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Home My WebLink About03312 - Technical Information Report . _ . I � : ��J ��'� � � � Z J � rth t Th i r ' � � New Park at No eas d Court � m � and Union Avenue Northeast Renton, Washington � TECHNICAL INFORMATION REPORT � .. .�'.F�.�1.�1 z - �1 ., r Y�:.\t� � I ' ��l �/ 1./ . - �Y��}N`� \��_ • -�! �� M � .- l\f� � ..�-. , 'l� _ � � ` �. �1� r g� '{ _, i ,�' _ � _ --'; j`i �,::J.'.:�:ti, L �>��i�� / n 2�h �. �g� ,��/ � , l _�'*.i��'`C'�''') �%'=�;�;� � ?�r_�,_� �_.^';�`/ ��.__..__ � � � Consulting Engineers � 1601 Fifth A�enue, Suite 1600 Seattle, WA 98101 � � c,l y Prepored by: Katie Herold �` aFq KPFF Project No. 105 I 66.10 ��9 CF/�r�'^ F> � � Februory 27, 2006 ��.'/;l�� JOfI.. d 3� iz . . •-- • , � � New Park a1 Noriheast Th�rd Courf and Union Avenue Northeast Techniml Informotion Report Renton, Woshington TABLE OF CONTENTS . Page SECTION 1- PROJECT OVERVIEW........................................................................................... 1 r' i ; Pre-developed Site Conditions.............................................................................................. 1 t4 DevelopedSite Conditions ................................................................................................... 1 � SECTION 2 - CONDITIONS AND REQUIREMENTS SUMMARY..................................................2 '� Core Requirements..............................................................................................................2 �� SECTION 3 - OFF-SITE ANALYSIS ............................................................... ............................3 _ � SECTION 4 - FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN...........3 r, Part A - Existing Site Hydrology.............................................................................................3 �� Parf B- Developed Site Hydrology ........................................................................................4 Part C - Performance Standards ...........................................................................................S Part D - Flow Control............................................... .. .. .. . � . . . . ................................................5 SECTION 5 - CONVEYANCE SYSTEM ANALYSIS AND DESIGN .................................................5 r� SECTION 6 - SPECIAL REPORTS AND STUDIES ........................................................................S ° SECTION 7 - OTHER PERMITS................................................................................................6 -, SECTION 8 - EROSION AND SEDIMENT CONTROL ANALYSIS AND DESIGN ............................6 --3 SECTION 9 - BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT.6 � SECTION 10 - OPERATIONS AND MAINTENANCE MANUAL....................................................6 � � � � � � � r� KPFF Consulhng Engineers i February 28, 2006 J �- ,,. �_ • ' New Park at Norfheast Third Court and Union Avenue Northeost Technical Information Report Ren�on, Washingion -� SECTION l- PROJECT OVERVIEW � � The new park at Northeast Third Court and Union Avenue Norfheast is a proposed public park to include a play field, walking trail, basketball court, play structures, picnic facilities, public restroom, and parking for six vehicles. The site is 9.18 acres but the proposed project will only impact 6.38 acres of the site. - The site address is 233 Union Avenue Northeast located in Renton, Washington. PRE-DEVELOPED SITE CONDITIONS __ The existing site is 100 percent pervious with forest and pasture groundcovers except for a small decomposed grovel road. The site is split up into three threshold drainage basins. The northwest basin sheet flows drainage to the north and northwest. On the north side of the site, drainage sheet flows into the curbline of Noriheast Third Courf where it is collected in catch basins and conveyed westerly. Drainage also sheet flows across the site to the west and onto the adjacent : property where it is collected in catch basins. The northeasi basin sheet flows to the east and into :.: the storm drainage system in Union Avenue Northeast where it continues northerly. The majority of the site is contained in the southwest basin which sheet flows in a westerly direction onto the -�� adjoining property to the west where it is collected in catch basins. � � DEVELOPED SITE CONDITIONS � The developed site will mostly consist of pervious surfaces with some new impervious surfaces consisting of new sidewalk and paved paths, a paved ploza, a small parking lot, and a restroom � and picnic shelter. The new on-site improvements will cover approximately 6.38 acres. The developed condition drainage maintains the three pre-developed threshold basins. � The northwest basin consists of grass, asphalt pathways, part of the sport field, and the unmodified forested area. The northwest basin sheet flows to the northwest, some of the drainage entering the catch basins in Northeast Third Court and some of it sheet flowing to the � property to the northwest ond into catch basins in their parking lot. The northeast basin consists of grass, sidewalk, and the proposed parking lot. The drainage � sheet flows into Union Avenue Northeast where it is collected and conveyed into catch basins in the street. � The southwest basin contains the plaza area, sidewalks, playgrounds, half the sporf fields, and the remaining pervious grass and existing forested areos. The plaza and playground droinage is collected in catch bas�ns and tight-lined to the west where it terminates in a flow dispersion trench � that reintroduces the storm drainage into a sheet flow condition across the undisturbed forested area of the site. The remainder of the southwest basin sheet flows across the site before discharging on to the adjacent property to the southwest as in the pre-developed condition. � � � � J _ _ . . _ , � . New Pork ot Northeast Third Court and Union Avenue Northeost 7echnical Information Reporf , Renion, Washington I SECTION 2— CONDITIONS AND REQUIREMENTS SUMMARY CORE REQUIREMENTS ' • Core Requirement No. 1 - Discharge at the Natural Locotion The manner in which droinage is discharged from the site is maintained from the � pre-developed to the developed condition. Currently drainage is un-concentrated and sheet flows onto the adjocent properties and into the streets. The developed condition will ' ' also be un-concentrated discharge across the property line and into the streets. ,,,� Drainage will not be significantly added to, or diverted from, the pre-developed threshold dischorge areas. + • Core Requirement No. 2 - Off-Site Analysis s . The downstream conditions have been reviewed and determined to be stable. • Core Requirement No. 3 - Flow Control � This project is exempt from implementing flow control using the exemptions listed in the ��i 1990 King County Surface Water Design Manual (KCSWDM). -- • Core Requirement Ncs. 4 - Conveyance System - � The conveyance system was designed to meet the 2005 KCSWDM Core Requirements for new pipe systems. The system was designed to convey the 25-year storm without � overtopping any catch basins. • Core Requirement No. 5 - Erosion and Sediment Control ' -' The erosion and sediment control plan was designed per the requirements in Appendix D „j of the KCSWDM. � • Core Requirement No. 6 - Maintenance and Operations 'I `y The City of Renton Community Services or their designee will maintain all on-site drainage facilities. The City of Renton Public Works will maintain drainage facilities in the � right-of-way. • Core Requirement No. 7 - Financial Guarantees and Liability � Guarontees and liability issues will not be required, as the City of Renton Community Services owns the facility and will be maintaining it. • Core Requirement No. 8 - Water Quality � The project proposes to add less than 5,000 square feet of pollution generating I impervious surfaces, thus will not require water quality treatment. I � � Special Requirements ii None of the five special requirements apply to this proposal. " I � ,� _ � 3 il ° r � � KPFF Consulnng Eng�neers 2 February 28, 2006 ,� ._ , � New Park at Norfheast Third Court ond Union Avenue Norfheast Technical Information Reporf Renton, Washington -, SECTION 3— OFF-SITE ANALYSIS The downstream conditions for the proposed new park development have been evaluated and determined to have no identifiable problems. The extent of the study extended downstreom for � 1/4-mile from the discharge points. The downstream was evoluated for the three primary discharge basins from the site. � The small basin draining to Union Avenue Norfheast is conveyed in underground pipe northward to Northeast Fourth Street. There are no known problems with this system as the conveyance system � appears to be sized appropriately for the flows and there are no opporfunities for erosion and no , -� flooding problems. � The northwest basin drains into an underground pipe storm drainage system and is conveyed westerly . through the adjocent apartment complex over to the cemetery. The site storm water discharges onto paved surfaces and then directly into catch basins and underground piping so there is no erosion � opportunity. There are no known problems with this conveyance system and no flooding issues. � � The southwest bosin sheet flows onto the adjacent property where it is immediately collected in catch basins and conveyed in underground pipes through the property in a southwesterly direction. There are no known problems with this conveyance system, no erosion problems, and no flooding ', � issues. � � SECTlON 4 —FLOW CONTROL AND WATER QUALITY FACIUTYANALYSIS AND DESIGN � PART A— EXISTING SlTE HYDRO�OGY In its current condition, the site cover primarily consists of forest and pasture surfaces with two small gravel drivewoys. Currently the site can be divided into three different threshold discharge � oreas. The northwest basin consists of 2.2 acres of pasture, forest, and a small amount of gravel sloping to Northeast Third Court and the adjacent properfy to the northwest. The slopes in this basin range from 1 to 25 percent. The southwest basin consists of 6.53 acres of pasture, forest, � and gravel gently sloping to the southwest. The slopes range from 3 to 25 percent. The northeast basin consists of 0.46 acres of pasture, forest, and gravel, which slopes out to Union Avenue Northeast and is collected in existing catch basins. The slopes in this basin range � from 1 to 16 percent generally in an easierly direction. See Appendix A, Figure 4 for on existing conditions map. � There used to be a single-family residence on the central easterly quarter of the site. In that area, a layer of fill material, approximately 2 feet deep, has been placed. Underlying the fill, there is ' approximately 2 to 3 feet of weathered glacial till overlying non-weathered glacial till. Also in this � area, there are two old gravel roads that have been weathered over time. The forest and pasture areas have an organic topsoil overlying the till layers. The Soil Conservation Service soils map shows the site as AgC, which is Alderwood gravely sandy loam with 6 to 15 percent slopes, � (Appendix A, Figure 3). i . . . _ . . � � KPFF Consulhng Engineers 3 Februory 28, 2006 • �� i New Pork at Northeast Third Court and Union Avenue Northeasf Technicol Information Report II Renfon, Washington The Pre-developed Basin Characteristics are as foliows: II � � Northeast Basin 'I Gravei Road = 0.013 acres ! _, Pasture = 0.096 acres i Forest = 0.346 acres -- Northwest Basin � Gravel Road = 0.1 acres �� Pasture = 1 .031 acres �� Forest = 1 .065 acres � ; Southwest Basin <� Gravel Road = 0.032 acres Pasture = 1 .88 acres I j Forest = 4.617 acres � � PART B — DEVELOPED SI7E HYDROLOGY � The developed site maintains the same three threshold ba"sins as the exiting conditions. The northeast basin consists of the porking lot, grass areas, and some sidewalk that sheet flows II into Union Avenue Northeast and into the existing storm drainage system. The northwest basin , consists of grass, unmodified forested areas, and some sidewalk, which sheet flows to ihe existing storm drainage system in Northeast Third Court and the adjacent property to the norfhwest. ' The southwest basins consist of grass, unmodified forest, sidewalk, and plaza areas. The plaza � area and play areas are being collected in new catch basins and conveyed to a flow dispersion trench to allow the drainage to flow un-concentraied through the forested area to, match the '� existing drainage patterns. See Appendix A, Figure S for a developed conditions map and area breakdowns. � The developed basin characteristics are as follows: � Northeast Basin Impervious = 0.147 acres Grass = 0.364 acres � Northwest Basin Impervious = 0.144 acres � Grass = 1 .465 acres Forest = 0.855 ocres � Southwest Basin Impervious = 0.49 acres Grass = 3.65 acres � Forest = 2.07acres . . , i II � � KPFF Consulting Engineers 4 Febrvary 28, 2006 , . . � New Park a�Northeasr Th�rd Court and Union Avenue Northeost Technicol Informotion Report Ren�on, Washington PAR7 C— PERFORMANCE STANDARDS Per the City of Renton's direction, the site characteristics are to be evaluated to determine if flow control is required by reviewing the exemptions to flow control as described in the 1990 KCSWDM. The conveyance system has been designed to convey the 25-year storm without overtopping any ; structures. � Water quality is not required because the project adds less than 5,000 square feet of pollution � generating impervious surfaces. PAR7 D— FLOW CONTROL � Each basin was evaluated to determine if it met any of the exemptions to flow control as described in the 1990 KCSWDM. The manual states that if your increase in 100-year peak flow , t rate is less than 0.5 cfs from existing to developed conditions then flow control is not required. JEach basin was under the 0.5 cfs increase in flow rate, thus meeting the flow control exemption. The basins were evaluated using Santa Barbara Urban Hydrogroph method with StormShed. i 1 - Please see Appendix 6 for a detailed basin onalysis. � �' The 100-year peak flow rates from pre-developed to developed is as follows: , Northeast Basin Pre-developed = 0.12 cfs 1 Developed = 0.19 cfs Northwest Basin � Pre-developed = 0.34 cfs Developed = 0.51 cfs Southwest Basin iPre-developed = 1 .1 cfs Developed = 1 .37 cfs " SECTION 5— CONVEYANCE SYSTEM ANALYSIS AND DESIGN � The new on-site conveyance system was sized using the backwater calculations spreadsheet. The conveyance system was sized to convey the 25-year storm without overtopping the catch bosins. � The conveyance and backwater calculations spreadsheet is provided in Appendix B. SECTION 6—SPECIAL REPOR7S AND �TUDIES � The geotechnical report is provided in Appendix C. , 1 II � KPFF Consulting Engineers 5 Februory 28, 2006 �.� ' , Ne�.v rark ot Northeast Th�ra Court and Urion A�enue NoRheest Techn�ca!iniormohon Repor' � Renton, Woshington i SECTION 7—OTHER PERMITS I, � Washington State Department of Ecology National Pollutant Discharge Elimination System Permit. SECTION 8—EROSION AND SEDlMENT CONTROL ANALYSIS AND DESIGN i, - The erosion and sediment control plan was designed using Appendix D of the KCSWDM. II� : ' The primary sediment control will be through filter fabric fence along the downhill sides of the ' ; perimeter. � � 3 SECTION 9—BOND QUANTITIES, FACIUTY SUMMARIES, AND DECLARATION OF COVENANT , 1 A bond quantities worksheet is not required. A stormwater facility summory sheet does not apply ; _ since there are no flow control facilities or water quality facilities. A declaration of covenant is not —. opplicable. ' �i I', ...,,- SECTION 10— OPERATJONS AND MAINTEJ�iANCE A�NUAL - I� `� The on-site drainage facilities will be maintained by the City of Renton. � � � � .x � � � � � . . . � ; � � KPFF Consulting Eng�neers 6 Februa,ry 28, 2006 { r �� ? � �. _[ � � �3,.� i �.' �� h t � r .' • Vicinity � ' , � • SCS soils Map • Existing Basins Map -� :: • Developed Basins Map �, .J � � ..t .� � � � � � . . � s 3 � •.! ,,, . , I King County Department of Development and Environmental Services I�'� �--� TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND Part 2 PROJECT LOCATION AND ' PROJECT ENG(NEER DESCRIPTION � Projec Owner Project Name • Li�e Rcrtf�rL Con+rrtcin� Ser��Lt�S Ncw Pavk a.�'NE 3r�Leur�aK�. U►t�b+ti NE Address Location I 0 5 5 S. brar.�u 1�/au . Ren te►11�t/R 9 F� Township 23 /1� Phone Ran e � E jy25) y 30- 6617 s�hy �4 9 'Y.��ly Af...Section �� ,_ Project Engine r NE �/�� Ka�r� N�e�o�� Company KPFF( � �I�� ` �rs � Address/Phone /60l 5�`hvc Sw� l600, � ti, wh 9 lo! ' Part 3 TYPE OF PERMIT Part 4 OTHER REVIEWS AND PERMITS APPLICATION , Subdivison DF�N HPA Shoreline Management ,.� Short Subdivision COE 404 Rockery � Grading DOE Dam Safety Structural Vaults Commercial , FEMA Floodplain Other � Other COE Wetlands � ,; Part 5 SlTE COMMUNITY AND DRAINAGE BASIN � Communiry � Ren.�or� , Wasl� in 4 to►� Drainage Basi Lc��r C�Y TZi ve✓' . � 7 Part 6 SITE CHi4RACTERISTIGS J River Floodplain � X Wetlands ►'t0►1 �^r u.la�-�e'� Stream Seeps/Springs Critical Stream Reach High Groundwater Table � Depressions/Swales ,� Groundwater Recharge Lake Other � Steep Slopes J � F� � � '-� Part 7 SOILS Soil Type Slopes Erosion Potential Erosive Velcoties __ Ide o v�1 1�oa►n 6 -!5 % �aw-a�crt�� Additional Sheets Attached - - Part 8 DEVELOPMENT LIMITATIONS REFERENCE LIMITATION/SITE CONSTRAINT " � Ch. 4—Downstream Analysis ►�t0�� —? 1 _J , Additional Sheets Attached � Part 9 ESC REQUIREMENTS , � � MINIMUM ESC RE�UIREMENTS MINIMUM ESC REQUIREMENTS , DURING CONSTRUCTION AFTER CONSTRUCTION '� Sedimentation Facilities k Stabili2e Exposed Surface � �Stabilized Construction Entrance x Remove and Restore Temporary ESC Facilities , � X Perimeter Runoff Control )( Clean and Remove All Silt and Debris I, � X Clearing and Graing Restrictions X Ensure Operation of Permanent Facilities " ' X Cover Practices Flag Limits of SAO and open space � � preservation areas ' Construction Sequence i Other Other � ! J � � � � � � � . ; � J F/ • + Part 10 SURFACE WATER SYSTEM Grass Lined Tank Infiltration Method of Analysis Channel Vault Depression 1 xPipe System Ener Dissa ator �r Flow Dis ersal Compensation/Mitigati 9Y p /` P on of Eliminated Site "' Open Channel Wetland Waiver Storage Dry Pond Stream Regional � Wet Pond Detention .3 - Brief Description of System Operation Dra�Naa�. co�le��'ec� t'rl cnl-c� bassih5 � A 1n C� P 1 D e. TO 4 7�'�w cl�5 D e YS 4� t'►'�VLC� !N�b �►'c5 Tf� are,0` � � Facility Related Site Limitations , Reference Faciliry Limitation �� Part 11 STRUCTURAL ANALYSIS Part 12 EASEMENTSlfRA�TS � _� Cast in Place Vault Drainage Easement Retaining Wall Access Easement � Rockery>4' High Native Growth Protection Easement Structural on Steep Slope Tract � Other Other '�I Part 13 SIGNATURE OF PROFESSIONAL ENGINEER . - ::.� I or a civil engineer under my supervision my supervision have visited the site. Actual site � conditions as observed were incorporated into this worksheet and the attachments. To the best of my knowledge the information provided here is accurate. � � z,/oc Si ned/Dat � � �� ' � J �{ � M�..___�� . . Lr- -..-A .. I . J J ..j ..... .1 --...� w^. .. ' � � � � �nwa..uN/ . I N�o� __ V . . '�`+:. � � N` .,'T I o rti � �...I,. f' _ �1� ��d, : ■' � �• _ � _ � I � . . �m o I . -.�' . ._r. ; � _.�; 5f�4 l 9.--", � ��s��` � _ `... _ 1 o�<�'D �l . . .f� .a. 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'� / ' � . , � } /,`/� �i" � \`. i� �,� , . .._ _.._. y,��_ _.1 \ . i-: .T � -. ___....�..____ - - ' - - - ) / ' � —1 --�-- . - - - ._-_..._ -.—' --- f� 1 - _1� � � ,' -1r ' ___ � � . i'� �-- -..�-�_ , - � :�` � 1 � � '� ` ' � 4 /� , , � ' `, Y' !�',/ ' -� i. / '` j ` __ �- -- - - r � ',` '.� 'f � , '� -�•/ -�._ � 1 � :.,�� 3 if � J f' / {� � \ _�-, , ; ,t -- - � ;' %,, i ,,_ ,%�,- �, , .`�," � ; ,�f �'��'J �. � �-- � ' -�� ' . , � � ,, ;� � � � ", ;� " � '. ," ; , =' �� i , � ; � ; � .: . • . --- � � ---•- . � � Z _ � . . - _ __ , _� --_.. - .__- . .S c w,, , w, , > � DEVELOPED BASINS �� ' a z 0 Basin Name Total Area(acres) Impervious Area(acres) Pervious Area(acres) � � Northeast 0.5111 acres 0.1475 acres 0.3635 acres II Northwest 2.4640 acres 0.1440 acres 2.3200 acres Southwest 62070 acres 0.4875 acres 5]190 acres J SCALE 1"= 100' � NEW PARK AT NE 3RD COURT os/za/2ooe L�� CITY OF AND UNION AVENUE NE .��"".r�"r"�,..' .� � RENTON � o�+E "°' � 1 �� "T F11 � DEVELOPED BASINS � S �,�`,n� c�oq su-e.0 ...c�o.�.u-.ib vbrn*w��9/�,w� wo.r. o.y� s wor a+e .�C„ SC1LE ICCOHDRICLY • � I r� Appendix B ; • Pre-developed to Developed Basin Analysis for 100yr peaks, Flow Control Exemption • Conveyance Calculations ' r.., � � � t � �� ..-} :.i ' rt i.f � � � � �: CJ � . . Flow Control Exemption i Pre-developed to Developed Basin Analysis � for 100yr peaks 1 f _ _ � 1 i � � i ( � � I I � � . . , j 3 S � . S . , I � , � r , t • : � � � � Existin_q Stormwafer Runoff Calculations: i � Precipitation: 3 2yr 24-hour: 2 in 10yr 24-hour: 2.9 in ? 25yr 24-hour. 3 4 in } 50yr 24-hour: 3.4 in 100yr 24-hour: 3.9 in i � neexisting Event Summary: ; BasinlD Peak Q Peak T Peak Vol Area Method Raintype Event � ------- (cfs) (hrs) (ac-ft) ac /Loss i neexisting 0.12 8.00 0.0562 0.45 SBUH/SCS TYPEIA 100 yr I 1 Drainage Area: neexisting . Hyd Meth�d: SBUH Hyd Loss Method: SCS CN Number 1 Peak Factor: 484.00 SCS Abs: 0.20 Storm Dur: 24.00 hrs Intv: 10.00 min ' Area CN TC Pervious 0.4420 ac 72.57 0.14 hrs Impervious 0.0130 ac 95.00 0.03 hrs Total 0.4550 ac � Supporting Data: Pervious CN Data: Forest 73.00 0.3460 ac � Pasture 71.00 0.0960 ac Impervious CN Data: gravel yd 95.00 0.0130 ac Pervious TC Data: � Flow type: Description: Length: Slope: Coeff: Travel Time Shallow Forest 50.00 ft 6.00% 3.0000 1.13 min Sheet pasture area 50.00 ft 2.00% 0.1500 7.12 min � Impervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Sheet gravel yd 40.00 ft 4.00% 0.0500 1.87 min � � . � 1 � ' . ; . : l 1 , . r ' Proposed Development Stormwater Runoff Calculations: , 1 ' Precipitation: � 2yr 24-hour: 2 in � 10yr 24-hour: 2.9 in 25yr 24-hour: 3.4 in 50yr 24-hour: 3.4 in , � 100yr 24-hour: 3.9 in jNEdeveloped Event Summary: BasinlD Peak Q Peak T Peak Vol Area Method Raintype Event • ------- (cfs) (hrs) (ac-ft) ac /Loss � NEdeveloped 0.i 9 8.00 0.0912 0.51 SBUHlSCS TYPE 1 A 100 yr Drainage Area: NEdeveloped , � Hyd Method: SBUH Hyd Loss Method: SCS CN Number Peak Factor: 484.00 SCS Abs: 0_20 Storm Dur: 24.00 hrs Intv: 10.00 min � Area CN TC � Pervious 0.3635 ac 74.00 0.57 hrs Impervious 0.1475 ac 98.00 0.01 hrs Total 0.5110 ac I� � Supporting Data: ' Pervious CN Data: Grass Lawn 74.00 0.3635 ac � Forest 73.00 0.0000 ac Impervious CN Data: Plaza and Path 98.00 0.1475 ac Pervious TC Data: � Flow type: Description: Length: Slope: Coeff: Travel Time Shallow Forest 200.00 ft 7.00% 3.0000 4.20 min Sheet upper park area 300.00 ft 2.00% 0.1500 29.85 min � Impervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Sheet across plaza 40.00 ft 2.00% 0.0110 0.74 min I 1 conc►�sior,: Using the 1990 King County Surface Water Design Manual, flow control is not required } when there is less than a 0.5cfs increase from existing conditions to developed - conditions for the 100yr peak 24-hour storm. The existirig peak flow rate, Q, for the Northeast Basin is 0.12cfs. The proposed development would increase this flow rate to l0.19cfs; an increase of 0.07cfs. This increase is less than 0.5cfs which means Flow Control=is not required for this basin. . . ! 1 • t } i - • . . 1 ' Existin_q Stormwater Runotf Calculations: ! ; Precipitation: � 2yr 24-hour: 2 in 10yr 24-hour: 2.9 in 25yr 24-hour: 3.4 in j 50yr 24-hour: 3.4 in 100yr 24-hour: 3.9 in � nwexisting Event Summary: i BasinlD Peak Q Peak T Peak Vol Area Method Ra�ntype Event 1 ------- (cfs) (hrs) (ac-ft) ac /Loss nwexisting 0.34 8.50 0.2707 2.20 SBUH/SCS TYPEtA 100yr i Drainage Area: nwexisting � Hyd Method: SBUH Hyd Loss Method: SCS CN Number Peak Factor: 484.00 SCS Abs: 0.20 Storm Dur. 24.00 hrs Intv: 10.00 min I Area CN TC IPervious 2.0960 ac 72.02 0.83 hrs � Impervious 0.0998 ac 95.00 0.01 hrs Total 2.1958 ac � Supporting Data: Pervious CN Data: Pasture 71.00 1.0310 ac � Forest 73.00 1.0650 ac Impervious CN Data: gravel yd 95.00 0.0998 ac Pervious TC Data: � Flow type: Description: Length: Slope: Coeff: Travel Time Sheet sheet in pasture area 300.00 ft 2.00% 0.2400 43.47 min Shallow Through forest 300.00 ft 7.00% 3.0000 6.30 min � Impervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Sheet gravel yd 20.00 ft 4.00% 0.0110 0.32 min � I ) - � � � e _ Proposed Developmenf Sformwater Runoff Calculations: • Precipitation: 2yr 24-hour: 2 in 10yr 24-hour: 2.9 in �__ 25yr 24-hour. 3.4 in 50yr 24-hour: 3.4 in 100yr 24-hour: 3.9 in � NWdeveloped Event Summary: � BasinlD Peak Q Peak T Peak Vol Area Method Raintype Event . ------ (cfs) (hrs) (ac-ft) ac /Loss NWdeveloped 0.51 8.00 0.3337 2.46 SBUH/SCS TYPEtA 100 yr � Drainage Area: NWdeveloped � Hyd Method: SBUH Hyd Loss Method: SCS CN Number , Peak Factor: 484.00 - SCS Abs: 0.20 . '� �� Sbrm Dur. 24.00 hrs Intv: 10.00 min Area CN TC Pervious 2.3202 ac 73.63 0.57 hrs ' Impervious 0.1440 ac 98.00 0.01 hrs Total 2.4642 ac Supporting Data: Pervious CN Data: Grass Lawn 74.00 1.4650 ac - Forest 73.00 0.8552 ac Impervious CN Data: • Plaza and Path 98.00 0.1440 ac Pervious TC Data: � Flow type: Description: Length: Slope: Coeff: Travel Time Shallow Forest 200.00 ft 7.00% 3.0000 4.20 min Sheet upper park area 300.00 ft 2.00% 0.1500 29.85 min j Impervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time � Sheet across plaza 20.00 ft 2.00% 0.0110 0.42 min � Conclusion: � Using the 1990 King County Surface.Water Design Manual, flow control is not required_ when there is less than a 0.5cfs increase from existing conditions to developed � conditions for the 100yr peak 24-hour storm. The existing peak flow rate, Q,00, for the Northwest Basin is 0.34cfs. The proposed development would increase this flow rate to � 0.51 cfs; an fncrease of 0.17cfs. This� increase is less than 0.5�fs which means Flow � � Control is not required for this basin. � t i � ' � � 1 Existin_q Stormwater Runoff Calculations: , � Precipitation: 2yr 24-hour: 2 in I 10yr 24-hour: 2.9 in 25yr 24-hour: 3.4 in 50yr 24-hour: 3.4 in � 100yr 24-hour: 3.9 in � swexisting Event Summary: BasinlD Peak C� Peak T Peak Vol Area Method Raintype Event ------- (cfs) (hrs) (ac-ft) ac /Loss swexisling 1.10 8 17 0.7766 6.53 SBUFUSCS TYPEIA 100 yr 1 Drainage Area: swexisting Hyd Method: SBUH Hyd Loss Method: SCS CN Number ( Peak Factor. 484.00 SCS Abs: 0.20 Storm Dur: 24.00 hrs Intv: 10.00 min Area CN TC � Pervious 6.4970 ac 72.42 0.57 hrs Impervious 0.0320 ac 95.00 0.00 hrs Total 6.5290 ac Supporting Data: � Pervious CN Data: Pasture 71.00 1.8800 ac Forest 73.00 4.6170 ac � Impervious CN Data: gravel yd 95.00 0.0320 ac. Pervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time � Sheet sheet in pasture area 300.00 ft 6.00% 0.2400 28.01 min Shallow Through forest 300.00 ft 8.00% 3.0000 5.89 min Impervious TC Data: � Flow type: Description: Length: Slope: Coeff: Travel Time Sheet gravel yd 20.00 ft 6.00% 0.0110 0.27 min 1 ! : j 1 1 � • 1 i � - Proposed Development Stormwater Runotf Calculations: � Precipitation: 2yr 24-hour: 2 in ' 10yr 24-haur: 2.9 in , 25yr 24-hour: 3.4 in 50yr 24-hour: 3.4 in � 100yr 24-hour: 3.9 in � ; SWdeveloped Event Summary: BasinlD Peak Q Peak T Peak Vol Area Method Raintype Event � ------- (cfs) (hrs) (ac-ft} ac /Loss SWdeveloped 1.37 8.00 0.8632 6.21 SBUH/SCS TYPEIA 100 yr .� Drainage Area: SWdeveloped � Hyd Method: SBUH Hyd Loss Method: SCS CN Number Peak Factor: 484.00 SCS Abs: 0.20 Storm Dur: 24.00 hrs Intv: 10.00 min � Area CN TC j Pervious 5.7190 ac 73.64 0.56 hrs Impervious 0.4875 ac 98.00 0.01 hrs � Total 6.2065 ac I Supporting Data: , Pervious CN Data: Grass Lawn 74.00 3.6500 ac � Forest 73.00 2.0690 ac Impervious CN Data: Plaza and Path 98.00 0.4875 ac � Pervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Shallow Forest 200.00 ft 8.00% 3.0000 3.93 min Sheet upper park area 300.00 ft 2.00% 0.1500 29.85 min � Impervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Sheet across plaza 20.00 ft 2.00% 0.0110 0.42 min � 1 Conclusion: J Using the 1990 King County SurFace Water Design Manual, flow control is not required when there is less than a 0.5cfs increase from existing conditions to developed conditions for the 100yr peak 24-hour storm. The existing peak flow rate, Q,00, for the � Northwest Basin is 1.1 cfs. The proposed development would increase this flow rate to 1.37cfs; an increase of 0.27cfs. This increase is less than 0.5cfs which means Flow � Control is not required for this basin. � � � � J � } Conveyance Calculations � Conveyance Map � Basin Analysis for 25yr peak fiowrate • Conveyance and Backwater spreadsheet , II � ,� � � � ..J � e �.3 J 2 J T n � ' ' � ' � � I t T � , I I -, NE 3RD PLACE � ._ ._ . �I � � _ - , _ , _ � � , � � '^r � _ - - - _ '- _:� � -_ � ' , � -� , - - - _ � _ ---- - _ - �, . } (, /. 'i -- -- ---- . . _ _. . - _ . . ( �� \ ` � -- �. ,,.� r E , ,, `' , ' } r �� ; t- � - - , Y ' ; 'i j. t�' /. � � _ - '� .. � �� ' �; � ( � ��' �` f - ��\ l ; I � ` '/ `, �1- -.. CB 1. -Q��1�� '� ; �' - - i%� '� . � - - - +-_ - � z� `� �. �- .,� ,_J/` � _ __- - \' �` -1_ " ' _ � - ' ��` �,:��. I � � . � j� B�� l Z, � a. �i,,`'�. � �\\ , � - .602 1`,� � o i .�-� ' �. �_ � . � j � re �-J�- � '------- -- — --_ - ��- -- ' . .L,r ;' `__ .�-� '�� +�{ - y •. ' . < ! . .. • � i �11 ( 'i � ' � � � "��---� ./ � ; � �} i `� ; ; 803 --- �`. �� ; ! - � - -- i� ,' . � � -� ,\ ` J ' � CB �3 ! --- � � i ` � , j I t '�' 1� ,,1 �� i � . / , , �y 3 1 �. I , ,; , � � ;.' � � I ;� � � . , l' - ,'` i ` ' ; 'i ----- - � _ �.� , � : , � � . , � � , .- r' � \� , — y% _ __ _ _._ - _ __ . i � _�1 � r ',.:.= � -, � '� t ; `; -.�__ _�-% K` _� � - .F, � �- -- - - -�- `- - -- ' ---__.._ - - —� N� ; J t�; : J t'` '�,� � � ' , r , r� ,- . , ; - � '' t\\• ` � i i' � ` �--- -- - ` ', '��^ �!_ - / � `� � ' J l �` �, ' � '.' ,`-.��.... ' � i ! i �' .r� '�� --�, \\ i ��_...., _I!1 J 1 c:i \\. , �.%o �� i� / %� . � / �� --- t ^;~ \j / �f'I/l/ l`'. /` 1 f" l��, -� / ------ / ~ I ` D � � ;• ��rf,. �� , --� �� ` , ! , , , ; /' j = , - , , . ; ; ; { ; c �. ., . . , . � -t _ : , � , — � .. - - :; � � , - -- , �._- - _ . \ , Ju,;' � z: _ ; � j` �,, ¢ i o z � � � � � � s• CITY OF SavF NEW PARK AT NE 3RD COURT oz/2a/zooe � � `r � � AND UNION AVENUE NE � � ,�,„�,�`,�",�,.�F",�"" s RENTON � � � �.,� "°''''+°"°"°',"'a' "r F`"L sc''`E CONVEYANCE LAYOUT cm.�sx�-asu .(�oq ut-+i.+u w«w,u.a. IF Nar o►/E.+a+ SGLE IipCq201NG1Y r r � � � � � � • Precipitation: 2yr 24-hour: 2 in 10yr 24-hour: 2.9 in -, 25yr 24-hour: 3.4 in : � B01 Event Summary: BasinlD Peak Q Peak T Peak Vol Area Method Raintype Event � ------- (cfs) (hrs) (ac-ft) ac /l.oss 601 0.14 7.83 0.0551 0.30 SBUH/SCS TYPEIA 25 yr 1 - Drainage Area: 601 � Hyd Method: SBUH Hyd Loss Method: SCS CN Number Peak Factor: 484.00 SCS Abs: 0.20 Storm Dur: 24.00 hrs Intv: 10.00 min � Area CN TC Pervious 0.1722 ac 78.74 0.29 hrs Impervious 0.1288 ac 98.00 0.01 hrs Total 0.3010 ac I� � Supporting Data: I Pervious CN Data: Grass Lawn 74.00 0.1042 ac � Playground 86.00 0.0680 ac Impervious CN Data: Plaza and Path 98.00 0.1288 ac Pervious TC Data: � Flow type: Description: Length: Slope: Coeff: Travel Time Sheet grass areas 30.00 ft 2.00% 024Q0 6.89 min Sheet playground 30.00 ft 2.00% 0.4100 10.57 min � Impervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Sheet across plaza 40.00 ft 2.00% 0.0110 0.74 min � Summary: � The 25yr Peak Flow Rate is QB01= 0.14cfs. � � J - , � J I t 1 � � � 1 � � Precipitation: 2yr 24-hour: 2 in 10yr 24-hour: 2.9 in - 25yr 24-hour. 3.4 in 602 Event Summary: � BasinlD Peak Q Peak T Peak Vol Area , Method Raintype Event ------- (cfs) (hrs) (ac-ft) ac /Loss B02 0.07 7 83 0.0291 0.17 SBUH/SCS TYPEIA 25 vr Drainage Area: B02 � Hyd Method: SBUH Hyd Loss Method: SCS CN Number Peak Factor: 484.00 SCS Abs: 0.20 Storm Dur: 24.00 hrs Intv: 10.00 min � Area � C N TC Pervious 0.0948 ac 74.00 0.34 hrs Impervious 0.0754 ac 98 00 0.02 hrs Total 0.1702 ac � Supporting Data: Pervious CN Data: Grass Lawn 74.00 0.0948 ac � Playground 86.00 0.0000 ac Impervious CN Data: Ptaza and Path 98.00 0.0754 ac Pervious TC Data: t Flow type: Description: Length: Slope: Coeff: Travel Time 4 Sheet grass areas 45.00 ft 2.00% 0.2400 9.53 min Sheet playground 30.00 ft 2.00% 0.4100 10.57 min � Impervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Sheet across plaza 65.00 ft 2 00°%0 0.01 10 1 09 m in � Summary: 1 The 25yr Peak Flow Rate is QB02= 0.07cfs. 1 1 . � 1 l f t � � � ' � � • Precipitation: 2yr 24-hour: 2 in 10yr 24-hour: 2.9 in � 25yr 24-hour: 3.4 in : , � � B03 Event Summary: �" BasinlD Peak Q Peak T Peak.Vol Area Method Raintype Event ------ (cfs) (hrs) (ac-ft) ac /�oss 603 0.05 8.00 0.0207 0.12 SBUH/SCS TYPEIA 25 yr Drainage Area: B03 � Hyd Method: SBUH Hyd Loss Method: SCS CN Number ,; Peak Factor. 484.00 SCS Abs: 0.20 Storm Dur: 24.00 hrs � Intv: 10.00 min �� Area CN TC Pervious 0.1074 ac 84.50 0.32 hrs -�' Impervious 0.0145 ac 98.00 0.01 hrs Total 0_1219 ac � Supporting Data: " :� Pervious CN Data: Grass Lawn 74.00 0.0134 ac � Playground 86.00 0.0940 ac Impervious CN Data: " Plaza and Path 98.00 0.0145 ac Pervious TC Data: t' Flow type: Description: Length: Slope: Coeff: Travel Time ;,�; Sheet grass areas 10.00 ft 4.00% 0.2400 2.17 min Sheet playground 55.00 ft 2.00% 0.4100 17.17 min f� Impervious TC Data: � Flow type: Description: Length: Slope: Coeff: Travel Time Sheet across plaza 20.00 ft 2.00% 0.0110 0.42 min � Summary: � The 25yr Peak Flow Rate is QBo3= 0.05cfs. � • . � � . , . � � f f ! t � � Pro-ec New Park in Rento Shee� _ � I Jab M 105166 0 of , - . --- By MOE Date 02;24/05 l J _-.. '. -- .. . - Backwater Calculations for 25yr 24-hour Des�gn Storm Event per King County Surtace Water Design Manual � _ 1 2 3 4 S 6 7 6 9 10 11 12 13 14 15 16 17 18 79 20 Outlet Inlet Proportio 8arrel Tad Entrance OuUet Inlet Approach Head Q Pipe Invert Invert nal V design Barrel Barrel Vebcity Water Fnction �r.trance Head Exit Head Control Control Control VebcBy Bend Head Junction VJater Rim Rim EL Req'd Pi e Se men[ desi n Q(uM pJQfull Len th size n Elevation Elevalion d/D Ratio Velocity V full fVs fUs Area Velocity Head Elev Loss HGL EL Ke Loss Loss Elev HW/O Elev Elev Head K, Loss K, Head Loss Elevation Elevation to HGL Ciearance OK� from to ds c(s ft in ft ft ft^2 fVs ft fl ft ft ft ft ft ft ft n n ry ft ft ft OutiaA WYE 026 1 712 0.15 229 8 0.012 402 06 405.96 0.26 0.72 4.90 3.51 0.349 0 74 0 01 40256 0 087 402 65 0.50 0.004 0 008 402.66 0.1 406 03 406_03 0 240 0.00 0 0 0 0000 40579 406.96 1.17 0 O� WYE C63 OAS 1.6596 0 03 45 6 0.012 405 96 409 3 0 11 0 43 8.45 3 60 0.196 0 24 0.00 406 21 0 003 40E 27 0 50 OA00 OA01 406.21 0.1 409 35 409.35 0 270 0 40 0 00223518t O P3833486 OA000 a09A8 411 1 2 02 0 OK � 1/Vl'E C82 021 1 J086 0.12 79 8 0.012 405 96 407.3 0.23 0.67 4.89 327 0 349 0 60 0.01 406.46 0 020 405.4& 0.50 0 003 0 006 406.49 0.1 407 37 407 37 0 390 0.00 0 0 0 0000 406 98 410 1 3 12 0 OK C82 C81 0.14 0.8494 0 16 36 6 0 012 407 3 408 0 27 0 73 4.33 3 17 0 196 0 70 0 01 407 63 0 07 B 40?65 0 50 0 004 0 008 407.66 0.1 408A5 408 05 0 000 OAO 0 0 OA000 4C�A5 409.8 1]5 0 OK . 1 i ��yr Storm 61a�n Backwater Ocalc r's ,�q;��,i6 � � � � � � � A endix C pp � • Geotechnical Report "t ; � �, J - - i� , I�� ,i �� J � � . � � � . . . � 3 3 � . : ; . : ; . � J � r i Geotechnical Repor � Heather powns Park Developmen� Renton, Washingtor � October 10, 200� � I 7 � , ,,: � -r� t , � � + • • J -� - , y� � , .tlF��iF�'�.ti',�',Ft I(MO��. E1'�V1Nd1tYErNTAt�OMeULTAHTO' ' � � . , . . . . _ .. ... . . - . ' I ��t Shnnnun & R'iLcon. nur mi.r.cion is�u Gc u prugrc�.ssi�•c�, �rell- 1 utruru,Sed prufe.csiunn!c•rnt.rn/tin,S firm irr 1h��Jield.�nj t'l14lRPL'I'lll�( cind applied currli.,rience.c. Our,Suu!i.� to pciJrn-�n nttr sc�r�•ires' l uit/r lhr lri,�krs!dc�ri�e uf'p�n%a.cciunulisnr��•ill�rhr��cnn.cid�vnli�nr I Jtu lhc�hc�sl n�lYrr.str njlhe 1�td�/rc•.otu'c fir�irls.urrd r,ur�vnpL»'ees. � � . , ll � . i � � Submitted To: Mr. Jim Brennan J.A. Brennan Associates, PLLC � 100 South King Street, Suite 200 Seattie, Washington 98104 � ; By: Shanr�n 8 Wilson, Inc. - � � : = 400 N 34�"Street, Suite 100 � Seattle, Washington 98103 21-1-20373-001 � f � 1 � SHANNON�WILSON.INC. � TABLE OF CONTENTS � � Page 1.0 INTRODUCTION .................:...............................................................................................1 � 1.1 Purpose.......................................................................................................................1 1.2 Scope of Work............................................................................................................l 2.0 SITE AND PROJECT DESCRIPTION.................................................................................1 ' � 3.0 SUBSURFACE EXPLOR.ATION PROGRAM ...................2 '� 1 4.0 GEOLOGY AND SUBSURFACE CONDITIONS ..............................................................2 I 4.1 Regional Geology.......................................................................................................2 4.2 Subsurface Conditions ...............................................................................................3 � 4.3 Groundwater Conditions.................................................................. ......................3 5.0 ENGINEERING CONCLUSIONS AND RECOMMENDATION-S........:...........................4 � 5.1 General.:.....................................................................................................................4 5.2 Foundation Design.....................................................................................................4 5.3 Estimated Settlement..................................................................................................4 � , 5.4 Lateral Earth Pressures...............................................................................................5 5.5 Lateral Resistance......................................................................................................5 � 5.6 Floor Slabs .................................................................................................................6 5.7 Drainage.....................................................................................................................6 5.8 Earthwork...................................................................................................................7 5.8.1 Site Preparation and General Excavation....................................................7 � 5.8.2 Temporary Groundwater Control................................................................7 5.8.3 Fill Placement, Compaction, and Use of On-site Soils ...............................5 � 5.8.4 Wet Weather Earthwork..............................................................................9 5.8.5 Erosion Control..........................................................................................10 6.0 CONSTRUCTION CONSIDERATIONS...........................................................................10 l 6.1 Obstructions.............................................................................................................10 6.2 Loose Test Pit Backfill.............................................................................................10 , 7.0 LIMITATIONS....................................................................................................................10 � 8.0 REFERENCES.....................................................................................................................13 � 3 3 . . , S • , . � 21-1-20373-001-R1/wpiLKDLORI DOHERTY 21-1-20373-001 � ' r T � � SHANNON F�WILSON,INC. TABLE OF CONTENTS (cont.) � LIST OF FIGURES � Figure No. 1 Vicinity M ap � 2 Site and Exploration Plan , � � � LIST OF APPENDICES Appendix 1 A -Field Explorations - li B Important Information About Your Geotechnical Report J J � l J . � � � � � � � � . . � � - - : . : ; . . � � � 21-1-20373-001-RI/ ucn 21-1-20373-041 � � ii � � I SHANNON F�WILSON,INC. IGEOTECHNICAL REPORT HEATHER DOWNS PARK DEVELOPMENT IRENTON, WASHINGTON I1.0 INTRODUCTION I1.1 Purpose This report presents the results of subsurface explorations and geotechnical engineering studies I for the Heather powns Park Development site located in Renton, Washington. The purpose of our�geotechnical studies was to evaluate subsurface conditions in order to formulate engineering recomrnendations for use in the design and construction of the proposed project. Our services � wer� provided in accordance with our proposal, dated May 31, 2005, and authorized by , Mr. James A. Brennan at J.A. Brennan Associates, Inc. on July 19, 2005. I 1.2 Sco e of Work P ( Our scope of work for this project included the following: ' � ► Identifying and reviewing existing subsurface information in the general vicinity. ► Overseeing and sampling excavation of three test pits. ► Performing laboratory tests. 1 ► Preparing a site and exploration plan and logs of test pits. � ► Conducting engineering analyses. ► Summarizing our conclusions and recommendations in this report. I 2.0 SITE AND PROJECT DESCRIPTION IThe proposed Heather powns Pazk Development project, as shown in the Vicinity Map, Figure 1, is situated southwest of the intersection of NE 3`� Court and Union Avenue in the City � of Renton. We understand that the site was formerly residential property and the majority of the site is cunently overgrown with trees and brush, including dense thickets of blackberries. Based � on the proposed site plan surveyed by Penhallegon Associates Consulting Engineers, Inc. (PACE), on September 13, 2005, the area of concern at the site measures about 250 feet by 1 300 feet. In general, the ground surface across the site slopes gently from elevation 414 feet on 3 , � �1-�-203�3-001-RliwpiLKDLORI DOHER7'Y 21-1-20373-001 � 1 , � � �i � SHA�INON F�WILS�N. IN�� [ 3 r-, Y►ie aout}�i end io about elevati�i�� 408 teet on the north end T}iese elevatiuns are in tenns of the � : � North American Vertical Datum of 1988 (NAVD88). ��i The proposed developed area of the park will cover about 75,000 square feet. The buildings at , " the site include a restroom facility and a picnic shelter. We understand that these structures will ' be constructed on slabs-on-grade with shallow perimeter footings. The site will also include i•; paved parking lots, playground areas, and planters and landscape areas, as shown on the Site and Exploration Plan, Figure 2. � f� 3.0 SUBSURFACE EXPLORATION PROGRAM � s - To generally characterize subsurface conditions in the vicinity of the proposed structures, three � test pits were excavated and sampled at the approximate locations shown in Figure 2. The test _ pits are designated TP-1 through TP-3. A des�ription of the methods and procedures used for locating, excavating, and sampling the test pits is included in Appendix A. The logs of the test � pits are also included in Appendix A as Figures A-2 fhrough A-4. t�3 4.0 GEOLOGY AND SUBSURFACE CONDITIONS � 4.1 Regional Geology The project site is located in the central portion of the Puget Lowland, an elongated topographic � and structural depression bordered by the Cascade Ivlountains on the east and the Olympic mountains on the west. Low-rolling relief, with some deeply cut ravines and broad valleys, � characterizes this lowland. In general, the ground surface elevation of the project site is within 410 feet above sea level. � Geologists generally agree that the Puget Sound area was subjected to six or more major glaciations during the Pleistocene Epoch (2 million years ago to about 10,000 years ago), which � filled the Puget Lowland to significant depths with a complex sequence of glacial and non- glacial sediments. Ice for these glacial events originated in the coastal mountains of the � Vancouver Range of British Columbia. The maximum southward advance of the ice was about halfway between Olympia and Centralia (about 80 miles south of Seattle). During the most recent ice coverage of the central Puget Lowland (Vashon Stade of Fraser Glaciation), the � ; . ; . . ; . . ; . � 21-1-20373-001-RIlw LKD 21-1-20373-001 � � 2 ♦ � � � SHANNON F�WILSON,INC. � thickness of ice is estimated to have been about 3,000 feet in the project area. The last ice '' l covering the project area receded about 13,500 years ago. � The distribution of sediments in the Puget Lowland is complex, because each glacial adva: ' deposited new sediments and partially eroded previous sediments. During the intervening � interglacial episodes, the complete or partial erosion or the reworking of some deposits, as .� � : as the local deposition of other sediments, furkher complicated the geologic setting. I4.2 Subsurface Conditions The results of our subsurface explorations, TP-1 through TP-3, indicate the general subsurface Iconditions across the proposed park site are underlain by a varying thickness of fill material- overlying native glacial till. Fill was not encountered in TP-3. The fill material, to a depth of 2 Ito 3%2 feet, generally consists of loose to medium dense, slightly gravelly, silty sands. The test pit lacations were deliberately chosen to=avoid excavating within future building footprints and ( adjacent to the site of the demolished former residence. Demolition debris was not encountered �n the fill layer dunng excavation, but may be encountered dunng earthwork activities. Large I concentrations of demolition debris were not encountered during exploration. However, due to the history of the site, which includes two residences that were demolished, it is likely that debris concentrations in the fill may be encountered across the site. The debris may include abandoned Ifoundations, concrete and asphalt rubble, metal, bricks, wood, tree stumps, and other organic and construction debris. Underlying this surficial fill layer, the soils consist of loose to medium Idense, slightly gravelly, silty sand (weathered glacial till) approximately 2 to 3 feet thick � • overlying a dense to very dense, concrete-like mixture of silt, gravel, sand, and clay(glacial till). ( Cobbles and up to 3-foot-diameter boulders are commonly included in the matrix of the glacial till, though none were encountered during our explorations. I4.3 Groundwater Conditions Groundwater was not observed in the test pits during excavation. However, we observed iron � oxide stains on partings and lenses, which suggest fluctuating groundwater conditions. Therefore, we anticipate that seasonal perched groundwater conditions may be present. ' 1 I2]-1-203 73-001-RI/wpiLKD 21-1-203 73-001 � 3 . �j � ^? SHANNON F�WILSON.INC. I i � � 5.0 ENGINEERING CONCLUSIONS AND RECOMhtENDATIONS 5.1 General � Based on our cunent understanding of the proposed park development project as described � previously, and on the results of our geotechnical studies, we developed the following � recommendations for foundation design. The following sections describe these recommendations and provide additional recommendations for site preparation, excavation, fill � placement and compaction, use of on-site soil, and wet weather earthwork. 5.2 Foundation Design ' � In our opinion, the proposed structures could be supported on conventional spread footings or on slab-on-grades with thickened edges. However, because of the depth of relatively loose soils that � underlie the proposed struetures, we recommend the foundation areas be overexcavated to competent soil (up to about 2 feet) and replaced with compacted structural fill. For footings , bearing on densely compacted structural fill or dense, unweathered, native soil, we recommend using an allowable bearing pressure of 2,040 pounds per square foot (ps�. Continuous wall , � footings should have a minimum width of 18 inches and column footings should have a �� minimum width of 24 inches. All footings should be embedded at least 18 inches below the � �lowest adjacent exterior grade. The allowable bearing pressure may be increased by one-third for short-term wind or seismic loads � We recommend that each footing/slab excavation be evaluated by a qualified geotechnical engineer or representative during construction to confirm the presence of competent bearing soil � and to determine that all unsuitable fill and organic material have been removed. 5.3 Estimated Settlement � Foundations designed and constructed as recommended in this report are estimated to undergo � total settlement of less than % inch. Owing to the variation of footing loads and soil conditions, differential settlements are estimated to be about one-half of the total settlements between heavily loaded and lightly loaded footings or along a continuous footing for a distance of � approximately 20 feet. It is anticipated that the majority of the estimated settlements would occur simultaneously as the loads are applied. � 3 � � 4 l�1�LO / �00 1 21-1-20373-001•Rl/wp/LKD 3 3 � 4 f { ♦1 jj I I � SHANNON F�WILSON,INC. i L � 5.4 Lateral Earth Pressures 'j The lateral pressures against a buried wall are dependent upon many factors, including method of F� backfill placement and degree of compaction, backfill slope, surcharges, the type of backfill soil _ � and native soils, drainage, and whether or not the wall can yield or deflect laterally or rotate at ' � the top after or during placement of backfill. If the wall is free to yield at the top an amount � i �j equal to approximately 0.001 times the height of the wall, the soil pressures will be (ess (active i case) than if this amount of movement is not allowed due to stiffness or resistance of the wall �! � (at-rest condition). ', r� Rigid, buried walls should be designed to resist an "at-rest" lateral earth pressure based on an ' Z � equivalent fluid unit weight of 55 pounds per cubic foot(pc�. Walls allowed to deflect laterally ;, or rotate at the top should be designed using an active lateral pressure equivalent to a fluid unit '� ;,� weight of 35 pcf. These values should be increased by 1 pcf for each degree of upward inclination of the backslope above the wall. The above pressures are for permanent walls and � assume that proper drainage is provided behind the walls so there is no buildup of hydrostatic !, pressures. Backfill should not be placed behind a wall until the wall is capable of supporting '� � lateral pressures. � 5.5 Lateral Resistance ' Lateral loads, due to unbalanced lateral earth pressures, wind, or seismic forces, would be � resisted by base friction and passive earth pressure against buried portions of the structure. We recommend passive earth pressures in dense, silty, gravelly sands or compacted structural fill be determined using an equivalent fluid density of 200 pcf. This value assumes that footings are � founded at least 18 inches below the lowest adjacent grade and placed within neat excavations. The above value includes a factor-of-safety of l.5. � We recommend that a coefficient of friction between mass concrete and dense native ground and � structural fill of 0.40 be used, with an appropriate factor-of-safety to calculate the resistance to sliding. � - � � ' : - . . ; . . - � 21-1-20373-001-R1/w uco 21-1-20373-001 a � 5 1 i ) � SHANNON F�WILSON,INC. � 5.6 Floor Slabs We recommend that all floor slabs be supported be densely compacted structural fill or dense � native soil. If unanticipated loose, soft, or unsuitable soil is encountered in the floor subgrade preparation, it should be overexcavated and replaced with compacted structural fill. � We recommend placing a capillary break consisting of at least 4 inches of washed pea gravel or � S/a-inch minus crushed gravel beneath the floor slabs. The washed pea gravel will provide � positive leveling and a more uniform surface than the native soil or structural fill and will also act as a capillary break. For heated spaces or spaces with floor coverings, a vapor barrier n, consisting of plastic sheeting or equivalent should be placed on top of the washed pea gravel. As j an alternative, the capillary break may consist of a 2-inch layer of washed gravel beneath a 2-inch layer of crushed rock. The crushed rock should be compacted with a vibrating plate � compactor to provide a working surface for concrete placement. � We recommend using a modulus of subgrade reaction, k, of 250 pounds per cubic inch (pci) tc�r designing floor slabs-on-grade. This design recommendation assumes that slabs-on-grade are � constructed in accordance with the above recommendations. 5.7 Drainage . � Groundwater was not encountered in the subsurface explorations performed at the site. Therefore, the proposed structures will not require a permanent subdrain system. � To control surface water, rovisions should be made to direct it awa from structures and revent P Y P � it from seeping into the ground adjacent to structures or excavations. The ground surface should be sloped away, and surface and downspout water should not be introduced into site backfill. Surface water should be collected in catch basins and along with downspout water, should be � conveyed in a non-perforated pipe(tightline) into an approved discharge point. � Except as otherwise designed and/or specifically covered in the contract, the Contractor should be made responsible for control of all ground and surface water encountered during construction. � In this regard, sloping, ditching, pumping from sumps, providing trench drains, dewatering, and other measures should be employed as necessary to permit proper completion of the work� , � ; • . s • . � 21-1•20J7J-001-R1lwp/LKD 21-1-20373-001 � 6 � 1 SHANNON�WILSON,INC. 5.8 Earthwork � 5.8.1 Site Preparation and General Excavation � Site preparation for excavation and fill placement should commence by collecting and ' diverting all sources of surface water flow into temporary storm drainage facilities. Each � building site should be cleared of all trees, brush, and other vegetation, and should then be �- grubbed of large roots and stripped of su�cial soil containing significant amounts of roots or � other objectionable debris (see Section 4.2) and organic material. The material should not be mixed with soil that may be used as structural fill. Abandoned utility pipes should be plugged or removed so they do not provide a conduit for water that could cause saturation and stability � problems. � Based on the subsurface conditions encountered in the explorations, we anticipate that the . • excavations at the site could be made using conventional excavating equipment such as dozers, � front-end loaders, rubber-tired backhoes, or tracked hydraulic excavators. Cobbles and possibly boulders could be encountered in dense glacial soil, and the Contractor should anticipate their presence. We recommend that all loose fill soil in the building footprint be removed. Native � ground should be encountered from %Z to 2 feet below existing ground surface. � Where fills are made on a slope, the native ground upon which the fill is placed should be terraced to key the fill into the slope. We recommend that the height of each tenace not exceed � 2 feet. Following stripping, grubbing, and excavation to obtain desired grades or exposed native � ground, a geotechnical engineer or engineer's representative should evaluate the density of the exposed surface. Should the presence of loose zones be revealed, they should either be remo� � and replaced with structural fill, or dried or moistened as required (including scarifying, mixin and/or aeration), reworked, and adequately compacted until a dense, unyielding soil mass i� produced. � 5.8.2 Temporary Groundwater Control � Groundwater was not encountered in the explorations performed at the site. If the earthwork occurs during the wet season, perched groundwater could be encountered. In our � opinion, perched groundwater that may seep into the excavation and rainwater that falls into the � 3 J21-1-20J73-001-R1rwp:LKD 21-1-20373-001 � 7 J I �� ,.� � SHANNON F�WILSON,INCe � 5.8.4 Wet Weather Earthwork Wet weather generally begins about mid-October and continues through about May, i � although rainy periods may occur at any time of year. Some of the soil at the site contains sufficient silts and fines to produce an unstable mixture when wet. Such soils are susceptible to changes in water content, and they tend to become unstable and difficult or impossible to ;,1 compact if their moisture content significantly exceeds the optimum. If earthwork at the site continues into the wet season, or if wet conditions are encountered, we recommend the �!, � following: ��I � ► The ground surface in and surrounding the construction area should be sloped as much as ' possibl� to promote runoff of precipitation away from work areas and to prevent ponding of water. " � . ► Work areas or slopes should be covered with plastic. The use of sloping, ditching, sumps, dewatering, and other measures should be employed a�necessary to permit proper - completion of the work. - � ► Earthwork should be accomplished in small sections to minimize exposure to wet ; conditions. That is, each section should be small enough so that the removal of ', � unsuitable soils and placement and compaction of clean structural fill can be accomplished on the same day. The size of construction equipment may have to be limited to prevent soil disturbance. It may be necessary to excavate soils with a backhoe, � or equivalent, located so that equipment does noC traffic over the excavated area. Thus, subgrade disturbance caused by equipment traffic will be minimized. � ► Fill material should consist of clean, well-graded, pit-run sand and gravel soils, of which { not more than 5 percent fines by dry weight passes the No. 200 mesh sieve, based on wet- sieving the fraction passmg the '/+-inch mesh sieve. The gravel content should range from � between 20 to 60 percent retained on a No. 4 mesh sieve. The fines should be nonplastic. ► No soil should be left uncompacted and exposed to moisture. A smooth-drum vibratory roller, or equivalent, should roll the surface to seal out as mueh water as possible. � ► In-place soils or fill soils that become wet and unstable andlor too wet to suitably compact should be removed and replaced with clean, granular soil (see part 4). � ► Excavation and placement of structural fill material should be observed on a full-time basis by a geotechnical engineer(or representative) experienced in earthwork to determine that all work is being accomplished in accordance with the project � specifications and our recommendations. ► Grading and earthwork should not be accomplished during periods of heavy, continuous , � rainfal l. . _ ' , 3 I . . . ; S . ; I �, � II 21-1-20373-001-RI/wp/LKD 21-1-203 73-001 9 �t`. � '• � 1 � SHANNON�WILSON. INC. � We suggest that these recommendat►ons for wet �veather earthwork be included in the contract specifications. � 5.8.5 Erosion Control The Contractor should employ proper erosion control measures during construction, , � especially if construction takes place during wet weather. Covering work areas, soil stockpiles, �I or slopes with plastic, sandbags, sumps, and other measures should be employed as necessary to permit proper completion of the work. Bales of straw, geotextile silt fences, and drain inlet � sediment screens/collection systems should be appropriately located to control soil movement � and erosion. ] 6.0 CONSTRUCTION CONSIDERATIONS 'I i 6.1 Obstructions � � ' , Unanticipated conditions are commonly encountered and cannot be fully determined by merely taking soil samples or making explorations. Although not encountered in the explorations, lcobbles and boulders are commonly found in glacial soils and should be anticipated at the site. These obstructions would im.pact excavations. Such unexpected conditions frequently require j that additional expenditures be made to achieve a properly constructed project. Some � contingency fund is recommended to accommodate such potential extra costs. j6.2 Loose Test P�t Backfill ' Test pits dug to explore the site were loosely backfilled. If a test pit falls in an area that will not , be overexcavated below the bottom of the test pit, the loose soil should be removed�during construction and replaced with compacted structural fill. 1 7.0 LIMITATIONS � This report was prepared for the exclusive use of J.A. Brennan Associates, Inc. and other � members of their design team to assist in the design and construction of the Heather powns Park ! � ; � • � 1 � 21-1-20373-001-Rl/w �Ko 21-1-20373-001 a � la � � � 1 � SHANNON F�VNILSON,INC. � Development project. The analyses, conclusions, and recommendations contained in this report are based on site conditions as they presently exist and on the site and project descriptions as presented herein. We should be notified if differences are identified. We assume that the � exploratory test borings and retrieved samples are representative of the subsurface conditions throughout the site; i.e., the subsurface conditions everywhere are not significantly different from � those disclosed by the explorations. During construction, if subsurface conditions different from those described in this report are observed or appear to be present during construction, we should J be advised at once so that we can review these conditions and reconsider our recommendations, where necessary. If conditions have changed due to natural causes or construction operations at � or adjacent to the site, it is recommended that this report be reviewed to determine the applicability of the conclusions and recommendations considering the changed conditions and time lapse. J Within the limitations of the scope, schedule, and budget, the analyses, conclusions, and recommendations presented in this report were prepared in accordance with generally accepted � professional geotechnical engineering principles and practice in this area at the time this report � was prepared. We make no other wananty, either express or implied. These conclusions and recommendations were based on our understanding of the project as described in this report and on site conditions as observed at the time of the exploration. • � � The sco e of our services for this ro'ect did not include an environmental assessment or P P J Y � evaluation regarding the presence or absence of wetlands or hazardous or toxic materials in the soil, surface water, groundwater, or air, on or below or around the site, or for the evaluation or � disposal of contaminated soils or groundwater, should any be encountered. However, we will be glad to provide such services on request � � .� � � ��-�-zo3�3-ooi-Ri;,.� ;iKv 21-1-20373-001 P � 11 k s. � % I � SHANNON�WILSON,INC. � � Shannon & Wilson has prepared and included in Appendix B, "Important Information About ' � Your Geotechnical Report," to assist you and others in understanding the use and limitations of our reports. � SHANNON & WILSON, INC. � __ � J e A. Mat E ineer � i: � � �U$?► � o� �O� � N- � N . x '� � � � � 1D��0�5 lox,�.� � ��s �nsro � Thomas M. Gurtowski, P.E. . . Vice President � JXM;TMG/met � � � , ' � n � 21-I-20373-001-R1/wp/LIfD 21-1-2�373—��1 i 12 � a i • � i � . � SHANNON�WILSON,INC. : : � S.0 REFERENCES � American Society for Testing and Materials (ASTM), 2004, Annual book of standards, Construction, v. 4.08, Soil and rock (I): D 420— D 4914: West Conshohocken, Pa. � Washington State Department of Transportation and American Public Works Association, 2004, Standard specifications for road, bridge, and municipal construction (M41-10). J �� ! J � � � J � � � � � � . � - � 3 � 21-i-20373-001•R l/wp/LKD 21-1-203 73-001 � 13 --�Z�� O � 3S AY H1Bvi� AY IN •-.._.._.._.._..-.. ' � o. T ' p .-' C�j � � �r ;t, ti�� 3S H�.IA M16►f' � ��-�. � c d I � �; ��'� 3S ie� .. Hie� '� y S�1Y a � � ' ' O L1. �Av `^ �3S l'�a'� ��. IG�� i� 16p� " y; � k"�a a N � �A� I_. 3S � _ -- !+ '$la � _, . 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L� _ R�STROOM � �� . .; � , � � __ : � - ' � �� .��rl; :. ,:i� T -� � �:r i �„�..� { � -; :i S i � i ,,. � � _ . �- � ' � _y � , ,. � � � � __ -__. . , F , .. _ _ _ ,._ _ . i ,; " -� � � , ., . , � , , , i _ __ _ _- �- _ � � � ,,. - _ - � .,� ,� � . =-- -- __ , ,= �_ .. �,, � � � _ � � o so �o0 � � Q Scale in Feet LL Heather powns Park Development � LEGEND City of Renton � � 3 TP-1 � Test Pit Designation and 3 Renton, WaShington Approximate Locati�on � , : . . . � � No� SITE AND EXPLORATION PLAN �y Figure adapted from electronic files, "survey.dwg' � "hdp �rading.dwg",and "hdp-site-layout-dh2.dwg" October 2005 21-1-20373-001 r� � provided by client 9-13-05. SHANNON b WILSON, (NC. F�G, 2 J � CiwMrJrYdl�nd Emkorvnanttl Co�nultanb iL � -. �, a. � i 1 : :� . SHANNON F�WILSON,INC. : ; � r� 1. � �1 '.� � . y - - � � APPENDIX A � FIELD EXPLORATIONS • � � �� . II, � � .:l - � ; : ' � � � � • � � � _ . , � � 21-1-20373-001 r .M r 1 �. {.� 1 �� SHANNON F�WILSON,INC. ' APPENDIX A _ ; .i FIELD EXPLORATIONS 1 � TABLE OF CONTENTS � � � Page � � A.1 GENERAL.......................................................................................................................A-1 , ,,� A.2 TEST PITS.......................................................................................................................A-1 � ; - -� LIST OF FIGURES .� Figure No. ] A-1 Unified Soil Classification and Log Key(2 sheets) A-2 Log of Test Pit TP-1 � A-3 Log of Test Pit TP-2 A-4 Log of Test Pit TP-3 � � � � � � � � . � . � � 21-1-2037)-001-Rl-AA/wpILKD 21-1-20373-001 A-i