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(f.n. P . R -258I TECHNICAL INFORMATION REPORT Heritage Renton Hill Plat S.E. 7th Court and Beacon Way S.E. Renton, Washington City of Renton File Nos. LUA00-149, AAD and LUA00-053, PP, ECF Prepared for: Heritage Arnold Associates, LLC 2100 - 124th Avenue N.E., Suite 112 Bellevue, Washington 98005 January 2002 Our Job No. 7797 Z / �2 S• ARC WASyi�c l' �O .QF26016�� ,e ASTER �� ASS/ONAiL. EXPIRES:2-05-; �&V4 A VS CIVIL ENGINEERING, LAND PLANNING,SURVEYING, ENVIRONMENTAL SERVICES 18215 72ND AVENUE SOUTH, KENT,WA 98032 . (425)251-6222 (425)251-8782 FAX www.barghausen.com TECHNICAL INFORMATION REPORT Heritage Renton Hill Plat S.E. 7th Court and Beacon Way S.E. Renton, Washington City of Renton File Nos. LUA00-149, AAD and LUA00-053, PP, ECF Prepared for: Heritage Arnold Associates, LLC 2100 - 124th Avenue N.E., Suite 112 Bellevue, Washington 98005 January 2002 Our Job No. 7797 rmy OF RENTON RECEIVED .t� 2002 ,s s OrAGR SERVICE CIVIL ENGINEERING, LAND PLANNING, SURVEYING, ENVIRONMENTAL SERVICES 18215 72ND AVENUE SOUTH, KENT,WA 98032 .. (425)25T-6222 (425)251-8782 FAX www.barghausen.com TABLE OF CONTENTS 1.0 PROJECT OVERVIEW 1.1 Technical Information Report (TIR)Worksheet 1.2 Vicinity Map 1.3 Assessor's Map 1.4 Aerial Topography 1.5 Aerial Photograph 1.6 Topographic Survey 1.7 Boundary Survey 2.0 CONDITIONS AND REQUIREMENTS SUMMARY 2.1 Preliminary Plat Maps 2.2 Hearing Examiner's Report dated January 25,2001 2.3 Mitigated Determination of Non-Significance dated October 19, 2000 2.4 Summary of Hearing Examiner's Conditions 2.5 Summary of SEPA Conditions and ERC Advisory Notes 3.0 OFF-SITE ANALYSIS 3.1 Downstream Analysis by Peterson Consulting Engineers dated April 10, 2000 4.0 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN 4.1 Existing Site Hydrology 4.2 Developed Site Hydrology • 4.3 Tract A Infiltration Pond Sizing 4.4 Tract A Wet Pond Sizing 4.5 Tract A Infiltration Trench Sizing 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN 5.1 100-Year Conveyance Analysis 6.0 SPECIAL REPORTS AND STUDIES 6.1 Results of Subsurface Infiltration Testing by Geotech Consultants dated November 17,2000 6.2 Results of Test Pits for Fill Exploration by Geotech Consultants dated November 9,2000 6.3 Geotechnical Engineering Study by Geotech Consultants dated September 14, 1999 6.4 Phase 1 Environmental Site Assessment by Geotech Consultants dated September 9, 1999 6.5 Abandoned Mine Assessment by Hart Crowser dated August 23, 1999 7.0 OTHER PERMITS 7.1 City of Renton Street Name and Address Approval 7.2 City of Renton Postmaster Approval 7.3 City of Renton Fire Hydrant Location Approval 7.4 Washington State Department of Natural Resources FPA Permit 7.5 Washington State Department of Ecology NPDES Permit Approval 7.6 City of Seattle Water Department Approval to Work Within Beacon Way S.E. 8.0 ESC ANALYSIS AND DESIGN 7797.006[RJA/jss/ca] 9.0 BOND QUANTITIES,FACILITY SUMMARIES,AND DECLARATION OF COVENANT • 10.0 OPERATIONS AND MAINTENANCE MANUAL t 7797.006[RJA/jss/ca] 1.0 PROJECT OVERVIEW • The Heritage Renton Hill plat is located in a portion of the Northwest quarter of the Northeast quarter P P q of Section 20, Township 23 North, Range 5 East, Willamette Meridian, City of Renton, King County, Washington. The project occupies approximately 10.35 acres and is situated east of Beacon Way S.E. and south of S.E. 7th Court, as shown on the Vicinity Map. To the north of the project is an existing single-family subdivision known as River Ridge. To the east of the project is an existing single-family subdivision known as Falcon Ridge. To the west of the project is the Seattle Water Department Cedar River Pipeline Easement and the City of Renton Philip Arnold Park. The project has received preliminary plat approval for 50 lots. The property is covered with young,second growth,mixed deciduous trees,except the northwest portion where filling has occurred in the past. The site is underlain with surface native topsoil overlying gravelly sand. There is an area in the northwest portion of the site where fill material was placed in the past. This fill is a mixture of soil, concrete rubble,construction debris, and household garbage. This garbage/fill will be screened on site and the soil will be retained on site while the garbage will be hauled away to an approved dump site. The entire site will be cleared and graded for individual lot pads. The proposed development for the site consists of a 50-lot single-family subdivision with roads and utilities serving each lot. The roadway sections used for this project are according to City of Renton standards, with a modification allowed to reduce the right-of-way width to 42 feet. Several private driveway tracts will be provided along with an emergency access tract. Tract A is a drainage facility containing a wet pond for water quality treatment and an infiltration pond for retention of stormwater on site. The wet pond is sized for Basic Water Quality treatment according • to the 1998 King County Surface Water Design Manual(KCSWDM). The infiltration pond is sized for the KCRTS 100-year event according to the KCSWDM. The design infiltration rate used for the pond sizing is 30 minutes per inch based upon safety factors required by the KCSWDM and field measured infiltration tests by Geotech Consultants. Please refer to Section 6.0 ofthis Technical Information Report (TIR) for the Geotech Consultants reports. Roof drain infiltration trenches will be provided for each lot and equipped with an emergency overflow connection to the storm drainage system. This is in accordance with Section 5.1 of the 1998 KCSWDM. Drainage runoff from the roadways, driveway tracts, individual lot driveways, and front yards will be collected and conveyed by a series of catch basins and drainage pipes that run to the Tract A drainage pond. Individual lot drainage stubouts will be provided for each lot for the emergency overflow from the roofdrain infiltration trenches. This will provide a distribution of infiltration of stormwater runoff across the site. The storm drainage infiltration pond has been sized to handle the entire site,assuming a worst case scenario that the roof drain infiltration trenches are not functioning. This is the conservative approach. Please refer to Section 2.0 of this TIR for a detailed narrative response to each of the plat conditions and SEPA conditions for this project. 7797.006[RJA/jss/ca] Iti King County Department of Development and Environmental Services TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND Part 2 PROJECT LOCATION AND DESCRIPTION PROJECT ENGINEER Project Owner Heritage Arnold Associates, LLC Project Name Address 2100 - 124th Avenue N.E., Suite 112 Heritage Renton Hill Plat Bellevue, Washington 98005 Location Phone Bill Sherman at(425) 602-3700 Township 23 North Project Engineer Robert J. Armstrong, P.E. Range 5 East Company Barghausen Consulting Engineers, Inc. Section 20 Address/Phone 18215 - 72nd Avenue South Kent, Washington 98032/ (425)251-6222 Part 3 TYPE OF PERMIT Part 4 OTHER REVIEWS AND PERMITS APPLICATION ■ Subdivision HPA ❑ DFW HPA ❑ Shoreline Management ❑ Short Subdivision ❑ COE 404 ■ Rockery Grading ❑ DOE Dam Safety ❑ Structural Vaults Commercial ❑ FEMA Floodplain ■ Other-Structural Wall ❑ Other ❑ COE Wetlands Part 5 SITE COMMUNITY AND DRAINAGE BASIN Community Renton Drainage Basin Cedar River Part 6 SITE CHARACTERISTICS ❑ River ❑ Floodplain ❑ Stream ❑ Wetlands ❑ Critical Stream Reach ❑ Seeps/Springs ❑ Depressions/Swales ❑ High Groundwater Table ❑ Lake ❑ Groundwater Recharge ❑ Steep Slopes ❑ Other • 7797.006[RJA/jss/ca] art 7 SOILS Soil Type Slopes Erosion Potential Erosive Velocities Gravelly Sand 5% Minimal Minimal ❑Additional Sheets Attached See Geotech Consultants Reports in Technical Information Report Section 6.0 Part 8 DEVELOPMENT LIMITATIONS REFERENCE LIMITATION/SITE CONSTRAINT ■ Ch. 4- Downstream Analvsis ❑Additional Sheets Attached: See TIR Section 3.0 Part 9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION ■ Sedimentation Facilities ■ Stabilize Exposed Surface 1 Stabilized Construction Entrance ■ Remove and Restore Temporary ESC Facilities Perimeter Runoff Control ■ Clean and Remove all Silt and Debris ❑ Clearing and Grading Restrictions ■ Ensure Operation of Permanent Facilities ■ Cover Practices ❑ Flag Limits of SAO and open space preservation areas ■ Construction Sequence ❑ Other ❑ Other Part 10 SURFACE WATER SYSTEM ❑ Grass Lined Channel ❑ Tank ■ Infiltration Method of Analysis ■ Pipe System ❑ Vault ❑ Depression 100-Year KCRTS ❑ Open Channel ❑ Energy Dissipater ❑ Flow Dispersal Compensation/Mitigation of ■ Dry Pond ❑ Wetland ❑ Waiver Eliminated Site Storage ■ Wet Pond ❑ Stream ❑ Regional Detention Brief Description of System Operation Catch basins and pipes for collection and conveyance. Wet Pond for water quality Infiltration pond for stormwater retention. Facility Related Site Limitations Reference Facility Limitation • 7797.006[RJA/jss/ca] art 11 STRUCTURAL ANALYSIS Part 12 EASEMENTS/TRACTS ❑ Cast in Place Vault ■ Drainage Easement ■ Retaining Wall ■ Access Easement ■ Rockery>4' High ❑ Native Growth Protection Easement ❑ Structural on Steep Slope ■ Tract ❑ Other ❑ Other Part 13 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet a t at chments. 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O ob o"f' • �� (z\ ., 0 I'� Ac '\ �6 tr �. �q 9 [naB-i�=�. :./ a>9.d;]n .. /DI..o Y d� _ • 9� Y .D1 �) I -- aMIF Ulm RE 53M '..�► ,y � RE. { .. r. AC 74 66 41k� • a 1" 010 - 1 ,+ Jksit a $ 1 • h ti ! i a t t ` r f 115 1 �y r' e �� • � � t a1 4 • • • • 1.7 BOUNDARY SURVEY N1/4 CDR.SEC. 20--23-5FFOOUND CASED CONC MON. RIVER RIDGE VOL. 163199-101 \ I /1' NE CORNER SECTION \ /I-) FOUND 1/2"REBAR&CAP FOUND 1/2-REBAR h CAP FOUND 1/2-REBAR RE CAP 2o-23-5 L TCA 9634 10356 0.1'N- OF S*XS"CONIC MON I Z,12 / TCA 9634/10356 0.1 s OF TCA .LINE 0356 O.iN.of PROP. LINE PROP.LINE PROP.LINE WITH LEAD k HIS BRASS PIN I 1 •� � NOT VISITED THIS SURVEY i7 3 q 5 6S. 7TH ST. \ i FENCE��� N 8956'37"'W \\�\ 2659.62' - - - ---— - 929.64' �-. .. 7329.BP of toy. 4Dot7r-—•—•--—•---- SEE ENCROACHMENT L7 \ DETAIL ENCROACHING AREA FROM \ LOT 3 OF RIVER RIDGE APPROX. AREA- 3293± S.F. PUBLIC ROADWAY AND UTILITY IC/i EASEMENT REC NO. 9108190681 IQ \\ �w Iz j� 19 100 0 100 200 300 �b CcNo `� FALCON RIDGE (CEDAR RIDGE) Scale 1" = 100' ,p �� VOL. 129151-57 tiF \ MERIDIAN: CURVE TABLE F'9 PLAT OF FALCON RIDGE (CEDAR RIDGE) `%/� VOL. 129, PG. 51-57 NUMBER DELTA RADIUS LENGTH a `\ C1 281271 12500 62.08 ` • ' cz 134 2500 58.68 MoSIGN T `4.04' REFERENCES: 1. PLAT OF FALCON RIDGE(CEDAR RIDGa VOL 129,PG.51-57 LINE TABLE \ 2. PLAT OF HI24-AND ADDRION,VOL.17,PG.32 NUMBER DIRECTION DISTANCE 1 3. PLAT OF EML LISNBEIII AODFWK VOL 6Z PG.40 Li N 0151'Ir E 33.13, 25.9r' L2 N 4419 4 W 34.10P 4. PUT OF RIVER RIDGE,VOL.183„PG.99-101 L3 N 8956 W 100. BOUNDARY \ L4 N 1 1 W 15.45 LINE �\ gyp' LN3 N 781 334 W 2286 ,�p9 NOTES: L7 N 4 W 23.E ENCROACHMENT DETAIL L8 N 5213'42"E 45.18' 1. EQUIPMENT h FIIELD PROCEDURES: A 5'ELECTRONIC TOTAL STATION WAS USED FOR THIS FELD TRAVERSE SURVEY.ACCURACY NESTS OR t9 N 162215 E 114.9ir IXCFIDS WAG 332-130-090. DR�\rr- 2. THE INFORMATION DEPICTED ON THIS MAP REPRESENTS THE RESULTS c�� B OF A SURVEY MADE ON THE DATE INDICATED AND CAN ONLY BE 0014- SDERED AS INDICATING THE GENERAL CONDITION EXISTING AT THAT TIME. LEGAL DESCRIPTION 3. THIS MAP DOES NOT PURPORT TO SHOW ALL EASEMENTS OF RECORD. THAT PORTM OF THE NORTHWEST QUARTER OF THE NORTHWEST QUARTER OF THE NORTHEAST QUARTER OF SECTION 20. TOWNSHIP 23 NORTH,RANGE 5 EAST.W.M.,N TONG COUNT.WASHNGTON.DESCFmm AS FOLLOWS. COMMENCING THE TRUE POINT OF BEGNwNr THORTHWEST CORNERENCE��EEAASSTP�T PXObX•v��4F- LEGEND ALONG 7TE NORTHERLY TITS OF SAID SUBOHNSUOII A DISTANCE OF 929.67 O.,T a • SET REBAR AND CAP'MIG 3243C UNLESS OTHERWISE NOTED. FEET TO THE NORTHEAST CORNER OF SAID SUBDMSION; THENCE SOUTH 4i«n z;Z 01'4S3r WEST ALONG THE EASTERLY LIMITS OF SAD SUBOIMSION A DISTANCE OF 818.33 FEET; THENCE SOUTH 71'0512"WEST A DISTANCE OF 109-48 FEET TO A PONT ON THE NORTHEASTERLY MARGIN OF THE CITY OF 32 20*15AWEST RIGHTTPrS CEDAR RI[VER PIPELINE NORTH OF WAY,. 7HENCE ALONG SAD NORTHEASTERLYMARON A DISTA NCE .20OF 1148 :�' S:JStC��4 •: FEET TO A POINT ON THE WESTERLY LIMITS OF SAID SUBEIVISDN; THENCE �0 NORTH O1'46'20'EAST ALONG SAID WESTERLY UMEIS A DISTANCE OF 33.14 FEET TO THE TRUE PONT OF BEGfNNNG. EXPIRES:9/9/ NW1/4, NE1/4, SEC. 20, T. 23 N., R. 5 E., W.M. KING COUNTY, WASHINGTON RECORDERS CERTS)r-ATE - SURVEYOR'S CERTIFICATE RECORD OF SURVEY Seluld S & .ICI.V,,(s�o. THIS MAP CORRECTLY REPRESENTS A SURVEY MADE BY ME OR for PROFESSIONAL LAND SURVEYORS FILED FOR RECORD INS DAY OF 20_AT UNDER MY DIRECTION IN CONFORMANCE MTH THE REQUIREMENTS P.O. BOX 289. WOODNVILLE. WA 98072 (425) 486-1252 OF THE SURVEY RECORDNC ACT AT THE REQUEST OF M.N BOOK OF SURVEYS AT PAGE_ �NMETT CORP. NAM ,999 B EN N ETT DEVELOPMENT DRAWN BY: DATE: JOB NO.: AT THE REDDEST of OF EDA 3-21-00 99172 • MANAGER SUPT. OF RECORDS EDWARD D.ANDERSON CHKD BY: SCALE: SHEET: rADRTUTCATE NO. 32434 9 LAKE BELLEVUE DR. STE 100A BELIEVUE. WA 98005 JR 1" = 100' 1 OF 1 N O • 2.0 CONDITIONS AND REQUIREMENTS SUMMARY Included within this section are the preliminary plat approval conditions and a narrative response describing how the conditions will be addressed prior to final plat recording. The basic and special requirements that govern this project have been listed below in a table that articulates how each ofthe core and special requirements have been addressed. These requirements come directly from the 1998 King County Surface Water Design Manual. DISCUSSION OF CORE REQUIREMENTS AND SPECIAL REQUIREMENTS OF THE 1998 KING COUNTY SURFACE WATER DESIGN MANUAL CORE REQUIREMENT HOW PROJECT HAS ADDRESSED REQUIREMENT: No. 1: Discharge at Natural The proposed infiltration pond will act as the natural discharge for the Location project,along with the individual lot roof drain infiltration systems. An emergency overflow connection to the catch basin in Beacon Avenue South will be provided. No.2: Off-Site Analysis A Level 1 Downstream Analysis was prepared by Peterson Consulting Engineers, dated April 10, 2000. This analysis has been included in Section 3 of this Technical Information Report. No.3: Flow Control On-site infiltration will be provided to retain runoff. • No.4: Conveyance System The conveyance analysis that was performed for the proposed storm drainage system is contained in Section 5.0 of this Technical Information Report and has been prepared according to the 1998 King County Surface Water Design Manual. No.5: Erosion and Sediment Temporary erosion control measures for this project include temporary Control ditching,stabilized construction entrance,perimeter runoffcontrol,cover practices,temporary sedimentation pond,and construction sequence. No.6: Maintenance and The drainage facility for this project will be maintained by City of Operations Renton,and has been designed in accordance with the 1998 King County Surface Water Design Manual requirements. No.7: Bonds and Liability Bonding will be completed as required by City of Renton. No.8: Water Quality The project has provided a wet pond in accordance with the Basic Water Quality menu of the 1998 King County Surface Water Design Manual. SPECIAL REQUIREMENT HOW PROJECT HAS ADDRESSED REQUIREMENT: No. 1: Other Adopted Area This special requirement does not apply to this project. Specific Requirements • 7797.006[RJA/jss/ca] • No. 2: Floodplain/Floodway The 100-year floodplain boundary is not within the limits of this project, Delineation nor is it within the limits of any of the adjacent properties to this project. No.3: Flood Protection This project does not contain or abut a Class I or Class II Stream that has Facilities an existing protection facility;therefore,this requirement does not apply. No.4: Source Controls This project is not a commercial,industrial,or multi-family development, nor a redevelopment project proposing improvements to an existing commercial, industrial, or multi-family site; therefore,this requirement does not apply. No.5: Oil Control This site is not classified as a high use site given the criteria found in the 1998 King County Surface Water Design Manual;therefore,no special oil control treatment is necessary. • • 7797.006[RJA/jss/ca] • N N • • 2.1 PRELIMINARY PLAT MAPS SEC. 20, T WP. 23 N., RGE. 5 E., W.M. ETE RSO N CO NSULTING HERITA " E E N G I N EE R S AIRPORT 4030 Lake Washington WAY S � �,� Blvd. N.E., Suite 200 RENTON HILL �� ��o Kirkland, WA 98033 S 2nd ST t2 Tel(425)827-5874 S Jrd ST Fax (425)822-7216 S 4tn ST m SITE \� a 2 CT. a a 2 \� I \y \� WAY S. 77N ST. C _1 S89 S6 3 �_ 829.34'\ ~ ARNCiD s 3 + Q Iis - - i S TRACT 14414J 42 41 40 39 38 37 36 PARK 34 SW 16th J O fi � ST 4 4e 49'SD if TDR �GV I I I I I y 3 56 Ss ss 83 52 30 �� J 200' 0 200• -I f--t-I-----I i I ' _.nt �. F y -_ 29 m � VICINITY MAP:29 Q W SCALE 1'=200' r > , \ B a3 \ NOT TO SCALE W 4/12/00 1 I 8 9 10 11 12 .,.? 27 , \ , 4 GENERAL NOTES: 17 1615 14 13 25 4 Y4 �_- OWNER: RENTON SCHOOL DISTRICT W c _fi NUMBER I DELTA RADIUS LENGTH LA 7RALY L- C- 3OO SW 7th is 23 23 RENTON, WASHINGTON 98055 C1 13478'40" 25.00' 58.68' F• C2 2877'12" 125.00' 62.08' 1 ' DEVELOPER' BENNETT DEVELOPMENT l \\ 19 21 I---� 9 LAKE BELLEVUE SU17E 100 A L/$TRACT\ p / C ' (425) 09-6508NGTON 98005 v I •l! \1 CONTACT, RYAN nKE o� 9� CONTACT,ENGINEER•. PE7ERSON CONSULTING ENGINEERS'N-- � J�-\ S40O LAKE UITE 200 WASHDNGTON BL VD N.E. KIRKLAND, WASHINGTON 98033 // \ (425)827-5874 CONTACT .*WNIFER STEM P.F- , KEY MAP SURVEYOR., MEAD GILMAN s ASSOCIATESo SCALE 1'=200' P.O. BOX 289 a WOODINWLL& WASHINGTON 98072 (425)486-1252 CONTACT: EDWARD ANDERSM,, P.L.S. o BENCHMARKS/DA TUM: TOTAL ARF4:(-A/-) f0.35 ACRES(GROSS) o BENCHMARKS CITY OF RfVON/415- N1/4 COR. SEG Z(�23-5 m CASED 4�4'CONG MON WITH 1 1/2"BRASS DISC 3 -", 80.3 E OF TOTAL AREA FLO.W. 204 ACRES o�a aaaa aaaa� THE INTX OF S 77H ST. &XNES AM S. NET AREA 6.31 ACRES ELEVATION- J41.34' TOTAL LOTS 57 RESIDENTIAL L07S a STETG CITY OF REN70V 1418 PROJECT MANAGE& CASED CONC MON WITH 1/4'BRASS PPJ, 11.*S OF THE INTX OF MAX ALLOWABLE DENSfM- 8.00 OU/ACRE S 77H ST &RENTON AM S DESIGNED d STE1G ELEVATION- 305.80' PROPOSED DENSIM 6.86 DU/ACRE CADD B. DENNEY DATUM• ALiW 88(CITY OF RENTON) ZONING R-8, URBAN R£SIDEN77AL CfECKER J. STM DATE 4/10/00 PROPOSED USE: SINGLE-FAMfL Y, DETACHED FILE NAME PP1H£R25 LEGAL DESCRIPTION EXIS77NG USE-- SINGLE-FAMXY, DETACHED THAT POR77ON OF THE NORTHEAST QUARTER OF THE NORTHWEST OVARTER OF THE NORTHEAST BOUNDARY• FIELD SURVEYED BY MEAD GILMAN.4 ASSOCIATES QUARTER 8 SECRON 20, TOWNSHIP 23 NORTH, RANGE 5 EAST, W.M, IN KING COUNTY, WASHINGTON, - DESCRIBED AS FOLLOWS TOPOGRAPHY. FIELD SURVEYED BY MEAD GILMAN R ASSOCTA TES OF COMMENCING )HENCE SOUTH 895��FAST ALON OF'SAID�NNORTHMY LIMITS OFF SAID SUBMWSION9M SW PONT BEING ZHE� ME T UTILITIES/PURVEYORS: $�•t�.84 A3g 1P A DISTANCE OF 929.67 FEET 70 THE NORTHEAST CORNER OF SAID SUBO(V15ION,• 7HE1VCE SOUTH 0143.38'WEST ALONG THE EASTERLY LIMITS CK SAID SUBMV790N A DISTANCE OF 8/8.33 FEET ry m THENCE SOUTH 71175.12'WEST A DISTANCE OF 109.48 FEET TO A POINT ON THE NORTHEASTERLY SEWER/WAIM. CITY OF RENTON MARGIN OF 7HE CITY OF SF-4 ME'S CEDAR RIVER PIPEUN£RIGHT OF WAY; THENCE NORTH 44' 20'15'WEST ALONG SAID NORTHEASTERLY MARGIN A DISTANCE OF 114&20 FEET TO A POINT ON THE STORM DRAINAGE.• CITY OF RENIDN WESTERLY LIM17S CP SAID SUBDMSIOAh THENCE NORM 07 4620'EAST ALONG SAID WESTERLY DJMIIS A A DISTANCE OF 33.14 FEET TO THE TRUE POINT OF BEGINNINGI GAS/POWER: PUGET SOUND R ENERGY LOT AREA'S (LISTED IN SQUARE FEET) TELEPHONE' US WEST 1. 4990 1.1 %482 25. 4,750 37. 5,527 49. 4,750 CAS- AT&T EXPIRES 9/9/00 2 4353 1'k 4,965 2& 4,750 3& a500 sa 4,749 FIRE DISTRICT. CITY OF RENTON STAMP NOT VALID .I 4,875 1a 4,750 27. 4,750 39. 4500 51. 5,825 OU A 4,625 1G 4,750 2& 4,750 4Q 5�500 52 5,863 SCHOOL DISTRICT. RENTON SCHOOL DISTRICT f403 UNLESS SIGNED AND DATED A 4,504 17. 6,090 29. 4,750 41. 5,500 51 4,750 6. %557 1& 7,564 3R 4,750 4Z 5,500 54, 4,750 7 4799 19. 7,319 31. C754 4J 4500 55. 4,750 JOB NUMBER HERM-om 6L 4443 2a $318 3Z 4,946 44. 5,500 56. 4,731 9. 4,750 21. 4000 3.I 6,121 45 4,750 57. 6,660 1Q 4,750 22 AOOO 34. A549 48. 4,750 SHEET NUMBER g 11. 4,750 21 4,851 3S 6,905 47. 4,750 3 12 --&625 24. 4,750 36. 7,406 4& 4,750 SEC. 20, TWP. 23 N., RGE. 5 E., W.M. ETERSON CONSULTING " EX. SS H H114 CO2 SEC.20-23-5 \\ .\ PoM 336. FOUND CASED CONC MON- _ y CTR. CN 328.2(NW,SW) I I EX. CB rrP£n 4030 Lake Washington TYPE ll TOP 344.4 / / I COULD NOT OPEN I 'TT Blvd_ME, Suite 200 \ p O\ 1E 334.7(SW) I EX. CB TYPE I / I I I i Kirkland, WA 98033 - 1R'1E 331.8(S£) TOP 343.5 -X- SSMH \\ 'IE 33r.6(NW) 12"1£34a4(5) I I 1 I Tel(425)827-5874 -TR. CHNL. 326.9`(,�1E;SW1 \\ \� I GS 12'1E 34a (< /= i I I I Fax(425)822-7216 _ PTU GA JJ= (� PM_ o"'I �� • I I i I a -FVC- — -- 1 — { I X. 1-r / _ x 15'VF A77W/ o R1Ay 46.6 — / _ —-- —— / i — /I l C7(t CHI' 34a r (NE--SW) % �/ s — � _M*7!1 —'— 37"E �19. � 6'4VOO FENCE 50' ,/ _ 50, ' 5Cr , 1 . N t / / rh 1 / / / / / I r F AREA O 8-f CB �-/ / 1 I // I CW 343 ( � ',/ / ,/ / ,� / (T�) I \\\ \ I I I — — ^J !� EX. IE.140.9(N)\ , I I/ TOP 338.9 S�O7 wAATER__---/ / ��`�� \ \\ �,�' , 8'JE 336.4(SE) V\ \\ � � �'. ( / �^v, / // �``a50d\x/._r SOa'��\ I 5,500 sf. \ I / /27982 of ' --- ------------ Sol 4 e4 rL f afi fit° v V V _ I t. 1\ \ \\ '�` - .1� ��._�E�.�s.*3c '*Fr`�'` `�.f'�``r .+�c.�:'�_a.,:.s• � - -h `��.�s Ni� 16' 'WI / , I( ` ----------- 7Ro I \\ \\ ' j L a. % r A • ; I { \\ I \ \ `\� \ .\ I TRACT --\ \ - PARK 11 ,4 NUMBER DELTA, RADIUS LENGTH \ 1 l �� I �4o2�r. ` / �\ /� j tY r 3Co4z�f 45Cf 1342840 25.00' 56.68 \ / \ : \ �I ! / \ - , . Aso sr. C2 2827'12" 125.00' 62-06' l^ N 50 4875 ski \\� _ - _--�Scf� .t S7F16 DFSIQ4ED .t s7crc // . I i 1\ alEcxED .c s7e7c /\\ 4,625 af. ,( 4/10/00 / \\ -� ,roc,:.•. ,::Y DATE F4,ENAM PP2HVM \ SCALE., I"v 40 <{ { .C� \ \ \ \\\ \ I I I . ..• ..:1'... . .:1..,, t^�\ ,\ \�\ \ \\\` \ \\,504 at Me I ErwVREs: s/s/oo STAMP NOT YALN •; \\ 9��P \ \ UNUM 1=0 AND DATED I { . ACT ; .MN HERM-om af Y 9ffiET NUMB 2 cr 4 SEE SHEET 2 Ll li,�y, SA (CA I Irq / I 1. / I \\ ,�I\` .� � ��x �y i �Sn � I } • ]� .; `' 1 I`I I \ 1 ./ / (mOR Li nnT-Cfi ---i\ I w \ gg A Ii �k$e1\ I I y ,1. 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WASHINGTON ^•—•�••••�•••. rtn,w1L 1/3/Op PLOP SCJJL III" PAPER MACE YO SEA Jos Na: hm-.Qm @ R.aFm • PF • SS—TTTT HERITAGE RENTON HILL 4/2/00 •�© CITY OF &DENNfl• "� RENTON NEIGHBORHOOD DETAIL MAP 1 PS?GTYCLWMENTS auo e/af/oo JAS aim �_°�1_001_ DATUM N0. J•sraa : Planning/Building/Public Works Dept. REVISION gy pgTE AppR N..wm .u.rmawwr Gregg Zimmerman P.E., Administrator J.SIEIG t--r--� \ -1-i- \ \ l-r `ITN 7 �-FT-T-TTTT777-1 Iif I I lal I I I I I I I I I I �"4-4i4 }--.}. -I z I I I I I I I I I I L y ��____ LL_L_L LLLLLll-L I J/ MAIN AVE S • 40, I ---I 8R i05 ------------------------ / II I I MILL AVE S 114 ; .rTT- 7-7-1 ( i-1-1-1-T T_f_T_f�1 L lm1 I I I 1 1 1 1 I 1 ti i —Im f rT--F-r '777777 I CEDAg AVE9--- ----I l I-1 —J LLLLL111��J LLLL11111JJ~ CEDAR AVE a cl I I I I I I I I I I I I IL11 I I I i l l l l l l l I I j �'� j 4 I I I I I I I I I I I► I I ==-::, I I I I I i l l l l l I I I I I I I I� V� {- / I I I I I I I I: �= I I I I I I I I I I J_ o��� f / / I I I I I I I I I I I •F•" I I I I I I I I I I I �� 00 L�_ <• r:J__1_LJ-1_ J i_ _ f ICIr�I TI 7F--•a II I I RENTON I AV E 8 _TT T_FI I I I I' I I IN``:•c• R(E-N7TON_A L- -r--i--ri-rt-- / Imo(--1 LJ 1 J.1 L� �1� � I —T�_� I,AI; J LI I I- I-f I'�,•t=. 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S. — — — — ------------- ------------ u_ A Ati io ti,, cl T ,/'••yip' /� � /, r,\ b\\� //;"s �/, �"�, I \\\ 11 n� III���A it I It I d � p I \z I 1 / \I lo I / ♦ / I 1IS r� Nra\4 1\ \ , �\ \w �/ Y/ <�'.1 \J �/ \ /l 1 \b I I / f 7. / / r/tea //►v � ��-' / � -\I / ..� 1 � / / / \ � I r - � /r' �-- -�. / // \ _ r 11• VI 4 Of I 1111 �l 1\hi (.r / / ' � // /� ` I I I I I � \\ \ I �\ ) i ! �''��� \\ \.. owl �ii r'�•'!�' I l I I I l \ \ y� SE 8th DR °l / January 25 ,2001 OFFICE OF THE HEARING EXAMINER • CITY OF RENTON REPORT AND DECISION APPELLANT: Ruth Larson Appeal of ERC's Determination re Heritage Renton Hill File No.: LUA00-149,AAD LOCATION: Renton Hill, southeast of intersection of Beacon Way S with SE 7th Ct,Jones Ave S,and South 7th Street SUMMARY OF REQUEST: Subdivide an approximately 450,846 square feet(10.35 acre) property into 57 lots suitable for detached, single family homes SUMMARY OF APPEAL: Appeal of SEPA determination PUBLIC HEARING: After reviewing the Appellant's written request for a hearing and examining the available information on file,the Examiner conducted a public hearing on the subject as follows: • MINLrTES The following minutes are a summary of the November 14,2000 appeal hearing. The official record is recorded on tape. The hearing opened on Tuesday,November 14,2000,at 9:05 a.m. in the Council Chambers on the seventh floor of the Renton City Hall. Parties wishing to testify were affirmed by the Examiner. The following exhibits were entered into the record: Exhibit No. 1: Yellow file containing the appeal, Exhibit No.2: Yellow land use file,LUA00- the Examiners letter setting the hearing date,a map, 053,PP,ECF,containing the original application,proof photographs,and other documentation pertinent to the of posting,proof of publication and other appeal documentation pertinent to this request. Exhibit No.3: Vicinity Map Exhibit No.4: Photo of Renton Ave S Exhibit No.5: Photo of telephone pole 6"from curb Exhibit No. 6: Photo of telephone pole 12-112" from curb Exhibit No.7: Photo of curb and gutters Exhibit No.8: Photo of garbage truck on street Exhibit No.9: Photo of garbage truck on street Exhibit No. 10: Photo of dip in street Exhibit No. 11: Photo of fire hydrant Exhibit No. 12: Ruth Larson's testimony Exhibit No. 13: Aerial photo from City Archives Exhibit No. 14: Plat map Exhibit No. 15: Phase I Environmental Site Exhibit No. 16: Jennifer Steig letter to Bennett Assessment Development i Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25,2001 • Page 2 Parties present: Appellant: Ruth Larson Renton Hill Community Association 714 High Ave S Renton, WA 98055 Representing applicant: _ Ann M. Gygi,Attorney Hillis Clark Martin&Peterson 500 Galland Building 1221 Second Avenue Seattle, WA 98101-2925 Applicant: Ryan Fike Bennett Development 9 Lake Bellevue Drive, Suite 100-A Bellevue, WA 98005 Representing City of Renton: Zanetta Fontes, City Attorney Elizabeth Higgins,Development Services -- 1055 S Grady Way Renton, WA 98055 Ms.Larson, appellant herein, reviewed each item contained in her written appeal of the ERC's Staff Report dated October 17,2000, and explained the reasons for her objections in each case. Particular emphasis was given to Renton Avenue South. Ms.Larson used photos to show the close proximity of telephone poles to the curbs,the narrowness of the street, the dips in the street and the tendency of garbage trucks to drive toward the center of the-street. She explained her concerns regarding safety issues when large trucks are using the street considering the narrowness of the street,the steep grade,and the limited sight distances. Becky Lamke,415 Cedar Ave S,Renton, WA 98055 expressed concern that the number of trips per day per single family household has been underestimated,based on informal surveys of her neighbors. Ms.Lamke questioned exactly what the landscaping would consist of in the 15-foot buffer along the north property boundary. She concluded by stating that the construction vehicles should be required to come onto the site off of Puget Drive. It is not considered safe for busses to come up the hill,so it should not be safe for large trucks to do so. Elizabeth Higgins Senior Planner, Development Services, 1055 S Grady Way, Renton, WA 98055 gave an overview of the nature of the project, its current status, and its progress through the ERC. Regarding the reason for the setbacks on Lot#35,Ms. Higgins stated the geotechnical engineer's report commented that the slopes at the rear of this lot are excessive. They recommended that the setback at the rear of Lot#35 be increased from • Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 0age 3 20 to 25 feet in order to further to protect the slope. Using a photograph from the City Archives, she clarified why an exemption to the requirement in the Critical Areas Ordinance that slopes above a certain grade be protected was granted to the project. Ms. Higgins also addressed the issues of groundwater,responsibility for landscaping,regulation of fences,and parks constructed on the property. Ms. Higgins discussed the issue of Metro service on Renton Hill. She also explained the State of Washington Growth Management Act requirements and how the City is required to plan for housing. The City Council has committed to provide as much single family housing as possible and not meet their target with apartments. Regarding the requirement that a note be placed on the face of the plat about former mining activities,Ms. Higgins stated this is the City's- way of insuring that a property owner is made aware of a potentially hazardous situation. Mining activity took place throughout the city, and there are very rudimentary maps of where these mine shafts might be. The note on the plat alerts the potential home owner to seek the consultation of a structural engineer and choose the construction method most appropriate for the site. The appeal hearing was adjourned at 12:30 pm.,to be continued on Thursday,November 16 at 9:00 a.m. ******************************** The continued appeal hearing opened on Thursday,November 16 at 9:02 a.m. in the Council Chambers on the seventh floor of the Renton City Hall. Kayren-Kittrick,Development Services, 1055 S Grady Way,Renton, WA 98055 explained her role regarding Land Use Applications and how these applications are reviewed by her office. Ms.Kittrick stated that the sclude reet Maintenance Plan requires that all arterials be evaluated annually and all other streets,which would Renton Avenue S, be evaluated every two years. Ms. Kittrick explained traffic mitigation fees and how they are reviewed and collected,resources available for street repair,and hauling times as allowed by code. Ms. Kittrick reviewed intersection distances,how they are measured, and under what circumstances intersections should be 110 feet apart vs. 150 feet apart. She also discussed the transportation study provided by the applicant, including levels of service at S A Ct and access to Renton Hill overall. Regarding the foundation of Renton Avenue S.,Ms. Kittrick stated that recent borings show four inches of asphalt over crushed rock. On cross examination,Ms.Kittrick responded to questions raised by Ms.Larson in her appeal letter. Ann M.Gygi, attorney representing applicant, Hillis Clark Martin&Peterson, 1221 Second Ave,Seattle,WA 98101-2925 opened by reiterating that in a SEPA appeal it is appellant's burden to establish that the SEPA determination is clearly erroneous. This is a plat application that is based on an adopted comprehensive plan and zoning that slated this property for development at an urban scale. This parcel is among those that the City of Renton legislated to accommodate a certain amount of urban growth under the Growth Management Act. The general impacts associated with the conversion are impacts of the legislative decision. The specific and unique impacts of the plat proposal are what should be the subject of the SEPA consideration at this stage. Mark McGinnis,Geotech Consultants, 13256 NE 20th St.#16,Bellevue, WA 98005 reviewed his education, training and experience as a geotechnical engineer'. He summarized what is contained in the Phase I Environmental Site Assessment prepared by his firm regarding coal mines under the site, including risk of excessive settlement, localized subsidence, and mine gas emissions.Mr. McGinnis discussed the mitigation measures recommended in the Geotechnical Report to address the two worked coal mine seams under the 6perty. He stated that it is his professional opinion that the recommended measures will adequately mitigate Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 • Page 4 any potential risks associated with the two worked coal seams. Mr. McGinnis described the steep slope associated with Lot#35 in the northeast corner of the site. His firm investigated the slope, looked for slope problems, and did a test pit for exploration in the area to assess soil conditions near the top of the slope. Based on these observations, a 25 foot building setback from the crest of the slope is recommended. In addition to the 25 foot setback, it is recommended that there be no clearing and grading within 10 feet of the top of slope. Larry Hobbs, Transportation Planning and Engineering, Inc.,2223 112th Ave NE, Suite 101, Bellevue, WA 98004 reviewed his background, education and training as a traffic engineer. Mr.Hobbs stated that safety issues were considered as part of the traffic study that was prepared for the project. The city provided the last three years worth of accident data in the area, and it was found that there were no accidents recorded on Renton Hill itself for this period of time. In checking the data for the last five years, it was found that there were three traffic accidents throughout all of Renton Hill. Two of these accidents involved one vehicle backing into another, and the third was a vehicle striking a parked vehicle. There were no injuries or fatalities in any of the reported accidents. The record of reported traffic incidents is one of the main indicators of safety on a street system. Mr.Hobbs stated that it is his opinion that there will not be any increase in traffic accidents in the Renton Hill area as a result of the proposed development. Residents of the area would most likely be aware of anything that may be deficient and would drive accordingly to compensate for that. New residents moving into the area would rapidly gain familiarity with the street system. Jennifer Stem, Peterson Consulting Engineers,4030 Lake Washington Blvd NE, Suite 200,Kirkland, WA 98033 gave a summary of her training,education and experience as a civil engineer. Ms.Steig described the •conceptual grading plan her firm prepared for the site. Once grades are set,computer programs to come up with cut and fill volume. Based on the conceptual grading plan, there would be approximately 55,000 cubic yards of cut material and 19,000 cubic yards of fill:.The applicant requested that we develop a plan with a closer balance so that all the cut and fill would be used on the site--there would not be any material hauled off the site as a result of grading. The conceptual plan was sent to a company used industry wide that has a computer program which can look at the site as it is graded in the conceptual plan and raise or lower the site in small increments to determine when a balance is reached. This information is used to develop a final grading plan for construction. In doing this,it was found that if the site is raised one foot from the conceptual grading plan, there would be a balance of the cut and fill material on the site. Based on further geotechnical studies, if the unsuitable fill were screened on site,the amount of fill that would need to be hauled offsite could be reduced by approximately half. Ms.Steig discussed the number of truck trips that would be required to haul fill off the property based on the number of cubic yards of fill remaining. She explained under what conditions material must be worked so that it will be suitable for use in construction. In closing,Ms. Larson discussed the issues of preservation of vegetation and wildlife,compatibility of the new homes with the neighborhood, and the two crested vertical curves on Renton Ave S that do not meet city, county or state requirements for vertical curve design. Ms.Fontes, in closing,addressed issues raised by the appellant in the course of the hearing and discussed what the evidence has shown and what the process has been in each instance. Ms.Fontes reiterated that despite all the questions raised by the appellant, she has not shown evidence of significant adverse environmental impacts in any of these instances. Therefore,the decision made by the ERC must stand. Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25,2001 •Page 5 Ms. Larson responded that every question she asked was stated in the ERC's report. She responded to the questions because she felt there was clarification needed. Some of the issues have been clarified, others have not. In closing, Ms. Gygi stated that the applicant concurs with the City's closing arguments. She reviewed some of the issues raised by the appellant. Ms. Gygi summarized by stating that any project will alter the surrounding area. It is unrealistic to expect that there would be no effect from development. The law does not require that all adverse impacts be eliminated. If it did,no change in land use would ever be possible. Ms. Gygi reiterated that the burden is upon the appellant to prove adverse environmental impacts,which has not been done in this case. The Examiner called for further testimony regarding this appeal. There was no one else wishing to speak. The appeal hearing closed at 11:30 a.m. SEPA APPEAL FINDINGS,CONCLUSION&DECISION FINDINGS: I. The appellant,The Renton Hill Community Association, represented by Ruth Larson, filed an appeal of a Determination of Non-Significance-Mitigated(DNS-M) issued for a proposed Preliminary Plat that would divide approximately 10.35 acres of R-8 (Residential: 8 units per acre)zoned property into 57 • lots. The appeal was filed in a timely manner. 2. In processing the preliminary plat application the City subjected the application to is'ordinary SEPA review process. The City, in the course of and as a result of its SEPA review,issued a Determination of Non-Significance-Mitigated for the project. The Determination of Non-Significance-Mitigated (DNS-M)was conditioned by the City. 3. The subject site is located near the intersection of Beacon Way SE, S 7th Court and S 7th Street. The property is located immediately across from Philip Arnold Park. 4. The subject site a triangular parcel approximately 1.114 feet by 818 feet by 829 feet. 5. The subject site is approximately 10.35 acres or 450,846 square feet in area. 6. The subject site has rolling and descending terrain with some steeper slopes that were determined to be manmade as part of past mining or quarrying activity. An exemption from steep slope regulations was issued administratively since the steeper slopes are not natural. 7. The ERC imposed five conditions related to erosion control,three conditions imposing mitigation fees for fire,parks and roads, three conditions related to geotechnical issues for building construction/foundation work, subsidence notice due to potential coal mines and setbacks from steep slopes,one condition dealing with the potential discovery of hazardous materials, one dealing with traffic control for construction vehicles and finally, a condition for access across the Seattle Pipeline for emergency, secondary access. Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 • Page 6 8. During the course of the public hearing staff noted that the gross vehicle weight of 26,000 was not intended to vary from that posted on the road signs and should have matched that posted along the road. 9. The appellants objected to the determination. The appellants objected to or raised concerns about: a. Modification of street standards to allow narrower roads in the plat. b. Protection for abutting Falcon Ridge and River Ridge properties. C. Weight limit on Renton Avenue differing from posted standard(that was an error not intended to vary from posted limits). d. Width and emergency access relating to the Pipeline road. e. The steepness and width of Renton Avenue South. f. Exception to Critical Areas Ordinance that permitted grading on previously disturbed slopes. g. The amount of grading and number of heavy truck trips were not fully evaluated for impacts on the community. (the applicant altered the plans to balance the cut and fill and • substantially reduce material movements) h. Impacts on River Ridge. i. Air quality impacts of vegetation removal. j. The alteration of the base elevation and its impacts on water. k. The removal of 92%of the trees and retention of 32 trees, if possible. I. The maintenance of installed landscaping strips and islands. m. Impacts on the deer population that frequents the subject site. n. The manner in which the rezone was adopted. o. The character of the homes. p. The consistency of fencing. q. The impacts of new light on the community. r. The impact of internal pocket parks. S. The impact on the Renton Hill community by this plat. Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 40,age 7 t. Traffic impacts of new residents and construction vehicles on the existing road surfaces and the community. U. The use of mitigation funding. V. The development does not follow the policies of the City of Renton. 10. The subject site is located near the northeast corner of Renton Hill just where it begins its drop down to Maple Valley and the Cedar River. 11. The majority of property in the vicinity of the subject site is zoned R-8 (Residential; 8 dwelling units per acre). It has been developed with single family homes. The slopes north of and below the subject site are Resource Conservation. 12. Immediately north of the subject site is the River Ridge development that contains 11 lots. The proposed development would share an access roadway that now serves only River Ridge. East of the subject site is Falcon Ridge,and it contains 80 lots. Falcon Ridge is accessed from the east by a private roadway. 13. The subject site is covered by what is probably second or third growth trees and shrubs. As noted, the • site has been disturbed by some form of extraction or quarrying in the past. 14. The applicant did an historical survey of the subject site using aerial photographs as well reviewing the permit history of the site. There also were reviews of the mining data for the subject site and vicinity. There were also borings to determine the nature of the soils and to expose potential dumping of hazardous or other materials. The US Geological Survey maps for the area show a mine symbol, although it does not specify the type of mine but it appears it was used as a gravel quarry. 15. An evaluation was made of potential mine hazards. Both the more shallow and deeper mines are located 200 feet to 600 feet deep. It is anticipated that most linear shafts would have subsided over time. Any collapse events in "horizontal"mines would be distributed over those 200 to 600 feet, causing little surface subsidence. The greater potential for dangerous collapses are old airshafts or vertical access shafts. Some of these were filled with jumbled lumber or other debris till it"caught" on. the sides of the shaft and then filled. The"caught"materials can decay over time and lead to collapses. In most cases these latter actions cannot be predicted. The geotechnical information and studies have instructions on dealing with these if they are discovered during construction. In addition, there are governmental agencies that deal with such openings,although obviously,an opening occurring can still take parties by surprise. The geotechnical report also has construction methods to make sure homes constructed in this development follow certain prescribed foundation techniques. 16. The applicant and City emphasized stability in dealing with lots near the edge of slope areas. The only lot affected by steeper slopes is Lot 35 in the northeast corner of the subject site. Lot 35 will have a 25 foot setback for building and a 10 foot setback buffer that will remain undisturbed. i Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 • Page 8 - 17. The Geotechnical information shows that areas that have 15%to 30% slopes are limited and most of the terrain is moderate and the underlying soils are suitable for construction. The ERC imposed conditions to deal with erosion. The professional analysis is that the measures suggested in the geotechnical report and the measures imposed by the ERC should prevent any problems. 18. There are approximately 250 to 300 acres of open space along the Cedar River and the slopes above the river in City ownership or open space. Although a large amount of this property is very steep slopes, there are a developed trail and park located along the river, and there are other level or more gentle - areas. To accommodate roads and building pads, most of the vegetation will be removed from the subject site. It would appear that similar clearing probably has occurred for most development on the hill in the past with ornamentals replacing native trees. 19. There will be a loss of over 300 trees of six inches or greater in diameter. This loss of trees and habitat is an unfortunate but foreseeable result of development. Trees and vegetation may be maintained where possible. Open space tracts and ornamental landscaping generally occur as plats are developed and mature. 20. The project was reviewed for compliance with the Critical Areas Ordinance and the land clearing regulations. The exception approved for working on the man-made or altered slopes is not unusual and is a remedy available by code. Natural slopes will not be altered or would require special approvals. �1. The original plans called for a substantial grade and fill effort. This would have entailed a large number of dump trucks moving the materials to and from the subject site. The applicant further refined their grading plans and found that generally raising the elevation of the subject site by approximately one(1)foot would significantly reduce the needed trips. This would mean utilizing local materials on site in what is termed a "balanced cut and fill." There would still be export of unsuitable materials or debris that has been dumped on the subject site. It is not anticipated that raising the site by approximately one foot would create any problems with erosion or stability. The number of truck trips would probably be reduced to approximately 750 trips. The original estimate would have generated approximately 3,700 trips. The trucks would meet load limit requirements of the City. While this is not xsmall number of trips, it is also not unusual where development is occurring, including in residential areas and the City urges that this is generally not a SEPA impact. 22. The existing public roads serving the subject site do not meet current standards. Similar undersized or steep roads serve other older or hilly areas of the City including roads serving areas west of Rainier. At the same time,these older roads serve their neighborhoods or communities. Renton Avenue seems to serve the existing population, and as new residents have moved to Renton Hill they have adjusted to the constraints and limitations. This does not discount the experiences of current residents and that fact that extra care seems necessary to negotiate the roadways and deal with events like snow and ice. The fact is,transportation impact analysis including LOS information and sight distance information shows that the existing road system can handle the additional traffic including the additional approximately 50 to 60 vehicle trips that would be generated during the peak hours. It appears that there may be an approximately 0.2 second delay in wait time at traffic lights. • Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos._ LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 •Page 9 23. The proposed intersection at SE 7th Court and the subject proposal's entry road will meet City standards for sight distance and angles. Anytime a new intersection is created residents have to accommodate the changes in traffic flow. 24. Renton Avenue South is approximately 26 feet wide and has an approximately 23 foot 2 inch driving surface. There is a 5 inch drop to the gutter. Both telephone poles and hydrants are located close to the right-of-way and driving surface. There are some dips in the road and the crest apparently creates difficult sight problems with traffic driving up and down the hill according the residents. The technical analysis would appear to show that at normal driving sitting position,the view is not significantly impaired. 25. A study of accident history showed no reported accidents during the last three years and three(3) accidents throughout Renton Hill during the last five years. They appeared to be minor accidents resulting in limited property damage but no personal injuries. Anecdotal evidence suggests that there have been a number of"near-miss"and minor accidents but that residents may not have reported some accidents. The assumption then would have to be that they were not major accidents if they remained unreported. 26. The evidence does suggest that curbs, gutters and sidewalks improve safety but there are areas along what would be the commute route where this is not possible. Limiting speed and driver caution serve to control conflicts. SEPA does not ask an applicant to rectify existing problems,whether traffic or . storm water problems, but requires that impacts be appropriately disclosed. 27. The appellant challenged the traffic generation numbers used by the applicant. Those numbers estimate that each single family home generates approximately 9.55 trips. The 57 homes would generate 544.35 trips per day. The estimates also predict that approximately ten percent(10%)of the total trips would occur during each of the peak commuting times or approximately 55 trips. No basis for the challenge was provided. 28. The development, if approved in full,would add 57 homes to an existing inventory of approximately 200 homes,or an approximately 25% increase: There has been some infilling in the last few years,also adding to the inventory. At the same time, some homes were lost to the last expansion and straightening of I-405. The traffic report and City analysis demonstrate that while the roads are not standard,they have sufficient capacity to handle the additional traffic. There will be impacts,but they are not considered untoward. The LOS for the intersections on the hill will not change as a result of the development. 29. Intersection spacing was found to be able to meet standards for the new intersection,which will be controlled by a stop sign. 30. LOS of A and B exist for the critical intersections and those will not be changed by the development of the subject site, although as indicated, wait times may increase by a fraction of a second. 31. Street maintenance is accomplished as needed. No specific improvements outside the boundaries of the 0 plat will occur other than some possible modification to the intersection at Beacon and 7th. Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 • Page 10 32. The City works with applicants to develop a construction management plan to deal with traffic, routes and times in order to control access by heavy trucks. This would be done in this case as well. 33. There is an approximately 30 foot wide strip of land between the proposed development and River Ridge,the residential site adjacent to the subject site. Fences are not generally an environmental issue. Setbacks between newer single family and existing single family uses is also not considered a SEPA issue. The project will be providing the required setbacks, and in some instances it intends to provide larger than required setbacks. Larger setbacks than code provides are not required(minimum impacts that would occur with any development and not untoward in any fashion). The additional light and glare created by the new homes is not expected to be out of the ordinary for single family communities. It is not particularly reviewed for single family development. 34. While there is no public bus route serving the hill, residents can apparently use a dial-up service for vans. 35. The proposed density of 6.78 is in the midrange permitted in the R-8 Zone. The R-8 Zone permits a density of between 5 and 8 single family units per acre. 36. There is an approximately 30 foot wide strip of land between the proposed development and Falcon Ridge,the other residential site adjacent to the subject site. • 37. Mitigation fees for transportation are distributed after the City Council determines needs in its six year cycle. Maintenance is done as needed. 38. Construction activity and hauling is governed by code provisions limiting the impact on rush hour traffic and limiting it,generally,to daylight hours. In addition,there is the construction management plan. Trucks doing hauling are monitored and"weight tickets" and reports are required. Renton Avenue was checked and it is four inches of asphalt over crushed rock. The City found it acceptable for heavy loads. It currently serves large garbage trucks and fire trucks. 39. The proposed reduction in street width from 50 feet to 42 feet for new roads within the plat boundaries is a code compliance issue and should not generally affect SEPA compliance. 40. The question of who builds the homes and what would be their quality is not a SEPA issue. The City does not control design of single family development nor who may develop such homes if they meet code standards. 41. The applicant and City, in response to the appeal, both noted that asking a series of questions, particularly if the answers are contained in existing studies or covered by existing regulations,does not provide a sufficient basis for overturning a SEPA decision. 42. All of the Findings and Conclusions of the companion Plat Report are incorporated into this report by reference. • Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25,2001 orage I l CONCLUSIONS: 1. The decision of the governmental agency acting as the responsible official is entitled to substantial weight. Therefore, the determination of the Environmental Review Committee (ERC),the city's responsible official, is entitled to be maintained unless the appellant clearly demonstrates that the determination was in error. 2. The Determination of Non-Significance in this case is entitled to substantial weight and will not be reversed or modified unless it can be found that the decision is "clearly erroneous." (Hayden v. Port Townsend,93 Wn 2nd 870, 880; 1980). The court in citing.Norway Hill Preservation and Protection Association v. King County Council, 87 Wn 2d 267, 274; 1976,stated: "A finding is'clearly erroneous' when, although there is evidence to support it,the reviewing court on the entire evidence is left with the definite and firm conviction that a mistake has been committed." Therefore,the determination of the ERC will not be modified or reversed if it can meet the above test. For reasons enumerated below, the decision of the ERC is affirmed. 3. The clearly erroneous test has generally been applied when an action results in a DNS,since the test is less demanding on the appellant. The reason is that SEPA requires a thorough examination of the environmental consequences of an action. The courts have,therefore,made it easier to reverse a DNS. A second test,the "arbitrary and capricious"test is generally applied when a determination of • significance(DS) is issued.In this second test an appellant would have to show that the decision clearly flies in the face of reason since a DS is more protective of the environment since it results in the preparation of a full disclosure document,an Environmental Impact Statement_ 4. An action is determined to have a significant adverse impact on the quality of the environment if more than a moderate impact on the quality of the environment is a reasonable probability.(Norway, at 278). Since the Court spoke in Norway, WAC 197-11-794 has been adopted, it defines "significant"as follows: a. Significant. (1) "Significant" as used in SEPA means a reasonable likelihood of more than a moderate adverse impact on environmental quality. b. (2)Significance involves context and intensity...Intensity depends on the magnitude and duration of an impact....The severity of the impact should be weighed along with the likelihood of its occurrence. An impact may be significant if its chance of occurrence is not great, but the resulting environmental impact would be severe if it occurred. Also redefined since the Norway decision was the term "probable." C. Probable. "Probable"means likely or reasonably likely to occur, ...Probable is used to distinguish likely impacts from those that merely have a possibility of occurring,but are remote or speculative. (WAC 197-11-782). 5. Impacts also include reasonably related and foreseeable direct and indirect impacts including short- term and long-term effects. (WAC 197-11-060(4)(c)). Impacts include those effects resulting from growth caused by a proposal,as well as the likelihood that the present proposal will serve as precedent Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 • Page 12 for future actions. (WAC 197-11-060(4)(d)). 6. Environmental impact is also related to the location. A development, whether an office building or a single family development, may or may not create impact depending on the existing surroundings. 7. There is no question that there will be changes in the neighborhood and there may definitely be inconvenience, particularly during construction. There will be clear changes to the subject site. But these changes do not necessarily rise to the level of impact mandated by SEPA to require the - preparation of an EIS. The development will not significantly alter the character of the community. It will be single family in character,just like the surrounding development. Adding additional single family homes to the existing single family community is not dramatic. It will not trigger changes to other undeveloped or low density sites and will not create any precedents generating calls for changes to the residential zoning already governing the area. Both the Comprehensive Plan and Zoning designated the area for urban densities. In addition, while additional traffic will flow through the main commute route into downtown Renton,the proposed community is located on the edge of the community, not in the midst of the existing community,and its overall impacts will not be very significant. 8. Traffic seems to be a key issue presented by the appellant,and traffic's associated issues such as narrow and steep roads,heavy construction traffic and stopping distance and sight distance on the hill and at the new intersection. These are legitimate concerns, but the evidence does not provide a basis for altering the ERC's decision. They will not have more than a moderate impact on the quality of the environment. The development will permanently add more traffic of a kind that traffic analysis shows the streets currently handle without appreciably'increasing commute times,overloading roads or increasing conflicts significantly in terms of SEPA impacts that would require more detailed information than has been prepared inAhe various technical studies reviewed by the ERC. It will not have more than a moderate impact on the quality of the environment. The development will generate impacts similar to those that now exist. 9. There definitely will be more traffic. That occurs anytime new development occurs. The streets leaving the hill are definitely steep and narrow. The various analyses demonstrate that the LOS will not be substantially changed. The analyses also demonstrate that while there are some constraints due to the steepness of the hill and the narrowness of the roadway, but that the additional traffic can be safely accommodated. 10. The most pronounced change will be the removal of the forest cover on the ten acres. This acreage has been cleared in the past and the site topography altered by what appears to have been quarrying activity. But clearing of trees alone is not sufficient to trigger the preparation of an EIS. Nothing in record suggests that this alone will create such a significant impact on the quality of the environment that additional information is needed. This acreage needs to be looked at in the context of the adjacent 200 to 300 acres of forest and habitat. It also needs to be looked at in terms of surrounding uses. The areas around the site are mostly urban and developed with single family homes such as proposed for the subject site. There is already a park located immediately across from the site. While animals will probably be displaced, there appears to be sufficient open space immediately adjacent to the site to provide habitat. Nothing in the record demonstrates the any large species or threatened species • permanently inhabit the subject site. Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 •Page 13 11. Construction impacts will be irritating to those who live near the subject site and construction traffic will have impacts on the community as a whole,but they are not the type of impacts which have more than a short-lived impact and they are not the types of impacts that would throw the ERC's decision into doubt. In addition,code provides for construction management plans, and there remains the possibility that the pipeline road could serve some construction uses. In addition,the applicant has substantially reduced the amount of materials that would need to be transported either to or from the subject site. This will substantially reduce the originally anticipated truck traffic. 12. While there will be a series of impacts as there are in any development,they do not add up in a quantifiable manner to the type of impacts or long term precedents that result in more than a moderate impact on the quality of the environment. Issues such as quality or character of development, fencing, setback standards in excess of those required,code permitted exceptions to slope clearing or roadway width are not appropriately SEPA issues. Access to the site across the pipeline road is a condition of development, and if it were not granted, that would have a profound affect on the proposal and is not a SEPA issue. The creation of internal parks and open space and maintenance are not SEPA issues. The manner of adoption of the reclassification of the site is not a SEPA issue. 13. The reviewing body should not substitute its judgment for that of the original body with expertise in the matter, unless the reviewing body has the firm conviction that a mistake has been made. This office was not left with a firm conviction that the ERC made a mistake. There was a thorough review of • geotechnical information that showed the site could be developed. There were two traffic reports, including slope analysis of sight distance issues,that demonstrated the current roads, while not meeting current standards have capacity for the additional traffic anticipated. 14. The appealing party has a burden that was not met in the instant case. The decision of the ERC must be affirmed. DECISION: The decision of the ERC is affirmed. MINUTES: PRELIMINARY PLAT The following minutes are a summary of the November 16 and December 12,2000 preliminary plat hearing. The legal record is recorded on tape. The hearing opened on Thursday,November 16 at 11:35 a.m. in the Council Chambers on the seventh floor of the Renton City Hall. Because of time constraints,Mr. Mehlhaff, Ms.Liston, Mr.Giuliani,Mr. Ellis,Ms. Fulfer, Ms. Herman, Ms. Lamke,and Mr. Fulfer testified regarding the preliminary plat during the appeal portion of the hearing. Their comments appear later in the minutes. T ,be following exhibits were entered into the record for the preliminary plat hearing: Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25,2001 • Page 14 Exhibit No. 1: Yellow land use file,LUA00- Exhibit No.2: Overall plat plan 053,PP,ECF, containing the original application, proof of posting, proof of publication an other documentation pertinent to this request Exhibit No.3: Sheet 2 of 4, larger scale drawing of Exhibit No.4: Sheet 3 of 4, larger scale drawing of plat plan plat plan Exhibit No. 5: Sheet 4 of 4, preliminary plat plan . Exhibit No.6: Topographic survey Exhibit No. 7: Tree cutting and land clearing plan Exhibit No.8: Drainage control plan Exhibit No. 9: Generalized utilities plan Exhibit No. 10: Detailed grading plan Exhibit No. 11: Neighborhood detail map Exhibit No. 12: Zoning map Exhibit No:13: Plat map of lots along north border Exhibit No. 14: Timeline of project showing buffer Exhibit No:15: Wildlife Report Exhibit No. 16: Original plat map of River Ridge Exhibit No. 17: Stopping sight distances drawing Exhibit No. 18: Stopping sight distances chart Exhibit No. 19: Stopping sight distances chart and Exhibit No.20: Renton Ave. S. stopping sight topographic distances Exhibit No. 21: Traffic Count Charts(6 sheets) Exhibit No.22: Aerial photograph of River Ridge Elizabeth Higgins, Senior Planner,Development Services, 1055 S Grady Way,Renton, WA 98055 presented the staff report. Bennett Development has proposed subdivision of an approximately 450,846 square feet(10.35 acre)property into 57 lots suitable for detached,single family houses. The triangular-shaped property is 0located on Renton Hill,southeast of the intersection of Beacon Way S with SE 7th Ct,Jones Ave S,and South 7th St. Although Renton Hill is a well established neighborhood, land abutting the proposed project to the; north has been developed fairly recently into River Ridge, an eleven lot subdivision. Falcon Ridge,a large(80 lot)subdivision, lies to the southeast. Philip Arnold Park is adjacent to the southwest. The Seattle Public Utilities Cedar River Pipeline, which is used occasionally for overflow parking from the park,separates the park from the proposed development property. The zoning designation for the property is R-8. Most of Renton Hill is zoned R-8 except for a strip of land on the west side above I-405 which is zoned R-10. Access would be from a new public street that would intersect with SE 7th Ct. The new street would terminate in a cul-de-sac. An emergeney-only access would connect the cul-de-sac with the Seattle Public Utilities Cedar River Pipeline. A modification from street standards has been requested to reduce the width of the public right-of-way from 50 feet to 42 feet. This modification has been approved by the director of the Development Services Department. It would not reduce the pavement width,only the right-of-way width,and would not affect the ability to have sidewalks in the development. Ms Higgins continued by stating that the Environmental Review Committee(ERC) issued a Determination of Non-Significance- Mitigated on October 17,200. One appeal was filed prior to the close of the appeal period. The ERC placed several mitigating measures on the project. The first four relate to erosion control on the project and are best management practices as required by the City. The applicant shall pay applicable Transportation, Fire and Parks mitigation fees. The applicant shall follow the recommendations of the Geotechnical engineers as they pertain to site development and building construction. A note shall be placed on the face of the plat prior to recording stating that a known potential for ground subsidence exists in the area and that building plans shall be designed in consultation with a structural engineer and shall conform to the recommendations of the Geotech report. The rear setback at the lot located in the northeast corner of the wroperty, Lot#35, shall be increased to 25 feet from 20 feet. A note shall be placed on the title of the lot rohibiting building construction within 25 feet of the of the rear property boundary and prohibit land clearing Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 Wage 15 within 10 feet of the rear property line. The applicant shall ensure that all construction debris and discarded items are excavated from the site and construction is ceased immediately, followed by notification of the City of Renton Development Services Division within 24 hours, should hazardous material be discovered during the removal. The Construction Traffic Control Plan shall include a condition that the construction vehicles in excess of 20,000 gvw associated with the project would be prohibited from operating on Renton Hill during a.m.and p.m.peak traffic hours as identified in the traffic report. The applicant shall obtain an access permit in order to use the Seattle Public Utilities Cedar River Pipeline Easement for a secondary, emergency only access. The permit shall be obtained prior to building permits. Ms. Higgins described the property and discussed how the proposal meets the various requirements of the Preliminary Plat Criteria. The proposed project meets the first objective of the Comprehensive Plan Land Use Element by providing new housing in what up to now has been underutilized land. It also provides a greater use of urban services and infrastructure. The proposed project would meet the policy of meeting net density levels by providing density of 6.86 dwelling units per acre. The lots are proposed at an average size of 5,350 square feet. The range of lot sizes is 4,504 to 8,318 square feet. Both the Development Standards and the Comprehensive Plan polices limit the height of building to two stories in the R-8 zone. The question of transportation and pedestrian connections between neighborhoods is difficult on Renton Hill due to its situation of being isolated from the rest of the city and having limited access. There will be pedestrian connections throughout the neighborhood from new sidewalks that are going to be added and the Cedar River Pipeline. Three areas in the proposed site plan in the proximity of the entryway are going to be set aside as commonly held open,spaces. It is not anticipated that the vegetation will be retained,but they will be landscaped. Staff 4wecommends that a landscape plan be submitted to Development Services for review prior to building permits. e Comprehensive Plan included a forecast of Renton's traffic increase for a twenty year period. In the plan, it was estimated that there would be a 52%increase in traffic in Renton between 1990 and 2010. The estimated traffic increase on Cedar and Renton Avenues on Renton Hill would be approximately 25%from the proposed project. This appears to be consistent with projected city-wide traffic volume increases. Ms.Higgins discussed how the project meets the Housing Mandates in the Comprehensive Plan. The Growth Management Act requires the City to plan how it will accommodate its share of the projected population growth. The projected population growth for a 20 year period is determined by the Puget Sound Regional Council, and it was distributed to all cities and counties in the Puget Sound region. The Comprehensive Plan has to address how the City will provide housing for all economic segments of the City's population,and delineates the strategies for doing that. Ms Higgins reviewed some of the policies of the Housing Element and explained how they are met by the proposal. Ms.Higgins continued by reviewing how the proposal meets the Environmental Element of the Comprehensive Plan. Some of the policies that staff felt were met by the proposed project are: minimizing erosion and sedimentation by requiring appropriate construction techniques; implementing surface water management systems which protect natural features; promoting the return of precipitation to the soil at natural rates near where it falls through the use of detention ponds,grassy swales, and infiltration; promoting development design which minimizes impermeable surface coverage;and managing the cumulative effects of storm water through a combination of engineering and preservation of natural systems. Slopes on the property were probably created by surface mining activity, and are therefore exempt from the Critical Areas Ordinance. The stormwater control system would provide adequate protection of the City's Dater resource. The applicant has estimated that approximately 389 trees sized 6 inches in diameter and greater Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 • Page 16 and of various types would be removed from the property for construction. The applicant must adhere to the requirements of the Forest Practices Act. There are several areas in the project that are going to be preserved as "landscape tracts." The proposed project would meet all of the underlying zoning standards for the R-8 zone. The front, rear, and side setback lines indicated on the Preliminary Plat plan meet the minimum setback requirements for the R-8 zone. The maximum building coverage in the R-8 zone is 50% of lots 5,000 square feet or smaller and 35%of,or 2,500 square feet on, lots larger than 5,000 square feet. Compliance with the building coverage regulations would be a requirement of the building permit process. Ms. Higgins next reviewed the proposal's compliance with the subdivision regulations. All lots created by the subdivision would result in legal building lots according to the regulations for the R-8 zone. All parcels must have access-established to a public road,which would occur by either directly off the public roads that would be built or from the two private roads or driveway that would be placed on the property. Side lot lines shall be at right angles to street lines or radial to curved street lines--they would be in this project. All lot corners at intersections would have a radius of a minimum of 15 feet. Police and Fire have indicated they have sufficient resources to furnish services. The Parks and Recreation Department has also concurred that they could provide service. Renton School District has stated that new students, estimated to be approximately 25,could be accommodated in Talbot Hill Elementary School, Dimmitt Middle School,and Renton Senior High School. The School District further requested that the existing school busses be allowed to continue their route through the area, which would be allowed. The conceptual stormwater plan has been accepted by the Plan Review Division,as have the conceptual water and sanitary sewer plan. iStaff recommends approval of the Heritage Renton Hill Preliminary Plat subject to the following conditions: (1)that the applicant comply with the ERC Mitigation Measures as they have been amended,(2)that all landscape tract areas,with the exception of the 5,402 square foot tract located at the entry,the private "park", and the landscape area adjacent to the storm pond be incorporated into lots already proposed,and(3) commonly held open space areas shall be enhanced prior to occupancy with landscaping including mixed deciduous and evergreen trees and plantings of native shrubs and groundcover,and the applicant shall submit a landscape plan to the Development Services Department for approval. An additional condition would be that a homeowners'association be established and that one of the requirements be that they would be responsible for maintaining-,the private stormwater system and the commonly held landscape area, including the 15 foot buffers. The Examiner stated that he will schedule an evening hearing to conclude this matter in order to accommodate those who have to leave due to prior commitments. The various parties will be notified of the date and time of the evening hearing. The hearing closed at 12:40 p.m. ********************************** The hearing opened on Tuesday, December 12,2000,at 6:00 p.m. in the Council Chambers on the seventh floor of the Renton City Hall. Ms. Higgins gave a brief review of the project based on the Staff Report,which was presented at the hearing on December 16. Ms.Higgins stated that staff has added a recommendation which was not presented at the last hearing, that a Hold Harmless Agreement shall be recorded that indemnifies the City of Renton from any damage resulting from subsidence that may occur due to previous subsurface mining activities. Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 Wage 17 Mr. Fike presented a timeline explaining how the design for the project developed. In March of 1999 Renton School District selected Bennett Development as the purchasers. In September 1999 the mandatory pre- application meeting was held with the City. At that time plans for a 69-lot subdivision were submitted, designed around access from Beacon Way S. It was subsequently determined that Beacon Way S could not be accessed off of, since it is an easement owned by the City of Seattle and they do not want it used as a public right-of-way. In January of 2000,another pre-application meeting was held with the City of Renton and a new design for the project was submitted,based on input from community groups and the Cities of Renton and Seattle. This new design eliminated the Beacon Way access and showed access off of S 7th Ct. A stub road - that would cross over the pipeline and go into Philip Arnold Park was included. The City of Renton determined that the stub road was not needed. A design was subsequently developed showing a buffer setback along the north border of the property In April of 2000 the developer sent a submittal package to Renton Hill community leaders showing them what was going to be submitted to the City of Renton. This showed a 56-lot subdivision. In May,the City of Renton deemed the application complete, but asked that the access road across the pipeline be removed. With the removal of the access road,the project went from 56 lots to 57. The City also asked the developer to do additional traffic counts. A three-week traffic study was done during the summer which took into consideration increased traffic from sports activities held in the area. Mr. Fike submitted a study which was done by a wildlife biologist in the period since the last hearing. The report shows that there are deer on the property;however,there were no signs of deer nesting there. An eagle that nests on the south tip of Mercer Island uses the Cedar River as a fishing ground. This may be the eagle that is seen over the Cedar River and approaching the property. There are no signs of an eagle nesting on the roperty. The wildlife report shows that the project has minimal, if any,wildlife assessments. Regarding the pipeline easement, Mr. Fike explained that the City of Seattle views pipeline usage as a privilege. In order to be good neighbors with the City of Renton, Seattle overlooks things such as possibly driving trucks over the pipeline rather than through the neighborhood, and school buses using the pipeline. The City of Seattle will only issue Conditional Use Permits for the pipeline. The developer has a verbal agreement with Seattle that they will be able to have emergency vehicle access on the pipeline. Ms Higgins entered an original plat map which shows the entry to River Ridge as it was proposed,crossing the School District property,then intersecting the pipeline. A letter in the files from the City of Renton's Utilities Systems Manager at the time to the Real Property Division of the Seattle Water Department explains why the entryway to River Ridge was moved into the present position, and shows further evidence that the Seattle Public Utilities does not want the pipeline to be used for general traffic. John Nelson,Peterson Consulting Engineering,4030 Lake Washington Blvd NE,Suite 200,Kirkland, WA 98033 explained what sight distance is and what kinds there are, using a sight distances drawing. Using charts and a topographic map, he explained stopping sight distance and how it is determined for different types of vehicles and several actual road slopes in the Renton Hill Area. Mr.Nelson stated that as a result of his analysis and actually driving the roads in question, he did not think there is any significant problem with sight distances on the roads in Renton Hill. Larry Hobbs,Transportation Planning and Engineering, Inc.,2223 112th Avenue NE, Suite 101, Bellevue, WA 98004 stated that typically intersections are made with three or four legs; however, five-legged intersections do exist. All of the legs of the intersection are stop controlled. There are no records of any accidents at the Ontersection over the past five years. There is no reason to believe this intersection does not operate safely and Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA0O-149,AAD and LUAO0-053,PP,ECF January 25, 2001 • Page 18 adequately. There is enough capacity in the intersection to handle the traffic that is there now, and the future development. The intersection itself is relatively flat. Sight distance criteria does not come into effect at the intersection, since all vehicles must stop. Ms. Higgins clarified the Zoning Code as it relates to the project. In the R-8 Zone, the City requests that a developer try to have at least five units per net acre,with a maximum of eight units per net acre. If for some reason a developer chooses not to develop to the maximum density, or if they are trying to develop below the minimum density, the City requests that the developer demonstrate that future lots could be developed on ttie property. The City asks for a technique called shadow platting which would create hypothetical lots that would have the proper setbacks and be conforming lots given the requirement of that zone so that in the future those lots could be developed. Mark Mehlhaff, 532 Grant Ave S, Renton, WA 98055 addressed the issue of road safety on Renton Avenue S. Many drivers tend to use excessive speed going up the hill because of the steepness of the grade. This, combined with limited sight distances and cars parked on the side of the street,creates a dangerous situation. Mr.Mehlhaff asked why Puget Drive and the pipeline cannot be opened up for use of construction vehicles and general traffic to alleviate the congested conditions on Renton Avenue S and Cedar Avenue. Nancy Liston, 1518 Beacon Way S,Renton, WA 98055 spoke to the issues of tranquility and quality of life on Renton Hill. Ms. Liston expressed concern that the tranquility of the area would be greatly impacted by the increased traffic, noise,dirt and dust generated by the large trucks and construction equipment. She stated that • the streets and parks on the hill were never intended for the increased number of vehicles and people who will be occupying 57 homes. Ms. Liston also discussed the issue of intersection safety. She has witnessed people not obeying the stop signs,and has seen many near-misses. Ms. Liston also expressed concern about deer crossing the street, particularly at night, and the safety of bicyclists on the streets. John Giuliani, 1400 South 7th Street, Renton, WA stated that the new exit off of Renton Hill has no bearing on the traffic on Renton Avenue,since it is necessary to travel on Renton Avenue to get to the new exit. Mr. Giuliani further stated that when Renton Ave was repaved, he personally observed that all the asphalt was removed down to the dirt. New asphalt was placed directly on top of the dirt with no gravel base underneath to anchor it. Quentin Ellis,715 High Ave S., Renton, WA 98055 stated that there have been a lot of sophisticated studies made by the City and others regarding this project,but it all boils down to one word--infrastructure. The infrastructure that has to be maintained is not there. He cited a newspaper article regarding the Habitat program's plan to build low income housing on a ten acre parcel in Snoqualmie Ridge. They are only proposing to build 50 houses on those ten acres. This proposed project plans to build 57 homes in an area with only one street that is only 23.6 feet wide, as opposed to the normal 40 to 50 foot width. He expressed concern about the mine shafts in the area and the possibility of sink holes developing with the increased traffic on Renton Avenue S. Mr. Ellis challenged Bennett Development's traffic engineer to substantiate his statement that there would not be an increase in the number of accidents on Renton Hill. He questioned how,considering the 25% increase in traffic anticipated, the engineer could make that statement. Wendy Fulfer, 1729 SE 7th Ct,Renton, WA 98055 stated she lives in River Ridge. The intersection where she comes out of her development is already a five-way intersection. Adding another street would only add to the .difficult situation at the intersection. Ms. Fulfer added that she personally makes eight to ten trips off the hill Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 age 19 every day. She expressed concern about the deer and other wildlife in the area, including nesting eagles, if the property is developed. Sharon Herman, 711 Jones Ave S,Renton, WA 98055 stated that the contractor of River Ridge had the opportunity to build 23 homes. He elected to build only 12 homes out of respect to the neighborhood and the residents of Renton Hill. Ms. Herman further stated that she feels the property value of her home will drop because of all the traffic and the smaller homes that will not fit in with the rest of Renton Hill. Becky Lamke,415 Cedar Ave S,Renton,WA 98055 stated that she feels the massive size of the project is an undue burden to the current residents of the Hill. The number of cars and speed of the vehicles on Cedar Ave is already excessive for the number of homes that are there. The project should be forced to have their entrance and exit off of Puget Drive. The increased traffic and safety issues due to the slope of the streets all lead to Puget Drive being the best alternative. Ms.Lamke asked why Renton School District is still listed as the owner. She questioned whether the property been sold,or if that is contingent on whether the project is approved. Ms.Lamke stated that a clear cutting of this ten acres of mature forest could be detrimental to the Cedar River and to salmon recovery. Mike Fulfer, 1729 SE 7th Ct, Renton, WA 98055 asked why the buffer on the north edge of the project was included in the setback of the homes and not separate from the lots. He asked who is responsible for providing and maintaining the vegetation in the buffer. He expressed concern about the increased number of trips per day as a result of the new homes. He further stated that the project will be out of place because of the density of the Ames,and will change the character of the neighborhood and quality of life of the residents.Mr.Fulfer cussed stopping distances of vehicles and expressed concern that the stopping distances involved are right on the limit of safety. Being on the edge of safety should only be allowed in a controlled environment such as a race track,not on Renton Hill. Bentley Oaks, 1321 S 7th, Renton, WA 98055 addressed the sight distances issue. Most people drive in excess of 30-35 mph on Renton Ave. S. Considering the reaction time required,and trying to find a place to stop because of parked cars along the street,it can be a dangerous situation. It is important that the human factor be considered rather than just using an engineering study. Doug Brandt 610 Renton Ave. S, Renton, WA 98055 asked if Mr.Nelson made specific measurements on the two crests that exist on Renton Ave. S.or if he relied only on charts for his analysis. Mark Johnson,316 Renton Ave. S.,Renton,WA 98055 questioned the 6%grade, which is an average. The transition between 3%and 9% is sudden,so that close to the end of the 3%grade, it is effectively a 9%grade, not an average of a 6%grade. That would make a dramatic difference in the calculations. He expressed concern that cars are moving in both directions,the road is narrow, cars and trucks are parked on the side,and there is nowhere to go. Regarding speeds on the bridges, Mr.Johnson stated that speed limits are not observed. He feels that adding more cars is not something the road can handle safely. Dana Calhoun,433 Cedar Ave.S,Renton, WA 98055 stated that she feels the sidewalks, particularly on Renton Ave. S,are inadequate. The intersection at 7th and Beacon Way is very busy,especially during softball games. There are no crosswalks, and sometimes no sidewalks. Bicycling on the streets is dangerous. Ms. Calhoun said -zhe backs into her driveway because she does not want to have to back onto the street considering the Ogerous conditions that exist Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25,2001 • Page 20 Bill Collins,420 Cedar Ave. S., Renton WA 98055 entered traffic count charts that are a graphic version of traffic issues on Renton Hill. Using these charts, Mr. Collins explained how the increased number of cars would impact traffic conditions on various roads at various times of the day in the Renton Hill area. Rosemary Grassi,422 Cedar Ave. S,Renton, WA 98055 stated that this traffic count information was provided by Mr.Mar from the City. It is the City's latest official count of traffic on Renton Hill. The counts show that there would be 813 passes of vehicles on Cedar Avenue per day. On Renton Avenue S, there will be around 1,100 passes per day. There is also a problem of enforcement regarding stop signs. Ms. Grassi stated the Mr. Potter,who is president of the Falcon Ridge Homeowners Association, has signed a statement that he is opposed to this development. She also expressed concern that their appears to be an effort to"dump" affordable housing and apartments from other cities into Renton. Linda McManus, 530 Renton Ave. S., Renton, WA 98055 addressed the issue of accidents on Renton Ave. S. Ms.McManus stated that she was personally involved in an accident last summer on Renton Ave. S. The person coming down the hill failed to yield,and Ms.McManus' vehicle was forced into a telephone pole. She does not know why this accident wasn't recorded. Ms. McManus stated she has personally witnessed many near-accidents on Renton Hill S. She expressed her concern about safety issues in general in the Renton Hill area. Bart Bennett, 1800 SE 7th Ct., Renton, WA 98055 expressed concern that Lot#35 does not have the 15 foot greenbelt that the other lots in the development have. He also expressed concern about the possibility of the 5- way intersection being changed into a 7-way intersection. -He questioned the distances of the stop signs from the intersection. Mr. Bennett also stated that the intersection of Renton Ave. S and 7th is a 3-way stop,which is also extremely dangerous because of the steepness of the hill. He feels that his project is too large for the street system to handle. Mr. Bennett stated that he lives on Lot#5 in River Ridge. He has a sink bole in his back yard which he has dumped about 50 bags of sand into,and it is still fairly deep. Ruth Larson, 714 High Avenue S, Renton, WA 98055 stated that the residents of Renton Hill did not oppose River Ridge because it brought sewer service to those people living above Renton Avenue S. They were not opposed to Falcon Ridge. The only problem with Falcon Ridge was that their original plan was to remove the gate and use=the pipeline for access. The residents did not want the gate removed because of traffic concerns. Falcon Ridge put in their own access road instead. Ms.Larson reviewed the safety issue on Renton Avenue S, and stated emphatically that this issue must be addressed before approval. Kayren Kittrick stated that there is an enforcement issue regarding traffic in the Renton Hill area. The City has programs in place for monitoring these things,and the Police Department should be made aware of the problem. If the City does improvements on Renton Avenue South,it means the streets and sidewalks will be widened,which will take away from front yards along the street and actually increase traffic speeds on the street will increase. The blocking off of the lane on Mill Avenue by Metro is temporary during the;construction of the Transit Center. Regarding reports of accidents on Renton Hill,these were done by checking Police reports.The Police Department reported three accidents in five years. All of them involved hitting of stationery objects. Ms. Kittrick stated that pipeline is allowed to be used for emergency access only,not for general access. The pipeline is gated at the request of the local citizens in order to decrease traffic,and can be opened .only for emergency access. Regarding sinkholes,Ms. Kittrick stated that the City maintenance crews have been monitoring the sink hole on Renton Avenue S. She has no other reports of sink holes in the area. Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 *age 21 Ms.Higgins stated that the Geotechnical Report indicates there is no surface evidence of former coal mines. The area is very inadequately mapped, so no one really knows if there are mines in the area or where they are located. Residents of the area have had problems with sink holes. That is the reason the City wanted to make sure that new residents would at least receive a warning that this could be a problem so that they could plan for it by having a structural engineer design the foundations of their house. Mr.Nelson discussed the enforcement issue on Renton Hill. The developer cannot and should not try to accommodate people who do not follow the law. Mr.Nelson discussed reaction times and sight distances and stopping times of trucks. He also described the locations where measurements were made for the study and the relationship of road grades and sight distances. Mr.Nelson described how the intersections at 7th and Renton Avenue and 7th and Cedar Avenue are controlled with stop signs. Mark McGinnis Geotech Consultants, 13256 NE 20th Street#16,Bellevue, WA 98005 addressed the issue of coal mines and the question of a sink hole at Lot#5 in River Ridge. There is a deep mine under this area that is over 500 feet below ground surface. The shallower mine workings,which are the ones that seem to be giving the most problems on Renton Hill, do not extend that far to the east into the River Ridge development or into the proposed project's property. There are shallow mines under the western portion of Renton Hill,but they would not be under Lot#5. Regarding the subsidence on Renton Avenue S,Mr. McGinnis stated that he drove the street again and noticed many patches in the road, indicating some repaving and filling. The size of the patches is relatively small. Subsidence associated with a coal mine,related either to an air shaft or the collapse Of the tunnel itself,would be several thousand square feet in size. The small areas of subsidence and patching n Renton Avenue S appear to be related to utilities, improper compaction,or soft road sub-grade conditions that have been dealt with over time. Considering the depths of the mines, and the time that has elapsed since the last known workings under the property(at least 75 years) if large subsidence were to occur, it would have occurred already. Ms.Higgins discussed the issue of the increased setback on Lot#35 and the reasons for it. Ms.Higgins explained that we encourage quality development by looking at the layout of the plan and making sure it meets the requirements of the development standards that are set forth in the Code. Those are the minimal standards the City Council has felt should be applied in each neighborhood. Other factors that are looked at are the context of the project,development that has taken place in the past,and how the City plans to develop in the future. The City has housing goals that have been set by the Puget Sound Regional Council as to the amount of population that Renton, as well as other cities that are within the Growth Management Act,must meet. Regarding the question of stormwater drainage,Ms.Higgins stated that roof drains will be allowed to infiltrate. Stormwater from the driveways and streets would be collected in the stormwater pond, where it would receive treatment prior to release. It would be a controlled release,as there have been some stormwater problems in that area. Mr. Hobbs stated that the January 2000 Traffic Study was done based on the then current lot number count of 60 lots. This would mean a net reduction of 3 p.m.peak hour trips,and roughly 30 daily trips. The Traffic Report shows that there will be less than 1,500 trips per day on Renton Avenue S,which will be well below capacity for a one-way section. Mr. Hobbs stated that there would be an increased traffic volume on Renton Hill from this project. Regarding safety on Renton Hill, Mr. Hobbs said his statement that accidents should increased was based on accidents of record. The enforcement issue of people not obeying stop signs and speed its is a consideration. Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 • Page 22 Mr. Giuliani stated that the air shafts from the underground mines are made of wood timbers and are approximately 14 to 15 feet in diameter. He expressed his concern that the wood timbers will rot over time. There have already been three incidents of cave-ins. One took place across the street from his home. The air shafts were not blocked off from the mines below, they were filled and blocked off 50 or 75 feet from the top. The passage of time makes the situation more dangerous, not less so. Mr.Brandt questioned exactly where Mr.Nelson made the sight distance measurements on Renton Hill. Mr.Nelson replied that graphical measurements were made on A Avenue from the project site all the way down to Renton Avenue S and Cedar, then all the way down Renton Avenue S and Cedar to the bottom of the hill. These were graphical measurements made on the computer. On-the-ground field work was done all the Way up Renton Avenue S. Jeff Schultek, 613 Grant Avenue S, Renton, WA 98055 stated that sometime between 1980 and 1982,a garage was taken down through a sink hole at 820 Renton Avenue S. Mr. Ed Gouch owned the property at that time. Mr. Schultek expressed his concern about safety issues on Renton Hill, particularly in regard to emergency vehicle access. Ms. McManus expressed her concern that the Geotechnical Report has a disclaimer on it. Ms.McManus stated that she has a sinkhole on the side of her property. Her neighbor, Marie Overman,has had to have coal mining •engineers flown in from Montana because her driveway caved in. Ms. Gygi stated that Bennett Development does not object to the idea of a Hold Harmless agreement that would be a covenant against the land itself. Bennett Development does object to the idea of a bond being placed that would the hold the developer liable into the future. The Examiner called for further testimony regarding this appeal. There was no one else wishing to speak. The hearing closed at 9:00 p.m. PRELEVIINARY PLAT FINDINGS CONCLUSIONS&RECOMMENDATION Having reviewed the record in this matter, the Examiner now makes and enters the following: FINDINGS: 1. The applicant, Ryan Fike,Bennett Development filed a request for approval of a 57-lot Preliminary Plat together with Tracts for open space. 2. The yellow file containing the staff report,the State Environmental Policy Act(SEPA)documentation and other pertinent materials was entered into the record as Exhibit#1. 3. The Environmental Review Committee(ERC), the City's responsible official, issued a Declaration of Non-Significance-Mitigated(DNS-M)for the subject proposal. An appeal of that determination was filed by the Renton Hill Community Association. A hearing on that appeal was consolidated with the • hearing on this plat. Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 0age 23 4. The subject proposal was reviewed by all departments with an interest in the matter. 5. The subject site is located near the intersection of Beacon Way SE, S 7th Court and S 7th Street. The property is located immediately across from Philip Arnold Park. 6. The subject site a triangular parcel approximately 1.114 feet by 818 feet by 829 feet. 7. The subject site is approximately 10.35 acres or 450,846 square feet in area. ' 8. The subject site has rolling terrain but has steeper slopes along the northeast corner of the site. There are also some steeper slopes on the interior of the subject site that were determined to be manmade as part of past mining or quarrying activity. An exemption from steep slope regulations was issued administratively since the steeper slopes are not natural. 9. Although the slopes are not regulated by the Land Clearing and other development regulations,the ERC imposed a series of conditions to control erosion and deal with geotechnical issues. The subject site is located within Aquifer Protection Area 2. 10. The subject site was annexed to the City with the adoption of Ordinance 1861 enacted in February 1961. 1. The subject site is currently zoned R-8 (Single Family-8 dwelling units/acre). It received this designation in June 1993. 12. The map element of the Comprehensive Plan designates the area in which the subject site is located as suitable for the development of single family uses. 13. The subject site is vacant. It currently,is owned by the Renton School District but the applicant has an option to purchase the property. 14. The applicant proposes dividing the subject site into 57 single family lots. There would also be tracts for storm water detention and open space. Staff has recommended that most of these tracts be incorporated into adjacent lots to minimize potential maintenance issues. 15. The development of the subject site would require tree removal. Approximately 389 trees of 6 inches or greater diameter would be removed to allow for the construction of roads,building pads and storm drainage systems. A Class IV permit will be required to convert forest land to residential purposes. The applicant has indicated an intention to save some trees near the detention pond and property entrance if grading work permits. 16. The lots range in size from 4,504 square feet to approximately 8,318 square feet. Staff estimates that the average lot size would be approximately 5,350 square feet. The minimum lot size permitted in the R-8 zone is 4,500 square feet. 0 Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 • Page 24 17. The Beacon Way Seattle Pipeline Road runs in a southeast to northwest diagonal along the southwest angle of the subject site. It connects to Puget Drive SE and Royal Hills Drive SE on the east. The roadway is not a public roadway and has a gated barricade to prevent through traffic. Philip Arnold Park is located on the southwest side of that roadway. The road does provide access to Philip Arnold Park from the east. School buses also use this road approaching from the east, and a school bus stop is located east of the barricade. School buses do not negotiate the steep hills from the I-405 side of Renton Hi 11. 18. Apparently,the pipeline road was open as a through-street in the past but was closed to reduce traffic passing across Renton Hill and down the steep roadways east of 1-405. This also coincided with the then limitation of only one crossing of I-405 that also crossed railroad tracks that could totally block access to the hill. Reconstruction and realignment of 1-405 during the last decade provided a second crossing of 1-405, and both crossings are elevated and therefore removed the railroad crossing. 19. The proposed layout would create a looped roadway in the interior of the plat with a cul-de-sac road providing access to the southeast corner of the subject site. A gated,emergency access connection would be installed between the dead end cul-de-sac and the Seattle Pipeline roadway,with Seattle's permission. 20. The proposed roadways would be 42 feet wide instead of the standard 50 feet, since the applicant requested an administrative modification to reduce width,which was approved. Road dimensions are determined by the Director administratively. 21. The lots would be-located along the perimeter of the triangular shaped parcel as well as in the interior of the loop. The interior block would contain 13 single family lots as well as a"park"tract. 22. Eight lots would be served by either pipe stem or private roadways. Proposed Lots 14, 15, 16 and 17 would be served by private access easement or roads. Similarly,Proposed Lots 20, 21 and 22 would be served by private access roadway. Proposed Lot 35 would be located on a pipe stem driveway. 23. In order to prepare the site for the building pads and the new roads,the applicant will clear most of the vegetation from the site. Some trees may be preserved near the detention system. The slopes adjacent to Proposed Lot 35 would remain undisturbed, since there are steeper slopes that will be protected. 24. The applicant proposes open space and the storm water detention pond at the entrance to the plat. The road will pass through this open space. As the roadway splits to form the loop roadway,a small park will be located on the inside of the "Y" in the road. The applicant has proposed three triangular landscaped areas along the pipeline road to fill in between rectangular lots. Since the pipeline road runs at an angle,creating rectangular lots required these open space areas. As noted,staff recommended that these areas be incorporated into the adjacent lots to avoid maintenance problems. 25. Development of 57 single family homes will generate approximately 545 vehicle trips per day(based on approximately 9.55 trips per dwelling). It is anticipated that approximately 10%of the traffic trips will occur at each of the morning and evening peak hours. Staff has also estimated that the 57 homes will increase traffic on Renton Hill by approximately 25 percent. This is based on the fact that there Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25,2001 • Page 25 are approximately 200 homes on the hill currently. The ERC imposed mitigation measures for fee generation. Staff noted that the City anticipated an increase in overall traffic of approximately 50 percent,and that the 25 percent increase was reasonable. 26. The traffic analysis shows that the major intersections serving this site,Main Avenue S and S 4th Street, Houser Way and Mill,Cedar and S 3rd and Renton Avenue and S 7th will suffer no degradation in LOS. The LOS for the first two intersections will remain at B,while the latter two intersections would remain at LOS A. 27. An analysis of historical traffic accidents showed only three minor accidents and no accidents resulting in injuries. Residents report that there have been a number of"near-misses"and residents living along Renton and Cedar must exercise diligence in using the driveways. 28. The width and slopes of Renton Avenue and Cedar and the other roads serving the subject site from downtown Renton, the only open access to the hill, do not meet current development standards. At the same time, staff reports that these roads have capacity to handle additional traffic and that these roads can also safely handle the additional traffic. Staff did suggest that new residents would have to adjust to the conditions of access just as other residents on the hill have adjusted in the past, including other new residents. 29. The development of the subject site will generate approximately 25 school age children. These • students would be spread among the different grades of the Renton School District. 30. The City will provide sanitary sewer service and domestic water. 31. The ERC imposed additional storm water detention requirements due to the topography and Iocation of the subject site. The proposal will have to comply with the newest King County requirements. Staff reports that the conceptual drainage plan appears to adequately serve the subject site. Staff recommended a homeowners association be required to maintain the detention system. 32. While traffic and transportation issues were a main concern of the neighbors,the Transportation Division did not appear at the public hearing. Questions were-handled by other planning and development staff. 33. In addition to the steep slopes along the northeast margins of the subject site, the subject site is located over old,abandoned coal mine tunnels and other workings. Old records and maps were also reviewed. The property was surveyed and inspected and did not show any evidence of mines or shafts. It does appear that the site was a quarry at one time. There are disturbed soils and slopes. A geotechnical analysis provides methods for preventing foundations from being affected if there should be subsidence. The studies also had other suggestions for dealing with the subject site, but indicated that there should not be any problems evident at the surface. Apparently,there have been incidents on the hill of subsidence in the past. The geotechnical information shows that the soils can bear development. The City did recommend that the applicant execute a "hold harmless"agreement regarding the coal mines in case some problems were to arise. Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 • Page 26 34. In order to develop the subject site, the applicant will be excavating and filling the subject site. Originally, the applicant was going to export and import materials to level the site. The applicant proposes to alter those plans and do a balanced cut and fill. This will reduce the amount of materials that need to be transported to or from the subject site, reducing the number of truck trips substantially. 35. Development of the subject site will not change the single family character of the area but will generate additional population and traffic as well as other attendant changes more people bring to an area. 36. The homeowners would be required to maintain the open space tracts at the entrance and the park area. 37. All.of the Findings and Conclusions of the companion SEPA Appeal Report are incorporated into this report by reference. CONCLUSIONS: 1. The public interest in approving a preliminary plat depends on balancing a variety of interests. The City is bound by the Growth Management Act and has determined the appropriate density under that act for R-8 Districts is between 5 and 8 dwelling units per acre. For this parcel with a net site area of 8.31 acres, the 57 homes yields a density of 6.86 dwelling units per acre. At the same time, the increase in traffic projected for this project is approximately 25 percent over current traffic. This is not an issue that merely equates to LOS and technical issues. This means approximately 550 additional trips will be traveling up and down very steep, narrow roads. Staff noted that the Comprehensive Plan forecast a growth of 52 percent, but those projections would clearly have a lot of that traffic directed efficiently to arterial streets and not narrow streets with single family homes located on very steep streets. These narrow roads serve as collector arterials, but are in no way equal in width or slope to roads that would generally serve that purpose. Renton and Cedar and the streets nearest the subject site are local residential access streets. In fact,they are substandard streets in both width and slope angle. Five hundred additional trips per day is a substantial impact on the homes along the route from the subject site to the downtown area. The public interest sought to be served by approving a plat is not solely served by providing additional housing that meets density standards and growth management standards that do not consider the neighborhood characteristics, and particularly the street characteristics. The public interest is served when one balances density with the impacts of development on other homes and their residents. Engineering design standards to not measure or balance these impacts. They clinically decide that a certain pavement width is adequate to accommodate any additional 500 trips per day,without weighing the affects on adjacent residents. The number of trips will balloon from approximately 2,000 trips per day to 2,500 on Renton and Cedar. Similarly,engineering values on sight distance over the crest of a hill cannot discount the neighbors evidence of"near-miss" accidents as vehicles attempt to avoid each other when negotiating the steep, narrow streets. The engineering numbers do not necessarily account for slowed reaction time of elderly drivers or the impatience of teenage drivers. Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 •Page 27 Therefore, it seems that balancing the demands of growth management with the impacts on the residents along the commute route requires reducing the scale or scope of the project and the density of that project. The Zoning Code and Comprehensive Plan both provide a range. While it has been generally the case that the density should be as great as possible to meet the housing demands,there may be appropriate times when that density should be reduced modestly to effectuate a balancing of interests. While any reduction will be modest, it still would help to ameliorate the impacts on the existing community. Scaling the plat back to 50 homes would provide a density of 6.02 dwelling units per acre. This falls within the permissible range of 5 to 8 found in the regulations but reduces the - impacts. There would be approximately 50 less vehicle trips and while,not a substantial amount, it would go to lessen the impacts on the residential homes along the route and reduce the potential for vehicle conflicts somewhat. Reducing the density of this plat will reduce the untoward impacts on the existing residents. 2. The applicant will probably be heard to argue that the SEPA review did not warrant this reduction and that no significant impacts having more than a moderate impact on the quality of the environment were found. "Significance" in terms of SEPA and whether it amounts to EIS threshold "significance" is entirely different than the localized but very consequential impacts of 500 to 600 additional vehicle trips on a local,residential street. Just because an issue is not so large or significant to trigger the need for EIS preparation does not mean it does have an impact which should not be mitigated when determining whether a plat serves the public use and interest. In this case,the.additional traffic vis a vis the streets that would serve this traffic demand a density reduction. .. The applicant could choose to implement such a reduction by either maintaining the general lot size and increasing the open space and secondarily preserving additional trees or by modestly increasing the lot sizes of the remaining 50 lots. Rather then specify the method,the recommendation would be to allow the applicant flexibility in this redesign. 4. In general,with the proposed density reduction, the proposed plat appears to serve the public use and interest. It does provide additional housing choices in an area that can be adequately served by water and sewer and to a lesser extent,the steep narrow roads of Renton Hill. The plat is somewhat isolated from surrounding development and buffers between the subject site and adjacent properties have been provided. 5. The plans show that site can deal with its storm water runoff. As noted, it can be served by City water and sewer. 6. It would appear that there is a remote potential for instability due to the underlying coal workings. There remains the potential to discover overgrown or ineffectively sealed off shafts. The applicant will be required to follow the procedures outlined in the geotechnical reports to develop the site and home foundations. The recommendation of staff for a hold harmless agreement seems reasonable in the event a unforeseen settlement occurs in the future. Potential residents should be given adequate notice that their is some potential for a coal mine subsidence to occur. 7. The proposed layout appears reasonable. In most cases where "interior" lots would be accessed by easement or private roads or pipe stems, these lots are not sandwiched into compounds surrounded on Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 • Page 28 four side by other homes. A number of these lots are located on the pipeline or at the open space edges of this site. 8. The ERC imposed conditions to avoid exacerbating drainage problems down stream and to avoid erosion. Storm water will be contained and diverted to avoid excessive flows. The development to R-8 density standards and the need to create building pads and streets means that most of the vegetation will be removed from the subject site. 9. The proposed plat will provide additional housing choices in an area in which urban services are provided or can reasonably be provided. 10. Development of the site will introduce additional noise and population. 11. The plat provides reasonably rectangular lots and lots that meet the dimensional requirements of code. The open space between lots along the pipeline road does appear to be a potential maintenance problem, particularly with access to the pipeline road roundabout or circuitous from the main plat. These open space parcels should be absorbed into the adjacent lots. 12. The other open space parcels should be restricted by language on the face of the plat that preserves their open space characteristics and precludes selling them off for development in the future. • 13. The plat will have its main access to a street which appears capable of providing a safe controlled intersection with appropriate sight and stopping distances. There will be a need to provide assurance that the Seattle pipeline road can be used for emergency access. 14. As a final recommendation,this office would recommend to the City Council that it explore providing the primary access to this plat from the pipeline road with a gated access to the remainder of Renton Hill. If such access could be granted,the narrow and steep streets would not be a issue and the plat could be built to full density. This office was not fully permitted to explore whether this was at all possible. This office only has anecdotal evidence that Seattle,at one time,permitted unobstructed access to Renton Hill from the east. This office does not suggest a full opening but again,recommends that primary access to this plat might be from the east with a gated emergency access at SE 7th Court to prevent through traffic movements. 15. In conclusion,the proposed preliminary plat should be approved by the City Council subject to the conditions noted below. RECOMMENDATION: The City Council should approve the Preliminary Plat subject to the following conditions: 1. The plat should be reduced from 57 to 50 single family lots with a density of 6.02 dwelling units per acre. This falls within the permissible range of 5 to 8 dwelling units per acre. 2. The applicant shall comply with the conditions imposed by the ERC. Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 •Page 29 3. The plat shall contain language acceptable to the City Attorney regarding the recreational and open space respectively and precluding development of them. 4. All landscape tract areas, with the exception of the 5,402 sf tract located at the development entry,the 3,042 sf private"park", and the landscape area abutting the stormwater tract, shall be incorporated into lots already proposed within the plat. No additional building lots are to be created. A revised plan shall be submitted to the Development Services Division prior to receiving construction permits. 5. Commonly held open space areas shall be enhanced,prior to occupancy,with landscaping including ' mixed deciduous and evergreen trees and plantings of native shrubs and groundcover. The applicant shall submit a landscape plan to the Development Services Department for approval. 6. A Hold Harmless Agreement shall be recorded that indemnifies the City of Renton from any damage resulting from subsidence that may occur due to previous subsurface mining activities. 7. The applicant will have to secure in writing permission to use the Seattle pipeline road for emergency access. 8. The homeowners would be required to maintain the open space tracts at the entrance and the park area. •ORDERED THIS 25th day of January, 2001. FRED J.KA HEARING EXAMINER TRANSMITTED THIS 25th day of January, 2001 to the parties of record: Zanetta Fontes Jennifer Steig Sharon Herman 1055 S. Grady Way Peterson Consulting Engineering 711 Jones Avenue S Renton, WA 98055 4030 Lake Washington Blvd NE, Renton, WA 98055 Suite 200 Kirkland, WA 98033 Elizabeth Higgins John Nelson Mike Fulfer 1055 S Grady Way Peterson Consulting Engineering 1729 SE 7th Ct. Renton,WA 98055 4030 Lake Washington Blvd NE, Renton, WA 98055 Suite 200 Kirkland, WA 98033 Kayren Kittrick Becky Lamke Bently Oaks 1055 S Grady Way 415 Cedar Avenue S 1321 S 7th .Renton, WA 98055 Renton, WA 98055 Renton, WA 98055 Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 • Page 30 Ruth Larson Mark Mehlhaff Doug Brandt 714 High Avenue S 532 Grand Avenue S 610 Renton Avenue S Renton, WA 98055 Renton, WA 98055 Renton, WA 98055 Ann M. Gygi Nancy Liston Mark Johnson Hillis Clark Martin &Peterson 1518 Beacon Way S 316 Renton Avenue S 500 Galland Building Renton, WA 98055 Renton, WA 98055 1221 Second Avenue Ryan Fike John Giuliani Dana Calhoun Bennett Development 1400 S 7th Street 433 Cedar Avenue S 9 Lake Bellevue Dr., Suite 100-A Renton, WA 98055 Renton, WA 98055 Bellevue, WA 98005 Larry Hobbs Quentin Ellis Bill Collins Transportation Planning& 715 High Avenue S 420 Cedar Avenue S Engineering,Inc. Renton, WA 98055 Renton, WA 98055 2223 112th Avenue NE, Suite 101 Bellevue, WA 98004 . Mark McGinnis = Wendy Fulfer Rosemary Grassi Geotech Consultants 1729 SE 7th Ct. 422 Cedar Avenue S 13256 NE 20th St., 416 Renton, WA 98055 Renton, WA 98055 Bellevue, WA 98005 Linda McManus Bart Bennett Jeff SchuItek 530 Renton Avenue S 1800 SE 7th Ct. 613 Grant Avenue S Renton, WA 98055 Renton, WA 98055 Renton, WA 98055 This report was mailed to other Parties of Record. A complete list of the Parties of Record is available in the Hearing Examiner's office. TRANSMITTED THIS 25th day of January, 2001 to the following: Mayor Jesse Tanner Gregg Zimmerman,Plan/Bldg/PW Admin. Members, Renton Planning Commission Neil Watts,Development Services Director Larry Rude,Fire Marshal Lawrence J. Warren,City Attorney Transportation Systems Division Jay Covington,Chief Administrative Officer Utilities System Division Councilperson Kathy Keolker-Wheeler Sue Carlson, Econ. Dev. Administrator Betty Nokes,Economic Development Director South County Journal Larry Meckling,Building Official • Heritage Renton Hill Appeal and Preliminary Plat Hearings File Nos.: LUA00-149,AAD and LUA00-053,PP,ECF January 25, 2001 •Page 31 Pursuant to Title IV, Chapter 8, Section 100G of the City's Code, request for reconsideration must be filed in writing on or before 5:00 p.m.,February 8,2001. Any aggrieved person feeling that the decision of the Examiner is ambiguous or based on erroneous procedure,errors of law or fact, error in judgment, or the discovery of new evidence which could not be reasonably available at the prior hearing may make a written request for a review by the Examiner within fourteen (14)days from the date of the Examiner's decision. This request shall set forth the specific ambiguities or errors discovered by such appellant,and the Examiner may, after review of the record,take further action as he deems proper. An appeal to the City Council is governed by Title IV,Chapter 8, Section 110,which requires that such appeal be filed with the City Clerk,accompanying a filing fee of$75.00 and meeting other specified requirements. Copies of this ordinance are available for inspection or purchase in the Finance Department, first floor of City Hall. If the Examiner's Recommendation or Decision contains the requirement for Restrictive Covenants,the executed Covenants will be required prior to approval by City Council or final processing of the file. You may contact this office for information on formatting covenants. The Appearance of Fairness Doctrine provides that no ex parte(private one-on-one)communications may occur concerning pending land use decisions. This means that parties to a land use decision may not communicate in private with any decision-maker concerning the proposal. Decision-makers in the land use process include both the Hearing Examiner and members of the City Council. W11 communications concerning the proposal must be made in public. This public communication permits all interested parties to know the contents of the communication and would allow them to openly rebut the evidence. Any violation of this doctrine would result in the invalidation of the request by the Court. The Doctrine applies not only to the initial public hearing but to all Requests for Reconsideration as well as Appeals to the City Council. • • • N W 5; CITY OF RENTON`� t Ott Planning/Building/Public Works Department Jesse Tanner,Mayor Gregg Zimmerman P.E.,Administrator • October 19, 2000 _ OCT- "3 2000 Mr. Ryan Fike Bennett Development 9 Lake Bellevue Drive,Suite 100=A` Bellevue, WA 98005 SUBJECT: Heritage Renton Hill E Project No LUA-00-053,PP,ECF Dear Mr. Fike>. This.letter is written on behalf of the EnvironmpRta[A.evjow•Committee (ERC) and is.to advise you that they:have- completed their revi e pfoject ERC, on October 1.7, 2000; issued a j threshold Determination of Noll•Si ica i i ted inrith'Mi i ion :Measures See the .enclosed �� 'c;_�� 1 .,5#fit .1 , _ .- - r. •,. M�tigafion Measuresdocurrien� Nip .Appeals of the environmental fern must be;filed to cs before 5 QO PM November.6t,. -2000 :Appeals must be filed n• ite g ogether tti the:require $7V. application fee<with Hearing' txaminer, City & Renton;`-10 5 .S G a Wart, f " WA 98055,- peals to the Examiner are .. governed by City of.Renton 11unicipal rode S.ecti on -8?�10 Additional infofmafion regarding the appeal: • process may be obtained frome a tor��C er . r,A .ice; 425}43 ' S10 A Public Hearing will be hel by the Refitb earing miner, this„re0ular meet in the Council Chambers on the seventhfloa of C tlall, tn' embe ; , 200fat 9 00 AM ao consider the.proposed Preliminary The a lican `vr;reresentatiVe s of the applicant is re wired to be- resent at the public tY PP P q O PP 4• P P hearing A copy of the staff report w� tie ail d to,you one weekcb,�, fore a hearing` If the Environmental Qeterininabon is appealed,the ap I eird�as.paro is, earing _ - ':' -' L -'-fir ? ' - at _ ' U d'$ '- ► 'N,,y;`:N 4. w j -i• ttom�,, �.. • >.":... rvThe I) It,will assist pia i�ni or::'ic�plem on ofi#your p ojet t and enable�igtJ to =' uz ";clari : iesir ' =1epPealnghsmexercise you e a bons -or t le a ication of the o -For the.Envlroninental.Review'Conimittee f .it '.f v.' y st .4<- 'f t" Y'>' Y .z.. ,i.• ,,s(`-'•.>:'i j-. J. ••Y:"':•1..;;t+•:,.'^nP•': .}.t.. 1;!s::;:;-.1•wJ:' (j/.y'',i� yL.��•'4,,,.•, Rentonc�ioolistnc�t#40314wners . Parties of record x s xt'enclosure : ! y 0 •. E"cy' s' ir r� ?YY r •� ytr.n ` r.i:i �.�""! '". K b.s. x H ,I �., 1 ��: 4' ' �, ' iw c ow + w �t > ,.�`t -K•_0.... p+"FaAndi r �h r r.• 5 ({ )t! • t' rl ak �'tf !� # T >4i'�^ , 'S s i+�. r ''r ''� : rt st ifr* .lx - '4..'. � 0. f _ r •,;.tom i ,• c � -�,x n-,�,.. i r� -_ � a • rr:,7 �t�E� ..'K••�;"'�` �'' '+S,:rr{f ,'' t -.4«.�'' s't. n »'t' ..Y'L 'y l �"rl 'ti'l•.�i! )r yaf• V' t rt 't t ,.; tt3,s ,kn ::Y t.rl - �,•,.'> ',, �t;i i:'r ^''� :+r. ',�4.5`•. ,3,f Vet Y• ; r�•' .r .t�'.�.4,flf'i'.r^�iY4r,f .i . "t:< i e '.Yx r: ',r; fy .t y.•�.- r C - .r _! - •i t k-f eNtp .• -�. �. �?`� ,,. '�i..�'.'tf"G..�. .� Y$ 1.-t�i�.c� ^t:-�`�- r'3+r { '' .'r"'.tfz•.�i,t ° rJUx a,��k;! ,�' •-'M/ i �+ F����yy�,�T''jji'F'•��'• ( �-, � t `y° Y�4'•�. ~t'.t.}.. ,1 ,�i .ran i .�' ..r .�- � ';� x e+ x`-. ; �.. �.j t. >i t.,C�_�F ik4 . K.'r„Y�- '"l+r,�t ... � a�v� ��aS'!t!.`;y��Ck ,. rY�<(hY'i'. `� r {'sdv�1�''t'Y-- „ 9l'•�� ���'�F >.flt+u/- i�x J ,} .'`ey,1 h•'. +ph , �- .� �•. .i_ 3 �; i !,'}'-fdr' is bt.�� L y � -,� * �� Y- •a.4 - t .- r'3 s {% 4r.. c ,.' � d .• ,Y ff>:.,`x � .;yct ''� Y e. s' 145 South GradyVay Re -WashuigtonT9805�5 s. . . - - ®This paper contains 50%recycled material,20%post consimter ' CITY OF RENTON DETERMINATION OF NON-SIGNIFICANCE (MITIGATED) MITIGATION MEASURES APPLICATION NO(S): LUA-00-053,PP,ECF APPLICANT: Bennett Development PROJECT NAME: Heritage Renton Hill DESCRIPTION OF PROPOSAL: The applicant proposes division of a 10.35 acre property, by means of the preliminary plat process, into 57 lots suitable for single family residential development. The property is zoned Residential.8 (R-8), which allows residential development of.between 5.0 and 8.0 dwelling units per net acre (du/a). The proposed density for this project would be 6.8 du/a... .Lot sizes'. would:range from 4,504 to 8,318 square feet each. The minimum lot size in the R-8 Zone is 4500 sf' The applicant has requested a modification of street standards to allow public street tight-of-way widths of, 42' (instead of 50').;The.proposed project.is subjeect o review.py the City of Renton Environmental Review Committee..:A public.hearing before the CiofyR tors t`1�ar Examiner will also be required } ; s j t: ; r,l Y S, .1� ♦ 4jrt{ `la t 1 .:�y r 1^ LOCATION OF PROPOSAL > ht sects of Beaco E,S 7"-ZWrt"and S 77`Street MITIGATION MEASURES: ; N, .. y�, - > to "•^rtx � + ♦ Tfi 1 `The applicant shall inst l asittf rice alo the. o slo a ' rine er,of the area that is to be r P disturbed.:_:The*silt :fen a shall b'e it place g eMP = earing and;gra ing-is -initiated;.'and shall be constructed in conformance with the s ectficatior s_pr. stinted in the King County.•SurfaCe'Water •' Design Manual (KCSW[ ) t his uired ud the constructi n of both off--site and on-site ,improvements was well s buiidin c� s 2 Shallow drainage swales hall be construpte Ito int t su ace wa`te flow and ro ute the flow'awayr from the construction are,a.to agstabilized discharge.point. ege tion*growth shall be established in the ditch by seeding or placing so Depending on site gra�l0s; m be.necessary to line.the}ditch with rock to protect the ditclFi o eq s or and to red 'flo rite he design and construction of , drainage;,swales shalt cont'o s ecificat� n fires of in, the :`most recentlCC.WDtV►. " ' r.Temporary pipe;systems"cars a s ,�rs . ioiv_ st . ' acros's ahe site ;These inesures A�k. will be required_.during the cons ' i� o ff-s and ate irriprovenients,-asrellz' $iuilding t,yEq� ` ` ' _ - - - xr. .'r'.� - riG_�).t:`^r;a Si'e%�-'sr'r%;'sY':•-r;..; £f,�`.. Piyr:.. COnstlUCtlOrf. -fif:.. d F. - 6`•„t' ,�"�}irt € ..tn FF' - , _ .fir°.• � r �i_..r,.F•� ��r c The project contractor shall perform daily review..and maintenance Qf all erosion and sedimentafoh control Fnbasure�at the site during the consttucfiott of bofh bff- andron-site improvemeflts,as veil i i ' as building construction. is ;= =4. Weekly reports orjthe.'status and.Condition bf the erosion controt plan with any mniendations v> 4•;-max; revision to maintenance schedules or-installation_ihi ll be submitted ilia prpJeb�. z;.•:....;:x of Record to'the'Public:Works.;lnspector for`the`constructto�-of the'civil imp nVertients�f fhgplat. . . a' Certification of the installation; maintenance and proper remb4ail of the erosion Control q'pilities sha11' z be required prior to recording of the plat p .; ._ `- i - ., .,` - j �R f .r ti {, T • q \}'C f' � � CY ttj .. 5 The a IicaMsliall a the a licable Trans ortation .Mite abort Fee of the,' ' pP P. Y:, t?P P g rate�#.$7,5 Per .aoh s 9. Y P p ;I g Y p P ": new average.weekday trip attributable to the, ro act,estimated to be 9.55 avers a weef�da to s er :new single family lot:The:Transportation Mitigation Fee Is due prior t' the recording rapplipant shall. ay tlte�appropriate,Fire Mitigation Fee t a fat „$4$$;�0 g Yea F `e -�Aingig L - r� amity 1Qf created Cry the proposed pfiati}'fiabfee, sue rlo }fide eCordiri ,f tttl3; is �'+a•a4;,(a° i �„• S :Ttir.'4 x.;V-y �.,s -w•i N(; '�lj, ^r .a:'f' - . sf 7N�L{xr_^�K�tiS '�k. YY .�'h4t�4 .yjt aft' �' ,•,t y -r h ,<'. F. ,''^"ri ,,. .. TT .. - '. r. •t',t+ + • }`< .t r} y. r - t. < 'r _ �?x r { 'i ' � i,�•+Y+.._«°t. - X � = > � i'..' - ; �t - R �Yy # '�.`,•hN2C''itT� s t ht_ ,t � a .��.r Sti t l _ � ♦.... `. 1}' I'is ? - A ♦ 3, h a•�' +•y: ✓ kT f >.7 '. =_ t w� r'.�$-7 Ss _ r , �✓ L < r, 3 z aF + x fit• ar a.` t {. r x ...rir -- �.ty �r 3. G*41 T-lt- r' i.,.=.r •t,3.t� .,. 1� -r� • r =fiti ,fi - t+'ti•�` -. �- nt'x,�S�.t L T & •t'f '`. tia- t. _ '_{ '` � r "tt`'a .� •r . ti-..c Jr -: �.y t .. � �..�Yt ._J'tis�# +•Fir�Su `�' �i�' err-Ss - }�'tf•x _:.� t; _ r A s � s .:c +L a'�aaV'. _ s•�Mz° ��i ... - <:i i r- �i-'.�J'. •Y^ v � f irk( - • Heritage Renton Hill LUA-00-053,PP,ECF Mitigation Measures (continued) Page 2 of 2 7. The applicant shall pay the Parks Mitigation Fee at the rate of $530.76 per each new single family residential lot. The fee is due prior to the recording of the plat. 8. The applicant shall follow the recommendations of the geotechnical engineers, Geotech Consultants, Inc., (report dated September 14, 1999), as they pertain to site development and building construction. 9. A note shall be added to the face of the plat, prior to recording, stating that a known potential for ground subsidence exists in the area and that building plans shall be designed in consultation with a structural engineer and shall conform to the recommendations of the Geotech Consultants, Inc., as found in their report dated September.14, 1999. 10. The rear setback at the lot locatedin the northwest comer of the property (Lot 35 as shown on the plan dated 8/31/00) shall be twenty-five feet. 'A note-shall be placed on the title of the lot prohibiting building construction within twenty-five feet apd _clearing within ten feet of.the rear,property line, as shown on the revised plan submitted b the 'I'_Gn`t andAated,8/31/00� _ :11 The applicant shall ensure thae° s ctior� ebns and disca,Vd d items are excavated.from the site = and construction is'ceased: med ately, ollowed by obf icati0 the-City_,of.Renton,bevelopment -Services Division within 24 ours,-s ould" azardous matenal lie'd s vered during aid removal 12 The Construction TrafficJCo troljplan shal include a condition hat nstruction vehicles in" excess 26,000 gvw,-associated with the project two e prohibited from'opAting on Renton Hill-during am . and pm peak traffic hours-as identified nl erreport, "f eritage Renton Hill Preliminary Plat Arnold ' Property Traffic ImpactAnalOsis'Addeendtfrrli 0: 2 by TransportationtPlanning & Engineering, Inc., �j'. dated September 11,20000 '" ; -- `- 13 The applicant shall obtain an access=pem7i n order�3o uses _e Seatt Public Utilities "Cedar River Pipeline Easement"for a secondarjk emergency only access ;. •(. ..•.. _ is ,y. _ .�I J — - j.y. .:t•.t .t JG .J_1 - _ Ida �• !t d.^_�4�. iJ ri L -4 fief +A_' _diK'1'S .ti.T •v' _ _ :1f: ii•' j.. _ i= • f r 1 C` �y_ t::?. .•e .r L.0 x s 4. rr y_ck w s - C 3• :-.,.w:; ..t.+ '�.e•9 ♦ _ t! 'le, s .p.-'tdp, _," s s -�7�` j ' -'�'i ..v J r+ y _. a s 2i v s r ' lM L;' n * " t •t,av'i°?;ya ,.4'• . `"1 1,i "A4'iYa.-$ i :�+' jp •f'.o J" 'YS'' �: !T 1 0. _f'•f. a t!$f' I �i : t �.y�. 10 �f !t" '+ T=' � 4+ .':mrJz: {. yr. ? fit. -•�;, •,. .:r- j f ::! -t + t/ ti• ,prgativ'•3',r ? a r'�� ti1m C. c t .rr.�r y vw•' r-�- � -_I 1. .� "y' •i; ?.j F a 1: /{ X� n �L 't i i' J i. £ ^C 'f e x I ,,� �'� (i y,, . h -jD r i i • �y.': v. 't•t .a .4 T 'fe r Jr4 [` c,`3�iq,e!/e''r4t! ^.'•S S -fit- F:{, r k t"t !�y . f4„'3•TrtY1. Is'i t t .a. t,^" 'p�, A. tq..: ^.i- - / }. ;L! WJ•)V Lk -sJ c. f J k k'$ t� ,1^.lamt yy* tJ'. y'` Si +`:t t� r'. • CITY OF RENTON DETERMINATION OF NON-SIGNIFICANCE (MITIGATED) ADVISORY NOTES APPLICATION NO(S): LUA-00-053,PP,ECF APPLICANT: Bennett Development PROJECT NAME: Heritage Renton Hill DESCRIPTION`OF PROPOSAL: The applicant proposes division of a 10.35 acre property, .by means of the preliminary plat process, into 57 lots suitable for single family residential development:. The property is zoned Residential 8 (R-8); which allows residential development-of between 5.0 and 8:0 ' dwelling units per net acre (du/a). The proposed.density for this project would be 6.8 du/a. Lot sizes- would range from 4,504'to 8,318 square feet-each. The minimum lot sizein.the R-8 Zone is`4,500 sf The applicant has requested a modification of.street standards to allow public street right-of-way widths of 42'(instead of 50).-The proposed project is subject to review by the City of Renton Environmental,Review Committee A public hearing before the Ci �f'e*n o e°` nq0 Examiner will also be required.'._ E,S 7"'Court,and S 7 'Street LOCATION OF PROPOSAL Int echo of Beaco a s Adyisary Notes fo Applicant: ,, T , `1f r { y^ The`fol/owing notes are suppleme�ta �n formabo - rov'ded n co7ijuncbon with tffe envfronmentaf determination., Because these notes area pro e -a inf rmaion onl};they are'not subject to_.the- appeal process for environmental determ�natro s :'Plan Review—Sanitary Seer 1 There is an existing 8' sewers}tnainJin SE 7"' Court, ad*acen o4kie orth side of the proposed:plat The new project can'be served b� e.e ding an 8" sewerr airsJro this existing main through:the proposed subdivision 2 The noncePtttal sanitary;sewer,, ri�sho dra submitted'for ahe'format applicationr� +_• ;appears to`be in order: 3.".A sewer deariout will need to be located five feet but buildings; • .-4_ Separate.side sewer -will be required for each parcel (no dual sewers). Side sewer lines must have 2 percent slope. ust.:com` I �with�tlie C•� of Renton Oiaftin� Sta err:^ 'Y:V .All-util' .p1an��Yn p.y ►ty .9 `±6 Show finished floor elevations on the sewer construction plan sheet.' ;.j the sewer main will be.r uir „� Ttie vertical profle of.. eq The ro'e is located in'A uifer rotection Area Zone '#8. P. 1 ct. q P ` 9 Any new sewer mains are to be separated.from water lines*a minimum of;10 feet' There is a-7 5 :} {jypyr " � `{foot]mlnirrium( eparaftion frbri other:uttl�tes` 1.Q" - ,'j ",' •j'?`F n-�(1 "i.'S.!'�¢ L.y.9 rt S''`••5�-�;A;_' J ....kk. l >'1 l WS'a.G �Sp7r'�" 'F. , -t'• g+ l '' �).l 1k Y ..? w^/Y14 bJ Z.�`.� •I•• r; l�yCE �d �4iK'''� '* r t -E .sM, r tr 3. 0 r ♦ f `x r%;'�J'+ - R �r x s rrt. rr`Tl !r-.l d ,r' t - _ :C.Y.; -:K _E 7, T t �a„•e,�. i{'!st �'3�� r.a�a r - .Fgj f*`"Tiyiy'`ltti4•�;�� --�r- 'y E 4 . ark !..• J T!{ .1 y `, t �. .,,,.i.,i� .,. ' ... � ' }.. f"' Y i RJc�n s.' y T t a^�s a+".,7_` '`s s'i-:+:�. t xq.A.�r3 F•3 ,; t .�t,F n T sf✓J'.7 y 3 i . '{ , J r t j * �" .f "3�,{",Y,d. .,f, Y !-fit Heritage Renton Hill LUA-00-053,PP,ECF Advisory Notes(continued) Page 2 of 2 • 10. Sewer Development Charges of$585.00 per single family residence will be required for this plat. The fee for this project would be $16,380.00. This fee must be paid prior to issuance of the construction permit for the preliminary plate Plan Review—Water 1. There is an existing 6" water main in Jones Avenue S, an 8" water main in SE 7`h Court, and an 8" water main stub to the north boundary of this parcel. 2. The proposed project is located in the 490 foot water pressure zone. Static water pressure will range from approximately 40 psi at elevation 395 feet to 55 psi at elevation 360 feet. 3. Any new construction must have a fire hydrant capable of delivering a minimum of 1,000 GPM fire flow and shall be located.within 300 feet of the structure. This distance is.measure along a travel route. Additional fire hydrants will be required as part of this project to meet this.criteria. 4. The.water main must be a looped-system with two separate feeds. The conceptual utility plan_needs' to be modified to show the second feed to the existing 6"water main in Jones Avenue S.. 5 : Installation of 8°water mains In the interior'stree s p ,at to serve'the domestic water meters and fife hydrants are"required 6 Connection to the 8"stub alo th r `orth-pt perty4in s r ulred tee plan VN 2038). 7. .Connection to the existing 6":Yvatet ainones Avenue is`e Ire see.Nan W=1.156 . The water conce tual itili. p ty Plan halbe�ev'§e�d is how>this co section •, 8. Water System.Development charg s o $$50-0Openewsingle amilylowill be required for this: The charge for this plan woutd be _ 8 45 Obi, #I syfe ue paid prig to.Issuance of the construction . permit for the.prellminar tat. t Plan.Review—Stormwater Drainage 1 ; A,conceptual drainage plan: ndrefn 9e report was sub tfte ,�rlt� preliminary plat application for this protect and appears to b r 7 2 Diavirings submitted to the City err on`are 4 I ich sheets The infoimation - ' ertaiolhd to the:trlty of Renton thou tie mo ed fro a b7odc bf the sheets submitted ti r 3. Before any construction or development activity occurs,a pre-construction meeting•must be held with r they City of Renton Development Services Divisions,Construction.ServlcesJ425 277-5570) 4:. :Tile City of Renton.retains-the.-nght to restrict:the,timin `of...land;idearin `and.tree'cuttin :activitiesao .-• s ecific-dates and/or seasons when such rest'rictfons:ma be ecessa g for the ubliC health safe - P Y n ry ,P ty; and welfete,or for the protection+�f•the environment:- �:' '- 5 Suiface vVater System bevelopmen#charges of$385 per new single family lot will be required for this" plat The fee_for this project,would be $21,945.00..,:This fee must be paid:prior to Issuance of the ;construction permit for the prellthloary plat Plan'Review';Transportation and Street Improvements ::1 ',.-All electrical and communication facilities to be underground behind the sidewalk If right-of-way space is trot available;then In`a utility easement..-Construction of these franchise utilities must be .«[lspected and approved�y a C of: e�ton publlcwQrk$lnspector prior,to recording of the plat., y , 4 + .� _ ''r *A '>u k<icl Jt �, �" '(.S. 1 *A 'y F s •! t .YY<- l'`>`f.:g-• a`-vt-t`, t 2 t Streets over BOO feet in,length ire required to havo two means of access = :.f F '�� ? � :Y't ••.J- < s as� r a?"{ t iY7 s s ; tiC'� i r - _ t. x• ADVISORYNOTES :'' - Heritage Renton Hill LUA-00-053,PP,ECF Advisory Notes(continued) Page 3 of 3 • 3. Street lighting is_required to meet City standards. Minimum lighting level is 6:1 uniformity ratio and 0.2 foot candle level. The street lighting conduit to be located under the sidewalk. 4. The minimum right-of-way width is 42 feet(modified from street standard width of 50 feet). 5. The cul-de-sac is required to have a minimum pavement radius of 45 feet and right-of-way radius of 55 feet. 6. A 5 foot sidewalk at the curb is required 7. Payment of a Transportation Mitigation fee of$75 per new average weekday trip, estimated at 9.55 new trips per single family lot,Will be required prior to recording of the plat.- It has been estimated that this 57 lot plat would result in approximately 544.35 additional average (weekday)trips. The Transportation Mitigation Fee would be$40,826.25. Plan Review—General 1. Al required utility,drainage,and street improvements will require separate plan submittals prepared according to City of Renton drafting standards by'a registered Civil Engineer. 2. The construction permitapplication(s)must include an itemized cost estimate for these _ improvements 3 The fee for review and inspectiortfthese mp e'ments is 5 percent of the first$100,000 of the estimated construction costs;p ercent ofManA!hg over$�O,OOb but.less than $200,000;and,3 percent of anything over$20 ;000 Half.of°tiffs fee mustibe paid upo application fors' ruction permits(preliminaryplat im rovemenjs�, and the remainder w e. e construction permit is issued. There may be'additional f e fo�water"service ated.expenses • s ; 4. An easement that meetsCity standards for_ing ss egres. , an utilities shall be provided by the applicant to the property abutting the:east,pro a #lour dary at a point within 200 feet of the northeast ` property comer of the propose'p at. ' . Parks Department Reviewer , - _ 1. Payment,of a Parks Mitigation fee of$530.76 for each new single-Jamily lot will be required prior,to . recording of the.plat. The Perks fee will be$30,253.32. y_ `Building Department Review - ` 1 [7Aino111M v- krnits will be required: Fire PreVent`ion Rep a`rtment.Rev iew - :. ' 1 Afire hydrarAwith 1000 GPM fire flow is required within 300.feet of all new single family structures.`If the building square footage exceeds 3600 square feet in area, the minimum fire flow increases to.': 1500 GPM and requires two hydrants within 300 feet of the structure. 2 Prowde a 20 foot paved secondary emergency accessfrom tire cul-de-sac within the develo merit#o pp the Seattle.Public,Utilities-Cedar River Pipeline Easement (Beacon Way SE). This.would :be an . emergency access only and can be gated or chained.' - 3 Al tiu�dng addresses shall be visible from a public street. 4::' A`Fire.Mitigation fee'of $488 is required for all new single family lots. Payment is required prior to recording of the plat. ,The Fire Mitigation fee for the proposed project would be$27,816.00. ' x Property Services Department#teview $1 Comments will be provided under,separate cover. ADOSORYNOTES Heritage Renton Hill LUA-00-053,PP,ECF Advisory Notes(continued) Page 4 of 4 • Development Services Department Review 1. The site is designated Residential Single Family in the Comprehensive Plan. 2. The property is zoned Residential 8 (R-8). 3. Densities allowed in the R-8 Zone are 5.0 dwelling units per net acre (du/a) minimum and 8.0 du/a maximum. 4. Minimum lot size in the.R-8 Zone is 4500 sf, with minimum width of 50 for interior lots,and 60 for comer lots. The minimum permitted lot depth is 65 feet. Lot dimensions must be shown on the final site plan demonstrating that all lots meet these minimums. 5. Heights of buildings in the R-8 Zone are limited to 2 stories, or 30 feet. 6. Required setbacks in the R-8 Zone are 15 feet for houses and 20 feet for attached garages which access from the front when houses front streets created after September 1 1995,-20 foot rear yard' setbacks; 5 foot side yard setbacks for interior lots and 15 feet s.ideyard setbacks for comer lots..All setbacks are minimums. Setback dimensios�should be shown on the construction drawings, but % setback lines must be removed prior to,recor, mg t ie linalplat. .00 7. The maximum building coverage-in the R-8 Zo6d,is 35 pe cent for lots over 5,000 sf or 50 percent for lots 5,000 sf or less. < NS 8. Dead.end streets cannot exceed 700 feet in length, measured fr lm Me edge of the connecting street to the end of the cul-de sac. x-,} • 9. Retaining walls in excess of four )feet �re_'eninee ed drawings a d a separate buildin 9 t g P g Permit.. 10. Construction easements, obtainetd from .a uttW roperty .owners" �'tay be necessary, prior to construction of retaining walls on or nearprerty fines.,These agreements:must-include protection measures for (or permission to ppotentially+damage emove),trees located on abutting properties within 20 feet of the property line 11. The applicant shall draft nd .reco d a: aintenancd 4drf- ertie or :establish:.,a :Homeowners' Association for the maintenan oftallxcom on1mprover�ents ss and utility easements,:rights- Association stormwater facilities d+raft qqi a iidcu en hal .e submitted:to the:City of Renton for:.: . review and approval by the City Attoin rior�oe rordi g f the preliminary plat; 12.` Performance; Standards :for' Land Development Per its (RMG 4.4-130K), including -Protection Measures During`Construction! (RMC 4-�4-130K7).relating to trees,shall be folloinred.by the applicant; The,applicant shall adhere. o the definition of!." a found in RMG 4-1.1-20D,'drip line as`found;in RMC:4-11-040,and the measurement of trees as.found.in RMC.4 11030 13. The WasFiington State:Departriient of Natural Resources may ireguino a:Forest Practices Permit for the conversion:of timber land to another use 14: The applicant should contact Paul Alexander of The King County Department of Transportation; Metro Transportation, Metro:TransitRoute:F.acilities at206-684-1599, regarding Metro's requirements for potential_transit service in the area(no service is currently available to Renton'Hill) ` ADVISORYNOTES 2.4 SUMMARY OF HEARING EXAMINER'S CONDITIONS • Heritage Renton Hill Plat City of Renton File Nos.LUA00-149,AAD Note: The following outline summarizes the Hearing Examiner's conditions for the preliminary plat approval,in italics,followed by a narrative response explaining how the Hearing Examiner's conditions have been met or will be met for this project. 1. The plat should be reduced from 57 to 50 single family lots with a density of 6.02 dwelling units per acre. This falls within the permissible range of 5 to 8 dwelling units per acre. Response: The final layout has been prepared for 50 lots. The final layout is nearly identical to the preliminary plat map except for the reduction in lot count and the elimination of some landscape tracts. 2. The applicant shall comply with the conditions imposed by the ERC. Response: Completed. See separate responses to ERC conditions in Section 2.5 of this TIR. 3. The plat shall contain language acceptable to the City Attorney regarding the recreational and open space respectively and precluding development of them. Response: Acknowledged as a final plat item. 4. All landscape tract areas,with the exception of the 5,402 sf tract located at the development entry, the 3,042 sf private 'park", and the landscape area abutting the stormwater tract, shall be incorporated into lots already proposed within the plat. No additional building lots are to be created. A revised plan shall be submitted to the Development Services Division prior to receiving construction permits. Response: Completed. The final layout is nearly identical to the preliminary plat map except for the reduction to 50 lots and eliminating the landscape tract areas described by this condition. 5. Commonly held open space areas shall be enhanced,prior to occupancy, with landscaping including mixed deciduous and evergreen trees and plantings of native shrubs and groundcover. The applicant shall submit a landscape plan to the Development Services Department for approval. Response: Acknowledged as final plat item. The landscape plans will be completed for approval prior to final plat approval. 6. A Hold Harmless Agreement shall be recorded that indemnifies the City ofRenton from any damage resulting from subsidence that may occur due to previous subsurface mining activities. Response: Acknowledged as a final plat item. 7797.006[RJA/jss/ca] 7. The applicant will have to secure in writing permission to use the Seattle pipeline road for emergency access. Response: It is our understanding that the agreement has been written by the City of Seattle and is currently on file with the City of Renton awaiting approval by the Mayor. 8. The homeowners would be required to maintain the open space tracts at the entrance and the park area. Response: Acknowledged as a final plat item. • 7797.006[RJA/jss/ca] • • • I 2.5 SUMMARY OF SEPA CONDITIONS AND ERC ADVISORY NOTES • Heritage Renton Hill Plat City of Renton Project No.LUA00-053,PP,ECF Note: The following outline provides the City of Renton's Determination of Non-Significance Mitigation Measures in italics, followed by a narrative response explaining how the mitigation measure will be addressed. Also, following the SEPA mitigation measures is each of the Advisory Notes in italics, followed by a narrative response indicating how the comment is addressed. 1. The applicant shall install a silt fence along the downslope perimeter of the area that is to be disturbed. The silt fence shall be in place before clearing and grading is initiated, and shall be constructed in conformance with the specifications presented in the King County Surface Water Design Manual(KCSWDM). Response: This condition will be satisfied with the approval of the grading and erosion control plan. A silt fence has been located along the downslope portions of the property boundary. 2. Shallow drainage swales shall be constructed to intercept surface water flow and route the flow away from the construction area to a stabilized discharge point. Vegetation growth shall be established in the ditch by seeding or placing sod. Depending on site grades, it may be necessary to line the ditch with rock to protect the ditch from erosion and to reduce flow rates. The design and construction of drainage swales shall conform to the specifications presented in the most recent KCSWDM. Temporary pipe systems can also be used to convey stormwater across the site. These measures will be required during the construction of both off-site and on-site improvements, as well as building construction. Response: This condition will be satisfied with the approval of the grading and erosion control plan. Temporary drainage ditches/swales with rock check dams have been designed to collect and convey drainage. 3. The project contractor shall perform daily review and maintenance of all erosion and sedimentation control measures at the site during the construction of both off-site and on- site improvements, as well as building construction. Response: This note has been placed on the grading and erosion control plan, Sheet TL 4. Weekly reports on the status and condition of the erosion control plan with any recommendations of change or revision to maintenance schedules or installation shall be submitted by the project Engineer of Record to the Public Works Inspector for the construction of the civil improvements of the plat. Certification of the installation, maintenance and proper removal of the erosion control facilities shall be required prior to recording of the plat. Response: This note has been placed on the grading and erosion control plan, Sheet TL 7797.006[RJA/jss/ca] 5. The applicant shall pay the applicable Transportation Mitigation Fee at the rate of$75.00 •' per each new average weekday trip attributable to the project,estimated to be 9.55 average weekday trips per new single family lot. The Transportation Mitigation Fee is due prior to the recording of the plat. Response: Acknowledged as a final plat item. 6. The applicant shall pay the appropriate Fire Mitigation Fee at a rate of$488.00 per each new single family lot created by the proposed plat. The fee is due prior to the recording of the plat. Response: Acknowledged as a final plat item. 7. The applicant shall pay the Parks Mitigation Fee at the rate of$530.76 per each new single family residential lot. The fee is due prior to the recording of the plat. Response: Acknowledged as a final plat item. 8. The applicant shall follow the recommendations of the geotechnical engineers, Geotech Consultants,Inc., (report dated September 14, 1999),as the pertain to site development and building construction. Response: This note has been placed on the grading and erosion control plan, Sheet T1. 9. A note shall be added to the face of the plat, prior to recording, stating that a known potential forground subsidence exists in the area and that buildingplans shall be designed in consultation with a structural engineer and shall conform to the recommendations of the Geotech Consultants,Inc., as found in their report dated September 14, 1999. Response: Acknowledged as a final plat item. 10. The rear setback at the lot located in the northwest corner of the property(Lot 35 as shown on the plan dated 8131100)shall be twenty-five feet. A note shall be placed on the title of the lot prohibiting building construction within twenty-five feet and clearing within ten feet ofthe rearproperty line,as shown on the revised plan submitted by the applicant and dated 8131100. Response: This 25-foot setback is shown on the horizontal control plan,Sheet RI,as is the clearing limitation on the rear 10 feet of Lot 32 (please note that Lot 35 referenced in the condition has been renumbered to be Lot 32 as a result of the reduction from 57 lots down to 50 lots. 11. The applicant shall ensure that all construction debris and discarded item are excavated from the site and construction is ceased immediately,followed by notification of the City of Renton Development Serviced Division within 24 hours, should hazardous material be discovered during said removal. Response: This note has been placed on the grading and erosion control plan, Sheet T1. 7797.006[RJA/jsslca] 12. The Construction Traffic Control Plan shall include a condition that construction vehicles • in excess 26,000 gvw, associated with the project, would be prohibited from operating on Renton Hill during am and pm peak traffic hours as identified in the report, "Heritage Renton Hill Preliminary Plat Arnold Property Tragic Impact Analysis Addendum No 2 ' by Transportation Planning&Engineering Inc., dated September 11, 2000. Response: This note has been placed on the grading and erosion control plan, Sheet T1. 13. The applicant shall obtain an access permit in order to use the Seattle Public Utilities "Cedar River Pipeline Easement"for a secondary, emergency only access. Response: Acknowledged. The City of Seattle has prepared the agreement and it is on file with the City of Renton awaiting approval by the Mayor. i 7797.006[RJA/jss/ca] • Advisory Notes to Applicant.- The following notes are supplemental information provided in conjunction with the environmental determination. Because these notes are provided as information only,they are not subject to the appeal process for environmental determinations. Plan Review-Sanitary Sewer 1. There is an existing 8"sewer main in SE 7th Court, adjacent to the north side of the proposed plat. The new project can be served by extending an 8"sewer main from this existing main through the proposed subdivision. Response: The final sanitary sewer design connects to the existing 8-inch PVC sanitary sewer main stub that was built to the property by the River Ridge plat. 2. The conceptual sanitary sewer main shown on the drawing submitted for the formal application appears to be in order. Response: Acknowledged. 3. A sewer cleanout will need to be located five feet out from buildings. Response: Acknowledged as a residential building permit item. The plat will stub side sewers 10 feet into each lot. 4. Separate side sewers will be required for each parcel(no dual sewers). Side sewer lines must have a 2 percent slope. Response: Each lot has been provided with an individual 6-inch side sewer stubbed 10 feet into the lot. S. All utility plans must comply with the City of Renton Drafting Standards. Response: Completed. 6. Show finished floor elevations on the sewer construction plan sheet. Response: The sewer plan shows lot pad elevations. The finish floor elevations will be determined at the time of individual house construction and will probably be approximately 1.0 foot higher than the lot pad elevation that will be graded with the plat construction. 7. The vertical profile of the sewer main will be required. Response: Completed on Sheets S2 and S3. 8. The project is located in Aquifer Protection Area Zone 2. 7797.006[RJA/jss/ca] Response: Acknowledged. Sanitary sewer is provided so that the aquifer is not impacted •. by any septic systems. 9. Any new sewer mains are to be separated from water lines by a minimum of 10 feet. There is a 7.5 foot minimum separation from other utilities. Response: Completed. We have designed the standard separation between water and sanitary sewer at 12 feet,as shown on Sheets W 1 and S 1,and in no case is the sewer closer than 10 feet separation as required. 10. Sewer Development Charges of$585.00persinglefamily residence willbe requiredforthis plat. The fee for this project would be$16,380.00. This fee must be paid prior to issuance of the construction permit for the preliminary plat. Response: Acknowledged as a final plat item. Plan Review- Water 1. There is an existing 6"water main in Jones Avenue S, an 8"water main in SE 7th Court, and an 8"water main stub to the north boundary of this parcel. Response: Acknowledged and shown on Sheet W 1. 2. The proposed project is located in the 490 foot water pressure zone. Static water pressure will range from approximately 40 psi at elevation 395 feet to 55 psi at elevation 360 feet. Response: Acknowledged. 3. Any new construction must have afire hydrant capable of delivering a minimum of 1,000 GPM fire flow and shall be located within 300 feet of the structure. This distance is measure along a travel route. Additional fire hydrants will be required as part of this project to meet this criteria. Response: The water plan, Sheet W 1,proposes three fire hydrants that comply with this spacing requirement. 4. The water main must be a looped system with two separate feeds. The conceptual utility plan needs to be modified to show the second feed to the existing 6"water main in Jones Avenue S. Response: The water plan, Sheet W1, proposes a water main loop connection to Jones Avenue South. It runs in an east/west direction approximately 140 feet south of S.E. 7th Court. 5. Installation of 8"water mains in the interior streets of the plat to serve the domestic water meters and fire hydrants are required. Response: Completed with 8-inch mains shown on the water plan, Sheet W 1. 7797.006[RJA/jss/ca] 6. Connection to the 8"stub along the north property line is required(see plan W-2038). • Response: Completed on the water plan, Sheet W l. 7. Connection to the existing 6"water main n Jones Avenue S is required(see plan W-1156). The water conceptual utility plan shall be revised to show this connection. Response: Completed on the water plan, Sheet W 1. 8. Water System Development charges of$850.00 per new single family lot will be required for this. The charge for this plan would be $48,450.00. This fee must be paid prior to issuance of the construction permit for the preliminary plat. Response: Acknowledged as a final plat item. Plan Review-Storm water Drainage 1. A conceptual drainage plan and drainage report was submitted with the preliminary plat application for this project and appears to be in order. Response: Acknowledged. 2. Drawings submitted to the City of Renton are to be on 22 inch x 34 inch sheets. The information pertaining to the City of Renton should be removed from the title block of the sheets submitted. Response: Completed. 3. Before any construction or development activity occurs, a pre-construction meeting must be held with the City ofRenton Development Services Division, Construction Services(425- 277-5570). Response: Acknowledged as a construction item. 4. The City of Renton retains the right to restrict the timing of land clearing and tree cutting activities to specific dates and/or seasons when such restrictions may be necessary for the public health, safety, and welfare, or for the protection of the environment. Response: Acknowledged. The applicant is requesting an early clearing and grading permit for approval of the grading and erosion control plan prior to approval of the road and utility plans. 5. Surface Water System Development charges of$385 per new single family lot will be required for this plat. The fee for this project would be$21,945.00. This fee must be paid prior to issuance of the construction permit for the preliminary plat. Response: Acknowledged as a final plat item. 7797.006[RJA/jss/ca] • Plan Review- Transportation and Street Improvements 1. All electrical and communication facilities to be underground behind the sidewalk. Ifright- of-way space is not available, then in a utility easement. Construction of these franchise utilities must be inspected and approved by a City of Renton public works inspector prior to recording of the plat. Response: Acknowledged. The horizontal control plan,Sheet R1,provides a 10-foot-wide utility easement across all lots adjacent to right-of-way for the underground power, telephone, natural gas, and cable television. The street lighting has been designed on Sheet R9 and provides underground power service to the street lights. 2. Streets over 700 feet in length are required to have two means of access. Response: Emergency access is provided over Tract D for connection to Beacon Way S.E. The final layout is identical to the approved preliminary plat layout for the roads. 3. Street lighting is required to meet City standards. Minimum lighting level is 6:1 uniformity ratio and 0.2 foot candle level. The street lighting conduit to be located under the sidewalk. Response: Completed. The street lighting design is on Sheets R9, R10, and R11. 4. The minimum right-of-way width is 42 feet(modified from street standard width of 50 feet). • Response: Completed. The road section is shown on Sheet R4 with 42 feet of right-of-way. 5. The cul-de-sac is required to have a minimum pavement radius of 45 feet and right-of-way radius of 55 feet. Response: The cul-de-sac has been designed with 50-foot radius at face-of-curb and 55-foot radius at right-of-way line. 6. A 5 foot sidewalk at the curb is required. Response: Completed. The road section on Sheet R4 shows that the 5-foot sidewalk width is provided between face-of-curb and back-of-sidewalk. 7. Payment ofa Transportation Mitigation fee of$75 per new average weekday trip,estimated at 9.55 new trips per single family lot, will be required prior to recording of the plat.It has been estimated that this 57lotplat would result in approximately 544.35 additional average (weekday)trips. The Transportation Mitigation Fee would be$40,826.25. Response: Acknowledged as a final plat item. Plan Review- General • 7797.006[RJA/jss/cal • 1. All required utility,drainage,and street improvements will require separateplan submittals prepared according to City of Renton drafting standards by a registered Civil Engineer. Response: Completed. The plans have been submitted to the City of Renton with separate plan sets for road, drainage,and street lights(R Sheets),water(W Sheets), sanitary sewer (S Sheets), and grading and erosion control (T Sheets). 2. The construction permit application(s) must include an itemized cost estimate for these improvements. Response: Completed. The permit application included the itemized cost estimate. 3. The fee for review and inspection of these improvements is 5 percent of the first$1000,000 of the estimated construction costs; 4 percent of anything over $100,000, but less than $200,000, and 3 percent of anything over $200,000. Half of this fee must be paid upon application for construction permit (preliminary plat improvements), and the remainder when the construction permit is issued. There maybe additional fees for water service related expenses. Response: Completed. The permit fee for the submittal has been paid. 4. An easement that meets City standards for ingress, egress, and utilities shall be provided by the applicant to the property abutting the east property boundary at a point with 200feet of the northeast property corner of the proposed plat. Response: Completed as shown on the horizontal control plan, Sheet R1. Parks Department Review 1. Payment ofa Parks Mitigation fee of$53076 for each new single family lot will be required prior to recording of the plat. The Parks fee will be$30,253.32. Response: Acknowledged as a final plat item. Building Department Review 1. Demolition permits will be required. Response: Not applicable. There are no existing buildings on the property. Fire Prevention Department Review 1. Afire hydrant with 1000 GPMfire flow is required within 300 feet of all new single family structures.Ifthe building square footage exceeds 3600 squarefeet in area,the minimum fire flow increases to 1500 GPM and requires two hydrants within 300 feet of the structure. Response: The water plan, Sheet W1,provides three fire hydrants that meet the spacing requirement and 8-inch water mains to convey the required fire flow. i 7797.006[RJA/jss/ca] • 2. Provide a 20 foot paved secondary emergency access from the cul-de-sac within the development to the Seattle Public Utilities Cedar River Pipeline Easement (Beacon Way SE). This would be an emergency access only and can be gated or chained. Response: Completed as shown on the road and drainage plan, Sheet R2, and the emergency access pavement section shown on Sheet R3. We have provided a gate at the west end of the tract along Beacon Way S.E. and a chain at the east end of the tract at the cul-de-sac. 3. All building addresses shall be visible from a public street. Response: Acknowledged as a building permit item. 4. A Fire Mitigation fee of$488 is required for all new single family lots. Payment is required prior to recording of the plat. The Fire Mitigation fee for the proposed project would be $27,816.00. Response: Acknowledged as a final plat item. Property Services Department Review 1. Comments will be provided under separate cover. Response: Acknowledged. • Development Services Department Review 1. The site is designated Residential Single Family in the Comprehensive Plan. Response: Acknowledged. 2. The property is zoned Residential 8(R-8). Response: Acknowledged. 3. Densities allowed in the R-8 Zone are 5.0 dwelling units per net acre(du/a)minimum and 8.0 du/a maximum. Response: Acknowledged. 4. Minimum lot size in the R-8 Zone is 4500 sf, with minimum width of 50 for interior lots and 60 for corner lots. The minimum permitted lot depth is 65 feet. Lot dimensions must be shown on the final site plan demonstrating that all lots meets these minimums. Response: All lots have been designed to exceed 4,500 square feet and meet a minimum width of 50 feet for interior lots and 60 feet for corner lots. All lots are much greater than i 7797.006[RJA/jss/ca] the minimum depth of 65 feet. The lot widths and areas are shown on the horizontal control • plan, Sheet R1. S. Heights of buildings in the R-8 zone are limited to 2 stories, or 30 feet. Response: Acknowledged as a residential building permit item. 6. Required setbacks in the R-8 Zone are I5 feet for houses and 20 feet for attached garages which access from the front when houses front streets created after September 1, 1995, 20 foot rear yard setbacks; 5 foot side yard setbacks for interior lots and 15 feet side yard setbacks for corner lots. All setbacks are minimums. Setback dimensions should be shown on the construction drawings,but setback lines must be removed prior to recording thefinal plat. Response: The required setbacks are shown on the horizontal control plan, Sheet R1. 7. The maximum building coverage in the R-8 Zone is 35 percent for lots over S, 000 sf or 50 percent for lots S,000 sf or less. Response: Acknowledged. For the drainage calculations,we have assumed the 50 percent maximum coverage for the buildings and an additional 20 percent impervious surface for driveways and patios to size the drainage facility. 8. Dead end streets cannot exceed 700 feet in length, measured from the edge of the connecting street to the end of the cul-de-sac. Response: Acknowledged. We have proposed Tract E as an emergency access connection from the end of the cul-de-sac to Beacon Way S.E. 9. Retaining walls in excess of four (4)feet require engineered drawings and a separate building permit. Response: Acknowledged. We have rockeries up to 6 feet in height along the east boundary of the project. 10. Construction easements obtained from abutting property owners may be necessary prior to construction of retaining walls on or near property lines. These agreements must include protection measures for(or permission to potentially damage or remove)trees located on abutting properties within 20 feet of the property line. Response: Not applicable. The project does not require construction easements from any abutting property owners. 11. The applicant shall draft and record a maintenance agreement or establish a Homeowners' Association for the maintenance ofall common improvements(access and utility easements, rights-of-way, and stormwater facilities). A draft of the document shall be submitted to the City of Renton for review and approval by the City Attorney prior to the recording of the preliminary plat. / 7797.006 RJA/jss/ca [ J ] •' Response: Acknowledged as a final plat item. 12. Performance Standards for Land Development Permits (RMC 4-4-130K), including "Protection Measures During Construction"(RMC 4-4-130K7)relating to trees,shall be followed by the applicant. The applicant shall adhere to the definition of"tree"a found in RMC-4-11-200, "drip line"as found in RMC 4-11-040, and the measurement of trees as found in RMC 4-11-030. Response: Not applicable. All trees on the property will be cleared for the small lot development. 13. The Washington State Department of Natural Resources may require a Forest Practices Permit for the conversion of timber land to another use. Response: Acknowledged as a construction permit item. We have sent a separate application for a FPA permit. 14. The applicant should contact Paul Alexander of The King County Department of Transportation, Metro Transportation, Metro Transit Route Facilities at 206-684-1599, regarding Metro's requirements for potential transit service in the area (no service is currently available to Renton Hill). Response: Acknowledged. We have sent a request to Metro Transit and verified that no • service is currently available to Renton Hill. • 7797.006[RJA/jss/cal � :"' 0 3.0 OFF-SITE ANALYSIS • A Preliminary Technical Information Report and Level 1 Downstream Analysis were prepared by Peterson Consulting Engineers,dated April 2000,for this project. The downstream analysis part of that report is contained in Section 3.1 ofthis TIR. We have reviewed the downstream analysis and completed a field verification at the time of final engineering design and found that conditions have not changed since the April 2000 report. The Heritage Renton Hill project will use an infiltration pond combined with individual lot rooftop infiltration systems to retain stormwater on site. The pond will be provided with an emergency overflow connection to the existing storm drainage system in Beacon Way S.E. Specifically, the pond emergency overflow will be piped to connect to existing City of Renton Catch Basin No. 17,E9-3 that is located at the northeast corner of the intersection of Beacon Way S.E.and S.E. 7th Court. This is a Type 1 Catch Basin that is 4.1 feet deep. From here,emergency overflow drainage is piped in a northwest direction along the easterly side of Beacon Way S.E. through a series of catch basins and 12-inch concrete pipes to the intersection of Beacon Way S.E.and High Avenue South to City of Renton Catch Basin No. 17,E84. Here,the drainage tightline flows north along the west side of High Avenue South through 12-inch concrete pipes to City of Renton Catch Basin No. 17,E8-6. From here, drainage flows through an 18-inch and then 16-inch HDPE tightline over the top of steep slopes down to a"bubble up"energy dissipater catch basin that is City of Renton Catch Basin No. 17,E7-1. We have obtained some as-built records from the City of Renton and included them in this section of the TIR. • 7797.006[RJA/jss/cal M. APO �`�� x .FAG � �0�v ,���...�, j / -.,• `, \k; ,� !� / l; ' �i' /,/ll ! �,, '/ �,i ..tf,4 f� �yy:.v'(.,'�j� 'L•' Qtil1�!%,�71`ti�4\\` '.�\t !a',,; ,��1 P /i w `-r \ •• 1i tIF./ `r;, / �;�/ 1 is •'••` .•✓rrif� """�i" !i:ii,•.i•1„'ifi � :`'•,` \��.c,',••.•{����•:. ••�,},►• "' y`:�.'1;"r~•'y\ �� ifi:!I f,. ' �t}\'•,\'�7 �:r.�7t�`'' ,; %r' r `�... d �r y, ••.t ,, srr,,rc�t.:p �; •� , +%;, '/'/ // :' , '�r/,,•` t/� /`�' �trzl:�'�' �%i:,'�i(��,;I,l�� 1:i i� i.,. 1,�•�`� `.\\ r".�`p`•. ':?•� .%- _ . //•,//��� /•, j/' ,r r .�.,. t 1 JII '' }�•\,"11��.1 ! f 1.`, ,\ �C"\'•',`".`�,' �!','�.. �►,j'^. 'T�• `%, •` .'� '•} ' r %�' // /f / .• ,'./i , %,•- '..:;;1;�Y`;��`(i'":a� �a`,l'N I.ttl t. //!% / �• !:��./ '%•� /�. �, 1` t t /'• , �/ r. % / / �• }` v�11ii+• \ j ... yy��we v P"1 '•"�` t, ti`. ' �l A-, Nv."4 �` \. �:t�Z'1� t /�,' �r I / / 1 - '''' �•� �! �,y\�, L gyp- �: .y.. aM "�l f '�1� .i) 1A T, 4. 10 will: Al u ex V-11� 1 1: r• / Q .�: l ,.`�>�`�• N•.fir;` }1��11t 1l ".r.�'�"".,�r.+ �=.•-�M,r �� ✓, �wr•+r��r, w+ .'�� � ^ w I" ' f '`i%' �}• '+' (' ` / ,..' S• V Y V Y1� 16r �1.11'\� w�++� � +';ls••%;ik�Tlll-i� . / � ) , // ' .� / :�' 1 �/''' t �.EB'!4�„, `. � � ;�+�I- � , '`�' �"`�;�, ti�•1v!`'�'�rf� � �/' li�%� ��Jr �! �. , ..�• ..'!' t7rf•Vr ���/1 • ` ,� .��. �;• i'r 1', �, I J if I�;'/ \��1 I / l 1 i r8-3/'/ ,'r"" l 1 , I t- 74)IM 7. 8Tt 7 STt 1r •� ;; i i i � i I � 1 1.7.�.9— If ! ,r. .... (''� �� l ill/• ' R5E W 1/2 Q .____-240 --- -440 ton City Limits 1:4800 It OS or LO nI tm LM Metm 17 T23N R5E W 1/2 7 5317�--...;Is 5317 STORM DRAINAGE AND OUTLET PIPE INVENTORY - SHEET 17 The inventory information for the storm drainage system was compiled from numerous sources and is the best information available at this time and should be used only for GENERAL guidance . The City of Renton is not responsible for errors or omissions when this information is used for engineering purpose. Designers are to field verify this information. DWN DWN GRATE GRATE UPPER UPPER LOWER LOWER RAT O/W PIPE PIPE LENGTH ENGTH STREAM STRUCT PLAN TRUCTURE INDEX # TYPE CB? ELEV EL[M] IE IE (M) IE IE (M] YPE SEP. DIAM. TYPE (M) STRUCT INDEX# FILE 53175312 17,E3-12 1 - - - - S - 12 CC - - 53176311 17,F3-11 53175314 17,E3-14 2-48. Y 34.49 10.51 28.95 8.82 25.57 7.79 C N 10 PVC - - 53175309 17,E3-9 S-513 53175316 17,E3-16 2-48. N 35.44 10.80 29.94 9.13 26.3 8.02 C N 12 PVC - - 53175309 17,E3-9 S-513 53175317 17,E3-17 2-48. Y 35.98 10.97 30.48 9.29 29.94 9.13 C N 12 PVC - - 53175316 17,E3-16 S-513 53175318 17,E3-18 1 - 35.74 10.89 31.49 9.6 31.32 9.55 S - 12 PVC - 53175317 17,E3-17 S-513 53175319 17,E3-19 1 - 35.05 10,68 - - S - - - 53175320 17,E3-20 S-513 53175320 17,E3-20 1 - 35.09 10.7 - - 27.22 8.3 S 8 CC - - 53175309 17,E3-9 S-513 53175321 17,E3-21 1 - 34.52 10.52 29.89 9.11 29.71 9.06 S - 10 PVC 53173314 17,C3-14 S-513 53175401 17,E4-1 2 Y - - - - - - - N 10 CC 53174401 17,D4-1 1-3-18, 53175402 17,E4-2 2 Y - - - - - - - N 8 CC 53174403 17,D4-3 1-3-18. 53175403 17,E4-3 2 Y - - - - - - N 12 CC 53175501 17,E5-1 53175404 17,E4-4 1 - - - - - - S - 12 CC - 53176412 17,F4-12 53175405 17,E4-5 2 Y - - - - - - N 30 CC - - 53175502 17,E5-2 2-3-53/I-405 D,S. t53175407 17,E4-7 1 - - - - - - S - 12 CC 53175408 17,E4-8 1-1-59. 53175408 17,E4-8 - - - - - - - S - 12 CC - 53175409 17,E4-9 1-1-59. 53175409 17,E4-9 1 - - - - - S - 12 CC 53175410 17,E4-10 1-1-59. 53175410 17,E4-10 1 - - - - - - - S - 12 CC - - 53175411 17,E4-11 1-1-59, 53175411 17,E4-11 1 - - - - - - - S - 12 CC - - 53175310 17,E3-10 53175501 17,E5-1 2 Y - - - - - - - N 12 CC 53174503 17,D5-3 - 53175502 17,E5-2 2 Y - - - - N - _ - - OUT OUT 1-405,D,S 5 175701 17,E7-1 2-72. N - - 124.68 38.00 - - - N - - OUT OUT D-2271 53175801 17,E8-1 1 - - - - - - - - - 12 CC - 53175802 17,E8-2 53175802 17,E8-2 1 12 CC 53175803 17,E8-3 - 53175803 17,E8-3 1 12 CC 53175804 17,E8-4 53175804 17,E8-4 2 Y 351.3 107.07 346.59 105.64 339.08 103.35 C N 12 CC - - 53175818 17,E8-18 R-2038 53175805 17,E8-5 2 Y 328.2 100.04 323.3 98.54 321.04 97.85 C N 12 CC - - 53175806 17,E8-6 R-2038 53175806 17,E8-6 2-48, N 330.1 100.62 324.86 99.02 120.17 36.63 C N 18/16, HDPE 485 147.83 53175701 17,E7-1 D-2271 175806 17,E8-6 1 - 325.9 99.35 321.04 97.85 C - 12 CC - - DITCH DITCH R-2038 53175807 17,E8-7 1 - 376.6 114.78 373.27 113.77 372.98 113.69 S - 12 CPEP 30.3 9.24 53175808 17,E8-8 R-2038 53175808 17,E8-8 1 - 376.7 114.81 372.98 113.69 367.4 111.98 S - 12 CPEP 27.5 8.38 53175809 17,E8-9 R-2038 53175809 17,E8-9 1 - 372.4 113.51 367.2 111.92 366.93 111.84 C - 12 CPEP 27.6 8.41 D.T.POND T.POND R-2038 53175810 17,E8-10 1 - 371.1 113.10 368.56 112.34 368.1 112.20 S - 12 CPEP 30.2 9.21 53175811 17,E8-11 R-2038 Aug , 2001 Page 7 t 53176v.,;IS 5317 STORM DRAINAGE AND OUTLET PIPE INVENTORY - SHEET 17 The inventory information for the storm drainage system was compiled from numerous sources and is the best information available at this time and should be used only for GENERAL guidance . The City of Renton is not responsible for errors or omissions when this information is used for engineering purpose. Designers are to field verify this information. DWN DWN GRATE GRATE UPPER UPPER LOWER LOWER RAT O1W PIPE PIPE LENGTH ENGTH STREAM STRUCT PLAN TRUCTURE INDEX # TYPE C6? ELEV EL[M] IE IE (M] IE IE [M] YPE SEP. DIAM. TYPE (M] STRUCT INDEX# FILE 53175811 17,E8-11 1 - 371.1 113.11 368 112.17 367.3 111.95 S - 12 CPEP 84 25.60 53175809 17,E8-9 R-2038 53175812 17,E8-12 CUL - - - 366.95 111.85 366.86 111.82 - - 12 CPEP 21.4 6.52 53175813 17,E8.13 R-2038 53175813 17,E8-13 2-72. N 372 113.37 366.96 111.85 366.33 111.66 C Y 12 CPEP 129.9 39.59 DITCH DITCH R-2038 53175814 17,E8-14 CUL - - - 365.79 111,49 365.28 111.34 - - 12 CPEP 21.5 6.55 53175815 17,E8-15 R-2038 53175815 17,E8-15 2 N 369.5 112,62 365.18 111.31 355.53 108.37 C Y 12 CPEP 118.1 36.00 53175816 17,E8-16 R-2038 53175816 17,E8-16 2 N 358.7 109.34 355.33 108.31 341.27 104.02 C N 12 CPEP 319.2 97.29 53175817 17,E8-17 R-2038 53175817 17,E8-17 1 - 345.8 105.39 341.27 104.02 339.08 103.35 S - 12 CPEP 15.3 4.66 53175808 17,E8-8 R-2038 • �( (53175818 17,E8-18 1 - 344.3 104.94 339.08 103.35 323.3 98.54 S - 12 - - - 53175805 17,E8-5 R-2038-) 53175901 17,E9-1 1 - - - - - - - 8 CC - - 53175902 17,E9-2 - 53175902 17,E9-2 2 Y - - - - - - - N 8 CC - - 53175903 17,E9-3 - 053175903 17,E9-3 2 Y - - - - - - - N 12 CC - - 53175801 17,E8-1 - 53176201 17,172-1 1 - 38.65 11.78 34.85 10.62 34 10.36 - - 12 CMP 41 12.50 53176202 17,F2-2 16-1-252 53176202 17,F2-2 RAVTO/W 39 11.89 33.5 10.21 33.4 10.18 - Y 12 CMP 15 4.57 53176203 17,F2-3 16-1-252 �53176203 17,F2-3 2 Y 37.6 11.46 32.2 9.81 31.69 9.66 - N 18 CMP 101 30.79 53176205 17,172-5 16-1-252 53176204 17,F2-4 2-54. Y - - 31.3 9.54 31.19 9.51 - N 24 CC 30 9.14 53176205 17,F2-5 16-1-355 53176205 17,F2-5 2-54. Y - - 31.19 9.51 30.07 9.17 - N 24 CC 310 94.49 53176206 17,F2-6 16-1-355 53176206 17,F2-6 2-54. Y - - 30.07 9.17 29.8 9.08 - N 24 CC 75 22.86 53176207 17,F2-7 16-1-355 53176208 17,F2-8 2-48. Y - - 34.3 10.45 33.4 10.18 - N 18 CC 90 27.43 53176209 17,F2-9 16-1-355 53176209 17,F2-9 2-48. Y - - 33.4 10.18 33.2 10.12 - N 18 CC 20 6.10 53176210 17,F2-10 16-1-355 53176210 17,F2-10 1 - - - 33.2 10.12 32.2 9.81 - - 18 CC 100 30.48 53176203 17,F2-3 16-1-355 53176212 17,F2-12 1 - 32.77 9.99 31.22 9.52 31.15 9.49 S - 6 STEEL - - 53176213 17,172-13 S-513 53176213 17,F2-13 1 - 34.4 10.49 30.99 9.45 - - S - 8 STEEL - - RAIL ROAD AIL ROAD S-513 53176223 17,F2-23 1 . 39.83 12.14 37.95 11.57 34.38 10.48 S - 12 CC - - 53176208 17,F2-8 R-2265 53176224 17,F2-24 1 . 48.24 14.70 45.18 13.77 38.16 11.63 S - 12 CC - - 53176223 17,F2-23 R-2265 53176301 17,F3-1 1 - - - 109.97 33.52 - - - - 12 CC - - 53176302 17,F3-2 2-1-52, 53176302 17,F3-2 1 - - - - _ _ - - - - 53176303 17,F3-3 2-1-52. 53176303 17,F3-3 2 Y - - - - _ _ _ N _ _ _ - 53176306 17,F3-6 2-2-103 53176304 17,173-4 2 Y - - - - - - - N - - - - 53176305 17,F3-5 2-2-103 53176305 17,F3-5 2 Y - - - - - - N - - - - 53176303 17,F3-3 2-2-103 53176306 17,F3-6 2 Y - - - - - - - N 24 - - - 53176307 17,F3-7 2-2-103 53176307 17,F3-7 2 Y - - - - - - - N 24 - - - 53176322 17,F3-22 2-3-53, 53176308 17,173-8 1 - 38.67 11.79 36.77 11.21 36.15 11.02 - - 12 CMP 82 24,99 53176309 17,F3-9 16-1-252 } Aug , 2001 Page 8 I / o — — — — — — — — — — — — — - - — — — — — — / slA.9>RdG en"aa,nes I •' Aoi, /// / I I '.S.M.H. No. 7- 48" to pl E r"°°'t /e*- / STA. 8+1 1-- 6 RE. 8"(S)7.6 475 r : I 476 I.E. 8'(Sw)=ovT 7E.Qe va vw/ 3� = 7,ss STA 6WON 4,I3LT. H1611 AVE.3. f NOTE•ST. o -00 5.7TM ST.d ..,j.... \� /�� + MHI S7."0.00 MGM AVE.S r o ti1 I / / I r-- - n� / ._.... x-.VVE 5y- 6" / bz _) _ DATUM: u.s.c.&G.s. �� 6 --"so /a5 / m,. t 6p{ jd �- �!ff.T / EL_s:e7e i ,; ,. I BENCHMARK' CITY OF RENTON B.M. No. 260 /A- G Q 5� \/ qi '( E ersE)-zsro ►t t�.> i� , 6 / / ,.E.,rts-�t.e:>. tti0 CHISELED SOUARE AT BACK OF WALK INTERSECTION, O E�', (y. •„wu 6t, _ N.W. CORNER SOUTH 7th ST. 8 HIGH AVE. S. -s. `� /p r / cP �"�L.P u, •,6 �.."`"`""""a ELEVATION - 357.87 C6 co G r I ti _ - _- - - - - - - - - - - - - - - - - - - - - - - - — - - - - - - - - - - - I1 GRAPHIC SCALE \ , OC PZ/� 1.TA.9fG7 I� \ S.S.M.H. No. 8- as } ,; / " o' -- ., o"Pvc Plt/li .F-32SsS I IN nwr)STA. 6+43.04 1 r„-/. ..._---._... ...•.$$' P✓c STs. 9s•6p, RIM EL=.32 1 h>ce 20 R 1t 8.2/. I �'/ - M .., G FYC PLUG J'�c.31SLg I.E. 8'(NE)-�Nc3/G./S 1,n I.E. 8"{NW)=OUT % e I I I .7.7. /�Q �. •I� \ STA:7•g8J 5, 6RT.-BEACON 3' 'AS-BUILT CERTIFICATE I' rC f ?.55 NOTE-LD&TK 9 INTX.S.7TH ST. •/1{Jr b "' O { �, •n ACON AVE. 0.00-BEACON A NERERY CSW.&Fv v y ME FCUCwMB C4MMM 11Er S,TOW I FmOm NENMv on 4•cLr Orr=NRMY _. / / - II �• -`\ II; NOTE: o�'y °=W�"o,�y D811DNs+4 Asra►AfM6[11H1 wnoaar6nr �I I I \ I I EXISTING ROADWAY STORM DRAIN LINE MUST BE PROTECTED 2 n. IOQATNM 1Awm D 1m I oo= a I / ' hI,' �l DURING CONSTRUCTION. 2" A/C PAVEMENT OVERLAY OF HIGH I ydRRUlololoM vsahooars� otlsamelold�AV. S. WILL BE REQUIRED IF DAMAGE OCCURS DURING CONSTRUCTION. ' jf �1 �[a® OOIIOI \� �I;Y P1� '��.I � �` •'y !I I _ . I f _rA 480 ,� 7z�, � �� UtiD ����f_'7� ____ ///�7�/qz_ '1 i . o OTE: I sTA. M.H.0, S.S.M.H. No. 5- 48' ,�\\ I r11 r11 I I� \` TRAITOR TO CooR01NA4� I II RIM EL.=34s:o9 NOTE: '1 1 STA. 14+39.21 - STA. 0+00(ON-SITE SS) 1' TA UTILITY FOR UTILIX.POLE ( )_r✓ OVERLAY FULL WIDTH OF S.GTH ST.WITH •'�S BIUZATION DURI ' ,� I-E• 8"E iE¢G�LO.vKs333.37 2" A/C REOJIRED AFTER RIM EL=fd9.of I r7; as I �1,1 1, I�I \\, C STRUCTION. 5 I ..-I- _:.I, I.E. 8'(N)=oaT BACK OF UTILITY LINES. /6,g(„{iAw/,tCs+f4,488 \\ V ,fl `l ` r I ' LE.8'4SE)-Av �• J '' STA 4.32. I57_T.-NG71 AVE•S- 9 I.E. Ir W) ovT. STA:3.26.39 10'LT.-S.BTH ST.I I STA./t CONTRACTOR TO COORDIN O �e't WITH UTILITY FOR UTILITY POLE X1, I — „ 6sR�c.Pla6 �� OSTABIUZATION DURING \ x roz.�e o 3Uo ale v . �,,.�e -- SOUTH -- - coNSTRucnoN. / _' 6th _.STA sr.¢. t.� /'" I,��/ 1, J / �1 S. T_f' 1 — —�_ N 6:ivG' vG7 EQUATION/ ,tPoTE•MIX.NOT►tWR1MIXT /`S,'3 J/ "CPE�CJ/�35� O,..,a 4v /E,:3GrS,SS 'l!i I IAI~ \ .•`— — — — — _ Q /' a STA 14+39.35 OFF-SI AN. SEWER - VV 'T + '- N89"It'26-W ✓ � TA. 0+00 SAN. SEWER THR LOT 11 �T ; 41�1 I r` I t24 341.9' - PVC 04.83 " r'� \\\\ i i �(' 1T).'' 11, i�� wrrorper i ,� \ LE- O CROSSING 5/1.00_ _ .._-�AS-BUILT�� '!/9.�.-- - � '�t3«00 -/ CRO SIN = - SEE 8 of 17 'L O t� 11ZGH.'u6_ — N•' �• EET FOR CHONTINUATIOO 13 ,r t qrE �" -•/ -337.14 E-eummo �."� cvr�r ,yp0 \ >�,�.1.., �.1 ��I�I \\ .bl I I 50 -- •.E:. -i.. 1e-,tr> -- 'ram' ,s_rA./3.f�/ ,� C.B. No. 14- TYPE I 1 �j.- Z` \ •- 11 r11. �I ,r ,' ,'`\ S C$.I�. !/6.- - STA. 14+36.74, 5' RT. - !�; ...�Fil �' `' sT.vii�iG.� Y!-I ' _._--_..r44f/S - �� 'rr1, �, \\ I I w/s�Gn lx w6 a I y .5,, 5' RT. (ON-SITE) � \\ I.I I` 1 on oaE „� r�•�'._. .. I.-. A�M E�z3t/S77 y r•�^ \ •�( I I _ 1 I ii'•FJs30/.t7 I ti "I O LOCKING LID r„e1E' I O O RIM. f t l JSS.S3 485 � � J p 6r SLT.-8.8TH ST. tz a ' C.B. No. 15A-TYPE I t� 486 , _.- ,x;p- --- sTA. II+o¢,S,4.3'LT. STA4-27.8%9.47'LT.-HK01AVE.9 ` CITY OF RENTON �I t •J -- -�-, Eizv s'+99 =/SOLID LOCKING UD NOTE,MON E MTX.S.7TH ST.L RECOMMENDED DEPARTMENT OF PUBLIC WORKS .}(' 1 1� \ - I •fir.-.s-.)..•s:n MGH AVE RIM EL 34 f Z8 E.S.-0•00-W3H AVE.S.. V\M FOR APPROVAL I �, j &.'- L E. 12'S-N)=33fo�EXIST.) ' `� +E .. '• S.S. & S.D.(OFF—SITE)—PLAN ,, S q1 CONTRACTOR TO VERIFY LOCATION AE I.E. _�, !1 RIVER RIDGE \I\� I I PRIOR TO CONSTRUCTION IS w �.. t4. ,tom ona 6/13/91 mz isAm 89041 �e •. ly�''1'llll ,� \ p RECOMMENDED o•.°i'' �?.�� cmcuulm. MD k I, / V,LI� :...,\ FORAP�� Sfiv"�'' 2 os.BaxT ✓sFir sTeM cat io r9/11 DRAra DGL ++ 7h "I�\ t* `r11 1 PER REVIEW 9/27/91 ASP MLD 10/3/91 CNDCIREt MD x'� 1'='l0' --ems _*� WWP- - �\ �A\ I �5 \ lr Iro nvnmK BY grwt Dqn ArvRD� sxm 10 ue 18 .... 1 TOP OF \ \ INSTALL NEW PICKET FENCE SET BACK 5'MINIMUM MA'AM SLOPE FROM EDGE OF SLOPE SEE DETAIL 1 (NEW �.SH B PERMANENT SLOPE STABILIZATION AREA PIPE ANCHOR (TYP.) -.} 525 HIGH AVENUE SOUTH �"� II n APPROXIMATE G, o 2— CLEARING LIMIT SEE SPECIFICATIONS 'A / ASPHALT— I 11 1 '- � ^\ \`APPROX f MATE ALIGNMENT OF NEV `OPe p/P X�- DRIVEWAY \ �� GRAVEL XfSTING \\� r S�UTH NK PLAN 1 20 FT. UTILITY EASEMENT AS RECORDED\ ARK&PLAN G AVENUE 1 UNDER KING COUNTY RECORDING 22 9002269004. KING COUNTY RECORDING N0. 9202269004. a REINSTALL LANDSCAPE BARK NTING / \' IN i ' NOTE: /� .J/ / S ALL HGH NSIBlUTY ALONG EDGE OF SLIDE AREA SEE NOTES / / T \\�C \ , ( t/ 1 C STRUCTI FENCE _ THE EXISTING TOPOGRAPHIC AND PHYSICAL FEATURES SHOWN / \�_- ' e I 0 � —337 J � INSTALL NEW 11 CB CB 1 ON THESE PLANS ARE BASED ON A COMBINATION OF: �--�' \ �1,� SILT FEN E `\ I INSTALL TEMPORA/�Y \ \� ( �) ' AS-BUILTS AND FIELD SURVEY DATA PRONGED BY ENTRANCO. / I I I I '� -- �— (STND. PLAN 9027) BURIED TRENCH SECTION 334- SEE CONNECTION DETAIL E SEE DETAIL A THIS WAS THE INFORMATION AVAILABLE AT THE TIME OF PLAN / - PREPARATION. ACTUAL CONDITIONS MAY BE DIFFERENT. THE CONTRACTOR MAY ENCOUNTER VARIATIONS BETWEEN ACTUAL CONDITIONS AND THOSE SHOWN. THESE VARIATIONS WILL NOT BE 1 THETHE LOCATISIS FOR A ON OF EXISTING OR EXTRA COMPENSATION. UNDERGROUND UTILITIES ARE SHOWN 1 - IN AN APPROXIMATE WAY ONLY AND HAVE NOT BEEN INDEPENDENTLY VERIFIED BY THE OWNER OR ENTRANCO. THE CONTRACTOR SHALL 9 DETERMINE THE EXACT LOCATION OF ALL EXISTING UTILITIES BEFORE 1 COMMENCING WORK, AND AGREES TO BE FULLY RESPONSIBLE FOR ANY SEE DETAIL C i AND ALL DAMAGES WHICH MIGHT BE OCCASIONED BY THE CONTRACTOR'S ` APPROXIMATE FAILURE TO EXACTLY LOCATE AND PRESERVE ANY AND ALL UNDERGROUND NAO 1983191 HORIZ. DATUM UTILITIES. / WETLAND BOUNDARY NAVD 1988 VERT. DATUM I BENCHMARK - CONCRETE MOMUMENT AT INSTALL LANDSCAPE BARK ALONG FENCEUNE TO MATCH EXISTING INTERSECTION OF HIGH AVE. SOUTH AND LANDSCAPING. PLANT SHRUBS 10'APART. BEACOM WAY SOUTH 358.33 FT i I I O VEHICLE ACCESS I ' REMOVE EXIl77NG CATCHI BASIN I ! 1 N EX`iS71NG GRWf ID SURFACE ! ----rt-- I �------I ------ -�------I---------I-------- 340---I�-------! 240 --- E --�------- i -- - -- � � __ 240 TIN 12"CONC. ------ ------ - --- f }� rr - jFEMOVE EXIS NG CMP A PIPE _ I 5=.0761 / NE 18-SOR HDPE Pf32 Pq i _ ! ti r - --I— !I-- ---Ii -------!; ! 320 rt220 220 AS-89ILT I { � I o i i •a SOOT- -----4- -— --- CD { ---__ -- —�--- + 300 I 200 --- { �s• I ' " I� -- ----- I 200 ij I 280 180 i �<W r- — ---- --, F — ---z - --—�----- ---- ---- -- {—- --- —---f---- - 7. J i { I 10 _. — °m WX _____ c W — --- F —160 + I j N EXISTINGI D SUR —240 -- 140 La 12 z �- 220I 220 120 — — I - - - ----_ --- -- --- i -- --�__— Zrx i i s I - ----.r W o I I —r---—I I r---- -----�-- --— Q --- `- —� RIICbMM13ND --+-----t----- t-- —+-- _ 120 POR I i sY -n-fc AEL -- — -- 200 I 100 _ _ NEW 18-SOR{26 HOPE PIPE NE 16•SDR 26 HDPE PIP--__-- ---_-- - —__ - -- — — BY _ +So I � —�------- 20 10 0 2 40 HORIZ 7--20 ! I -- 20 10 0 20 40 _-1801--_—_�---- _—_—I ! I I FOR LIANCE vERT. 1•=20 180 _ 80 _ CHE � CITY OF RENTON r—----- -- —�- -- --- - -- -�—--- --= ARt i-- DEPARTMENT OF PVBLIC WORKS HIGH AVENUE SOUTH I N TER AN CIO _--I -- _-- -- I -p ats-_ 0. I +- 4400 STORMWATER OUTFALL IMPROV EMENTS EdEERS SCIES$ • NERS • unros „' 6 e PLAN $ PROFILE HINGTON i ARIZ09A 0 c,TK'MLFiwt DE8IDREG EWJ DATE 7/10/96 ROE NANE,HAPPI.DWO r. I I I { i I �lDRAL DRAWM KAK y 0/ 00 f +50 I 1 0 I +50 ! 2 00 2 00 +50 ( 3 SDALE 1• - 20' mcsoaA ••.� S w O -?L a +23 s r23 I +73 +25 tTJ , ID 3 t NQ REV�SIOtI A�BY AP�PR. DA.TEL APPROVED: SHEET, 2 OF, 4 • 3.1 DOWNSTREAM ANALYSIS BY PETERSON CONSULTING ENGINEERS DATED APRIL 10, 2000 >F ` l • HERITAGE PHILIP ARNOLD Preliminary Technical Information Report City of Renton April 10, 2000 Prepared for: Bennett Development Nine Lake Bellevue Dr. Suite 100-A Prepared by: Bellevue, WA 98005 Nicole McWhirter Reviewed by: g, Jennifer A. Steig, P.E. P ETERSON CONSULTING Y6�a ieem n ° ONAL �� \�\ 4030 LAKE WASHINGTON BLVD.NE,SUITE 200 EXPIRES SEPTF�A6ER OB, 2d00 KIRKLAND,WASHINGTON 98033 • PCE Job No. HERM-0025 A. TABLE OF CONTENTS • I. PROJECT OVERVIEW 1 H. CONDITIONS AND REQUHWAENTS SUMMARY 4 M. OFF-SITE ANALYSIS 6 TASK 1:STUDY AREA DEFINTHON&]NAPS 6 TASK 2:RESOURCE REVIEW 6 TASK 3:FIELD INSPECTION 10 TASK 4:DRAINAGE SYSTEMDESCRIPT TON AND PROBLEM SCREENING 11 IV. FLOW CONTROL AND WATER QUALITY ANALYSIS AND DESIGN 13 Existing Site Hydrology 13 Developed Site Hydrology 13 Facility Design 17 V. CONVEYANCE SYSTEMS ANALYSIS AND DESIGN 22 • VI. SPECIAL REPORTS AND STUDIES 22 VII.OTHER PERMITS 22 VIII.ESC ANALYSIS AND DESIGN 22 IX.BOND QUANTITIES,FACILITY SUMMARIES AND DECLARATION OF COVENANT 23 XI.OPERATIONS AND MAINTENANCE MANUAL 23 • Peterson Consulting Engineers Page i Prelimina Technical In ormahon Report for Henta e Phili Arnold A ri110 2000 • FIGURES Figure 1: Vicinity Map Figure 2: Site Map 2 Figure 3: USGS Map 5 Figure 4: SCS Soils Map 7 Figure 5: KC Level One Table 9 Figure 6: Existing Conditions Map 12 Figure 7: Developed Conditions Map 14 15 APPENDIX Lower Cedar River Sub-Basin Lower Cedar River Basin Map Reconnaissance Report NO. 13 Sensitive Area Folio Maps (Landslide, Seismic, Erosion, Coalmine, Stre Floodplams and Wetlands) and 100-Year Biofiltration Swale Worksheet 1998 King County Surface Water Design Manual(KCSWDM) POCKET Downstream Map • • Peterson Consulting Engineers Page ii SEC. 20, TWP. 23 N., RGE. 5 E., W.M. PONRSONNG I G�. 4030 Lake Washington RIVER RIDvE 1 VOL. 153i99-101 \ � \ Blvd.N.E.,Suite 200-/ I ► I 733000 \\\ \ Kirkland,WA 98033 r Tel(425)827-5874 Fax(425)822-7216 34 2 \ STOWWA7ER 4,3 42 41 40 39 38 37 36 35 Q TRACT . 1 ? I t f ROAD 'A' ` 32 '8 Q 100' ` 0 100' I I i PARK SCALE: 1" 100' 44 5 4s 47 4 49 e Q t _� ► I .30 ---- v, l e I c� I I 2 55 54 53 52 51 29 c I I 28 ; c 4 x .= ROAD, T O �'. I _ 5 27 I6 7 8 9 10 11 I ( 26 I ` I t ►�` I I % 25` �a��aR �f}y EI 6 I I 16 15 14 13 12 `_ Ca I I CITY OF P.ENTON \ 24 I o PHILIP ARNOLD PARK z ddddddddddd 23 t DESNTIER 1 s7oe I I I \ LIS 7RACT i CADa R,®, MER 17\ — D 22 DAB 41'e1Dn FUNANEMMM — 21 I- 7 18 ---t I 20 1 � I I• I I L 7RAC srAMV NOT VALS) UNLESS SIGNED AND DAitD X i "HERM-0025 FIGURE 2 PAGE 5 Preliminary Technical Information Report for Heritage Philip Arnold April 10 2000 • III. OFF-SITE ANALYSIS TASK]:STUDYAREA DEFINITION&MAPS The 10.35-acre site is located on the northwest comer of the intersection of Beacon Way, SE 76' Court, Jones Avenue South and South 7 h Street in the City of Renton, Washington. More generally, the site is located in Section 20, Township 23 North, Range 5 East, W.M. in King County, Washington(see Figure 1: Vicinity Map on Page 2). The site is located in the Cedar River Drainage Basin, bower Cedar River Sub-basin as defined in the King County Basin Reconnaissance Program Summary Volume H. The Lower Cedar River Basin Map and a portion of the Basin Reconnaissance Report NO. 13 have been provided in the Appendix. UPSTREAM DRAINAGE ANALYSIS • There is no upstream area tributary to the site see Figure 3: USGS Map on Page 7. TASK 2:RESOURCE REVIEW Community Plan The site is located in the Newcastle Community Planning Area. Adopted Basin Plan/Basin Reconnaissance Summary Report The site is located in the Cedar River Basin, Lower Cedar River Sub-basin Collection Point Area#2. Critical Drainage Area The site is not located in any of the Critical Drainage Areas as identified in the 1990 King County Surface Water Design Manual. • Peterson Consulting Engineers Page 6 I F00, will �// � ��.�. •ram RRHOU ell IN I IIIRk MIN Rvir Mill NEW I I N Ow '" - ;^ s:OWN e..an •� �1''`1��'�,�� ter' ! I�T, i� T��NtLL1e\�`\ �,�` \����ir�IcZt�'/Q\�,• ®aim �111•i�1�R i6�4� � � I _ ® _ . i �0 � • • WN. B Y_- " DATE., JOB 4030 ' •ETERSON •:� N G I N E E R S J__��=2000 Preliminary Technicallnformation Report for Heritage Philip Arnold April 10 2000 Sensitive Area Folio • The King County Sensitive Areas maps did not reveal that the site was located in hazard areas, such as, landslide, erosion and seismic. The site has been designated in a coalmine hazard area. The site does not contain any classified wetlands or streams (See Appendix for maps). SCS Soil Survey The soils on the site, per the SCS Soils mapping, are InC-Indianola Loamy Fine Sand and AgC-Alderwood Gravelly Sandy Loam; see Figure 4: SCS Soils Map on page 9. Wetlands Inventory There are no classified wetlands on-site. • • Peterson Consulting Engineers Page 8 • r —„ An aseb'eit HL�ll I Ceml yGRAVEL 'PIT _ Park PC - ♦ BM I Ix — ;�321. C °. 16 o i an \ ••Rn. ' •P� D 1 9 C AkF I Ev C -- ----I A.kF- i3 o F h ---- -- • yei�C I L I i. • `/ M137 AkF RjT' 'R 1 I _ _ — sig '- 3. At., = o- AgC / - ---, InC 1 `r---- / - -•'---•-',, - ' � - --1- ,f •,`I �1 •.� GyO°4G6�� ,i r` �. ``�� AgD mil•_` substa i AmC --- J AgC AgD 20 B aoa 4 Z1 455 i I � n• 9�c �aa ABC `".. /�/� AQ o =;ii• "BeC •�• .ii:•j (AgD ` n •I A t AgC D r Z 7 •.. m Z I Sk G u ( 1 AmC �BM Z9 AgC . Ag6 169 — — 2 HERITAGE PHILIP ARNOLD FIGURE 4: SOS SOILS MAP SEC. 20, TWN. 231V, RGE. -5E zi n o D WN. BY. DATE.' JOB NO. 2 on —0025ERSON Bly&Lake NEM 0411%0 HERM `* CONSULTING Kirkland,WA98o33 o Tel(425)827-M74 CHKD. BY.' SCALE: Fax(425)822-7216 PAGE 9 NEM 1"=2000' y �4 Preliminary Technical Information Report for Heritage Philip Arnold April 10 2000 • TASK 3: FIELD INSPECTION A site visit was made on April 4, 2000, a cold rainy day. The site is currently undeveloped; generally the site is covered with meadow and grass with deciduous and evergreen trees and slopes to the northwest at 6-15 percent. Runoff from the site and upstream area is tributary to the Cedar River. A request for drainage complaints was made to King County DDES in order to investigate past and/or present characteristics of the downstream path. The only complaint on record with the county was from 1985 (complaint# 85-1102) and has been closed for over 14 years. • • Peterson Consulting Engineers Page 10 Preliminary Technical information Report for Heritage Phi lip Arnold April 10 2000 • TASK 4:DRAINAGE SYSTEM DESCRIPTIONAND PROBLEM SCREENING Please reference Figure 5: KC Level 1 Table on Page 12 and Downstream Map in pocket of report. Drainage from the site sheet flows to the northwest comer of the property (point A). From this point any runoff from the site would enter the existing 12" tightline system on the northwest side of Beacon Way SE (point B) approximately 120' from the property comer. This 12" tightline system continues to the northwest along Beacon Way South for approximately 400' before changing directions (point Q, north, at the intersection of High Avenue South. The tightline system changes to the north at point D for approximately 260'. The pipe diameter increases from 12 to 18" at point E. The next catch basin contains the top connection for the HDPE outfall (point F). The HDPE pipe is approximately 485' in length and conveys the runoff aboveground over the steep slopes of Renton Hill to a Type U-72" SDMH (point G). The manhole contains a jailhouse opening for overflow. The runoff from the manhole is conveyed via a natural swale (point H), depth and width varying, to a large pond area. Due to the depth of water an outlet was not visible, from this point it was difficult • to determine where the runoff was conveyed. • Peterson Consulting Engineers Page 11 suftow "Now OFF—SITE ANALYSIS DRAINAGE SYSTEM TABLE SURFACE WATER DESIGN MANUAL, CORE REQUIREMENT #2 Basin: Cedar River Subbasin Name: Lower Cedar River Subbasin Number: Symb"ol Drainage Dra > age Slope �stahce,, Existing Potential Observations of field Component Type,, CQr�1p� t�entg Problems Problems,< " inspector, resource' Name;;and Sizes ich�ir reviewer, or"resident see map Type:sheet flow,Swale, dramag at5ltatY � tlon, °b" " ' fk11 constrictions,under capacity,ponding,Y tributary area;likelihood of problem stream,channel,pipe, cover,"d@p h;`tyt2e�of ¢hsitive overtopping,flooding,habitat or,organj".( overflow pathways,potential pond Size;diameter, afeavo)ume destruction,scouring;bahX slouphln'g, Impacts surface area W sedimentation Inclsion,othe erosl`on A Sheet Flow 6-30 0 None None No standing water observed on-site B 12" tightline system Within Beacon Way 5 120 None None SE C 12" tightline system To West side of High 5 620 None None Ave. S D 12" tightline system North 5 745 None None E 18" tightline system 5 1005 None None F_GG Top connection for 1115 HDPE pipe Type II-72" SDMH W/jailhouse opening 1600 None None '/a Mile point within this reach H Drainage Swale Width & depth varies 5-10 None None Uq t N cJ, - - LOWER CEDAR RIVER BASIN • Basin Boundary � � - •- ''' � '-' Subcatchment Boundary : Collection Iec ion Point- 2 t' IStream 0299 Tributary Num - y 1 I i _ ,i ber `� 03115 Proposed Project , l nr o I '> °`� j ° z Miles TT I , 1 - / Jw 19 `• < 3105 i'. .• 26 02sg .` b - `i w1 7�e ' 3121 •\ O N �jr i S �.�u V �� 1 , , :I 3122 1 p3 3116 o u. " r — ,i '•,� �, r Y o• w 3115 yC .OF EATTLF W ' , r I 0 x 12 311 ;x • N. M&yM voky �u t� • RECONNAISSANCE REPORT NO. 13 LOWER CEDAR CREEK BASIN • JUNE 1937 Natural Resources and Parks Division and Surface Water Management Division King County, Washington • King County Executive Tim Hill King County Council f • Audrey Gruger, District 1 Cynthia Sullivan, District 2 Bill Reams, District 3 Lois North, District 4 Ron Sims, District 5 Bruce Lain-, District 6 Paul Barden, District 7 Bob Grieve, District 8 Gary Grant, District 9 Department of Public Works Parks, Planning and Resources Don LaBelle, Director Joe Nagel, Director Surface Water Management Division Natural Resources and Parks Division Joseph J. Simmler, Division Manager Russ Cahill, Division Manager Jim Kramer, Assistant Division ManaC, Bill Jolly, Acting Division Manager Dave Clark. Manager, River �C Water Derek Poon, Chief. Resources Planning Section Resource Section Bill Eckel. Manager. Basin Planning Program Larry Gibbons, Manager, Project Management and Design Section Contributing Staff Contributing Staff • Doug Chin. Sr. En-ineer Ray Heller, Project Manager & Team Leader Randall Parsons, Sr. Engineer Matthew Clark, Project Manager Andy Levesque, Sr. Engineer Robert R. Fuerstenberg, Biologist Team Leader Bruce Barker, Engineer Matthew J. Bruengo, Geologist Arny Stonkus, Engineer Lee Benda, Geologist Ray Steiger, Engineer Derek Booth, Geologist Pete Ringen, Engineer Dvanne Sheldon, Wetlands Biologist Cindy Baker, Earth Scientist Di Johnson, Planning Support Technician Robert Radek, Planning Support Technician Randal Bays Planning Support Technician Fred Bentler, Planning Support Technician Consulting Staff Mark Hudson, Planning Support Technician Sharon Clausen, Planning Support Technician Don Spencer. Associate Geologist, Earth David Truax, Planning Support Technician Consultants, Inc. Brian Vanderburg, Planning Support Technician John Bethel, Soil Scientist, Earth Carolyn M. Byeriv, Technical Writer Consultants, Inc. Susanna Hornig. Technical Writer Virginia Newman, Graphic Artist Marcia McNulty, Typesetter Mildred Miller, Typesetter Jaki Reed, Typesetter Lela Lira, Office Technician Marty Cox, Office Technician P:CR TABLE OF CONTENTS • I. SUMMARY 1 II. INTRODUCTION 1 III. FINDINGS IN LOWER CEDAR RIVER BASIN 2 A. Overview of Basin B. Effects of Urbanization 4 C. Specific Problems 5 1. Drainage and flooding problems 5 2. Damage to property 6 3. Destruction of habitat' 6 IV. RECOMMENDATIONS FOR ACTION 7 A. Reduce landslide hazards 7 • B. Reduce erosion and flooding 7 C. Prevent future erosion and flooding with appropriate analysis, g planning, and policy development D. Stop present (and prevent future) damage to habitat g by addressing specific problems in stream systems V. MAP 11 APPENDICES: APPENDIX A: Estimated Costs A-1 APPENDIX B: Capital Improvement Project Ranking B-1 APPEDDIX C: Detailed Findings and Recommendations C-1 I. SUMMARY The Lower Cedar River Basin, in southwest• King County, is unique in its development pat- terns and the associated environmental problems that appear throughout the basin. Except for the city of Renton and areas on the Cedar River Valley floor, most of the development in the basin has occurred on the upland plateaus. Most of this development is recent and primarily residential. In addition, the plateau is the site of numerous sand and gravel mining operations and, in the southern uplands, an abandoned coal mine. Peat is also being mined north of Otter Lake. In some areas livestock are being raised on small farms; there are no major crop-related agricultural activities in the basin. The effects of development are most apparent where storm drainage is routed over the valley walls. Impervious surfaces on the plateau have increased the rate and volume of storm runoff, resulting in substantial erosion, siltation, and flooding below. In addi- tion, erosion and siltation have damaged or destroyed habitat in many tributaries, threatening the survival of fish. Habitat and water quality throughout the basin are also threatened by the filling of wetlands and the presence of large amounts of domestic trash in some streams. The reconnaissance team noted that the Peterson Creek system has so far remained in its natural, nearly pristine condition. Maintaining this quality should be a high priority in future basin planning capital project programs. Recommendations in the Lower Cedar River Basin include 1) designing and constructing appropriately sized RID and other drainage facilities; 2) establishing stricter land use policies regarding floodplains, wetlands, and gravel mining; 3) conducting more detailed and comprehensive hydraulic/hydrologic analyses of proposed developments; and 4) preventing damage to the natural drainage system. The field team also recommends 5) restoring the habitat of several tributaries (e.g., cleaning gravels, revegetating stream banks, and diversifying streambeds for spawning and rearing) as well as 6) protecting the nearly pristine quality of Peterson Creek. • II. INTRODUCTION: History and Goals of the Program In 1935 the King County Council approved funding for the Planning Division (now called the Natural Resources and Parks Division), in coordination with the Surface Water Management Division, to conduct a reconnaissance of 29 major drainage basins located in King County. The effort began with an initial investigation of three basins -- Evans, Soos, and Hylebos Creeks -- in order to determine existing and potential surface water problems and to recommend action to mitigate and prevent these problems. These initial investiga- tions used available data and new field observations to examine geology, hydrology, and habitat conditions in each basin. Findings from these three basins led the King County Council to adopt Resolution 6013 in April 1986, calling for reconnaissance to be completed on the remaining 26 basins. The Basin Reconnaissance Program, which was subsequently established, is now an important ele- ment of surface water management. The goals of the program are to provide useful data with regard to 1) critical problems needing immediate solutions, 2) basin characteristics for use in the preparation of detailed basin management plans, and 3) capital costs associated with the early.resolution of drainage and problems. The reconnaissance reports are intended to provide an evaluation of present drainage con- ditions in the County in order to transmit information to policymakers to aid them in developing more detailed regulatory measures and specific capital improvement plans. Thev are not intended to ascribe in any conclusive manner the causes of drainage or erosion • P:LC I Lower Cedar River Basin (continued) problems; instead, they are to be used as initial suc,Veys from which choices for subsequent detailed engineerng and other professional environmental analvses may be made. Due to the limited amount of time available for the field work in each basin, the reports must be viewed as descriptive environmental narratives rather than as final engineering conclusions. Recommendations contained in each report provide a description of potential mitigative measures for each particular basin; these measures might provide maximum environmental protection through capital project construction or development approval conditions. The appropriate extent of such measures will be decided on a case-by-case basis by County offi- cials responsible for reviewing applications for permit approvals and for choosing among competing projects for public construction. Nothing in the reports is intended to substitute for a more thorough environmental and engineering analysis possible on a site-specific basis for any proposal �- FINDINGS IN LOWER CEDAR RIVER BASIN The field reconnaissance of Lower Cedar River Basin was conducted in January 1987 by Robert R. Fuerstenberg, biologist; Bruce L. Barker, engineer; and Lee Benda, geologist_Their findings and recommendations are presented here. A- Overview of Lower Cedar River Basin The lower Cedar River Basin is located in southwest King County and is 27 square miles in area. It extends southeast from the mouth of the Cedar River on Lake Washington to approximately river mile 14.0. The• boundary to the northeast is marked by a ridgetop connecting the city of Renton to Webster and Franklin Lakes; the boundary to the southwest runs along Petrovitsky Road to Lake Youngs. Renton is the only incorporated area in the basin. Other population centers include Fairwood, Maplewood Heights, and Maple Valley. Except for the city of Renton, most of the residential concentrations are located on the upland plateaus overlooking the Cedar River Valley. These upland developments are recent compared to the smaller established communities on the valley floor. The basin lies within portions of three King County planning areas: Newcastle in the northeast (which includes Renton), Tahoma-Raven Heights in the east, and Soos Creek (the largest of the three) in the west. Rural areas exist on the valley floor on both sides of the Lower Cedar River, from approximately river mile 5.50 to 13.00. These are limited to pastureland for horses. cows, and some sheep and several small "u-pick" fruit and vegetable farms. Similar areas are located on the southern uplands above the reach from river mile 5.50 to 7.00 and in the Lake Desire-Otter Lake area. The plateau is also the site of sand and gravel mining operations and, in the southern uplands, of the abandoned Fire King Coal Mine. Peat deposits exist west of Lake Desire and north and south of Otter Lake, and peat mining is being carried out north of Otter Lake. Present zoning allows for urban and suburban densities throughout much of the basin. Particularly on the upland plateaus and in the Cedar River Vallev from its mouth to appoximately river mite 6.50. Population projections for the vear 2000 in the three planninn areas containing the Lower Cedar Basin are over 311,000; an increase of 47 • P:LC 2 Lower Cedar River Basin (continued) • percent from the present. Most of this growth will occur in the Soos Creek Plan R Area. mn0 Donunant geological and geomorphic features. The geology of the Lower Cedar River Basin is diverse. Geological formations exposed along the valley include sedimentary rocks, undifferentiated older glacial drift, extensive ground moraine deposits, recent alluvium along the Cedar River, and landslide deposits along the river and its tribu- taries. The sedimentary rocks, composed of moderately dipping sandstones, con- glomerates, mudstones, and shales, are exposed locally along the cliffs of the Cedar River Valley near the mouth of the Cedar River. In addition, the Renton formation. composed of sandstones, mudstones, and shales with periodic deposits of coal, is also exposed along the lower portion of the Lower Cedar River Valley. Undifferentiated glacial deposits found here are composed of three or more till sheets, glacio-fluvial sand and gravel, glacio-lacustrine clay, and sand, and non-glacial sand, clay and thin peat. These lie over the sedimentary rock formations and are best exposed in cross-section along the cliffs of the main valley and major tributaries. The morphology of the Lower Cedar River Basin is dominated by the valley formed by the Cedar River. Valley walls are steep cliffs formed by landslides in glacial sedi- ments. A once extensive and meandering River, which created a wide valley floor as it cut its way westward, the Cedar today is diked for most of its length through the lower valley. A narrow but extensive band of landslide deposits exists along the steep cliffs of the main river and its major tributaries. The landslide deposits consist of • deformed blocks of glacial sediments and colluvium derived from slides or mass flowage, such as landslides and debris flows. Recent alluvial deposits fill the valley and major tributaries. Small, composite, alluvial debris fans exist at the mouths of the largest tributaries. Closed depressions, principally in the uplands, have lacustrine and peat deposits. The Lower Cedar River Valley has a high potential for erosion due to steep slopes and the existence of a clay laver that promotes soil failures. In addition, the confined nature of tributary channels between steep hillslopes promotes bank erosion during hi gh flows. Numerous recent landslides are evident along cliffs of many of the steep tributaries and along the main stem of the Cedar River. These have been accelerated by the removal of vegetation and the routing of concentrated storm flows over steep slopes in areas where development has occurred. Hydrologic and hydraulic characteristics- The Cedar River Basin is composed of a complex drainage network consisting of the Cedar River and 17 tributaries. The larger tributaries begin in lakes or wetlands on the bluffs and flow through relatively flat, stable channels to the edge of the Cedar River Valley, then plunge down to the valley floor through steep, erodible ravines. Tributaries of this type such as Tributary 0304 (with headwaters at Wetland 3111) and Tributary 0323 (which begins at Lake Desire), are found on the south side of the Cedar River. Another type of tributary collects surface runoff from urbanized areas, pastureland, and wooded areas. Tributaries 0302, 0307, and 0312 are examples of this type of tributary. They are intermittent (depending on rainfall), shorter in length, flow through shallower channels that are steeper at the bluffs and transport more material during times of • P:LC 3 Lower Cedar River Basin (continued) • high flows Some of the worst ro l p blems located during field investigation (see Appendix C for a full listing) occur on this type of tributary. Catchments 5, 6, and 12 have very infiltrative soils. Urban developments hvae utilized R/D poinds to effectively infiltrate all urban runoff before it reaches the valley hillslopes. The infiltrated runoff then reappears as springs. Two large lakes (Desire and Otter), together with four smaller ones (Shady, Peterson Webster, and Francis) lie in the southeast third of the basin. Numerous large wetland areas exist in this section as well. The field team identified 10 potential wetland sites that had not been previously identified in the Sensitive Areas Map Folio (SAMF). The system of lakes and wetlands in this area effectively buffers the high flows draining to these tributaries. Habitat characteristics. With few exceptions, usable fish habitat exists only in peren- nial streams (i.e., Trib. 0302, 0304, 0305, 0323, and possibly 0303). In other streams (e.g.. Trib. 0303 and 0310), steep gradients preclude fish use. Steep gradients also reduce fish use in the perennial systems (except for Trib. 0328). Habitat is in various stages of degradation in these systems; pools are being filled and gravels and debris shift regularly. In Tributary 0328 (Peterson Creek), however. habitat diversity is extensive, and the channel is not seriously degraded. At this location the field team observed at least three species of salmonoids. In general, the most diverse and least disturbed habitat in a tributary system occurs in • the large wetland areas in the southeast third of the basin. Usable habitat for anadromous fish is found in the low-gradient portions of streams where channels cross the Cedar River Valley floor. In these reaches, however, only spawning habitat is likely to be available, as the pools and woody debris necessary for successful rearing either do not exist or are quite limited. Excellent spawning and rearing areas exist where pools and riffles are extensive, instream cover and bank vegetation are intact. and diversity of habitat types is abundant. B. Effects of Urbanization in the Basin Flooding, erosion, and the degradation of habitat associated with development in the Lower Cedar River Basin are most apparent where development has eliminated vege- tation along the edges of the valley and where stormwater has been routed down channels and swales. The removal of veg ed etation, such as trees, above and below the ,le s of valley walls, as well as the discharging of stormwater over the valley wall, has resulted in tension cracks and landslides that are endangering some houses. The sedi- ments from these failures are depositing in streams and on valley floors and damaging fish habitat and private property. Discharging stormwater from increased impervious areas into steep tributary channels and swales is seriously destabilizing channels and valley walls; this in turn results in channel downcutting, bank erosion, and landslides. The sediments from these problems often degrade fish habitat and settle out on pri- vate property along the valley floor. Two serious instances of development-related erosion occurred during the November 1936 storm: 1) culverts rerouting the stream were plugged, causing the formation of a new channel that destroyed portions of roads on Tributary 0314; and 2) new, uncom- P:LC 4 Lower Cedar River Basin (continued) • pacted fill adjacent to new residences near collection point 5 was w during the storm, causing landsliding and gullying. washed partly away Future problems will be similar to these, as commercial and residential developments increase flow rates and volumes by decreasing natural storage and infiltration. This is expected to occur if wetlands on the upper plateau are encroached upon or lost (e.g., on Trib. 0304 at RM 2.30 and on Trib. 0304A at Rm 1.60). The preservation of wetlands and streambank vegetation and the attenuation of storm this basin. flows are essential in G Specific Problems Identified The steep valley sideslopes through which streams pass and the often dense upland development result in a number of similar problems that repeat themselves throughout the Lower Cedar River Basin. The most significant of these are outlined and discussed below. 1- Drainage and flooding problems are often the result of several conditions: a. Undersized culverts and inadequate entrance structures_ The most notable area is on Tributary 0306 at river mile .30, where a culvert here was blocked by debris carried downstream by the stream and caused erosion and flooding of Fairwood Golf Course. The blockage was compounded by the fact that the culvert was undersized; the problem will worsen as flows • increase from upstream development. b. Serious instream erosion and subsequent downstream have been caused by three main fagctors: 1) from ii sedimentation. These developments on the bluffs above the valley, 2) compacted pastureland due to livestock, and 3) runoff from impervious areas originating at gravel pits. These problems will continue and worsen until mitigative measures are taken. (See Appendix C for specific examples.) c. Undersized rechannelized streams_ Tributaries on the valley floor are too small to carry the increased flows originating in developed residential areas along the top of the bluffs. For example, Tributary 0302 at river mile .25. the channel along Maplewood Golf Course, overtops and floods during storms. d- Construction in wetland and floodplain areas, Many of the wetlands on the south side of the Cedar River are peat bogs, and roads built through them continue to settle each year, increasing g the amount of floodin on the road. For example, the road crossing with Tributary 0323B north of Lake Desire will experience more severe flooding as the road settles. e- Discharging of stormwater at the top of steep banks. At river mile 2.20 on the Cedar River, a trailer park (constructed on the edge of the cliff) discharges its drainage down the valley wall. Increased flows erode the steep valley, depositing sediments on the valley floor, blocking channels and causing flooding. These problems will eventually stabilize, but only after a • large quantity of soil has been eroded. P:LC 5 Lower Cedar River Basin (continued) 2- Damage to property is being caused by three factors: a. Landslides and potential landslides. Landslides are accelerated by the removal of vegetation on steep slopes in preparation for residential construction and/or by the routing of storm flows over hillslopes. For example, a large landslide has already occurred in the front yard of a resi- dence on the Cedar River at river mile 7.80. b. Sedimentation (from landslides). Sedimentation and channel and bank ero- sion are damaging private property along the valley floor (Trio. 0299 and 0310). C. Flooding during storms Flooding has been brought on by the effects of development and associated changes to the natural draina-e systems in the basin. (See "B" above.) o 3. Destruction of habitat is being caused by four conditipns: a- Sedimentation of pools and riffles and cementing of gravels. These problems, the result of severe erosion and the transport of bedload material, have been caused by upland developments in the basin and the presence of associated impervious surfaces, which increase the rate and quantity of surface runoff. Sedimentation and cementing of gravels in streambeds destroy natural spawning and rearing habitat. On Tributary • 0307 at river mile .40 and Tributary 0305 at river miles .95, 1.20, and 1.70, . recent high flows have eroded the streambed at least one foot, contributing to a serious siltation problem downstream. Heavy bedload transport is evi- dent in all systems of the basin except Tributary 0328. In Tributary 0303 at river mile .25, fine sediments are accumulating in gravels that may be used by resident fish. In Tributary 0304 between river miles .95 and 1.20. pools are being filled by sands and gravels and rearing habitat is being rapidly lost. b- Channclization of stream beds. Loss of habitat through channelization has occurred in all the major streams of the basin, but most noticeably in those reaches that cross the valley floor. These reaches lack habitat diversity. reducing fish use for spawning and rearing. Channelization has damaged or destroyed. habitat in several reaches that were once heavily used by fish: these include Tributary 0302 between river mile .30 and 40. Tributary 0304 between river miles .05 and .18, Tributary 0305 between river mile .20 and .75, and Tributary 0328 from river mile 1.10 to 1.40. These systems cannot afford a further reduction of habitat and still remain viable fishery resour- ces. C. The accumulation of trash in stream beds This problem occurs in close proximity to residential areas. Trash degrades water quality and is visually unpleasant. Tires, appliances, furniture, and other trash have been thrown into Tributary 0302 at river miles 1.00 and 1.10 and in Tributary 0303 at river mile .35. • P:LC 6 Lower Cedar River Basin (continued) • d- Wetland encroachment. Encroachment destroys habitat and eliminates natural water filtration and storage for surface runoff. Examples of this problem were observed on Tributary 0304 at river mile 2.30. Tributary 0308 at .80, and Tributary 0304A at river mile 1.80. Many wetlands have already been completely lost through filling, for example on Tributary 0306A at river mile .55. Suspected violations were forwarded to Building and Land Development for enforcement. N. RECOMMENDATIONS FOR ACTION The primary recommendations for action in the Lower Cedar River Basin addresses current severe problems related to erosion, habitat destruction, and flooding. Prevention of these problems will be accomplished by controlling locations and densities of new development and providing adequate R/D facilities for stormwater. A. Reduce landslide hazards by: 1. Including sensitive areas not previously mapped on the Sensitive Areas Map Folio (SAMF)_ See Appendix C for a full listing of sensitive areas. 2- Establishing building setbacks along cliffs and native growth protection easements along steep ravines. 3. Discouraging or eliminating the routing of stormwater over cliffs, unless adequate tightline systems can be constructed to convey flows in a safe, nonerosive manner • to the bottom of cliffs. 4. Decreasing peak flows by constructing larger R/D facilities to lessen the landslide and erosion occurrence along tributary slopes. B. Reduce erosion and flooding in the basin by improving surface water management: 1. Direct the Facilities Management Section of the Surface Water Management Division to evaluate existing storm-detention and conveyance facilities to deter- mine whether they are properly sized to meet current standards. Evaluation should begin with all single-orifice R/D facilities. 2- Consider areas other than wetlands as regional storm-detention facilities. Tributary 0300 at river mile .42 is the site for a proposed.dam, for example. 3. Utilize existing lower quality. wetlands (those rated other than #1) as regional storm-detention facilities. Wetlands 3102 and 3142 could provide more live storage, for example. 4. Review channel and culvert capacity for conveying existing and future runoff, and establish floodplain areas in regions of slight gradient for existing and future runoff conditions. 5. Promote the infiltration of surface water through the use of retention facilities and open channels instead of pipes where the soil and slope conditions permit. • Collection points 5. 6, and 12 on plateaus have such soil conditions. P:LC 7 Lower Cedar River Basin (continued) • a. On Tributary 0304: Clean streambed gravels, add habitat and bed-control weirs, and plant bank vegetation for shade. b. On Tributary 0305: Construct a new channel and move stream from road- side channel to its new location on adjacent lands. Implement a full restoration project to provide channel meanders, habitat structures, pool/riffle enhancement, streambed gravel replacement, and revegetation. c- On Tributary 0303: Move stream from present channel to a location further north, away from the roadside. If relocation is not possible, these minimum steps should be taken: Add habitat structure to existing channel with root masses, deflectors, boulder clusters, and other features; revegetate channel banks with shrubs and small trees; enhance stream crossings with bottomless pipe arches. d. On Tributary 0328 (Peterson Creek): Add habitat structure by replacing the straight, shortened channel with a more natural, meandering one; place habitat structures (such as root masses, deflectors, cover logs and boulder clusters) throughout the channel; and revegetate banks with shrubs common to adjacent riparian zones (salmonberry, ninebark, or dogwood, for example). 3. Protect the Peterson Creek system (Tn-b. 0328) in its present, near-pristine state_ This will include not only the restoration outlined in section A above, but also the adoption of land use management regulations to prevent future habitat • destruction: a• Protect all existing wetlands within the subcatchments of Peterson Creek_ Employ wetland buffers at least 100 feet wide without exception. b. Restrict development in the critical headwater area (drainage, habitat, water quality) bounded by Lake Desire, Otter Lake, and Peterson Lake to rural densities. C. Designate and protect stn:amside management zones of at least 100 feet from the ordinary high-water mark (OHWM) along the main stem of the creek. Use 25 feet from the OHWM on tributaries. d- Preserve floodplains and their forests for dynamic retention of sediments and water. e- Restrict vegetation removal in streamside/wetland management zones. f_ Size R/D facilities to store the 100-year storm at a two-to-five-year release rate. Use the two-cell type of pond with a forebay, a gravel filter, and a vegetated swale outflow where feasible. g. Regulate more closely all septic tank and drain45eld installations, as well as maintenance schedules, particularly in the Lake Desire, Otter Lake. and Peterson Lake drainage areas. P:LC 9 Lower Cedar River Basin (continued) h- Work with the State Department of Ecology to establish minimum stream_ flow requirements for Peterson Creek and Lake Desire tributary. 4- Develop and promote public education and involvement programs for basin awareness. Work with schools, environmental groups, and the civic and business communities to conduct educational and restoration programs. P:LC 10 Trib. R Collect. Existing Item Rive, r Mile Point Category Prop, prof. ate Condit ons and Problems ConditAnticitiions and Problems Recommendations 5 0299 RM 12.1 18 Geology Horse farm in uplands has Continued high erosion and Develop R/D at horse farm created extensive imper- sedimentation. to attenuate peak flows: vious surfaces, resulting See Project 3115, in channel scour, bank erosion, landslides, and sedimentation at mouth of basin. Residence overcome with sediment. 6 -- 13 Geology Landslide terrain for sale Site of future mass erosion. Prohibit development here. by realtots. High risk for Notify Building and Land landslides, flooding (from Development. Add area to springs). SAMF. 7 7 Geology Large-scale landsides g Natural process. None. adjacent to Cedar River due to springs and cutting of toeslopes by streams. Appears to be natural. g O Geology Gullying in valley wall Y g Y , Unknown. None. possibly from natural springs. 9 -- 14 Geology Landslide debris flow from Existing tension cracks residence on SE 147th Pl., indicate future instability. ttrrees and shruevegetate bs. with Renton. P: LC.APC C-2 MM M.C�` 3 10 r- ni MIKE 0.10JR-MA �1.1.tss Ali �.. ,� ,< �• ..�: .�'� �,r� �, � �. ♦l�ma+raaa�r. • Y rtl� 1�� \ �11�� � i'?.�_ � _ ncmia `"�B�' � ��°,�� ►.E7 -- t--MMmas A lamplol1i1/Z� k .[� r_ .�f 1 7R�1 ,a n?FaVl' d �=fl E � ^OJIfq�O Mt g �r. � .. b ,�v'� ,lam:: - � ".�i'�,�� , ,�� ����� /✓ �,�'--•-•-e, d�.ssis�iTl �Ilel��tial 1 � ,L� �iA' � ` ' `'4�a '�;:-•/ar"�`OW' LEA NI�T.�U►.�s.i �.p B � \ �_ p cam. �sgjry:�r714s fP" to �� o .�. �lsllll� 1 r `� PUN ME slum mum ; \�,, .lo.� _ • `�' spy, *rv+ , , • n�v _` I �••»J �� ,��� �,+•�� ;+•fir, rr '`!� �� 11 � � sue• \�� �}� yid p � ��' � �'l �lo01s �tinew �, �, qc: Ong MO -milli ingggg. . P41. �• � � I :��l1l1!!11lO8:1 {,� I SF4� '" °`� ,ram ,;° '`- 1 '� 5�,���►� ' ?� " 1 " O s_mrws �i CW4 Py� rae_„U¢au./•Ne�18u� i. F' EWA � CAk'F47:/1� C / r will WR Aw >R17YYdY(Ii►I �FA►g Emu®Pd�,x'a�a'+ter�►:gg� 'rY�/H+n.l the f �.. Its r 6W1 ��999Kc, 0 4.0 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN 4.1 Existing Site Hydrology The project site is 10.35 acres in size. The surface topography slopes from southeast to northwest at an average slope of approximately 5 percent. The elevation of the southeast corner of the site, the high point, is approximately elevation 400 and the southwest corner of the site, the low point, is approximately elevation 377. The topography of the site is rolling with small areas having slopes up to 30 percent. The existing site is undeveloped and the majority of the site is covered with a young,second growth of mixed deciduous trees. Only a few scattered evergreen trees exist on the site. The groundcover understory includes ferns, blackberries, and other low growth vegetation. The SCS Soils Maps indicate that the on-site soils are Indianola loamy fine sand(InC),classified as outwash soils by Table 3.2.2.13 in the 1998 King County Surface Water Design Manual(KCSWDM). A site-specific soils analysis has been completed by Geotech Consultants and their reports are included in Section 6.0 of this TIR. The Geotech Consultants investigations revealed a layer of topsoil over gravelly sand across the site. The northwest portion of the site has been filled in the past with a mixture of soil,concrete rubble,construction debris,and household garbage. Drainage crosses the site as overland sheetflow in a southeast to northwest direction. Drainage leaves the site as overland sheetflow and enters the tightline drainage system along Beacon Way S.E. Refer to Section 3.0 of this TIR for the downstream drainage system analysis. 4.2 Developed Site Hydrology 1 The subject property will be developed as single-family subdivision consisting of 50 lots with public streets having curb,gutter, and sidewalk. A standard series of catch basins and underground storm drainage pipes will collect and convey drainage from the developed areas and convey the drainage to Tract A at the northwest corner of the site. Each lot will be provided with a rooftop infiltration system that will be equipped with an emergency overflow connection to the storm drainage system. Each lot will be provided with a roof drain stubout for this overflow connection. The Tract A drainage facility will consist of a basic wet pond for water quality treatment followed by an infiltration pond. The basic wet pond has been sized for the developed areas of the site excluding the rooftops that will be handled by the individual lot roof infiltration systems. The infiltration pond has been conservatively sized without credit for the rooftop infiltration systems. This approach allows infiltration distributed over the site. The infiltration pond is sized for the 100- year developed runoff for the entire site using KCRTS. The basic wet pond, which is sized for 60 percent of the 2-year storm, sizing includes the streets, driveways, and front yards, but not the rooftops because they are going into the rooftop infiltration trenches. The design infiltration rate for the pond has been determined based upon field measured infiltration rates and safety factor requirements contained in the 1998 KCSWDM. A portion of the roadway at the northwest corner of the site is too low to drain into the infiltration pond, and therefore will be served by an infiltration trench preceded by an oil/water separator vault. 4.3 Tract A Infiltration Pond Sizing 7797.006[RJA/jss/ca] • W • 4.3 TRACT A INFILTRATION POND SIZING 4.3 Tract A Infiltration Pond Sizing The Tract A infiltration pond has been designed according to the 1998 KCSWDM. The total site area tributary to the Tract A pond is 9.82 acres. In order to be conservative,we have assumed the entire lot areas are tributary to the pond for sizing calculations without giving any credit for the rooftop infiltration systems that will be provided for each lot. The impervious coverage of streets, sidewalks,open ponds,and driveway tracts have been measured from the construction plan layout. The impervious coverage of houses and driveways on the lots have been estimated according to the maximum impervious coverage permitted by code. This complies with the 1998 KCSWDM (page 3-27). The City of Renton development code states that the maximum building coverage for the R8 zone is,5&percent. For sizing calculations,we have assumed 70 percent impervious area on lots to account for the driveway and patio in addition to the 50 percent maximum building coverage. The calculations of impervious area tributary to the Tract A pond are as follows: Total Basin Area = 9.821 Acres tp% � Impervious Area: a Roads, Sidewalks,Pond, and Driveway Tracts = 2.166 Acres 50 Lots: 6.891 Acres xo l�iq ""' = 4.824 Acres 9 LOOU 51`/l6t A Gr"y� -7 S4(11 46.u4 Total Impervious Area = 6.990 Acres .l Pervious Area = 9.821 Acres - 6.99 Acres = 2.831 Acres The developed site runoff has been calculated using the areas shown above with a 100-year KCRTS model according to the 1998 KCSWDM. The other component of the infiltration pond design is the infiltration rate to used. The 1998 KCSWDM(page 5-54)for measured infiltration rates requires field testing of infiltration rates. This was done by Geotech Consultants with a number of test pits within the pond area that ranged from faster than 1 inch per minute to the slowest test pit having a rate of 0.25 inches per minute. The Geotech Consultants report dated November 17,200?2,recommends using a measured infiltration rate of 0.25 inches per minute. The 1998 KCSWDM(pages 5-54 and 5-55)for design infiltration rate uses an equation. We have coordinated with Geotech Consultants on this as follows: Imeasured = 0.25 inches per minute -' Ftesting = 0.30(EPA method used) Fgeometry = 1.00(no groundwater) ✓ Fplugging = 0.90(medium sands) Idesign = 0.25 x 0.30 x 1.0 x 0.9 = 0.0675 inches per minute The 1998 KCSWDM (page 5-55) for 100year overflow conveyance requires• an additional correction factor of 0.5 if the downstream overflow route does not have capacity to convey the 100- year developed peak flow. Therefore,the design infiltration rate is adjusted as follows: 7797.006[RJA/jss/ca] Idesign = 0.0675 minutes per inch x 0.5 = 0.0338 inches per minute (this equals • 29.63 minutes per inch) Given this design criteria,the pond sizing requirements are met by an infiltration pond having a depth of 5 feet,a bottom area of 9,373 square feet,and 2:1 side slopes. • 7797.006[RJA/jss/ca] _F ► AL sFSPK_S • KCRTS Program.-File Directory: C:\KC SWDM\KC DATA\ [C] CREATE a new Time Series ST 0.00 0.00 0.000000 Till Forest 0.00 0.00 0,000000 Till Pasture 0.00 0.00 0.000000 Till Grass 0.00 0.00 0.000000 Outwash Forest 0.00 0.00 0.000000 Outwash Pasture -- ,2.83 0.00 0.000000 Outwash Grass 4-- 0.00 0.00 0.000000 Wetland --- o 6.99 0.00 0.000000 Impervious 7797-POST.tsf T 1,00000 T • FsT - D eV PEA4e-s • Flow Frequency Analysis Time Series File:7797-pos.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- FlowRate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 1.79 6 2/09/01 2:00 3.51 1 100.00 0.990 1.50 8 1/05/02 16:00 2.54 2 25.00 0.960 2.15 3 2/27/03 7:00 2. 15 3 10.00 0. 900 1.74 7 8/26/04 2:00 2.07 4 5.00 0.800 2.07 4 10/28/04 16:00 1.82 5 3.00 0.667 1.82 5 1/18/06 16:00 1.79 6 2.00 0.500 2.54 2 10/26/06 0:00 1.74 7 1.30 0.231 3.51 1 1/09/08 6: 00 1.50 8 1.10 0.091 Computed Peaks 3.18 50.00 0.980 I NH LJ%--j uN Fo-t\jb 6-A�'s • Retention/Detention Facility Type of Facility: Infiltration Pond Side Slope: 2.00 H:1V Pond Bottom Length: 136.92 ft Pond Bottom Width: 68.46 ft Pond Bottom Area: 9374. sq. ft Top Area at 1 ft. FB: 14879. sq. ft 0.342 acres Effective Storage Depth: 5. 00 ft Stage 0 Elevation: 386.00 ft Vat.UAA/ - Storage Volume: 57803. cu. ft fir---- ��Q O_ 1.327 ac-ft U_ VOL = 631 %? G� -- Vertical Permeability: 30.00 min/in Permeable Surfaces: Bottom & Sides Riser Head: 5.00 ft Riser Diameter: 12.00 inches Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation Surf Area (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) (sq. ft) 0.00 386.00 0. 0.000 0.000 0.00 9374. 0.10 386.10 942. 0.022 0.000 0.44 9456. 0.20 386.20 1891. 0.043 0.010 0.44 9538. • 0.30 386.30 2849. 0.065 0.000 0.45 9621. 0.40 386.40 3816. 0.088 0.000 0.45 9705. 0.50 386.50 4790. 0.110 0.000 0.45 9788. 0.60 386. 60 5773. 0. 133 0.000 0.46 9872. 0.70 386.70 6765. 0.155 0.000 0.46 9956. 0.80 386.80 7765. 0.178 0.000 0.46 10041. 0.90 386.90 8773. 0.201 0.000 0.47 10126. 1.00 387. 00 9790. 0.225 0.000 0.47 10211. 1.10 387.10 10815. 0.248 0.000 0.48 10297. 1.20 387.20 11849. 0.272 0.000 0.48 10382. 1.30 387.30 12892. 0.296 0.000 0.48 10469. 1.40 387.40 13943. 0.320 0.000 0.49 10555. 1.50 387.50 15003. 0.344 0.000 0.49 10642. 1.60 387.60 16071. 0.369 0.000 0.50 10729. 1.70 387.70 17148. 0.394 0.000 0.50 10816. 1.80 387. 80 18234. 0.419 0.000 0.50 10904. 1.90 387.90 19329. 0.444 0.000 0.51 10992. 2.00 388.00 20433. 0.469 0.000 0.51 11081. 2.10 388.10 21545. 0.495 0.000 0.52 11169. 2.20 388.20 22667. 0.520 0.000 0.52 11258. 2.30 388.30 23797. 0.546 0.000 0.53 11348. 2.40 388.40 24936. 0.572 0.000 0.53 11437. 2.50 388.50 26084. 0.599 0.000 0.53 11527. 2.60 388.60 27242. 0.625 0.000 0.54 11618. 2.70 388.70 28408. 0.652 0.000 0.54 11708. 2.80 388.80 29583. 0.679 0.000 0.55 11799. 2.90 388.90 30768. 0.706 0.000 0.55 11891. 3.00 389.00 31961. 0.734 0.000 0.55 11982. •` 3.10 389.10 33164. 0.761 0.000 0.56 12074. • 3.20 389.20 34376. 0.789 0. 000 0.56 12166. 3.30 389.30 35598. 0.817 0. 000 0. 57 12259. 3.40 389.40 36828. 0.845 0.000 0.57 12352. 3.50 389.50 38068. 0.874 0.000 0.58 12445. 3.60 389.60 39317. 0.903 0.000 0.58 12538. 3.70 389.70 40576. 0.931 0.000 0.58 12632. 3. 80 389. 80 41843. 0.961 0. 000 0. 59 12726. 3. 90 389. 90 43121. 0.990 0. 000 0.59 12821. 4.00 390.00 44408. 1.019 0. 000 0. 60 12916. 4.10 390.10 45704. 1.049 0. 000 0. 60 13011. 4.20 390.20 47010. 1.079 0.000 0.61 13106. 4.30 390.30 48325. 1.109 0.000 0. 61 13202. 4.40 390.40 49650. 1.140 0. 000 0.62 13298. 4.50 390.50 50985. 1.170 0. 000 0.62 13394. 4.60 390.60 52329. 1.201 0. 000 0. 62 13491. 4.70 390.70 53683. 1.232 0.000 0.63 13588. 4.80 390.80 55047. 1.264 0.000 0. 63 13685. 4.90 390.90 56420. 1.295 0.000 0.64 13783. 5.00 391.00 57803. 1.327 0.000 0.64 13881. -5".10 391.10 59196. 1.359 0.308 0.65 13979. 5.20 391.20 60599. 1.391 0. 871 0.65 14078. 5.30 391.30 62012. 1.424 1.600 0.66 14177. 5.40 391.40 63435. 1.456 2.390 0.66 14276. 5.50 391.50 64867. 1.489 2.670 0.67 14376. 5.60 391.60 66310. 1.522 2.930 0.67 14476. 5.70 391.70 67762. 1.556 3.160 0.67 14576. 5.80 391.80 69225. 1.589 3.380 0.68 14677. • 5.90 391.90 70698. 1.623 3.590 0.68 14777, 6.00 392.00 72181. 1.657 3.780 0.69 14879. 6.10 392.10 73674. 1.691 3.970 0.69 14980. 6.20 392.20 75177. 1.726 4. 140 0.70 15082. 6.30 392.30 76690. 1.761 4.310 0.70 15184. 6.40 392.40 78214. 1.796 4.470 0.71 15287. 6.50 392.50 79747. 1.831 4.630 0.71 15389. 6.60 392.60 81291. 1.866 4.780 0.72 15493. 6.70 392.70 82846. 1.902 4.930 0.72 15596. 6.80 392.80 84411. 1.938 5.070 0.73 15700. 6.90 392.90 85986. 1.974 5.210 0.73 15804. 7.00 393.00 87571. 2.010 5.350 0.74 15908. Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) 1 3.51 0.00 0.04 5.01 391.01 58000. 1.332 2 2.54 ******* 0.00 1.94 387.94 19794. 0.454 3 2.15 ******* 0.00 2. 81 388.81 29721. 0.682 4 2.07 ******* 0.00 1.96 387.96 20041. 0.460 5 1.82 ******* 0.00 3.65 389.65 40007. 0. 918 6 1.79 ******* 0.00 4.06 390.06 45194. 1.038 7 1.74 ******* 0.00 1.24 387.24 12302. 0.282 8 1.50 ******* 0.00 1.08 387.08 10631. 0.244 ---------------------------------- Route Time Series through Facility Inflow Time Series File:7797-pos.tsf Outflow Time Series File:rdout.tsf • Inflow/Outflow Analysis 3.2.2 KCRTS/RUNOFF FILES METHOD—GENERATING TIME SERIES • All onsite,predevelopment forest/shrub cover and all offsite forest/shrub cover is defined as"forest," • irrespective of age. Post-development onsite land use is defined as forested only if forested areas are in a sensitive area buffer or are otherwise protected and will have a minimum 80%canopy cover within 5 years. In urban areas,unprotected onsite forest cover should be treated as either pasture or grass in the post-development analysis. In rural areas,unprotected forest cover should be assumed 50%grass,50%pasture. • The HSPF grass parameters were developed by the USGS study of regional hydrology and have generally been interpreted as providing the hydrologic response for"urban"grasslands(lawns,etc.), which have relatively low infiltration rates and are drained effectively. The HSPF"pasture" parameters were developed by King County DNR to provide a hydrologic response intermediate to the USGS forest and grass parameters,as might be typified by ungrazed or lightly grazed pasture with good grass cover. Because it is impossible to adequately control grassland management after development,all post-development grassland should be modeled as"grass" (with the exception of unprotected forest in rural development as noted above). All predevelopment grassland should be modeled as"pasture"except for redevelopment of areas with predevelopment land use densities of 4 DU/GA or greater(which are modeled as grass). 0. / C� CALCULATION OF IMPERVIOUS AREA °,p^d Gouor�e .SO ,I cr �on�� cc, d 2 . 70 Total Impervious Coverage CorSpr�w(;J� } 0Se- 70% 'µ�perdi�,rS }o c �covnd- r- d r.%leWof ur%A A+;p. Table 3.2.2.D(p.3-28) lists percent impe ious coverage for use in KCRTS analysis of existing I residential areas. The tabulated figures a useful in offsite analysis that includes large developed residential areas,making a detailed s ey of impervious coverage impractical. Impervious covera osed sidenti d commercial development must be estimated for each •, specific pro . Impervious coverage of streets,sidewa s,hard su ace trai s,etc., s a I be taken from layouts of the proposal. House/driveway or building coverage shall be as follows: • For urban residential development, the assumed impervious coverage shall not be less than 4,000 square feet per lot or the maximum impervious coverage permitted by code(K.C.C.21 A.12.030), whichever is less. • For rural residential development,the assumed impervious coverage shall not be less than 8,000 square feet per lot or the maximum impervious coverage permitted by code, whichever is less. • For commercial or multi-family development,impervious coverage shall be estimated from layouts of the proposal. Effective Impervious Area The net hydrologic response of an impervious area depends on whether that area is effectively connected (usually by pipes or a channel) to a storm drainage system. The impervious area that the user inputs to KCRTS is the"Effective Impervious Area"(EIA),the total impervious area multiplied by the effective impervious fraction (see Table 3.2.2.E, p. 3-28). Non-effective impervious area (i.e.,total impervious area less EIA)is assumed to have the same hydrologic response as the immediately surrounding pervious area. For example, for existing residential areas with rooftops draining to splash pads on lawns or landscaping,the non-effective portion of the roof areas would be treated as pasture for predevelopment conditions (if DU/GA<4.0)and grass for post-development conditions. Note: Credits for inf Itration/dispersion of downspouts on individual lots in proposed single family residential subdivisions are applied separately on a site-specific basis(see Note 3, Table 3.2.2.E). The effective impervious fraction can be selected from Table 3.2.2.E or determined from detailed site surveys. With the exception of figures for compacted gravel and dirt roads and parking lots,the figures in Table 3.2.2.E are average figures cited by the USGS (Dinicola, 1990). 1998 Surface Water Design Manual 9/l/98 3-27 SECTION 5.4 INFILTRATION FACILITIES the infiltration facility, and at least one test hole should reach the water table. If the water table is very • deep, the test hole need not extend more than one-fourth the maximum width of the pond below the bottom of a pond,or more than 5 feet below the bottom of a tank. If there is any question about the actual wet-season water table elevation,measurements shall be made during the period when the water level is expected to be at a maximum. Any requirements related to steep slope,landslide hazard,or other sensitive area impacts should also be addressed in the soil study. The geotechnical engineer shall provide a report stating whether the site is suitable for the proposed infiltration facility,and shall recommend a design infiltration rate(see 'Design Infiltration Rate" below). I� MEASURED INFILTRATION RATES Infiltration rate tests are used to help estimate the maximum sub-surface vertical infiltration rate of the soil below a proposed infiltration facility (e.g.,pond or tank)or a closed depression. The tests are intended to simulate the physical process that will occur when the facility is in operation;therefore, a saturation period is required to approximate the soil moisture conditions that may exist prior to the onset of a major winter runoff event. �Se �.ZS 11Ae-S �1��— M'nd� &r �TcoT�G� Co�cJ � ti Testing Procedure �eror-+ ka��/ of• 17, -2-boo 1. Excavations shall be made to the bottom elevation of the proposed infiltration facility. The measured infiltration rate of the underlying soil shall be determined using either the EPA falling head_ percolation test rp ocedure(Design Manual- Onsite Wastewater Treatment and Disposal Systems, EPA, 1980)or the double ring infiltrometer test(ASTM D3385). • 2. The test hole or apparatus shall be filled with water and maintained at depths above the test elevation for the saturation periods specified for the appropriate test. 3. Following the saturation period,the rate shall be determined in accordance with the specified test procedures, with a head of 6 inches of water. 4. The engineer shall perform sufficient tests to determine a representative infiltration rate for the site, but at least three tests shall be performed for each proposed infiltration facility site, and at least 2 tests per acre(minimum of 4 tests) shall be performed for a closed depression. 5. A minimum of two soils logs shall be obtained for each tank and for each 10,000 square feet(plan view area) of proposed pond infiltration surface area. Soils shall be logged for a minimum of 5 feet below the bottom of each proposed infiltration facility. The logs shall describe the SCS series of the soil, indicate the textural class of the soil horizons throughout the depth of the log,note any evidence of high groundwater level (such as mottling),and estimate the maximum groundwater elevation,if ` within the limits of the log. a DESIGN INFILTRATION RAT E TE In the past,many infiltration facilities have been built which have not performed as the designer intended. This has resulted in flooding and substantial public expenditures to correct problems. Monitoring of actual facility performance has shown that the full-scale infiltration rate is far lower than the rate determined by small-scale testing. Actual measured facility rates of 10%of the small-scale test rate have been seen. It is clear that great conservatism in the selection of design rates is needed,particularly where conditions are less than ideal. Ideally, the design infiltration rate will be determined using an analytical groundwater model to investigate the effects of the local hydrologic conditions on facility performance, but this may be excessively costly for small projects. • A simplified method may be used for determining the design infiltration rate by applying correction factors to the measured infiltration rate. The correction factors account for uncertainties in testing,depth to the water table or impervious strata,infiltration receptor geometry, and long-term reductions in permeability 911198 1998 Surface Water Design Manual 5-54 5.4.1 GENERAL REQUIREMENTS FOR INFILTRATION FACILITIES due to biological activity and accumulation of fines. Equation 5-9 has been developed to account for these factors. This equation estimates the maximum design infiltration rate(Ide,ign); additional reduction in rate • beyond that produced by the equation may be appropriate. Note that the design infiltration rate Ide,ign must not exceed 20 'nches/h u . � r o.2s M„ '0-30)( ►-0) (0.1) = o .o67s ►�. M A ]design = ]measured X Resting X Fgeomern•X Fplugging ^ ' [� 1^ (5-9) Correction factor Fre,ting accounts for uncertainties in the testing methods. For the PA method,Fre,ring 30 for the ASTM D3385 method,Fre,ri,,g=0.50 Fgeo,ne113. accounts for the influence of facility geometry and depth to the water table or impervious strata on the actual infiltration rate. A shallow water table or impervious layer will reduce the effective infiltration rate of a large pond, but this will not be reflected in a small scale test. Clearly,a large pond built over a thin pervious stratum with a shallow water table will not function as well as the same pond built over a thick pervious stratum with a deep water table. Fgeomer,). must be between 0.25 and 1.0 as determined by e following equation Fgeamern•=4 DIW+0.05 (5-10) where D = depth from the bottom of the proposed facility to the maximum wet-season water table or nearest impervious layer,whichever is less W = width of the facility Fplagging accounts for reductions in infiltration rates over the long term due to plugging of soils. This factor is: • • 0.7 for loams and sandy loams • 0.8 for fine sands and loamy sands • 0.9 for medium sand • 1.0 for coarse sands or cobbles,or any soil type in an infiltration facility preceded by a water quality facility. U/100-YEAR OVERFLOW CONVEYANCE An overflow route shall be identified for stormwater flows that overtop the facility when infiltration capacity is exceeded or the facility becomes plugged and fails. The overflow route must be able to safely convey the 100-year developed peak flow to the downstream conveyance system or other acceptable discharge point in accordance with conveyance requirements in Section 1.2.4. The requirement to identify and analyze a 100-year overflow pathway may be waived if(1)an additional correction factornf 0 5 is used in ca a atmg life design m titration rate, (2)the facility is sized to fully infiltrate the 100-year runoff event,and (3)the facility is not bermed on any side. Intent: to address situations where the infiltration facility may be a highly permeable closed depression,such as a gravel pit, where all stormwater is infiltrated. (0. 0675 p.S� = D. 033 8 ❑ SPILL CONTROL DEVICE -Z.q .63 All infiltration facilities must have a spill control device upstream of the facility to capture oil or other floatable contaminants before they enter the infiltration facility (see Section 4.2.1.1). If a tee section is used, the top of the riser should be set above the 100-year overflow elevation to prevent oils from entering • the infiltration facility. 1998 Surface Water Design Manual , 9/1/98 5-55 • i DEVELOPMENT STANDARDS FOR SINGLE FAMILY RESIDENTIAL ZONING DESIGNATIONS A N (Primary and Attached Accessory Structures) p ww BUILDING STANDARDS:... Maximum Building 2 stories and 30 ft.13 2 stories and30 ft, 13 2 stories and 30 ft. 13 2 stories and 30 ft. 1 Height11 and Number of Stories, except for uses having a "Public Suffix" (P) designation14 Maximum Height for See RMC 4-4-140G. See RMC 4-4-140G. See RMC 4-4-140G. See RMC 4-4-140G. Wireless Communication F e Maximum Building 2% for lots 5 acres or more. 35%. 35%. C Coverage o N 1 50%— Lots 5,000 50%— Lots 5,000 sq. ft. or less. (including primary an 5 acres. less. o accessory buildings 35%for lots 10,000 sq. ft. or less. On lots greater than 1 acre, an additional 5% of the total area may be used for agri- cultural buildings related to practices. EXCEPTIONS °= Pre-Existing Legal Lots Nothing herein shall be M Nothing herein shall be Nothing herein shall be de J Nothing herein shall be determined determined prohibit ' p hibit the determined to prohibit the termined to prohibit the con- to prohibit the construction of a single construction of a single fam- construction of a single struction of 1 single family family dwelling and its accessory ily dwelling and its accessory family dwelling and its dwelling and its accessory buildings on a pre-existing legal lot buildings on a pre-existing accessory buildings on a buildings on any substan- provided that all setback, lot cover- legal lot provided that all set- pre-existing legal lot pro- dard pre-existing legal lot, age, height limits and parking backs, lot coverage, height vided that all setbacks, lot provided that all setback, lot requirements for this Zone can be limits and parking require- coverage, height limits and coverage, height limits, satisfied. ments for this Zone can be parking requirements for sewer, and parking require- satisfied. this Zone can be satisfied. ments can be met. Conflicts:See RMC 4-1.080. t • 4.4 TRACT A WET POND SIZING • 4.4 Tract A Wet Pond Sizing As previously discussed,rooftop infiltration systems will be provided on each lot. The wet pond will receive drainage from the roads,curbs,sidewalks,driveway tracts,individual lot driveways, and front yards. The wet pond will receive drainage from 115,695 square` feet of impervious surface and 114,563 square feet of lawn(outwash grass). The basic wet pond requires a volume factor f=3.0. The rainfall r for the mean annual storm is 0.039 feet per Figure 6.4.LA of the 1998 KCSWDM. a,l. - 7797.006[RJA/jss/ca] Wetpond Sizing Worksheet Summary of the 1998 Surface Water Design Manual Requirements Project Name: Project Number: Step 1) Determine volume factor f. Basic size............................................. f= 3 Largesize............................................. f= 4.5 Step 2) Determine rainfall R for mean annual Storm Detemine rainfall R for mean annual storm Rainfall................................................. 0.039 (feet) Step 3) Calculate runoff from mean annual storm Vr= (0.9A;+ 0.25A�9 +0.10Atf+ 0.01 Ao9) X R A;=tributary area of impervious surface 115,695 (sf) Ate =tributary area of till grass 0 (sf) Att=tributary area of till forest 0 (sf) A09 =tributary area of outwash grass 114,563 (sf) R = rainfall from mean annual storm 0.039 (feet) Vr=Volume of runoff from mean annual storm 4,106 (cf) • Step 4) Calculate wetpool Volume Vb =fV, f=Volume Factor 3 Vb= Volume runoff, mean annual atorm 4,106 (cf) Vr=Volume of the wetpool 12,317 (cf) Step 5) Determine wetpool dimensions a) Determine geometry of first cell Volume in first cell 4,671 (cf) Depth h 1st cell (minus sed. Storage) 4 (feet) Determine horizontal xs area at mid-depth using 1,167 (sf) A mid= Vol. 1 st cell/h Mid-width 23 (feet) Mid-length 50 (feet) Determine xs area at surface Z= Side slope length ( 3H:1 V) 3:01 3:1 recommended 2(h/2 x Z) = 12 (feet) Dimensions of top of pond adjusted for geometrics •� Top width 35 (feet) 7797.008.xls[DED/ca] • Top length 62 (feet) Area of Top 2194 (feet) b) Determine geometry of second cell Volume in second cell 8,715 (cf) Depth h 2nd cell 5 (feet) Determine xs area at mid-depth using 1,743 (sf) A mid=Vol. 2nd cell/h Mid-width 26 (feet) Mid-length 63 (feet) Determine horizontal xs area at surface Z= Side slope length (3H:1 V) 3:01 3:1 recommended 2(h/2 x Z) = 12 (feet) Dimensions of top of pond adjusted for geometrics Top width 38 (feet) Top length 75 (feet) Area of Top 2850 (feet) Adjustment to cells (If necessary) • Geometry check: Overall pond L:W at mid-depth =3:1 Pond width (mid-depth) 26 Cell 1 length (mid-depth) 50 Cell 2 length (mid-depth) 63 Pond Length (mid-depth) = Cell 1 +Cell 2 113 L mid : W mid= 4.36 Total Wetpond Surface area required= 5,044 Total Wetpond Bottom area required = 1,142 7797.008.xls[DED/ca] 6.4.1 WETPONDS—BASIC AND LARGE—METHODS OFANALYSIS FIGURE 6.4.1-A PRECIPITATION FOR MEAN ANNUAL STORM IN INCHES(FEET) • ST 1.0/ ST 1.1 ST 1 0 LA 0.8 LA. 0.9 1 0 LA 1.2 j i. e ♦ q i X,i .' F-F '- -���• F s Elliott i .t1+,`F ..rt r ♦r I ,� . s r ,Y .1 ////�'� ,. F •fq s� —r 5'`rY lyr.�.�,r ass o��f S ! �• \ � r a n 'teA soamd 0.54 (0.045' ) t!YRC! COOMti \ � t 0.47" (0.039') j Incorporated Area _c= River/Lake 0.4 7" — Major Road (0.0391 ) ) NOTE:Areas east of the easternmost isoplw (0.043' 0.65" ial should use 0.65 (0.054' ) inches unless rainfall data is available for the location of interest (0.0471) 24 The mean annual stone is a conceptual storm found by dividing the annual precipitation by the total number of storm events per year result,generates large amounts of runoff. For this application,till soil types include Buckley and bedrock soils,and alluvial and outwash soils that have a seasonally high water table or are underlain at a shallow depth(less than 5 feet)by glacial till. U.S. Soil Conservation Service(SCS)hydrologic soil • groups that are classified as till soils include a few B,most C,and all D soils. See Chapter 3 for classification of specific SCS soil types. 1998 Surface Water Design Manual 9/1/98 6-69� • 4.5 TRACT A INFILTRATION TRENCH SIZING I ►� L . � Ill- v T�►'u`� 15�t_s • KCRTS Program..File Directory: C:\KC SWDM\KC DATA\ [C] CREATE a new Time Series ST 0.00 0.00 0,000000 Till Forest 0.00 0.00 0.000000 Till Pasture 0.00 0.00 0.000000 Till Grass 0.00 0.00 0.000000 Outwash Forest 0.00 0.00 0.000000 Outwash Pasture a 0.28 0.00 0.000000 Outwash Grass f- 0.00 0.00 0.000000 Wetland —>0.22 0.00 0.000000 Impervious e, — 7797-DEV.tsf T 1.00000 • • I"FI L- . T1eeNz M — PocST'- DSv i c.zw • Flow Frequency Analysis Time Series File:7797-dev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- FlowRate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.062 5 2/09/01 2:00 --i0.125 1 100. 00da- 0.990 0.047 8 1/05/02 16:00 0.081 2 25.00 0.960 0.077 3 2/27/03 7:00 0.077 3 10.00 0.900 0.055 7 8/26/04 2:00 0.066 4 5.00 0.800 0.066 4 10/28/04 16:00 0.062 5 3.00 0.667 0.058 6 1/18/06 16:00 0.058 6 2.00 0.500 0.081 2 10/26/06 0:00 0.055 7 1.30 0.231 0.125 1 1/09/08 6:00 0.047 8 1.10 0. 091 Computed Peaks 0. 110 50.00 0.980 1 • DIES(c7N ma's • ' Retention/Detention Facility Type of Facility: Gravel Infiltration Trench Facility Length: 62.00 ft Facility Width: 10.00 ft Facility Area: 620. sq. ft 4Q Effective Storage Depth: 5. 00 ft �1 D�� = 62-b SF Stage 0 Elevation: 373. 00 ft Storage Volume: 930. cu. ft Vertical Permeability: 15.00 min/in Permeable Surfaces: Bottom Riser Head: 5.00 ft Riser Diameter: 12.00 inches Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) 0.00 373.00 0. 0.000 0.000 0.00 0.06 373.06 11. 0.000 0.000 0.06 0.16 373.16 30. 0.001 0.000 0.06 0.26 373.26 48. 0.001 0.000 0.06 0.36 373.36 67. 0.002 0.000 0.06 0.46 373.46 86. 0.002 0.000 0.06 0.56 373.56 104. 0.002 0.010 0. 06 0.66 373.66 123. 0.003 0.000 0.06 0.76 373.76 141. 0.003 0.000 0.06 0.86 373.86 160. 0.004 0.000 0.06 0.96 373.96 179. 0.004 0.000 0.06 1. 06 374.06 197. 0.005 0.000 0.06 1. 16 374. 16 216. 0.005 0.000 0.06 1.26 374.26 234. 0.005 0.000 0.06 1.36 374.36 253. 0.006 0.000 0.06 1.46 374.46 272. 0.006 0.000 0.06 1.56 374.56 290. 0.007 0.000 0.06 1.66 374.66 309. 0.007 0.000 0.06 1.76 374.76 327. 0.008 0.000 0.06 1.86 374.86 346. 0.008 0.000 0.06 1.96 374.96 365. 0.008 0.000 0.06 2.06 375.06 383. 0.009 0.000 0.06 2.16 375. 16 402. 0. 009 0.000 0.06 2.26 375.26 420. 0.010 0.000 0.06 2.36 375.36 439. 0. 010 0.000 0.06 2.46 375.46 458. 0.011 0.000 0.06 2.56 375.56 476. 0.011 0.000 0.06 2.66 375.66 495. 0.011 0.000 0.06 2.76 375.76 513. 0. 012 0.000 0.06 2.86 375. 86 532. 0.012 0.000 0.06 2.96 375. 96 551. 0. 013 0.000 0.06 3.06 376.06 569. 0.013 0.000 0.06 3.16 376.16 588. 0.013 0.000 0.06 3.26 376.26 606. 0.014 0.000 0.06 3.36 376.36 625. 0. 014 0.000 0.06 3.46 376.46 644. 0. 015 0.000 0.06 • 3.56 376.56 662, 0.015 0. 000 0.06 3. 66 376.66 681. 0.016 0.000 0.06 3.76 376.76 699. 0.016 0.000 0.06 3. 86 376.86 718. 0. 016 0.000 0. 06 3. 96 376. 96 737. 0.017 0. 000 0.06 4. 06 377.06 755. 0. 017 0. 000 0.06 4. 16 377.16 774. 0.018 0.000 0.06 4.26 377.26 792. 0.018 0.000 0.06 4.36 377.36 811. 0.019 0.000 0.06 4.46 377.46 830. 0.019 0.000 0. 06 4.56 377.56 848. 0.019 0. 000 0.06 4. 66 377.66 867. 0.020 0. 000 0.06 4.76 377.76 885. 0.020 0. 000 0.06 4. 86 377.86 904. 0.021 0.000 0.06 4.96 377.96 923. 0.021 0.000 0.06 5. 00 378.00 930. 0.021 0. 000 0. 06 5. 10 378. 10 930. 0.021 0.308 0.06 5.20 378.20 930. 0.021 0.871 0.06 5.30 378.30 930. 0.021 1.600 0.06 5.40 378.40 930. 0.021 2.390 0.06 5.50 378.50 930. 0.021 2.670 0.06 5.60 378.60 930. 0.021 2. 930 0.06 5.70 378.70 930. 0.021 3.160 0. 06 5. 80 378.80 930. 0.021 3.380 0.06 5. 90 378.90 930. 0.021 3.590 0.06 6.00 379.00 930. 0.021 3.780 0.06 6.10 379.10 930. 0.021 3.970 0.06 6.20 379.20 930. 0.021 4.140 0.06 6.30 379.30 930. 0.021 4.310 0.06 6.40 379.40 930. 0.021 4.470 0.06 6.50 379.50 930. 0.021 4.630 0.06 6.60 379.60 930. 0.021 4.780 0.06 6.70 379.70 930. 0.021 4.930 0.06 6. 80 379.80 930. 0.021 5. 070 0.06 6.90 379.90 930. 0.021 5.210 0.06 7. 00 380.00 930. 0.021 5.350 0.06 Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) 1 0.12 0.00 0.00 4.93 377.93 918. 0.021 2 0.08 ******* 0.00 0.50 373.50 93. 0.002 3 0.08 ******* 0.00 0.43 373.43 81. 0.002 4 0.07 ******* 0.00 0.21 373.21 40. 0.001 5 0.06 ******* 0.00 0.14 373.14 26. 0.001 6 0.06 ******* 0.00 0.06 373.06 11. 0.000 7 0.06 ******* 0.00 0.05 373.05 9. 0.000 8 0.05 ******* 0.00 0.04 373.04 8. 0.000 Route Time Series through Facility Inflow Time Series File:7797-dev.tsf Outflow Time Series File:rdout Inflow/Outflow Analysis Peak Inflow Discharge: 0.125 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.000 CFS at 10:00 on Jan 9 in Year 8 Peak Reservoir Stage: 4.93 Ft STORMCEPTOR CALCULATIONS StnrmceptoCW Sizing Proymn •� ..... iati3.00 Selected Rainfall Statiun Particle Size Distribution ............ Stcstc. VdASHINGTOhi Diem.(urn) l Percent(f) Val.(ills) Name ,_E a"f TLE TAr_OMA INTL fiF' E~.leu.(ft) 40G3 .._........20...._............._i ..... 20 _U 001.�.............. . Latitude N 47 dog 27 min 6Q....._..._....... '.. 24 ..._..........._0.0051 _l cngiUrdo.. YY 1?2 deg_l_8 min...._..................................... 15D ?0 t1.0354 .......... _...... ............................................, ' 400 20 0?123 Site Parzt,tnatats _....... 2000 20 0.941 Total Area(ac) .5 Wrperiousness{` } 44. �tY:pt-PnitltS.Htw�+��ci 22 ...._........._................................. _.... ... ............................_........_.............. ..................._• Starrrrceptor Sizing Table __..._............................................. Sit,rmer✓ptur Model eo Fkunaff T rt3ated . ........ 6. ....__.... ....... f3� _.._ ., 97.4 91.2 STt;9i.10 ....._...., 99 9 94.9 _.................... ............................................ -..-STC.1200 .95.2 STG 1800 99.9 STC 2400 1 DD.O 96.7 STC 3600 l OD.O........_..........-... 97 0 `T-C 4800 1 UOA 97.8 ...................................._....... STC6000.____ ............................................................... .. 97.8 STC 7200 i ......................100:�......._..._................!,. 98-4 STC 11000 100 D 98.9 _.................__ ..._............ ............................... ; STCt 30D0 100.0_ _.......... ...._._........................;................._...... .. 99.0 STC 16000 104 0 C ornments Sizing prepared for Don Dawes 9 Be.rghausen Consulting Engineers Inc.Kent WA 425.251.6222 FA};8782.The site is also in Kent and is 0.5 ac.of which 0.22 ec.ie impervious.King County WQ treated flow is 0.058 eha.The STC 450i will tiew 0.20 cfs prior to bypass,80V TSS removal is exceeded. I Conservattvety.the pervious areas are assumed to be frozen from Nov.-Mar.to nnGcipets increased runoff from saturated soils. ZO ' d Ztletl 6t,L £OS -tagw� I zC� io0 b8Z =OI ZO--bZ-uEC' temp.out STQRM{EPTOR HYDROLOGY SIMULATION PROGRAM VERSION 3.0 1-his program reads local 15 minute data and simulates runoff for the period of record to determine the % of annual runoff treated and % of annual TSS removed by the Stormccpror SEATTLE TAC[Mx IWTL AP Latitude ~ w 47 deg 27 min Longitude = m 122 deg 18 min Elevation = 195. Feet or 59.4 meters Rainfall records from 196S to 1999 Site Parameters Total Drainage Area (ac 0.50 Total Imperviousness �� ' � 44 0U Overland Flom width ( -t) 2''5 Overland Slope {�) ' 2O impervious Depression Storage {inches} 0.020 Pervious Depression ' epres� on Storage (inches) 0.200 Impervious Mannings n 8Ol5 Pervious mannfngs n Q`2S infiltration Parameters \ *orton infiltration Used Initial (max) Infiltration Rate { n'/hr) 2'44O0DFinal Mn) Infiltration Rate in'/' r) 0^40000Infiltration DeCay Rate (l/sec) v~v»vnzInfiltration Regeneration Rote) 0.01000 :o infiltration During Winter months Chosen No infiltration for the months November through February Daily evaporation (in./hr) 0. 100 sediment build-up reduces the storage volume for settling calculations _ maintenance cycle of IZ months was cho�en (The �r ormcep�or will 6a cleaned c -- ----' - �_ -- ou every 12 months) TSS Loading calculations Buildup / Washnff Loading chosen Buildup wa3huff allocates more washoff in the rising limb of the hydrOgraph Tar �Buildup Event Mean concentration (mg/1) 125 u /oup Exponent ' 00.4OO / Page I Em ' d ZtZtp 6tL E09 q.Aaqumej �C>I-A«»o V6Z ;0I Z0-VZ-uer washo[f Exponent temp.outD.200 xvuflability Factors for Particles >= 400. um ; vai7ability = A + 8i^[ A = 0.057 0.040 � = rainfall intensity [ = 1.100 Slormwater particle Size Distribution Table Diameter Percent specific Gravity Settling velocity {um] (m/s) 20.0 20.0 1.90 0.0004 60.0 2O.O 1.80 0.00I6 150.0 20,0 2.20 0.0108 4VO.0 20,0 2'65 0.0647 2000.0 20'0 2.65 0'2870 Flncculativc settling assumed for particles <= 28 um Rainfall period from 1965 to 1999 Total rainfall period of 35 years Total rainfall = 3294I'7 mm 1296.9 in Average annual rainfall = 941.2 mm 37.1 in Rainfall event analysis Z.O hour inter event time used to determine # of events < in. Events 74 Vol (in.) yS 0.25 7020 82.9 455. 35.1 0. 50 907 I0.7 323. 24.9 0.75 280 9.3 170' 13.1 I.00 107 1.3 93' 7.2 1.25 55 0'6 62. 4'8 1. 60 37 0'4 51, 3.9 1.75 25 0,3 41. ].Z 2.00 lZ 0.1 22. 1.7 2. 2S 5 0.1 Il' 0.6 2.50 8 0.1 15. l,I 2.75 6 0.1 16' 1.2 3.00 5 0.1 15. 1.1 3.25 l D^O 3. 0.3 3'50 l 0'0 3' 0.3 3' 75 I 0.0 4. 0'9 4.00 l 0.0 4. 0.3 4.25 0 0.8 O. 0.0 4' 5O l 0.0 4' 0,3 4.75 l 0.0 5. 8.4 5.00 O 0.0 O. 0'0 5,25 0 0.0 O, 0.0 5' 50 O 0.0 Q. 0.0 E.75 D 0.0 0. 0.0 6.00 O O'O D. 0.0 6. 25 O D'O 0. O'O Page 2 VO ' d ZVZV 6tp/- EOS 4-Aaqwia-j �C>I�Aoo V60 :01 OO-VZ-uTer temp.out 6.50 0 0.0 0. 0.0 6,75 0 0.0 0. 0.0 7.00 0 0.0 0. 0.0 7.25 0 0.0 0. 0.0 7.50 0 0.0 0. 0.0 7.75 0 0.0 0. 0.0 8,00 0 0.0 0. 0.0 8.25 0 0.0 0. 0.0 8.25 0 010 0. 0.0 ,. o ta'; rain in inches 1297, Number of rain events 8471 Rainfall intensity analysis Average intensity = 0.16 in/hr < in/hr number % vol (in.) % 0.25 2661.4 82.4 678. 52. 3 0. 50 4270 1.3.2 374. 28.8 0.75 1018 3.2 152. 11.7 1-00 272 0.8 58. 4. 5 1.25 59 0.2 16. 1.3 1. 50 29 0.1 10. 0.8 1.75 1:3 0.0 5 . 0.4 2.00 5 0.0 2. 0.2 2.25 2 0.0 1. 0.1. 2.50 0 0.0 0. 0.0 2.75 ] 0.0 , 0.0 3.00 0 0.0 0. 0.0 3.25 0 0.0 0. 0.0 3. 50 0 0.0 0. 0.0 3.75 0 0.0 0. 0.0 4.00 0 0.0 0. 0.0 4.25 0 0.0 0. 0.0 4. 50 0 0.0 0. 0.0 4,75 0 5.00 0 0.0 0. 0.0 5.25 0 0.0 �.o o. 0.0 5.50 0 0.0 0. 0.0 5.75 0 0.0 0. 0.0 6.00 0 0.0 0. 0.0 6.25 0 0.0 0. 0.0 6.50 0 0.0 0. 0.0 6.75 0.0 0. ;.00 0 0.0 0. 0.0 7.25 0 0.0 0. 0.0 7. 50 0 0.0 0. 0.0 7.75 0 0.0 0. 0.0 8.00 0 0.0 0. 0.0 8.25 0 0.0 0. 0.0 8.25 0 0.0 0. 0.0 ;catal rainfall 1296.9 in. 32941.7 mm Total evaporation = 138.6 in. 3520.1 mm Total infiltration 314.8 in. 7996.9 mm AD Rainfall as runoff M 67.4 % •\! Page 3 90- d ZtIZtr 6tbL COS q.Aagw�el iC>"ao VO£: OI ZO-VZ-ujeC temp.out Average Event Mean concentration for TSS (mg/1) 122.7 TS'S, Removal simulation Results Table StorwicTor Treated Q % Runoff Tank TSS Overall TSS mode (cfs) Treated Removal M Removal (In) 450 0.28 97.4 91.3 91.2 900 0.64 99.9 94.9 94.9 .1200 0.64 99.9 95.2 95.2 1800 0.64 99,9 95.4 95.4 2400 1.06 100.0 96.7 96,7 3600 1.00 100.0 97.0 97.0 4800 1. 77 100.0 97.8 97.8 6000 1. 77 100.0 97.9 97.9 7200 2.47 100.0 98.4 98.4 11000 3. 53 100.0 98.9 98.9 13000 3. 53 100.0 99.0 9910 16000 4.94 100.0 99.2 99,2 HydrolOgy Table VOIUMe of Runoff Treated vs By-pass Flow Rate Treated Q Treated Vol over, Vol Tot Vol % Treated (cfs) (ft3) (ft3) (ft3) 0.04 845110. 741229. 1586072. 53.3 0.14 1402210. 183948, 1586072. 88.4 0. 32 1557223. 28849. 1586072. 98.2 0. 57 1582898. 3173. 1586072. 99.8 0.88 1-585746. 327. 1586072. 100.0 1.27 1586072. 0. 1586072. 100.0 1.73 1586072. 0. 1586072. 100.0 2.26 1586072. 0. 1586072. 100.0 2.86 1,586072. 0. 1586072. 100.0 3. 53 1586072. 0. 1586072. 10010 4.27 1586072. 0. 1586072. 100.0 5.09 1586072. 0. 1586072. 100.0 5,97 1586072. 0. 1586072. 100.0 6.92 1,586072. 0. 1586072. 100.0 7.95 1.586072. 0. 1586072. 100.0 9.04 1,586072. 0. 1586072. 100.0 10.21 1586072. 0. 1586072. 100.0 11.44 1,586072. 0. 1586072, 100.0 12.75 1.586072. 0. 1586072. 100.0 14.13 1586072. 0. 1586072. 100.0 15. 57 1586072. 0. 1586072. 100.0 17.09 1,586072. 0. 1586072. 100.0 18.68 1586072. 0. 1586072. 100.0 20- 34 1586072. 0. 1586072. 100.0 22.07 1586072. 0. 1586072. 100.0 23.87 1.586072. 0. 1586072. 100.0 25.74 1586072. 0. 1586072. 100.0 27.69 1586072, 0. 1586072. 100.0 29. 70 1,586072. 0. 1586072. 100.0 31.78 1586072. 0. 1586072. 100.0 Page 4 90 - d otrztp 6t'L Cos q.Aaqwe-j ,CNN Aoo v0c: 01 zo-ve-Upc DR. BY: E.J. JACKSON Hydro ConduitAR N .5. XAT : QWG4 A400-CE-99 'OVER GM TE f .. GRADE ADJl1S'i ERS M t. SUIT FINISHED GRACE E 5'iGRIKEPi£R'# l INlz -LRT z w f ,�,, ► ` � � t t;i.�,", ilT1�t'£�Er ,:4wy <: 1? A 31 PP 4( 1e �.rw.___,_ ��++ }jF /f "w4a P k"" Y?G.. I Ai i 1 V U'LE IMWIN PIPE RISER PIPE lF 14 48 1.4 NEEDED ( i S 12*0 INLET DOWN aw . iQTH U PLAN-VIEW, .NOT-E- 'rlE USE OF F.MBLE CONNECTIONS IS RECOMMENDE0 THE INLET AND o#;. rLEr wERF- APpuc-Aax- 2. THE COVER SHOW) BE POSMONED, OVS THE CLEAN0IlJ7/ VENT PIPE. t, THIS IS A GENERAL ARRANGUEENT DRAWING CONSULT LOCAL REPftMMATK FOR SPECIAL. CONDMONS, s LO 'd eVOV 6VL £OS �.taquu�e� iC�.toO VIC = 0I ZO-vZ-UL>p Stormeeptor a LI Hydro January 1, 2001 Conduit Effective imn-iediately, the prices prior' to shipping for the StOrmrel)tor c products are a.9 fo llows: Model No. -price ST(I' 450i $4,650 STC 900 $8,072 STC 1200 $9,620 STC 1800 $11,475 STC 2400 $14,835 STC 3600 $17,735 STC 4800 $22,960 STC 6000 $27,425 •\ STC 7200 $35,640 STC 11000 $40,000 STC 13000 $50,000 STIC 16000 $65,000 F.O.-B. the Tualatin, Oregon or Everett. Washington Plants. Includes concrete"s"ect.ions, top and bottom slabs, reducing slabs (if nc,cessary),fiberglass insert, gaskets, lubricant, c-ast iron frame & cover. Kor-N-Seal boots (where applicable) and grade rings. '* Rf�quires Multiple Truckloads to Deliver. NY''Area M'.k-.t;. %-Tgr. Corky Lambert Cellular 503.702,0939 (local to Portland) or Home Office 503.7491523 StorniceptorKan % 8,18 City 800.909.7763 E-M ail. clambert@csraxoni Website: www.csrstormeept-()i,.com Tualatin, Oregon (local) 503.692.3885 or Toll-free 800.648-6609 Everett, Washington (local) 42115.355.2111 or Toll-ftee 800-355,27711 ZVZV 6VL COS VEC :O-E 00-tPZ • • e • • 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN Enclosed are calculations necessary for sizing the conveyance system for the project. The rational method and Mannings formula were used for sizing each of the pipes. The conveyance pipes have been sized to accommodate the 100-year storm event at full flow condition, pursuant to Section 1.2.4.1 of the 1998 KCWSWDM. The intent of this pipe system within public roadways is to convey stormwater runoff from the houses and roads into the drainage facility located in Tract A. 5.1 25-Year Conveyance A 25-year conveyance analysis has been completed in accordance with the 1998 King County Surface Water Design Manual providing conveyance for the 100-year/24-hour storm. For ease in making these calculations,we have utilized the rational method as defined by the 1998 King County Surface Water Design Manual for this task. Tributary areas have been calculated to each of the catch basins connected to the proposed piping system and precipitation has been derived from the Renton/Seattle IDS curve. An average "C" factor was calculated for each tributary area, that will be utilized for these calculations. 7797.006[RJA/jss/ca] BARGHAUSEN CONSULTING ENGINEERS-PIPE FLOW CALCULATOR using the Rational Method 8 Manning Formula KING COUNTY DESIGN FOR 100 YEAR STORM JOB NAME: NOTE:ENTER DEFAULTS AND STORM DATA BEFORE BEGINNING JOB#: DEFAULTS C= 0.7 n= 0.012 REVISED: d= 121 Tc= 6.3 A=Contributing Area(Ac) Qd=Design Flow(cfs) COEFFICIENTS FOR THE RATIONAL METHOD"Ir"-EQUATION C=Runoff Coefficient Clf=Full Capacity Flow(cfs) STORM Ar Br Tc=Time of Concentration(min) Vd=Velocity at Design Flow(fps) 2YR 1.58 0.58 1=Intensity at Tc(in/hr) Vt=Velocity at Full Flow(fps) 10YR 2.44 0.64 PRECIP= 3.9 d=Diameter of Pipe(In) s=Slope of pipe(%) 25YR 2.66 0.65 2.61 L=Length of Pipe(ft) n=Manning Roughness Coefficient 50YR 2.75 0.65 0.63 D=Water Depth at Qd(in) Tt=Travel Time at Val(min) 100YR 2.61 0.63 FROM TO A s L d Tc n C SUM A A'C SUM A'C I Qd Qf Qd/Qf D/d D Vf Vd Tt CB21 CB20 0.38 1.57 7 12 6.3 0.012 0.7 0.382 0.27 0.27 3.19 0.85 4.83 0.177 0.281 3.38 6.16 4.63 0.03 CB20 C819 0.10 1.12 107 12 6.3 0.012 0.7 0.482 0.07 0.34 3.18 1.07 4.08 0.263 0.351 4.21 5.20 4.39 0.41 CB19 CB17 0.68 3.11 195 12 6.7 0.012 0.7 1.162 0.48 0.81 3.06 2.49 6.80 0.368 0.417 5.01 8.67 8.00 0.41 CB17 CB15 0.79 3.11 175 12 7.1 0.012 0.7 1.952 0.55 1.37 2.95 4.03 6.80 0.593 0.553 6.63 8.67 9.01 0.32 C815 CB13 0.63 4.04 122 12 7.5 0.012 0.7 2.582 0.44 1.81 2.87 6.19 7.76 0.669 0.598 7.17 9.88 10.56 0.19 CB13 CB11A 0.26 1.49 201 18 7.7 0.012 0.7 2.842 0.18 1.99 2.82 5.62 13.89 0.405 0.443 7.97 7.86 7.46 0.46 CB11A C810 0.49 4.27 221 18 6.1 0.012 0.7 3.332 0.34 2.33 2.72 6.35 23.51 0.270 0.356 6.41 13.31 11.32 0.33 CB32 CB31 0.19 4.96 107 12 6.3 0.012 0.7 0.19 0.13 0.13 3.19 0.42 8.59 0,049 0.153 1.83 10.95 5.62 0.32 CB31 CB30 0.56 5.13 39 12 6.6 0.012 0.7 0.75 0.39 0.53 3.10 1.62 8.74 0.186 0.289 3.47 11.14 8.47 0.08 CB30 CB29 0.47 1A6 90 12 6.7 0.012 0.7 1.22 0.33 0.85 3.07 2.62 5.26 0.499 0.499 5.99 6.71 6.74 0.22 CB29 CB28 0.24 0.50 30 15 6.9 0.012 0.7 1.46 0.17 1.02 3.01 3.08 4.96 0.622 0.581 8.71 4.03 4.28 0.12 CB28 CB26 0.23 4.20 85 15 7.0 0.012 0.7 1.69 0.16 1.18 2.98 3.52 14.34 0.246 0.337 5.05 11.69 9.66 0.15 CB26 CB25 0.19 4.54 112 15 7.2 0.012 0.7 1.88 0.13 1.32 2.94 3.87 14.91 0.260 0.348 5.21 12.16 10.21 0.18 CB25 CB23 1,20 2.58 79 15 7.4 0.012 0.7 3.08 0.84 2.16 2.89 6.24 11.24 0.555 0.532 7.97 9.16 9.38 0.14 CB23 CB11 0.39 2.00 40 15 7.5 0.012 0.7 3.47 0.27 2.43 2.86 6.95 9.89 0.702 0.618 9.27 8.07 8.75 0.08 CBi1 CB10 0.19 2.00 31 15 7.6 0.012 0.7 3.66 ' 0.13 2.56 2.84 7.28 9.89 0,736 0.638 9.56 8.07 8.83 0.06 CB10 CB7 0.18 1.45 179 18 8.4 0.012 0.7 0.18 0.13 5.02 2.66 13.34 13.70 0.974 0.794 14.29 7.76 8.77 0.34 CB7 CB6 0.88 1.00 18 24 8.8 0.012 0.7 1.06 0.62 5.64 2.59 14.61 24.50 0.596 0.555 13.32 7.80 8.13 0.04 CB6 POND 0.00 1.00 29 24 8.8 0.012 0.7 1.06 0.00 5.64 2.59 14.57 24.50 0.596 0.554 13.30 7.80 8.12 0.06 C822 CB19 0.52 3.77 71 12 6.3 0.012 0.7 0.52 0.36 0.36 3.19 1.16 7.49 0,155 0.264 3.17 9.55 6.89 0.17 CB18 CB17 0.24 0.50 31 12 6.3 0.012 0.7 0.24 0.17 0.17 3.19 0.54 2.73 0.197 0.297 3.57 3.48 2.68 0.19 CB16 CB15 0.11 0.50 31 12 6.3 0.012 0.7 0.11 0.08 0.08 3.19 0.25 2.73 0.090 0.200 2.40 3.48 2.10 0.25 CB12 CB11A 0.21 0.50 31 12 6.3 0.012 0.7 0.21 0.16 0.16 3.19 0.47 2.73 0.172 0.278 3.33 3.48 2.60 0.20 CB27 CB26 0.11 0.50 31 12 6.3 0.012 0.7 0.11 0.08 0.08 3.19 0.25 2.73 0.090 0.200 2.40 3.48 2.10 0.25 CB24 C823 0.24 0.50 31 12 6.3 0.012 0.7 0.24 0.17 0.17 3.19 0.54 2.73 0.197 0.297 3.57 3.48 2.68 0.19 CB9 CB8 0.67 5.60 80 12 6.3 0.012 0.7 0.67 0.47 0.47 3.19 1.50 9.13 0.164 0.271 3.25 11.63 8.55 0.16 CB8 CB7 0.12 0.50 31 12 6.5 0.012 0.7 0.79 0.08 0.55 3.14 1.74 2.73 0.637 0.586 7.04 3.48 3.70 0.14 CB1 C62 0.27 0.50 34 12 6.3 0.012 0.7 0.27 0.19 0.19 3.19 0.60 2.73 0.221 0.317 3.80 3.48 2.79 0.20 CB2 INFIL. 0.22 0.50 21 12 6.5 0.012 0.7 0.49 0.15 0.34 3.13 1.07 2.73 0,393 0.436 5.23 3.48 3.27 0A1 Page 1 rxfwuc .vcr: vim w1c am swe vwvn sv.a: S. ,roe rro: co. PPP—SS—TTTT CITY OF o .� RENTON PIPE SUNG BASH AREA MAP Planninq/Bu(Winq/Publfc Works Dept NO. RMON By DATE dAPPR HOUAGE FVM HlL PUT i it rl � I , A_ 1 i 11 "I fo II I �♦� I i i i i' i' 1 W �� ♦♦�� ��� ��l i i j i t ♦♦♦ . � ii gyp{ if�� ♦♦ ' II11 C� '1 1 / ♦♦ �a / ' I 1, I, 1 \``��A ♦�♦♦ `, .__ 'ii li A it it ♦♦♦ i� `'� 1♦\• / PARK litili 1!I�fi V ♦ I 1 i T tA /- ``�``_1♦/ i I AA ■ {�I IIII 1'1 I v • , 1, ■WM � . I flll 1 �, ,1 Illg � : I ■ co co Z - g --- 1 . ---.-- - SA, . m _J �� ' ■ --- -- .. _ ■ ` II IIII . ; ' ♦••�/ ... ■■......... ��• .■... ■ .♦ D p O y; N 1 I 1 I g ...►� W r..... flGg N C�� i N N" i j II^ W II i j N I I I I I � PFff70 F � "� 88ggNNggNggggggyggggggggggggSgggggggggg D 38la; i LSf� � � tDOoVOf V1 � AAW N -' m ooa � � oA�NN71A�j►�.�`W vVj goAAV p��Nr"tA�� j V ��1jNW OO (O� O(O��Op V �j �Yc SNca �♦QW � ����N �Oi �i��� � � NV � V�Np �+ ��p ��p ��p�(Vp�p � �DpD��p � � �l ��lll � ®p T aa�oCoy �i11 'iltA'ii + T71 "11 'i1Z1i171 'T1 W ��♦� � m 7"0•° OOOOOOOrr0000o0000000000000000000000 a � � c, Mi nnnAnnnnnnnnt7nnnnnnnnnnnnn� nn m pi= q = , Oil1 N Q � -� Ell 9 ' B.C.E. JOB NO. 7727 Fle: \SDSKPROJ\7797\engineerin9\7797--l.d.g Dote/T—01/12/2002 13:50 Scale: 1-50 ddorae%refs: 0797-t.z7797- 7797-br, t a, 0 6.0 SPECIAL REPORTS AND STUDIES 1 6.1 Results of Subsurface Infiltration Testing by Geotech Consultants dated November 17,2000 6.2 Results of Test Pits for Fill Exploration by Geotech Consultants dated November 9,2000 6.3 Geotechnical Engineering Study by Geotech Consultants dated September 14, 1999 6.4 Phase 1 Environmental Site Assessment by Geotech Consultants dated September 9, 1999 6.5 Abandoned Mine Assessment by Hart Crowser dated August 23, 1999 7797.006[RJA/jss/ca] 6.1 RESULTS OF SUBSURFACE INFILTRATION TESTING BY GEOTECH CONSULTANTS DATED NOVEMBER 17, 2000 ` T q-I- • November 17, 2000 Bennett Corporation JN 99330 9 Lake Bellevue Drive, Suite 204 Bellevue, Washington 98005 Attention: Chris Austin via facsimile: (425) 709-6553 Subject: Results of Subsurface Infiltration Testing Heritage Renton Hill Project Southeast Corner of Beacon Way South and South 7th Court Renton, Washington Dear Mr. Austin: We have previously prepared a geotechnical engineering study for the above-referenced site dated September 14, 1999. An infiltration pond to be located in the northwestern corner of the property has been proposed for the disposal of storm water from the development. This letter summarizes the findings of our most recent explorations and subsurface infiltration testing in the area of the proposed storm water pond. • We were provided with a drainage control plan prepared by Peterson Consulting Engineers, dated April 2, 2000. This plan shows the preliminary layout of the 57 lots on the property. Based on this plan, we anticipate that the infiltration pond will have a bottom elevation of 349.5 feet, with a 200- foot-long biofiltration Swale bordering the south and east perimeter of the pond. At its present proposed location, cuts to reach the pond bottom range from 12 to 17 feet. The subsurface conditions were explored by excavating eight test pits at the approximate locations shown on the attached copy of the pond layout. The test pits were excavated on October 19 and November 3, 2000, with a track-mounted backhoe. A geotechnical engineer from our staff observed the excavation process, logged the test pits, conducted infiltration tests in the native soils, and obtained representative soil samples. The logs of the test pits are attached to this letter. The test pits generally encountered loose sands that became denser with depth. As illustrated by the grain size analyses contained in Appendix A, the native sands contain a low percentage of fines (particles smaller than the U.S. No. 200 sieve). Test Pits B through H encountered varying depths of loose, silty sand fill containing asphalt and concrete debris, and assorted household garbage. The depth of this fill ranged from 3 feet in Test Pit B to at least 15 feet in Test Pit D, which was excavated where the ground surface is highest in the center of the proposed pond. The soils encountered in our recent subsurface investigation are similar to those found during our geotechnical engineering study in September of 1999. No groundwater seepage or wet soils were observed in the test pits. Test Pits F through H were excavated to an approximate elevation of 344 to 345 feet. The test pits were conducted following • the end of a relatively dry summer. GEOTECH CONSULTANTS, INC. Bennett Corporation JN 99330 November 17, 2000 Page 2 • INFILTRATION TESTS Falling head infiltration tests were performed in Test Pits E, G, and H with a 6-inch-diameter PVC pipe driven into native soil near, or slightly below, the likely bottom-of-pond elevation. We also conducted infiltration tests in the native sands found below the fill in Test Pit C, although the test was conducted approximately 4 feet above the proposed pond bottom. It was not possible to conduct infiltration tests in the center of the pond area, as the higher existing ground elevation, and the caving conditions in the fill soils made entering such a deep test pit unsafe. The infiltration tests were conducted in general accordance with the King County Surface Water Design Manual. After soaking the underlying soils, each test was performed three times, with an average falling head infiltration rate taken over a 6-inch drop in the water surface. The following table summarizes the average infiltration test rates that resulted from our testing: JTEST PIT DEPTH • • INFILTRATION TEST,feet RATE,inches/minute B U 0.23 E 12 4.5 G 13 0.26 H 14 8.2 CONCLUSIONS AND RECOMMENDATIONS • Based on the results of our subsurface investigation and infiltration tests, we recommend using an average test infiltration rate of 0.25 inches per minute. While this rate is substantially lower than the results for the tests in Test Pits E and H, it should be conservative and more appropriate to account for inherent variability in results of subsurface infiltration tests. The King County Surface Water Design Manual includes additional influence factors to account for the configuration of the infiltration structure and the tendency of soil to clog with silt and debris carried into the system. Over time, the infiltration capability of the soil close to the system will decrease, reducing the effectiveness of the system's infiltration. The effective life of the system can be lengthened by frequent cleaning of the catch basins that collect the runoff. Homeowners should also be notified of the sensitivity of the system so that they can minimize the amount of soil and debris that is flushed into the catch basins. Periodic maintenance, such as scraping the clogged soil from the bottom of the pond should be expected. The fill soils found in the eastern end of the pond area are not suitable for infiltration. However, it appears that the proposed bottom-of-pond elevation will be near the transition from fill to native soils found in our test pits. It is possible, however, that overexcavation will be necessary to remove fill remaining once the pond has been excavated to its planned elevation. • GEOTECH CONSULTANTS, INC. Bennett Corporation JN 99330 November 17, 2000 Page 3 • We trust that this report meets your immediate needs for the proposed development. Please contact us if we can be of further service. Respectfully submitted, GEOTECH CONSULTANTS, INC. g. McG waskl�cri,� 0 O 27845 k� � ��GIs F, �SSIaNAL EXPIRES 10/2512�1 Marc R. McGinnis, P.E. Principal Attachments: Test Pit Locations • Test Pit Logs Grain Size Analyses cc: Peterson Consulting Engineers —Jennifer Steig 4030 Lake Washington Boulevard Northeast, Suite 200 Kirkland, Washington 98033 Via facsimile: (425) 822-7216 MRM: alt • GEOTECH CONSULTANTS, INC. \ ` ' .,... _... -•-• - - -- 5� � MWS EL. = 353.0 LENGTH = 204 � r- o � Sb�� /• SURF- CE PON� BOTTOM EL. = 349.5 WIDTH = 9' � AREA IM 46.6— — — --- -- -- = 2,000 SF I _ SLOPE = 1.59 • r" } / `"F — /CT CHWL. 340.1 (NE,SW) CNN C1rT0 E /ST/N_ — � / / 6' WOOD FENCE( �� �i • ' € 5d /TYP I� I / ~'-'' /E J53.0 — — -- / — — — — — / I ` . TOP 12" I 9 P� Y 349.5 TP \� ORINATER P,-e4 TRACT _ _ \ . \ . \ SOVERFLOWYSTE \ \ \ �l — \ I \ FLQW� 1 f PROPOSED STORM SPLlT7FRi I j DRAINAGE CATCH BASII \ I \�� ♦ \/ + IF(TYP.) \\ 00 AM \SP/LI w C NTROL' e 1 s CIS 1 TRACT - ,- PARK I ` \ ♦ / \ i ' NORTH ® Test Pit conducted for \ \� \ Sept, 14, 1999 study `\ ; 12 v Test Pit conducted for recent infiltration testing i ' \ 4 ' {eti��l{ �Q,�r, �o o�efi�aa�ti� 5G5 TEST PIT A Description Elevation +/- 354' Brown SAND, some gravel, fine-grained, dry to moist, loose becomes brown/gray, moist, loose to medium-dense 5 S PI: becomes medium- to coarse-grained, medium-dense to dense - becomes brown, gravelly, very moist 10 " Test Pit was terminated at 10 feet on October 19, 2000. " No groundwater seepage was observed during excavation. " Light caving was observed from 0 to 6 feet during excavation. 15 �N yam' j e TEST PIT B �r''0%41��� Description Elevation +/- 360' Dark brown, silty SAND, assorted household garbage, loose (FILL) FILL Brown SAND, some gravel, fine-grained, dry to moist, loose 5 becomes brown/gray, gravelly, fine- to medium-grained, medium-dense SP 10 becomes brown, less gravelly, medium- to coarse-grained, dense - becomes very moist " Test Pit was terminated at 13 feet on October 19, 2000. 15F No groundwater seepage was observed during excavation. " Light to moderate caving was observed from 0 to 7 feet during excavation. TEST PIT LOG GEOTECH Beacon Way South and South 7th Court CONSULT�s, INC. Renton, Washington IJ06A(6. Date: Logged by: Ptate. 99330 Oct.2000 GDB le���`t TEST PIT C Description Elevation +/- 364' Dark brown, silty SAND with asphalt, concrete, and assorted household garbage, loose (FILL) 5 FILL 10 Old TOPSOIL Brown, gravelly SAND, fine- to medium-grained, moist, medium-dense 15 SP 18 * Test Pit was terminated at 18 feet on October 19, 2000. * No groundwater seepage was observed during excavation. * Light to moderate caving was observed from 0 to 7 feet during excavation. TEST PIT LOG GEOTECH Beacon Way South and South 7th Court CONSULTANTS,INC. Renton, Washington -- Job No: Dates 99330 oct.2000 L0 �g Pate. \ {° °I0 �tip{ TEST PIT D Description Elevation +/- 366' TOPSOIL Dark brown, silty SAND with concrete, asphalt, and household garbage, loose (FILL) 5 FILL 10 15 rown to gray 6ARD, fine- o me ium-graine , moist o wet, oose o medium- dense FILL? " Test Pit was terminated at 16 feet on November 3, 2000. " No groundwater seepage was observed during excavation. * Light to moderate caving was observed from 0 to 8 feet during excavation. e,��Il{ TEST PIT E 0- 01 Description Elevation +/- 362' FILL Brown, silty SAND with organics, household garbage, and old 45's, loose (FILL) Gray, gravelly, silty SAND with wood chips, fine- to medium-grained, moist, loose 5 to medium-dense (FILL) FILL Gray, gravelly SAND, medium-grained, moist, medium-dense 10 SP - becomes brown, moist to very moist, medium-dense to dense 15 " Test Pit was terminated at 16 feet on November 3, 2000. " No groundwater seepage was observed during excavation. * Light to moderate caving was observed from 0 to 8 feet during excavation. TEST PIT LOG GEOTECH Beacon Way South and South 7th Court CONSULTANTS,INC. Renton, Washington -� — Job No: Date: Logged by. Plate: 99330 Nov.2000 GDB ��{ TEST PIT F 'Gos�lj V, C ko"- �SG� Description Elevation +/- 362' Dark brown, silty SAND with concrete, asphalt, and household garbage, loose (FILL) 5 FILL 10 - becomes gray Brown, gravelly SAND, medium-grained, moist to very moist, medium-dense 15 SP * Test Pit was terminated at 19 feet on November 3, 2000. * No groundwater seepage was observed during excavation. * Light to moderate caving was observed from 0 to 10 feet during excavation. TEST PIT LOG GEOTECH Beacon Way South and South 7th Court CONSULT"rS,INC. Renton, Washington -- -- - Job No: Date: Logged by. I plate: 99330 Nov.2000 GDB 0� %e, G5 TEST PIT G 9 �O ,� Description Elevation +/- 363' Brown, silty SAND with roots, fine- to medium-grained, moist, loose (FILL) 5 - becomes gray and gravelly, with household garbage, asphalt, concrete, tires FILL 10 Gray, gravelly SAND, fine- to medium-grained, moist, medium-dense 15 SP - becomes brown, less gravelly - becomes gravelly, medium-grained, medium-dense to dense * Test Pit was terminated at 18 feet on November 3, 2000. ' No groundwater seepage was observed during excavation. * Light caving was observed from 0 to 12 feet during excavation. TEST PIT LOG GEOTECH Beacon Way South and South 7th Court CONSULTANTS,INC. Renton, Washington Job No: Date Logged b}; plate: 99330 Nov.2000 GDB TEST PIT H Description Elevation +/- 360' Dark gray, silty SAND with roots, asphalt, concrete, household garbage, and beer FILL bottles, loose (FILL) 5 Brown to gray, gravelly SAND, fine-to medium-grained, slightly moist, medium- dense 10 SP - becomes gray, less gravelly 15 - becomes brown/gray, medium-grained, moist to very moist " Test Pit was terminated at 17 feet on November 3, 2000. " No groundwater seepage was observed during excavation. " Light caving was observed from 0 to 2 feet during excavation. TEST PIT LOG GEOTI Beacon Way South and South 7th Court TS,INC. CONSULTANTS, Renton, Washington • —�- Job No: Date: LoWe t Plate. 99330 Nov.2000 • Appendix A - Grain Size Analyses Beacon Way South and South 7th Court Renton, Washington • GEOTECH CONSULTANTS,INC. sieve analysis Job Data: • Client: Job Number: 99330 Job Name: Date: 11/07/00 Sample Data: Test Pit/Boring: TP- E Tare: 0 Sample: Wet Weight: 512.2 Depth: 12' Dry Weight: 488.1 Wash Data: %Moisture: 4.9 Dry Weight(before wash): 488.1 grams Dry weight(after wash): 479.9 grams Washed Soil Weight: 8.2 grams F - S e 1.FWelgotetarned cent. r No. mn.' - (gram) 'Percent Retained; 'Passed Each Total - Each Total Total L3810100.0 L----4 19 05 45.9 1 45.9 1 9.4 1 9.4 90.6 -- _- 3/8- 9.53 79.6 125.5 16.3' 25.7 74.3 47.91 173.41 9.81 35.51 64.5 • -------- ----- -----i-----t------i------t------ 10 2.00 46.1 219.51 9.41 45.0 1 55.0 --r-----r----- -----t------t------t------ __- 40- i 0.43 195.31 414.81 40.01 85.01 15.0 ___100- i 0.15 i 64.0 i 478.8 i 13.1 i 98.1 i 1.9--r-----r------1-----T-----1------T-----9 __-200---1 0.08 i 3.Oi 481.81 0.6i 98.71 1.3 <200 r 0.00 -if 0.ill--481.9T--- 0.071----98.7T----1.3 tall- TO490.11 100.4 4.4 Sieve Opening(rrm.) 11,00.00 10.00 1.00 0.10 0.01 100.0 100 90.6 90 80 74.3 70 v 64.5 60 r4 55.0 50 a c 40 d 30 a 20 15.0 10 1.9 1.3 0 • Page 1 sieve analysis Job Data: • Client: Job Number: 99330 Job Name: Date: 11/07/00 Sample Data: Test Pit/Boring: TP- E Tare: 0 Sample: Wet Weight: 645.9 Depth: 16' Dry Weight: 619.7 Wash Data: %Moisture: 4.2 Dry Weight(before wash): 619.7 grams Dry Weight(after wash): 613.5 grams Washed soil weight: 6.2 grams :Sieve - . Sieve.Si.., Wa etamed: cent Inches or.No. -, rrve> ams Percerrt Retainer! Passed Each Total' Each Total Total. 11/2 3810 0.0, 0.0- , 0.0, 0.0� 100.0 --------L-----------�---- 1----- ------1 3/4 19 OS 56 3 56.3 9.1 ------ 9.1 90.9 3/8 9.53 1 178.01 234.31 28.71 37.8� 62.2 --------F -----►-----q-----4-----A------+------ _ _4 _ 1 4.75 1 113.31 347.61 18.31 56.1 43.9 • --------f------f------i-----f-----1------t------ 10 1 2.00 1 74.6 i 422.21 12.0 40- i 0.43 i 166.91 589.11 26.91 95.11 4.9 --r-----r-- Z -----T------1------T------ _-_100---i 0.15 i 24.9i 614.01 4.01 99.1i 0.9 r -----f-----1-----7-----I------T------ 200 0.08 i __ 2.01 616.O i 0.31 99.41 0.6 -------- <200 0.00 r 0.3,--616.3�--- 0.0,----99.5T----0.5 Total 622.51 100.5 ' -0.b Sieve Opening(mm.) 100.00 10.00 1.00 0.10 0.01 100.0 :: 100 90.9 90 80 70 0 a 62.2 60-50 � a c 43.9 40 9 d 31.9 30 a 20 10 4.9 0 0.9 0.6 • Page 1 sieve analysis Job Data: • Client: Job Number: 99330 Job Name: Date: 11/07/00 Sample Data: Test Pit/Boring: TP- G Tare: 0 Sample: Wet Weight: 304.5 Depth: 14' Dry Weight: 286.3 Wash Data: %Moisture: 6.4 Dry Weight(before wash): 286.3 grams Dry Weight(after wash): 280.8 grams Washed Sal Weight: 5.5 grams Sleve.U Sieve SI e- igt�Retained fWcent Inches or No. mm. ams Percertt Retained" passed Each.." Total Eacfi Tc►ta1 Total 0.01 0.01 O.dl 0.01 100.0 L-----i-----J-----1------�------ 1------ 3/4 19 05 0.01 0.01 0.01 0.01 100.0 3/8 1 9.53 4.81 481 1.71 1.71 98.3 --------1------E----- -----: 4------�------+------ _4 _ 1 4.75 1 6.91 11.71 2.41 4.11 95.9 --+------r------ ----- +-----1------+------ 10-__1 2.00 7.81 19.51 2.71 6.81 93.2 • t------r-----I ----t------ ------t------ ___ 40- 1 0.43 1 122.91 142.41 42.91 49.71 50.3 --1------r----7-----T-----7------T------ ___100--_1 0.15 1 138.21 280.61 48.31 98.01 2.0 r -----r-----1-----T-----1------T------ 200---1 _0.08 _1 __ 1.81 282.41 0.61 98.61 1.4 <200 0.00 1 0.6,--283.0T--- 0.2,----98.8T----1.2 Total 288 5 100 8 48 Sieve Opening(m m.) 100.00 10.00 1.00 0.10 0.01 100.0.100.0 100 3 95.9 93 2 90 80 70 v- d 60 50 50.3 c 40 30 a 20 10 2.0 1.4 0 • Page 1 sieve analysis Job Data: • Client: Job Number: 99330 Job Name: Date: 11/7/00 Sample Data: Test Pit/Boring: TP- G Tare: 0 Sample: Wet Weight: 612 Depth: 18' Dry Weight: 585.6 Wash Data: %Moisture: 4.5 Dry Weight(before wash): 585.6 grams Dry Weight(after wash): 579.1 grams Washed Soil Weight: 6.5 grams ieve reve Sl- Weight-Ketained Percent Inches or No. mrrL {grams) Percent Retained Passed Each ; Total Each ; Total Total 11/2 38.10 0.01 ' -----}----------�-----------}------0_--�-----------F----------- ------1 00_0 3/4 ; 19.05 ; 111.11 111.1; 19.0; 19.0; 81.0 ------ ---------;----------1----------;----------1-----------;------------;------------ 3/8 ; 9.53 ; 51.9; 163.0; 8.9; 27.8; 72.2 ----------------;---------- ----------;-----------;------------;------------41------------ 4__--- 4 75 ; 49.7; 212.7; 8.5; 36.3; 63.7 --t----------r----------t-----------►----_-------t----------- • ---___10----_ 1- 2:-- - 71.8 ------ 12.3 48.6 51.4 -r ---------T----------r----------T-----------T------------T----------- 40 1 0.43 1 240.11 524.6 41 01 89.61 10.4 ----------------F-----------#-----------F-----------�---------=F------------4----------=- 100 1 0.15 53.71 578.31 9.21 98.81 1.2 ----- ----------}----------1----------}-----------J------------;------------;------------ ____ ___ 2.41 580.7; 0.4; 99.2; 0.8 00 0.08 <200 1 0.00 1.21 581.91 0.21 99.4 0.6 Total 588.41 j 100.5 -0.5 Sieve Opening(rnrn.) 100.00 10.00 1.00 0.10 0.01 100.0 100 90 81.0 80 70 72.2 v 63.7 60 a 51.4 c 40 _ y 3 a 20 10.4 10 1.2 0.8 0 Page 1 sieve analysis Job Data: • Client: Job Number: 99330 Job Name: Date: 11/07/00 Sample Data: Test Pit/Boring: TP- H Tare: O Sample: Wet Weight: 731.3 Depth: 17' Dry Weight: 700.5 Wash Data: %Moisture: 4.4 Dry Weight(before wash): 700.5 grams Dry Weight(after wash): 691.9 grams Washed Soil Weight: 8.6 grams Sieve'US- ieve Sl- ht Retained:: rcen Inches or No. mm ( rams Percent fteta'med Passed Each Total' Each Total . Total L3 - O.OJ--- 0-01----0-z:j --0-01---100.0 ___ 3/4 ' 19 05 ' 147 2' 147.2' 21.0' 21.0' 79.0----- --=-- ----=-+----- ----- ------ ------ _ 3/8_-_' 9.53 1 177.01 324.2' 25.31 46.3' 53.7 ------H-----1-----4------a------4------ ____4__ 4.75 1 117.01 441.21 16.71 63.01 37.0 • --------+------ -----+----- ----- ------+------ 10 2.00 1 68.81 510.01 9.81 72.81 27 2 --r-----r---- ----- ----- ------rt------ --- 40---i 0.43 i 131.91 641.91 18.81 91.61 8.4 r-----r---- ----- ----- ------T------ ---100- i 0.15 i 48.O 1 689.91 6.91 98.51 1.5 --r-----r-----1-----7-----1------T------ __-200-_-1 0.08 i __ 2.21 692.11 0.31 98. 1.2 <200 0.00 0.5,--692.6T--- 0.1,---- 8�98.9T----1.1 Total 7012 100.1 Sieve Opening(nrn.( 100.00 10.00 1.00 0.10 0.01 100.0 100 90 79.0 80 70 60 53.7 50 a � c 40 37.0 30 a 27.2 20 10 8.4 1.5 1.2 0 • Page 1 sieve analysis Job Data: • Client: Job Number: 99330 Job Name: Date: 11/7/00 Sample Data: Test Pit/Boring: TP- H Tare: 0 Sample: Wet Weight: 382.9 Depth: 14' Dry Weight: 370.2 Wash Data: %Moisture: 3.4 Dry weight(before wash): 370.2 grams Dry Weight(after wash): 357.3 grams Washed Soil weight: 12.9 grams Sieve US- Sieve SI- .4Veight RetainedPercent Inches or No. Ulf". (grams) Percent Retained Passed Each ; Total Each ; Total Total _____11/2_ 38.1C 0.0� ' 3/4 ----f--19.05-+------ ----f------91--------0=qh----------�1------100_0 ' 0.0; 0.0; 0.0; 0.0; 100.0 ----------------;-----------;----------;-----------L-----------;------------1------- 0. ______318_ ; 9.53 ; 35.5 35.5 9.6 9.6; 90.4 -----►----------------------►----------L----------- ------------ ------------ _______4 p 4.75 23.6; 59.1; 6.4; 16.0; 84.0 • -------r----------t--------^r-- -- ---------' ______10__ - 2.00 __28_2; 87.3: 7.6 23.6 76.4 ----r----------T-- r----------T---------_-r_______ _..___---_--__ 40 0.43 194 7 282.0 52.61 76.2 23.8 ----------------F----------+-------=--F----------+-----------F------------i------------ 100 0.15 ; 72.0; 354.0; 19.4; 95.61 4.4 ---------------- ----------1---------- ----------1-----------�------------1------------ _____ 200 ; 0.08 ; 5.3; 359.3; 1.4; 97.1; 2.9 <200 0.00 0.7; 360.0; 0.2; 97.21 2.8 Total T 372.91 1 100.7 0.7 Sieve Opening(mm.) 100.00 10.00 1.00 0.10 0.01 100 100.0 100.0 90 90.4 80 84.0 76.4 70 d 60 a R � a c 40 d 30 a 23.8 20 10 4.4 2 9 0 • Page 1 � q • 6.2 RESULTS OF TEST PITS FOR FILL EXPLORATION BY GEOTECH CONSULTANTS DATED NOVEMBER 9, 2000 GEOTECH13256 NE 201h Street, Suite 16 z Bellevue, WA 98005 CONSULTANTS, INC. (425) 747-5618 FAX 747-8561 Memo JN: 99330 To: Chris Austin Rome Marc R.McGinnis CompanT. Bennett Development Date: November 9, 2000 Address: 9 Lake Bellevue Drive, Suite 204 FAX: (425)709-6553 Bellevue, WA 98005 Phone: (206) RE Resutts of Test Pits for Fitt Exploration Heritage—Renton Hill Renton,Washington This memo presents a summary of the depths of existing fill found in the test pits that previously conducted and have recently excavated during the infiltration testing for the proposed pond. The following table summarizes the depths of fill encountered in the test pits. Test Pit Depth of Fill Below Existing Grade 3 Greater than 12 feet 4 13 feet • 5 10 feet A 0 feet B 3 feet C 12 feet D At least 15 feet, possibly greater than 16 feet E 8 feet F 13 feet G 12 feet H 5 feet 3 feet 2 feet K 7.5 feet L Tires to max 3 feet excavated M Tires to max 3 feet excavated N 3 feet 0 5 feet P 0 feet Q 5.5 feet Generally,the fill consisted of a silty sand that contained chunks of concrete and asphalt, and varying amounts of organic and household debris. Strictly on a visual basis, we estimate that concrete and asphalt, and other debris comprised approximately 25 percent of the fill, by volume. Of this, approximately one-half would be the debris. The concrete, asphalt, and debris will need to be screened from the fill, then the silty sand could be used in non-structural applications on the site. The debris will likely need to be hauled to a landfill, and the • concretelasphalt could likely go to a recycler. cc: Peterson Consulting-Jennifer Steig (425)822-7216(FAX) E p 26,3119 1 (SEX. G'Lj TYPE �2 (NW) TOP 343.5 v CA TV. 12" lE 340.4 (S) OVERFLOW IS 0 PM ` � 12 IE 340.5 (NE,I / I • CNN T TO XISnII PRO OSED INFILTRATION POND I PROPOSED WU SL /5� (��� [AmWS EL. = 353.0 LENGTH = zv4' • FVC w — — ON BOTTOM EL. = 349.5 I WIDTH9' � - UR 9CE AREA = 2,000 SF I SLOPE = 1.590_.CT CNIdL340.1 (NE,SW) CNN CI-CI-TO EXISTING_ 6' WOOD FENCE( / TOP 12 x A �f 1 OFc7Cl kVA TER T P�4\ \� ' TRACT _ UTR \ OV RFkow SYSTE — � - \/� FLQW� i` + T P- PRO' RO DRA, , LENGTH / \� l .\,� ,� ` ��, � (rYF t. , , y J . 62.08 - T -�— i- T Pam--; G / / ` \SPuLC N1�ROL� l / _\ �, _ ` 1 TP- 1P7L 7RACT — T P , PARK I 30' I NORTH Test Pit conducted for \ \1 ' r ® Sept, 14, 1999 study �\ ; 2 i\l s I Q Test Pit conducted for 2 I recent infiltration testing w I Test Pit for fill depth determination f'� I Swle ; 1'�=,Say �sa",-e �s drA�n4 \� :� y�1+ \ 14 M / • w • 6.3 GEOTECHNICAL ENGINEERING STUDY BY GEOTECH CONSULTANTS DATED SEPTEMBER 14, 1999 O E O'I'E C H September 14, 1999 CONSULTANTS, INC. 10'256 NE 20th street,suite 16 JN 99330 allevue,WA 98005 (425)747-5618 FAX(425)747-8561 The Bennett Corporation 9 Lake Bellevue Drive, Suite 204 Bellevue, Washington 98005 Attention: Ryan Fike Subject: Transmittal Letter— Geotechnical Engineering Study Proposed Heritage Arnold Project South 7th Street and Beacon Way Southeast Renton, Washington Reference: Hart Crowser, Inc.; Abandoned Mine Assessment, Heritage Arnold Property, Renton, Washington; August 16, 1999. Dear Mr. Fike: We are pleased to present this geotechnical engineering report for the proposed residential subdivision to be constructed at the Heritage Arnold property in Renton. The scope of our work consisted of exploring site surface and subsurface conditions, and then developing this report to • provide recommendations for general earthwork, design criteria for foundations, retaining walls, and pavements and mitigation of potential coal mine subsidence hazards. This work was authorized by your acceptance of our proposal, P-5004, dated August 16, 1999." The subsurface conditions of the proposed building site were explored with fourteen test pits that encountered native topsoil and weathered, gravelly sand overlying dense to very dense, gravelly sand. Loose fill with concrete rubble, construction debris, and household garbage was encountered as deep as 13 feet below existing grade on the western portion of the site. It appears that the small rise in this area consists of fill. Single-family residences may be supported on conventional foundations bearing directly on native, medium-dense to dense, gravelly sands. Depending on the final site grades and on the locations of the residences, some overexcavation may be required to expose competent bearing soils. The fill soils are not suitable for supporting the loads associated with the proposed development; foundations in these areas either will need to be overexcavated, or be pile- or pier-supported. The site is underlain by three deep coal seams, which were mined until the early 1920s. Hart Crowser, Inc. developed a report detailing mine activity and potential subsidence issues at the subject site. Applicable recommendations from their study have been incorporated into this report. The Bennett Corporation JN 99330 September 14, 1999 Transmittal Letter- Page 2 • The attached report contains a discussion of the study and our recommendations. Please contact us if there are any questions regarding this report, or if we can be of further assistance during the design and construction phases of this project. Respectfully submitted, GEOTECH CONSULTANTS, INC. Marc R. McGinnis, P.E. Associate EMT/MRM: alt • • GEOTECH CONSULTANTS, INC. • GEOTECHNICAL ENGINEERING STUDY Proposed Heritage Arnold Project South 7th Street and Beacon Way Southeast Renton, Washington This report presents the findings and recommendations of our geotechnical engineering study for the site of the proposed subdivision in Renton. We were provided with a topographic map. Mead Gilman & Associates developed this plan, which is dated July 28, 1999. Development of the property is in the planning stage, and detailed plans were not made available to us. Based on conversations with Ryan Fike, we understand that the site will be developed with a number of single-family residences. We anticipate that access to the residences will be via paved common streets and private driveways. We were also provided with the Abandoned Mine Assessment, prepared by Hart Crowser, Inc. This report, which is dated August 16, 1999, discusses historical coal mining activity at the subject site and provides recommendations to protect the development from significant hazards presented by potential ground subsidence. SITE CONDITIONS • SURFACE CONDITIONS The Vicinity Map, Plate 1, illustrates the general location of the site. The triangular, approximately 10.4-acre site is located near the intersection of South 7th Street and Beacon Way Southeast. The property is bordered on its southern, angled side by the Cedar River Pipeline easement, and on its northern and eastern sides by single-family residences and undeveloped woodlands, respectively. The northeastern property corner is located at the top of a steep, undeveloped slope. This slope has an estimated height of 30 feet and an inclination of 50 to 60 percent. The terrain on the site is generally rolling, with small rises and hollows located throughout the parcel. It appears that some grading has been done on the property, resulting in a steep, U-shaped cut slope located near the center of the site. An abandoned gravel road winds through the southeastern side of the site and ends at the steep cut slope. The flat area at the base of the cut slope may have been a gravel pit at some time during the past. The small rise located on the western side of this flat area consists of fill; some pea gravel is visible on the surface. The westernmost portion of the site is strewn with large amounts of household garbage and construction debris, and appears to have been used as a dump. The eastern portion of the site is densely wooded with tall evergreen and deciduous trees. The ground is covered with ferns, blueberry and blackberry bushes, and other low-growth vegetation. No obvious signs of slope instability were observed during our site visit. Additionally, no visible indications of air shafts, trenches, or ground subsidence were observed on the portions of the site that we traversed. • GEOTECH CONSULTANTS, INC. The Bennett Corporation JN 99330 September 14, 1999 Page 2 • SUBSURFACE CONDITIONS The subsurface conditions were explored by excavating fourteen test pits at the approximate locations shown on the Site Exploration Plan, Plate 2. The field exploration program was based upon the proposed construction and required design criteria, the site topography and access, the subsurface conditions revealed during excavation, and the scope of work outlined in our proposal. The test pits were excavated on August 26, 1999 with a trackhoe. A geotechnical engineer from our staff observed the excavation process, logged the test pits, and obtained representative samples of the soil encountered. "Grab" samples of selected subsurface soil were collected from the backhoe bucket. The Test Pit Logs are attached to this report as Plates 3 through 9. The test pits encountered native topsoil overlying loose, gravelly sand that became medium-dense to dense with depth. This native sand contained occasional boulders. The test pits on the westernmost corner of the site encountered loose fill that contained construction debris and concrete and asphalt rubble to depths of 10 to 13 feet. Native sand was encountered underlying the fill, except in Test Pit 3, which revealed fill to the maximum 12-foot depth that was possible. The final logs represent our interpretations of the field logs. The stratification lines on the logs represent the approximate boundaries between soil types at the exploration locations. The actual transition between soil types may be gradual, and subsurface conditions can vary between exploration locations. The logs provide specific subsurface information only at the locations tested. The relative densities and moisture descriptions indicated on the test pit logs are interpretive • descriptions based on the conditions observed during excavation. The compaction of backfill was not in the scope of our services. Loose soil will therefore be found in the area of the test pits. If this presents a problem, the backfill will need to be removed and replaced with structural fill during construction. Groundwater No groundwater seepage or wet soil was observed during excavation. It should be noted that groundwater levels vary seasonally with rainfall and other factors; the absence of groundwater in our explorations does not eliminate the possibility that groundwater could be encountered during future excavations. However, due to the granular nature of the site soils, encountering significant near-surface groundwater is unlikely. We anticipate that groundwater could be found between the near-surface weathered soil and the underlying denser soil. CONCLUSIONS AND RECOMMENDATIONS GENERAL Based on our explorations at the subject site, it is our opinion that construction of the proposed single-family residences is feasible from a geotechnical engineering standpoint. The proposed residences may be supported on conventional foundations bearing directly on medium-dense to dense, native soil. Depending on final site grading, some overexcavation may be required to expose competent sand. The loose fill encountered on the western corner of the site is not suitable GEOTECH CONSULTANTS, INC. The Bennett Corporation JN 99330 September 14, 1999 Page 3 • to support the loads associated with the proposed development. The fill should be removed from building areas, or deep foundations should extend to the underlying, native, gravelly sand. We can provide recommendations and design criteria for driven piles or drilled piers, if requested. The steep slope near the northeast corner of the property may experience shallow slope movement in the future. To protect against structural damage, houses and other occupied buildings should be set back at least 25 feet from this slope. No clearing or grading should occur within 10 feet of the slope's crest. Water from drains and impervious surfaces should not be directed toward the steep slope. The site is underlain by three deep coal seams which were mined until the early 1920s. Hart Crowser, Inc. completed an assessment of the historical mine use and potential hazards associated with development over abandoned mines. Their study concludes that there is a risk of noticeable differential foundation settlement due to ground subsidence. However, the maximum calculated ground strain would result in a differential settlement of approximately 3 inches in a distance of 50 feet. Because of the approximately 80 years that have elapsed since the last documented mining, it is likely that most subsidence has already occurred. Therefore, the risk of significant area-wide subsidence is low. We highlight the following recommendations as applicable to the proposed development: • All footings should be continuous, with increased steel reinforcement, to span potential isolated subsidence areas and reduce differential settlement. • Post-and-beam construction should be considered to allow for relatively easy releveling in the event of settlement. • Concrete slabs-on-grade should be avoided in favor of floors on joists. • All new construction should include vapor barriers and well-ventilated crawl spaces to mitigate mine gas emissions. • Rigid structural materials, such as concrete and masonry, should be avoided where possible in favor of more flexible materials like steel and timber. • Avoid siding, weather stripping materials, and interior floor and wall coverings that are settlement-sensitive. • Plan regular maintenance for weather stripping, utilities, and mechanical systems which may be affected by building movement. At the time of earthwork, any areas of fill in structural areas should be thoroughly investigated to verify that they are not underlain by old air shafts or mine openings. Ground subsidence could result in distress or damage to pavements and utilities. Periodic maintenance and repair of these elements should be expected. Where the existing fill is not removed, on-grade elements such as pavements and slabs would experience noticeable long-term settlement. Pavements over existing fill should be underlain by at least 18 inches of gravelly structural fill to reduce, but not eliminate, differential settlement. Final slopes in developed portions of the site should be graded to an inclination of no steeper than 2:1 (Horizontal.-Vertical). • The erosion control measures needed during the site development will depend heavily on the P y weather conditions that are encountered. We anticipate that a silt fence will be needed around the GEOTECH CONSULTANTS, INC. The Bennett Corporation JN 99330 September 14, 1999 Page 4 • downslope side of any cleared areas. Rocked construction access roads should be extended into the site to reduce the amount of mud carried off the property by trucks and equipment. Following rough grading, it may be necessary to mulch or hydroseed bare areas that will not be immediately covered with landscaping or an impervious surface. Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the recommendations presented in this report are adequately addressed in the design. Such a plan review would be additional work beyond the current scope of work for this study, and it may include revisions to our recommendations to accommodate site, development, and geotechnical constraints that become more evident during the review process. CONVENTIONAL FOUNDATIONS The proposed single-family residences can be supported on conventional continuous footings bearing on undisturbed, native, gravelly sand, or on structural fill placed above this competent, native soil. See the later sub-section entitled GENERAL EARTHWORK AND STRUCTURAL FILL for recommendations regarding the placement and compaction of structural fill beneath structures. Adequate compaction of structural fill should be verified with frequent density testing during fill placement. We recommend that continuous footings have minimum widths of 12 and 16 inches, respectively. The foundations should be reinforced to span a minimum distance of 10 feet without soil support, similar to grade beams. They should be bottomed at least 18 inches below the lowest adjacent finish ground surface. • Footing subgrades must be cleaned of loose or disturbed soil prior to pouring concrete. Depending upon site and equipment constraints, this may require removing the disturbed soil by hand. Depending on the final site grades, some overexcavation may be required below the footings to expose competent, native soil. Unless lean concrete is used to fill an overexcavated hole, the overexcavation must be at least as wide at the bottom as the sum of the depth of the overexcavation and the footing width. For example, an overexcavation extending 2 feet below the bottom of a 3-foot-wide footing must be at least 5 feet wide at the base of the excavation. If lean concrete is used, the overexcavation need only extend 6 inches beyond the edges of the footing. An allowable bearing pressure of 3,000 pounds per square foot (pso is appropriate for footings supported on medium-dense to dense gravelly sand. For footings supported on structural fill, an allowable bearing pressure of 2,000 psf is appropriate. A one-third increase in these design bearing pressures may be used when considering short-term wind or seismic loads. Lateral loads due to wind or seismic forces may be resisted by friction between the foundation and the bearing soil, or by passive earth pressure acting on the vertical, embedded portions of the foundation. For the latter condition, the foundation must be either poured directly against relatively level, undisturbed soil or be surrounded by level structural fill. 1Ne recommend using the following design values for the foundation's resistance to lateral loading: Parameter Design Value • Coefficient of Friction 0.45 Passive Earth Pressure 350 pcf GEOTECH CONSULTANTS, INC. The Bennett Corporation JN 99330 September 14, 1999 Page 5 • Where:(i) pcf is pounds per cubic foot,and(1i)passive earth pressure is computed using the equivalent fluid density. If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will not be appropriate. We recommend a safety factor of at least 1.5 for the foundation's resistance to lateral loading, when using the above design values. SEISMIC CONSIDERATIONS The site is located within Seismic Zone 3, as illustrated on Figure No. 16-2 of the 1997 Uniform Building Code (UBC). In accordance with Table 16-J of the 1997 UBC, the soil within 100 feet of the ground surface is best represented by Soil Profile Type Sc (Very Dense Soil). The site soils are not subject to seismic liquefaction because of their dense nature and because of the absence of near-surface groundwater. PERMANENT FOUNDATION AND RETAINING WALLS Retaining walls backfilled on only one side should be designed to resist the lateral earth pressures imposed by the soil they retain. The following recommended design parameters are for walls that restrain level backfill: • [ Parameter Design Value Active Earth Pressure ' 35 pcf Passive Earth Pressure 350 pcf Coefficient of Friction 0.45 Soil Unit Weight 135 pcf Where:(i)pcf is pounds per cubic foot,and(ii)active and passive earth pressures are computed using the equivalent fluid pressures. For a restrained wall that cannot deflect at least 0.002 times its height,a uniform lateral pressure equal to 10 psf times the height of the wall should be added to the above active equivalent fluid pressure. The values given above are to be used to design permanent foundation and retaining walls only. The passive pressure given is appropriate for the depth of level structural fill placed in front of a retaining or foundation wall only. We recommend a safety factor of at least 1.5 for overturning and sliding, when using the above values to design the walls. Restrained wall soil parameters should be utilized for a distance of 1.5 times the wall height from corners in the walls. The design values given above do not include the effects of any hydrostatic pressures behind the • walls and assume that no surcharges, such as those caused by slopes, vehicles, or adjacent foundations will be exerted on the walls. If these conditions exist, those pressures should be added to the above lateral soil pressures. Where sloping backfill is desired behind the walls, we will need GEOTECH CONSULTANTS, INC. The Bennett Corporation JN 99330 September 14, 1999 Page 6 • to be given the wall dimensions and the slope of the backfill in order to provide the appropriate design earth pressures. The surcharge due to traffic loads behind a wall can typically be accounted for by adding a uniform pressure equal to 2 feet multiplied by the above active fluid density. Heavy construction equipment should not be operated behind retaining and foundation walls within a distance equal to the height of a wall, unless the walls are designed for the additional lateral pressures resulting from the equipment. The wall design criteria assume that the backfill will be well-compacted in lifts no thicker than 12 inches. The compaction of backfill near the walls should be accomplished with hand-operated equipment to prevent the walls from being overloaded by the higher soil forces that occur during compaction. Retaining Wall Backrill and Waterprootng Backfill placed behind retaining or foundation walls should be coarse, free-draining, structural fill containing no organics. This backfill should contain no more than 5 percent silt or clay particles and have no gravel greater than 4 inches in diameter. The percentage of particles passing the No. 4 sieve should be between 25 and 70 percent. If the native sand is used as backfill, a drainage composite similar to Miradrain 6000 should be placed against the backfilled retaining walls. The drainage composites should be hydraulically connected to the foundation drain system. For increased protection, drainage composites should be placed along cut slope faces, and the walls should be backfilled with pervious soil. • The purpose of these backfill requirements is to ensure that the design criteria for a retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the wall. The top 12 to 18 inches of the backfill should consist of a compacted, relatively impermeable soil or topsoil, or the surface should be paved. The ground surface must also slope away from backfilled walls to reduce the potential for surface water to percolate into the backfill. The sub-section entitled GENERAL EARTHWORK AND STRUCTURAL FILL contains recommendations regarding the placement and compaction of structural fill behind retaining and foundation walls. The above recommendations are not intended to waterproof below-grade walls. The performance of any subsurface drainage system will degrade over time. Also, groundwater drainage patterns can change, even if seepage is not evident in the temporary excavation. Therefore, if future moist conditions or seepage through the walls are not acceptable, waterproofing should be provided. This typically includes limiting cold joints and wall penetrations, and using bentonite panels or membranes on the outside of the walls. Applying a thin coat of asphalt emulsion is not considered waterproofing, but will only help to prevent moisture, generated from water vapor or capillary action, from seeping through the concrete. EXCAVATIONS AND SLOPES Excavation slopes should not exceed the limits specified in local, state, and national government • safety regulations. Temporary cuts to a depth of about 4 feet may be attempted vertically in unsaturated soil, away from property lines, utilities, and existing structures, if there are no indications of slope instability. Based upon Washington Administrative Code (WAC) 296, Part N, GEOTECH CONSULTANTS, INC. The Bennett Corporation JN 99330 September 14, 1999 Page 7 • the native sand at the subject site would generally be classified as Type B. Therefore, temporary cut slopes greater than 4 feet in height cannot be excavated at an inclination steeper than 1:1 (Horizontal:Vertical), extending continuously between the top and the bottom of a cut. The above-recommended temporary slope inclination is based on what has been successful at other sites with similar soil conditions. Temporary cuts are those that will remain unsupported for a relatively short duration to allow for the construction of foundations, retaining walls, or utilities. Temporary cut slopes should be protected with plastic sheeting during wet weather. The cut slopes should also be backfilled or retained as soon as possible to reduce the potential for instability. Please note that sand can cave suddenly and without warning. Utility contractors should be made especially aware of this potential danger. All permanent cuts into native soil should be inclined no steeper than 2:1 (H:V). Fill slopes should not be constructed with an inclination greater than 2:1 (H:V). To reduce the potential for shallow sloughing, fill must be compacted to the face of these slopes. This could be accomplished by overbuilding the compacted fill and then trimming it back to its final inclination. Water should not be allowed to flow uncontrolled over the top of any temporary or permanent slope. Also, all permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce erosion and improve the stability of the surficial layer of soil. Any disturbance to the existing steep slope beyond the northeastern corner of the site may reduce the stability of the slope. Damage to the existing vegetation and ground should be minimized, and any disturbed areas should be revegetated as soon as possible. Soil from the excavations should • not be placed on, or near, the slope. DRAINAGE CONSIDERATIONS Foundation drains are required where crawl spaces or basements will be below a structure, or the outside grade does not slope downward from a building. Drains should also be placed at the base of all earth-retaining walls. These drains should be surrounded by at least 6 inches of 1-inch- minus, washed rock and then wrapped in non-woven, geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material). At its highest point, a perforated pipe invert should be at least 6 inches below the bottom of a slab floor or the level of a crawl space, and it should be sloped for drainage. Drainage should also be provided inside the footprint of a structure, where a crawl space will slope or be lower than the surrounding ground surface, or an excavation encounters significant seepage. We can provide recommendations for interior drains, should they become necessary, during excavation and foundation construction. All roof and surface water drains must be kept separate from the foundation drain system. A typical drain detail is attached to this report as Plate 10. For the best long-term performance, perforated PVC pipe is recommended for all subsurface drains. No groundwater was observed during our field work. If seepage is encountered in an excavation, it should be drained from the site by directing it through drainage ditches, perforated pipe, or French drains, or by pumping it from sumps interconnected by shallow connector trenches at the bottom of • the excavation. GEOTECH CONSULTANTS, INC. The Bennett Corporation JN 99330 September 14, 1999 Page 8 • The excavations and site should be graded so that surface water is directed away from the tops of slopes. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. Final site grading in areas adjacent to the buildings should slope away at least 2 percent, except where the area is paved. Water from roof, storm water, and foundation drains should not be discharged onto slopes; it should be tightlined to a suitable outfall located away from any slopes. PAVEMENT AREAS The pavement sections may be supported on competent, native soil or on structural fill compacted to a 95 percent density. We recommend that the pavement subgrade must be in a stable, non- yielding condition at the time of paving. Granular structural fill or geotextile fabric may be needed to stabilize soft, wet, or unstable areas. To evaluate pavement subgrade strength, we recommend that a proof-roll be completed with a loaded dump truck immediately before paving. In most instances where unstable subgrade conditions are encountered, an additional 12 inches of granular structural fill will stabilize the subgrade, except for very soft areas where additional fill could be required. The subgrade should be evaluated by Geotech Consultants, Inc., after the site is stripped and cut to grade. Recommendations for the compaction of structural fill beneath pavements are given in a later sub-section entitled GENERAL EARTHWORK AND STRUCTURAL FILL. The performance of site pavements is directly related to the strength and stability of the underlying subgrade. • The pavement for lightly-loaded traffic and parking areas should consist of 2 inches of asphalt concrete (AC) over 4 inches of crushed rock base (CRB) or 3 inches of asphalt-treated base (ATB). We recommend providing heavily-loaded areas with 3 inches of AC over 6 inches of CRB or 4 inches of ATB. Heavily-loaded areas are typically main driveways, dumpster sites, or areas with truck traffic. The pavement section recommendations and guidelines presented in this report are based on our experience in the area and on what has been successful in similar situations. We can provide recommendations based on expected traffic loads and California Bearing Ratio tests, if requested. As with any pavements, some maintenance and repair of limited areas can be expected as the pavement ages. To provide for a design without the need for any repair would be uneconomical. GENERAL EARTHWORK AND STRUCTURAL FILL All building and pavement areas should be stripped of surface vegetation, topsoil, organic soil, and other deleterious material. The stripped or removed materials should not be mixed with any materials to be used as structural fill, but they could be used in non-structural areas, such as landscape beds. Structural fill is defined as any fill placed under a building, behind permanent retaining or foundation walls, or in other areas where the underlying soil needs to support loads. All structural fill should be placed in horizontal lifts with a moisture content at, or near, the optimum moisture content. The • optimum moisture content is that moisture content that results in the greatest compacted dry density. The moisture content of fill is very important and must be closely controlled during the filling and compaction process. GEOTECH CONSULTANTS, INC. The Bennett Corporation JN 99330 September 14, 1999 Page 9 • The allowable thickness of the fill lift will depend on the material type selected, the compaction equipment used, and the number of passes made to compact the lift. The loose lift thickness should not exceed 12 inches. We recommend testing the fill as it is placed. If the fill is not compacted to specifications, it can be recompacted before another lift is placed. This eliminates the need to remove the fill to achieve the required compaction. The following table presents recommended relative compactions for structural fill: Location of Minimum Fill Placement Relative Compaction Beneath footings or 95% walkways Behind retaining walls 90% 95% for upper 12 inches of Beneath pavements subgrade; 90% below that level Where:Minimum Relative Compaction is the ratio,expressed in percentages, of the compacted dry density to the maximum dry density, as determined in accordance with ASTM Test Designation D 1557-91 (Modified Proctor). Use of On-Site Soil If grading activities take place during wet weather, or when the site soils are wet, site • preparation costs may be higher because of delays due to rain and the potential need to dry the site soils. The moisture content of the on-site soil must be at, or near, the optimum moisture content, as the soil cannot be consistently compacted to the required density when the moisture content is significantly greater than optimum. The on-site, non-organic sand could be used as structural fill, if grading operations are conducted during hot, dry weather, when drying the wetter soil by aeration is possible. During excessively dry weather, however, it may be necessary to add water to achieve the optimum moisture content. LIMITATIONS The analyses, conclusions, and recommendations contained in this report are based on site conditions as they existed at the time of our exploration and assume that the soil and groundwater conditions encountered in the test pits are representative of subsurface conditions on the site. If the subsurface conditions encountered during construction are significantly different from those observed in our explorations, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary. Unanticipated soil conditions are commonly encountered on construction sites and cannot be fully anticipated by merely taking soil samples in test pits. Subsurface conditions can also vary between exploration locations. Such unexpected conditions frequently require making additional expenditures to attain a properly constructed project. It is recommended that the owner consider providing a contingency fund to • accommodate such potential extra costs and risks. This is a standard recommendation for all projects. GEOTECH CONSULTANTS,INC. The Bennett Corporation JN 99330 September 14, 1999 Page 10 • This report has been prepared for the exclusive use of the Bennett Corporation, and its representatives, for specific application to this project and site. Our recommendations and conclusions are based on observed site materials, and selective engineering analyses. Our conclusions and recommendations are professional opinions derived in accordance with current standards of practice within the scope of our services and within budget and time constraints. No warranty is expressed or implied. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractor's methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. This report, and the study by Hart Crowser, should be provided to any future property owners to inform them of our findings and recommendations. Additionally, this report should be provided in the project contract documents for the information of the contractor. ADDITIONAL SERVICES In addition to reviewing the final plans, Geotech Consultants, Inc. should be retained to provide geotechnical consultation, testing, and observation services during construction. This is to confirm that subsurface conditions are consistent with those indicated by our exploration, to evaluate whether earthwork and foundation construction activities comply with the general intent of the recommendations presented in this report, and to provide suggestions for design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. • However, our work would not include the supervision or direction of the actual work of the contractor and its employees or agents. Also, job and site safety, and dimensional measurements, will be the responsibility of the contractor. We conducted an environmental assessment for this site which is presented in a separate report. The following plates are attached to complete this report: Plate 1 Vicinity Map Plate 2 Site Exploration Plan Plates 3 - 9 Test Pit Logs Plate 10 Typical Footing Drain • GEOTECH CONSULTANTS, INC. The Bennett Corporation JN 99330 September 14, 1999 Page 11 • We appreciate the opportunity to be of service on this project. If you have any questions, or if we may be of further service, please do not hesitate to contact us. Respectfully submitted, GEOTECH CONSULTANTS, INC. Erin M. Toland Geotechnical Engineer g. 11XICQ ��pF WASn�'� L) r 27845 G•IS CF, 0 L IF, • EXPIRES 1 Marc R. McGinnis, P.E. Associate EMT/MRM: alt GEOTECH CONSULTANTS, INC. T R5t _ _ _ N29 o S NECA AV SW SENECA p G a AY �EE AV $W g L ND V AV SW 4 [[b z A6EEYP S4e h N�C ECA r e^ 1900 AV F'o �_ kv E N p~j Cn 6' G7 v 700 P E A= SW STEVENS't+ w M LE S AVIaS = 7'y£ 'Psw o LINO SN L NO AV 400 (J'1 ,� O A �,DyVH O A N MARLE AP* ,,w EVA LEY R SVHAROIE ,ES � t* HAROiE w AV SW — N K3-1-Jd N :,!p a s �3 l cn Ln N z Atl I n 005� ■ ANE S AV LAKE AV N C n II 1 CA] ` nM Le Sgi td 3>t� _ m ■ SHATTUCK AV ,I, EST y 1Nda... 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CA � it, /�a 77'''1h7 \\ � •J. tTl J J , O O w .g� , y� •l •.��/ J�•, L gyp CD 90 CD .J = o y J • , co CD \V,, � • gJ f-i• {e, °►l TEST PIT 1 01 Description FILL Concrete rubble with old building materials, loose (FILL) SIR Dark brown, silty SAND, moist, loose (Topsoil) over tan, slightly silty SAND, dry to slightly moist, loose 5 Test Pit was terminated at 4 feet on August 26, 1999. * No groundwater seepage was observed during excavation. * Caving was observed to bottom during excavation. 10 15 � ���`►�{ TEST PIT 2 Description Topsoil Red-brown SANE), dry to slightly moist, loose (TOPSOIL) Brown, slightly gravelly SAND, medium-grained, dry, loose 5 - becomes more gravelly, slightly moist, medium-dense SP - becomes moist, medium-to coarse-grained, less gravelly, dense 10 * Test Pit was terminated at 11 feet on August 26, 1999. L * No groundwater seepage was observed during excavation. 15 * Caving was observed to 8 feet during excavation. TEST PIT LOG GE O TE C H South 7th Street & Beacon Way Southeast CONSULTANTS,I1vc. Renton, Washington Job No: Date: I-Logged bY.99330 Sept. 1999 ET Plate: 3 l {Qj 010 TEST PIT 3 Description Dark brown, silty SAND, with concrete rubble, moist, loose (FILL) - piece of old carpet 5 FILL - asphalt chunks 8-12" in size - becomes gray-black, silty, gravelly SAND 10 - large tree stump * Test Pit was terminated at 12 feet on August 26, 1999. 15 * No groundwater seepage was observed during excavation. * Caving was observed to 12 feet during excavation. TEST PIT 4 KIO Description Red-brown, silty SAND, with roots, concrete rubble, and metal debris, dry to slightly moist, loose (FILL) - large asphalt chunk (6 feet across and 6 inches thick) 5 - some glass, household debris FILL - becomes gray-black, silty, gravelly sand, with asphalt chunks and household debris 10 LsP =`. Red-brown, slightly silty, gravelly SAND, medium- to coarse-grained, moist, medium-dense to dense 15 - becomes brown at 13.5 feet, dense * Test Pit was terminated at 14.5 feet on August 26, 1999. * No groundwater seepage was observed during excavation. * Caving was observed to 13 feet during excavation. TEST PIT LOG GEOTECH South 7th Street & Beacon Way Southeast CONSULTANTS,INC. Renton, Washington Job No: Date: Logged by: Plate: 99330 Sept. 1999 EMT 4 ---■ram. {� 1001 TEST PIT 5 e4 � �ti� �G5 G Description Red-brown, silty, gravelly SAND, with cobbles, brick debris, and household garbage, loose (FILL) - large tree stump and root ball 5 FILL - becomes gray, slightly silty, gravelly SAND, moist 10 Sp Red-brown, weathered, slightly silty SAND, fine-to medium-grained, moist, medium-dense -becomes brown, dense * Test Pit was terminated at 11.5 feet on August 26, 1999. * No groundwater seepage was observed during excavation. 15 Caving was observed to 10 feet during excavation. {e, O� TEST PIT 6 a� tie 5 Description FILL Red-brown, silty SAND, with abundant roots, dry to slightly moist, loose (FILL) 6 inches of dark brown TOPSOIL over Red-brown, gravelly SAND, fine-to medium-grained, moist, loose 5 SP - becomes medium-dense to dense - becomes less gravelly, dense 10 Test Pit was terminated at 8.5 feet on August 26, 1999. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. 15 TEST PIT LOG GE O TE C H South 7th Street & Beacon Way Southeast CONSULTANTS,INC. Renton, Washington No: Date: Logged by: Plate: 99330 1 Sept. 1999 EMT 5 ej 010� TEST PIT 7 o ��e��a�rotie G5 G0 �a �5 Description Brown, slightly silty SAND, with abundant roots, dry, loose (TOPSOIL) Red-brown SAND, with occasional boulders up to 1 foot diameter, fine-grained, dry to slightly moist, medium-dense Sp - becomes brown, with gravel and cobbles, moist, dense 5 10 * Test Pit was terminated at 8.5 feet on August 26, 1999. * No groundwater seepage was observed during excavation. * Some caving in upper 4 feet was observed during excavation. 15 N 41e�0�{ TEST PIT 8 o ewe"va' G° Description Dark brown, slightly silty SAND, with occasional gravel, with abundant roots, dry to slightly moist (TOPSOIL) Red-brown, silty, gravelly SAND, fine-to medium-grained, moist, medium-dense SM to dense - becomes brown, very dense 5 * Test Pit was terminated at 6.5 feet on August 26, 1999. * No groundwater seepage was observed during excavation. 10 * No caving was observed during excavation. 15 TEST PIT LOG GEOTECH South 7th Street & Beacon Way Southeast CONSULTANTS,INC. Renton, Washington ,sue Job No: Date: Logged by: Plate: 99330 1 Sept. 1999 1 EMT 1 6 TEST PIT 9 Description • Dark brown, silty SAND, loose (TOPSOIL) Red-brown, silty, gravelly SAND, with abundant roots, fine-grained, moist, SM medium-dense - becomes brown, dense to very dense 5 501 * Test Pit was terminated at 5.5 feet on August 26, 1999. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. 10 15 jo�\►�{ TEST PIT 10 • 9 Description Topsoil Red-brown TOPSOIL, loose Brown, silty, gravelly SAND, with abundant roots, fine-to medium-grained, moist, sM medium-dense to dense 5 - becomes dense to very dense * Test Pit was terminated at 5.5 feet on August 26, 1999. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. 10 15 TEST PIT LOG GE O TE CH South 7th Street & Beacon Way Southeast CONSULTANT'S,INC.F-4 Renton, Washington I. Job No: Date: Logged by: Plate: � \ 99330 Sept. 1999 EMT 7 TEST PIT 11 �4o o��c� a �aroti� �G5 G � Description Dark brown, silty SAND, with abundant roots, moist, loose (TOPSOIL) Red-brown SAND, medium-grained, moist, medium-dense SP - becomes dense, brown 5 * Test Pit was terminated at 7 feet on August 26, 1999. 10 * No groundwater seepage was observed during excavation. * Some caving of upper 4 feet was observed during excavation. 15 TEST PIT 12 �^r � rotim G5 9�4 Go ' ° ig Description Dark brown, slightly silty SAND, with abundant roots, dry to slightly moist(TOPSOIL) gp Reddish-brown SAND, with some gravel and sandstone chunks, medium-grained, moist, medium-dense to dense 5 - becomes brown, very dense * Test Pit was terminated at 6 feet on August 26, 1999. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. 10 15 TEST PIT LOG GEOTECH South 7th Street & Beacon Way Southeast CONSULTANTS,INC. Renton, Washington Job No: Date: Logged by: Plate: 99330 1 Sept. 1999 1 EMT 8 TEST PIT 13 9 G Description Dark brown, silty SAND, with abundant roots, dry to slightly moist, loose (TOPSOIL) SP Red-brown SAND with gravel, medium-grained, moist, medium-dense - becomes brown, dense to very dense 5 " Test Pit was terminated at 5.5 feet on August 26, 1999. " No groundwater seepage was observed during excavation. * No caving was observed during excavation. 10 15 �`i e< TEST PIT 14 o� ��� a ro%s Z 5 �'t 4 G Description Red-brown, slightly silty SAND,with abundant roots, fine-grained, dry to slightly moist, loose -becomes medium-dense SP .', -becomes moist, dense to very dense 5 * Test Pit was terminated at 5 feet on August 26, 1999. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. 10 15 TEST PIT LOG GEOTECH South 7th Street & Beacon Way Southeast CONSULTANTS,INC. Renton, Washington Job No: Date: Logged by: Plate: 99330 Sept. 1999 EMT 9 • Slope bockfil/ away from foundation. —•� ` `\\ T/GHTL/NE ROOF DRAIN Do not connect to footing drain. BACKF/L L See text for VAPOR BARRIER requirements. SLAB — WASHED ROCK °. .'°'. - ^; - `, �, 4 min. 6 min. FREE-DRAINING NONWOVEN GEOTEXT/LE SAND/GRAVEL FILTER FABRIC 4"PERFORATED HARD PVC PIPE • Invert of least as low as footing and/or crawl space. Slope to drain. Place weepholes downward. , TYPICAL FOOTING DRAIN GEOTECH South 7th Street & Beacon WaySoutheast coNsul,Tarrrs,INC. Renton, Washington Job No: Date. plate. 99330 Sept_ 1999 10 6.4 PHASE 1 ENVIRONMENTAL SITE ASSESSMENT BY GEOTECH CONSULTANTS DATED SEPTEMBER 9, 1999 G E O T E C H September 9, 1999 CONSULTANTS, INC. 256 NE 20th street,Suite 16 JN 9930A llevue,WA 98005 (425)747-5618 FAX (425)747-8561 Bennett Corporation 9 Lake Bellevue Drive, Suite 204 Bellevue, Washington 98005 Attention: Ryan Fike Subject: Transmittal Letter Phase 1 Environmental Site Assessment Proposed Heritage Arnold Project Beacon Way Southeast Renton, Washington Dear Mr. Fike: Geotech Consultants, Inc. is pleased to present the results of our recently completed Phase 1 Environmental Site Assessment for the subject property. Our work was completed in accordance with our proposal dated August 18, 1999. Please find the assessment attached. We appreciate this opportunity to be of service to Bennett Corporation on this project. If you have • any questions, or if we may be of additional service, please contact us. Respectfully submitted, GEOTECH CONSULTANTS, INC. David Bair Environmental Engineer DB: alt • PHASE 1 ENVIRONMENTAL SITE ASSESSMENT Proposed Heritage Arnold Project Beacon Way Southeast Renton, Washington Submitted by: GEOTECH CONSULTANTS, INC. David Bair Environmental Engineer FI oy WAS o P'' ,Q19660 4�40 0 AL��G q, q EXPIRES 8/ 1]/I) James R. Finley, P.E. Principal • GEOTECH CONSULTANTS, INC. • TABLE OF CONTENTS 1.0 EXECUTIVE SUMMARY.......................................................................................................1 2.0 INTRODUCTION...................................................................................................................1 2.1 Special Terms and Conditions 2.2 Purpose and Scope of Work 3.0 SITE DESCRIPTION AND RECONNAISSANCE...................................................:..............2 3.1 Location and Legal Description 3.2 Site and Vicinity Characteristics 3.3 Hazardous Materials 3.4 Other Conditions of Concern 4.0 HISTORICAL USE INFORMATION ......................................................................................6 4.1 Previous Environmental and Geotechnical Investigations 4.2 Historical Maps 4.3 Tax Assessor Records 4.4 State Archive Records 4.5 Renton Directories 4.6 Aerial Photographs • 5.0 ENVIRONMENTAL SETTING 8 ......................................................................................... 5.1 Regional Physiographic Conditions 5.2 Soil and Geologic Conditions 5.3 Hydrogeologic Conditions 6.0 RECORDS REVIEW.............................................................................................................8 6.1 Federal Records Sources 6.2 State Records Sources 6.3 Local Agency Sources 6.4 Assumptions and Opinion of Contaminant Mobility and Site Vulnerability 7.0 RESULTS OF INVESTIGATION.........................................................................................10 7.1 Findings 7.2 Conclusions and Recommendations 7.3 Limitations 8.0 REFERENCES....................................................................................................................11 ATTACHMENTS Plate 1 Vicinity Map Plate 2 Site Plan Plates 3 &4 Site Photographs • Appendix VIS's Site Assessment GEOTECH CONSULTANTS, INC. • PHASE 1 ENVIRONMENTAL SITE ASSESSMENT Proposed Heritage Arnold Project Beacon Way Southeast Renton, Washington 1.0 EXECUTIVE SUMMARY Presently, the site is undeveloped and covered with trees, brambles, and other native vegetation. The Vicinity Map, Plate 1, illustrates the general location of the site. Land use in the surrounding area is characterized by single-family residences. Two tunnels from abandoned coal mines underlie the site. Historical research revealed that the northern portion of the site was excavated, then filled with imported material that included construction debris. This assessment did not reveal any recognized environmental conditions in connection with the subject property. A discussion of the scope of our work, our site observations, and our conclusions are contained in this report. 2.0 INTRODUCTION This report presents the results of our Phase 1 Environmental Site Assessment of the Heritage Arnold property at Beacon Way Southeast in Renton, Washington. • 2.1 Special Terms and Conditions The scope of work for our review of this site did not include the examination, sampling, or analysis of subsurface soil or groundwater on the site for potential environmental contaminants. If new information is developed in future site work, which may include excavations, borings, or studies, Geotech Consultants, Inc. should be given the opportunity to review the findings, re-evaluate the conclusions of this report, and provide amendments as required. 2.2 Purpose and Scope Of Work The purpose of an environmental assessment is to satisfy one of the requirements to qualify for the innocent landowner defense in the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA): that is, to make "all appropriate inquiry into the previous ownership and uses of the property consistent with good commercial or customary practice." Our scope of work and the limitations of our study are consistent with American Society for Testing and Materials (ASTM) Designation E 1527: Standard Practice for Environmental Site Assessments: Phase 1 Environmental Site Assessment Process. The objective of a Phase 1 assessment is to minimize potential future liability for environmental problems by demonstrating that at the time this report was prepared, the owner, holder, or buyer had no knowledge or reason to know that any hazardous substance had been released or disposed on, in, at, or near the property. An additional objective of • the Phase 1 assessment is to identify potential contamination sources. The goal of the processes established by the ASTM is to identify recognized environmental conditions. The term 'recognized environmental conditions" means the presence, or likely GEOTECH CONSULTANTS, INC. Bennett Corporation A 9930A September 9, 1999 Page 2 • presence, of any hazardous substances or petroleum products on a property under conditions that indicate an existing release, a past release, or the material threat of a release of any hazardous substances or petroleum products into structures on the property or into the ground, groundwater, or surface water of the property. The term includes hazardous substances or petroleum products even under conditions in compliance with laws. The term is not intended to include de minimis conditions that generally do not present a material risk of harm to public health or the environment and that generally would not be the subject of an enforcement action if brought to the attention of the appropriate governmental agencies. Our study included: • A review of the chronology of ownership and site history, using county assessor records, archival property record cards, recent and historical maps, and aerial photography as primary resources. An attempt was made to identify possible former industries or uses presenting some probability of generating waste, which may have included dangerous or hazardous substances, as defined by state and federal laws and regulations. • A reconnaissance of the property to look for evidence of potential contamination in the form of soil stains, odors, vegetation stress, discarded drums, or discolored water. • The acquisition and review of available reports and other documentation pertaining to the subject property or nearby sites. • • A review of a search by Vista Information Services, Inc. (VIS) of available state and federal government records. VIS reported those sites and businesses that are located within the minimum search distances specified by American Society for Testing and Materials (ASTM) Designation E 1527. Additionally, through observations made during our site reconnaissance, we attempted to identify local topographic conditions that may influence the potential for regulated facilities to adversely impact the subject property. 3.0 SITE DESCRIPTION AND RECONNAISSANCE 3.1 Location and Legal Description The subject property is an approximately triangular-shaped parcel of land that covers 10.36 acres. It is located on a plateau approximately one-half mile southeast of downtown Renton. The Vicinity Map, Plate 1, illustrates the general location of the site. The property is situated in the northeast quarter of Section 20, Township 23 North, Range 5 East, Willamette Meridian, in King County, Washington. The tax identification number, as recorded by the King County Assessor's Office, is 202305-9110. 3.2 Site and Vicinity Characteristics • An environmental engineer from our firm visited the site on September 1, 1999 to observe on-site conditions and land use practices in the surrounding area. Land use in the immediate vicinity is characterized by single-family dwellings and a park. GEOTECH CONSULTANTS, INC. Bennett Corporation JN 9930A September 9, 1999 Page 3 • 3.2.1 Site Improvements The entire 10.36-acre lot is undeveloped. Potable water is provided by the City of Renton. Storm and sanitary sewer services are provided by the King County Department of Metropolitan Services (METRO). 3.2.2 Building Materials No structures are currently on the property. 3.2.3 Current Uses of Property The subject property is the proposed location for a high-density residential development. At present, the site is undeveloped. The southern portion of the property is covered by trees, brush, and other native vegetation. An unpaved road, now heavily overgrown, leads onto the property from the southeastern border. The northern portion of the property appears to have been excavated (see Section 4.4), then filled. This area contains some trees and is heavily overgrown by brambles. We observed construction debris (wood, plastic piping, pieces of concrete and asphalt, etc.) along with tires, bottles, furniture, yard waste, and other household items. The majority of the casual dumping appears to have taken place on the northern portion of the property. None of • the material appears to be hazardous. At the time of our site visit, no major stains, odors, or unusual vegetative conditions that might indicate the potential presence of hazardous contamination were noted on the subject property. 3.2.4 Current Uses of Adjoining Properties Land use in the site vicinity is characterized by residential development. More specifically, the property is bordered as follows: North: To the north of the subject site is the River Ridge subdivision of single- family houses constructed in 1994. East: To the east of the subject site is the Falcon Ridge subdivision of single- family houses constructed in 1989 and a parcel of undeveloped land that slopes steeply down to the northeast. South-: A gated, asphalt-paved maintenance road (Southeast Beacon Way) over- West lying the City of Seattle's Cedar River water supply pipeline runs along the southwestern border of the property. Across this road is Philip Arnold Park, then single-family residences. • During our reconnaissance, we did not observe any obvious signs of improper storage or disposal practices of hazardous waste on any of the neighboring sites that would negatively impact the subject property. GEOTECH CONSULTANTS, INC. Bennett Corporation J N 9930A September 9, 1999 Page 4 • 3.3 Hazardous Materials 3.3.1 Storage Tanks and Containers At the time of our site visit, we looked for evidence of underground or above-ground storage tanks on the subject parcel. No signs of underground or above-ground storage tanks were observed during our site reconnaissance. 3.3.2 Asbestos-Containing Materials Asbestos gained widespread use in the 1930s, 1940s, and 1950s for fireproofing, for thermal insulation, and to enhance strength, and has been used in over 3,000 commercial products. In buildings, it is most commonly found in boiler and pipe insulation, in "popcorn" ceiling texture, in vinyl flooring, in plaster and drywall compounds, in mastics and adhesives, in cement board siding, and in roofing. The knowledge that exposure to asbestos fibers can cause harm to humans became widespread between about 1955 and 1975. Diseases linked to asbestos exposure include asbestosis, a scarring of the lung tissue; lung cancer; and mesothelioma, a cancer of the lining of the chest and abdominal cavity. The EPA banned the use of asbestos in some applications in 1973, and by 1989 had announced a gradual ban on most remaining uses. Building materials imported from Canada or other areas outside • the United States may still contain asbestos. No structures are on the site. We did not observe signs of asbestos-containing materials on the property. 3.3.3 Lead-Based Paint Until the 1960's, paint containing 30 to 40 percent lead was commonly used on the interior and exterior surfaces of buildings. Exposure to particles of lead-based paint (LBP), either through inhalation or ingestion, has been found to cause a variety of adverse human health effects. Children are particularly sensitive to these effects, and chronic exposure to lead can cause learning difficulties, mental retardation, and delayed neurological and physical development. In 1977, the Consumer Products Safety Commission banned consumer use of paint products that contain lead in excess of 0.06 percent. The current LBP standard, as defined by the Lead-Based Paint Poisoning Prevention Act and the Department of Housing and Community Development Act, Title 10, is any paint or other surface coating that contains lead in excess of 1.0 milligrams per centimeter squared or 0.5 percent by weight (5,000 parts per million). No structures are on the subject property. We did not observe any signs of lead-based paint on the site. 3.3.4 PCBs • Prior to 1979, polychlorinated biphenyls (PCBs) were widely used in electrical equipment, such as transformers, capacitors, switches, fluorescent light ballasts, and voltage regulators, owing to their excellent cooling properties. In 1976, the EPA initiated GEOTECH CONSULTANTS, INC. Bennett Corporation JN 9930A September 9, 1999 Page 5 • the regulation of PCBs through the Toxic Substances Control Act (TSCA). These regulations generally control the use, manufacture, storage, documentation, and disposal of PCBs. The EPA eventually banned PCB use in 1978, and the adoption of amendments to TSCA under Public Law 94-469 in 1979 prohibited any further manufacturing of PCBs in the United States. No buildings are on the property. We did not observe any transformers on the subject property. 3.3.5 Waste Generation and Disposal No solid or hazardous waste is generated at the subject property. 3.4 Other Conditions of Concern 3.4.1 Radon Radon is a naturally occurring, highly mobile, chemically inert, radioactive gas created through the radioactive decay of uranium and thorium. The potential for the occurrence of radon varies widely and depends on: (1) the concentration of radioactive materials in the underlying bedrock, (2) the relative permeability of soils with respect to gases, and (3) the amount of fracturing or faulting in the surficial materials (EPA, 1987). The EPA has established a concentration for radon of 4 pico-Curies per liter (pC/1) of air as a maximum permissible concentration "action level." According to some studies, the average concentration in homes across the United States is on the order of 1.4 pC/I. Typically, the Puget Sound area of Washington is underlain by a consolidated thickness of glacial drift and rocks that do not contain radon-forming minerals. The Washington Department of Health, Division of Radiation Protection, published a study listing the King County average as 0.7 pC/I. Based on this information, it is our opinion that the potential for elevated levels of radon at this site is low. 3.4.2 Coal Mine Hazards Coal has been mined in several areas of King County since the late nineteenth century. Although current production is entirely from surface mines, nearly all the coal produced prior to about 1970 was from underground workings. Abandoned subsurface mine workings leave large underground voids which are hazardous in several ways. Gradual failure of the roof and sides of these voids may result in subsidence of the ground surface over a large area overlying the mines. Noxious gases and "dead air" (lacking oxygen) may also collect in these voids. In addition, animals or people may fall into surface openings, shafts, or tunnels. Unstable mine spoil piles, frequently covered with vegetation and resembling natural hills, pose hazards as well. . We reviewed a mine hazard assessment of the property prepared by HartCrowser, Inc. The report stated that the Heritage Arnold property is underlain by three coal seams, two of which have historic mine workings. The shallowest of the workings lies approximately GEOTECH CONSULTANTS. INC. Bennett Corporation A 9930A September 9, 1999 Page 6 • 250 to 300 feet beneath the surface, while the deeper workings lie 475 to 765 feet beneath the surface. There was no indication of mining on, or adjacent to, the property after the early 1920s. The HartCrowser report identified three potential mine-related hazards: trough-type settlements, sinkholes, and mine gas emissions. They concluded that sinkholes and mine gas emissions were unlikely to be problems at the property and that, although trough-type subsidence could occur, the magnitude of settlement would be unlikely to cause damage to conventionally-constructed structures. 4.0 HISTORICAL USE INFORMATION Sources reviewed for information on site and area development and land use included historic aerial photography and the resources of the King County Assessor's Office and the Puget Sound branch of the Washington State Archives. 4.1 Previous Environmental and Geotechnical Investigations Geotech Consultants, Inc. has not completed geotechnical or environmental engineering studies for the site. We were provided with a copy of an abandoned mine assessment for the site prepared by HartCrowser, Inc. that is summarized in section 3.4.2. • 4.2 Historical Maps Sanborn Fire Insurance maps do not cover the vicinity of the subject property. A U.S. Geological Survey map of the Renton Quadrangle, dated 1949, shows the subject site as a mine in an area that is otherwise undeveloped. Revisions made to the map in 1968 and 1973 show areas of residential development to the west and to the southeast. 4.3 Tax Assessor Records The King County Assessor's Office lists the current taxpayer as the Renton School District 403. According to information from the Assessor's Office, the residential subdivision to the north, River Ridge, was developed in 1994 while the subdivision to the south, Falcon Ridge (or Cedar Ridge) was developed in 1989. 4.4 State Archive Records Information on file at the archives indicates that the subject property was once part of a 32.03-acre site owned by the Puget Sound Power and Light Company. A wooden water tank, located on the present site of Philip Arnold Park, was the structure shown on the property. This large parcel was divided in 1964, and the subject site in its present size and shape was created through a second • division in 1966. It was acquired at that time by the Renton School District from Puget Properties. GEOTECH CONSULTANTS, INC. Bennett Corporation JN 9930A September 9, 1999 Page 7 • 4.5 Renton Directories Renton city directories did not cover the area of the subject property. 4.6 Aerial Photographs We reviewed aerial photographs dated 1936, 1946, 1960, 1968, 1974, 1980, 1985, 1990, and 1995. Development on the subject property and in the surrounding area for each of these years is discussed in the paragraphs that follow. 1936: In this photograph, the subject property is covered by low vegetation. An unpaved road, the City of Seattle's Cedar River Pipeline Road, runs northwest-to southeast along the southwestern border of the property. To the north is a smaller, unnamed road that winds to the southeast before splitting into small trails. Farther north is Maple Valley. A residential area covering a few blocks lies to the west. The land to the south and the east is undeveloped and covered by low vegetation. 1946: The subject site remains undeveloped and covered by low vegetation. Residential development to the west is denser. A power line right-of-way running east to west has been cleared approximately one-quarter mile to the south. • 1960: A small cleared area can be seen at the southeastern corner of the property. A baseball field appears to the west. Several housing developments can be seen to the south. 1968: The northern portion of the property has been cleared of vegetation, and appears to have been excavated. An electrical substation has been constructed approximately one-quarter mile to the south. 1974: The subject site appears unchanged from the 1968 photograph. At Philip Arnold Park to the west, a building and a parking lot have been constructed. 1980: The northern portion of the property is now covered by low vegetation. The vegetation on the remaining portion is much denser. 1985: Residential development in the area has increased greatly. 1990: The Falcon Ridge housing development now appears to the southeast of the subject site. 1995: The River Ridge housing development now appears to the north of the subject site. The site and the surrounding area appear as described in our 1999 site visit. • GEOTECH CONSULTANTS, INC. Bennett Corporation JN 9930A September 9, 1999 Page 8 • 5.0 ENVIRONMENTAL SETTING 5.1 Regional Physiographic Conditions The site is located on the Covington Drift Upland, a gently rolling, elevated drift plain in the Puget Sound Lowland geomorphic province. The Puget Sound Lowland is a basin lying between the Cascade Mountains to the east and the Olympic Mountains to the west and is covered mainly by glacially-deposited sediments. The plain was formed during the last period of continental glaciation that ended approximately 13,500 years ago. The site lies near the northwestern corner of the upland plain at an approximate elevation of 400 feet above sea level. 5.2 Soil and Geologic Conditions A published geologic map for the site vicinity suggests that much of the material underlying the subject site is glacial till, a dense, heterogeneous mixture of silt, sand, and gravel. Typically, the till exhibits relatively low vertical hydraulic conductivity, which frequently results in formation of a perched water table along its upper contact. The perched water table (if present) is frequently seasonal and derives recharge primarily from infiltration of precipitation through more permeable overlying soils. Geotech Consultants, Inc. is preparing a geotechnical engineering study of the site that will discuss subsurface conditions in greater detail. 5.3 Hydrogeologic Conditions The geologic unit that we assume characterizes the site is of relatively low permeability, although unmapped deposits of higher permeability sand and gravel may occur within this unit. Based upon local drainage patterns and upon our review of a U.S. Geological Survey map of the area, it is likely that the flow of surface, or shallow-seated subsurface, water across the property would be toward the northwest to the Cedar River. According to a U.S. EPA Ground Water Handbook, shallow water tables typically conform to surface topography. 6.0 RECORDS REVIEW Geotech Consultants, Inc. utilized the services of Vista Information Services, Inc. (VIS) to complete a search of available state and federal government records. VIS reported those sites and businesses that are located within the minimum search distances specified by American Society for Testing and Materials (ASTM) Designation E 1527. Additionally, through observations made during our site reconnaissance, we attempted to identify local topographic conditions that may influence the potential for regulated facilities to adversely impact the subject property. The databases searched by VIS, as well as the search areas applied to each, are summarized in the following sections. A copy of the VIS Site Assessment is included with this report as an appendix. • GEOTECH CONSULTANTS. INC. Bennett Corporation JN 9930A September 9, 1999 Page 9 • 6.1 Federal Records Sources 6.1.1 NPL One site within a one-mile radius of the subject property is found on the National Priority List. That site, Pacific Car and Foundry at 1400 North 4th Street, is located approximately one mile to the north. Based upon its distance from the Heritage Arnold property and its crossgradient hydrologic position, any risk it may pose appears to be very low. 6.1.2 CERCLIS A review of the EPA's CERCLIS listing reveals no active sites within approximately one- half mile of the subject property that have been designated as potentially hazardous or eligible for participation in the Superfund cleanup program. 6.1.3 ERNS The subject property does not appear on the Emergency Response Notification System (ERNS) database of spill response activities. 6.1.4 FINDS • A review of the Facility Index System (FINDS) listing and the EPA's RCRA Notifiers list, along with our site and area reconnaissance, reveals no RCRA-regulated businesses on the subject property, on adjacent sites, or within a one-eighth mile radius. 6.1.5 TSD A review of the RCRIS-TSD list shows no sites within a one-mile radius of the subject property. 6.2 State Records Sources 6.2.1 WDOE Underground Storage Tanks A review of the WDOE listing of underground storage tanks (USTs) reveals no registered USTs on, or adjacent to, the subject property. 6.2.2 WDOE Leaking Underground Storage Tanks A review of the current Leaking Underground Storage Tank (LUST) list reveals no sites within a half-mile radius of the subject property that have reported releases of petroleum into the environment. • 6.2.3 WDOE Hazardous Site Listings A review of the WDOE Confirmed & Suspected Contaminated Sites (C&SCS) report GEOTECH CONSULTANTS. INC. Bennett Corporation JN 9930A September 9, 1999 Page 10 • shows one site within an approximate one-mile radius of the subject property that has been designated as a confirmed hazardous substance site. This site, Northwest Pipeline at 800 South 21 st Street, is situated approximately seven-eighths of a mile to the southwest, in a crossgradient hydrologic position. Based upon the distance separating it from the Heritage Arnold property and upon its relative hydrologic position, it is not considered a source of potential contamination to the subject property. 6.2.4 WDOE Toxics Site Listings A review of the WDOE Toxics site listing shows two sites within a one-half-mile radius of the subject property that have submitted reports to WDOE describing independent cleanup activities. Both sites are approximately one-half mile from the subject site, and are in cross- to downgradient hydrologic positions. Based upon the distances separating them from the Heritage Arnold property and upon their relative hydrologic positions, they are not considered sources of potential contamination to the subject property. 6.3 Local Agency Sources A statewide listing of municipal solid waste facilities does not record any active landfills in this area. A review of the Seattle-King County Health Department records pertaining to current and • abandoned landfills within the county suggests that two closed landfills are located within one mile of the subject property. The Mount Olivet Landfill is located three-quarters of a mile to the north- northeast, and the.Renton Highlands Landfill is located approximately one mile to the northeast. Both landfills are located across Maple Valley from the subject site. Based upon the distances separating them from the Heritage Arnold property and the intervening valley, they are not considered sources of potential contamination to the subject property. 6.4 Assumptions and Opinion of Contaminant Mobility and Site Vulnerability No sites confirmed to be contaminated by hazardous waste lie within 1,000 feet of the subject property in an upgradient hydraulic position. As such, it is our professional opinion that the potential for the migration of theoretical water-borne contamination onto the subject property is very low. 7.0 RESULTS OF INVESTIGATION We performed a Phase 1 Environmental Site Assessment, consistent with the scope and limitations of ASTM Designation E 1527, for the property at Beacon Way Southeast in Renton, Washington. 7.1 Findings • This assessment revealed no evidence of recognized environmental conditions in connection with the property. GEOTECH CONSULTANTS, INC. Sennett Corporation A 9930A September 9, 1999 Page 11 7.2 Conclusions and Recommendations As stated earlier, the northern portion of the property was excavated, then filled with as much as 12 feet of imported material that included construction debris. It may be prudent to include a contingency in development plans, should contaminated material be discovered during future excavation. 7.3 Limitations This report has been prepared for the exclusive use of the Bennett Corporation, and its representatives, for specific application to this site. This work was performed in a manner consistent with that level of care and skill normally exercised by members of the environmental science profession currently practicing under similar conditions in the area. Our work is in accordance with our Fee Schedule and General Conditions and our signed proposal, which is dated August 18, 1999. 8.0 REFERENCES Bishop, Greg, Turnberg, Wayne L., and VanDusen, Karen. Abandoned Landfill Study in King County. Seattle-King County Department of Public Health. Seattle, Washington. April 1985. • Department of Interior, U.S. Geological Survey. Topographic Map of the Renton, Washington Quadrangle. 1983. Division of Radiation Protection, Department of Health, State of Washington. Radiation Fact Sheet. HartCrowser, Inc. Abandoned Mine Assessment, Heritage Arnold Property, Renton, Washington. August 16, 1999. King County, Environmental Division. Sensitive Areas Map Folio. December 1990. Office of Research and Development, U.S. EPA. U.S. EPA Ground Water Handbook - Volume 1: Ground Water and Contamination. EPA/625/6-90/016a. September 1990. Waldron, Howard H., Liesch, Bruce A., Mullineaux, Donal R., and Crandell, Dwight R. Preliminary Geologic Map of Seattle and Vicinity, Washington. U.S. Geological Survey. 1962. • GEOTECH CONSULTANTS, INC. r U I thletic U \`Meld • �' \ i 3pfi, ", ------ i j 0 \` } ,. —�' Greenwood Cerq BM i I asebal \( r Cem i 0 �•y Park t T-11 oc a r I - A _ .it • _ - ) Y Ap r,� • fir, :! �• \I �� _ 1,\ Set i-=--� ,>fd �C�`` ��s�' � \��':/�j •• � o� 1 Aqv \boa - .'rh •\ rl ) II I o Mzxl 04 4 416- ;ervoir ' z _N Scale 0 112 1 m1/e X, Inferred Direction of Shallow Groundwater Flow (Source:U.S.Geologic Sunray map of Renton,Washington Quadrangle,1973) VICINITY MAP GEOTECH Proposed Heritage Arnold Project CONSULTANTS,INC. Beacon Way Southeast Renton,Washington F No: 1 "arsffpt 1399 Plate: 0--x1 N • River Ridge residential development s-•---•—•—•—•—•—•—•—•—•—•---•—•—•—•—•—•—•—•—•-- •�• brambles - trees and 1 gate. �`.� brush steep, wooded slope N. i approximate area tq. *-* �.` of excavation O GL---------------------------� parking d`��e•` --- 1 lot 1 co` y` brambles 1 •� trees and Philip 011P brush I Falcon Arnold Pa Park °d�� 1 Ridge c ! residential • °°d,,�• I development baseball fields d�o�°,.�.�'�• J undeveloped land SITE PLAN G''Ej OTj CH Proposed Heritage Arnold Project CONSULTANTS,INC. Beacon Way Southeast Renton,Washington dob A6o: Dot P/at 99330A Sept_1999 No Scale 2 - - ��.0 rye' -war• ? =� � Y 7il -'•P�.Ya MO +•r SYy` •• - +_ fit.�i-� �� ia �a I I • • 1 • t I • 1 •1 1 h a ,¢` '$ 'pia `•,.6. �.� ` Y i • I' t I 1 I • t • I • • •� .s_ I r - + it 4 �•s j �1. If �R"J r {!A ',. �Las '.. } "�', (A•y t _".�{ q, :.i/r. ���:.>� �. sIX SITE � �iR� �ti S :in s��• - � �s3 r- - �Il'.t .r ,.C.1�- .K r,... s r ;3•+'t a� '. [ � .♦ ,. � 1 cam,-^p, . � t s� .. PHOTOGRAPHS Proposed Heritage Arnold Project IBeacon Way Southeast Renton, • • • APPENDIX V/S's Site Assessment • • GEOTECH CONSULTANTS, INC. SITE ASSESSMENT REPORT PROPERTY CLIENT INFORMATION INFORMATION Project Name/Ref#: 99330A Ryan Fike Proposed Heritage Arnold Project Bennett Corporation Beacon Way Southeast 9 Lake Bellevue Dr., Suite 204 Renton, WA 98055 Bellevue, WA 98005 Latitude/Longitude: 47.473422, 122.192681 Site Distribution Summary within1/8 1/8to 114to vzlo mile 114 mile 112 mile I mile ' Agency/Database -Type of Records A) Databases searched to 1 mile: US EPA NPL National Priority List 0 0 0 1 US EPA CORRACTS RCRA Corrective Actions and (TSD) associated TSD 0 0 0 0 STATE SPL State equivalent priority list 0 0 0 1 B) Databases searched to 1/2 mile: • STATE SCL State equivalent CERCLIS list 0 0 0 - US EPA CERCLIS / Sites currently or formerly under NFRAP review by US EPA 0 0 0 - US EPA TSD RCRA permitted#treatment, storage, disposal facilities 0 0 0 - STATE LUST Leaking Underground Storage Tanks 0 0 0 - STATE SWLF Permitted as solid waste landfills, incinerators, or transfer stations 0 0 0 - STATE TOXICS Washington Site Register 0 0 2 - C) Databases searched to 1/4 mile: STATE UST Registered underground storage tanks 0 0 - - D) Databases searched to 1/8 mile: US EPA ERNS Emergency Response Notification System of spills 0 - - US EPA LG GEN RCRA registered large generators of hazardous waste 0 - - - US EPA SM GEN RCRA registered small generators of hazardous waste 0 - - - For more information call VISTA Information Solutions, Inc. at 1 -800-767 -0403. 41 Report ID: 99330Al11 Date of Report: September 3, 1999 Version 2.6.1 Page 17 (This report meets the ASTM standard E-1527 for standard federal and state government database research in a Phase I environmental site assessment. A (-) indicates a distance not searched because it exceeds these ASTM search parameters. • LIMITATION Of LIABILITY Customer proceeds at its own risk in choosing to rely on VISTA services,in whole or in pan,prior to proceeding with any transaction. VISTA cannot be an insurer of the accuracy of the information,errors occurring in conversion of data,or for customer's use of data. VISTA and its affiliated companies,officers,agents,employees and independent contractors cannot be held liable for accuracy, storage,delivery,loss or expense suffered by customer resulting directly or indirectly from any information provided by VISTA I NOTES 4.0 For more information call VISTA Information Solutions, Inc. at 1 -800-767-0403. Report ID: 99330Al 11 Date of Report:September 3, 1999 Version 2.6.1 Page F2 SITE ASSESSMENT REPORT Map of Sites within 1 Mile z N i N 4th t \ rio -t I N cJ O C 2n t Ne 3rd St E U P e 2nd St o To 2 C D \ S % dSt StteH m 0 �� ro S ............... St h S 6t S o St e 2 t S > r` Q sad a � rP 1 4 5 15t t Cn 18th Sco S 19t St Q `D s e 57 S 2 t P `° 7 o r. _.v> D cn 1 Se _ S d St (n e t Se n -e 0 0.25 0.5 St S 5 26t o t ��� 2 t e 163rd Mites Category: A B C D Subject Site Databases Searched to: 1 mi. 1/2 mi. 1/4 mi. 1/8 mi. Single Sites 0 Xj'. O Multiple Sites a 0 �\ Highways and Major Roads NPL,SPL, CERCLISI UST ERNS, Roads CORRACTS NFRAP, GENERATORS Railroads (TSD) TSD, LUST, Rivers or Water Bodies SWLF,SCL • Utilities For More Information Call VISTA Information Solutions, Inc. at 1 -800-767-0403 Report ID:9933OAl11 Date of Report: September 3, 1999 Page 13 SITE ASSESSMENT REPORT Sites Represented as Polygons Q N M 4 z N t N v p Zn t Ne 3rd St W e 2nd St \ o o To St a' ID S2dSt cn St tel77 ' ,' ................ _ S Sth St S 61l S 7ff S a o � (� N < D P d CD (<D C� • 5 � �dek \� �� i 4 c U-) cn -p a 07 \ a> Q c cn fl 18th S �, o � P ID �, v S 19t St - e 57 S 2 t P I o .— a) � 1 Se V'cn � — S 5d St e t Se n S e °' 0 0.25 0.5 S 26t St o t �� S z t e 163rd Miles These boundaries are approximated from agency records or other sources such as published maps. They may represent property boundaries, impact zones,or study areas. For more information contact the agency referenced by source number in the site listing. �\ Highways and Major Roads Roads Subject Site Railroads • Rivers or Water Bodies Utilities For More Information Call VISTA Information Solutions, Inc. at 1 -800-767-0403 Report ID:9933OA111 Date of Report: September 3, 1999 PVe 04 SITE ASSESSMENT REPORT • Street Map N 14tSt Q) \ rio ..t o � 2n t o Ne 3rd St W e 2nd St Tp Ct a > CD < � •z z � Qi S2 dSt = (D St �x �� P yif I6 ti! ....... S Sfh St " S 6ff S t S _ > o (D • z Gtod W c� � � ���Q '� < 1 4 5 CD 7dek �� `tee _ �gIle � 15t dlo Q `v51 CDCn U v o a} a> Q c cn o V < 18th S �y o {6� P o �, v S 19t St d �° s e 57 �t.. S 2 1 P 1 Se t S d St t Se n e o t 0 0.25 0.5 S 2 S 26{ St e 163rd Miles t �\ Highways and Major Roads Subject Site Roads Railroads Rivers or Water Bodies Utilities • For More Information Call VISTA Information Solutions, Inc. at 1 -800-767-0403 Report ID:99330Al11 Date of Report: September 3, 1999 Page#5 SITE ASSESSMENT REPORT • SITE INVENTORY A B C D PROPERTY AND THE ADJACENT AREA o a MAP (within 1/8 mile) C ID Z U N VISTA ID U L. H (� DISTANCE a O a V uii O H = 0 n DIRECTION Z U H CAU 4 � H f- W V1 No Records Found A; B C D SITES IN THE SURROUNDING AREA p^ a MAP (within 1/8- 114 mile) ID Z U N N Z W VISTA/D C U u• V y 0 DISTANCE m O a U W H O H (� DIRECTION Z U H N U :f- V) W H. No Records Found A B C D' • SRES IN THE SURROUNDING AREA 0 a MAP (within 114-1/2 mileU. ); G ID Z U h H Z ZUjL VISTA ID U 4. C1 H C7 DISTANCE a O a U W ?r O H (� DIRECTON Z U VN V1 U ►- J H I W H STONEWAY CONCRETE RENTON 6808683 1 1915 SE MAPLE VALLEY HWY 0.47 NI X • RENTON, WA 98056 PUGET SOUND POWER LIGHT RENTON 342043 2 620 S GRADY WAY 0.48 1 X RENTON, WA 98055 A B C D SITES IN THE SURROUNDING AREA p^ a MAP (within 1/2- 1 mile) H ID U z H H Z W Uj J VISTA ID U � X V! CD a DISTANCE a O - U W O h 0 DIRECTION Z U N U V) ►.- W � 0: NORTHWEST PIPELINE SEATTLE 2883006 3 800 S 21 ST ST 0.875 11 X • RENTON, WA 98055 X=search criteria; • =tog along (beyond search criteria). For more information call VISTA Information Solutions, Inc. at 1 -800-767-0403. Report ID: 99330Al 11 Date of Report:September 3, 1999 Version 2.6.1 Page 16 A B C D SITES IN THE SURROUNDING AREA o a. MAP (within 1/2 - 1 mile) C • ID z z z J W W VISTA 10 U I LL. DISTANCE pJ, O a ((j W Ln _ �: O Ix0 � N DIRECTION z U to cn U t- J En ►- W h PACIFIC CAR FOUNDRY CO 4864595 4 1400 N 4TH ST 0.99 MI X • RENTON, WA 98055 X=search criteria; • =tog along (beyond search criteria). For more information call VISTA Information Solutions, Inc. at 1 -800-767-0403. Report ID:99330Al 11 Date of Report September 3, 1999 Version Z6,r Page 17 A B C D UNMAPPED SITES V) • U Z � N Z Z J W W U U V) VISTA 1D Z O V) V> U I 0 = H � W No Records Found X=search criteria; • =tog along (beyond search criteria). For more information call VISTA Information Solutions, Inc. at 1 -800-767 -0403. Report ID: 99330Al11 Date of Report: September 3, 1999 Version 2.6.1 Page 18 SITE ASSESSMENT REPORT • DETAILS PROPERTY AND THE ADJACENT AREA (within 1/8 mile) No Records Found SITES IN THE SURROUNDING AREA(within 1/8 - 1/4 mile) No Records Found SITES IN THE SURROUNDING AREA(within 1/4- 1/2 mile) VISTA STONEWAY`CONCRETE`RENTON VISTA ID# 6808683 MapID Address': Distance/Direction: 0.47 MI/ N 1915 SE MAPLE VALLEY HWY Plotted as Point RENTON,WA 98056 WA Toxics-Washington Toxics/SRC#5911 EPA/Agency ID: N/A ' Agency Address: STONEWAY CONCRETE 7915 SE MAPLE VALLEY HIGHWAY RENTON,WA 98055 • Region: NORTHWEST State Detail Description: NO Contact: NOT REPORTED Description: WASTE:METALS Description: WASTE.PETROLEUM PRODUCT Description: WASTE:NON-HALOGENATED SOLVENTS Description: DATE ECOLOGY RECEIVED REPORT.'6/27/90 .Description: MEDIA:SOIL Description: REPORT TYPE:FINAL Description: ISSUE OF SITE REGISTER:90-07 VISTA PUGET SOUND POWER LIGHT RENTON VISTA ID#: 342043 Map ID Address': Distance/Direction: 0.48 MI/W 620 S GRADY WAY Plotted as: Point RENTON, WA 98055 WA Toxics-Washington Toxics/SRC#5911 EPA/Agency ID: N/A Agency Address: PUGET SOUND ENERGY 620 S.GRADY WAY RENTON,WA 98055 Region: NORTHWEST State Detail Description: NO Contact: NOT REPORTED Description: WASTE:POLYCHLORINATED BIPHENYLS Description: WASTE:POLYNUCLEAR AROMATIC HYDROCARBONS VISTA address includes enhanced city and ZIP. For more information call VISTA Information Solutions, Inc.at 1 -800-767-0403. Report ID: 99330Al11 Date of Report:September 3, 1999 Version 2.6.1 Page 19 SITES IN THE SURROUNDING AREA (within 1/4 - 1/2 mile) CONT. DesCriptlOn: DATE ECOLOGY RECEIVED REPORT.7122198 • Description: MEDIA:SOIL Description' MEDIA:SEDIMENTS Description: REPORT TYPE:INTERIM Description: ISSUE OF SITE REGISTER:98-06 Description: WASTE:POLYCHLORINATED BIPHENYLS Description: WASTE:POLYNUCLEAR AROMATIC HYDROCARBONS Description: DATE ECOLOGY RECEIVED REPORTA130/98 Description: MEDIA:GROUNDWATER Description: MEDIA:SOIL Description: REPORT TYPE:INTERIM Description: ISSUE OF SITE REGISTER:98-07 SITES IN THE SURROUNDING AREA(within 1/2- 1;mile) VISTA NO PIPELINE SEATRE VISTA ID#': 2883006 MaplD Address': Distance/Direction: 0.87 MI/SW 800 S 21ST$T Plotted as: Point RENTON, WA 98055 SPL-State E uivalent Priority List/SRC#5429 Agency ID: 2392 WARM 3 Agency Address: SAME AS ABOVE Status: UNKNOWN Facility Type: NOTAVAILABLE • Lead Agency: NOTAVAILABLE State Status: NOTAVAILABLE Pollutant 1' EPA PRIORITY POLLUTANTS-METALS CYANIDE Pollutant 2: PESTICIDE Pollutant 3: UNKNOWN `VISTA address includes enhanced city and ZIP. For more information call VISTA Information Solutions, Inc. at 1 -800 -767-0403. Report ID: 99330Al11 Date of Report: September 3, 1999 Version 2.6.1 Page 110 SITES IN THE SURROUNDING AREA (within 1/2 - 1 mile) CONT. • ;VISTA PACIFIC CAR FOUNDRY CO VISTA ID#: 4864595 Map io Address*: Distance 0.99 MI 1400 N 4TH ST RENTON, WA 98055 Plotted as: Polygon 4 NPL - National Priority List/SRC#5900 EPA ID: WAD009249210 Agency Address: PACIFIC CAR FOUNDRY CO. 1400 N 4TH ST RENTON,WA 98055 EPA Region: 0 i Congressional District: 0 Federal Facility: Agency Code�) Facility Ownership: NOT AVAILABLE Site Incident Category: unknown Federal Facility Docket: Agency code() NPL Status: UNKNOWN Incident Type: Unknown Proposed NPL Update#: 0 Final NPL Update#: 0 Financial Management System ID: NOT REPORTED Latitude: 0 Longitude: 0 Lat/Long Source: Agency code() Lat/Long Accuracy: Unknown Dioxin Tier: Unknown USGS Hydro Unit: 0 • RCRA Indicator; Unknown Alias Name: PACCAR Alias Street: NOT REPORTED Alias City: NOT REPORTED Alias Latitude: 0 Alias Zip: NOT REPORTED Alias Longitude: 0 Alias State: NOT REPORTED Alias Name: PACIFIC CAR FOUNDRY CO Alias Street: NOT REPORTED Alias City: KING Alias Latitude: 4729200 Alias Zip: NOT REPORTED Alias Longitude: 12211470 Alias State: NOT REPORTED 'VISTA address includes enhanced city and ZIP. For more information call VISTA Information Solutions, Inc. at 1 -800-767 -0403. Report ID: 99330Al11 Date of Report:September 3, 1999 Version 2.6.1 Page ill UNMAPPED SITES • No Records Found 'VISTA address includes enhanced city and ZIP. For more information call VISTA Information Solutions, Inc. at 1 -800-767 -0403. Report ID: 99330Al11 Date of Report:September 3, 1999 Version 2.6.7 Page 012 SITE ASSESSMENT REPORT • TI R DESCRIPTION OF DATABASES SEARCHED C �A) DATABASES SEARCHED TO 1 MILE i NPL VISTA conducts a database search to identify all sites within 1 mile of your property. SRC#:5900 The agency release date for NPL was May, 1999. The National Priorities List(NPL) is the EPA's database of uncontrolled or abandoned hazardous waste sites identified for priority remedial actions under the Superfund program.A site must meet or surpass a predetermined hazard ranking system score, be chosen as a state's top priority site, or meet three specific criteria set jointly by the US Dept of Health and Human Services and the US EPA in order to become an NPL site. SPL VISTA conducts a database search to identify all sites within 1 mile of your property. SRC#:5429 The agency release date for Confirmed Contaminated Sites Report was November, 1990. The Washington Confirmed Contaminated Sites Report contains a WARM (Washington Ranking Model) BIN Number of 0-5 which is assigned to an NPL site designating it as a State Priority Site. CORRACTS VISTA conducts a database search to identify all sites within 1 mile of your property. SRC#:5896 The agency release date for HWDMS/RCRIS was May, 1999. The EPA maintains this database of RCRA facilities which are undergoing "corrective action". A"corrective action order" is issued pursuant to RCRA Section 3008 (h) when there has been a release of hazardous waste or constituents into the environment from a RCRA facility. Corrective actions may be required beyond the facility's boundary and can be required regardless of when the release occurred, even if it predates RCRA. B) DATABASES SEARCHED TO 1/2'MILE CERCLIS VISTA conducts a database search to identify all sites within 112 mile of your property. SRC#: 5790 The agency release date for CERCLIS was March,1999. The CERCLIS List contains sites which are either proposed to or on the National Priorities List(NPL) and sites which are in the screening and assessment phase for possible inclusion on the NPL.The information on each site includes a history of all pre-remedial, remedial, removal and community relations activiies or events at the site, financial funding information for the events, and unrestricted enforcement activities. For more information call VISTA Information Solutions, Inc. at 1 -800- 767-0403. Report ID: 99330Al 11 Date of Report September 3, 1999 Version 2.6.1 Pagel 73 NFRAP VISTA conducts a database search to identify all sites within 112 mile of your property. SRC#: 5791 The agency release date for CERCLIS-NFRAP was March, 1999. • NFRAP sites may be sites where, following an initial investigation, no contamination was found, contamination was removed quickly, or the contamination was not serious enough to require Federal Superfund action or NPL consideration. SCL VISTA conducts a database search to identify all sites within 112 mile of your property. SRC#: 5428 The agency release date for Suspected Contaminated Sites Report was November, 1998. The Washington Suspected Contaminated Sites Report is not assigned a WARM (Washington Ranking Model) BIN Number, designating these sites a contaminated site. The Washington Affected Media and Contaminants Report includes sites in the following categories: (1) National Priorities List(NPL) Sites, Federal Lead; (2) National Priorities List (NPL) Sites, State Lead; (3) State Sites, Confirmed Hazardous Substances Sites (sites where the presence of hazardous substances has been confirmed by laboratory or field determinations; (4) Potential Hazardous Substance Sites, these sites have been reported to the Department of Ecology and further investigation including sampling is underway; (5) State Sites Under-going Long-Term Monitoring; and (6) Sites For Which Cleanup is Complete.This report includes some leaking underground storage tank sites. RCRA-TSD VISTA conducts a database search to identify all sites within 112 mile of your property. SRC#: 5896 The agency release date for HWDMS/RCRIS was May, 1999. The EPA's Resource Conservation and Recovery Act(RCRA) Program identifies and tracks hazardous waste from the point of generation to the point of disposal.The • RCRA Facilities database is a compilation by the EPA of facilities which report generation, storage, transportation, treatment or disposal of hazardous waste. RCRA TSDs are facilities which treat, store and/or dispose of hazardous waste. SWLF VISTA conducts a database search to identify all sites within 112 mile of your property. SRC#:5619 The agency release date for Municipal Solid Waste Facilities was September, 1998. This database is provided by the Department of Ecology, Solid Waste Services Program. The agency may be contacted at: 360-407-6133. The Washington Solid Waste Inventory does not provide facility locations. LUST VISTA conducts a database search to identify all sites within 112 mile of your property. SRC#:5910 The agency release date for Leaking Underground Storage Tank List was May, 1999. This database is provided by the Department of Ecology, Toxics Cleanup Program. The agency may be contacted at: 360-4077179 . The Washington Department of Ecology Leaking Underground Storage Tank List contains some of the same sites included on the Regional lists. This list is being used because there are some"new"sites and it includes a site identification number. Because two lists are being used, sites may be reporting twice. For more information call VISTA Information Solutions, Inc. at 1 -800-767 -0403. Report ID: 9933OAl11 Date of Report: September 3, 1999 Version 2.6.7 Page 114 WA Site VISTA conducts a database search to identify all sites within 1/2 mile of your property. Register The agency release date for Toxic Cleanup Program Site Register was May, 1999. • SRC#: 5911 This database is provided by the Department of Ecology, Toxics Cleanup Program. The agency may be contacted at: 360-407-7200. The Washington Site Register Toxics Cleanup Program report details activities related to the study and cleanup of hazardous waste sites under the Model Toxics Control Act. Note that the State of Washington cautions that information contained under the Site Description is summarized information from an Independent Report and the Department of Ecology is not responsible for the accuracy of these reports.This report includes some leaking underground storage tank sites. C) DATABASES SEARCHED TO 1/4 MILE UST's VISTA conducts a database search to identify all sites within 1/4 mile of your property. SRC#:5909 The agency release date for Underground Storage Tank Database was May, 1999. This database is provided by the Department of Ecology, Solid Hazardous Waste Program. The agency may be contacted at: 360-407-7179; Caution-Many states do not require registration of heating oil tanks, especially those used for residential purposes. D) DATABASES SEARCHED TO 1/8 MILE ERNS VISTA conducts a database search to identify all sites within 1/8 mile of your property. SRC#:5598 The agency release date for was December, 1998. • The Emergency Response Notification System (ERNS) is a national database containing records from October 1986 to the release date above and is used to collect information for reported releases of oil and hazardous substances.The database contains information from spill reports made to federal authorities including the EPA, the US Coast Guard, the National Response Center and the Department of Transportation. The ERNS hotline number is (202) 260-2342. RCRA-LgGen VISTA conducts a database search to identify all sites within 1/8 mile of your property. SRC#:5896 The agency release date for HWDMS/RCRIS was May, 1999. The EPA's Resource Conservation and Recovery Act(RCRA) Program identifies and tracks hazardous waste from the point of generation to the point of disposal. The RCRA Facilities database is a compilation by the EPA of facilities which report generation,storage,transportation, treatment or disposal of hazardous waste. RCRA Large Generators are facilities which generate at least 1000 kg./month of non-acutely hazardous waste (or 1 kg./month of acutely hazardous waste). RCRA-SmGen VISTA conducts a database search to identify all sites within 1/8 mile of your property. SRC#:5896 The agency release date for HWDMS/RCRIS was May, 1999. The EPA's Resource Conservation and Recovery Act(RCRA) Program identifies and tracks hazardous waste from the point of generation to the point of disposal. The RCRA Facilities database is a compilation by the EPA of facilities which report generation, storage, transportation, treatment or disposal of hazardous waste. RCRA Small and Very Small generators are facilities which generate less than 1000 kq./month of non-acutely hazardous waste. For more information call VISTA Information Solutions, Inc. at 1 -800-767 -0403. 41 Report ID: 99330Al11 Date of Report:September 3, 1999 Version 2.6.1 Page J75 End of Report • • For more information call VISTA Information Solutions, Inc. at 1 -800-767 -0403. WW Report ID: 99330Al11 Date of Report: September 3, 1999 'T Version 2.6.1 Page#16 i� • 6.5 ABANDONED MINE ASSESSMENT BY HART CROWSER DATED AUGUST 23, 1999 AM dR6WSrzR Hart Avenue er,last V.W7910 Fairview Avenue East Seattle,Washington 98102-3699 Fax 206,328.5581 Tel 206.324.9530 Earth and Environmental Technologies J-7179 August 23, 1999 Mr. Ryan Fike, Project Administrator Bennett Corporation 9 Lake Bellevue Drive, Suite 204 Bellevue, WA. 98005 Re: Abandoned Mine Assessment Heritage Arnold Property Renton, Washington Dear Mr. Fike: This letter report presents Hart Crowser's assessment of abandoned underground coal mines related to prospective development of the Heritage Arnold property in Renton. We understand that you are considering potential residential development of approximately 10.4 acres located near South 7th Avenue and Jones Avenue South, in the NW '/4 of the NW 1/4 of Section 20, T 23 N, R 5 E. The purpose of Hart Crowser's work was to assess potential development constraints, if any, related to abandoned underground coal mine workings at the site based on available information, and provide geotechnical recommendations. Hart Crowser's scope did not include completion of any subsurface borings or tests at the site. Prior to beginning work, Hart Crowser informally contacted the City of Renton Planning Department to inquire about general requirements for developing areas which may be affected by abandoned underground mines. We were advised that the City does not have specific requirements related to development proposals involving abandoned mine lands, but would expect • that area to be addressed through a geotechnical engineering report. Seattle•Tacoma•Richland•Anchorage•Portland•Denver•Honolulu•San Francisco•Long Beach•San Diego-Mexico City am ALAF • Bennett Corporation 1-7179 August 23, 1999 Page 2 This report is divided into the following sections: ► SUMMARY; ► AVAILABLE MINE INFORMATION; ► REPORTED MINE-RELATED HAZARDS; ► EVALUATION OF POTENTIAL FUTURE SUBSIDENCE; ► GENERAL RECOMMENDATIONS FOR SITE DEVELOPMENT; and ► USE OF THIS REPORT. Figures are included following the main text of this report. Figure 1 shows location of the site. Figure 2 shows a site plan with the principal mine tunnels. Figure 3 presents a diagrammatic cross section of the mine workings. SUMMARY • The property is underlain by three coal seams with reported mine workings located in the upper (No. 1) coal seam and lowest(No. 3) coal seam. Elsewhere in Renton, the intermediate (No. 2) coal seam has also been mined, but apparently not in close proximity to the Heritage Arnold property. Depth of the No. 1 Seam mine workings varies from about 250 to 300 feet in the western part of property, while the No. 3 Seam workings range between about 475 to 765 feet in depth and extend across the entire property. Mining in Renton occurred over a period ranging from around 1875 to 1955. Hart Crowser did not find any indication of mining on or immediately adjacent to the Heritage Arnold property after the early 1920s. Typically mine subsidence occurs relatively soon after mining, as discussed in this report The US Department of Interior, Office of Surface Mining (OSM) has recorded less than about a dozen incidents of mine subsidence and other hazards related to the abandoned mines in Renton since 1982, most of which involve relatively shallow workings, and none of which involve the Heritage Arnold property. Available information on subsurface conditions at the Heritage Arnold site from mine maps and other sources is very limited, but appears to be reasonably consistent Hart Crowser is not aware of any deep borings or rock test data for the area. As a result, only general estimates of potential for subsidence and magnitude of surface movements can be accomplished within the limits of available information, as discussed later in this report. Comparison with statistical evaluations from other • fir♦ • Bennett Corporation )-7179 August 23, 1999 Page 3 sites suggests this subsidence has most likely already occurred, and any future ground movements are likely to be a fraction of the calculated values discussed in this report Hart Crowser considered three potential types of mine hazard that could occur at the site: trough- type settlements which could damage structures, pavements or utilities over a long period of gradual settlement; sinkholes (sudden ground collapse over a local area); and mine gas emissions. Trough-type subsidence could occur at the site, but in our opinion is unlikely to cause ground movements sufficiently large to damage conventionally constructed structures. Statistical evaluation of trough subsidence in other parts of the US has consistently demonstrated that more than 90 percent of subsidence events occur within about 70 to 80 years after mining; the mine workings underlying the Heritage Arnold property are believed to have been completed more than 75 years ago. Empirical analysis of maximum potential trough-type subsidence at the Heritage Arnold property, using worst case assumptions of: 1) no subsidence to date, 2) discontinuous mining, and 3) superposition of subsidence effects from adjacent seams, shows some potential of ground movements in the western part of the site that would require special construction under regulations used by King County and the City of Bellevue. Actual future settlement and ground strain are likely to be considerably less than these threshold values. Potential future development of sinkholes at the site is also not likely to occur, in our opinion. This is because of the time elapsed since mining and because depth of the shallowest workings at the site is more than two-and-a-half times the maximum depth of previous sinkholes reported in western Washington. Mine gas emissions are unlikely to be a problem for structures constructed with vapor barriers and good crawl space ventilation.The only reported occurrence of mine gas problems in the Renton area actually occurs not far from the site, and could be related to workings on the No. 1 Seam which extend onto the Heritage Arnold property. However, the depth of these workings on the site is more than five times the depth where the gas problem occurs, and overall mine gas problems are extremely rare in western Washington. Depth of the mine workings underlying the Heritage Arnold property is generally quite a bit more than other mine workings where problems have occurred within the City of Renton. While it isn't possible to prove there is no chance of future mine-related problems at the site, there is no clear basis for anticipating future mine hazards would arise at this site that are similar to problems which have occurred elsewhere in the City. • �r • Bennett Corporation J-7179 August 23, 1999 Page 4 In Hart Crowser's opinion, it is reasonable to develop the Heritage Arnold property using conventional construction, with little risk of future mine-related problems. AVAILABLE MINE INFORMATION Information on abandoned underground mines at the Heritage Arnold site includes the Washington Department of Natural Resources mine map archives, a 1985 Morrison Knudsen investigation for OSM, and Bulletin No. 3, a 1912 report prepared by G. W. Evans for the Washington Geological Survey(see reference list at the end of this report). Three historically mined coal seams underlie the Heritage Arnold site, typically dipping a little south of east at about 10 to 12 degrees below horizontal. The coal beds occur within a series of folded and faulted sandstones, and shales, but there is little or no information on the engineering characteristics of these rocks. • Mining in the No. 1 Seam on or immediately adjacent to the property was accomplished by the Denny Renton Clay& Coal Co. from at least 1911 through 1918, and may have began earlier. The mining mostly extended to the west, but was close enough that surface subsidence effects might have occurred on the Heritage Arnold property. The Denny Renton Coal & Clay Co. map designated K30 A shows a somewhat unconventional mining pattern of driving"planes" up dip and mining laterally, with the area adjacent to the Heritage Arnold site apparently completely worked out by 1918. Mining the No. 2 Seam apparently did not extend within the area of potential impacts to the Heritage Arnold site, according to maps in Morrison Knudsen, 1985, as well as review of the Washington DNR mine map index (Schasse et al., 1994). Most of the mining in the No. 3 Seam occurred from about 1874 through about the early 1920s, including the area below the site. The Renton Mine was operated during this period by a variety of operators, most notable the Seattle Electric Company. Typical mining practice in the Renton Mine was to advance principal haulage tunnels (referred to as "levels" or"gangways") laterally from a main haulage slope (inclined shaft) and remove coal by mining on retreat with the breast and pillar system. Bulletin No. 3 indicates that mining had been completed on the 1 st through 7th Levels North by 1912, and was underway on 8th, 9th and 1 Oth Levels North (see Figure 2 for approximate location of tunnels across the Heritage Arnold site). • Y7 • Bennett Corporation J-7179 August 23, 1999 Page 5 It appears that all the No. 3 Seam below the Heritage Arnold property was mined by 1919, the Seattle Electric Co. map no. K31 A shows all the area below the property as being "worked out." This is consistent with the map in Bulletin No. 3 that shows the 9th Level North completed, and the text suggests that 1 Oth Level North was being advanced at the time of the report. By 1920, an 11 th North Level had been driven (see Renton Coal Company, 1920a and 1920b) and a 12th Level North was proposed, which suggests that retreat mining on levels above the 9th Level North (i.e., across the Heritage Arnold property) likely had already been entirely completed. Some mining was accomplished on both the No. 1 and No. 3 seams until the mid-1950s by the Strain Coal Co. (as indicated by Gray, 1955), that probably included mining within workings connected to the mines extending below the Heritage Arnold property. The Strain Co. is one of several local operators that are sometimes referred to as "gypo" miners, typically engaged in salvage mining (pillar robbing) rather than development of new mine reserves. There is no indication that the Strain C-o. or any others mined coal within the area that could influence subsidence at the Heritage Arnold property after the early 1920s;this is significant from the perspective of evaluating risk of future subsidence, as discussed later in this report. REPORTED MINE-RELATED HAZARDS Hart Crowser has worked on abandoned mine problems in Renton and elsewhere in Western Washington since the early 1980s. We understand there are three reports of hazards related to abandoned mine workings on the No. 1 and No. 2 Seams west of the Heritage Arnold site, none on the No. 3 Seam either within or adjacent to the property. For this study, we reviewed other reports of mine hazards in Renton, to see if these involved any conditions similar to those anticipated at the site. Known problems related to abandoned mines in the area include reported subsidence within Renton Ave. north of South 7th Street, collapse of an air shaft at the Noorani residence (706 Renton Ave.), and subsidence and subsequent mine gas emissions at the Thompson residence (1307 South 9th Street). ► No information is available regarding the Renton Avenue subsidence,which was reported by Morrison Knudsen (1985). ► The Noorani subsidence apparently involved collapse of an improperly closed air shaft which extended 165 feet in depth to the Denny Renton Mine workings on the No. 1 Seam. OSM • reclosed the shaft in 1982, and no further problems have been reported. Ar7 ALr • Bennett Corporation J-7179 August 23, 1999 Page 6 ► OSM provided structural repairs to limit subsidence damage to the Thompson residence in 1986 and has been monitoring the presence of carbon dioxide and other gases in the residence since 1997 (Hart Crowser has acted as a consultant to OSM in both of these instances). Other reported mine hazards were found to differ significantly from conditions anticipated at the Heritage Arnold property, e.g., see Morrison Knudsen (1985). Problems at the Thompson residence are potentially the most troubling of the events outlined above and reported elsewhere in Renton, but are not considered particularly likely to occur at the Heritage Arnold property. The Thompson residence is located about 50 feet over the No. 1 Seam and about 130 feet over the No. 2 Seam; considerably less than the depth that these seams occur across the Heritage Arnold Site (about 250 to 300 feet for the No. 1 Seam and about 375 to 605 feet for the No. 2 Seam), see Figure 3. While extent of mining and the source of problems at the Thompson site (i.e., Seam No. 1 or No. 2) are not well understood, there is ample evidence from other sites that the frequency and severity of abandoned mine hazards decreases with depth of the • workings. Given the extensive areas of Renton which are underlain by relatively shallow workings and not experiencing problems of the type found at the Thompson site, there is no reason to expect such problems at the Heritage Arnold property. EVALUATION OF POTENTIAL SUBSIDENCE Analyses of maximum potential subsidence and associated ground strain were accomplished for the site using an empirical method which predicts ground movements which might appear as relatively uniform trough-type settlements over a relatively large area(on a scale corresponding to the extent of mining). Potential for sinkhole development (sudden discontinuous ground surface settlement over a relatively limited area on the order of a few feet to a few hundred square feet)was also assessed based on depth and age of the mine workings. Published statistical evaluations of subsidence at other sites, as well as experience with more detailed rock mechanics investigations at other King County sites, suggest that mine subsidence at the Heritage Arnold property has probably already occurred. ► Published reports by others show trough-type subsidence typically occurs within 40 years or so • after mining, with 90 percent of subsidence events occurring within 70 to 80 years after mining. • Bennett Corporation j-7179 August 23, 1999 Page 7 ► Published reports by others show sinkhole formation typically occurs within 40 to 60 years or so after mining, with 90 percent of subsidence events occurring within 90 years after mining. Since no borings and rock property tests have been completed at the project location, we used a method of estimating the maximum potentia/settlement and ground strain that could occur, based on the depth, lateral extent, dip, and thickness of the mined-out coal. Information was obtained from maps of mine workings for the No. 1 and No. 3 Seams. Hart Crowser's analysis used an empirical method developed by the British National Coal Board (NCB). Based on similarities in mining techniques used for mines in the British study compared to mining in Western Washington, and studies by others, the approach is believed to be conservative and probably over-predicts magnitude of potential settlements and ground strains.The method is limited in the present application in that it cannot distinguish future ground movement from subsidence which has already occurred. • Figure 4 shows a cross section of the subsidence components predicted by the NCB method. A notable aspect of Figure 4 is that the subsidence trough, including particularly the area where tensile ground strains can occur, extends considerably beyond the vertically projected limits of mining, especially on the down dip side. For the Heritage Arnold site, this results in potential ground movements in the western part of the property related to the No. 1 Seam workings which largely extend off-site to the west Our analysis considered a worst case of superimposing settlements from both seams at once, although there is no reason this would necessarily occur in the real world. Hart Crowser's analysis provided the results discussed below and illustrated on Figure 5 assuming that subsidence affecting the Heritage Arnold site has not already occurred (as noted above, statistical reports from other areas suggests these effects have probably already occurred). Since Renton does not have explicit requirements for threshold ground movements, the following discussion relates to differential subsidence and ground strain values exceeding 0.003,which are accepted as threshold levels requiring special construction by King County and the City of Bellevue. The analysis refers to differential settlement and strain, since structures are usually quite tolerant of high values of total settlement magnitude, but readily damaged by small levels of differential settlement and horizontal strain. • iT0 �r • Bennett Corporation J-7179 August 23, 1999 Page 8 As a first case, we estimated ground movements assuming complete mining of both the No. 1 and No. 3 Seams, based on information presented on the maps designated K30 A and K31 A. However, the Morrison Knudsen report indicates that total reported mine production was not as great as implied by complete extraction within the levels worked, and Bulletin No. 3 describes a method of mining in the Renton Mine that is discontinuous. Therefore, as a second approximation, Hart Crowser also calculated ground movements for discontinuous mining of Seam No. 3 (roughly a 50 percent extraction ratio) which would produce greater subsidence impacts. Although predicted levels of total settlement are relatively large, no differential settlement or ground strain values exceeding thresholds values were found for analysis of complete mining of the No. 3 Seam. Since the No. 1 Seam workings are generally located west of the site or along the extreme western edge, and the No. 1 Seam is quite thick, there are differential settlement and ground strain values above threshold values within the Heritage Arnold property for both the cases of complete and discontinuous mining of the No. 1 Seam. ► Maximum trough-type settlements related to the No. 1 Seam could exceed threshold levels • (0.003) for ground strain, within an area about 200 feet wide across the middle of the site and in the extreme western corner, see Figures 2 and 5. Subsidence for the No. 3 Seam alone would not exceed the threshold values for ground strain, except in the extreme west corner of the property. ► Maximum differential settlement related to trough-type settlements could exceed threshold values for discontinuous mining of Seam No. 3 in the western part of the site, and for the superimposed effects of discontinuous mining on Seam No. 3 and Seam No. 1,'in the central part of the site. As noted above, actual future differential settlements and ground strains at the site are anticipated to be some fraction of these values, but actual values of future ground movement, if any, cannot be quantified from available information. GENERAL RECOMMENDATIONS FOR SITE DEVELOPMENT The assessment of potential mine hazards accomplished as discussed above did not identify any specific reason not to develop the Heritage Arnold site using relatively conventional construction methods. • �r • Bennett Corporation J-7179 August 23, 1999 Page 9 From our experience studying mine gas problems at the Thompson site, it is apparent that the problems at that site could have been avoided had original construction used conventional vapor barriers and a well-ventilated crawl space.We recommend new construction over abandoned mines typically include such measures. Listed below are general measures reportedly used to mitigate differential subsidence and ground strain problems in areas of trough subsidence. Without knowing details of proposed construction at the Heritage Arnold site, Hart Crowser provides these measures as ideas you may wish to consider and incorporate where feasible in planning construction, particularly within the western part of the site. ► Smaller structures are typically less sensitive to differential settlement compared to large structures: Minimize continuous length of buildings to reduce potential for horizontal strain or differential settlement to produce damaging or aesthetically displeasing cracks or gaps. ► Divide a single large structure into smaller modules, connected by breezeways which can • tolerate and/or mask differential movement across the complex as a whole. ► Increase foundation-bearing areas and increase reinforcement in footings to improve stability if non-uniform ground support develops. ► Avoid relatively rigid structural frames and cladding, such as concrete or masonry, in favor of relatively flexible structural elements such as timber or steel. ► Use continuous foundations with post and beam construction to the extent possible. Detail vertical support connections to allow for jacking and shimming if necessary due to long- term settlements. Detail lateral connections to minimize distress and prevent separation of members in the event of racking or translation. ► Select and maintain exterior seals and weather-stripping that can tolerate differential movement of overlapping building elements. ► Select interior floor and wall coverings that maximize tolerance of movement and minimize visual signs of distress (i.e., carpet vs. the floors, paneling vs. gypsum wall board). Minimize use of large unbroken, exposed surfaces in favor of smaller or"textured" surfaces that will tolerate tilting or differential movement with less apparent signs of distress. • WN ALA • Bennett Corporation J-7179 August 23, 1999 Page 10 ► Align gravity flow pipelines and increase slopes to reduce potential for unacceptable flow reduction as settlements occur. ► Plan on regular maintenance to verify performance of weather stripping and integrity of . mechanical or utility systems, where performance may be degraded by building movements. There is some potential that surface evidence of past subsidence and/or abandoned mine shafts may be encountered during site development. We recommend that you contact us in the event this occurs, so that we may assist in hazard assessment and provide recommendations for closure or other mitigation as needed. LIMITATIONS Hart Crowser, Inc. completed this work in general accordance with our proposal dated July 13, • 1999.We performed this work for the exclusive use of the Bennett Corporation for specific application to this project and site. Hart Crowser performed this work in general accordance with generally accepted geotechnical engineering practices in the same or similar localities, related to the nature of the work accomplished, at the time the services were performed. We make no other warranty, express or implied. • Ar/ Bennett Corporation 1-7179 August 23, 1999 Page 11 We appreciate the opportunity to assist you with this project. Please call if you have any questions. Sincerely, HART CROWSER, INC. J. Q9 y �0 �8 22484 �ssjONA EXPIRES /z /3/ 1 • MICHAEL BAILEY, P.E. Principal Engineer 7179\H eritage(Itr).doc Attachments: References Figure 1 -Vicinity Map Figure 2 -Site Plan with Principal Mine Tunnels Figure 3 - Diagrammatic Mine Workings Cross Section A-A' Figure 4-Subsidence Analysis Components Figure 5 -Calculated Strain and Subsidence Along Profile AA' cc: Geotech Consultants, attn. Mr. Mark McGinnis • • REFERENCES Denny Renton Clay and Coal Co., 1911. Map of Renton Mine. Map no. K30 A. in Washington DNR mine map collection. Denny Renton Clay and Coal Co., 1918. Map of Renton Mine. Map no. K30 B. in Washington DNR mine map collection. Evans, G. W., 1912. The Coal Fields of King County. Washington Geological Survey, Bulletin No. 3. Gray, Dave, 1955. Map of Renton Mine (Strain Coal Co.workings). Map no. K32 E. in Washington DNR mine map collection. Morrison Knudsen, 1985. Engineering Investigation for the Renton, Washington Area. Report prepared for the Office of Surface Mining, AML Program. National Coal Board, 1975. Subsidence Engineer's Handbook. • Renton Coal Co., 1920a. Map of Renton Mine. Map no. K32 A. in Washington DNR mine map collection. Renton Coal Co., 1920b. Map of Renton Mine. Map no. K32 B. in Washington DNR mine map collection. Renton Coal Co., 1932. Map of Renton Mine. Map no. K32 D. in Washington DNR mine map collection. Renton Historical Society, 1982. Copy of mine workings from Evans, G.W., 1920 (Map no. K32 A. in Washington DNR mine map collection) superimposed on a City street map. Schasse, H.W, et al., 1994. The Washington State Coal Mine Map Collection: A Catalog, Index, and User's Guide. Washington Division of Geology& Earth Resources, Open File Report 94-7. Seattle Electric Co., 1919. Map of Renton Mine. Map no. K31 A. in Washington DNR mine map collection. 7179\H eritage(Itr).doc • Hart Crowser J-7179 0 0 0 7179WAMP7179(COREL) A71 R,';, AV i. 77� oc- 290 75 Av�g 10 s All A 13 a.h. : '41,, . . , .g . , St .;Nv 'r�Xkk gC V� f3 113M q V-00 Rotirdju 'A -AX SE 11371 Po 11UH P3 �V SE t:m Pt L - : 0 rl vl ", Eli t ut- 0 I OTH AV SE IN SE 1201H AV. -n Th ul -4 N AY SF (D st 4e: Y.1 co Lac 1!L�LYN A, • • i'WIN FL Z' 41 4B i SE Site Plan with Principal Mine Tunnels c Approximate Area where Calculated Potential Differential Settlement Exceeds 0.003 (see text) c0)/c c 0 ^mac^mac 0 0 0 F �� .w A c c O O Ifir t + - � [� jh Y' _ s � I .0 0 S? - r t Approximate Area where Calculated ^ Z Z Potential Ground Strain Exceeds 0.003 _ and Differential Settlement Exceeds 0.003 > (see text) -i ) CO ti I 0 '/z 1 �A� Cross Section Location and Designation Scale in Kilometers Location of Reported Workings No. 1 Seam 1":--200' A o — Location of Reported Mine Gangway No. 3 Seam �r • -105— Elevation Contours in Meters HA. R T 0 W WWA J-7179 8199 Note: Base map prepared from USGS quadrangle map of Renton,Washington. Figure 2 Subsidence Analysis Components Surface Limits of Subsidence Tensile Strain Zone Compressive .f_. - Tensile Strain Zone T Strain Zone Original Ground Surface Maximum Subsidence \` Differential Subsidence Up-Dip 2 I I / Limit Angle � I I • i \� Down-Dip �\ I � � ' Angle of Dipping Limit Angle L Coal Seam 00 Mined Portion of Coal Seam Coal Seam Not to Scale AM HARTOWWWR J-7179 8199 71791SUBSlDENCE(CDREI) Figure 4 Calculated Strain and Subsidence along Cross Section A-A' • Strain along Cross Section -500 -400 -300 -200 -100 0 100 200 300 400 500 0.006 , _ 0.004 , 0.002 ' , Strain Profile for Discontinuous Mining Seam No.3 Only j 0 i r rr `Q -0.002 r � r , r , rr - Strain Profile for -0.004 '' Superimposed Effects of�� Property on Cross Section A-A' r Seam No. 1 and Seam No. 3 (Discontinuous) , r -0.006 v Subsidence along Cross Section 500 400 300 200 100 0 100 200 300 400 500 x- l-Property on Cross Section A-A' 0.5 Subsidence Profile for Discontinuous Mining ----- Seam No.3 Only _ --- 1.0 I � _ i 1.5 • _ Subsidence Profile for 2.0 Superimposed Effects of t Seam No. 1 and Seam No. 3 -0-� t (Discontinuous) 2.5 • t/ HARTOWWS J-7179 8/99 Figure 5 71791GRAPHS (COREL) Diagrammatic Mine Workings Cross Section A-A' A A, 400 R FL • -600 -500 -400 -300 -100 0 100 200 300 400 7500 600 Existing Ground Surface 300 -- 2 CO Limit of Denny-Renton Mine Plane No. 1 Workings Gangway to No. 1 Plane Denny-Renton Mine(1 0-Foot-Wide Tunnel) Gangway to No.2 Plane Denny-Renton Mine 100 - (1 0-Foot-Wide Tunnel) Seam No, y m - - tLL O m 4th North Gangway w 5th North Gangway Seam No.2 -100 6th North Gangway 7th North Gangway -200 Seam No 3 8th North Gangway -300 9th North Gangway -400 -- --— ----- - ------- ----- -- -- t! OVVSEA Reported Mine Workings 0 100 200 t Unmined Coal Seam Inferred from Mine Map Scale in Fee J-7179 8199 7179�wws-mcbon(cw/) 5th Figure 3 Gangway Location per Mine Map 9 0 7.0 OTHER PERMITS Several specialized permits/approvals p p approvals will be required for this project. Below is a list of the anticipated permits this office will seek as part of this development: 7.1 City of Renton Street Name and Address Approval 7.2 City of Renton Postmaster Approval 7.3 City of Renton Fire Hydrant Location Approval 7.4 Washington State Department of Natural Resources FPA Permit 7.5 Washington State Department of Ecology NPDES Permit Approval 7.6 City of Seattle Water Department Approval to work within Beacon Way S.E. • 7797.006 RJAJss/ca � J ] • • 7.1 CITY OF RENTON STREET NAME AND ADDRESS APPROVAL «mot: �, a =I, �• PPP—SS—TTTT K,a �"' "' a► CITY OF HORIZONTAL CONTROL PLAN RENTON Planning/Bulld(ng/Public Works Dept. N0. REVISION BY DATE APPR '•""0t0i0."" HERBAGE PUT '- NN N O � � � � � � � � ������� �Yi�4IJi�o i001�V a U,+4N�Om0•V PG�4N-�s •( � a � tl.{tlr 1 II 1 1 1 0 ZmZm `Y II tl phi�o p� N.'� J�j 1 �9l �i a �•i yys�'j$� V q t�rt� O•m +GG y�V G�P°eG EGG T W N 9tat t t t trlwls�lmuka������� I Gt pV fly fAGN GG GOVGQi.!•Ut gs9snesuu I � I CCC aa-a--2-2 a 6 Vsi�li:�ii`.f m T UR Q �mj �G• sO � No>�r. 8m ?f t . itP � tt - ��Mc t SBo�*, m ''P r k 88 I. � at $8m I• ♦msWm4P E LtONE., AVE.SOUTH �QQqt N0= m G +1 OL it N Of< In 3 00 41 C i I SIM ♦ Y I 2C 21• O 0 'Jam+ �/ / p'•, e•�o/ �� Z AftLit 1,0 `��, ` to�`!•',►.' PARK m (7`�/ / 7 • =, a cA yP�wa .� iii� j gx ............... I,...s..a.. mx / ..... I . rq �I ......... 2 ...... 8 4+ co �' I' .: '... rn a a 1 : at m 'I ............... 21' 21' FI o � . . N g ell a ::.......... o Il Y g. I V 95 SFt ± ......... f ............. Ni t/I t�_� 1I I 3G.3• `'�.. ..1 _ :J �,.1... `^' 11 '/ 9 W ................ •I Li ISO �rfI et,Mc./ NA� 20•JOIM USE J� $ $ "1 $ 8 _. _—— •11 7 \ $ US Mb dos Z 60- m Y O t- 6 M �J n z r u, c5 f j 'M G) -D p � r�ni 4 Glle:P:\SOSKPRQI\7797\englneenng\7797-h1.dw9 Ntl/Ti e:01/03/2002 12:16 Sc.[,. 1-50 a Nle°n%rNs: :7797-,,:7797-tr•x7797-t, B.C.E.JOB NO. _7�Z�7 STtOMT N�kN�sN r d•�t •p•o•x. t i 7.2 CITY OF RENTON POSTMASTER APPROVAL • 7.3 CITY OF RENTON FIRE HYDRANT LOCATION APPROVAL • • 7.4 WASHINGTON STATE DEPARTMENT OF NATURAL RESOURCES FPA PERMIT • • 7.5 WASHINGTON STATE DEPARTMENT j OF ECOLOGY NPDES PERMIT APPROVAL 7.6 CITY OF SEATTLE WATER DEPARTMENT APPROVAL TO WORK WITHIN BEACON WAY S.E. 0 8.0 ESC ANALYSIS AND DESIGN • 8.0 ESC ANALYSIS AND DESIGN The erosion control plans for Heritage Hill Renton plat were prepared in accordance with the 1998 KCSWDM, Appendix D. The first phase of construction is to remove the garbage fill located in the northwest portion of the site. There is approximately 10,000 cubic yards of fill material. This will be run through an on-site screen and approximately 50 percent will be soil to remain on site and the other 50 percent will be concrete rubble, construction debris, and household garbage hauled off site to an approved dump site location. The next phase of construction will be to clear the trees on the plat. The site will use the permanent wet pond for sediment control. Drainage will be conveyed through V-ditches with rock check dams and 12-inch culverts at roadway crossings. A temporary infiltration pond will be built in the area of Lots 40,41, and 50,where the natural topography is low after the roadway fills are constructed. This will help infiltrate stormwater on site during construction. It is necessary to protect the permanent infiltration pond in Tract A from being contaminated with siltation during construction. The drainage pond plan calls for leaving the pond bottom higher than the permanent bottom elevation through several stages of plat development,finally being excavated to the permanent pond bottom elevation after all of the houses are constructed and the plat is completely stabilized. The plat must prevent silt-laden stormwater from leaving the site. This should not be a problem given the native gravelly sand soils that exist on site. After clearing and removal of stumps and debris, the top soil layer will be stripped and stockpiled on site. The roads and lots will be graded to subgrade elevations, then the topsoil strippings will be spread over the top of the lots approximately 12 inches thick so that the lot pad elevations specified on the construction plans are achieved. Bright orange silt fence will be utilized along the property line for sedimentation control,as well as perimeter protection. 7797.006[RJA/jss/ca] • • 0 • 0 b Print N/%p Page Page 1 of 1 King County M Parcel Map and Data Tt H_ T 3UUC+ 0 73'+Jr i4 '+e4Q T dfit 3 7 32947 71 $E:B,fXt 323 Sx t lu 1 k7� a o3 sx rr0 / 3 947004W 3 �5751" +t' a5JQ x�at 3 57r' 24i d5f Z3 �5 2 C?l 'MA42 1 101 �� aS' z lu 941003 f r s_a:r. ' 32 71, E 3 947ODY" 24 x = 3 700A, 2423050152 3 tY> � S77f3 ' Parcel Number 0323059312 Address 4810 NE 20TH PL Zipcode Taxpayer BUTCHER RICHARD The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice.King County makes no representations or warranties,express or implied,as to accuracy,completeness, timeliness,or rights to the use of such information.King County shall not be liable for any general,special,indirect,incidental,or consequential damages including,but not limited to,lost revenues or lost profits resulting from the use or misuse of the information contained on this map.Any sale of this map or information on this map is prohibited except by written permission of King County." King County I GIS Center I News I Services I Comments I Search By visiting this and other King County web pages, you expressly agree to be bound by terms and conditions of the site. The details. http://www5.metrokc.gov/parcelviewer/Print—Process.asp 04/05/2005 Map Output � � �, � Page 1 of 1 King County -M. Map Print Page 0371 �, 0475 7 179 00G0 0 0335 480 S_BT}i=ST 90t5 110 ig0485 1 . 9628 0302 1 i3O t y. 00a;(S 0165 0301 E11�; 01 =— OOTO 1 15 0405 013a 0330 0342 0470 t 9058 0331 0344 0471MM _ 0184 0). 0351 0460 1 0181 0211 0321 . 0350 Wi 4 \ 9110 '-. 031 1 DA52 0173 I 0220 0310 ' 0360 0450 l 0162 i 2 7 r 0160<1 70 WJ tiZ 41 t. = t1- 3 9TN 7 ai rrel 7 SE�_ 01 0245 02W 0430 TqJ 9059 0240 0= 04M 0 00o0 02W MI 0420 0140 2 0295 0390 0421 0 0260 0270 0392 0415 9152 �C 0191 0265 0215 0400 11 �y 3 HST 04t0 /y 9001 01 9050 0 9002 2DU KIHG Cau NTY+ Legend Streets - A•10-Agriaikr*am 0U per 10 acres ■ R.18-Resicla**18 DU par acre ! Forest Production Dist rlct ® A•35-Agriafkrd,am DU per 35 arras . R-24-RamdanW 24 DU per acme Boundary ■ F•Faetl ■ R•48-Rmaieniai.48 DU per acp f f Agricultural Production Distract u-►i- N8•Neofft d Brernees Boundary RA-2.5-Rurd Area,am DU per 5 saes ■ Ce•cammue*8emrnes Urban Gmv&Area Line RA-5•Rural Ares,am DU per 5 sores ■ RD-ReparW era►n=& ■ RA.10•Rvar Arm•am Du per 10 awns ■ 0•aim U Lakes and Large Fivers UR•Urtmn Rnserye,are DU per 5 saes I-iMusriel Muddeshoot Tfibe R.1•Reeiderid•am OV par sae ■ afar Parcel R4•Reeidanfal,4 DU par ace Incorporated Area R. .RaN ds",8 0U per sae Zoning LaWs R•8-Remderiel,8 Du per sae Zoning R.12-Rab*Aal,12 DU per acre F'i icrmrl Isar►► The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties,express or implied,as to accuracy,completeness,timeliness,or rights to the use of such information.King County shall not be liable for any general,special,indirect,incidental,or consequential damages including,but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map.Any sale of this map or information on his map is prohibited except by written permission of King County. King CountyI GIS Center I News I Services I Comments I Search By visiting this and other King County web pages,you expressly agree to be bound by terms and conditions of the site._The details.. http://www5.metrokc.gov/servlet/com.esri.esrimap.Esrimap?ServiceName=overview&Cli,... 12/12/2002 6 � -S20 / 23tl /PS727-7 C/ZQx 41Ve2 46-,67 6 ve ?�o>I/ r/ 7 to d LGt z�ac Lo'� PLO �7`lam ✓d 4`l-eW