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Home My WebLink AboutMisc- TECHNICAL INFORMATION REPORT CENTRAL IS \ RECEIVED MAR -9 2015 CITY OF RENTON PLANNING DIVISION NDS SHORT PLAT 7TH STREET / \ \ The Concept Group 4701 SW Admiral Way, Suite 353 • Seattle, WA 98116 • (206) 446-1291 Land Development & Civil Engineering Consultants CENTRAL ISLANDS SHORT PLAT 3413 NE 7TH STREET RENTON, WA Revisions: Original -November 2014 pt Revision -March 2015 I certify that this technical information report and all attachments were prepared either by me or my technical staff working directly under my supervision. 03/3/2016 THE CONCEPT GROUP Table of Contents SECTIO:'< 1: PROJECT OVERVIEW .................................•..•.••..•....•.•..•.....•.•..•..•......••.••......••.••....•..................•.••..... 1 SITE INFC)RMATlON................................................................... . .................................. 1 DRA(NAGE BAS(N ............................................................................................................................................... 4 Son.s fNFORMATION .................................................. 5 SECTIO\. 2: CO:\DITI(>NS AND Rt:QlllREl\11<:NTS .................................................................................................... 6 DES(GN REQU(REMENTS ..................................................................................................................................... 6 SECTION 3: 0FFSITE A1'ALYS1S ............................................................................................................................. 8 TASK I: STUDY AREA DEF!N(T(ON AND MAP ..................................................................................................... 8 TASK 2: RESOURCE REVIEW ............................................... 8 TASK 3: FIELD INSPECTION ............................................................................................................................... 13 SECTION 4: FLOW CONTROL/WATER QUALITY ANALYSIS AND DESIGN ......................................................... 13 EX(STING HYDROLOGY .................................................................................................................................... 13 DISCHARGE AT NATURAL (EXISTING) LOCATION ............................................................................................ 13 DEVELOPED SITE HYDROLOGY ........................................................................................................................ 14 PERFORMANCE STANDARDS ............................................................................................................................ 14 KCRTS HYDROLOGIC MODEL ......................................................................................................................... 15 FLOW CONTROL ............................................................................................................................................... 16 INF(LTRA TION FACILITY DESIGN ...................................................................................................................... 17 WATER QUALITY.................................................................................................................. . ......... 17 SECTION 5: CONVEYAr<CE SYSTEM ..................................................................................................................... 18 100-YEAR FLOOD/OVERFLOW CONDITION ...................................................................................................... 18 SECTION 6: SPECIAL REPORTS AND STUDIES ..................................................................................................... 18 SECTION 7: OTHER PERMITS ...........................................................................................................••..............••. 18 SECTION 8: EROSION CONTROL ANALYSIS AND DESIGN ................................................................................... 18 CONSTRUCTION SEQUENCE AND PROCEDURE .................................................................................................. 18 TRAPPING SEDIMENT.... .. ............................................ 19 SECTION 9: BOND QUANTITIES AND DECLARATIONS OF COVENANTS ............................................................... 19 SECTION 10: OPERATIONS AND MAINTENANCE ................................................................................................. 19 Appendices Appendix A: Other Reports (Soils Information) Appendix B: Proposed Drainage Plan & Stormwater Facilities Design Appendix C: Erosion Control Details Append ix D: Maintenance Procedures Acronym Terminology ,, Inch cf Cubic Feet cfs Cubic Feet per Second CMP Corrugated Metal Pipe DI Ductile Iron HDPE High Density Polyvinyl Ethane KCSWM King County Surface Water Manual PGIS Pollution Generating Impervious Surface PVC Polyvinyl Chloride RCP Reinforced Concrete Pipe scs Soils Service Conservation Sq Ft Square foot General Notes: 1. The information contained in this report is based on a topography and boundary survey prepared by surveying company, the King County Assessor's map, and on-site observations and measurements. If any changes are made to these drawings or the site that will affect the calculations in this report, the engineer shall be notified. All construction based on this report shall be stopped and shall not proceed until the impact of the changes can be reflected in a supplement report. 2. This report is based on limited subsurface exploration. During construction, if soil conditions are found that are significantly different from those identified in this report, construction should stop until those items affected by the changed conditions can be identified and adjusted, if needed to reflect the changed conditions. 3. This report is prepared for the sole use of client for the purpose of subdividing the property located at 3413 NE 7th Street in the City of Renton, Washington. All other uses are expressly prohibited without prior written approval from the engineer. 4. All construction related to the drainage system for this project will be in accordance with the 2009 King County Surface Water Design Manual and the 2007 King County Roads Standards unless specifically mentioned in this report and/or approved by agency. Central Islands Short Plat -Technical Information Report March 2015 SECTION 1: PROJECT OVERVIEW The property is located at 3413 NE 7th Street in the City of Renton, Washington. There is currently one (1) single family residence on the property. The project proposes to short plat the existing parcel into three (3) total single family residential lots. The existing structures on the property will remain. Proposed improvements include the construction of two (2) new single-family structures, a private access driveway/road, associated utilities and stormwater management facilities. Site Information Address: 3413 NE 7th Street; City of Renton, WA Section/Township/Range: SEY., Sec. 9, T. 23N, R. SE ofW.M. Size: 28,669 sq ft (approximately 0.66 acre) City, County, State: Renton, King County, Washington Governing Agency: King County Design Criteria: 2009 King County Surface Water Manual % ~· J ' l1. · ;1r; '< ·'V.':5 i ' The Concept Group f t-.E1tiP ,. ,, ""4r, ~ Figure 1 -Vicinity Map/ Site Location Not-to-Scale NE 4tt1S1 NE 61h $1 Page 1 Central Islands Short Plat -Technical Information Report March 2015 Looking south towards property from NE 7th Street. The Concept Group Page 2 Central Islands Short Plat -Technical Information Report March 2015 Looking west from property along NE 7th Street. Looking north towards subject property from SE 88 1h Place. The Concept Group Page 3 Central Islands Short Plat -Technical Information Report March 2015 Drainage Basin The property is located within the East Lake Washington drainage basin. The entire property drains to one basin with a contributing area of 0.66 acres. The general topography of the site slopes from north to south. Elevations on the site vary from a high point of 389 feet at the northern property line to 377 feet at the southern property line, with grades varying around 4.0% to 16%. / / \ 68!i ) .,. ) 3<06 The Concept Group J<" 3<09 \\\ \r--:::::::i...J...·· 'i>\lp· \ rOJeCt ) Location I ) (-~-", \ \ J Renton \, ) I \ \ 300/ / i Figure 2 -Drainage Study Area Not-to-Scale \ 611 ... Page 4 Central Islands Short Plat -Technical Information Report Soils Information Soils Survey March 2015 The Soils Conservation Service (SCS) mapped the soils information in the project as AmC, arents, alderwood material. This type of soil is moderately well drained. The KCRTS equivalent soils group, as defined in Table 3.2.2.B of the 2009 King County Surface Water Manual (KCSWM), is Till. A geotechnical report was also performed by Geo Group Northwest, Inc in August of 2014 which found site soils conducive to infiltration. Refer to Appendix A for this geotechnical report and SCS soils map. The Concept Group Figure 3 -Soils Map Not-to-Scale Page 5 Central Islands Short Plat -Technical Information Report SECTION 2: CONDITIONS AND REQUIREMENTS Design Requirements March 2015 The 2009 King County Surface Water Manual sets forth the drainage requirements for this project. The project adds more than 10,000 SF of new impervious surface; therefore is subject to full drainage review. Table 1 · Jurisdictional Reauirements Peak Run-off Control: NIA -0.10 cfs exemption Water nualitv: NIA based on surface area exemption Convevance: NI A -no convevance svstem proposed Downstream Analysis: NIA -infiltration site Core Requirement #1: Discharge at the Natural Location Surface water will continue to infiltrate to native soils with overflow sheet flowing south towards neighboring properties. Core Requirement #2: Offsite Analysis This is an infiltration site; therefore an offsite analysis is not required. However, an abbreviated offsite analysis is provided in Section 3 of this report. Core Requirement #3: Flow Control The property is located within the Duration Forested area per the Pre-Application notes provided by City of Renton staff. However, the project is exempt from flow control requirements because the proposed project generates less than a 0.10 cfs increase in the existing site condition 100-year peak flow rate. Refer to Section 4 of this report for a detailed analysis of the flow control exemption. Core Requirement #4: Conveyance System There is no conveyance system proposed for this project. Core Requirement #5: Erosion and Sediment Control The project will provide erosion and sediment controls (ESC) to prevent, to the maximum extent practicable, the transport of sediment from the project site. Refer to Section 8 of this report for a discussion of the ESC measures proposed. Core Requirement #6: Maintenance and Operations Maintenance and operations of all drainage facilities is the responsibility of the property owner. Maintenance and operation guidelines are provided in Section 10 of this report. Core Requirement #7: Financial Guarantees and Liability This project is exempt from this core requirement because the stormwater facilities are privately owned and maintained. The Concept Group Page 6 Central Islands Short Plat -Technical Information Report March 2015 Core Requirement #8: Water Quality This project is exempt from Water Quality requirements as defined by Core Requirement #8 based on the surface area exemption. Although the project will create 12,166 square feet of new impervious surface, only 4,966 square feet is pollution- generating impervious surface (PGIS). Special Requirement #1: Other Adopted Area-Specific Requirement Based on pre-application meeting notes, no other area-specific requirements are imposed on this property. Special Requirement #2: Flood Hazard Delineation Based on FEMA Flood Map #FM53033C0981 F, the project area is located in Zone X, a 500-year flood plain. Special Requirement #3: Flood Protection Facilities The project is not located in a flood hazard area; therefore, it is exempt from Special Requirement #3. Special Requirement #4: Source Control This project is a single-family residential community development. It is not a commercial, industrial, or multifamily site development; therefore, it is exempt from Special Requirement #4. Special Requirement #5: Oil Control This project not defined as a high-use site per section 1.3.4 of the 2009 KCSWM; therefore, it is exempt from Special Requirement #5. The Concept Group Page 7 Central Islands Short Plat -Technical Information Report March 2015 SECTION 3: 0FFS1TE ANALYSIS Task 1: Study Area Definition and Map The study area of the downstream analysis extends beyond J4 mile from the project discharge location as shown in Figure 4 below. Figure 4 -Drainage Study Area Nat-to-Scale Task 2: Resource Review A resource review was conducted to document existing and potential flooding and erosion problems. Basin Reconnaissance Summary Reports -Project is located in the East Lake Washington -Renton drainage basin and Cedar River/ Lake Washington watershed. No landslide or erosion areas noted in the study area. King County Drainage Complaint Records There are no drainage complaints on record with King County within J4 mile of the project in the past 10 years. The Concept Group Page 8 Central Islands Short Plat -Technical Information Report March 2015 FEMA Maps -Based on FEMA Flood Map #53033C1235F, the project area is located in Zone X, a 500-year flood plain. ----1 I ~ ... w .,_,. The Concept Group ___.------·-- j ~ ill "''""' "'" -· ;...;;.; ', ; ~. """""-·-_,,, __ .. _,,,.' _,, , 'I l, FIRM [I FUIOD INSUWICE UT! MIi' MU' lflMIU -·· -..L'-"'~---:~--:-------1:::.:.:.,~·.:.;:~~=,:~:,:/',"::.~=~7;..";.,";',;::<~ Figure 5 -Flood Map Not-to-Scale ..... ..,...'rt" .... , ... ....,~ •• ,.,, ............................... " .... -"'·-........... r~,,_,_,...,.,..,,,...,.,,, .. .,..._..,,..,.""n"""'"""''~""• .,,.,..,...,'""'mo...,'·"""•,,,..~,..,~"'""' >ho ,w,.,., _.,. ""'· -•....., Page 9 Central Islands Short Plat -Technical Information Report March 2015 Sensitive Areas Folio -The project site is not located in or near a mapped Sensitive Area per the King County sensitive areas inventory maps. Ill -, ,_ ~ ,,., !"' /" ! _3J.S--· r Highlighted Feature County Boundary CAO Shoreline Condition """ u .... m L- Highways Incorporated Area Streets "--(cont) { ) ~' .. 0 ... --- ~ ;./ /\/ m (Z] I C l, .. \ I , ) ((·· . .) --~-~-··/ ·, .... 'i Legend '"""' Parcel• SAO Stream c .... , Ctess 2 Ptira,mml Clan 2 Samon.id C'-l u .......... SAO Wetland SAO Landallda SAO Erosion i '1 Renton , I , I I \ 1, \ Project Location -..,. __ . SWDM Landslide Hazards --Lanoslldetf-..d Dranave CAO Basin Condition The Concept Group Page 10 Central Islands Short Plat -Technical Information Report March 2015 Wetlands Inventory -The project site is not located in or near a mapped wetland per the King County sensitive areas inventory maps. \ I ( / ,,~\. 0 ("\ ~ .. I ! ( ' ' "''T"' i • 0 ~ ,;-, ,1 ! \ \ --' -~---· ! ,, \ \ I, ! I I ! "' ~. ) -- ,{' -------· f\--) ) "··---~,I ! ,i i \ --.. ---- i ·, Renton I ,' . < Project Location ____ 3,_o ____ .I l / -~j"j_5_,. / Ill llighligh1"d Feature -, '-County Boundary CAO Sh«eline Condition r/ """ ,._, Mad- /"' , Low Highway• # Incorporated Area Street& H111h'MI)' ......... (cont) The Concept Group , ....... ) I Legend Lo.- Par,cel• SAO Stream ~ c ... , Cl!Bll:i!~ /.I Clan 2 Samon.td /./ c .... , tJ~ m SAO Wetland ~ SAO Landslide SAO Erosion --~--! ,I SWDM Landslide Hazards il'i!il,-- l.andsllda Hma-d Dniin~ CAO Buin Condition Ill! .... [±1 Mochum D Low Figure 7 -Wetland Inventory Map Not-to-Scale Page 11 Central Islands Short Plat -Technical Information Report March 2015 Hazardous Landslide -The project site is not located in or near a mapped wetland per the King County sensitive areas inventory maps. 111 -1 I_ ~ ,.., ~ /V \ --~··· ---- / I ', 1,, 1. ··"(..'·. " .... -~ ' to C "'""" i I . N£ tryf sr ·, ) '· \ ~ ~ 0 .1- I :: ' ' . "\ \ ~ --~-· ' ' ~~----~31.0 _____ J --j].s -~----. ,,,-,._ ,/ I // ! Legend Highlighted Feature .__ County Boundary Parcels CAO Shoreline CorN:lition SAO Stream """' ': C'-1 M ....... C111n; 2 Pllnlnnuil ""' ;,/ Cbss 2 Salrnonid Highways /"~/ c .... , lnGOIJX)l'.ated Acea \Jf1CIU'sdi.i Streett. m SAO Wetland ........ [%1 SAO Landslide .......... SAO Erosion (conll ) I A ·, Project Location ! '\ .--- SWDM Landslide Hazard& !iitJ Londol,do ......... LancktNki ~ lmiinag,a CAO BHln Conditlon Figure 8 -Hazardous Landslide Map Not-to-Scale The Concept Group Page 12 Central Islands Short Plat -Technical Information Report Task 3: Field Inspection Level 1 Downstream Analysis March 2015 A downstream analysis was conducted on November 10, 2014. The weather was sunny with temperatures in the mid SO's degrees Fahrenheit. The property is located within the East Lake Washington drainage basin. The entire property drains to one basin with a contributing area of 0.66 acres. The general topography of the site slopes from north to south. Elevations on the site vary from a high point of 389 feet at the northern property line to 377 feet at the southern property line, with grades varying around 4.0% to 16%. Surface water infiltrates to native soils with the overflow sheet flowing south towards NE 7th Place. The stormwater is conveyed west towards Monroe Avenue NE. The stormwater then combines with upstream tributary areas and travels south in a closed pipe system along Monroe Avenue beyond a quarter mile from the site and eventually discharges at a regional stormwater facility located near NE 4th Street and Monroe Avenue NE. Task 4: Drainage System Description and Problem Descriptions Based on this field inspection there appears to be no current significant erosion or capacity problems within a \4 mile downstream of the property. Task 5: Mitigation of Existing or Potential Problems Roof stormwater from the development will be mitigated with infiltration trenches. No existing or potential flooding problems, capacity, or erosion problems were observed. Based on the availability of existing drainage information, the developed site will not create or aggravate existing downstream conditions. SECTION 4: FLOW CONTROL /WATER QUALITY ANALYSIS AND DESIGN Existing Hydrology There is currently one (1) single family residence on the property. Surface water infiltrates to native soils with the overflow sheet flowing south towards NE 7th Place. The project site is 0.66 acres; however, only 0.31 acres of new or replaced impervious surface is proposed. Also, the KCSWDM, chapter 1 (page 1-4) defines new pervious surface as " ... the conversion of native pervious surface to non-native pervious surface ... " The site does not contain native pervious surface; therefore, there is no new target pervious surface. Discharge at Natural (Existing) Location Surface water will continue to infiltrate to native soils. During heavy rainfall events, stormwater will continue to sheet flow towards south towards NE 7th Place, discharging to the public storm system located along NE Monroe Avenue and eventually discharge to Lake Washington. The Concept Group Page 13 Central Islands Short Plat -Technical Information Report March 2015 Developed Site Hydrology The project proposes to short plat the existing parcel into a total of three (3) single family residential lots. Proposed improvements include the construction of two (2) new single-family structures, private access road, associated utilities and stormwater management faci I ities. Developed Onsite Assumptions Each new residential lot is assumed to consist of 4,000 sq ft of new impervious surface, of which, 400 sq ft is PGIS driveway. The remainder of the property will consist of landscape and lawns. Table 2 -Developed Impervious Surfaces (SF) Lot 1 (existing surface) 1,500 Lot 2 (assumed max) 4,000 Lot 3 (assumed max) 4,000 Private Road (less grass crete) 4,166 Total New Impervious Surface 13,666 SF (0.31 ac) Lot 2 & 3 Drainage Design On-site roof stormwater runoff will be collected through an underground drainage system consisting of pipes, yard drains and catch basins. An infiltration trench is proposed for the new residential structure. Performance Standards Level 2 Flow Control The property is located within the Duration Forested area per the Pre-Application notes provided by City of Renton staff. However, roof stormwater will be mitigated with infiltration trenches; therefore, flow control facility sizing credits were applied per the requirements for use of BMP credits specified in Table 1.2.3.C. The project is exempt from flow control requirements because the proposed project generates less than a 0.10 cfs increase in the existing site condition 100-year peak flow rate as discussed below. The Concept Group Page 14 Central Islands Short Plat -Technical Information Report March 2015 KCRTS Hydrologic Model The King County Runoff Time Series (KCRTS) Hydrologic Model is the required methodology under the 2009 King County Surface Water Design Manual for sizing detention facilities. The KCRTS equivalent soils group, as defined in Table 3.2.2.B of the 2009 King County Surface Water Manual (KCSWM), for this project is Till. Table 3 -KCRTS Inputs Rainfall Region SeaTac Scale Factor 1.0 Table 4 -Existing Conditions in KCRTS Model Areas (acres) Till Forest Till Grass Impervious 0.31 0.00 0.00 Replaced impervious surface is not considered target impervious surface unless it is part of a redevelopment project. Subdivisions are not redevelopment projects, by definition. Table 5 outlines the assumed developed conditions. Furthermore, the KCSWDM, chapter 1 (page 1-4) defines new pervious surface as " ... the conversion of native pervious surface to non-native pervious surface ... " The site does not contain native pervious surface; therefore, there is no new target pervious surface. Table 5 -Developed Conditions in KCRTS Model Areas (acres) Impervious Roof Impervious Roof Driveway/Private Road (not infiltrated) (infiltrated, not included in model) 0.03 0.17 0.11 TIii Forni 0.28 aaes Till Forest 0.00 acres TIU Pasture 0.00 aaes TIii PashJre 0.00 111cres TIii Grass 0.00 aaes TIii Grass 0.00 •cres Outw•ah Forest 0.00 aaes Outw•sh Forest 0.00 IIICl"CS OUIWflBh Pasture 0.00 •ues Outwash Pe-sWre 0,00 8Cfe11 Outwash Grass 0.00 8CfeS Outwash Griiu;s 0.00 acres Wedand 0.00 aaes Wetland 0.00 acres Impervious 0.00 aues Impervious D.15111cre11 Total Tolal 0.28 IUCS 0.15 acres Scale hcior; 1.00 Hourly Reduced Scale fatter: 1.00 Hourty Reduced Time Series: [island~_(Jdsling ~J Time Serles: :Islands Developed.Isl ----~ Compute Time Series -~~---J I __ ; Compute Time Serles Modify User Input __ _J Modlly User Input I Ale lor computed Time Series (.TSF) FIie tor computed Time Serles (.TSF] ·---·--·----·-------- The Concept Group Page 15 Central Islands Short Plat -Technical Information Report F:ow Frequency Analysis ~~me Ser~es File:Islands Existing.tsf Project Location:Sea-Tac March 2015 ---Annua::_ Peak Flow Rates--------Flow Freq~ency Analysis------- F:icw Rate :(ank Time of Peak - (CFS) 0. 818 2 2/09/01 18:00 0.005 7 1/06/07 3:00 0.013 4 2/28/03 3:00 0.001 8 3/24/04 20:00 0.008 6 1/05/05 8:00 0.014 3 1/18/06 21: 00 0.012 5 11/24/06 6:00 0. 022 1 1/09/08 9:00 Computed Peaks Flow Frequency Analysis Time Series File:islands developed.tsf Project Location:Sea-Tac -Peaks Rar.k Return Prob (CFS) .I?eriod 0.022 1 :oo.oo 0.990 0.018 2 25.00 0. 960 0.014 3 10.00 0.900 0.013 4 5.00 0.800 0.012 5 3.00 0. 667 0.008 6 2.00 0.500 0.005 7 1. 30 0.231 0.001 8 1.10 0.091 0 .021 50.00 0.980 ---Annual Peak Flow Rates--------Flow Frequency Analysis------- Flow Rate Rank Time of Peak --Peaks Rank Return Prob (CFS; {CFS) Period 0.036 7 2/09/01 2:00 0. 071 1 100.00 0.990 0.032 8 1/05/02 16:00 0.054 2 25.00 0. 960 0.044 3 12/08/02 18:00 0.044 3 10.00 0.900 0.037 6 8/26/04 2:00 0.044 4 5.00 0.800 0.044 4 10/28/04 16:00 0.039 5 3.00 0. 667 0.039 5 1/18/06 16:00 0.037 6 2.00 0.500 0.054 2 10/26/06 0: 00 0.036 7 1. 30 0.231 0.071 1 1/09/08 6: 00 0.032 8 1.10 0. 091 Computed Peaks 0.065 50.00 0.980 Table 6 summarizes the KCRTS 100-year peak runoff rates. Without the BMP credits of the proposed roof infiltration trench BMP's, the 100-year peak flow rate of the developed site is still only 0.049 cfs higher than the existing forested condition. Table 6 -Peak Runoff Rates (cfs) Event Existing Condition Developed Condition Difference 100-year 0.022 0.071 0.049 Flow Control Per the 2009 KCSWDM, Section 1.2 (page 1-42), this project is exempt from flow control requirements "far any threshold discharge area in which there is no more than a 0.1-ifs difference in the sum ef the developed 100-year peak flows for those target surfaces suqject to this requirement and the surn ef historic site conditions I oo-year peak flows for the same surface areas. Note.for the purposes ef this calculati014 target surfaces served by flow control BMPs per Appendix C may be modeled in accordance with the flow control B1\.1P facility sizing credits in Table 1.2.3.C (p. 1-47).·· The Concept Group Page 16 Central rslands Short Plat -Technical rnformation Report March 2015 2009 KCSWDM. pa/te J-42 2 The facility requirement in ConscITation Flow Control An:::a~ i~ wai,·ed for an~· threshold discharge ,1rea ln which there is no more than a 0.1-cfs difference in the sum of developc-d l OO-:rear peak flmn, for those target surfaces subject to this requirement and the sum of historic site conditions I 00- year peak flows for the same surface areas . .Vote:fo,· the pmposes of this calculation, forget s111fc1ces senwl by.flow control BJ!Ps per Appendix C mar be modeled in accordance with theflmr conrwl B.\!Pfi1ci/i1y sizing credits in Table 1. 2.3. C /µ. J -4 7/. Flow control facilities are not required because the project creates less than a 0.10 cfs increase in discharge from the existing condition for the 100-year storm event per the KCRTS analysis above. Infiltration Facility Design Soils Survey A geotechnical report was also performed by Geo Group Northwest, Inc. in August of 2014 which found site soils conducive to infiltration. Based on the recommendation of the geotechnical engineering, the site soils are classified as sandy loam. Per the 2009 KCSWM Section C.2.2, infiltration trenches for projects with fine sand soils must be at least 75 feet in length per 1,000 square feet of new impervious roof surface based on a 2 feet wide bottom. An overflow outlet is proposed to sheet flow storm water during heavy rainfall events. Final infiltration trench designs will be provided during the building permit phase when building envelop information is available. Water Quality This project is exempt from Water Quality requirements as defined by Core Requirement #8 based on the surface area exemption. Although the project may create up to 12,166 square feet of new impervious surface, only 4,966 square feet is pollution-generating impervious surface (PGIS). PGIS is defined as "an impervious surface considered to be a significant source ef pollutants in surface and storm water runoff Such surfaces include those sulyect to vehicular use or storage of erodible or leaclzable materials, wastes, or chemicals, and which receive direct rainfall or the run-on or blow-in of rainfall." Non-metal rooftops are not considered PGIS; therefore, are not included in the PGIS area calculations. Water quality is not required for this project because the project does not create more than 5,000 sq ft of pollution generating impervious surfaces. The Concept Group Page 17 Central Islands Short Plat -Technical Information Report March 2015 SECTION 5: CONVEYANCE SYSTEM There is no conveyance system proposed for this project. 100-Year Flood/Overflow Condition During overflow conditions, stormwater will sheet flow south towards SW 1 l 9'h Street. SECTION 6: SPECIAL REPORTS AND STUDIES A geotechnical report was prepared by Geo Group Northwest Inc. No other reports or special studies have been prepared for this project. SECTION 7: OTHER PERMITS Permit for this project included: • Short Plat Approval • Building Construction Permit SECTION 8: EROSION CONTROL ANALYSIS AND DESIGN All erosion and sediment control measures shall be governed by the requirements of the King County Stormwater Design Manual. Refer to Appendix C for Erosion Control Details. The erosion potential of the site is influenced by four major factors: soil characteristics, vegetative cover, topography, and climate. Erosion/ sedimentation control is achieved by a combination of structural measures, cover measures, and construction practices that are tailored to fit the specific site. Construction Sequence and Procedure Prior to the start of any grading activity upon the site, all erosion control measures, including installation of a stabilized construction entrance, shall be installed in accordance with the construction documents. The best construction practice will be employed to properly clear and grade the site and to schedule construction activities. The planned construction sequence for the construction of the site is as fol lows: 1. Flag or fence clearing limits. 2. Install catch basin protection if required. 3. Grade and install construction entrance(s). 4. Install perimeter protection (silt fence, brush barrier, etc.). 5. Construct sediment ponds and traps. 6. Grade and stabilize construction roads. 7. Construct surface water controls (interceptor dikes, pipe slope drains, etc.) simultaneously with clearing and grading for project development. 8. Maintain erosion control measures in accordance with City of Renton and King County standards and manufacturer's recommendations. The Concept Group Page 18 Central Islands Short Plat -Technical Information Report March 2015 9. Relocate erosion control measures or install new measures so that as site conditions change the erosion and sediment control is always in accordance with the King County Erosion and Sediment Control Standards. 10.Cover all areas that will be unworked for more than seven days during the dry season or two days during the wet season with straw, wood fiber mulch, compost, plastic sheeting or equivalent. 11.Stabilize all areas that reach final grade within seven days. 12. Seed or sod any areas to remain unworked for more than 30 days. 13. Upon completion of the project, all disturbed areas must be stabilized and BMPs removed if appropriate. Trapping Sediment Structural control measures will be used to reduce erosion and retain sediment on the construction site. The control measures will be selected to fit specific site and seasonal conditions. The following items will be used to control erosion and sedimentation processes: • Temporary gravel construction entrance • Filter fabric fences (Silt fences) • Ground cover measures such as straw cover and/or hydroseeding • In let protection Vehicle tracking of mud off-site shall be avoided. Installation of a gravel construction entrance will be installed at a location to enter the site. The entrances are a minimum requirement and may be supplemented if tracking of mud onto public streets becomes excessive. SECTION 9: BOND QUANTITIES AND DECLARATIONS OF COVENANTS None known at the time this report was prepared. SECTION 10: OPERATIONS AND MAINTENANCE The owner or operator of the project shall be responsible for maintaining the stormwater facilities in accordance with the requirements as attached in Appendix D. Proper maintenance is important for adequate functioning of the stormwater facilities. If it is unclear whether a problem exists, contact a Professional Engineer. At a minimum, infiltration trenches must be maintained as follows: • Infiltration trenches must be inspected annually and after major storm events to identify and repair any physical defects. Maintenance and operation of the system should focus on ensuring the system's viability by preventing sediment- laden flows from entering the device. Excessive sedimentation will result in a plugged or non-functioning facility. • If the infiltration device has a catch basin, sediment accumulation must be removed on a yearly basis or more frequently if necessary. Prolonged ponding around or atop a device may indicate a plugged facility. The Concept Group Page 19 Central Islands Short Plat -Technical Information Report March 2015 • If the device becomes plugged, it must be replaced. • Keeping the areas that drain to infiltration devices well swept and clean will enhance the longevity of these devices. • For roofs, frequent cleaning of gutters will reduce sediment loads to these devices. The Concept Group Page 20 The Concept Group Appendix A Soils Information Appendices ·1''' .!~ .it' 11 l '",I),\ C i:iiiiiiii N ·-if,n~:: Map Scale 0 5 Soil Map-King County Area, Washington (3413 NE 71h S1reet) :o;,2.,oc, SG2.J:O 562320 1:627 rfpnntcd on A portrc1il [R.'i" x 11'") sheet. ,Meters 10 20 '30 562330 S62340 0 ---~,,~, 180 Map projection: Web Mercator Cori er coord1r1<1tes: WGS84 Edge tics: Lffi.1 Zone 10/\ WGS84 30 GO 120 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 562360 502370 s !S e a s ; ~ ~ ~ I i 0 ; ~ ~ ' ; ,: ~ ~ s ~ ; ; 11/11/2014 Page1of3 47° 29· 42'" N 4T 29' J8"' N GEOTECHNICAL ENGINEERING STUDY PROPOSED SHORT PLAT 3413 NE 7TH STREET RENTON,WASHINGTON G-3710 Prepared for Mr. Thuong (Tom) Pham Central Island Landscape 3556-!20th Ave SE Bellevue, WA 98006 August 6, 2014 GEO GROUP NORTHWEST, INC. 13240 NE 20th Street, Suite 10 Bellevue, Washington 98005 Phone: (425) 649-8757 Email: wchang@geogroupnw.com or agaston@geogroupnw.com .Group Northwest, Inc.~- August 6, 2014 Mr.Thuong(Tom)Pham Central Island Landscape 3556 -120 .. Ave SE Bellevue, WA 98006 SUBJECT: GEOTECHNICAL ENGINEERING STUDY PROPOSED SHORT PLAT 3413 NE 7m STREET RENTON, WASHINGTON Dear Mr. Pham: Geotechnical Engineers, Geologists & Environmental Scientists G-3710 GEO Group Northwest, Inc., has prepared the following geotechnical report for the proposed residential development based upon our subsurface investigation at the site. This work was performed in accordance with our contract with you dated July 16, 2014. GEO Group Northwest, Inc., explored the subsurface soil conditions at the site by directing the excavation of four exploratory test pits on July 23, 2014. Soils encountered at the test pits TP-1 through TP-3 consist of very loose to dense gravelly and fine silty SAND soils overlying dense silty SAND soils at depths ranging from 3.5 to 6 feet below ground surface. Some apparent fills were present within the overlying loose soil zone at these test pits. At the test pit TP-4 location the dense silty SAND soils with some gravel overlie the very dense gravelly silty SAND soils at a depth of 3-feet below ground surface. Based on the results of our study, it is our professional opinion that the site is geotechnically suitable for the proposed development. The proposed buildings can be supported on conventional spread footings bearing on the dense native in-situ site soils or on compacted structural fill placed on top of the dense native soils. The overlying loose site soils and fills are not suitable to support fotllldations due to their loose and variable condition. Based on the findings from our soil investigation at the site, we anticipate that over-excavation and replacement with compacted structural fills will likely be required at the southern two lots. The amount of over-excavation is not currently known since proposed foundation elevations were not available at the time of report preparation. Please refer to the text of the report for more specific recommendations regarding the site development. 13240 NE 20th Street. Suite 10 • Bellevue, Washington 98005 Phone 425/649-8757 • Fax 425/649-8758 August 6, 2014 Proposed Short Plat, 3413 NE 7'" St, Renton, Washington G-3710 Page ii We appreciate this opportunity to have been of service to you on this project. We look forward to working with you as this project progresses. Should you have any questions regarding this report or need additional consultation, please feel free to call us. Sincerely, GEO Group Northwest, Inc. ~'!1( Principal GEO Group Northwest, Inc. TABLE OF CONTENTS JOB NO. G-3710 Page 1.0 INTRODUCTION ...................................................... I 1.1 Project Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 1.2 Scope of Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 2.0 SITE CONDITIONS .................................................... 2 2.1 Site Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.2 Geologic Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.3 Field Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.4 Soil Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.5 Groundwater Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.0 SEISMIC CONSIDERATIONS ........................................... 3 4.0 CONCLUSIONS AND RECOMMENDATIONS ............................. 3 4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4.2 Site Preparation and General Earthwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.2. l Temporary Excavation and Slopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.2.2 Structural Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.3 Spread Footing Foundations ......................................... 6 4.4 Permanent Basement and Conventional Retaining Walls ................... 8 4.5 Slab-on-Grade Floors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.6 Footing Drains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.7 Pavements ...................................................... 10 5.0 LIMITATIONS ...................................................... 12 6.0 ADDITIONAL SERVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . 12 ILLUSTRATIONS Plate I Plate 2 Plate 3 APPENDIX A: -Site Vicinity -Site Plan -Typical Footing Drain Detail TEST PIT LOGS AND SOIL LEGEND GEO Group Northwest, Inc. GEOTECHNICAL ENGINEERING STUDY PROPOSED SHORT PLAT 1.0 INTRODUCTION 1.1 Project Description 3413 NE 7TH STREET RENTON,WASHINGTON G-3710 The project site is located at the southern side of NE 7"' Street in Renton, Washington at the subject address. The subject parcel consists of a 0.6 acre lot which is currently occupied by a two-story single family residence. The existing residence is located adjacent to the northern property line, fronting NE 7"' Street. At the time of our investigation the remainder of the southern portion of the lot was vacant and generally flat or having gentle slopes, except for near the western property line where a west-facing moderate slope has an estimated height of up to 6- feet. Several piles of yard trimmings were located at the site. These were especially evident along the western side of the lot and near the southwestern corner of the lot. The existing building is shown on the attached Plate 2 -Site Plan. Based upon the Plate 2 -Site Plan and infonnation provided by the owner, Mr. Thuong Pham, we understand that the current project parcel is proposed to be subdivided into four new lots. The existing house will remain on the northernmost of the new lots. Wood-framed single family residences are proposed to be constructed near the center of the three new southern lots. A new access road is proposed to be located at the eastern side of the project parcel. 1.2 Scope of Services The ta~ks we completed for this study were conducted in general accordance with the scope of work presented in our contract dated July 16, 2014. The results of our subsurface investigation and our recommendations regarding the proposed development are summarized in the following report. GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Washington 2.0 SITE CONDITIONS 2.1 Site Description G-3710 Page 2 The site consists of 0.6 acre parcel occupied with one single family residence. The existing building is located at the northern side of the lot and the southern portion of the lot is undeveloped. Existing conditions are shown on the attached Plate 2 -Site Plan. 2.2 Geologic Overview According to the geologic map for the site vicinity the soils at the site are reported to be Va~hon Till (Qvt). The Vashon Till soils consist of a mixture of sand, silt and gravel, which was consolidated by overriding glacial ice. These soils can usually be divided into a surficial loose to medium dense weathered zone which overlies the dense to very dense underlying un-weathered till soils. 2.3 Field Investigation GEO Group Northwest, Inc., explored subsurface soil conditions at the site by directing the excavation of 4 exploratory test pits and logging the observed soil conditions on July 23, 2014. The test pits were excavated by the owner using a small mini-hoe. The test pits were located near the proposed development areas, as shown on Plate 2 -Site Plan. The test pits were excavated to depths ranging between 4 and 6 feet below ground surface (bgs). The observed soil and groundwater conditions were logged. The test pits were then backfilled with the excavated site soils. Backfilled soils were not compacted. An attempt was made to locate the test pits outside of the building areas, however, it is probable that test pit TP-2 was located within the building area and other test pits may be as well, dependent upon the final location of the new houses. We recommend that loose fills placed at test pit locations be re- excavated and re-placed and compacted to meet structural fill specifications (below) prior to the construction of any structures, foundations or slabs. GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Washington 2.4 Soil Conditions G-3710 Page3 Soils encountered at the test pits TP-1 through TP-3 consist of very loose to dense gravelly and fine silty SAND soils overlying dense silty SAND soils at depths ranging from 3.5 to 6 feet below ground surface. Some apparent fills were present within the overlying loose soil zone at these test pits. At the test pit TP-4 location the dense silty SAND soils with some gravel overlie the very dense gravelly silty SAND soils at a depth of 3-feet below ground surface. The dense to very dense soil conditions observed at the test pit TP-4 location matched the description for the anticipated Vashon Till soil deposit. Copies of the Test Pit Logs are presented in Appendix A: Test Pit Logs. 2.5 Groundwater Conditions No groundwater seepage was encountered at the test pits. It should be noted that groundwater conditions may fluctuate seasonally, depending on rainfall, surface runoff and other factors. 3.0 Seismic Considerations Based upon our subsurface investigation at the site, it is our opinion that the project buildings may be designed using the Class C soil profile per the International Building Code. It is our opinion that the soils at the project site are not susceptible to liquefaction, due to the absence of groundwater within the loose soil zone. 4.0 CONCLUSIONS AND RECOMMENDATIONS 4.1 General Based upon the results of our study, it is our professional opinion that the site is geotechnically suitable for the proposed development. The proposed buildings may be supported on conventional spread footings bearing on the dense native site soils or on compacted structural fill placed on top of the dense native site soils. The overlying loose site soils are not suitable to support foundations. We anticipate that the dense soils are located at depths ranging from 3.5 feet to 6 feet below ground surface (bgs) at the southern portion of the site. Dense soils may be GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Washington G-37!0 Page 4 located near the ground surface at the northern portion of the site. We anticipate that a significant amount of over-excavation will likely be necessary for at-grade foundations located at the southern-most two lots. We recommend that GEO Group Northwest, Inc., is on-site at the time of foundation excavation to verify that subgrades consist of the dense native soils and that replacement structural fills are properly compacted as specified in this report. It is also important to note that mapping of our test pits indicates that some test pits may have been located at areas where proposed buildings or pavements are to be located. No compaction was performed at the time that the test pits were backfilled. Therefore it is anticipated that the fills at the test pit locations will be loose. We recommend that the contractor plan on over- excavating and placing compacted structural fill at any test pit locations which are located at pavement or building locations. GEO Group Northwest, Inc., can be on-site at the time of grading and building pad preparation to aid in locating test pit locations and overseeing the subgrade repair work. 4.2 Site Preparation and General Earthwork The building pad areas should be stripped and cleared of landscaping clippings, surface vegetation and topsoil. Silt fences should be installed around areas disturbed by construction activity to prevent sediment-laden surface runoff from being discharged off-site. Exposed soils that are subject to erosion should be compacted and covered with plastic sheeting. 4.2.1 Temporary Excavation and Slopes Under no circumstances should temporary excavation slopes be greater than the limits specified in local, state and national government safety regulations. Temporary cuts greater than four feet in height should be sloped at an inclination no steeper than 1 H: IV (Horizontal: Vertical) in the loose site soils. Temporary cuts in the dense site soils may be excavated no steeper than IH:2V provided that no seepage is encountered. If groundwater seepage is encountered during construction, excavation of cut slopes should be halted and the cut slopes should be re-evaluated by GEO Group Northwest, Inc. If necessary the underlying very dense soils may be capable of standing at steeper inclinations such as !H:3V, however, this is dependent upon the conditions at the time of excavation. If it is necessary to form such steep excavation slopes than GEO Group Northwest, Inc., must be retained to evaluate the conditions at the excavation at the time of grading to provide an evaluation of stability. If the proposed temporary excavation slopes GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Washington G-3710 Page 5 encroach upon adjacent properties then it may be necessary to obtain an excavation easement or plan for temporary shoring at those locations. Permanent cut and fill slopes at the site should be inclined no steeper than 2H: IV. Surface runoff should not be allowed to flow uncontrolled over the top of slopes into the excavated area. During wet weather exposed cut slopes should be covered with plastic sheeting during construction to minimize erosion. 4.2.2 Structural Fill All fill material used to achieve design site elevations below the building areas and below non- structurally supported slabs, parking lots, sidewalks, driveways, and patios, should meet the requirements for structural fill. During wet weather conditions, material to be used as structural fill should have the following specifications: I. Be free draining, granular material containing no more than five (5) percent fines (silt and clay-size particles passing the No. 200 mesh sieve); 2. Be free of organic material and other deleterious substances, such as construction debris and garbage; 3. Have a maximum size of three (3) inches in diameter. All fill material should be placed at or near the optimum moisture content. The optimum moisture content is the water content in soil that enables the soil to be compacted to the highest dry density for a given compaction effort. The majority of the surficial site soils will be moisture-sensitive because they consist of fine silty SAND soils. The site soils' moisture sensitivity may make them unusable as structural fill if they are to be placed/compacted as structural fill during the wetter portions of the year. Alternatively, an imported granular fill material may provide more uniformity and be easier to compact to the required structural fill specification. If the on-site soils are to be used as engineered structural fill, it will be necessary to segregate the topsoil and any other organic-or debris-containing soil, because such soils would be unsuitable GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Washington G-3710 Page6 for use as structural fill. Excavated on-site material that is stockpiled for later use as structural fill should be protected from rainfall or contamination with unsuitable materials by covering it with pl as tic sheeting until it is used. Structural fill should be placed in thin horizontal lifts not exceeding ten inches in loose thickness. Structural fill under building areas (including foundation and slab areas), should be compacted to at least 95 percent of the maximum dry density, as determined by ASTM Test Designation D- 1557-91 (Modified Proctor). Structural fill under driveways, parking lots and sidewalks should be compacted to at least 90 percent maximum dry density, as determined by ASTM Test Designation D-1557-91 (Modified Proctor). Fill placed within 12-inches of finish grade should meet the 95% requirement. We recommend that GEO Group Northwest, Inc., be retained to evaluate the suitability of structural fill material and to monitor the compaction work during construction for quality assurance of the earthwork. 4.3 Spread Footing Foundations The proposed buildings can be supported on conventional spread footings bearing on the dense native site soils or on compacted structural fill placed on top of the dense native site soils. Based on the findings from our soil investigation at the site, we anticipate that the dense soils are present at depths between 3.5 and 6 feet below ground surface (bgs) at the southern portion of the site. Over-excavation and placement of structural fill is anticipated at some of the foundation locations, dependent upon the proposed finish grades and the conditions encountered at the building foundation excavations. We recommend that GEO Group Northwest, Inc., be retained to verify competent soils are present at each building foundation location, at the time of construction, prior to the foundation pour(s). Individual spread footings may be used for supporting columns and strip footings for bearing walls. Our recommended minimum design criteria for foundations bearing on the dense site soils or on compacted structural fill are as follows: GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7'h St, Renton, Washington Allowable bearing pressure, Dense native soil Compacted structural fill including all dead and live loads = 2,000 psf = 2,000 psf G-3710 Page 7 Minimum depth to bottom of perimeter footing below adjacent final exterior grade= 18 inches Minimum depth to bottom of interior footings below top of floor slab = 18 inches -Minimum width of wall footings= 16 inches Minimum lateral dimension of column footings = 24 inches Estimated post-construction settlement= 114 inch Estimated post-construction differential settlement; across building width = 1/4 inch A one-third increase in the above allowable bearing pressures can be used when considering short-term transitory wind or seismic loads. Lateral loads can also be resisted by friction between the foundation and the supporting compacted fill subgrade or by passive earth pressure acting on the buried portions of the foundations. For the latter, the foundations must be poured "neat" against the existing undisturbed soil or be backfilled with a compacted fill meeting the requirements for structural fill. Our recommended parameters are as follows: -Passive Pressure (Lateral Resistance) • 350 pcf equivalent fluid weight for compacted structural fill • 350 pcf equivalent fluid weight for native dense soil. -Coefficient of Friction (Friction Factor) • 0.35 for compacted structural fill • 0.35 for native dense soil GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Washington G-3710 Page 8 We recommend that footing drains be placed around all perimeter footings. More specific details of perimeter foundation drains are provided below in Section 4.6 · Footing Drains. 4.4 Permanent Basement and Conventional Retaining Walls At the time of report preparation finish grades for the proposed development were not shown on the site plan. We anticipate that little site grading is proposed and that the new construction will be primarily at-grade. The site plan does not indicate whether or not any retaining walls will be constructed. The following design recommendations may be used for permanent basement and conventional retaining walls at the project site, if necessary. Foundations for all retaining walls should be founded on the dense in-situ site soils or compacted structural fill placed on top of the competent site soils as discussed above in the Section 4.3 -Spread Footing Foundations. Permanent basement walls restrained horizontally on top are considered unyielding and should be designed for a lateral soil pressure under the at-rest condition; while conventional reinforced concrete walls free to rotate on top should be designed for an active lateral soil pressure. Active Earth Pressure Conventional reinforced concrete walls that are designed to yield an amount equal to 0.002 times the wall height, should be designed to resist the lateral earth pressure imposed by an equivalent fluid with a unit weight of 35 pcf for level backfill. At-Rest Earth Pressure Walls supported horizontally by floor slabs are considered unyielding and should be designed for lateral soil pressure under the at-rest condition. The lateral soil pressure design should have an equivalent fluid pressure of 45 pcf for level ground behind the walls. Passive Earth Pressure and Base Friction The available passive earth pressure that can be mobilized to resist lateral forces may be assumed to be equal to 350 pcf equivalent fluid weight in both undisturbed soils and engineered structural backfill. GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7tn St, Renton, Washington The base friction that can be generated between concrete and undisturbed native soils or engineered structural backfill may be based on an assumed 0.35 friction coefficient. Drainage G-3710 Page 9 Based upon the subsurface investigation no groundwater seepage was encountered at the test pit locations which extended to depths of up to 7-feet below ground surface (bgs). If excavations extend deeper than this, such a for detention vaults or full-height basements then seepage may be encountered. If seepage is encountered then GEO Group Northwest, Inc., should be retained to evaluate and provide updated recommendations for the un-anticipated conditions. We recommend that a vertical drain mat, Miradrain 6000 or equivalent, be used to facilitate drainage behind permanent concrete basement and conventional retaining walls. We recommend that the drainage mat be installed on the back side of the wall extending from the finish grade down to a footing drain pipe. The wall footing drain pipe should consist of a 4-inch diameter perforated rigid PVC pipe surrounded by a bed of washed gravel and separated from site soils by filter fabric, Mirafi 140N or equivalent. The drain pipe should be tightlined to discharge to the stormwater system. Backfill behind conventional retaining walls should consist of free-draining sand or gravel soils which are compacted in lifts. Backfill in areas adjacent to basement or conventional retaining walls should be compacted with hand held equipment or a hoepack. Heavy compacting machines should not be allowed within a horizontal distance to the wall equivalent to one half the wall height, unless the walls are designed with the added surcharge. 4.5 Slab-on-Grade Concrete Floors Loose site soils should be excavated from all concrete slab sub grade areas or compacted to a firm and unyielding condition. Slab-on-grade concrete floors may be constructed on top of medium dense to dense native site soils or on top of compacted structural fill placed on top of the competent site soils. The slab-on-grade floors should not be constructed on top of loose soils. A significant thickness of loose and very loose soils are anticipated at the southern two building lots based upon our subsurface investigation. Therefore, we recommend that if concrete slabs are proposed at these areas, then at minimum the slab subgrade areas should be over-excavated to 2- feet below the proposed slab subgrade elevation, the subgrade compacted to a firm condition and GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7'h St, Renton, Washington G-3710 Page 10 then structural fills placed up to the proposed slab subgrade elevation. GEO Group Northwest, Inc, should be retained to verify appropriate over-excavation and placement of compacted structural fills at these areas. If medium dense to dense soils are encountered at the slab subgrade then the over-excavation is not necessary, provided the GEO Group Northwest, Inc., verifies competent soil conditions at the time of construction. To avoid moisture build-up on the subgrade, slab-on-grade floors should be placed on a capillary break, which is in tum placed on the prepared subgrade. The capillary break should consist of a minimum of a six (6) inch thick layer of free-draining crushed rock or gravel containing no more than five (5) percent finer than the No. 4 sieve. A vapor barrier, such as a 10-mil plastic membrane, is recommended to be placed over the capillary break beneath the slab to reduce water vapor transmission through the slab. Two to four inches of sand may be placed over the barrier membrane for protection during construction. 4.6 Footing Drains We recommend that drains be installed around the perimeter of the foundation footings. The drains should consist of a four (4) inch minimum diameter perforated rigid drain pipe laid at or near the bottom of the footing with a gradient sufficient to generate flow, as schematically illustrated in Plate 3 -Typical Footing Drain Detail. The drain line should be bedded on, surrounded by, and covered with a free-draining rock, pea gravel, or other free-draining granular material. The drain rock and drain line should be completely surrounded by a geotextile filter fabric, Mirafi 140N or equivalent. Once the drains are installed, the excavation should be backfilled with a compacted fill material. The footing drains should be tightlined to discharge to the storm water collection system. Under no circumstances should roof downspout drain lines be connected to the footing drainage system. All roof downspouts must be separately tightlined to discharge into the storm water collection system. We recommend that sufficient cleanouts be installed at strategic locations to allow for periodic maintenance of the footing drains and downspout tightline systems. 4.7 Pavements Based upon the site plan we understand that a new private access roadway will be constructed at the site. The adequacy of pavements is strictly related to the condition of the underlying GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Washington G-3710 Page 11 sub grade. We recommend that all pavement subgrades be compacted by several passes of a large vibratory drum roller prior to placement of the crushed rock base. Before paving, we recommend that the sub grade be proof-rolled under the supervision of the geotechnical engineer to verify that the subgrade is firm and unyielding at the time of paving. The proof-roll may be performed by driving a fully loaded dump truck over the subgrade areas. If loose or yielding soils are encountered it may be necessary to over-excavate and replace with compacted structural fill in some areas. For firm and unyielding native subgrade soils we recommend the following minimum pavement sections for driveways: Class "B" Asphalt Concrete (AC) Crushed Rock Base (3/4-inch minus) Or Concrete Pavement Crushed Rock Base (3/4-inch minus) 3 inches 6 inches 6 inches 4 inches We understand that it may be beneficial to install a base pavement layer such as ATB (Asphalt- Treated Base) prior to completion of the project. Oftentimes this can help protect the sub grade from construction impacts and reduce cost related to subgrade repairs during wet weather periods. Consequently we have calculated that the 3-inches of AC over 6-inches of Crushed Rock Base noted above would be equivalent to the following total pavement thickness: Class "B" Asphalt Concrete (AC) Asphalt Treated Base (ATB) Crushed Rock Base (3/4-inch minus) 2 inches 4 inches 3 inches In accordance with the Washington State Department of Transportation Construction Manual, transverse cracks will develop in concrete slabs at about 15 foot intervals along the length of slabs and a slab wider than 15 feet may crack longitudinally. To control cracking of the concrete, contraction joints should be installed. Contraction joints are weakened planes which collect the cracking into a controlled joint, creating a maintainable joint in the slab, and preventing random ragged cracks which spread and require expensive maintenance. We recommend that contraction and construction joints be connected with #5 dowel bars, 30 inches long, 18 inches on center. The contraction joints should be placed at maximum 14 foot intervals. GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Washington 5.0 LIMITATIONS G-3710 Page 12 This report ha, been prepared for the specific application to this site for the exclusive use of Mr. Thuong (Tom) Pham of Central Island Landscape and their authorized representatives. We recommend that this report be included in its entirety in the project contract documents for use by the contractor. Our findings and recommendations stated herein are based on field observations, our experience and judgement. The recommendations are our professional opinion derived in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession current! y practicing under similar conditions in this area and within the budget constraint. No warranty is expressed or implied. In the event the soil conditions are found to vary during site excavation, GEO Group Northwest. Inc. should be notified and the above recommendation should be re-evaluated. 6.0 ADDITIONAL SERVICES We recommend that GEO Group Northwest Inc. be retained to perform a general review of the final design and specifications of the proposed development to verify that the earthwork and foundation recommendations have been properly interpreted and implemented in the design and in the construction documents. We also recommend that GEO Group Northwest Inc. be retained to provide monitoring and testing services for geotechnically-related work during construction. This is to observe compliance with the design concepts, specifications or recommendations and to allow design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. We anticipate the following construction monitoring inspections may be necessary: I. Site clearing and grubbing; 2. Over-excavation and structural fill placement at building foundation locations; 3. Verification of bearing soil conditions for foundations; GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Washington 4. Structural fill placement and compaction; 5. Slab-on-grade preparation; 6. Subsurface drainage installation; 7. Proof-rolling of pavement sub grade areas. G-3710 Page 13 We appreciate this opportunity to have been of service to you on this project. We look forward to working with you as this project progresses. Should you have any questions regarding this report or need additional consultation, please feel free to call us. Sincerely, GEO Group Northwest, Inc. fr(ifl--,{4fr- AdamGaston Project Engineer William Chang. P.E. Principal GEO Group Northwest, Inc. ILLUSTRATIONS G-3710 GEO Group Northwest, Inc. I ! t r f I J \ l ' I l .. , J '-'-,'ll, • ' ·-· I r \ I • .. L • ' i •• , ~ ~ ., - ---~· ,, f I r ' ~-· ,., ' • I I I t l • • • --· .. ..,t .. • • ....... • ,i I I • r .. ' •-.,., t -' . • Gro~R .. ~f!!il!~.~ Inc. .... ~,Al[~ .... - SCALE: NTS DATE: 8-6-14 MADE:AG ~ ' I t I • • I • ' - t ' t ' • I • c ... ~ ,··· t ,.. -: ' .. ·-· • J l ....... ~~' . ..... _, t ·fjfi .. ~; l ,_ ?.J . I ' .t,,; l • l I -~· . .. ... • VICINITY MAP 3413 NE 7TH ST RENTON,WASHINGTON ... ... ' i I < JOB NO.: Q.3710 PLATE: I - ~ g·~'' / ~·t,'fi ~-~''--// ~J'-~" ~11-P~ i~ 8 (") .ro·119 (t~).,,·119 ---~- 8~ .... -"' 8 \ \\ \ \ "'"' __ .--->--------II! i,: LEGEND ~ <. -:. ~~ - ~ <. -:. o,.q ... '3 .,q.. ~ ~ 60.02 ..11:1 '~~ -..::qtrTP-1 i'> i'> § ,-.. §rq~-2 29B.88' (M 92.67' 20' BAfX LOT 3 8,690 SF./F>AE 5,706 SF. rq \ -I>. · ~ .J I -.1.u1 I,,,,,. SOO'bd <ZCf ____ .J 15' F1?0NT ~mi N00'09' 4S"W 70.00 20' BAc..-$: -----TP-4 z LOT 2 6,708 SF./F>M 4,757 SF. I \... ______ _J !O 15' FWONT ., C')... 44.90' -- §i ~ I ~ 111 BAS.ED UPON THE SHORT PLAT PLAN BY APS SURVEY & MAPPING,JlJL'r' 2014 Jft! -TEST PIT NUMBER AND -qa: APPROXIMATE LOCATION TP-1 • Group,,!::J",2!"!.h.~~.~7 Inc. -~YI fA:IC*2~"""41?~ ·- ct,, 17. <o>-°--o > ~'Is "' q "' q "' ~ ;)~~ ~ Q l 2 ~6~~" i ~ ~ ~, .. t: ~ .;;~ ...,_ !" ,-,... ,... r- C)C)C)C) .. (.i...,_ I .... '"'1 .......... ..•• !J:J~f I SJTEPLAN PROPOSED SHORT PLAT 3413 NE TfH ST RENTON, W ASHINOTON !"' l g t ci " ,.; r z I m ' I i ..... i -i I :r I (/) I -i I ;;o I m I I m -i I I ~ I '---, I I Q~g~ I ! § .. ;~ ' l1Q & i· ~-t" = PLATE_: 2 BACKFILL WITH COMPACfEO t,;ATIVE SOIL GEOTEXTILE FILTER FABRIC. MJRAFI i 40N OR EQUIVALENT FREE DRAINING BACKFILL CONSISTING OF WASHED ROUND ROCK OR CRUSHED ROCK MINIMUM 4 INCH DIAMETER PERFORATED PVC PIPE LEVEL OR WITH POSITIVE GRADIENT TO DISCHARGE NOTES: i FOOTING NOT TO SCALE I.) Do not replace rigid PVC pipe with flexible corrugated plastic pipe. 2.) Perforated or slotted PVC pipe should he tight jointed and laid with perforations or slotlii down, with positive gradient to discharge. 3.) Do not connect roof downspout drains into the footing drain lines. SLAB Ill • Group Northwest, Inc. TYPICAL FOOTING DRAIN DETAIL PROPOSED SHORT PLAT SCALE NONE --··- Geotectmical Ehgneers, Geologists. & 61vir!;IYT90tal Sciernists DATE B/5114 MADE AG ~---~- 3413 NE 7TH ST RENTON, WASHINGTON CHKD WC JOB NO. G-3710 Pl.ATE 3 APPENDIX A: TEST PIT LOGS G-3710 LEGEND OF SOIL CLASSIFICATION AND PENETRATION TEST UNIFIED SOIL CLASSIFICATION SYSTEM (US~ ' -: -·----·--·------·---T--· ...... -------------------·-·- GROUP I SYMBOL I TYPICAL DESCRIPTION I : -----·-------rl ----· -~-------- ow I WEU GRADED GRAVELS, GRAVEL-SAND Ii I Cu :c [D6CI I O!O) greaiertha/14 CLEAN MIXTURE. UTTI.E OR NO FINES ,1 ' C: "'(0302 J / {010 ' OGO) ~ 1 and 3 i GRAVELS Ii DETERMINE I ---·----····----------------rPERCENTAGESOFr-----------. ---- MAJOR DIVISION LABORATORY CLASSIFICATION CRITERIA ----------- GRAVELS ! {kt11e Of no POORl V GRADED GRAVELS, AND GRAVEL-SAND[: GRAVEL AND SANO 1 COARSE '""' -"" I """' GP I Ml>m!AES llTTI..E °" NO ~ FROM GRAIN SIZ,: ! NOT MEETING ABOVE AEOOIAEMENTS GAAINEOSOILS: '-''::Era:' i 0,R~--; .. ~M II. SILTYG~:LS.GRAVEL-S~~ILTMIXTURES ·.i 0,5~~ ii -----! AnERBE~~~ETSeeLow·- GRAVELS ! i ! , CONTENT I or PI LESS THAN 4 L---jf, (wrthsOf!Hl 11~-. · cLAYEYGAA~LS GRAVEL-SAN~~v ! je~;:e~2'%.! ATTERBERGU'-«TSABOVE fines) GC MIXTURES : COARSE GRAINED I ! 'A' LINE I I SOILS ARE I _. ! or P.I. MORE THAN 7 I I , i CLASSIFIED AS ~ -----. I SANDS i SW ! WEU. GRADED SANOS. GRAVEUY SANDS, UITL.E I FOUOWS· j Cu=-(D60/ 010) greate,t11an6 ~= I ~· ORNOFlNES Ci:={D302)l(D10"060)b8tween1afl(fJ ...., """.Hall~( ('::,:;,.:" [.i I""'""'' 1· .:· AAD>EO SANOS. GRAVELL~-,;.,.os_ I <51' Fne °"""" I IT-::NG ABOVE.REOUIF;:~MENTS We;ghl:L..arger ISmalerThanNo.4: fines) UTTLEOFINOFINES GW,GP.SW,SP Thar1 No 200 I SIIM!) ~---·-·--r-----__ j -! ATTEABERQ LIMITS BElOW Slave I : DIRTY SM i SILTY SANOS. SAND-SILT MIXTURES I > 12% Fine Gf11ined i "A" LINE II I SANOS L_ I GM. GC, SM, SC CONTEITT CF i with PJ. LESS THAN 4 ' (withsome ! I 5to12%Fme !EXCE:EOS l2%1 ATTERBERQLIMITSABOVE I SC CLAVEYSANOS SAND-CLAYMIXTIJRES Grahe<! usedual ' 'I "A'UNE , ·t ~ / FINES ,__ _____ if---· i fines) t; symbQls / _ _ _____ L_ wltl'1 P 1. MORE n-tAN 7 i . \I LiquidUmil NORGANICSILTS~AOCKFLOUR SANO~SILTS I ' SILTS <~ I Ml OFSUOITTPLASTICITY 1 60 F======,-,r--r,,,-,, FINE-GRAINED ~; ,:?E) ii Liquid Limit I ----I INORGANIC SILTS, MICACEOUS OR~ so ~~~1;~~ ,;,-i--,·-;~----t--,..,,t-/--;---; SOllS >50% I MH DIATOMACEOUS,FlNESANOVOR$1Lr..:S0tl l NO 40SIEVE I I / ---I I INORGANIC-CLAYSOfLOW'PLASTICJTY-:--i t" 40 F CHorOH . -f---- 1 CLAYS 1-U>m I Cl GAAVEU.Y,SANOY.ORSILTYCL,<VS.CLEAN 1 ~ 1 1 (Above A-uie on < 30% I CLAYS ~ I P-,, cnan t --1 ;,-30 t-+-+--+--t---!f---J~t-+-+-+-1 ......... _..,,: """'Lmt I CH i INOAGANlC CLAYS OF HlGH PLJ,STICITY, FAT I t; ' V l I > SO% , : CLAYS (/) .. ~ 20 t-+-+'-C-;L-"'_Olh'H--+-+-l-t-+--l ~:S:"1eri,yl-Liquid~---t·-----~ !: 0RGANICSILTSAN00AGANICS1LTYCUYSOF / _I/ MHo,OH ThaflS:~200 ORGA;~.;~LTS&~.c:-_ __ ; ---· --~~LAsnc1rv _J ~o )..i Ml / I ,- c 1 _=';:.";' I "':"' ,.~t· I OH i ORGANIC CU.YSOF H,GH PLASTICITY .J 'o O 10 ,o Jll <O :0 OD 70 OO ,o 100 110 ---I I LIQUID LIMIT(%) HIGHLY ORGANIC SOILS I Pt i PEAT AND OTHER HIGHLY ORGANIC SOILS i SOfL. PARTICLE SIZE 1------~----------·-··-GENERAL OUIDAHCE OF SOil ENGINEEFl9rf0 PROPERTIES FROM STANDARD PENEmATION TEST (BPT) U.S. STANDARD SIEVE -·-·--tt------------------,------------1 FRACTION Paulng : Rmlned SANDY SOILS I Siew 1 Sm ) Sleft ! ··-5----r-- --"''""'· F"""' ! __ --JJ"'."'! I (mm) -.-.. -.-,-.,...--.-_ _,+I ·~ i ·"· r +----H-----+-----1-- -I I i I I Counm """" -N % ., ...... 0·4 I 0-15 , I , r' #40 0.425 ! •200 MEDIUM t10 I 2-+' __ '_'°---;1--_O.~ ; I" J':1 II ,~o ,___COA_A_s_•______ I_-"-~ ____ ,) __ ~ FINE 0075 4 75 ~-c~ +i-----,._""" __ '°"" mm 80ULOER$ i .. 203 l'M1 ---·--1---------------ff """" i ---i-------·-----------11 1 4· 10 I 10-JO 3(). 50 I > 50 15 " ,. "' ,. .. 28 " ., " 35 42 85 · 100 38 .. 13240 NE 2Clh Street. Sulle 10 Phone (425) 649-8757 SILTY & CLAYEY SOILS - I I ""'°"-I --=.~-! N __ I q,.u1 . V"'f Loooe <2 , -< 0.25 j Very sott ' I Loooe ,., I 0.25 050 Soft ' Medium°""" ••• Q.50-1.00 I Medium Stiff °""" 8-15 I 1.00 · 2.00 .,,, V"'f "'"'8 15-30 2.00-4.00 I V"'f5'11 I > 3() ..... 00 i ' - PLATE A1 TEST PIT NO. TP-1 LOGGEOBY AG TEST PIT DATE: 07/23/2014 ---------- DEPTH SAMPLE Water OTHER TESTS/ fl_ uses SOIL DESCRIPTION No. % COMMENTS Al ground surface -pile of organic debris (landscaping material) and -bricks -Tan fine silty SAND with cobble and gn1.vcl, dry, very loose to loose Probe 18" SM -Probe 15" - 5 - Probe 8-18" Probe 6-8" --------. --------------------------------------------------SM Brown fine silty SAND with gra"·el, moist, medium dense to dense Probe 3-4" -Total depth of test pit= 7' below ground surface (bgs) -No groundwater seepage encountered 10 _ Competent native soils encountered at 6' bgs - - - - 15 _ TEST PIT NO. TP-2 LOGGED BY AG TEST PIT DATE: 07/23/2014 DEPTH SAMPLE Water OTHER TESTS/ fl. uses SOIL DESCRIPTION No. % COMMENTS Piece of concrete debris at surface I' x 2' x 6" Probe 1-6" -SM Dark brown/gray gravelly silty SAND, dry lo moist. dense Probe 1-3" ----------------------------------------------------------Probe 1-3" -SM Tan fine silty SAND with some gravel and SAND, dry to moist, Probe 1-3" -variable dense lo loose Probe 13-18" 5 -Probe 4-6" -Total deplh of lest pit= 6' bgs No groundwater seepage observed -Variable loose to dense soils encountered at depths between 3 and 6 . feet bgs. 10 _ - - - - 15 _ TEST PIT LOGS • PROPOSED SHORT PLAT Grou~ Northwest? Inc. 3413 NE 7Til ST Geot&chncal EnginNrs, Geologats, & RENTON, WASHINGTON Bwhll'lnllll'ltlll Scientists JOB NO. G-371 O DATE 7/23/14 PLATE A2 TEST PIT NO. TP-3 LOGGED BY AG TEST PIT DATE: 07/23/2014 --------- DEPTH SAMPLE Water OTHER TESTS/ n. uses SOIL DESCRIPTION No. % COMMENTS SM Brown fine silty SAND with some gravel, dry, dense Probe <l" - -Drain tile and drain rock ohserved above a depth of 3'-4" -apparenlly Probe 2-3" excavated into an in-active dr.:tinfield -----------------------------------------------------------Probe 2-4" 5 - SM Tan fine silty SAND with some gravel, dry to moist, medium dense and Probe 2-4" dense Probe 3-5" -Total depth of test pit= 6' below ground surface (bgs) No groundwater seepage encountered -Competent native soils encountered at 3.5' bgs - 10 _ - - - - 15 _ TEST PIT NO. TP-4 LOGGED BY AG TEST PIT DATE: 07/23/2014 DEPTH SAMPLE Water OTHER TESTS/ n. uses SOIL DESCRIPTION No. % COMMENTS Probe <I" -SM Brown/gray fine silty SAND with some gravel, dry, dense Probe I" -Probe 2-3" --------Pmbe<2" SM Gray gravelly silty SAND, dry to moist, dense to very dense Probe <I" -I'-.. (un-weathered glacial till) 5 - -Total deplh of test pil = 4' bgs No groundwater seepage observed . Competent native soils encountered at ground surf.ace - - 10 _ - - - - 15 _ TEST PIT LOGS • PROPOSED SHORT PLAT Group Northwest! Inc. 3413 NE 7TH ST ~I &IQNe,s, Geologists, & RENTON,WASIDNGTON Envi'cJomtlntaj Scielntlsla JOB NO. G-3710 I DATE 7/23/14 PLATE A3 - The Concept Group Appendix B Proposed Drainage Plan Appendices --------____j__ _ --- -.,~--____j__ - bl/5 g~ bl~ c;O ~~ "' ROW CENTERLINE NE 7TH STREET 10.0' VERTICAiSAWCUT r=--.::.:--=--~.::.: 1:l.O' 30.0' 8.0' PLANTER STRIP 8" ROW 5.0' 3.5' SIDEWALK 1.0' _12&.. " 4:1 OR FLATER 2" CRUSHED SURFACING TOP COURSE (CSTC) w z ~ /: ~ w C 0 oc C 10.0' TRACT "A" w VARIES 20.0' TO 24.01' z ~ 'i. /: PVT. ACCESS ROAD oc I w C 0 oc C 10.0' ~ wt--~ ~~~ 6" CRUSHED ROCK CEMENT CONCRETE TRAFFIC CURB & GUTTER PER COR STD. PLAN 101 4" CEMENT CONCRETE SIDEWALK PER COR STD. PLAN 102 t._"_'"ro""~'• a t-- ~ a:: 0 J: Cf) 0 z ::5 Cf) ...J ~ t--z w u 1 ' J l r ~ ; ~ "' ' & s ! l ' ~ 0 .>>·" -.... ,, .• , [ !"''""'"' ,1·:~~~'""'"""~::1,:.3: , (7,088SQ.FT) :. ·'t-.· Q~ • .. ~ '.~1 ~ 1"¥ I ',I ,..,,.,.,.,,,.,, .... ., .... ,,_,.,.,,,,~,.,., ............. , '• g ._,,.. ·+---+ RASSCRETE (609 SF) @ 0.00% SEE PAVER SECTION ON THIS SHEET ss.1~· M19"5S'IJ2"E -i9.9J" LOT 2 ,/'." .••...... i ·.TMct'1_1fA11 I xr~!t~·/':tf'. I ~{2(! : 1 (7,743 SQ. Ff) 5' IJTJUTY EAS"E.MENT 7 I "II.' Ii•.:• ,11, i.( ·, I . l F-----.ii.' ____ _1 _____ ~ IN..l-t.JY r11 I I I I ~I 'I: JD 1~ i r I ~ '\. '· ')'> S89"50'05"W LOT3 (8,920 SQ. FT) PT.,_ 11 +23.55 .,,·_ '",-'J 408 404 400 396 392 388 384 380 376 372 388 4" SANDY PLANTING SOIL NE 7TH ST. -TYPICAL SECTION g~ «i"! ".;:'m3: e'i?rn a>~ ~WO ~~G fi'.£ ca olW ~~ 6~ -M i'.3,~ >> SCALE: NONE 60.00'VC PVISTA=10+80 PVI ELEV = 385.88 A.D. = 4.12 K., 14.56 FINISH GRADE -1~ +~ ::~ ::::& ... d ~~ ~r,.j" It.!!.._ ~M >Z I-... w -..... ...I I-i ... w::::i m;!: ~o 4Jv.iir~ il · OJ. ID ID ----1/SOC' -tj.21% !f ~200% 63~x ~O:N~ -J .E.._,._=====L-,..:.~-.,.=- 11'1 PRIVATEAC::S_] ____ _ Ji'! ~j[D ~ ~ INFILTRATION TRENCH 6W X S2'L X 2'0 (BOTTOM ELEV=382.00) -5 LF 6" 0 SOLID ADS Nt:2 @0.0% PRIVATE ACCESS INFILTRATION TRENCH 6W X 52'L X 2'D (BOTTOM ELEV=380.00) -2.15% 52:lf 6" 0 PERf. ADS N1-2 @0.0% 2" COMPACTED DEPTH HOT MIX ASPHALT (HMA) CLASS Yi" 2" COMPACTED DEPTH CRUSHED SURFACING TOP COURSE 4" COMPACTED DEPTH CRUSHED SURFACING BASE COURSE TO 95% MAX. DENSITY PVT. ACCESS ROAD -TYPICAL SECTION ~ -~ ~ ~~ + NO ~ 'it: "> . t~~ m ~c 5 >z ~ cw 5 LF 6" 0 SOLID ADS N12@0.0% 408 404 400 398 392 388 384 380 376 372 388 SCALE:NONE TURFSTONE (MUTUAL MATERIALS) (3)'2" X 23 %" X 15 X") 6" CRUSHED ROCK{%") 364 52 LF 6" 0 PERF. ADS N12 @0.0% EX. GROUND \ / FINISH ,GRADE 3601 f I I I I I I I 111 384 PAVER SECTION 360 SCALE: NONE . " ~ " 9-1-80 10+00 ~11, •m .. nM 10-+20 ;:::~ "Im ~~ 10-+40 CONSffiUCTION NOTES: 'I' "!'-: . , .. n~ 10-1-60 ·1m "!'": .. .. nM 10-1-80 ,Im 0~ <O <ci . . nM 11•00 ·1~ "~ •w nM 11•20 'lfll •v ~~ 11+40 PVT. ACCESS -PROFILE (D INSTALL CB #1-TYPE 1 WNANED GRATE & OIL/WATER SEPARATOR PER DETAIL 2 ON SHEET OT1. STA 11+32, CENTERLINE RIM=384.77. IE{N)=382.00 @ INSTALL CB #2-TYPE 1 WNANED GRATE & OIUWATER SEPARATOR PER DETAIL 2 ON SHEET DT1. STA 12+31. CENTERLINE RIM=382.64, IE(N)=380.00 @ CONSTRUCT PVT. ACCESS INFILTRATION TRENCH (6'W x S2'L x 2'D). SEE PROFILE THIS SHEET & DETAIL 3 ON SHEET DT1. @) PROPOSED (SW x 63'L x 2'D) ROOF INFILTRATION TRENCH PER DETAIL 1 ON SHEET DT1. (TO BE REVIEWED AND CONSTRUCTED AT BUILDING PERMIT APPLICATION. @ PROPOSED (SW x 60'L x 2'D) ROOF INFILTRATION TRENCH PER DETAIL 1 ON SHEET DT1. (TO BE REVIEWED AND CONSTRUCTED AT BUILDING PERMIT APPLICATION. @ INSTALL 5 LF 6" SOLID ADS N12@0.00%. ~1~ ~~ 11-1-60 ~1~ n '° ·~ 11-1-50 '1-nM n~ .. nM 12+00 j n 00 • -. n N ~ .. n~ 12-1-20 12-1-40 12+60 @) INSTALL MAILBOX PER COR STD. PLAN H027, H028 & H029. @ CONSTRUCT 4' THICK CEMENT CONCRETE SIDEWALK PER COR STD. PLAN 102. @ CONSTRUCT 5' WIDE ASPHALT RAMP (1:12 SLOPE MAX.)WITH TRUNCATED DOOM. @) CONSTRUCT ASPHALT WEDGE AND MATCH EXISTING. @ SAWCUT & PATCHING ASPHALT PAVEMENT PER COR STD. PLAN H032.1. @ UTILITY TRENCH (POWER & COMMUNICATIONS). CONTRACTOR TO COORDINATE WITH UTILITY PROVIDERS FOR CONDUIT TYPE & SIZE. @ CONSTRUCT CEMENT CONCRETE TRAFFIC CURB PER COR STD. PLAN 101. V[RTIC/\L GRJ\PHIC SCALI:. 10 5 0 j 10 1 ;nch ., II) tl HOR•ZONT/\L GRAPHIC ~C/>-H 20 10 0 10 70 J;nch=£Utl 0 CONSTRUCT 18' WIDE DRIVEWAY ENTRANCE PER DETAIL ON SHEET DT1. I CALL 48 HOURS @ CONSTRUCT 20' WIDE DRIVEWAY ENTRANCE PER DETAIL ON SHEET DT1. BEFORE YOU DIG -------------------' NSS!:i'.!w 1· ____ 1 ________ @a'WIDEPLANTERSTRIPWITHSODORBARK. I 1-800-424-5555 I UA"E ........... JOB NO SURl'EYED = } PBG ~ Lt1.11C -""-' H .,,,._ . '.~N' K~, ·~· ~N ••. ,~, ·~. - 0[51G>/ED: H_,_____ti,_ PHAN ::~ !~'.'"::.:... :::....".~ !~ S~~~; ~LAT 2-10-2015 1"=20' ,~®"' 3413 NE 7TH STREET I LDBOOK :R CITY OF RENTON, WA 98056 PAGE g 8 Land Planning • Gvil Engineering 5130 South 166th Lane SeaTac, WA 98188 t----+------------------<f---+-----<f---< JIIA\\~: H. H.PHAN Cl!ECKECc AT:~~e I s~l. ~0~.;,'",!.~, Y I RENTON Plannlng/Building/Publlc Works Dept. ROADWAY/ DRAINAGE -, ... ----·· -T (206) 229-6422 -~, ....... .,;,r _,., PLAN .. HU .... ILt: ANU ::i ............... NO. REVISION BY DATE APPR , I I ···~ SECTIONS )RAM!ol(;NO DR1 SffcE~ o• 3 5 w ~ < z ~ al 3 ~ • f- <( -' a.. f-a:: 0 I en Cl z <( -' en -' <( ~I 1 ' I 1 3 ~ a ~ I / ' • ' , / 0 l " z "1 . t:, ~-. ~ SEE PLANS 10.0' MIN 5.0"MIN 6" RIGID PERFORATED PIPE@ 0.0% ROOF DRAIN A._j CATCH BASIN OR AREA DRAIN WITH SOLID LID NTS WASHED ROCK 314" -1112" 6" RIGID PERFORATED PIPE@0.0% 'EXISTING GROUND -',,,,.,J7:.":c;"· .. ' .. ,,,-.,' ... -- FINE MESH SCREEN ELEVATION VIEW NTS BACKFILL~ __ [E:l:TINGGROUND ' .., --~ --, ---,. ] ,~',.: : OD -. _'.,,_•, '' ·,': ~ ~ 5.0' WRAP WASHED ROCK ENT!REL Y WITH FILTER FABRIC (TYP} 6' RIGID PERFORATED PVC PIPE LAID LEVEL (TYP) WASHED ROCK 3/4" -1 1/2' (1YP) ~~o~~FIL TRATION TRENCH DETAIL Ci) FINISHED GRADE VANED GRATE PROPOSED ACCESS ROAD SECTION SEE ROADWAY DRAWING ~ ~ PVT. ACCESS 6.0' i3 ~ 6"' MIN. GRAVEL BACKFILL WRAP WASHED ROCK ENTIRELY WITH Fil TER FABRIC 6" RIGID PERFORATED PIPE (ADS OR CMP) WASHED ROCK 314" -1 112·· ~ Oil COLLECTION ---,lftl--1 TO INFILTRATION TRENCH ~I II SEDIMENT COLLECTION CATCH BASIN-TYPE 1 OIL/ WATER SEPARATOR DETAIL ® SCALE: NONE ~~~~;::, TION TRENCH DETAIL 0 Cl. 4000 CONCRETE ISOMETRIC VEW 5.0' 3/8" EXPANSION JOINT (TYP) ORIVEWA Y ENTRANCE SIDE SLOPE {TYP.) DRIVEWAY DRIVEWAY RAMP SEE PLAN " ~ SEE NOTE 1 A 5.o· ~ CEMENT CONCRETE CURB & GUTTER PLAN VIEW 8.0' SECTION@ NOTES 1. WHEN THE DRIVEWAY WIDTH EXCEEDS 15 FEET, CONSTRUCT A FULL DEPTH EXPANSION JOINT WITH 318" JOINT FILLER ALONG THE DRIVEWAY CENTERLINE. CONSTRUCT EXPANSION JOINTS PARALLEL W!TH THE CENTERLINE AS REQUIRED AT 15 FEET MAXIMUM SPACING WHEN DRIVEWAY WIDTHS EXCEED 30 FEET. 112" MAX. LIP BETWEEN ROADWAY GUTTER & CURB DEPRESSED CURB & GUTTER CE~NT CONCRETE DRIVEWAY ENTRANCE SCALE: NONE I ,oBNo, '~"''° s= CENTRAL ISLAND SHORT PLAT r;''.10-201sl '. ~'El!)l'A;!~ 'lj'-l'F~-,c /~• ~;,,,~ ~~'"' ,00~::C~:Jl., CITY OF 3413 NE 7TH STREET ,,_,,-. > ,!iF' ,!ill~ §' .ILi .ILi .~',"'{' H, H, PHAN ~ !JD RENTON, WA 98056 "' Land Planning • Civil Engineering ., ;.~. PHAN DATUM ~ RENTON 15 130 South 166th Lane CHECllErt I Of,EINCH I \. Plannlng/Bulld!ng/Publlc Works Dept. 1 DET ILS 42815 mlUCALE '--SITE A SeaTac, WA 98188 :%.~~,~ ~ s~O:C~:;·(L T (206) 229-6422 ...,_~,om r" IJ'F'ROl'ED: ,~, ·"'u""'~ DT1 N' NO. REVISION BY DATE I APPR 5 5 6" 12" FIGl"RE C.2.2.A TYPICAL TRE:XCH I~FILTR.\TIO:X SYSTE:\I ·---./'----- v roof -.:;~ ~ drain PLAN VIEW NT$ / 4" rigid or 6" flexible _..----._--_··_·_··_··_-·_·_··_-·_·_·-_·-_··_·_·-_··_·_··_··_··_·_··_l_-_··_··~· -p-e-rlo_r....,,-8,1---~ ....... ···-·· ........ --.... ---------------·-.... . infiltration trench sump wlsolid lid PLAN VIEW ·---------------- NTS ..... ··································---.---·l..J'•" : (; ~ overflow ----- splash block ~ roof drain ,-· -~ _J : 6 CJ C· =======::=:1m;i::;::=:==:;::;::=7==:::::~ --t;,.,\(. r\ n r\ (, '"'D [! : 1·A ~'--~ washed rock --\ :--•.6 .\ "' l)., .-: :\ C' c-;-=-1 1/2"•3/4" 0 '•-.J. ~, 0 <) (, ,;:. f,: 1'min 5.0'min I 11. • -~=·'··'·'··"·'·'-'', 1'min I line mesh "---CB sump wlsolid lid cf'r.:i.on filter fabric -\ __ H --· compacted backhll '"" 1 " ri'"' ~ ~ ~ -, 0 O'-' D -:: :<" 4" rigid or 6". flexible , >--: L' perlorated pipe 24" --~"' r/ _6 ~ D V I f -c o ',' (>,D o f , ,; ",.., 0 ,; c V l 12.. 0 v v \7 0 v washed rock ;.,; 6 c\ \' (: ~ \ 1 1/2" 3/4" l >>-:Fco<:>,Jn" - /. I '~ / ;' <.J />,:_.D0~0.i:J --;:;:.~ ;';/,'$/,0"' , Z<V.-<.~:.<.0::'<-{-:(( , L---24~ SECTION A NTS 2009 Surface Waler Design lvfmnml -Appendi.....: C' C-45 I 9/2009 The Concept Group Appendix C Erosion Control Appendices i 1.l ~ ~ ...J (L f-- ci:: 0 I Cf) Cl ~ ~ ...J ~ f--z w (.) 1 3 ' ~ l ' t ~ ~ ii • / ! ' ' " / l ~ ,_',/;;- "~-·"<'. - ~-/ ~ ------------ NE 7TH STREET ---·-r ,.,_ ,,·,; -'-'-'tt ,,,; El' .,, .. ., io:· -;;rl5 -- M~ "' INSTALL CONSTRUCTION ENTRANCE PER DETAIL ON T~IS SHEET - s'sii~'W"E 7J_94":"'" 9!i.95 . . "'!" ~ c;O M~ "' ""''""""'""""''m~"' '"""''"'"'"I' LOT 1 (7,088 SQ. FT) ~-~lti •: EX. HOUSE !j §. LrTO.REMAIN.-........ ~ ... J i ;;, . · l -'.S.---4---~-···-" INSTALL INLET PROTECTION (TYP) PER DETAIL THlS SHEET 55.7~· "f 49.!JJ' rsw· "I TRACT 11A11 Ii': (4,919 SQ. FT) .. L'';L~T2 (7,743 SQ. FT) CKPILE '6:0T I I I 'i I : INSTALL PLP,,STIC o·oY,fiRING PER DET,U. ON THJS5HEET ,/' ,, .f ~ I • "' I I: I > I .,;:'UTILITY I • . i" I --, S · I .EASEMENT "' I t, I L~ -~,91' I T · S89"5G'!J6'W -~- LOT3 (8,920 SQ. FT} ··, ;/:· •, INSTALL SILT FENCE' • •,. [PER DETAIL ON THIS SHEET ~-. --,:.,. ' ,..... ·-·-·-·-·-·-·-·-·--·-· ... ~ ~ 1® I~ EX. TREE TO BE REMOVED {TYP) EROSION AND SEDIMENT CONTROL NOTES, 1----------------------------~--------- 1. APPROVAL OF THIS EROSION AND SEDIMENT CONTROL (ESC) PLAN DOES NOT CONSTITUTE AN APPROVAL OF PERMANENT ROAD OR DRAINAGE DESIGN {E.G., SIZE AND LOCATION OF ROADS, PIPES, RESTRJCTORS, CHANNELS. RETENTION FACILITIES, UTILITIES, ETC.). 2. THE IMPLEMENTATION OF THESE ESC PLANS AND THE CONSTRUCTION. MAINTENANCE, REPLACEMENT, AND UPGRADING OF THESE ESC FACILITIES IS THE RESPONSIBILITY OF THE APPLICANTIESC SUPERVISOR UNTIL ALL CONSTRUCTION IS APPROVED. 3. THE BOUNDARIES OF THE CLEARING LIMITS SHOWN ON THIS PLAN SHALL BE CLEARLY FLAGGED BY SURVEY TAPE OR FENCING, IF REQUIRED, PRIOR TO CONSTRUCTION (SWOM APPENDIX D). DURING THE CONSTRUCTION PERIOD, NO DISTURBANCE BEYOND THE CLEARING LIMITS SHALL BE PERMITTED. THE CLEARING LIMITS SHALL BE MAINTAINED BY THE APPLICANTIESC SUPERVISOR FOR THE DURATION OF CONSTRUCTION. 4. STABILIZED CONSTRUCTION ENTRANCES SHALL BE INSTALLED AT THE BEGINNING OF CONSTRUCTION AND MAINTAINED FOR THE DURATION OF THE PROJECT. ADDITIONAL MEASURES. SUCH AS CONSTRUCTED WHEEL WASH SYSTEMS OR WASH PADS. MAY BE REQUIRED TO ENSURE THAT ALL PAVED AREAS ARE KEPT CLEAN AND TRACKING OUT TO ROAD RIGHT-OF-WAY DOES NOT OCCUR FOR THE DURATION OF THE PROJECT. 5. THE ESC FACILITIES SHOWN ON THIS PLAN MUST BE CONSTRUCTED PRIOR TO OR IN CONJUNCTION WITH ALL CLEARING AND GRADING SO AS TO ENSURE THAT THE TRANSPORT OF SEDIMENT TO SURFACE WATERS, DRAINAGE SYSTEMS. AND ADJACENT PROPERTIES IS MINIMIZED. 6. THE ESC FACILITIES SHOWN ON THIS PLAN ARE THE MINIMUM REQUIREMENTS FOR ANTICIPATED SITE CONDITIONS. DURING THE CONSTRUCTION PERIOD, THESE ESC FACILITIES SHALL BE UPGRADED AS NEEDED FOR UNEXPECTED STORM EVENTS AND MODIFIED TO ACCOUNT FOR CHANGING SITE CONDITIONS (E.G., ADDITIONAL COVER MEASURES, ADDITIONAL SUMP PUMPS, RELOCATION OF DITCHES AND SILT FENCES, PERIMETER PROTECTION, ETC.) 7. THE ESC FACILITIES SHALL BE INSPECTED DAILY BY THE APPLICANTIESC SUPERVISOR AND MAINTAINED TO ENSURE CONTINUED PROPER FUNCTIONING. WRITTEN RECORDS SHALL BE KEPT OF WEEKLY REVIEWS OF THE ESC FACILITIES. 8. ANY AREAS OF EXPOSED SOILS, INCLUDING ROADWAY EMBANKMENTS, THAT WILL NOT BE DISTURBED FOR TWO DAYS DURING THE WET SEASON OR SEVEN DAYS DURING THE DRY SEASON SHALL BE IMMEDIATELY STABILIZED WITH THE APPROVED ESC COVER METHODS (E.G., SEEDING, MULCHING, PLASTIC COVERING, ETC.). 9. ANY AREA NEEDING ESC MEASURES NOT REQUIRING IMMEDIATE ATTENTION SHALL BE ADDRESSED WITHIN SEVEN (7) DAYS. 10. THE ESC FACILITIES ON INACTIVE SITES SHALL BE INSPECTED AND MAINTAINED A MINIMUM OF ONCE A MONTH OR WITHIN TWENTY·FOUR (24) HOURS FOLLOWING A STORM EVENT. 11. AT NO TIME SHALL MORE THAN ONE (1) FOOT Of SEDIMENT BE ALLOWED TO ACCUMULATE WITHIN A CATCH BASIN. ALL CATCH BASINS AND CONVEYANCE LINES SHALL BE CLEANED PRIOR TO PAVING. THE CLEANING OPERATION SHALL NOT FLUSH SEDIMENT LADEN WATER INTO THE DOWNSTREAM SYSTEM. 12. ANY PERMANENT RETENTION/DETENTION FACILITY USED AS A TEMPORARY SETTLING BASIN SHALL BE MODIFIED WITH THE NECESSARY EROSION CONTROL MEASURES AND SHALL PROVIDE ADEQUATE STORAGE CAPACITY. IF THE PERMANENT FACILITY IS TO FUNCTION ULTIMATELY AS AN INFILTRATION SYSTEM, THE TEMPORARY FACILITY MUST BE ROUGH GRADED SO THAT THE BOTTOM AND SIDES ARE AT LEAST THREE FEET ABOVE THE FINAL GRADE OF THE PERMANENT FACILITY . 13. COVER MEASURES WILL BE APPLIED IN CONFORMANCE WITH APPENDIX D OF THE SURFACE WATER DESIGN MANUAL 14. PRIOR TO THE BEGINNING OF THE WET SEASON (OCT. 1), ALL DISTURBED AREAS SHALL BE REVIEWED TO IDENTIFY WHICH ONES CAN BE SEEDED IN PREPARATION FOR THE WINTER RAINS. DISTURBED AREAS SHALL BE SEEDED WITHIN ONE WEEK OF THE BEGINNING OF THE WET SEASON. A SKETCH MAP OF THOSE AREAS TO BE SEEDED AND THOSE AREAS TO REMAIN UNCOVERED SHALL BE SUBMITTED TO THE CITY OF BURIEN INSPECTOR FOR REVIEW. RECOMMENDED CONSTRUCTION SEQUENCE, 1. PRE-CONSTRUCTION MEETING. 2. POST SIGN WITH NAME AND PHONE NUMBER OF ESC SUPERVISOR (MAY BE CONSOLIDATED WITH THE REQUIRED NOTICE OF CONSTRUCTION SIGN). 3. FLAG OR FENCE CLEARING LIMITS. , _ ~~ , "'fl'""-'-··--( i\ ~" ' •T4al1.IZU• 0:0NS"T .. 1,1(:TH)N l!NTIIU.NCI! ,.. ___ ,._.,A'"" .... ,.-~o,_ • ~.," H·-~-·.-•u .. ~.,,w,~~ .,,,_,.,,, • ~.-·,-, ,,..-~,w, .. ~,-,.~, .... , ~-'''"'°''"'""'""" ~· .,,.,,_, ... , r"'< ~·,· ~·~-.-,,. ,, '• '"''"'' '"'"' ,_,,....,.,,,,_ • ,.,.~ •.. ,,., ... ~·~ .. "' -><,,~ .• -.... , 'l ,.,_,,.,.~><-.>oe>•,a, O"L •~-'-"•""""""-" ,~ • '•'" •V'<"> " ~--,-· ,~,-. ,~,.·,..--······~--~ .. ,c~.-...... -... !l'ro f'UII . .-.~ ,o 4. INSTALL CATCH BASIN PROTECTION IF REQUIRED. 5. GRADE AND INSTALL CONSTRUCTION ENTRANCE($), I ~~) a Pl..ASTtc C-IIINO fl!> l't.ul -tl,:l.:'l'I '<i~ 6. INSTALL PERIMETER PROTECTION (SILT FENCE. BRUSH BARRIER. ETC.) . 7. CONSTRUCT SEDIMENT PONDS AND TRAPS. 8. GRADE AND STABILIZE CONSTRUCTION ROADS. 9. CONSTRUCT SURFACE WATER CONTROLS (INTERCEPTOR DIKES, PIPE SLOPE DRAINS, ETC.) SIMULTANEOUSLY WITH CLEARING AND GRADING FOR PROJECT DEVELOPMENT. 10. MAINTAIN EROSION CONTROL MEASURES IN ACCORDANCE WITH KING COUNTY STANDARDS AND MANUFACTURER'S RECOMMENDATIONS. 11. RELOCATE EROSION CONTROL MEASURES OR INSTALL NEW MEASURES SO THAT AS SITE CONDITIONS CHANGE THE EROSION AND SEDIMENT CONTROL IS ALWAYS lN ACCORDANCE WITH THE KING COUNTY EROSION AND SEDIMENT CONTROL STANDARDS. 12. COVER ALL AREAS THAT WILL BE UNWORKED FOR MORE THAN SEVEN DAYS DURING THE DRY SEASON OR TWO DAYS DURING THE WET SEASON WITH STRAW, WOOD FIBER MULCH, COMPOST, PLASTIC SHEETING OR EQUIVALENT . ' , _I I I I I I I I I I I I I I ...... ~F', (·~·' ~~i ,.,l Tll[fl: '"""'ue ,. .. O"l"l!!CTION m> Pf..,. , '7 ), ,··~-~·" ... -....... , ... -...... -"' .... ,-~-"'"'· ---~,·· ..... . '"'' .. ,,, .. , .. ,~·· -~~~·;,, ,,...,.,. ~-··- -~~--:~ : .. '<d 9-llTFl!:NCI!: ·J·_! . : ' , ' , ' -' ,rm l'I..L• -~:<.OO HORIZONTAL GRAPH1C SCALE 20 10 0 10 20 1 ,nch lU tt II &: • 95.96" ··l ·.·-·· .. , 113. STABILIZE ALL AREAS THAT REACH FINAL GRADE WITHIN SEVEN DAYS. I /\1'88"5i"08w ----1 ----------14. SEED OR SOD ANY AREAS TO REMAIN UNWORKED FOR MORE THAN 30 DAYS. • :c I I 15. UPON COMPLETION OF THE PROJECT, ALL DISTURBED AREAS MUST BE STABILIZED AND BMPS REMOVED IF APPROPRIATE. 5 I - & CALL 48 HOURS BEFORE YOU DIG 1-800-424-5555 JOB NO. s=«o-oc= CENTRAL ISLAND SHORT PLAT Ion E 'll'!ai'El/a 'I"~-'1"~-c f-''" H. ~ =,cn~,aos 3-10-2014 .-.E"" ,!;.II Ii' .lbl).lbl) ;' '<'01 '""7.,;.~, ~=, 1"=20' "~'-'"~"""' 3413 NE 7TH STREET "' Land Planning • Ovll Engineering : J DRA~, "\ ~ RENTON 1 -5130 5 th 166th La H. H. PHAN DATUM :::l OU ne CHECl(f!): OIE INCH . . PAGf DRAWlNGNO· """ rt f i \ H. H. PHAN ~ ~ CITY OF RENTON WA 98056 ' S SeaTac, WA 98188 "-: ".tc4:~fl~ . I ;~~~~ I '-Plarmlng/Bu1ldlng/Publ1c Works Dept. I TESC PLAN AND DETAILS 1; T (206) 229-6422 ~s1111ru -~ Al'l'llOYID se,,u..ccCRJ~v ( 2 5 ( ::i; NO. REVISION BY DATE APPR EC1 • D.3.1 COVER MEASURES D.3.2A PLASTIC COVERI:\"G Cod.;:-: PC Symbol: ---~c)i----- Purpose Plastic coYering pro,ides immediate. sho11-tenn erm,iou protection to .i;,,lopes and disturbed areas. Conditions of Use l. ' ·'. +. Plas.tic co,·ering may be used on dis.turbed areas that require coYer measures for less than 30 days. Pins.tic is. pmtic:ulady useful for protecting cut and fills.lopes and stockpiles .. Vote: The relatfrefr rapid breakdo11·n of most po!n?Th_1'lene sheeting makes tr uns11itab!efor long-tern1 apphcahons. Clear plastic sheeting: may be used o,·er newly-seeded areas. to create a greenhouse effect and encourage grass. gro,,·th. Clea1· plastic should not be u-;ed for th.ii;,, pmpose dming the '.':.mnmer months because the resulting: high temperatlue-. can kill the g:rai;,,s.. Due to rapid nm.off cam,ed by plastic s.heeti.ng. thi<:i method shall not be used upslope of areas that might be adYersely impacted by concenrrated mnoff. Such areas include ~teep andi or unstable <:ilopes. ~Vore: There haw beN1 mm~1· problems ll'ith plmrtc, 11walf1· amibwab!e ro poor instaf latton and maimenance. Hou·e,·er, the material irse!f can cause problems. e,·e,111'11e11 conecrf1· insralled and maimained. beca11'ie tr generates higlH·elocity runoff and breaks do,rn quickfr due 10 u!tral'ioler radiation. In addition. fthe pf{lsfic i'> no/ co111plete(1· remol'ed, it can clog dminage ~ystem inlet5 and ou!lers. It is high~1· reco111me11ded rhat alren,atil'es to plastic sheeting be used 1d1enernrposstbfe and rhar trs use be limited. Design and Installation Specifications l. See Figtue D.3.2.D for detail'>. 2. Plastic sheeting shall h,n-e a mininuun thickness of0.06 millimeters. 3. If erosion at the toe of a slope is likely. a ~ra\"el benn. riprap. or other suitable protection shall be installed at the toe of the slope in order to reduce the ,·elocity of nmoff. FIGl'RE D.3.2.D PLASTIC-CO\"'ERIXG 2009 Surface Water Design Manual -Appendix D D-17 TIRES, SAtlDBAGS, OR EQUIVAL£tfT UAV BE USED TO WEIGHT PUSTIC SEAMS BETWE:EH SME'.rTS MUST OVCRLAP A WINIMUhl OF 12• ,1,HD B[ WEIGHTED OR TAPEO t.'9!2009 SECTION D.3 ESC MEASURES D.3.3 PERil\lETER PROTECTION Perimeter protection to filter <,ediment from sheero;ash shall be located downslope of all disnirbed areas and shall be installed p1ior to upslope grading. Perimeto;r protection include:c:. the use of yeg_etated r,trip::. as well as. constmcted mea':!-ure":.. i:..uch as i:iih fences. fibe1· rolls. i:,.and· graYel baniers. bmsh or rock filters. triangular silt dikes and other methods. Dtuing the 1,.yet season. 50 linear feet of sih fence (and the neces::.ary .stakes) per acre of disnirbed area must be stockpiled on site. Purpose: TI1e pmpose of perimeter protection is to reduce the amount of ,~ediment tn111spo11ed beyond the disnubed areas of the construction site. Perim.eter protection is primarily a bach1p means of sediment control. ?>.lost. if not all. sediment-laden \Yater is to be treated in a sediment trap or pond. The only circumstances in which perimeter control is to be u~ed as a primary means of sediment remoYal is when the catchment is Yery -.mall tsee below). \\"hen to Install: Perimeter protection is to be installed prior to any upslope clearing: and grading. :'.\lensure~ to Fse: The aboYe measures may be used interchangeably and are not the only perimeter protection measures. a,·ailable. If surface water is collected by au interceptor dike or swale and routed to a sediment pond or trap. there may be no need for the perimeter protection meas.ures specified in this section. C1·iteiia for r se as Prhoar~· Treatment: At the bom1da1y of a site. perimeter protection may be used as the sole fonu of treatment when the flowpath meet:, the criteria listed below. If these criteria are not met. perimeter protection shall only be u,;,ed as a backup to a sediment trap or pond. A wrag• Slop• l.'.'H: lV or le'>'> 2H: 1 V or le~~ -4H: 1 V or le~~ 6H: IV or less IOH: IV or less Slope Pel'cent 50°0 or less 25% or lef::.s 10% or less Flowpath L•ngtb 100 feet 115 :feet l'.'O feet 200 feet 250 feet D.3.3.1 SILT FEl'\CE 1/9°2009 Code: SF Symbol: )( )( )( )( )( Purpose Use of a silt fence reducer, the transport of coarse sediment from a constrnction site by providing a temporaty physical ball."ier to sedimem and reducing-the nmoffYelodties of O\"erland flow. Conditions of Use 1. Silt fence may be used downslope of all disturbed area,;,. 2. Silt fence is not intended to treat concentrated flows. nor is it intended to n·eat substantial amounts of oYerland flow. Any concentrated flows must be conveyed through the cirai.uage system to a sediment trap or pond. TI1e only circumstance in which oYerlaud flow may be treated solely by a silt fence. rathe1· than by a sediment trap or pond. is when the area draining to the fence is small (see ''Criteria for Vse as Primary Treatment" on page D-30). Design and Installation Specifications See Figure D.3.3.A. and Figure D.3.3.B for details. 2009 Surface Water Design Manual -Appendix D D-30 D.3.3 PERIMETERPROTECTION The geotextile used must meet the standard~ listed belo\,-. A copy of the manufacturer\ fabric specificmion<,c must be an,ilable on site. AOS (ASTM 04751) 30-100 sieve size (0.60-0.15 mm) for slit film 50-100 sieve size (0.30-0.15 mm) for other fabrics Water Permittivity (ASTM 04491) 0.02 sec-1 minimum Grab Tensile Strength (ASTM 04632) 180 lbs. min. for extra strength fabric 100 lbs. min. for standard strength fabric Grab Tensile Elongation (ASTM 04632) 30% max. Ultraviolet Resistance (ASTM 04355) 70% min . .3. Standard strength fabric requires wire backing to increase the strength of the fence. \Vire backing or closer post spacing may be required for extra ~trength fabric if field perfom1ance warrants a strong-er fence, 4. \\11ere the fence is installed. the slope shall be no steeper than 2H: 1 V. 5. If a typical silt fence (per Figure D.3.3.A) is used. the stand..1rd 4 x 4 trench may not be reduced as long a'> the bottom S inches of the silt fence is well buried and secured in a trench that ':!.tabilizes the fence and does not allow water to bypass or undennine the silt fence. Maintenance Standards I. ' ·'· 4. 5. A.ny damage shall be repaired immediately. If concenrrated flows are eYident uphill of the fence. they must be intercepted and conYeyed to a &ediment trap or pond. It is important to check the uphill side of the fence for signs of the fence clogging. and acting a-5 a baffier to flow and then cau.').i.ng channelization of flows parallel to the fence. If this occun,. replace the fence or remm·e the trapped sediment. Sediment must be remo\·ed wheu the sediment is 6 inches high. If the filter fabric {geotextile) has deteriorated due to ultraviolet breakdown. it shall be replaced. FIGFRE D.3.3.A SILT FE'.\"CE JOINTS iN FlL""ER FABRIC Sr.AL.1.. BE S.PLICEO AT POSTS. US( STAPLE'S. W l~E RINGS, G~ EQUIVALENT TO ATIACH FABRIC TO POSTS. 2'°:,,2" BY 14 Gd. WIRE OR '--====:-EQ . .J:VALENT, IT S'ANDt>.RD CI! S"'"f.:(NGTH FASH':.; USi].l I I I I I I I I I I NOTE: FILTE:R FABRIC FEI\CES SH.A.LL OE lt-.,~TALLED N ... ONG CONlCldR WHE.NEV=."( ross:BLE. FI.JE.R f.Af3Rtc---f N ~~ I " ~'· ~009 Swfa('e Water Design Manual -Appendix D 1/9/~009 D-31 D.H TRAFFIC AREA ST ABILIZAT!ON D.3.4.1 STABILIZED CO'.'ISTRrCTIO'.'I E'.'ITR.A ... ~CE Cod,;:: CE Symbol: Purpose Co11-.tn1ctiou entrances are stabilized to reduce the amom1t of sediment transported onto pa\·ed road.;, by motor ,·elricles. or nmoffby constructing a stabilized pad of qua1Ty spalls at entrances. to con'iitniction sites. Conditions of Use Constmction entrance'i. shall be stabilized whereYer traffic will be le.:ffing a constJ:uction site and tra\·eJing: on payed roads or other pa,·ed areas within 1.000 feet of the site. Access and exib shall be limited to one roure if po!:.:-.ible. or two for linear projects such as roadway where more than one acces.c..:exit i-.. neces,;.ary for manenYering: large equipm.ent. Design and Installation Specifications l. ' 3. ~. See Figure D.3.-1.A for details. A separation geotextile ;hall be placed under the &palls to pre\·ent fine sediment from pmuping up into the rock pad. The geotextile shall meet the following standards: Grab Tensile Strength (ASTM D4751) 200 psi min. Grab Tensile Elongation (ASTM D4632) 30% max. Mullen Burst Strength (ASTM D3786-80a) 400 psi min. AOS (ASTM D4751) 20-45 (U.S. standard sieve size) Hog fuel (wood ba:-,ed mukh) may be snbs.tintted for or combined with quan-y spalls in areas that wilJ not be used for permanent road.s.. TI1e effectivene.;s of hog: fuel is highly variable. but it has been us.ed succe%fully on many site3. It generally require~ more maintenance than quarry spalls. Hog fuel is not reconunended for entrance stabilization in rn·ban areas. The itE,pector may at any time require the use of qnaITy spalls if the hog fuel i'!i not pre\·enting sediment from being tracked onto paYement or if the hog fuel i') being cani.ed onto pa\·ement. Hog fuel i!":. prohibited in pennanent roadbeds because organics it1 the subgrade soils cause difficultie-,. with comp.action. Fencing. { see Section D.3.1) shall be installed as necessary to restrict traffic to the consn1.1ction entrance. 5. \VheneYer possible. the entrance shall be constn1cted on a fmn. compacted subg.:rnde. Thi'i can substantially increase the effectiYene-ss of the pad and reduce the need for niainteuauce. Maintenance Standards I. Qu.any spalls ( or hog fuel) shall be .added if the pad is no longer in accordance with the specifications. If the entrance is not preYenting sediment from being tracked onto p.a\"ement. then altemafo:e measures to keep the -,.treets free of sediment shall be used. This may include street -,.weepit1g:. an increase in the dimensions of the entrance. or the installation of a wheel wash. If washing is used. it shall be done on an area coYered with cmshed rock. and wash water shall drain to a seditneut trap or pond. 2009 Surface Wate-r Des.i_g:n Manual -Appendix D 1(9/2009 D-39 The Concept Group Appendix D Maintenance Procedures Appendices APPD.'DIX A MAIXTESAXCE REQllRHIEJ\"TS FLOW COSTROL. CO'.\"\'EYAJ\"CE. i\SD WQ FACILITIES 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. Inlet/outlet pipes clear or sediment accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). Damaged Cracks wider than Yi-Inch at the joint of the No cracks more than 'Y..-inch wide at lnletioutlet pipes or any evidence of soil entering the joint of the inletloutlet pipe. at the Joints of the Inlet/outlet pipes. Access ManhOle Coverilid 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 coverilid does not work. Cover/lid d!fficult to One maintenance person cannot remove Cover/lid can be removed and remove coverllld after applying ao lbs of lift. relnstalled 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 ii 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 1 /1 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 or 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 Splllway restored to design Emergency Overflow area five square feet or larger, or any exposure of standards. Splllway 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 stablllty of Trees removed. spillway. 119/:!009 :!009 Surface Water Design Manual~ Appendix A A·4 ----- • Group N_orthwest, Inc. August 6, 2014 Mr. Thuong (Tom) Pham Central Island Landscape 3556 -120 .. Ave SE Bellevue, WA 98006 SUBJECT: GEOTECHNICAL ENGINEERING STUDY PROPOSED SHORT PLAT 3413 NE 7"' STREET RENTON, WASHINGTON Dear Mr. Pham: Geotechnical Engineers, Geologists & Environmental Scientists G-3710 GEO Group Northwest, Inc., has prepared the following geotechnical report for the proposed residential development based upon our subsurface investigation at the site. This work was performed in accordance with our contract with you dated July 16, 2014. GEO Group Northwest, Inc., explored the subsurface soil conditions at the site by directing the excavation of four exploratory test pits on July 23, 2014. Soils encountered at the test pits TP-1 through TP-3 consist of very loose to dense gravelly and fine silty SAND soils overlying dense silty SAND soils at depths ranging from 3.5 to 6 feet below ground surface. Some apparent fills were present within the overlying loose soil zone at these test pits. At the test pit TP-4 location the dense silty SAND soils with some gravel overlie the very dense gravelly silty SAND soils at a depth of 3-feet below ground surface. Based on the results of our study, it is our professional opinion that the site is geotechnically suitable for the proposed development. The proposed buildings can be supported on conventional spread footings bearing on the dense native in-situ site soils or on compacted structural fill placed on top of the dense native soils. The overlying loose site soils and fills are not suitable to support foundations due to their loose and variable condition. Based on the findings from our soil investigation at the site, we anticipate that over-excavation and replacement with compacted structural fills will likely be required at the southern two lots. The amount of over-excavation is not currently known since proposed foundation elevations were not available at the time of report preparation. Please refer to the text of the report for more specific recommendations regarding the site development. 13240 NE 20th Street, Suite 10 • Bellevue, Washington 98005 Phone 425/649-8757 • Fax 425/649-8758 GEOTECHNICAL ENGINEERING STUDY PROPOSED SHORT PLAT 3413 NE 1fH STREET RENTON,WASHINGTON G-3710 Prepared for Mr. Thuong (Tom) Pham Central Island Landscape 3556-120th Ave SE Bellevue, WA 98006 August 6, 2014 GEO GROUP NORTHWEST, INC. 13240 NE 2Qlh Street, Suite 10 Bellevue, Washington 98005 Phone: (425) 649-8757 Email: wchang@geogroupnw.com or agaston@geogroupnw.com August 6, 2014 Proposed Short Plat, 3413 NE 7fh St, Renton, Washington G-3710 Page ii We appreciate this opportunity to have been of service to you on this project. We look forward to working with you as this project progresses. Should you have any questions regarding this report or need additional consultation, please feel free to call us. Sincerely, GEO Group Northwest, Inc. William Chang, P.E. Principal GEO Group Northwest, Inc. TABLE OF CONTENTS JOB NO. G-3710 Page 1.0 INTRODUCTION . , .................................................... 1 1.1 Project Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Scope of Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2.0 SITE CONDITIONS .................................................... 2 2.1 Site Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.2 Geologic Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.3 Field Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.4 Soil Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.5 Groundwater Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.0 SEISMIC CONSIDERATIONS ........................................... 3 4.0 CONCLUSIONS AND RECOMMENDATIONS ............................. 3 4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4.2 Site Preparation and General Earthwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.2.1 Temporary Excavation and Slopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.2.2 Structural Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.3 Spread Footing Foundations ......................................... 6 4.4 Permanent Basement and Conventional Retaining Walls ................... 8 4.5 Slab-on-Grade Floors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.6 Footing Drains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4. 7 Pavements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l 0 S.O LIMITATIONS . . . . • . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 6.0 ADDITIONAL SERVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 ILLUSTRATIONS Plate 1 Plate 2 Plate 3 APPENDIX A: -Site Vicinity -Site Plan -Typical Footing Drain Detail TEST PIT LOGS AND SOIL LEGEND GEO Group Northwest, Inc. GEOTECHNICAL ENGINEERING STUDY PROPOSED SHORT PLAT 1.0 INTRODUCTION 1.1 Project Description 3413 NE 7m STREET RENTON,WASHINGTON G-3710 The project site is located at the southern side of NE 7111 Street in Renton, Washington at the subject address. The subject parcel consists of a 0.6 acre lot which is currently occupied by a two-story single family residence. The existing residence is located adjacent to the northern property line, fronting NE 7111 Street. At the time of our investigation the remainder of the southern portion of the lot was vacant and generally flat or having gentle slopes, except for near the western property line where a west-facing moderate slope has an estimated height of up to 6- feet. Several piles of yard trimmings were located at the site. These were especial! y evident along the western side of the lot and near the southwestern corner of the lot. The existing building is shown on the attached Plate 2 -Site Plan. Based upon the Plate 2 -Site Plan and information provided by the owner, Mr. Thuong Pham, we understand that the current project parcel is proposed to be subdivided into four new lots. The existing house will remain on the northernmost of the new lots. Wood-framed single family residences are proposed to be constructed near the center of the three new southern lots. A new access road is proposed to be located at the eastern side of the project parcel. 1,2 Scope of Services The tasks we completed for this study were conducted in general accordance with the scope of work presented in our contract dated July 16, 2014. The results of our subsurface investigation and our recommendations regarding the proposed development are summarized in the following report. GEO Group Northwest. Iuc. August 6, 2014 Proposed Short Plat, 3413 NE 7th St, Renton, Washington 2.0 SITE CONDITIONS 2.1 Site Description G-3710 Page2 The site consists of 0.6 acre parcel occupied with one single family residence. The existing building is located at the northern side of the lot and the southern portion of the lot is undeveloped. Existing conditions are shown on the attached Plate 2 -Site Plan. 2.2 Geologic Overview According to the geologic map for the site vicinity the soils at the site are reported to be Vashon Till (Qvt). The Vashon Till soils consist of a mixture of sand, silt and gravel, which was consolidated by overriding glacial ice. These soils can usually be divided into a surficial loose to medium dense weathered zone which overlies the dense to very dense underlying un-weathered till soils. 2.3 Field Investigation GEO Group Northwest, Inc., explored subsurface soil conditions at the site by directing the excavation of 4 exploratory test pits and Jogging the observed soil conditions on I ul y 23, 2014. The test pits were excavated by the owner using a small mini-hoe. The test pits were located near the proposed development areas, as shown on Plate 2 . Site Plan. The test pits were excavated to depths ranging between 4 and 6 feet below ground surface (bgs). The observed soil and groundwater conditions were logged. The test pits were then backfilled with the excavated site soils. Backfilled soils were not compacted. An attempt was made to locate the test pits outside of the building areas, however, it is probable that test pit TP-2 was located within the building area and other test pits may be as well, dependent upon the final location of the new houses. We recommend that loose fills placed at test pit locations be re- excavated and re-placed and compacted to meet structural fill specifications (below) prior to the construction of any structures, foundations or slabs. GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7rh St, Renton, Washington 2.4 Soil Conditions G-3710 Page3 Soils encountered at the test pits TP-1 through TP-3 consist of very loose to dense gravelly and fine silty SAND soils overlying dense silty SAND soils at depths ranging from 3.5 to 6 feet below ground surface. Some apparent fills were present within the overlying loose soil zone at these test pits. At the test pit TP-4 location the dense silty SAND soils with some gravel overlie the very dense gravelly silty SAND soils at a depth of 3-feet below ground surface. The dense to very dense soil conditions observed at the test pit TP-4 location matched the description for the anticipated Vashon Till soil deposit. Copies of the Test Pit Logs are presented in Appendix A: Test Pit Logs. 2.5 Groundwater Conditions No groundwater seepage was encountered at the test pits. It should be noted that groundwater conditions may fluctuate seasonally, depending on rainfall, surface runoff and other factors. 3.0 Seismic Considerations Based upon our subsurface investigation at the site, it is our opinion that the project buildings may be designed using the Class C soil profile per the International Building Code. It is our opinion that the soils at the project site are not susceptible to liquefaction, due to the absence of groundwater within the loose soil zone. 4.0 CONCLUSIONS AND RECOMMENDATIONS 4.1 General Based upon the results of our study, it is our professional opinion that the site is geotechnically suitable for the proposed development. The proposed buildings may be supported on conventional spread footings bearing on the dense native site soils or on compacted structural fill placed on top of the dense native site soils. The overlying loose site soils are not suitable to support foundations. We anticipate that the dense soils are located at depths ranging from 3.5 feet to 6 feet below ground surface (bgs) at the southern portion of the site. Dense soils may be GEO Group Northwest. Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7th St, Renton, Washington G-3710 Page4 located near the ground surface at the northern portion of the site. We anticipate that a significant amount of over-excavation will likely be necessary for at-grade foundations located at the southern-most two Jots. We recommend that GEO Group Northwest, Inc., is on-site at the time of foundation excavation to verify that subgrades consist of the dense native soils and that replacement structural fills are properly compacted as specified in this report. It is also important to note that mapping of our test pits indicates that some test pits may have been located at areas where proposed buildings or pavements are to be located. No compaction was performed at the time that the test pits were backfilled. Therefore it is anticipated that the fills at the test pit locations will be loose. We recommend that the contractor plan on over- excavating and placing compacted structural fill at any test pit locations which are located at pavement or building locations. GEO Group Northwest, Inc., can be on-site at the time of grading and building pad preparation to aid in locating test pit locations and overseeing the subgrade repair work. 4.2 Site Preparation and General Earthwork The building pad areas should be stripped and cleared of landscaping clippings, surface vegetation and topsoil. Silt fences should be installed around areas disturbed by construction activity to prevent sediment-laden surface nmoff from being discharged off-site. Exposed soils that are subject to erosion should be compacted and covered with plastic sheeting. 4.2,I Temporary Excavation and Slopes Under no circumstances should temporary excavation slopes be greater than the limits specified in local, state and national government safety regulations. Temporary cuts greater than four feet in height should be sloped at an inclination no steeper than IH: IV (Horizontal: Vertical) in the loose site soils. Temporary cuts in the dense site soils may be excavated no steeper than IH:2V provided that no seepage is encountered. If groundwater seepage is encountered during construction, excavation of cut slopes should be halted and the cut slopes should be re-evaluated by GEO Group Northwest, Inc. If necessary the underlying very dense soils may be capable of standing at steeper inclinations such as IH:3V, however, this is dependent upon the conditions at the time of excavation. If it is necessary to form such steep excavation slopes than GEO Group Northwest, Inc., must be retained to evaluate the conditions at the excavation at the time of grading to provide an evaluation of stability. If the proposed temporary excavation slopes GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7th St, Renton, Washington G-3710 Page5 encroach upon adjacent properties then it may be necessary to obtain an excavation easement or plan for temporary shoring at those locations. Permanent cut and fill slopes at the site should be inclined no steeper than 2H: 1 V. Surface runoff should not be allowed to flow uncontrolled over the top of slopes into the excavated area. During wet weather exposed cut slopes should be covered with plastic sheeting during construction to minimize erosion. UJ. Structural Fill All fill material used to achieve design site elevations below the building areas and below non- structurally supported slabs, parking lots, sidewalks, driveways, and patios, should meet the requirements for structural fill. During wet weather conditions, material to be used as structural fill should have the following specifications: 1. Be free draining, granular material containing no more than five (5) percent fines (silt and clay-size particles passing the No. 200 mesh sieve); 2. Be free of organic material and other deleterious substances, such as construction debris and garbage; 3. Have a maximum size of three (3) inches in diameter. All fill material should be placed at or near the optimum moisture content. The optimum moisture content is the water content in soil that enables the soil to be compacted to the highest dry density for a given compaction effort. The majority of the surficial site soils will be moisture-sensitive because they consist of fine silty SAND soils. The site soils' moisture sensitivity may make them unusable as structural fill if they are to be placed/compacted as structural fill during the wetter portions of the year. Alternatively, an imported granular fill material may provide more uniformity and be easier to compact to the required structural fill specification. If the on-site soils are to be used as engineered structural fill, it will be necessary to segregate the topsoil and any other organic-or debris-containing soil, because such soils would be unsuitable GEO Group Northwest. Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7th St, Renton, Washington G-3710 Page6 for use as structural fill. Excavated on-site material that is stockpiled for later use as structural fill should be protected from rainfall or contamination with unsuitable materials by covering it with plastic sheeting until it is used. Structural fill should be placed in thin horizontal lifts not exceeding ten inches in loose thickness. Structural fill under building areas (including foundation and slab areas), should be compacted to at least 95 percent of the maximum dry density, as determined by ASTM Test Designation D- 1557-91 (Modified Proctor). Structural fill under driveways, parking Jots and sidewalks should be compacted to at least 90 percent maximum dry density, as determined by ASTM Test Designation D-1557-91 (Modified Proctor). Fill placed within 12-inches of finish grade should meet the 95% requirement. We recommend that GEO Group Northwest, Inc., be retained to evaluate the suitability of structural fill material and to monitor the compaction work during construction for quality assurance of the earthwork. 4.3 Spread Footing Foundations The proposed buildings can be supported on conventional spread footings bearing on the dense native site soils or on compacted structural fill placed on top of the dense native site soils. Based on the findings from our soil investigation at the site, we anticipate that the dense soils are present at depths between 3.5 and 6 feet below ground surface (bgs) at the southern portion of the site. Over-excavation and placement of structural fill is anticipated at some of the foundation locations, dependent upon the proposed finish grades and the conditions encountered at the building foundation excavations. We recommend that GEO Group Northwest, Inc., be retained to verify competent soils are present at each building foundation location, at the time of construction, prior to the foundation pour(s). Individual spread footings may be used for supporting columns and strip footings for bearing walls. Our recommended minimum design criteria for foundations bearing on the dense site soils or on compacted structural fill are as follows: GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7th St, Renton, Washington -Allowable bearing pressure, Dense native soil Compacted structural fill including all dead and live loads = 2,000psf =2,000psf G-3710 Page? -Minimum depth to bottom of perimeter footing below adjacent final exterior grade = 18 inches -Minimum depth to bottom of interior footings below top of floor slab = 18 inches -Minimum width of wall footings = 16 inches -Minimum lateral dimension of column footings = 24 inches -Estimated post-construction settlement= 1/4 inch -Estimated post-construction differential settlement; across building width= 1/4 inch A one-third increase in the above allowable bearing pressures can be used when considering short-term transitory wind or seismic loads. Lateral loads can also be resisted by friction between the foundation and the supporting compacted fill subgrade or by passive earth pressure acting on the buried portions of the foundations. For the latter, the foundations must be poured "neat" against the existing undisturbed soil or be backfilled with a compacted fill meeting the requirements for structural fill. Our recommended parameters are as follows: -Passive Pressure (Lateral Resistance) • 350 pcf equivalent fluid weight for compacted structural fill • 350 pcf equivalent fluid weight for native dense soil. -Coefficient of Friction (Friction Factor) • 0.35 for compacted structural fill • 0.35 for native dense soil GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7th St, Renton, Washington G-3710 Page8 We recommend that footing drains be placed around all perimeter footings. More specific details of perimeter foundation drains are provided below in Section 4.6 -Footing Drains. 4.4 Permanent Basement and Conventional Retaining Walls At the time of report preparation finish grades for the proposed development were not shown on the site plan. We anticipate that little site grading is proposed and that the new construction will be primarily at-grade. The site plan does not indicate whether or not any retaining walls will be constructed. The following design recommendations may be used for permanent basement and conventional retaining walls at the project site, if necessary. Foundations for all retaining walls should be founded on the dense in-situ site soils or compacted structural fill placed on top of the competent site soils as discussed above in the Section 4.3 -Spread Footing Foundations. Permanent basement walls restrained horizontally on top are considered unyielding and should be designed for a lateral soil pressure under the at-rest condition; while conventional reinforced concrete walls free to rotate on top should be designed for an active lateral soil pressure. Active Earth Pressure Conventional reinforced concrete walls that are designed to yield an amount equal to 0.002 times the wall height, should be designed to resist the lateral earth pressure imposed by an equivalent fluid with a unit weight of 35 pcf for level backfill. At-Rest Earth Pressure Walls supported horizontal! y by floor slabs are considered unyielding and should be designed for lateral soil pressure under the at-rest condition. The lateral soil pressure design should have an equivalent fluid pressure of 45 pcf for level ground behind the walls. Passive Earth Pressure and Base Friction The available passive earth pressure that can be mobilized to resist lateral forces may be assumed to be equal to 350 pcf equivalent fluid weight in both undistwbed soils and engineered structural backfill. GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7fu St, Renton, Washington The base friction that can be generated between concrete and undisturbed native soils or engineered structural backfill may be based on an assumed 0.35 friction coefficient. Drainage G-3710 Page9 Based upon the subsurface investigation no groundwater seepage was encountered at the test pit locations which extended to depths ofup to 7-feet below ground surface (bgs). If excavations extend deeper than this, such a for detention vaults or full-height basements then seepage may be encountered. If seepage is encountered then GEO Group Northwest, Inc., should be retained to evaluate and provide updated recommendations for the un-anticipated conditions. We recommend that a vertical drain mat, Miradrain 6000 or equivalent, be used to facilitate drainage behind permanent concrete basement and conventional retaining walls. We recommend that the drainage mat be installed on the back side of the wall extending from the finish grade down to a footing drain pipe. The wall footing drain pipe should consist of a 4-inch diameter perforated rigid PVC pipe surrounded by a bed of washed gravel and separated from site soils by filter fabric, Mirafi 140N or equivalent. The drain pipe should be tightlined to discharge to the stonnwater system. Backfill behind conventional retaining walls should consist of free-draining sand or gravel soils which are compacted in lifts. Backfill in areas adjacent to basement or conventional retaining walls should be compacted with hand held equipment or a hoepack. Heavy compacting machines should not be allowed within a horizontal distance to the wall equivalent to one half the wall height, unless the walls are designed with the added surcharge. 4.5 Slab-on-Grade Concrete Floors Loose site soils should be excavated from all concrete slab subgrade areas or compacted to a firm and unyielding condition. Slab-on-grade concrete floors may be constructed on top of medium dense to dense native site soils or on top of compacted structural fill placed on top of the competent site soils. The slab-on-grade floors should not be constructed on top of loose soils. A significant thickness of loose and very loose soils are anticipated at the southern two building lots based upon our subsurface investigation. Therefore, we recommend that if concrete slabs are proposed at these areas, then at minimum the slab subgrade areas should be over-excavated to 2- feet below the proposed slab subgrade elevation, the subgrade compacted to a firm condition and GEO Group Northwest. Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Washington G-3710 Page 10 then structural fills placed up to the proposed slab subgrade elevation. GEO Group Northwest, Inc, should be retained to verify appropriate over-excavation and placement of compacted structural fills at these areas. If medium dense to dense soils are encountered at the slab subgrade then the over-excavation is not necessary, provided the GEO Group Northwest, Inc., verifies competent soil conditions at the time of construction. To avoid moisture build-up on the subgrade, slab-on-grade floors should be placed on a capillary break, which is in tum placed on the prepared subgrade. The capillary break should consist of a minimum of a six (6) inch thick layer of free-draining crushed rock or gravel containing no more than five (5) percent finer than the No. 4 sieve. A vapor barrier, such as a 10-mil plastic membrane, is recommended to be placed over the capillary break beneath the slab to reduce water vapor transmission through the slab. Two to four inches of sand may be placed over the barrier membrane for protection during construction. 4.6 Footing Drains We recommend that drains be installed around the perimeter of the foundation footings. The drains should consist of a four (4) inch minimum diameter perforated rigid drain pipe laid at or near the bottom of the footing with a gradient sufficient to generate flow, as schematically illustrated in Plate 3 • Typical Footing Drain Detail. The drain line should be bedded on, surrounded by, and covered with a free-draining rock, pea gravel, or other free-draining granular material. The drain rock and drain line should be completely surrounded by a geotextile filter fabric, Mirafi 140N or equivalent. Once the drains are installed, the excavation should be backfilled with a compacted fill material. The footing drains should be tightlined to discharge to the stonnwater collection system. Under no circumstances should roof downspout drain lines be connected to the footing drainage system. All roof downspouts must be separately tightlined to discharge into the storm water collection system. We recommend that sufficient cleanouts be installed at strategic locations to allow for periodic maintenance of the footing drains and downspout tightline systems. 4. 7 Pavements Based upon the site plan we understand that a new private access roadway will be constructed at the site. The adequacy of pavements is strictly related to the condition of the underlying GEO Group Northwest, Inc. August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Washington G-3710 Page 11 subgrade. We recommend that all pavement subgrades be compacted by several passes of a large vibratory drum roller prior to placement of the crushed rock base. Before paving, we recommend that the subgrade be proof-rolled under the supervision of the geotechnical engineer to verify that the subgrade is firm and unyielding at the time of paving. The proof-roll may be performed by driving a fully loaded dump truck over the subgrade areas. If loose or yielding soils are encountered it may be necessary to over-excavate and replace with compacted structural fill in some areas. For firm and unyielding native subgrade soils we recommend the following minimum pavement sections for driveways: Class "B" Asphalt Concrete (AC) Crushed Rock Base (3/4-inch minus) Or Concrete Pavement Crushed Rock Base (3/4-inch minus) 3 inches 6 inches 6 inches 4 inches We understand that it may be beneficial to install a base pavement layer such as ATB (Asphalt- Treated Base) prior to completion of the project. Oftentimes this can help protect the subgrade from construction impacts and reduce cost related to sub grade repairs during wet weather periods. Consequently we have calculated that the 3-inches of AC over 6-inches of Crushed Rock Base noted above would be equivalent to the following total pavement thickness: Class "B" Asphalt Concrete (AC) Asphalt Treated Base (ATB) Crushed Rock Base (3/4-inch minus) 2 inches 4 inches 3 inches In accordance with the Washington State Department of Transportation Construction Manual, transverse cracks will develop in concrete slabs at about 15 foot intervals along the length of slabs and a slab wider than 15 feet may crack longitudinally. To control cracking of the concrete, contraction joints should be installed. Contraction joints are weakened planes which collect the cracking into a controlled joint, creating a maintainable joint in the slab, and preventing random ragged cracks which spread and require expensive n1aint,,,r1J.nce_ \Ve recommend that contr:iction and construction joints be connected wit11 #5 dowel bars, 30 inches long, l 8 inches oo center The contraction joints ,hould be placed at maximum 14 foot intervals. GEO Group Northwest, Inc. -- August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Washington 5.0 LIMITATIONS G-3710 Page 12 This report has been prepared for the specific application to this site for the exclusive use of Mr. Thuong (Tom) Pham of Central Island Landscape and their authorized representatives. We recommend that this report be included in its entirety in the project contract documents for use by the contractor. Our findings and recommendations stated herein are based on field observations, our experience and judgement. The recommendations are our professional opinion derived 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 and within the budget constraint. No warranty is expressed or implied. In the event the soil conditions are found to vary during site excavation, GEO Group Northwest, Inc. should be notified and the above recommendation should be re-evaluated. 6.0 ADDITIONAL SERVICES We recommend that GEO Group Northwest Inc. be retained to perform a general review of the final design and specifications of the proposed development to verify that the earthwork and foundation recommendations have been properly interpreted and implemented in the design and in the construction documents. We also recommend that GEO Group Northwest Inc. be retained to provide monitoring and testing services for geotechnically-related work during construction. This is to observe compliance with the design concepts, specifications or recommendations and to allow design changes in the event subsurface conditions differ from those anticipated prior lo the start of construction. We anticipate the following construction monitoring inspections may be necessary: 1. Site clearing and grubbing; 2. Over-excavation and structural fill placement at building foundation locations: 3. V crification of bearing soil conditions for foundations; GEO Group Northwest, Inc. • ---- , August 6, 2014 Proposed Short Plat, 3413 NE 7"' St, Renton, Wawiugton 4. Structural fill placement and compaction; 5. Slab-on-grade preparation; 6. Subswface drainage installation; 7. Proof-rolling of pavement subgrade areas. G-3710 Page 13 We appreciate this opportunity to have been of service to you on this project. We look foiward to worlting with you as this project progresses. Should you have any questions regarding this report or need additional consultation, please feel free to call us. Sincerely, GEO Group Northwest, Inc. 11~41r- AdamGaston Project Engineer William Chang, P.E. Principal GEO Group Northwest. Inc. ILLUSTRATIONS G-3710 GEO Group Northwest, Inc. e SCALE: NTS DATE: 8-6-14 MADE: AG VICINITY MAP 3413 NE 7TH ST RENTON,WASHINGTON JOB NO.: G-3710 PLATE: 1 9·0\\ l..."-e,'f, c;·o\\ l.,.'f'l ,'-r.(?..~ ,.. .. c;. \!' ..... ~~ 08 (~) .ro·9s {tc1),s i ·se M.££',80.00N ~ -:. <. -0 ~\ CS' '3, ~ ~ 7 <.~ ~q ...l'3, ~ ' \ = 60.02 6 j / 298.88' (M) 92.67' =--I'" . "~a( -------- (JI N00'09' 46.W == 10.00· ,-~~? r ·~ q C!. !"l - I dl o.,., "o. <o,. 'o.1: > qS' I I I I z I m ,., I ~ I I -,J -f LOT J C-__ 2~ BAC..$TP-4 ~ ii~~ ) t1I ~ o tuiz ~ • LOT 2 -::1,r -10 ~ ~ 20' BAO< _ -_ _r,,.,: kit--TP-1 --Vl . ,rg I ' ~ I d ~ l • ,·1 J ~~ I \ \ \ \ \_ -·------ 00 0 "'" ...., _. (JI g Q) • 0"1i ~ ..: ~ (I).... "' 6,708 SF./PAE P> I I~ I P>§~. ~~~ , § ~fqa;P-2 r~ _ -,5' F7i'$T-_} ? ~~ ~ / J 47.67' TP-34') 8,890 SF./PAE 5,706 SF. 4,757 SF. I \_ ______ _J O> !O 15' FRONT fD ul 44.90' j i~ ........ ~-<o t -...., . 0 l ~~~ co ...., ... ,., "'"'i .... co ? ~~~~~~'----',.~~~~~~~~~~~ I ' ? ' ...J i-15'FRONT $ PU,UL ·=-~"~'= --NN O'! (J1 ' !~ i:» i LEGEND "' ~ ?3~23' ,,~ ~-=»--=··= _ _ 82.67' -j'.'' N00'09'54~W • _ _ 152.83' _I_ 20' N00'09 154TW · ~ ,~,~ @ . -~ PRIVATE ACCESS EASE;MQ!J. (PAEJ.fOR. EGRE~~-r-)!,NGfiESS ,l,JJJ!l.l]IS -1- 0 .~ S00'09'54~E 298.81 M ~~~~/~ (I i I I I , ... -- , ::0 ~ f ffl "' ~ 1 ii ,.. ,-,-,.. 0000 1 ~~"'"i~ .... <.., I',) -it N M U b ~t:::i ,~ SITE PLAN \ .1 , !J~~~~~'oP~ !~,~,~~T PLAT I -5t-= TEST PIT NUMBER AND APPROXHviA TE LOCATION PROPOSED SHORT PLAT 3413 NE 7TH ST 1 .. _r, -~ nprr,.J("-('i 1r ·-;., 211.:.;,. ~~ . ~ µ RENTON, VI} .. S,}ITNCt· ·._:-1'-.: :r C/J -f I ;::o m m -, . I ·-,. I ,., I ····\,, --, ...... j -'Sc."" I ''i J ri1 ,~~-t~ r~ I ><fl.lo~ S';f~ I I i PROJECT#: G-3710 DATE: 7-23-14 ' I ~ ~ ;J H ~ ;'.\ j ~ ,, .. ( ,..i '.'j DRAWN: AG CHECKED: we ____ .ll ;_;s;C::;).!] .. >'.l:. i ., ~ru1 info@geogroupnw.com -II -.ll.i£1dbJ&.E4&L?--,'..&b1.s.1,:.....0-':-_-; _::;;c_;;:_;-..:lli!i*~ ezm .. .lP-BY..$,,".:"£,,:~..:., __ .. ~~~.:~~~«"l.f.C;,. -.-.~;i':ffi_'". ·;31:.'. ... ~.c:.•ir-.:fr.::·.?:'" ~--:.;;.'!I',,~-!,[:_::-~----' .. :,;;::~~,:.w;,;,::h ... m· .. -a'""""::::C::.~,-.. ::-3:'3'!3f5'"7:Ti'"lif8"'."~~~:-. -,.,;.;:::~• • L-.c-:"·· ----. ~ ~--· ,.,, t /--\ ~ ~'.~--· ___ -1--;.:::·,'."._~--~H-~---~ ~----· ,Ji BACKFILL WITH COMPACTBD NATIVE SOIL GEOTEXTILE FILTER FABRIC, MlRAFI 140N OR EQUN ALENT FREE DRAINING BACKFILL CONSISTING OF WASHED ROUND ROCK OR CRUSHED ROCK MINIMUM 4 INCH DIAMETER PERFORATED PVC PIPE LEVEL OR WITH POSITTVE GRADIENf TO DISCHARGE NOTES: l 6" to 12" l NOT TO SCALE I.) Do not replace rigid PVC pipe with flexible corrugalcd plastic pipe. 2.) Perforated or sloUcd PVC pipe should be tight jointed and laid with perforations or slots down, with positive gradient to discharge. 3 .) Do not connect roof downspout drains into the footing drain lines. Ill TYPICAL FOOTING DRAIN DETAIL PROPOSED SHORT PLAT SCALE NONE DATE 815114 IIADE AG CHKD WC 3413 NE 7TH ST RENTON,WASIIINGTON JCB NO. G-3710 PU.TE 3 • APPENDIX A: TEST PIT LOGS G-3710 • LEGEND OF SOIL CLASSIFICATION AND PENETRATION TEST UNIFIED SOIL CLASSIFICATION SYSTEM (USCS) MAJOR DM&ION OROUP nPIClol. DE8CRll'T10N LAIIORATORV CUSSlflCATION CRITERIA BYIIBOL GW WEU. GRADED GRAVElS. GRAYEl-sA.ND Cu• (D60/ 010) ;fNklf than 4 CLEAN MIXTURE. um..E OR NO ANES Ce• (030:2) / (010 • 060) between 1 and 3 GRAVELS DETERMNE PERCENTAGES OF GRAVELS ("11eon,o GP POOAt.Y GRADED GRAVELS, Af«>GRAVEL-sANO GRAVEL AND SAND NOT~ A.f!£NE REOLNREt.ENTS (More Than Halt -) MXTURES UTTl.E OFI NO ANES FROM GRAIN SIZE COARSE· ComeG-[)ISlllfEIUTlON GRAINED SOILS Larger 1han No. 4 C\IA\/E ATTERBERG LIMITS BEi.OW -) DIRTY GM SIL TY GRAVELS, GFIAVEL-sA.NO-SIL T MIXTURES "A"UNE. GRAVELS OON1cNT or P.l. LESSTHAN4 OFRNES ,-..... Cl.AVEY GRAVELS, GAAVEL-8AND-CLAY EXCEEDS 12% ATTERBERG UWfS A8CWE -) GC M>0U<ES CCWISE GRAINED "A"UNE. SOIISARE Cll' P.I. MORE THAN 7 CLASSIRED AS SANOS SW WEU. GRADS) SANOS, GRAVELLY SANDS. UITLE FOLLOWS, CU• (060 f D10) giNlef than 8 Cl.EAN OR NO FINES Cc: (oocr') / (010 • 080) betweel'l 1 lf'ld 3 SANOS (Mon, Thon Half POORLY GP.ADEO SANOS, GRAVELL. Y SANOS, eomea.v. _ .... SP o: 5% Ant Gfarlect: NOT MEETING AI!JCNE REWAEMENTS Mote Than Hall' by &naler Than No. 4 -) lJTTLE 0A NO ANES GW,GP,SW,SP W ..... Lmge< ThOnNo. 200 -) AllERBEAG UWfS BELOW -· DIRTY SM SILT'V $ANOS, SAND-SILT MXRIRES > 12% Fine Gfainecl: "A'UNE SANOS GM. GC, SM, SC COHTENTCF Vllllh P.1. l.ESS TI-Wt 4 ANES _ ...... 5to 12%.Flnt EXCEEDS 12" ATTERBERG uwrs ABOVE -) SC CLAYEY SANDS, BAfE-CLAY YXTUFIES Gnlinea: UM dual "A"UNE -WIit! P.1. MlRE" THAN 7 ...... Limit ... INORGANIC SIL TS, ROCK FLOUR, SANDY SILTS SILTS <50% OF SUGHT Pl.ASTICITV "" (BelowA-1..neon Pl.AS1lCllY CHART /, ,/uWJ V -""""' r-, ANE-GRIJNED --) ...... Uml INOFIGANIC SILTS, Pe9CACEOUS OR 00 FOR SOIL PASSING I I SOILS ,..,.. MH CNA.Tc»MOEOU5. FINE SANJYOA SILTY SOIL N0.40SIEVE I I / l CH"OH ...... -INORGAHICCl.AYSOFL.OWPl.ASTIQTY, ~ <IQ ClAVS CL GRAVB.1..Y, SANOY, OR SILTY CLAYS, ClEM1 I <30% ClAVS I (~~on ~ -""""· I 30 --) ............ CH INOAllANC a.A VS OF Hk1H PLASTICITY. FA. T I J > 50% ct.AVS J ClotOL ~ Thon Half., 211 J ,, w...,...,_ ...... ...,,. OI. ORGANIC stlTS AND OOGANfC SILTY CLAYS OF ,I MH0<0H Than No.200 ORGANIC StL TS & <50% LOW PUST1C1TY 10 I I ' ,.._ ..... ClA\'8 7 PL ... (Below Mile on 4 , -Chart) ........... OH ORGANIC Cl.A VS OF HIGH PlASTICl1Y 0 >50% 0 10 211 30 .. " "" 70 .. 90 100 110 LIQUID LIMIT {%) HIGHLY ORGANIC SOil.$ P1 PEAT Ml> OTHER tlGl-l.Y ORGANIC SOILS SOL PARTICLE SIZE GENERAL OtlDANCE OF SOIL ENGi d ta PIIOP&RTID PIIOM STANDARD PENE1'U1JON TEST (8P1) U.S. STANDMII IIEVE FRACTION -... -UNDVSOILS SILTY & a.AVEY SOILS ----........... ----(mm) (nwn) ""'° ---ca.... --A.TICLAY l200 0.070 N " ........ N Qu."' -0·4 0 ·15 v..,..__ <2 < 0.2.5 ....... ANE ... ...... l200 0-075 4-10 15·35 28·30 .__ 2·4 D.25 • 0.50 ... -110 2 ... ...... 10-30 ..... 28·35 -""""' 4-8 0.60 • 1.00 --COAASE .. 4.75 110 2 30·50 ...... ,. ... DonH 8-15 1.00-2.00 ... ->50 85-100 ..... v,..0onoe 15-30 2.00-4.00 v.., ... ANE 19 .. 4.75 • 30 ..... -CCWISE ,. 19 CONU8 711m1 to 203 mm • Groue Northwest2 Inc. >203mm IIOUl.Ol1R& ----.-.& IIDCI< 6w~Sci1nt11t& , 711mm MHI "" 13240 NE 20lh SttNt. Suile 10 BeletN!t, WA 98005 IIOC1( >-0. 711 ~ meler In VClu'l'llt Pt'lona ("25) MN757 Fax (425) 649-8758 PLATE A1 . ' TEST PIT NO. TP-1 LOGGED BY AG TEST PIT DATE: 01n312014 DEPTH SAMPLE w-OTHER TESTS/ It. uses SOIL DESCRIPTION No. "" COMMENTS At ground surface -pile of organic debris (landscaping material) and -bricks -Tan ftne silty SAND with cobble and gravel, dry, very loose to loose Probe 18' SM -Probe 15' - 5 ProbeS-18" -Probe~' ----1-... ---· --------------------------------------------------· Probe3-4' SM Brown fme silty SAND with gravel, moist, medium dense to dense -Total depth of test pit = 7' below ground surface (bgs) -No groundwater seepage eocouotered 10 _ Competent native soils encouotored at 6' bgs - - - - 15 _ TEST PIT NO. TP-2 LOOQEDBY AG TEST PIT DATE: 07t23/2014 DePTK 8AIIPLE w-OTHER TEBTSI It. uses SOIL DE8CRIPT10N No. "" COMMENTS Piece of CODCICle debris at surface I' x 2' x 6' Probe 1-6' -SM Dark brown/gray gravelly silty SAND, dry to moist, dense Probe 1-3' ----------------------------------------------------------· Probe 1-3' . SM Tao fme silty SAND with some gravel and SAND, dry to moist, Probe 1-3' variable dense lo loose Probe I J.J 8' . 5 Probe4-6' - -Total depth of test pit = 6' bgs No groundwater seepage ob,ecved -Variable loose lo dense soils encountered at depths between 3 and 6 -feet bgs. 10 _ -- - - 15 - TEST PIT LOGS • Grm:_~ .. ~!~~~c. PROPOSED SHORT PLAT 3413NE7THST RENTON,WASHINGTON a...•u.•••1181 Sclantlsta JOB NO. G-3710 I DATE 7/23/14 I PLATE A2 , .. j TEST PIT NO. TP-3 LOGGED BY AG TEST PIT DATE: 07123/2014 DEPTH SAMPLE w-OTHER TESTS' It. uses SOIL DESCRIPTION No. % COMMENTS SM Brown fine silty SAND with some gravel, dty, dense Probe <l" - Drain tile and drain rock obsttved above a depth of 3'-4" -apparently Probe 2-3" - excavated into an in-active dra.infield ----------------------------------------------------------Probe 2-4" -SM Tan fine silty SAND with some g,avel, dty to moist, medium dense and 5 Probe 2-4" -dense Probe 3-5" -Total depth of test pit = 6' below ground surface (bgs) No groundwater seepoge eocountered -Competent native soils eocountered at 3.5' bgs - 10 -- - - - 16 - TEST PIT NO. TP-4 LOOGEDBY AG TEST PIT DATE: 07123/2014 Dl!PTH UMP\.£ w ... OTHER 11:STSI It. uses SOIL DESCRIPTION No, % COMMENTS Probe <I" -SM Brown/g,ay fine silty SAND with some gravel, d,y, dense Probe I" -Probe 2-3" -., ___ -----------------------------------------------------. Probe <2" SM Gray gravelly silty SAND, dty to moist, dense to very dense Probed" -' (un-weathered glacial tiU) 5 - -Total depth of lest pit= 4' bgs No groundwater seepoge observed -Competent native soils eocountered at ground mlface . - 10 _ -. --16 - TEST PIT LOGS • G""!!L~~~~~c. PROPOSED SHORT PLAT 3413 NE 7TH ST RENTON,WASHINGTON Effi ........ Sc .... JOB NO. G-3710 I DATE 7123/14 I PLATE A3