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HomeMy WebLinkAboutTIR-3906TTCIHINICAL INFORMATION REPORT Tel" Renton, Washington Revised: June 2016 February 2016 Prepared for: Pool Brothers Construction 720 N. 10t' Street #A105 Renton, WA 98057 Prepared by: Daniel Smith, P.E., Project Manager Approved By: Craig Deaver, Principal REPORT #1.4038 PA 1403 8.0\Reports\Storm\Monterra.'I"IR.doc TABLE OF CONTENTS PAGE 1.0 Project Overview...............................................................................................................................1 2.0 Conditions and Requirements Summary.........................................................................................19 2.1 Analysis of The Eight Core Requirements.................................................................................. 19 2.2 Analysis of Special Requirements...............................................................................................21 3.0 Off -Site Analysis.............................................................................................................................24 3.1 Study Area Definition And Maps................................................................................................24 3.2 Resource Review.........................................................................................................................24 3.3 Field Inspection...........................................................................................................................25 3.4 Drainage System Description and Problem Descriptions...........................................................25 3.5 Mitigation Of Existing or Potential Problems.............................................................................26 4.0 Stormwater Analysis and Design....................................................................................................35 4.1 Existing Site Hydrology..............................................................................................................35 4.2 Developed Site Hydrology..........................................................................................................35 4.3 Performance Standards................................................................................................................36 4.4 Flow Control System...................................................................................................................37 4.5 Water Quality System.................................................................................................................38 5.0 Conveyance System Analysis and Design......................................................................................45 6.0 Special Reports and Studies............................................................................................................48 7.0 Other Permits..................................................................................................................................81 8.0 Esc Analysis and Design.................................................................................................................82 9.0 Bond Quantities...............................................................................................................................83 10.0 Operations and Maintenance Manual.............................................................................................93 LIST OF FIGURES Figure 1.1 - Technical Information Report (TIR) Worksheet................................................................. 2 Figure1.2 - Vicinity Map........................................................................................................................ 8 Figure 1.3 - Drainage Basin Maps........................................................................................................... 10 Figure 1.4 - Soil Map and Descriptions................................................................................................... 13 Figure3.1 - FEMA Map.......................................................................................................................... 27 Figure 3.2 - Sensitive Ares Map.............................................................................................................. 29 Figure 3.3 - Offsite Analysis Drainage System Table............................................................................. 31 Figure 3.4 - Drainage Analysis Maps...................................................................................................... 33 Figure4.1 - KRCTS Outputs................................................................................................................... 39 Figure5.1 - LDD Computer Output........................................................................................................ 46 Figure 6.1 - Geotechnical Engineer's Report.......................................................................................... 49 P:\14038.0\Reports\Storm\Monterra.TIR.doe 1.0 PRO.JECT OVERVIEW The Monterra project consist of a single 12,819sq.ft. (0.29-acres) parcel (431 l 990-OO51) located at 905 Sunset Blvd. NE in the City of Renton, King County, Washington. The project also lies within a portion of the SW '/4 of the NE '/4 of Section 8, Township 23 North, Range 5 East W.M. Refer to Figure 2— Vicinity Map within this section. The site is generally rectangular in shape, and contains an existing drive aisle within an easement along its northern property line. The remainder of the site is covered with dense vegetation, and slopes from the east to the west at an approximate gradient of 10%. An existing house use to be onsite, but it was removed after 2005. The property is surrounded by multifamily developments to the north, south and west. To the east the property abuts Sunset Blvd. NE of which a single family residence is located across the street. Site soils consist of Ragnar-Indianola association, sloping (RdC). These soils are classified as type A soils by the Department of Ecology. Earth Solutions NW has prepared a geotechnical engineer's report dated June 27, 2016. They discovered fine sands at the northeast corner of the site which are more favorable soils for limited infiltration. They recommend the trench be designed per Section C.2.3.3 of Appendix C of the 2009 King County Surface Water Design Manual (Manual) which size trenches based off of soil textural classifications. The Monterra project proposes the construction of five attached townhomes, driveways, walkways, frontage improvements, and associated utilities. The site improvements are designed per the City's standards and it's amendments to the Manual. The project site is located in the Peak Rate Flow Control Standard area, requires a Full Drainage Review, and it implements Small Site BMPs for stormwater flow control —more specifically limited infiltration. The project meets Exemption #1 for runoff treatment. A TIR work sheet has been included in Figure l of this section. Page I 1 PAI 403 8.0\Reports\Storm\Monterra.TIR.doe Figure I.I. — Technical Information Report (TIR) Worksheet Page 12 P A 1403 8.0\Reports\Storm\Monterra.TIR.doc KING COUNTY, VYA8H|NUTON,SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT /T|R\NK)RKSAEE T Part 1 PROJECT OWNER � AND PROJECT ENGINEER ` Project Owner Pool Broo<hcmConut. Phone Renton, WA 98057 Project Engineer Daniel Smith, PE Company CES NW Inc. ` Part3 TYPEAPPLICATION ```, [� �� LondueoSenicea Subdivieon / Shod8ubd. / UPD 0 Building Samioao [W/F/Commehoo| / SFR [� �� Clearing and Grading [� �� Right -of -Way Use [� �� Other Part 2 PROJECT LOCATION AND��..� DESCRIPTION .^.`. Project Name Monterra DDESPermit # Location Township Range SE Section 8 905Sunset BLVI)��B Site Address PERMITS Part OTHERQ ` ^' �� DFVVHPA [� �� Shoreline Fk �� �� 0 �� [� �� C0E 404 DOE Dam Safety FEK8AF|oodp|ain CO�VVe�|andu Management LJ Structural Rockery/Vault/ �A ESA Soohon7 �� [� �� Other Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review Full / Targeted (��e Type (circle one): Full Modified (�maa)ll (circle): Site Site Date (include revision Date (include revision dates): dates): Date of Final: Date of Final: Part 6 ADJUSTMENT APPROVALS Type (circle one): Complex / Preapplication / Experimental / Blanket Description: (include conditions in TIR Section 2) Not Applicable Date of Approval: 2OO9Surface Water Design Manual 1/9/2009 °� KING COUNTY, WASHINGTON, SURFACE WATER DI -,SIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes No Describe: Start Date: Completion Date: Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan : City of Renton Special District Overlays: Drainage Basin: Cedar River/ Lake Washington Stormwater Requirements: Small Lot BMPs Part 9 ONSITE AND ADJACENT SENSITIVE AREAS ❑ River/Stream ❑ Lake ❑ Wetlands ❑ Closed Depression ❑ Floodplain ❑ Other Part 10 SOILS Soil Type RdC Slopes 10% ❑ Steep Slope Erosion Hazard Landslide Hazard ❑ Coal Mine Hazard ❑ Seismic Hazard ❑ Habitat Protection Lj ❑ High Groundwater Table (within 5 feet) ❑ Sole Source Aquifer ❑ Other ❑ Seeps/Springs ❑ Additional Sheets Attached 2009 Surface Water Design Manual Erosion Potential Low/Moderate 1/9/2009 KING COUNTY, YVASH|NOTON`SURFACE WATER DESIGN MANUAL T�[�AN|�4| |�J��[JK&�T|[l�J��P()�7-[T|�\�Kl���A��T .^_~..~~'.�.~ .~..,.`..~~., REPORT �..`/ ,,~..~.~..^_._. | Part 11 DRAINAGE DESIGN LIMITATIONS ` | � REFERENCE [� �� [� �� SEPA F� = Other [� �� [U ��Addbiona Sheets Attached LIMITATION / SITE CONSTRAINT Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: Project site sheds to the west as a single basin. (name or description) Core Requirements (all 8 apply) Discharge at Natural Location Number of Natural Discharge Locations: I Flow Control Level: 11iii I (incl. facility summary sheet) mall Site BMPs Full Infiltration Conveyance System Spill c6—nFa—i—n—m—e—nTTo—c—a-fe-d—at: NA Erosion and Sediment Control ESC Site Supervisor: TBD Contact Phone: After Hours Phone: Maintenance and Operation Responsibility: (P-rivai-e-)/ Public If Private, Maintengnce Log Required: (—Y—e-s-Y No Financial Guarantees and Provided: Yes)/ No Liability Water Quality Type: Basic Sens. Lake / Enhanced Basicrn Bog (include facility summary sheet) or Exemption No. I Landscape Management Plan: Yes /(No) Special Requirements (as appli able) Area Specific Drainage Type: CDA/SDO/MDP /BP/LMP /Shared Fac. /(None) Requirements Name: Flood plai n/Floodway Delineation Type: Major / Minor / Exemption / E�) 100-year Base Flood Elevation (or range): Flood Protection Facilities Describe: NA Source Control Describe landuse: NA (comm./industrial landuse) Describe any structural controls: NA %O09Surface Water Design Manual 1/9/2009 KING COUNTY, YVA8R|NU78N`SURFACE WATER DESIGN K4ANOAL T�/�AN|�4| INFORMATION REPORT .__'..—_''_..— ~..'.`..~-.. .`._. ~.`. �..,/ .,~~...^~..^_^_. Oil Control High -use Site: Yes /(No Treatment BMP: Maintenance Agreement: Yes /S with whom? Other Drainage Structures Describe: Below ground infiltration trench and upstream sediment control structure. Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION UJI Clearing Limits Stabilize Exposed Surfaces FX1 Cover Measures Remove and Restore Temporary ESC Facilities Perimeter Protection LJ Clean and Remove All Silt and Debris, Ensure Traffic Area Stabilization Operation of Permanent Facilities Sediment Retention LJ Flag Limits of SAO and open space LJ Surface Water Collection preservation areas 0 Dust Control Ll Flow Control Part 14 STORMWATER FACILITY DESCRIPTI NS (Note: Include Facility Su mary and Sketch) Flow Control Type/Description Water Quality Type/Description LJ Regional Facility LJ Shared Facility Flow Control LJ Other LJ Media Filtration Ll Oil Control LJ Spill Control LJ Other Infiltration Trench 2O09Surface Water Design Manual 1/9/2009 �� KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL, w ■ • Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS ❑ Drainage Easement LJ Cast in Place Vault ❑ Covenant ❑ Retaining Wall ❑ Native Growth Protection Covenant ❑ Rockery > 4' High ❑ Tract ❑ Structural on Steep Slope ❑ Other ❑ Other I Part 17 ' SIGNATURE OF PROFESSIONAL ENGINEER I I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into is worksheetgpd tfie attached Technical Information Report. To the best of my knowledge i Frma i pro ' here is accurate. 2009 Surface Water Design Manual 1/9/2009 5 4 Figure 1.2 — Vicinity Map Page 18 P:\14038.0\Reports\Storm\Monterra.TIR.doe .... ma ............ ..... .... . . . V-ICINITY MAP NTS. c Page 110 P A 1403 8.0\Reports\Storm\Monterra.TIR.doc MONTERRA A PORTION OF THE SW 1/4 OF THE NE 1/4 OF SECTION 08, TWN 23N, RNG 05E WILLAMETTE MERIDIAN, KING COUNTY, WASHINGTON APPROX 20041 TO •- 1HIi NEAREST EX CB EXISTING BASIN 1 _ _ FLOW FREQUENCY SUB -BASIN KRCTS LAND USE AREA (AC.) RETURN PERIOD PEAK FLOW \ EXISTING A DRIVE AISLE 0.087 100-YEAR 0.228 CFS ttEXISTING B 1111. GRASS 0,248 25-YEAR 0133 CFS ! \ a I Inch � 10 fast. TOTAL 0.335 10 YEAR 0.114 CFS 5-YEAR 0.064 CFS 2-YEAR 0.054 CFS In I 15.00' WATER EASMENT 24.O0' ACCESS AND UDIA D@S PER AFN 9007111033 - EASMENT PER AFN 9007111033 i I r i (N S89'44'59 L 91_00• — nl BASIN BOUNDARY LINES+► - — ------------_ rly■_ ;iTi Y�.rr■- rr_i■ 1y aim oil r�-------wl�— r■ L I ' 1 _S89.44.59 P 54,00' t / 11L'�.iYtZ{t_illtiT-/1 i , \ ,l i i W / I cr in "01 CID It BASIN BOUNDARY LINE / �--N89'44 59 W 129.46 {- - - -P ---\ /9 ' 1 ZI r h 7 /l/T 11 !ll1 / o l I I /,t!IIIIII!! I, ,'cl'IIII�I i f I II i APPROX. 150-FT TO THE NEAREST EX CB VICINITY MAP N.T.S. 4_:(*4NL EXISTING DESCRIPTION PROPOSED - MONUMENT LANE - PROPERTY LINE --• - RIGHT OF WAY LINE — ----- - -- EASEMENT LINE — ---- - BUILDING SETBACK LINE - - - - -c - CHAIN LINK FENCEo-- -.. WOOD FENCEr�— == CURD -- -- EDGE OF PAVEMENT -- -- -- ,�,o CONTOURS ,0 STREET SIGN — 1 ( STORM DRAIN CATCH BASIN ■ ()} STORM DRAIN MANHOLE > STORM BRAIN CLFANOUT STORM DRAIN LINE SD -HO - ROOF DRAIN LINE — I () SANITARY SEWER MANHOLE SANITARY SEWER CLEANOUT -- SANITARY SEWER LINE S -- ` S SANITARY SEWER STUB -- ---------55 S FIRE HYDRANT Y :K WATER VALVE N WATER METER N . yy _...._ WATER MAIN W j-< \5 LUMINAIRE ---Q -�>- POWER/UTILITY POLE ---- GUY WARE ASPHALT CONCRETE ASPHALT OVERLAY CEMENT CONCRETE SAWCUT LINE -------------------- ROCK WALL C■CAK:-:� CLEARING LIMITS iYYYYI INTERCEPTOR DITCH • — SILT FENCE M 3E CHECK DAM CALL 48 HOURS BEFORE YOU DIG DIAL 811 --__ .....--_.-_. � � 1 1 Pu ai zi9a 1q0 MONTERRA A PORTION OF THE SW 1/4 OF THE NE 1/4 OF SECTION 08, TWN 23N, RNG 05E WILLAMETTE MERIDIAN, KING COUNTY, WASHINGTON POST DEVELOPED BASIN BOUNDARY LINE 24,00'ACCESS AND UTIUD S APPROX. 200-I1 TO 1ME NEAREST F.X C0 PJS1/A/A_ 3 i „ ' a 1 \ l / n lI i\ l PROPOSED SIDEWALK DIRECTED TOWARDS A SEPARATE THRESHOLD DISCHARGE AREA APPROX. 150-FT TO THE NEAREST EX CB VICINITY MAP N.T.S. 4 141E, EXISTING DESCRIPTION PROPOSED - - MONUMENT LINE -- --- -- - - PROPERTY LINE --- — — - - RIGHT OF WAY LINE — - - --- — EASEMENT LINE — — — — — — — BUILDING SETBACK UNE -- -0 o - CHAIN LINK FENCE --e o-- o- - WOOD FENCE --_ -_= CURB -- --- --- EDGE OF PAVEMENT — ... .._ _.._. --- -- ` CONTOURS r. STREET SIGN i STORM DRAIN CATCH BASIN ■ (17 STORM DRAIN MANHOLE > STORM DRAIN CLEANOUT D -- STORM DRAIN LINE `^ --RD - ROOF DRAIN LINE --R0 (� SANITARY SEWER MANHOLE SANITARY SEWER CLEANOUT - S ---- SANITARY SEWER LINE $ -- -SS SANITARY SEWER STUB — ------SS 0 FIRE HYDRANT Y k WATER VALVE H ,tJ WATER METER 9 ---- --- - W _.__. WATER MAIN WA --6 LUMINAIRE > POWER/UTILITY POLE --- GUY WARE ASPHALT CONCRETE ASPHALT OVERLAY CEMENT CONCRETE SAWCUT LINE ------------------- ROCK WALL CLEARING LIMITS /YWY1 INTERCEPTOR DITCH — SILT FENCE * M CHECK DAM Q CALL 48 HOURS BEFORE YOU DIG DIAL 811 1 PNuj 02J 2,iflT6nW0 �., Figure 1.4 — Soils Map and Descriptions Page 113 P AI 403 8.0\Reports\Storm\Monterra.TIR.doc M.'a JT MT M..00 ITT ZZT BT809zs ems s WOWS ONOWS m09zs U) 0 U) 0 U) U �®\ c6 S \ \ o 'o (41, =2 F 0 r rL rL o c) 0 z 0 39zs Al. 1 I z 0 LL Z 1d G a N (O p NC: O O 01 C �p ro O U a) s > O ` N U if.0 N m d1 .0 m 2a N D O N ro o a) o. C E U) a N N C E O N C ro •- O C cn (h — U t/1 O U7 in t-M a) N U m CL E °� a)U w a N � U C Q a c Z cn a N - (v Z m N U o Iwo �O . E L UvW N N O 'roa. 'Q C a 0 m J_- CL M p a) m m ani N U Q p (D ro o Q a > a: o a� �% Tm O m u �� ro o o u m a) E c O maw a) c» ro Z'o_���' Eo c co �c N o .c E T Q ,�E.o N 2' Q N U '67 m O U o O 'y U lv a >+ N O N m ro N ,m n.a`o� 'o a) E a rn� n a E ro ro J fn N Q Co U O C m N _ X a) m N t o o N N C N O `m ^Sa>) CS N m m E O HE N m N m� U cp N a) m Q Q m > o cu `O o ac) >, -U1 a m N C O C a j C >'� «_ C m C = p n «. O 'O C_ O p O 0-0 O N [ Q a m pam� L a O N N m m U a .O tO N U C a N a) U a a) N> U) a) —[ E °) — (0 N a) co O •a o m N E N E d E U) U 2 n.=0 Q 0 IL- � tO U) U) `o 00 .E o a d y T CL C � N Ntm C N C lQ N m N O O � O o s o. 54, m a U)ca p oci R 44 a 0 LL O 6 O C n.. N C E `w °a 0 N E 0 ` O_ a CL N CO (a 8 > Oa OaC O> WO ° t U. F _ uOU)law 3 t Q U) co (f) '0 m m U U (D 0 J J (L wo U) U) N U) U) U) y C a N J 13 OM •6 R. fn Q U) d' M W 'o U) (U o m m o a`) n. n o U C O m Z Soil Map —King County Area, Washington Map Unit Legend King County Area, Washington (WA633) Map Unit Symbol Map Unit Name Acres in AAl percent ofAOI RdC Ragnar-Indianola association, j 0.31 100.0% sloping Totals for Area of Interest tSt)A Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 0.3 j 100.0% 9/18/2014 Page 3 of 3 Map Unit (description: Ragnar-Indianola association, sloping ---King County Area, Washington King County Area, Washington RdC—Ragnar-Indianola association, sloping Map Unit Setting National map unit symbol., 1 hmty Elevation: 300 to 1,000 feet Mean annual precipitation: 30 to 65 inches Mean annual air temperature: 48 to 54 degrees F Frost -free period: 150 to 210 days Farmland classification: Farmland of statewide importance Map Unit Composition Ragnar and similar soils: 45 percent Indianola and similar soils: 40 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Ragnar Setting Landform: Eskers, kames, terraces Parent material: Glacial outwash Typical profile H1 - 0 to 4 inches: ashy fine sandy loam H2 - 4 to 27 inches: ashy fine sandy loam H3 - 27 to 60 inches: loamy sand Properties and qualities Slope: 2 to 15 percent Depth to restrictive feature: 20 to 40 inches to strongly contrasting textural stratification Natural drainage class: Well drained Capacity of the most limiting layerto transmit water (Ksat): High(1.98 to 5.95 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available waterstorage in profile: Low (about 3.7 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 3e Hydrologic Soil Group: A Other vegetative classification: Unnamed (G002XN402WA) Description of Indianola Setting Landform: Terraces Parent material: Glacial drift UStxr Natural Resources Web Soil Survey 9/18/2014 Conservation Service National Cooperative Soil Survey Page 1 of 2 Map Unit Description: Ragnar-Indianola association, sloping ---King County Area, Washington Typical profile H1 - 0 to 6 inches: loamy fine sand H2 - 6 to 30 inches: loamy fine sand H3 - 30 to 60 inches: sand Properties and qualities Slope: 2 to 15 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Somewhat excessively drained Capacity of the most limiting layer to transmit water (Ksat): High(1.98 to 5.95 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of pending: None Available waterstorage in profile: Low (about 5.0 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 3e Hydrologic Soil Group: A Other vegetative classification: Unnamed (G002XN402WA) Data Source Information Soil Survey Area: King County Area, Washington Survey Area Data: Version 8, Dec 10, 2013 USDA Natural Resources Web Soil Survey 9/18/2014 Conservation Service National Cooperative Soil Survey Page 2 of 2 2.0 CONDITIONS AND REQUIREMENTS SUMMARY The project is subject to Full Drainage Review as dictated by the Manual's Core Requirements No. I through 8, and Special Requirements No. 1 through 5. 2.1 Analysis of the Eight Core Requirements Core Requirement No. 1: Discharge at the Natural Location Intent: To prevent adverse impacts to downstream properties caused by diversion of flow from one flowpath to another, and to discharge in a manner that does not significantly impact downhill properties or drainage systems. Diversions can cause greater impacts (from greater runoff volumes) than would otherwise occur from new development discharging runoff at the natural location. Diversions can also impact properties that rely on runoff water to replenish wells and ornamental or fish ponds. Response: The project proposes to control its runoff with the use of Limited Infiltration. Historically, runoff from the site sheet flows west off the site onto the neighboring apartment complex's parking lot. A catch basin in the parking lot collects the runoff and directs it downstream towards the west. Core Requirement No. 2: Off -Site Analysis Intent: To identify and evaluate offsite flooding, erosion, and water quality problems that may be created or aggravated by the proposed project, and to ensure appropriate measures are provided for preventing creation or aggravation of those problems. In addition, this requirement is intended to ensure appropriate provisions are made, as needed, to mitigate other identified impacts associated with the quantity and quality of surface and storm water runoff from the Project site (e.g., impacts to the hydrology of a wetland as may be identified by a "critical area report" per RMC 4-3-050). Response: The project intends to control its runoff with limited infiltration with the use of an infiltration trenches. Runoff from the proposed roofs will be collected onsite and released to the ground water table. The remaining runoff is allowed to discharge downstream. A Level One Downstream Analysis is located within Section 3.0 of this report. Core Requirement No. 3: Flow Control Intent: To ensure the minimum level of control needed to protect downstream properties and resources from increases in peak, duration, and volume of runoff generated by new development. Page119 P:\14038.0\Reports\Storm\Monterra.TIR.doe The level of control varies depending on location and downstream conditions identified under Core Requirement 42, Response: The site is located in the Peak Rate Flow Control Standard area; although, the project does not create 0.10-cfs or greater rise of runoff from the predeveloped site. Also, the site is Tess than 22,000 square feet and is being developed as an individual site; therefore, the project uses Small Lot BMPs as described in Appendix C of the Manual. More specifically limited infiltration (Section C.2.2) is implemented for the project's roof tops. Per Figure 5.2. EA of Appendix C of the manual an individual lot less than 22,000 sq.ft. in which full dispersion and infiltration is not feasible must control at least 20% of its site area with another Small Site BMP. The disturbed landscaped areas will have their soils amended to a depth of at least 8-inches. Core Requirement No. 4: Conveyance SVstem Intent: To ensure proper design and construction of engineered conveyance system elements. Conveyance systems are natural and engineered drainage facilities that collect, contain, and provide for the flow of surface and storm water. This core requirement applies to the engineered elements of conveyance systemsprimarily pipes, culverts, and ditches/channels. Response: Pipe Systems: The proposed conveyance system is comprised of privately owned roof downspout pipes which connect to the proposed infiltration trench. This project doesn't propose a public storm system. The conveyance system is sized to convey tine 100-yeas developed peak flow as determined by KRCTS, and analyzed using LDD's Manning Calculator in Section 5.0 of this report. Culverts: There are no proposed culverts for this development. Ditches/Channels: There are no proposed ditches for this development. Core Requirement No. S: Temporary Erosion and Sediment Control Intent: To prevent the transport of sediment and other impacts, like increased runoff, related to land disturbing activities. Erosion of disturbed areas on construction sites can result in excessive sediment transport to adjacent properties and to surface waters. This sediment call result in major adverse impacts, such as flooding from obstructed drainage ways, smothering of salmonid spawning beds, algal blooms in lakes, and exceedances of state water quality standards for Page 120 P:\14038.0\Reports\Storm\Monterra.TIR.doc turbidity. These impacts can also result from the increased runoff generated by land disturbing activities on construction sites. Response: A "Temporary Erosion and Sedimentation Control (ITESC) Plan has been p7repared as part of the Construction Plans. The TESC Plan will prevent the transport of sediment to streams, wetlands, lakes, drainage systems, and adjacent properties in accordance with all the applicable standards of the KCWSWDM and the City of Renton. Core Requirement No. 6: Maintenance and Operations Intent: To ensure that the maintenance responsibility for drainage facilities is clearly assigned and that these facilities will be properly maintained and operated in perpetuity. Response: The onsite stormwater components will be located within private property. See Section 10.0 for a draft Flow Control BMP Covenant and maintenance standards for the privately maintained drainage components. Core Requirement No. 7. Financial Guarantees and Liability Intent: To ensure financial guarantees are posted to sufficiently cover the cost of correcting, if necessary, incomplete or substandard drainage facility construction work, and to warrant for two years the satisfactory performance and maintenance of those newly Constructed drainage facilities. Core Requirement #7 is also intended to ensure that a liability policy is provided that protects the proponent and the City from any damages relating to the construction or maintenance of required drainage facilities by private parties. Response: Bond Quantities are included in Section 9.0. Core Requirement No. 8: Water Qualit Intent: To require an efficient, cost-effective level of water quality treatment tailored to the sensitivities and resource protection needs of the downstream receiving water to which the project site drains, or, in the case of infiltration, protection of the receiving groundwater system. Response: The project proposes 1,948 sq.ft. of new pollution impervious surfaces (PGIS), of which 1,280 sq.ft. are driveways and the remainder in the access easement, and 5,004 q.ft. of pollution generating pervious surfaces (PGPS). Additionally these areas are not controlled with full dispersion; therefore, the project is exempt from this core requirement per Exemption #1. 2.2 Analysis of Special Requirements Special Requirement No.]: Other Adopted Area -Specific Requirements P:\ 1403 8.0\Reports\Storm\Monterra.TIR.doe Page 121 Response: The following is a list of other possible adopted area -specific requirements according to the Manual: Master Drainage Plan —'The area is not part of a master drainage plan. Basin Plans — This site is located within the Cedar River/Lake Washington drainage basin. No additional requirements have been identified. Salmon Conservation Plan — The site is located within the WRIA 8 Chinook Salmon Conservation Plan Area. No additional requirements apply. Flood Hazard Reduction Plan Updates — This project does not appear to be within a Flood Hazard Area; therefore, this plan does not apply. Shared Facility Drainage Plan — The project does not propose to connect to a shared detention facility system or create a shared facility; therefore, this plan does not apply. Special Requirement No. 2: Flood Hazard Area Delineation Response: The proposed site is not located within the 100-year floodplain or flood hazard area. See included FEMA map within Section 3.0 of this report. Special Requirement No. 3: Flood Protection Facilities Response: Special Requirement No. 3 is not applicable to the proposed site since the site will not affect any existing flood protection facilities. Special Requirement No. 4: Source Control Response: Special Requirement No. 4 only applies to commercial site development permits. Since this site is a multi -family residential, this requirement does not apply. Special Requirement No. S: Oil Control Response: Special Requirement No. 5 does not apply to the site since it is not classified as a high -use site. Page 122 PM 403 8.0\Reports\Storm\Monterra.TIR.doc Special Requirement No. G: AyWLj,r Protection Area Response: The project is not located within either Zone 1 or Zone 2; therefore, this requirenmit does not apply. Page 123 P:\14038.0\Reports\Storm\Monterra.TIR.doe 3.0 OFF -SITE ANALYSIS 3.1 Study Area Definition and Maps The City of Renton requires a summary of the upstream drainage basin, and a 1-mile downstream drainage analysis. The property is located on the west side of Sunset Blvd NE and south of the intersection of Aberdeen Ave. NE. Multi -family developments are located to the north, south and west. To the east are single-family properties across Sunset Blvd NE. Runoff upstream of the project site is collected within Sunset Blvd NE's right-of-way by curb and gutter. Once the runoff is in the gutter it's collected by existing catch basins approximately 150- feet south and 190-feet north of the project site in Sunset Blvd. NE, and Aberdeen Ave NE respectively; therefore, the upstream areas bypass the project site. The project proposes to infiltrate its roof top areas. The reminder of the site is allowed to shed to the west where it is collect by the neighboring apartment's collection system. An Offsite Drainage Analysis Map is included in this section. 3.2 Resource Review • Adopted Basin Plans: This site is located within the Cedar River/Lake Washington drainage basin. According to the City's GIS Map Viewer the site is tributary to Johns Creek, and ultimately Lake Washington. • Floodplain and Floodway FEMA Maps: Per the FEMA Panel 977 of 1725 of map number 53033CO977F the site is located in Zone X and is not located within the 100- year floodplain. Please see the FEMA map within this section. • Offsite Analysis Report: No other offsite analysis reports were located. • Sensitive Areas Folios: Based on a review of the Renton and King County Sensitive Areas Maps, it was found that the subject site does not contain any seismic hazards, flood hazards, is within an aquafer protection zone, or coal mines. However, the project site is located within and adjacent to a high erosion and landslide hazard zones. • United States Department of Agriculture King County Soils Survey: Based on the soils map for this area, the entire site is located within Ragnar-Indianola association, sloping (RdC). Ragnar soils are typically underline by ashy fine sandy loam 0 to 27-inches then to loarny sands to a depth of 60-inches. Indianola soils are Page124 P:\14038.0\Reports\Storm\Monterra.TIR.doc typically underline by loamy fine sands 0 to 30-inches then to sands to a depth of 60- inches. These soils are classified as type A/B and are either well drained to somewhat excessively drained. • Wetlands Inventory Maps: Based on a review of the Renton and King County maps there are no onsite or adjacent offsite wetlands. • Washington State DOE List of Polluted Waters: There are no polluted waters within 1-mile of the project site. • Erosion and Landslide Maps: As previously mention the site is located within and adjacent to a high erosion and landslide hazard area. 3.3 Field Inspection The site was visited on November 25, 2015. It was a sunny day after a prolonged period of high winds and rain. The downstream drainage path was walked and what was discovered is recorded in the Offsite Analysis Drainage System Table which is included with this section for reference. No serious drainage problems were observed; although, a type 2 catch basin at the end of a cross culvert under Interstate 405 has signs of possible surcharging. 3.4 Drainage System Description and Problem Descriptions The project site slopes from east to west at an approximate rate of 10%. What runoff that isn't infiltrated onsite continues westerly overland for 380-feet onto the property to the south (parcel number 3119900050). This property has a closed conveyance system consisting of at least 2 catch basins in its northern drive aisle. From this property the runoff continues west for another 260-feet over a Puget Sound Energy transmission line tract, and into the Interstate 405's ditch system. The runoff continues north within the ditch for approximately 190-feet where it is conveyed under the freeway by a 24-inch corrugated metal culvert pipe. From this culvert the runoff continues into Houser Way N with a Type 2 catch basin. This catch basin possibly surcharging into a short ditch along Houser Way N where it is intercepted by a 12-inch concrete culvert pipe. This structure could be a bubbler, but it could not definitively be determined as such. The ground surrounding it is moist and soft with some stormwater trickling over the top back of the curb and into Houser Way N. Once in the 24-inch concrete culvert the stormwater is conveyed for 1,200-feet to the intersection of N 8°i St. Once the runoff is in N 8"' St the runoff flows west into a 36-inch diameter storm system for another 1,070-feet to the intersection of Garden Ave N. The remainder of the one mile drainage path ends north at the intersection of Garden Ave N and Lk Wash Blvd N. At this intersection the stormwater from the area discharges Page 125 P:\14038.0\Reports\Storm\Monterra.TIR.doc to an open channel via a 72-inch corrugated metal pipe on the north side of Lk Wash 131vc1 N. From here the runoff is conveyed north towards Lake Washington with a series of large diameter concrete culvert pipes. The ultimate discharge location for runoff from the project site is Lake Washington at the Gene Coulon Memorial Beach Park. An Offsite Analysis Drainage System Table is included within this section for reference. 3.5 Mitigation of Existing or Potential Problems There are no existing problems that need mitigation due to the construction of this project. The project proposes to use limited infiltration to control its proposed roof tops, and amended soils for the future landscaped areas. Any potential problems this project could aggravate downstream are mitigated with the use of these Small Site BMPs. Page 126 P:\14038.0\Reports\Storm\Monterra.TIR.doc Figure 3.1 — FEMA Map Page 127 PAI 403 8.0\Reports\Storm\Monterra.TIR.doe Page 129 P: \ 1403 8.0\Reports\Storm\Monterra.TI R. doe mama m t 1 ell 3� :hy is opal I. u ram, Cy 4) ,may Ll. 4) L Al o E a ro r pS ro f O� w G C ro vi QNj . . p o u q a ❑ (D to ? O 41 CLo ma ° o o 0 x .4y � ✓ N ro U O� O O� p p ° a n.. © o r b pa o 3 45 E ++ m' 'o v rn � rn� 0 o a a O o Y L, a. CLL. 0 c: 0 z z c / OL t6 :o C .- ro t:r;N U N U a p C o C x �U! O SN=_ O .T, E � O p o O O7 tui C X o o off- Wa o> z Z t z z o Y rov �o LEIS N Ll 7l .-r o o 0 o a t N z z t N o ro _ Cc:N o GD o o m o E O. c R Cs L E ��-� m m b w in o Qi N p..� a O U u 0 7 v ✓ y ro U: M �. ey � ✓` 7 ry p a >, N 3 2 P� mt-(/) Na?m U v Co=vm C N m .R N (9 N U er o' C ff w Q m o w U U U O o .Q t° - N M d CO) N Figure 3.4 — Downstream Analysis Map Page133 P:\14038.0\Reports\Storm\Monterra.TIR.doe 3q 4.0 STORMWATER ANALYSIS AND DESIGN 4.1 Existing Site Hydrology The existing site is, generally, rectangular in shape, covered with two trees, grass and blackberries. I-listorieally in approximates, a 1,500 sq.ft. single-family home was onsite with lawns, and a 400 sq.ft. driveway. This home was demolished in 2005 and now the site sits vacant. The site slopes from east to west at an approximate rate of 10%. There is an existing paved driveway onsite to access the property to the west. The onsite soils are Ragnar-Indianola association, sloping (RdC) which is classified as an outwash soil. A Pre -Developed Basin Map is included Section I of this report. According to Reference l 1-A of the City's amendments to the Manual the site requires a Peak Rate Flow Control Standard, matching the existing site conditions runoff rate for the full 2, 10, and 100-year peak rates, if detention is used to mitigate its runoff. The pre -developed basin is as follows: Sub-Basinn1�G TS Land Use"':'Acres Existing A Drive Aisle (Imp.) 0.087 Existing B Till Grass 0.248 Total 0.335 Table 4.1.1- Pre -Developed Basin Summary The 15-minutes pre -developed peak flows for the basin (0.335-acre) are as follows (from KCRTS output): Qz= 0.059-cfs Qio= 0.124-cfs Qzs= 0.181-cfs Qioo= 0.312-cfs 4.2 Developed Site Hydrology Limits of site disturbance will include installation of sediment and erosion control Best Management Practices (BMPs), construction of frontage improvements, driveways, walkways, infiltration trenches, utilities, landscaping and 5 townhornes. Frontage improvements include Page135 P:\ 1403 8.0\Reports\Storm\Monterra.TlR.doe curb, gutter, 8-foot planter and 8-foot sidewalk on the western side of Sunset Blvd NE. The total disturbed area will cover approximately 0.28 acres both onsite and off. Upon completion of the project, impervious surfaces covering the site include approximately 0.04-acre of driveways/pathways, and 0.09-acre of new rooftops. The proposed infiltration trenches mitigate the roof top areas only with limited infiltration. The roof top area is tributary to two parallel of infiltration trenches. Since limited infiltration is used when computing the overall basin peak flows they are modeled as 50% impervious and 50% grass per Table 1.2.3.0 of the Manual. The post developed basin is as follows: Su6!AAsxn KRCTS Viand Use Acres Post Dev A Drive Aisle (Imp.) 0.080 Post Dev B Driveways 0.029 Post Dev C Townhouse (50% Imp., 50% Till Grass) 0.087 Post Dev D Walkways (Imp.) 0.014 Post Dev E Yards (Till Grass) 0.098 Total 0.308 Table 4.1.1- Post Developed Basin Summary The 15-minutes post developed peak flows for the basin (0.308-acre) are as follows (from KCRTS output): Qz= 0.089 cfs Qlo= 0.162 cfs Qzs= 0.219 cfs Qloo= 0.338 cfs For basin delineation please refer to the Developed Basin Map in Section 1 of this report. The Post developed basin is smaller than the predeveloped basin since the new sidewalk (597 sq.ft.) and planter (579 sq.ft.) along Sunset are tributary to a separate threshold discharge area. 4.3 Performance Standards The site is located within a Peak Rate Flow Control Standard areas and the project results in a 0.026-cfs increase in runoff when compared to the existing site; therefore, the project is exempt from Core Requirement #3: Flow Control. According to Figure 5.2.1.A for lots less than 22,000 Page136 P:\14038.0\Reports\Storm\Monterra.TIR.doc sq.ft. the site must evaluate full dispersion, full infiltration and if neither of those BMPs are feasible then at least: 20% of the site must be controlled with another Small Site BMP. The site does not have the proper flow paths and soils for cither full dispersion or infiltration, but the onsite soils are sufficient for limited infiltration. The project's roof tops are mitigated with infiltration trenches per Limited Infiltration Section C.2.3 oi'Appendix C of the Manual, which is greater than 20% of the site area (20% of site area = 2,564 sq.ft., roof top area = 3,795 sq.ft.). All disturbed future landscaped areas shall have their soils amended to a minimum depth of 8-inches per the Manual. The remaining impervious surfaces, driveways and walkways, are allowed to sheet flow onto the lawn areas and proceed downstream. 4.4 Flow Control System As previously mentioned, the project is exempt from Core Requirement #3: Flow Control. The roof tops are mitigated with infiltration trenches, the new yard areas are to have their soils amended, and the remaining impervious surfaces (0.029-acres of driveways and 0.014acres of walkway) are not concentrated and are allowed to sheet flow downstream. The infiltration trenches are sized per Section C.2.3 and the geotechnical engineer's report which discovered fine sands; therefore, the trench sizing ratio is 75-feet long by 2-feet minimum wide (150 sq.ft.) per 1,000 sq.ft. of tributary impervious surfaces. The maximum trench length is 100-feet, and each trench center shall be no closer than 6-feet. The trench is sized to infiltrate all the roof top area being constructed. The project proposes 3,795 sq.ft. (0.087 acres) of new roof areas. This area exceeds 20% of the site (12,819 sq.ft. * 20% = 2,564 sq.ft.); therefore, no other BMPs are required per Figure 5.2.1.A of the Manual. Trench sizing calculations are as follows: Rooftop Area: 3,795 sq.ft. Sizing Ratio: 150 sq.ft. trench bottom area per 1,000 sq.ft. of tributary impervious area. Calculation: 150 sq.ft./1,000 sq.ft. * 3,795 sq.ft. = 569 sq.ft. trench bottom area required. Provided: two 48-feet long by 6-feet wide by 2-feet deep infiltration trenches. (2*48-feet*6-feet = 576 sq.ft.); therefore, the provided trench is adequate. Page137 P:\ 1403 8.0\Reports\Storm\Monterra.TIR.doe 4.5 Water Quality System 'rho projectpropomux 1,948 mq.fL of new 96}S (Jhvcvvuyx and new concrete apron along Sunset Blvd.) and 5,004 sq.ft. PGPS (yard areas), 'ne pro.ject does not exceed thresholds for water quality treatment per on#} uadescribed inSection /28ofthe KC8WDM. Pucn|3D P:\14038.0\Reports\Storm\Monterra.TIR.doc Page139 P:\14038.0\Reports\Storm\Monterra.TIR.doe Land UFe SUrnmary X . Area ni Till Forest! 0.00 acres' Till Pasture! 0.00 acres, Till Grass' 0.25 acres; Outwash Forest 0.00 acres Outwash Pasture! 0.00 acres; Outwash Grass! 0.00 acres! Wetland' 0.00 acres: Impervious! 0.09 acres; Total 0.33 acres Scale Factor : 1.00 15-Min Historic File for computed Time Series [.TSF] Modify User Input �._ File for computed Time Series s [.TSF] Page 140 P:\14038.0\Reports\Storm\Moiiterra.TIR.doc Monterra PreDev,pks Flow Frequency Analysis LoePearson III Coefficients Time Series File;monterra predev.tsf Mean= -1.181 StdDev= 0.206 Project LncationzSea-Tac Skew= 1,418 ---Annual Peak Flow Rates--- -----FInw Frequency Analysis------- FlowRate Rank Time of Peak - - Peaks - - Rank Return Pr0b ([FS) /[F5\ Period 0.106 O 2/16/49 17:45 0.357 l 89.50 0^989 8.166 3 3/03/50 15:15 0.190 2 32.13 0,969 0.054 31 2/09/51 12:45 8.166 3 19*58 0,949 8.063 26 10/17/51 7:15 0.158 4 24^08 0,929 e.039 47 9/30/53 3:00 0^158 S I0,99 8,909 0.854 32 12/19/53 17:45 0,126 6 9.01 0.889 0.041 44 11/25/54 1:88 0.112 7 7,64 0,869 0.057 38 1I/18/55 15z80 8,106 O 6.63 0,849 0.076 12 12/89/56 12/45 0,885 9 5.86 0.829 8,064 25 1/16/58 10:15 0.086 18 5.24 8.809 0.067 21 10/18/58 19:45 8.078 11 4.75 0.789 0.078 11 10/10/59 22:00 0.076 12 4,34 0,769 0.069 16 2/14/61 28:15 0.073 13 3.99 0,749 0.049 45 8/84/62 13:15 0.870 14 3.70 0,729 0,052 35 12/01/62 20:15 8.069 15 3,44 0,789 0.037 48 12/31/63 22:00 0.069 16 3.22 0.690 0.068 17 4/28/65 19:30 0.068 27 3.03 0,670 0.048 46 1/85/66 25:80 0,068 18 2,85 0,650 0.073 13 11/13/66 17:45 0.068 19 2.70 8.630 0.158 4 8/24/68 15:00 8.068 20 2.56 0'610 0.064 24 12/03/68 15:30 0.067 21 2.44 0.590 0'036 49 1/13/78 20:45 0.066 22 2.32 0,570 0.045 39 12/06/70 7:00 0'066 23 2.22 0.550 0.112 7 12/08/71 17;15 0.064 24 2,13 0'530 0.044 40 4/18/73 9:30 0,064 25 2.04 0.510 0'068 20 11/28/73 8:15 0.063 26 1,96 0.490 0.066 22 13/26/74 20:15 0.063 27 1.89 0'470 0.048 37 10/29/75 7:00 9.062 28 1,82 0.458 0.036 50 8/26/77 1:08 0.060 29 1.76 0.430 0,068 18 9/23/78 18:15 0'057 30 1.70 0.418 0.086 9 9/08/79 13:45 0.054 31 1.64 0'390 0.086 10 12/14/79 20:00 0,054 32 1.59 0.370 0.060 29 12/25/80 23:15 0.053 33 1.54 0.350 0,190 2 10/05/81 22:15 8.052 34 1.49 0.330 0.062 28 10/28/82 16:00 0'052 35 1,45 0.319 8'053 33 1/02/84 23:45 0.050 36 1'41 0'291 0.042 43 6/06/85 21:15 0'048 37 1.37 0.271 0,066 23 10/27/85 10:45 0.048 38 1'33 0'251 0.068 19 10/25/86 22:45 8.045 39 1,30 0.231 0'048 38 5/13/88 17:38 0'044 40 1'27 0'211 0.044 41 8/21/89 16:00 0.044 41 1,24 0'191 0.126 6 1/89/90 5:30 0,869 15 4/03/91 20:I5 0,050 36 1/27/92 15:25 8.063 27 6/09/93 I2:15 0.043 42 11/17/93 16:45 0.052 34 6/05/95 17:00 0.870 14 5/19/96 11:30 0.357 l 12/29/96 11;45 0,158 5 10/04/97 14:15 Computed Peaks Computed Peaks Computed Peaks Computed Peaks Computed Peaks Computed Peaks Computed Peaks Computed Peaks Monterra PrgDev.pks 0.04] 0.042 8.041 0.040 0.040 0.039 0.037 0.036 0.036 0-312 0.238 0.181 0.124 0.115 0.092 0.059 0,846 42 1,21 0.171 43 1.18 0.151 44 1^15 0.131 45 1.12 0.111 46 I.10 0,091 47 1.08 0.071 48 I.05 0.051 49 1.83 0.031 50 1.01 0.011 100.00 0,990 50.00 0.980 25.00 0.960 10.00 0.000 8.00 0,875 5.00 0.800 2.00 0.500 1.30 0.231 Mnnterra Post Dev,pks Flow Frequency Analysis LouPearson III Coefficients Time Series FiIe:monterra post dev.tsfMeaO= -1.814 StdDov= 0.166 Project Location:Sea-Tac 5kew= 1.396 ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- FlowRate Rank Time of Peak - - Peaks - - Rank Return PrVb ([FS) ([FS) Period 0.136 9 2/16/49 17/45 0.391 I 89^58 0,989 8.183 S 3/03/50 15:00 0,233 2 32.13 0.969 0.878 35 8/27/51 18:00 0.207 3 19.58 0.949 0.092 27 10/17/51 7:15 0.189 4 14.08 0.929 0.066 43 9/38/53 3;80 0.183 S 10,09 0.909 0.076 38 12/19/53 17:38 0.153 6 9,01 0.889 0.064 46 7/30/55 21:15 0.140 7 7.64 0.869 0,096 20 10/04/55 10:00 0,138 8 6.63 0.849 0.893 24 12/09/56 12:45 0.136 9 5.86 0.829 0.086 32 1/16/58 10:00 0.114 18 5.24 0.808 0,209 14 10/18/58 19:45 0.112 11 4.75 0.789 0,110 13 10/10/59 32:00 0.111 12 4.34 0.769 0,093 25 2/14/61 20:15 0,110 13 3.99 0.749 0.077 37 8/04/62 13:15 0.109 14 3.70 0.729 0.076 39 12/01/62 20:15 0.103 15 3.44 0.709 0.059 48 6/05/64 15;08 0.102 16 3.22 0.690 0.088 30 4/20/55 19:30 0,101 17 3.03 0,670 0.069 49 1/05/66 15:00 0.099 18 2,85 0.658 0,101 16 11/13/66 17;45 0,099 lQ 2,70 0.630 8.207 3 8/24/68 15:00 8.096 20 2'56 0.610 0.890 29 10/20/68 22:00 0.095 21 2.44 0.590 0,054 50 1/13/70 20:45 0.094 22 2'32 8.570 8.065 45 12/86/70 7:00 0.094 23 2.32 0.550 0'140 7 12/08/71 17:15 0,093 24 2'13 0'530 0.077 36 4/18/73 9:30 0,893 25 2.04 0,510 0,094 22 11/28/73 8:88 0.093 26 1.96 0,490 0.099 18 8/17/75 23:00 0.092 27 1.89 0.478 0.869 42 10/29/75 7;00 0.091 28 1,82 0,450 0'062 47 8/23/77 14:30 0.090 29 1'75 0'430 0.112 ll 9/17/78 1:00 0'088 30 1.70 0.410 0'253 6 9/08/79 13:45 0.087 31 1.64 0'390 0.111 12 12/14/79 20:00 0,086 32 1,59 0.370 0.103 15 9/21/81 8:00 0.084 33 2,54 0.350 0.233 2 10/05/81 22:15 8.081 34 1.49 0.330 0.094 23 10/28/82 16:08 0'878 35 1,45 0.310 0'072 40 1/03/84 23:45 0.077 36 1.41 0.291 0'066 44 6/06/85 21:15 0'077 37 2,37 0.271 0.099 19 10/27/85 18:45 0'076 38 1.33 0,251 0,114 10 10/25/86 22:45 0.876 39 1'30 0,231 0'091 28 5/13/88 17:30 0'072 40 1.27 0.211 0'084 33 8/21/89 I6:09 0.071 41 I'24 0.191 /^�� t� � 0.138 8 1/09/90 5:30 8,093 26 4/03/91 20:15 0.071 41 1/27/92 15:00 8.087 31 6/09/93 12:15 0^081 34 11/17/93 16:45 0,095 21 6/05/95 17:00 0.101 17 5/19/96 11:30 0.391 l 12/29/96 21:45 8.189 4 10/84/97 14:15 Computed Peaks Computed Peaks Computed Peaks Computed Peaks Computed Peaks Computed Peaks Computed Peaks Computed Peaks Monterra Post Oev.pks 0.069 0.066 0.066 0.865 0,064 0.062 0.059 0,059 0.@54 0.338 0.273 0.219 0.162 0.152 0.127 0.089 8.072 42 1.21 0.171 43 1.18 0,151 44 1.15 0.131 45 1,12 0.111 46 1,I0 8.091 47 1,08 0.871 48 1.05 0.051 49 1,03 0.031 50 1.01 0.011 100.00 0.990 50,00 8.980 25,00 0.960 10.00 0.900 8,00 0.875 5.00 0,800 2,00 0.508 1.30 0.231 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN Stnnnvvutor6nm the proposed roof tops are collected and conveyed to two ioDkrudou ko'chca. The conveyance mymkxn upstreunn nfthe trenches is sized porK4unning`a Ruuu1ion. The 100 year flow rate (O./U3o{s) as determined by KRCT6 x0orno`pntcrmode| is used to size the conveyance system. The minimum pipe diunno1or, nnu1o,iu| type and slope is as follows: 6-inch /\US N-l2 at 0.50 percent. The minimum pipe slope per the City of Renton requirements is 0.5 percent. Using LDD"u Manning Calculator, u Manoin&m Coefficient (n) of 0.012 and the ufb,eno*udoned pipe parameter o:ou|tx in a full flow odo of 0.43o/s; tbunofbvo, the proposed ayutmn has sufficient capacity toconvey the |O0-ycur,|5minute flow rate. Puuc|45 9:\14038 doo Page146 P:\ 1403 8.0\Reports\Storm\Monterra.TIR.doe Roof Downspout 100 Year Calc.txt Manning Pipe Calculator Given Input Data: Shape ........................... Circular Solving for ..................... Flowrate Diameter ........................ 0.5000 ft Depth ........................... 0.5000 ft Slope ........................... 0.0050 ft/ft Manning's n ..................... 0.0120 Computed Results: Flowrate ........................ 0.4298 cfs Area ............................ 0.1963 ft2 Wetted Area ..................... 0.1963 ft2 Wetted Perimeter ................ 1.5708 ft Perimeter ....................... 1.5708 ft Velocity ........................ 2.1891 fps Hydraulic Radius ................ 0.1250 ft Percent Full .................... 100.0000 Full flow Flowrate .............. 0.4298 cfs Full flow velocity .............. 2.1891 fps Critical Information Critical depth .................. 0.3965 ft Critical slope .................. 0.0084 ft/ft Critical velocity ............... 3.5483 fps Critical area ................... 0.1714 ft2 Critical perimeter .............. 1.0783 ft Critical hydraulic radius ....... 0.1590 ft Critical top width .............. 0.5000 ft Specific energy ................. 0.6154 ft Minimum energy .................. 0.5947 ft Froude number ................... 0.7191 Flow condition .................. Subcritical Page 1 ( �t e 6.0 SPECIAL REPORTS AND STUDIES • Geoteclinical Report, prepared by ENSW dated December 10, 2015. Page 148 P:\14038.0\Reports\Storm\Monterra.TIR.doe Figure 6.1-- Geotechnical Engineer's Report Page 149 PAI 403 8.0\Reports\Storm\Monterra.TIR.doc ' t b M,44 Geotechnical Engineering' Geology Environmental Scientists` Construction Monitoring PREPARED FOR POOL BROTHERS CONSTRUCTION NOVEMBER 23, 2015 REVISED JUNE 27, 2016 ,yam Henr T. Wright, P.E. Project Engineer tip? t� Ft Co' i y i �.1t.,�` a, Raymond A. Coglas, P.E. Principal REVISED GEOTECHNICAL ENGINEERING STUDY MONTERRA TOWNHOMES 905 - SUNSET BOULEVARD NORTHEAST RENTON, WASHINGTON ES-3622 Earth Solutions NW, LLC 1805 —136th Place Northeast, Suite 201, Bellevue, Washington 98005 Ph:425-449-4704 Fax:425-449-4711 Toll Free: 866-336-8710 Geolecholocel E001fleeping Repopt Geetechnical SePivices Ape Performed for Specific Purposes, Persons( and Protects Geotechnical engineers structure their services to meet: the specific needs of their clients. A geotechnical engineering study conducted for a civil engi.. neer may not fulfill the needs of a construction contractor or even another civil engineer. Because each geotechnical engineering study is unique, each geotechnical engineering report is unique, prepared solelyfor the client. No one except you should rely on your geotechnical engineering report without first conferring with the geotechnical engineer who prepared it. And no one --- not evon you — should apply the report for any purpose or project except the one originally contemplated. Read the Full Report Serious problems have occurred because those relying on a geotechnical engineering report did not read if all. Do not rely on an executive summary. Do not read selected elements only. A Geotechnical EngineeNng Ge opt is Based on Unique Set of Project -Specific Factors Geotechnical engineers consider a number of unique, project -specific fac- tors when establishing the scope of a study. Typical factors include: the client's goals, objectives, and risk managerrnent preferences; the general nature of the structure involved, its size, and configuration, the location of the structure on the site; and other planned or existing site improvements, such as access roads, parking lots, and underground utilities. Unless the geotechnical engineer who conducted the study specifically indicates oth- erwise, do not rely on a geotechnical engineering report that was: • riot prepared for you, • not prepared for your project, • not prepared for the specific site explored, or • completed before important project: changes were made. Typical changes that can erode the reliability of an existing geotechnical engineering report include those that affect: the function of the proposed structure, as when it's changed from a parking garage to an office building, or from a light industrial plant to a refrigerated warehouse, elevation, configuration, location, orientation, or weight of the proposed structure, composition of the design team, or project ownership. As a general rule, always inform your geotechnical engineer of project changes ---even minor ones —and request an assessment of their impact. Ceotechniral engineers cannot accept responsibility or liability for problerns that occur because their reports do not consider developments of which they were not informer. Su sUrface Conditions Can Change A geotechnical engineering report is based on conditions that existed at [lie time the study was performed. Do not rely on a geotechnical engineer- ing reportwhose adequacy may have been affected by: the passage of time; by man -(Wade events, such as construction on or adjacent to the site; or by natural events, such as floods, earthquakes, or groundwater fluctua- tions. Always contact the geotechnical engineer before applying the report to determine if it is still reliable. A minor amount of additional testing or analysis could prevent major problems. Most Geotechnical Findings Are Professional Opinions Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. Geotechnical engi- neers review field and laboratory data and then apply their professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ —sometimes significantly — from those indicated in your report, Retaining the geotechnical engineer who developed your report to provide construction observation is the most effective method of managing the risks associated with unanticipated conditions. sport's Recommendations Are Not Final Do not overrely on the construction recommendations included in your report. Those mcomfnendations are notfinal, because geotechnical engi- neers develop them principally from judgment and opinion. Geotechnical engineers can finalize their recommendations only by observing actual subsurface conditions revealed during construction. 1hogook,,ohnical errgnaer who developed your report cannot assume responsibilily or liabRily for the reports recommendratiotis if that enginapi- does not perform construction observation. Ceotee nieal En inee inn Report is Subject to i " terpPetation Other design learn members' misinterpretation of geotechnical engineering reports has resulted in costly problems. Lower that risk by having your geo- technical engineer Confer with appropriate mernbeiss of the design team after submitting the report. Also retain your geotechnical engineer to review perti- nent elements of the design tearn's plans and specifications. Contractors can also misinterpret a geotechnical engineering report. reduce that risk by having your geotechnical engineer participate in prebid and preconstruction cuwnferences, and by providing construction observation'. o Not Re paw the ineep`s Logs Geotechnical engineers prepare final boring and testing logs based upon their interpretation of field logs and laboratory data. To prevent errors or omissions, the logs included in a geotechnical engineering report should never be redrawn for inclusion in architectural or other design drawings. Only photographic or electronic reproduction is acceptable, but recognize that separating logs from the repoll can elevate risk. Give Contpa tops a complete Repopt and Guidance Some owners and design professionals mistakenly believe they can make contractor: liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give con- tractors the complete geotechnical engineering report, but preface it with a clearly written letter of transmittal. in that letter, advise contractors that the report was not prepared for purposes of bid development and that the report's accuracy is limited; encourage them to confer with the geotechnical engineer who prepared the report (a modest fee may be required) and/or to conduct additional study to obtain the specific types of information they need or prefer. A prebid conference can also be valuable. Be sure conlrac- tors have ,sufficient firneto perform additionaf study. Only then aright you be in a position to give contractors the best information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Read Responsibility Ppovisiens Closely Some clients, design professionals, and contractors do riot recognize that geotechnical engineering is far less exact than other engineering disci- plines, This lack of understanding has created unrealistic expectations that have led to disappointments, claims, and disputes. To help reduce lire risk of such outcomes, geotechnical engineers commonly include a variety of explanatory provisions in their reports. Sometimes labeled "limitations" many of these provisions indicate where geotechnical engineers' responsi- bilities begin and end, to help others recognize their own responsibilities and risks. Head these provisions closely Ask questions. Your geoiechnical engineer should respond fully and frankly. Ce environ entai Con epns Are Not Covered The equipment, tochniques, and personnel used to perform a geoenviroll- mental study differ significantly from those used to perform a geotechnica! study. For that reason, a geotechnical engineering report does not usually relate any geoenvironnientai findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanliclp�rted environmental problems have led to olrmerous project failures, if you have not yet obtained your own geeen vironmental information, ask your geotechnical consultant for risk man- agement guidance. Do not rely on an environmental report prepared tot, someone else, Obtain Ppo essional Assistance To [leaf with of Diverse strategies can be applied during building design, construction, operation, and maintenance to prevent significant amounts of mold from growing on indoor surfaces. to be effective, all such strategies should be devised for the axpress purpose of mold prevention, integrated into a com- prehensive plan, and executed with diligent oversight by a professional mot(] prevention consultant. Because just a small amount of water or moisture can lead to the development of severe mold infestations, a num- ber of mold prevention strategies focus on keeping building surfaces dry. White groundwater, water infiltration, and sirnitar issues may have been addressed as part of the geotechnical engineering study whose findings are conveyed in fl,ris report, the geotechnical engineer in charge of this project is not a mold prevention consultant; none of the services per- formed in connection with the geotechnical engineer's study ruere designed or conducted for the purpose of mold prevon- tion. Proper implementation of the recommendations conveyed in this report will not of itself he sufficient to prevent mold from growing in or on the structure involved. Ref r n `ot p Ae-McMbelt eOt8c n iai Enneep lop Additional Assistance Membership in ASFE/The Best People on Earth exposes geotechnical engineers to a wide array of risk management techniques that can be of genuine benefit lot everyone involved with a construction project. Confer with you ASFE-member geotechnical engineer for more information. 8811 Galesville Road/Suite G106, Sliver Sluing, MD 20910 0ephone: 3011565-2733 Facsimile: 301/589-2017 e-mail: into@asfe.org 08AA asfe.org Capyril*r. 2004 by ASFE, (no, Duplication, reproduction, or copying of this docurnent, in whole o; in part, by any means whatsoever, is strictly prohibited, except with ASFE's specific Written permission Excerpting, quoting, or otherwise extracting wording from this docvurient is permitted only width the express written permission ofASFE, and only for purposes of scholarly research or .hook review Onry members of ASFE may use this docurnent as a complement to o, as an elarnent of a geotechnical eagineenny report: Any other firm, individual, or oilier entity that so uses this document without being an ASFE' member could be conrrrutting negligent or intentional tfraudulent) mrsrepirsentation. RGER06045.01''A November 23, 2015 Revised June 27, 2016 ES-3622 Pool Brothers Construction 720 North 1 oth Street, #A 105 Renton, Washington 98501 Attention: Mr. Dave Pool Earth Solutions NW LLC • Geotechnical Engineoring • Constilictioll Monitorillp) • Flivironmental scionce� Earth Solutions NW, LLC (ESNW) is pleased to present this report titled "Revised Geotechnical Engineering Study, Monterra Townhomes, 905 - Sunset Boulevard Northeast, Renton, Washington". This study has been revised to address City of Renton redline comments. In our opinion, development and construction of the proposed multi -family residential development is feasible from a geotechnical standpoint. Following site preparation and grading activities, the proposed building structure can be supported on conventional foundations bearing on competent native soil, recompacted native soil or new structural fill. In general, competent native soil suitable for support of foundations will likely be encountered between depths of approximately two to three feet below existing grades. Recommendations for site preparation and related earthwork activity, structural fill placement, foundation and retaining wall design, subsurface drainage, and other pertinent geotechnical recommendations are provided in this study. We appreciate the opportunity to be of service to you on this project. If you have any questions regarding the content of this geotechnical engineering study, please call, Sincerely, EARTH SOLUTIONS NW, LLC Henry'T. Wright, P.E. Project Engineer 1805 - 136th Place INLE,, Suite 20 1 0 Rellevue, V%4,' 98005 o (42S) 449-4704 & FAX (4215', 449 47 1' N Table of Contents ANN50 INTRODUCTION .............................................. 1 General ...................................... 1 Project Description ...... ........ ................ ........... 2 SITE CONDITIONS ........................................................ 2 Surface 2 Subsurface ................................ .......... 2 Topsoil.................... .............................. ...... 3 Fill ............................... 3 Native Soils ........... ........ ....... 3 Geologic Setting.. . ... ....... ...... ...... 3 Groundwater ....................... ........ 3 INFILTRATION EVALUATION ........... 4 Infiltration Recommendations_ ............. ........................ 4 GEOLOGICALLY HAZARDOUS AREAS ............... ............ ...... 4 DISCUSSION AND RECOMMENDATIONS .................................. 4 General.............................................................. 4 Site Preparation and General Earthwork. .............. 5 Temporary Erosion Control__ .... ....... 5 Stripping.......................... .......... ....................... 5 In -situ Soils .......... ........... ........ ...... 6 Imported Soils ................ ......................... 6 Subgrade Preparation... .......... .......................... 6 Structural Fill ............ ............ _ ........ ...... 6 Foundations ......................................... ........ ...... 7 Seismic Design ................ .......................... ........ 7 Slab -On -Grade Floors. .... .............. ............................. 7 RetainingWalls .................................... ......... _ ...... ....... 8 Drainage........ ................. ............ ....................... .............. .... 9 Excavations and Slopes .... ................... ....... 9 Pavement Sections ............................. ........... ......... .... 10 Utility Support and Trench BackfilL. ... __ ...... ............. 10 LIMITATIONS ....................... ....................................... ....... 11 Additional Services ....... ............ ................ Earth Solutions NW, LLC Table of Contents Cont'd Plate I Vicinity Map Plate 2 Test Pit Location Plan Plate 3 Retaining Wall Drainage Detail Plate 4 Footing Drain Detail Appendix A Subsurface Exploration Test Pit Logs Appendix B Laboratory Test Results Sieve Analysis Results Earth Solutions NW, LLC m REVISED GEOTECHNICAL ENGINEERING STUDY MONTERRA TOWNHOMES 906 — SUNSET BOULEVARD NORTHEAST RENTON, WASHINGTON General This geotechnical engineering study was prepared for the five-plex, three-story townhomes to be constructed on the west side of Sunset Boulevard Northeast near the intersection with Northeast 9t" Street in Renton, Washington. The purpose of this study was to perform subsurface explorations across accessible portions of the site, conduct appropriate analyses, and prepare geotechnical recommendations for the proposed development. This study has been updated to address City of Renton redline comments. Our scope of services for completing this geotechnical engineering study addressed the following: • Preparing a site geologic description including soil and groundwater conditions that may impact site development; • Providing a project -specific recommendations regarding site grading, drainage, structural fill requirements, erosion control, recommended pavement sections; • Providing soil bearing capacity, subgrade preparation, and other pertinent recommendations for foundation support; • Preparing an assessment of the suitability of the site soils for use as structural fill; • Preparing a preliminary infiltration evaluation to provide design infiltration rates, and; • Providing additional geotechnical recommendations, as appropriate. The following documents and maps were reviewed as part of our report preparation: • Online Web Soil Survey (WSS) resource maintained by the United States Department of Agriculture (USDA), Natural Resources Conservation Service; • Geologic Map of the Renton Quadrangle compiled by D.R. Mullineaux, dated 1965; • Conceptual Site Plan, by C.E.S. NW Inc., dated October 21, 2014; and 0 2009 King County Surface Water Design Manual (Renton). Pool Brothers Construction November 23, 2015 Revised June 27, 2016 Project Description ES-3622 Page 2 We understand that the subject site will be redeveloped with new townhomes and associated improvements. The proposed development will include construction of one structure with a total of five units and associated improvements. The proposed building will likely be three stories in height and constructed utilizing relatively lightly loaded wood framing supported on conventional foundations. Final building loads were not available at the time of this report. based on our experience with similar projects, we anticipate perimeter footing loads on the order of 1 to 2 kips per lineal foot (kIf) for each structural story. Slab -on -grade loading is anticipated to be on the order of 150 pounds per square foot (psf). Based on the existing topography, grading will be relatively minimal, and will likely require cuts and fills of less than three feet to achieve finish floor elevations. A stormwater infiltration trench facility will be located on the north side of the building which will infiltrate surface runoff into the native soil. The remainder of the site will be developed with general landscaping and paved walkways. If the above design assumptions are incorrect or change, ESNW should be contacted to review the recommendations in this report. ESNW should review the final design to verify that our geotechnical recommendations have been incorporated, SITE CONDITIONS Surface The site is located along the west side of Sunset Boulevard Northeast near the intersection with 9th Street in Renton, Washington. The approximate location of the property is illustrated on plate I (Vicinity Map). The site is roughly rectangular in shape and consists of one tax parcel (King County Parcel No. 311990-0051) totaling approximately 0.29 acres. The subject site is bordered to the east by Sunset Boulevard Northeast and private properties to the west, north, and south. The overall site topography is relatively level, with little discernible elevation change. The majority of the site is occupied by vegetation with areas of brambles and trees. Subsurface An ESNW representative observed, logged, and sampled four test pits on October 14, 2015 excavated at accessible locations within the property using a mini-trackhoe and operator retained by our firm. The test pits were completed for purposes of assessing soil conditions, classifying site soils, and characterizing subsurface groundwater conditions within the proposed development area. Earth Solutions NW, LLC ■ Pool Brothers Construction November 23, 2015 Revised June 27, 2016 ES-3622 Page 3 The approximate locations of the test pits are depicted on Plate 2 (Test Pit Location Plan). Please refer to the test pit logs provided in Appendix A for a more detailed description of subsurface conditions. Topsoil Topsoil was observed in the upper approximately 6 to about 12 inches of existing grades. Topsoil was characterized by dark brown color, the presence of fine organic material, and small root intrusions. Topsoil is not suitable for use as structural fill nor should it be mixed with material to be used as structural fill. Topsoil or otherwise unsuitable material can be used in landscape areas if desired. W] Fill was encountered during our fieldwork at test pit locations TP-1 and TP-2. The fill ranged from the existing ground elevation to a depth of one -and -one-half feet. The fill primarily consisted of loose silty sands (Unified Soil Classification, SM) in a damp condition. Localized areas of fill may be encountered throughout the site. Where encountered, fill should be observed by ESNW at the time of construction in order to assess the suitability for use as structural fill. Native Soils Underlying topsoil and fill, the native soils were encountered consisting primarily of medium dense to dense silty sand with gravel (Unified Soil Classification System SM), consistent with outwash and glacial till transitional deposits. USDA textural classification identified these soil types as fine sand, loamy sand, and sandy loam. Native soils were encountered primarily in a damp to moist condition and extended to the maximum exploration depth of nine -and -one-half feet below existing grades. Geologic Setting The referenced geologic map resource identifies ground moraine deposits for the subject site and immediately surrounding areas. As described on the geologic map, ground moraine deposits typically consists of lodgment till, deposited by the Puget glacial lobe. Lodgment till is generally comprised of compact, unsorted mixture of sand, silt, clay and gravel. Additionally, the referenced WSS resource identifies Ragnar-Indianola soils (map unit RdC) across the site and surrounding areas. The soil conditions encountered at -depth during our fieldwork were generally consistent with lodgment till with localized areas of outwash Indianola soils. Groundwater Groundwater seepage was not observed at the time of our fieldwork (October 14, 2015). We do not anticipate heavy groundwater seepage in the majority of the site excavations, except possibly in deeper utility excavations. Groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater flow rates are higher during the wetter, winter months. Earth Solutions Nw, LLC Pool Brothers Construction November 23, 2015 Revised June 27, 2016 INFILTRATION EVALUATION ES-3622 Page 4 As part of our study, we performed an infiltration evaluation for the proposed infiltration facilities. We understand the storm drainage for the proposed project will be designed using Appendix C of the 2009 King County Surface Water Design Manual (KCSWDM). We understand limited infiltration using infiltration trenches will be incorporated into the overall storm drainage design. Infiltration Recommendations The soils encountered within the proposed infiltration trench area (test pit location TP-1) and at the proposed infiltration trench depth (approximately 4 feet) generally consist of slightly gravelly fine sand (USDA classification) with loamy sand soils encountered at -depth and elsewhere on - site. Based on the soil and groundwater conditions observed at the test pit locations, we recommend the infiltration trenches should be sized in general accordance with Section C.2.3.3 of Appendix C of the 2009 KCSWDM. The infiltration design recommendation assumes infiltration within the more favorable outwash find sand soils identified within the northerly portions of the site. If the location of the proposed infiltration is changed, ESNW should review the infiltration design recommendation. We also recommend incorporating an emergency overflow provision in the infiltration system design; a splash block overflow with positive drainage away from the building will be sufficient. The soil and groundwater conditions should be confirmed by ESNW at the time of construction. GEOLOGICALLY HAZARDOUS AREAS As part of this geotechnical engineering study, Section 4-3-050 (CRITICAL AREAS REGULATIONS) of the Renton Municipal Code was reviewed with respect to geologically hazardous areas. Based on City of Renton online mapping, a very small corner of a high landslide hazard area is mapped within the southwest corner of the site. Based on the results of our site specific investigation the mapping is incorrect, and the site does not contain and is not immediately adjacent to any geologically hazardous areas. DISCUSSION AND RECOMMENDATIONS General Based on the results of our study, construction of townhomes at the site is feasible from a geotechnical standpoint. The primary geotechnical considerations associated with the proposed development include foundation support, slab -on -grade subgrade support, and minimizing post -construction settlements. Earth Solutions NW, LLC Pool Brothers Construction November 23, 2015 Revised June 27, 2016 ES-3622 Page 5 Based on the results of our study, the proposed building structure can be supported on conventional spread and continuous footings bearing on undisturbed, competent native soil, recompacted native soil or new structural fill. Based on our understanding of the proposed development, competent native soils suitable for support of foundation should be encountered at depths of between approximately two to three feet below existing grade. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with a suitable structural fill material, will be necessary. This study has been prepared for the exclusive use of Pool Brothers Construction, and there representatives. No warranty, expressed or implied, is made. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Site Preparation and Earthwork Site preparation activities will include installing temporary erosion control measures, establishing grading limits, and performing site stripping and clearing. Temporary Erosion Control Prior to finish grading and paving, temporary construction entrances and drive lanes, consisting of at least 12 inches of quarry spalls, should be considered in order to minimize off -site soil tracking and to provide a stable access entrance surface. Geotextile fabric may also be required underlying the quarry spalls for greater stability of the temporary construction entrance. Erosion control measures should consist of silt fencing placed around down -gradient margins of the site. Soil stockpiles should be covered or otherwise protected to reduce soil erosion. Temporary approaches for controlling surface water runoff should be established prior to beginning earthwork activities. Stripping Topsoil was generally encountered in the upper 6 to 12 inches of existing grades at the test pit locations. ESNW should be retained to observe site stripping activities at the time of construction. Over -stripping may result in increased project development costs and should be avoided. Topsoil and organic -rich soil is neither suitable for foundation support nor is it suitable for use as structural fill. Topsoil and organic -rich soil can be used in non-structural areas if desired. Earth Solutions NK LLC Pool Brothers Construction November 23, 2015 Revised June 27, 2016 In -situ Soils ES-3622 Page 6 From a geotechnical standpoint, native soils encountered at the test pit locations will generally be suitable for use as structural fill; however the native soils have a moisture sensitivity that can be characterized as moderate to high. Silty sand soils with fines contents greater than 5 percent typically degrade rapidly when exposed to periods of rainfall. Successful use of native soils as structural fill will largely be dictated by the moisture content at the time of placement and compaction. If the on -site soils cannot be successfully compacted, the use of an imported soil may be necessary. In our opinion, if grading activities take place during months of heavy rainfall activity, a contingency should be provided in the project budget for export of soil that cannot be successfully compacted as structural fill and import of granular structural fill. Imported Soils Imported soil intended for use as structural fill should consist of a well -graded granular soil with a moisture content that is at or slightly above the optimum level. During wet weather conditions, imported soil intended for use as structural fill should consist of a well -graded granular soil with a fines content of 5 percent or less defined as the percent passing the Number 200 sieve, based on the minus three-quarter inch fraction. Subgrade Preparation Uniform compaction of the foundation and slab subgrade areas will establish a relatively consistent subgrade condition below the foundation and slab elements. ESNW should observe the compacted subgrade prior to placing formwork, particularly where existing structures have been removed. Structural Fill Structural fill is defined as compacted soil placed in foundation, slab -on -grade, and roadway areas. Fill placed to construct permanent slopes and throughout retaining wall and utility trench backfill areas is also considered structural fill. Soils placed in structural areas should be placed in loose lifts of 12 inches or less and compacted to a relative compaction of 90 percent, based on the laboratory maximum dry density as determined by the Modified Proctor Method (ASTM D1557). Soil placed in the upper 12 inches of slab -on -grade, utility trench, and pavement areas should be compacted to a relative compaction of at least 95 percent. Additionally, more stringent compaction specifications may be required for utility trench backfill zones, depending on the responsible utility district or jurisdiction. Earth Solutions NW, LLC C�/ Pool Brothers Construction November 23, 2015 Revised June 27, 2016 Foundations ES-3622 Page 7 In our opinion, the proposed building structure can be constructed on competent native soil, recompacted native soil, or new structural fill. In general, competent native soil suitable for support of foundations will likely be encountered between depths of approximately two to three feet below existing grades. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with a suitable structural fill material, will be necessary. Provided foundations will be supported as described above, the following parameters can be used for design: Allowable soil bearing capacity 2,500 psf ® Passive earth pressure 300 pcf (equivalent fluid) ® Coefficient of friction 0.40 A one-third increase in the allowable soil bearing capacity can assumed for short-term wind and seismic loading conditions. The above passive pressure and friction values include a factor -of - safety of at least 1.5. With structural loading as expected, total settlement in the range of one inch and differential settlement of approximately one-half inch is anticipated. The majority of the settlements should occur during construction as dead loads are applied. Seismic Desi n The 2012 International Building Code recognizes the American Society of Civil Engineers (ASCE) for seismic site class definitions. Based on the soil conditions observed at the test pit locations, in accordance with Table 20.3-1 of the ASCE Minimum Design Loads for Buildings and Other Structures manual, Site Class D should be used for design. During our subsurface explorations completed on October 19, 2015, groundwater seepage was not encountered at the test pit locations. In our opinion, site susceptibility to liquefaction can be characterized as low. The generally consistent densities of the native soils and the lack of a consistently established groundwater table were the primary bases for this characterization. Slab -On -Grade Floors Slab -on -grade floors for proposed residential buildings constructed on the subject site should be supported on a firm and unyielding subgrade. Where feasible, native soils likely to be exposed at slab -on -grade subgrade levels can be compacted in situ to the specifications of structural fill. Unstable or yielding areas of the subgrade should be recompacted or overexcavated and replaced with suitable structural fill prior to construction of the slab. Earth Solutions Nw, LLC Pool Brothers Construction November 23, 2015 Revised June 27, 2016 ES-3622 Page 8 A capillary break consisting of a minimum of four inches of free -draining crushed rock or gravel should be placed below the slab. The free -draining material should have a fines content of 5 percent or less (percent passing the Number 200 sieve, based on the minus three-quarter inch fraction). In areas where slab moisture is undesirable, installation of a vapor barrier below the slab should be considered. If a vapor barrier is to be utilized, it should be a material specifically designed for use as a vapor barrier, and should be installed in accordance with the manufacturer's specifications. RetaininaWalls Retaining walls should be designed to resist earth pressures and any applicable surcharge loads. The following values should be used for concrete retaining and foundation wall design: « Active earth pressure (yielding wall) • At -rest earth pressure (restrained wall) • Traffic surcharge (passenger vehicles) • Passive earth pressure 0 Allowable soil bearing capacity 0 Coefficient of friction r- Lateral seismic surcharge 35 pcf (equivalent fluid / granular fill) 50 pcf 70 psf (rectangular distribution) 300 pcf (equivalent fluid) 2,500 psf 0.40 6H (where H equals wall height in feet) Additional surcharge loading from foundations, sloped backfill, or other loading should be included in the retaining wall design, where applicable. Drainage should be provided behind retaining walls such that hydrostatic pressures do not develop. If drainage is not provided, hydrostatic pressures should be included in the wall design. The geotechnical engineer should review retaining wall designs to confirm that appropriate earth pressure values have been incorporated into the design and to provide additional recommendations. Concrete retaining and foundations walls should be backfilled with free draining material that extends along the height of the wall, and a distance of at least 18 inches behind the wall. The upper one foot of the wall backfill can consist of a less permeable (surface seal) soil, if desired. A perforated drain pipe should be placed along the base of the wall, and connected to an appropriate discharge location. A typical retaining drainage detail is provided as Plate 3 of this study. Earth Solutions NW, LLC Fool Brothers Construction November 23, 2015 Revised June 27, 2016 Drainage ES-3622 Page 9 Perched groundwater should be anticipated in site excavations depending on the time of year grading operations take place, particularly in utility excavations at depth. Temporary measures to control surface water runoff and groundwater during construction would likely involve interceptor trenches and sumps. ESNW should be consulted during preliminary grading to identify areas of seepage and to provide recommendations to reduce the potential for instability related to seepage effects. Finish grades must be designed to direct surface drain water away from structures and slopes. Water must not be allowed to pond adjacent to structures or slopes. In our opinion, foundation drains should be installed along building perimeter footings. A typical foundation drain detail is provided on Plate 4. Excavations and Slopes The Federal Occupation Safety and Health Administration (OSHA) and the Washington Industrial Safety and Health Act (WISHA) provide soil classification in terms of temporary slope inclinations. Soils that exhibit a high compressive strength are allowed steeper temporary slope inclinations than are soils that exhibit a lower compressive strength. Based on the soil conditions encountered at the test pit locations, loose and medium dense native soils, fill or areas where groundwater seepage is exposed are classified as Type C by OSHA and WISHA. Temporary slopes over four feet in height in Type C soils must be sloped no steeper than 1.51-1:1V (Horizontal:Vertical). Dense native glacial till encountered without the presence of groundwater would be classified as Type A by OSHA and WISHA. Temporary slopes over four feet in height in Type A soils must be sloped no steeper than 0.75H:1V. Type A soils that are fissured, subjected to vibrations from heavy traffic, or have been otherwise previously disturbed must be classified as Type B by OSHA and WISHA. Temporary slopes over four feet in height in Type B soils must be sloped no steeper than 1H:1V. The presence of perched groundwater may cause caving of the temporary slopes due to excess pore pressure and seepage forces. ESNW should observe site excavations to confirm soil types and allowable slope inclinations. If the recommended temporary slope inclinations cannot be achieved, temporary shoring may be necessary to support excavations. Permanent slopes should maintain a gradient of 2H:1V, or flatter, and should be planted with vegetation to enhance stability and to minimize erosion. An ESNW representative should observe temporary and permanent slopes to confirm the slope inclinations are suitable for the exposed soil conditions, and to provide additional excavation and slope recommendations as necessary. Earth Solutions NW, LLC Pool Brothers Construction November 23, 2015 Revised June 27, 2016 Pavement Sections ES-3622 Page 10 The performance of site pavements is largely related to the condition of the underlying subgrade. To ensure adequate pavement performance, the subgrade should be in a firm and unyielding condition when subjected to proofrolling with a loaded dump truck. Structural fill in pavement areas should be compacted to the specifications previously detailed in this report. It is possible that soft, wet, or otherwise unsuitable subgrade areas may still exist after base grading activities. Areas containing unsuitable or yielding subgrade conditions will require remedial measures such as overexcavation and thicker crushed rock or structural fill sections prior to pavement. We anticipate new pavement sections will be primarily subjected to passenger vehicle traffic. For lightly loaded pavement areas subjected primarily to passenger vehicles, the following preliminary pavement sections can be considered: �► Two inches of hot mix asphalt (HMA) placed over four inches of crushed rock base (CRB), or; • Two inches of HMA placed over three inches of asphalt treated base (ATB). Heavier traffic areas (such as access drives) generally require thicker pavement sections depending on site usage, pavement life expectancy, and site traffic. For preliminary design purposes, the following pavement sections for heavy traffic areas can be considered: W Three inches of HMA placed over six inches of CRB, or; Three inches of HMA placed over four and one-half inches of ATB. The HMA, ATB and CRB materials should conform to WSDOT specifications. All soil base material should be compacted to at least 95 percent of the maximum dry density. Final pavement design recommendations can be provided once final traffic loading has been determined. City of Renton road standards may supersede the recommendations provided in this report. Utility Support and Trench Backfill In our opinion, the native soils will largely be suitable for support of utilities. Organic -rich soil is not considered suitable for direct support of utilities and may require removal at utility grades if encountered. Remedial measures may be necessary in some areas in order to provide support for utilities, such as overexcavation and replacement with structural fill, or placement of geotextile fabric. Groundwater seepage may be encountered in utility excavations, and caving of trench walls may occur where groundwater is encountered. Earth Solutions NW, LLC Pool Brothers Construction November 23, 2015 Revised June 27, 2016 ES-3622 Page 11 In general, the native soils should be suitable for use as structural backfill in the utility trench excavations, provided the soil is at or near the optimum moisture content at the time of placement and compaction. Moisture conditioning of the soils may be necessary at some locations prior to use as structural fill, especially where groundwater seepage is encountered. Each section of utility lines must be adequately supported in the bedding material. Utility trench backfill should be placed and compacted to the specifications of structural fill as previously detailed in this report, or to the applicable specifications of the City of Renton or other responsible jurisdiction or agency. LIMITATIONS The recommendations and conclusions provided in this geotechnical engineering study are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. A warranty is not expressed or implied. Variations in the soil and groundwater conditions observed at the test pit locations may exist, and may not become evident until construction. ESNW should reevaluate the conclusions in this geotechnical engineering study if variations are encountered. Additional Services ESNW should have an opportunity to review final project plans with respect to geotechnical recommendations provided in this report. ESNW should also be retained to provide testing and consultation services during construction. Earth Solutions NW, LLC NORTH Reference: King County, Washington Map 626 By The Thomas Guide Rand McNally 32nd Edition il NOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. Drwn. GLS Date 11/02/2015 Proj. No. 3622 Checked HTW Date Nov. 2015 Plate 1 i ■ 202 204 206 200, .. —LApproximate Location of TP-1 I ESNW Test Pit, Proj. No. ES-3622, Oct. 2015 Subject Site Proposed Building Proposed Infiltration Area NOTE: The graphics shown on this plate are not intended for design purposes or precise scale measurements, but only to illustrate the approximate test locations relative to the approximate locations of existing and / or proposed site features. The information illustrated is largely based on data provided by the client at the time of our study. ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. NOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. 0 20 40 80 Scale in Feet Test Pit Location Plan Monterra Townhomes Renton, Washington Drwn. GLS Date 11/02/2015 Proj. No. 3622 Checked HTW Date Nov. 2015 Plate 2 r, NOTES: 18" Min. O/}. p. 0 p �.. ° p �./.0 �.. O p. p Vp p 0 `O o dO p o p0° 0 Q gyp ° pp Op O 010 p p 0 0 0°ao �0 .0 ° ° p p O p °gyp0 a po as p p p o° O o O p0° p 0.0tiD�pO p 0 0. p0 ° 0p 0a° 00 °p O O°0 U p 0.6 oo I) O o ° p 0 ° p p o0 .0 Oo p o '0 o o 0 0 0. o " Q p o�°° ° o p °p p g ° 00 °°0p000 o p° o 0o o p po po 0 o p opp opop° ° 0. ° 0 ° 19 0 e o 0 op pop 0 0o �p o .0 p 0:*. • Free Draining Backfill should consist of soil having less than 5 percent fines. Percent passing #4 should be 25 to 75 percent. • Sheet Drain may be feasible in lieu of Free Draining Backfill, per ESNW recommendations. • Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1" Drain Rock. po0 0 00 0 0 Free Draining Structural Backfill r•r•r•r• ti•ti••.•ti•ti ti�L�'L?L�L 1 inch Drain Rock •r•r•r•r• Structural Fill \ Perforated Drain Pipe (Surround In Drain Rock) SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING RETAINING WALL DRAINAGE DETAIL Monterra Townhomes Renton, Washington Drwn. GLS Date 11/02/2015 Proj. No. 3622 Checked HTW Date Nov.2015 Plate 3 -�o Perforated Rigid Drain Pipe (Surround with 1" Rock) NOTES: • Do NOT tie roof downspouts to Footing Drain. o Surface Seal to consist of 12" of less permeable, suitable soil. Slope away from building. LEGEND: Surface Seal; native soil or other low permeability material. ti•ti•i J'•�'•J'•.••.7' " ;•r:};:;r 1 Drain Rock SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING FOOTING DRAIN DETAIL Monterra Townhomes Renton, Washington Drwn. GLS I Date 11/02/2015 Proj. No. 3622 Checked HTW Date Nov. 2015 Plate 4 _�4 Appendix A Subsurface Exploration ES-3622 The subsurface conditions at the site were explored by excavating a total of four test pits across the development envelope of the property. The approximate test pit locations are illustrated on Plate 2 of this report. The test pit logs are provided in this Appendix. The subsurface exploration was completed in October 2015 using a rubber -tired backhoe and operator subcontracted by ESNW. The test pits were excavated to a maximum depth of nine and one half feet below existing grades. Logs of the test pits excavated by ESNW are presented in Appendix A. The final logs represent the interpretations of the field logs and the results of laboratory analyses. The stratification lines on the logs represent the approximate boundaries between soil types. In actuality, the transitions may be more gradual. Earth Solutions NW, LLC ----% "I r L_ SYMBOLS TYPICAL. MAJOR DIVISIONS_ GRAPM LETTER DESCRIPTIONS CLEAN WELL -GRADED GRAVELS, GRAVEL - GRAVEL GRAVELS b � GW MIXTURES, LITTLE OR NO AND 3 FSAND INES o a _ POORLY -GRADED GRAVELS, GRAVELLY SOILS (LITTLE OR NO FINES) GP GRAVEL - SAND MIXTURES, LITTLE Q a OR NO FINES COARSE o a GRAINED GRAVELS WITH ° tl0 GM SILTY GRAVELS, GRAVEL -SAND - SOILS MORE THAN% FINES 0 SILT MIXTURES OF COARSE v FRACTION RETAINED ON NO. 4 SIEVE (APPRECIABLE r �.�+ CLAYEY GRAVELS, GRAVEL - SAND - AMOUNT OF FINES) CLAY MIXTURES CLEAN SANDS SW WELL -GRADED SANDS, GRAVELLY MORE THAN 50% SAND SANDS, LITTLE OR NO FINES OF MATERIAL IS AND LARGER THAN SANDY NO.200 SIEVE SOILS OR NO FINES) SP POORLY -GRADED SANDS, GRAVELLY SAND, LITTLE OR NO SIZE (LITTLE FINES SANDS WITH SILTY SANDS, SAND - SILT MORE THAN50% FINES `�M MIXTURES OF COARSE FRACTION PASSING ON NO. 4 SIEVE (APPRECIABLE �' ' ', SC CLAYEY SANDS, SAND - CLAY AMOUNT OF FINES) MIXTURES INORGANIC SILTS AND VERY FINE ML SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY SILTS INORGANIC CLAYS OF LOW TO NE FINE LIQUID LIMIT AND FEE CL MEDIUM PLASTICITY, GRAVELLY GRAINED LESS THAN 50 CLAYS CLAYS, SANDY CLAYS, SILTY SOILS CLAYS, LEAN CLAYS OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY MORE THAN 50% INORGANIC SILTS, MICACEOUS OR OF MATERIAL IS MH DIATOMACEOUS FINE SAND OR SMALLER THAN SILTY SOILS NO. 200 SIEVE slzE SILTS AND LIQUID LIMIT CI I INORGANIC CLAYS OF HIGH CLAYS GREATER THAN 50 PLASTICITY OH ORGANIC CLAYS OF MEDIUM TO ^� M HIGH PLASTICITY, ORGANIC SILTS HIGHLY ORGANIC SOILS " PT PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. Earth Solutions NW TEST PIT NUMBER TP-1 1805 - 136th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 Telephone: 425-449.4704 Fax: 425-449-4711 CLIENT pod, Brothers Constructing PROJECT NAME Monterra Townhomes PROJECT NUMBER „3622 PROJECT LOCATION Renton W s i n to _ _ _._,.. _... _.__. __11a_! _. ._._ . DATE STARTED 10/14/15 COMPLETED 10/14/15 GROUND ELEVATION TEST PIT 512E EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: EXCAVATION METHOD _ _ , AT TIME OF EXCAVATION LOGGED BY HTW CHECKED BY HTW AT END OF EXCAVATION -- NOTES Brambles AFTER EXCAVATION w w vi a LU TESTS v o O MATERIAL DESCRIPTION z c7 uz 0 Brown silty SAND with gravel, loose, damp (Fill) SM iiYYY 111 INIx Tan silty SAND with gravel, medium dense, damp = MC $.50% SM i ... .. _. ....__. _... ..... Tan silty fine SAND, medium dense, damp MC = 7.70% I` -weakly cemented Sin i i MC = 11.80% i _ Fines = 12.70% [USDA Classification: tan slightly gravelly fine SAND] ! Tan poorly graded fine SAND with silt, medium dense to dense, damp MC = 4.00% SP- ( -weakly cemented _ SM MC = 12.80% ( Gray silty SAND, dense, moist - Fines = 26.80% SM -moderately cemented _ i i [USDA Classification: gray slightly gravelly loamy SAND] Test pit terminated at 9.5 feet below existing grade. No groundwater encountered during excavation. Bottom of test pit at 9.5 feet. 0 ui a z a. tV J a F- x � m w z w w.. ....a ............ ..........a............ ....... .w...._. µ. w.._.. Earth Solutions NW 1805 - 136th Place N.B., Suite 201 TEST PIT NUMBER TP-2 Bellevue, Washington 98006 PA GE 1 OF 1 Telephone; 425-449-4704 4 aFax: 425-449-4711 CLIENT Pod Brothers Constructing PROJECT NAME Monterra Townhomes,_ _ PROJECT NUMBER 3622 PROJECT LOCATION Renton, Washington _._... DATE STARTED _10/14/15 COMPLETED "a , _ GROUND ELEVATION TEST PIT SIZE ._ EXCAVATION CONTRACTOR NWU C ggav10ting, GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION LOGGED BY HTW _ _ _. _ CHECKED BY HTW .. ., _. AT END OF EXCAVATION .._ NOTES Brambles., ... y_ AFTER EXCAVATION _--- _......,.... uj aL 1�- ui U ul 2EUj TESTS a MATERIAL DESCRIPTION Q z C� U) 0 Brown silty SAND with gravel, loose, damp (Fill) SM Light brown silty SAND with gravel, loose to medium dense, damp � = MC 4.20% I i= ' SM ii t i +1.5 5 Tan - gray silty SAND with gravel, dense, moist j -moderately cemented SM MC = 5.30% } ! Test pit terminated at 7.0 feet below existing grade. No groundwater encountered during C excavation. Bottom of test pit at 7.0 feet. n iv f- t� -7 e a A. C' ni Rrm a i m J Q M' Earth Solutions TEST PIT NUMBER TP-3 1805 _ 13C�th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT Pod Brothers Constructing PROJECT NAME Monterra Townhomes PROJECT NUMBER 3622 PROJECT LOCATION Renton, Washington ....... _.._ .... ,.._ w..... DATE STARTED 10/14[15 COMPLETED 10/14/15 GROUND ELEVATION _ TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating _ _ GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION -•- LOGGED BY HT1N .. .. _ CHECKED BY HTW_ AT END OF EXCAVATION --- NOTES Depth of Topsoil. & Sod 1y2':1 brambles _e.., . _.._...... AFTER EXCAVATION w aw w TESTS cn U 0-6 7- O MATERIAL DESCRIPTION az O 0 0 TOPSOIL to 12" TPSL,, 1.0 I} Tan silty SAND with gravel, loose to medium dense, damp MC = 9,10% SM i -becomes medium dense -increasing sand content = MC 6.40% Test pit terminated at 5.5 feet below existing grade. No groundwater encountered during excavation. l i i Bottom of test pit at 5.5 feet. _7L Earth Solutions NW TEST PIT NUMBER TP-4 1805 - 136th Place N.E., Suite 201 r r ' Bellevue, Washington 98005 PAGE 1 OF 1 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT Pod _Brothers Constructing_, _ PROJECT NAME Monterra Townhomes PROJECT NUMBER 3622 _ _ . PROJECT LOCA11 TION Renton, Washington _ --- DATE STARTED 10/14/15 , COMPLETED 10/14/15 GROUND ELEVATION _ _ _ TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating __ GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION _. LOGGED BY _ HTW CHECKED BY HTW AT END OF EXCAVATION --- NOTES , Depth, of Topsoil & Sod�6": brambles AFTER EXCAVATION w w u? CT i W TESTS C MATERIAL DESCRIPTION o QZ 0 0 TPSL `' `-` 0.5 TOPSOIL to 6" Tan silty SAND with gravel, loose to medium dense, damp � (3 I -becomes medium dense SM f 5 MC = 7.90% Fines = 29.50% [USDA Classification: tan slightly gravelly sandy LOAM] IMG -becomes dense, moderately cemented = 7.90% To Test pit terminated at 7.0 feet below existing grade. No groundwater encountered during excavation. 1 a £ i Bottom of test pit at 7.0 feet. F £ i i i { t £ Appendix B Laboratory Test Results ES-3622 Earth Solutions NW, LLC -�-(6 Earth Solutions NW GRAIN SIZE DISTRIBUTION - 136th Place N.E., Suite 201 IM1805 Bellevue, WA 96005 Telephone: 42 5-284-3300 CLIENT _ Pool Brothers Construction . _, _ ___ _ _ __ PROJECT NAME ,MontarraTownhomes _ PROJECT NUMBER , S-16,22 _ _ _ _ ..___. ___ _ PROJECT LOCATION Renton -. -... _. U.S. SIEVE OPENING IN INCt IES U 5. SIEVE NUMBERS HYDROMETER 6 4 3 2 1 5 1 4 1i2� 3 6 & 14 1 20 30 40 50 60 100 140200 100 a 95 _ __, ._ __.. 90 _____ _ 85 80 75 70 _,.._. __ ,.. _� . _........ ..... ..._._. . _.. _ .,. ._ .. _....., F-- t C360 `w �_..._. _, _..._ _,. �.._ ... _. �.,. ,...._.., ..,», . , �. _. ». ..v.. _ _... ..� ...- _.... 's 55 _.... ,.._ _. __ . ,. _ _.»<_. .......... w 50 _.' z , 45 ...... r, .... _.._ _. __ _...._ z w 40 w o_ 35- 30 _.. _. ....... ._.... 25 20 ,_, ._ w ..... .. . , , .. m.. _... m = — - .. _. .. . ` 15 __ _ I 10 f _ -- 5 ' : ,...� _ _. - 0 _. .__ Specimen Identification TP-16.Oft._ z TP-1 9.Oft. TP-4 _5.0ft �jz 0 I__..__________ GRAIN SIZE IN MILLIMETERS ........ GRAVEL SAND ..._.._ ... _ �_._ .....M.._�.... ..................... . _ .......... coarse fine coarse medium fine SILT OR CLAY 01 Classification Cc Cu ..... USDA Tan Slightly Gravelly Fine Sand, USCS: SM _ _...... ___._ __ _.__. _. USDA: Gray Slightly Gravelly Loamy Sand USCS SM. _.._._ __.�_ ...—_..._.._.._..._.. .__ _ USDA: Tan Slightly GravellySandyLoam. USCS: SM. Specimen Identification D100 D60 D30 D10 LL TP_1 6.Oft 4.75 0.19 0.124 �, . _ �.. _._...., _._ <1 z TP-1 9.Oft. 9.5 0.241 0.089 A T - 5-aft- 19 0.227 0.077 PL PI %Silt . 12.7 26.8 29.5 Report Distribution ES-3622 EMAIL ONLY Pool Brothers Construction 720 North I Oth Street, #A1 05 Renton, Washington 98501 Attention: Mr. Dave Pool EMAIL ONLY C.E.S. NW, Inc. 310 — 29th Street Northeast, Suite 101 Puyallup, Washington 98372 Attention: Ms. Jennifer Caldwell Earth Solutions NW, LLC � 0 7.0 OTHER PERMITS The following permits and/or approvals are thought to be required as part ofthis project: • Postmaster Approval ® Building Permits • Right of Way Permit P:\14038.0\Reports\Storm\MonteiTa.TIR.doe Page 181 8.0 ESC ANALYSIS AND DESIGN TESC measures are put into place to prevent sediment from leaving the site. The site slopes from east to west at an approximate rate of 10%. The proposed TESC plan, Construction Pollution Prevention Plan, includes and is not limited to the following guidelines set in the Manual and the City Amendments to Appendix D of the 2009 King County Surface Water Design Manual in order to comply with Core Requirement No. 5. Clearing Limits — The clearing limits are on the engineering plans and will be Tagged in the field. Cover Measures — Cover measures are specified on the TESC plan set and will be implemented in the field as necessary. These cover measures include mulching, temporary seeding, and plastic covering. Perimeter Protection —The silt fence and clearing limits will be shown on the TESC plans and implemented in the field. The silt fence is placed on the downslope side of the property. During construction no runoff shall leave the site. Traffic Area Stabilization — Traffic area stabilization will be addressed by a stabilized construction entrance. Sediment Retention — Retention will be established by silt fences around the perimeter and catch basin inserts that will control of the on -site sediment -laden water. Surface Water Collection — Runoff will be routed to the collection ditches and routed to a sediment trap if necessary. Dewatering Control — Any water from dewatering shall be filtered or contained so sediment can filter out prior to discharge downstream. Dust Control — Dust control by splinklering will be provided as needed. Wet Season Construction: Infrastructure cconstruction will be conducted in the summer months. Any construction planned during the wet season will be according to King County and the City of Renton standards. Construction Within Sensitive Areas and Buffers: There are no onsite sensitive areas or buffers. Maintenance: Maintenance requirements are detailed in the TESC notes on the engineering plans. Final Stabilization: Upon completion of the project, all disturbed areas will be stabilized and Best Management Practices removed if appropriate. P:\14038.0\Reports\Storm\Monterra.TIR.doc Page 182 9.0 BOND QUANTITIES The City of Renton Bond Quantity Wodkxheo< is included within this moo<knn. P:\|4038 doo Puuc|83 E m U) ƒ go % 2 W . ƒ \ k�L:%\ k9±ma E E Q / 0 ƒUr ) E k E X E k a J E ƒ < = & f e y / \ S � / / / / 7< & a G 2 } \ \ \ - ) \ ) E f ! § 7 § COE f 2 L c k j j \ / / - ƒ E / \ m / 3 7 § ] / / w / § /\ Jf // \ \ \ q y * E �E }\ A) E § ƒ - \ � ) ® \ § / E y \ \ J E m , § E R / E ) % ± \ 'Fa\ / [ - 0 \ ± 0\ < 3 ƒ# E \ ) _\ ) k § _ \ / \ \ \ \ / (Y) C) 4i M U) 0 :tf m _0 c m0 E 0 L- QL E a) :tf U) Q C) (D (.0 (6 CY) Cta RS Ri 0 E 0 4— a) cu a a) 0 U- C w E a 0 tD uj CD t-D co -A N r,4 9) r, IM N LI) >, >1 0 U) CO C E 0 0 0) 0. V) u %- tn "F 0 -2 U) 0) fu E Lu 41 L- m O =3 N CT CD 0 %b Ln C: 0 m Ln rq M I E m m w 0 0 z z v co (D C: Zo, C: 0 Irgo Cl. 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P:\14038.0\Reports\Storm\Monterra.TIR.doc Page 193 RECORDING REQUESTED BY AND WHEN RECORDED MAIL TO: CITY CLERK'S OFFICE CITY OF RENTON 1055 SOUTH GRADY WAY RENTON WA 98057 FOR MAINTENANCE AND INSPECTION OF FLOW CONTROL BMPS Grantor: Pool Brothers Construction Grantee: City of Renton Legal Description: PARCEL B OF 907 ABERDEEN AVE LOT LINE ADJUSTMENT LUA-06-126-LLA RECORDED MARCH 20, 2007 UNDER RECORDING NUMBER 20070320900004, IN THE OFFICIAL RECORDS OF KING COUNTY, WASHINGTON. Additional Legal(s) on: NA Assessor's Tax Parcel ID#: 311990-0051 IN CONSIDERATION of the approved City of Renton(check one of the following) ® residential building permit, ❑ commercial building permit, ❑ clearing and grading permit, ❑ subdivision permit, or ❑ short subdivision permit for Application File No. LUA/SWP relating to the real property ("Property") described above, the Grantor(s), the owner(s) in fee of that Property, hereby covenants(covenant) with City or Renton, a political subdivision of the state oi' Washington, that he/she(they) will observe, consent to, and abide by the conditions and obligations set forth and described in Paragraphs I through 8 below with regard to the Property. Grantor(s) hereby grants(grant), covenants(covenant), and agrees(agree) as follows: 1. Grantor(s) or his/her(their) successors in interest and assigns ("Owners") shall retain, uphold, and protect the stormwater management devices, features, pathways, limits, and restrictions, known as flow control best: management practices ("BMPs"), shown on the approved Flow Control BMP Site Plan for the Property attached hereto and incorporated herein as Exhibit A. 2. The Owners shall at their own cost, operate, maintain, and keep in good repair, the Property's BMPs as described in the approved Design and Maintenance Details for each BMP attached hereto and incorporated herein as Exhibit B. 3. City or Renton shall provide at least 30 days written notice to the Owners that entry on the Property is planned for the inspection of the BMPs. After the 30 days, the Owners shall allow the City of Renton to enter for the sole purpose of inspecting the BMPs. In lieu of inspection by the City, the Owners may elect to engage a licensed civil engineer registered in the state of Washington who has expertise in drainage to inspect the BMPs and provide a written report describing their condition. If the engineer option is chosen, the Owners shall provide written notice to the City of Renton within fifteen days of receiving the City's notice of inspection. Within 30 days of giving this notice, the Owners, or the engineer on behalf of the Owners, shall provide the engineer's report to the City of Renton. If the report is not provided in a timely manner as specified above, the County may inspect the BMPs without further notice. 4. If the City determines from its inspection, or from an engineer's report provided in accordance with Paragraph 3, that maintenance, repair, restoration, and/or mitigation work is required for the BMPs, The City shall notify the Owners of the specific maintenance, repair, restoration, and/or mitigation work (Work) required under RMC 4-6-030. The City shall also set a reasonable deadline for completing the Work or providing an engineer's report that verifies completion of the Work. After the deadline has passed, the Owners shall allow the City access to re -inspect the BMPs unless an engineer's report has been provided verifying completion of the Work. If the work is not completed properly within the tirne frame set by the City, the City may initiate an enforcement action. failure to properly maintain the BMPs is a violation of RMC 4-6-030 and may subject the Owners to enforcement under the RMC 1-3, including fines and penalties. 5. Apart from performing routine landscape maintenance, the Owners are hereby required to obtain written approval from the City or Renton before performing any alterations or modifications to the BMPs. 6. Any notice or approval required to be given by one party to the other under the provisions of this Declaration of Covenant shall be effective upon personal delivery to the other party, or after three (3) days from the date that the notice or approval is mailed with delivery confirmation to the current address on record with each Party. The parties shall notify each other of any change to their addresses. 7. This Declaration of Covenant is intended to promote the efficient and effective management of surface water drainage on the Property, and it shall inure to the benefit of all the citizens of the City of Renton and its successors and assigns. This Declaration of Covenant shall run with the land and be binding upon Grantor(s), and Grantor's(s') successors in interest and assigns. 8. This Declaration of Covenant may be terminated by execution of a written agreement by the Owners and the City of Renton that is recorded by King County in its real property records. IN WITNESS WHEREOF, this Declaration of Covenant for the Maintenance and Inspection of Flow Control BMPs is executed this._,__, day of--------------, 20 GRANTOR, owner of the Property GRANTOR, owner of the Property STATE OF WASHINGTON ) COUNTY OF KING )ss. On this day personally appeared before me: , to me known to be the individual(s) described in and who executed the within and foregoing instrument and acknowledged that they signed the same as their free and voluntary act and deed, for the uses and purposes therein stated. Given under my hand and official seal this __._ day of 20 Printed name Notary Public in and for the State of Washington, residing at My appointment expires E APPIiNDIX A MAIN'I'I�:NAN('li Rf?OIJ1Rt?MIiN'I;S I'OR I:I.OW CON'hROI,, (`ONVI:YANCti, AND WO I:A(LL,I'1'I1?S NO.2 - INFILTRATION FACILITIES Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance Is Performed Site Trash and debris Any trash and debris which exceed 1 cubic foot Trash and debris cleared from site. per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Noxious weeds Any noxious or nuisance vegetation which may Noxious and nuisance vegetation constitute a hazard to County personnel or the removed according to applicable public. regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in Grass or groundcover mowed to a height, height no greater than 6 inches. Infiltration Pond, Top Rodent holes Any evidence of rodent holes if facility is acting Rodents removed or destroyed and or Side Slopes of as a dam or berm, or any evidence of water dam or berm repaired. Dam, Berm or Embankment piping through dam or berm via rodent holes. Tree growth Tree growth threatens integrity of dams, berms or Trees do not hinder facility slopes, does not allow maintenance access, or performance or maintenance interferes with maintenance activity. If trees are activities. not a threat to dam, berm, or embankment integrity or not interfering with access or maintenance, they do not need to be removed. Erosion Eroded damage over 2 inches deep where cause Slopes stabilized using appropriate of damage is still present or where there is erosion control measures. If erosion potential for continued erosion. Any erosion is occurring on compacted slope, a observed on a compacted slope. licensed civil engineer should be consulted to resolve source of erosion. Settlement Any part of a dam, berm or embankment that has Top or side slope restored to design settled 4 inches lower than the design elevation. dimensions. If settlement is significant, a licensed civil engineer should be consulted to determine the cause of the settlement. Infiltration Pond, Sediment if two inches or more sediment is present or a Facility infiltrates as designed. Tank, Vault, Trench, accumulation percolation test indicates facility is working at or or Small Basin less than 90% of design. Storage Area Infiltration Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents. Tank bent out of Any part of tank/pipe is bent out of shape more Tank repaired or replaced to design. shape than 10% of its design shape. Gaps between A gap wider than '/,inch at the joint of any tank No water or soil entering tank sections, damaged sections or any evidence of soil particles entering through joints or walls. joints or cracks or the tank at a joint or through a wall. tears in wall Infiltration Vault Damage to wall, Cracks wider than 1/2-inch, any evidence of soil Vault is sealed and structurally Structure frame, bottom, and/or entering the structure through cracks or qualified sound. top slab inspection personnel determines that the vault is not structurally sound. 2009 Surface Water Design Manual - Appendix A 1/9/2009 A-3 AI'PL:NDIX A MAINTI NANCI: RI QUIRI_;MENTS FLOW CONTROL., CONVEYANCE, AND WQ FACIITFIL'S NO. 2 - INFILTRATION FACILITIES Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance Is Performed Inlet/Outlet Pipes Sediment Sediment filling 20% or more of the pipe. iniet/outiet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatabies and non-fioatables). Damaged Cracks wider than 1/2-inch at the joint of the No cracks more than '/-inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlot pipes. Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Manhole access covered. Any open manhole requires Immediate maintenance. Locking mechanism Mechanism cannot be opened by one Mechanism opens with proper tools. not working maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Cover/lid difficult to One maintenance person cannot remove Cover/lid can be removed and remove cover/lid after applying 80 Ibs of lift. reinstalled by one maintenance person. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Large access Damaged or difficult Large access doors or plates cannot be Replace or repair access door so it doors/plate to open opened/removed using normal equipment. can opened as designed. Gaps, doesn't cover Large access doors not flat and/or access Doors close flat and covers access completely opening not completely covered. opening completely. Lifting Rings missing, Lifting rings not capable of lifting weight of door Lifting rings sufficient to lift or rusted or plate. remove door or plate. Infiltration Pond, Plugged Filter bag more than '12 full. Replace filter bag or redesign Tank, Vault, Trench, system. or Small Basin Filter Bags Infiltration Pond, Sediment 6" or more of sediment has accumulated. Pre -settling occurs as designed Tank, Vault, Trench, accumulation or Small Basin Pre - settling Ponds and Vaults Infiltration Pond, Plugged High water level on upstream side of filter Rock filter replaced evaluate need Rock Filter remains for extended period of time or little or no for filter and remove if not water flows through filter during heavy rain necessary. storms. Infiltration Pond Rock missing Only one layer of rock exists above native soil in Spillway restored to design Emergency Overflow area five square feet or larger, or any exposure of standards. Spillway native soil at the top of out flow path of spillway. Rip -rap on inside slopes need not be replaced. Tree growth Tree growth impedes flow or threatens stability of Trees removed. spillway. 1/9/2009 2009 Surface Water DesignManual— Appendix A A-4 APPIiNDIX A MAIN'I'F.NANC'I: RGQtIIREMENTS FOR I"I.OW CONTROL, CONVI;YAN(`I , AND WO FACIL ITIES NO.5 - CATCH BASINS AND MANHOLES Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed Structure Sediment Sediment exceeds 60% of the depth from the Sump of catch basin contains no bottom of the catch basin to the invert of the sediment. lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Trash and debris Trash or debris of more than % cubic foot which No Trash or debris blocking or is located immediately in front of the catch basin potentially blocking entrance to opening or is blocking capacity of the catch basin catch basin. by more than 10%. Trash or debris in the catch basin that exceeds No trash or debris in the catch basin. 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. Dead animals or vegetation that could generate No dead animals or vegetation odors that could cause complaints or dangerous present within catch basin. gases (e.g., methane). Deposits of garbage exceeding 1 cubic foot in No condition present which would volume, attract or support the breeding of insects or rodents. Damage to frame Corner of frame extends more than '/< inch past Frame is even with curb. and/or top slab curb face into the street (if applicable). Top slab has holes larger than 2 square inches or Top slab is free of holes and cracks, cracks wider than '% inch. Frame not sitting flush on top slab, i.e., Frame is sitting flush on top slab. separation of more than inch of the frame from the top slab. Cracks in walls or Cracks wider than % inch and longer than 3 feet, Catch basin is sealed and bottom any evidence of soil particles entering catch structurally sound. basin through cracks, or maintenance person judges that catch basin is unsound. Cracks wider than '/2 inch and longer than 1 foot No cracks more than 1/4 inch wide at at the joint of any inlet/outlet pipe or any evidence the joint of inlet/outlet pipe. of soil particles entering catch basin through cracks. Settlement/ Catch basin has settled more than 1 inch or has Basin replaced or repaired to design misalignment rotated more than 2 inches out of alignment. standards. Damaged pipe joints Cracks wider than '/,inch at the joint of the No cracks more than M-inch wide at inlet/outlet pipes or any evidence of soil entering the joint of inlet/outlet pipes. the catch basin at the joint of the inlet/outlet pipes. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Inlet/Outlet Pipe Sediment Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatabies). Damaged Cracks wider than 1/2-inch at the joint of the No cracks more than Y inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. 2009 Surface Water Design Manual —Appendix A 1/9/2009 l A-9 t APPENDIX A MAINTENANCE RI;Q(JIRI:MI:N'I'S FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 5 - CATCH BASINS AND MANHOLES Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance Is Performed Metal Grates Unsafe grate opening Grate with opening wider than 1/8 inch. Grate opening meets design (Catch Basins) standards. Trash and debris Trash and debris that is blocking more than 20% Grate free of trash and debris, of grate surface. footnote to guidelines for disposal Damaged or missing Grate missing or broken member(s) of the grate. Grate is in place and meets design Any open structure requires urgent standards. maintenance. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Cover/lid protects opening to Any open structure requires urgent structure. maintenance. Locking mechanism Mechanism cannot be opened by one Mechanism opens with proper tools. Not Working maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Cover/lid difficult to One maintenance person cannot remove Cover/lid can be removed and Remove cover/lid after applying 80 lbs. of lift. reinstalled by one maintenance person. 1/9/2009 2009 Surface Water Design Manual — Appendix A A-10 to I APPENDIX A MAIN'I'I NANCI� RI QUIRLMI NI;S l�Oli l�LOW ('ONTROL, CONVI YANCI , ANI) WQ I,A('11,1'1'IGS NO.6 - CONVEYANCE PIPES AND DITCHES Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Pipes Sediment & debris Accumulated sediment or debris that exceeds Water flows freely through pipes. accumulation 20% of the diameter of the pipe. Vegetation/roots Vegetation/roots that reduce free movement of Water flows freely through pipes. water through pipes. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damage to protective Protective coating is damaged; rust or corrosion Pipe repaired or replaced. coating or corrosion is weakening the structural integrity of any part of pipe. Damaged Any dent that decreases the cross section area of Pipe repaired or replaced. pipe by more than 20% or is determined to have weakened structural integrity of the pipe. Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 Trash and debris cleared from square feet of ditch and slopes. ditches. Sediment Accumulated sediment that exceeds 20% of the Ditch cleaned/flushed of all sediment accumulation design depth. and debris so that it matches design. Noxious weeds Any noxious or nuisance vegetation which may Noxious and nuisance vegetation constitute a hazard to County personnel or the removed according to applicable public. regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vegetation Vegetation that reduces free movement of water Water flows freely through ditches. through ditches. Erosion damage to Any erosion observed on a ditch slope. Slopes are not eroding. slopes Rock lining out of One layer or less of rock exists above native soil Replace rocks to design standards. place or missing (If area 5 square feet or more, any exposed native Applicable) soil. 2009 Surface Water Design Manual — Appendix A 1/9/2009 A-11 Al'PI NDIX A MAIN"1'1.sNANC'P, REQU1ltEMEN"I'S I�I,OW CONTROL,, CONVEYANCE, AND WQ FACILITIES NO. 11 - GROUNDS (LANDSCAPING) Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Site Trash or litter Any trash and debris which exceed 1 cubic foot Trash and debris cleared from site. per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Noxious weeds Any noxious or nuisance vegetation which may Noxious and nuisance vegetation constitute a hazard to County personnel or the removed according to applicable public. regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in Grass or groundcover mowed to a height. height no greater than 6 inches. Trees and Shrubs Hazard Any tree or limb of a tree identified as having a No hazard trees in facility. potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible. Damaged Limbs or parts of trees or shrubs that are split or Trees and shrubs with less than 5% broken which affect more than 25% of the total of total foliage with split or broken foliage of the tree or shrub. limbs. Trees or shrubs that have been blown down or No blown down vegetation or knocked over. knocked over vegetation. Trees or shrubs free of injury. Trees or shrubs which are not adequately Tree or shrub in place and supported or are leaning over, causing exposure adequately supported; dead or of the roots. diseased trees removed. 1/9/2009 2009 Surface Water Design Manual — Appendix A A-16 103