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HomeMy WebLinkAboutC21006052_TIR_Drainage Report_Approved1 TECHNICAL INFORMATION REPORT FOR Tran-Nguyen Development 2309 Aberdeen Avenue NE Renton, Washington December, 2022 12-26-2022 DEVELOPMENT ENGINEERING yqi 04/21/2023 SURFACE WATER UTILITY JFarah 04/21/2023 2 TABLE OF CONTENTS 1.0 Project Overview………………………………………………………..…….…...4 1.1 General……………………………………………………………………………4 1.2 Pre-Developed Condition……………………………………………………...…4 1.3 Proposed Development…………………………………………………………...4 1.4 Proposed Storm Drainage Facilities………………………………………………5 1.5 Soils………………………………………………………………………………5 2.0 Conditions and Requirements Summary…………………………………..…….7 2.1 Conditions and Requirements…………………………………………………….7 2.1.1 Core Requirements……………………………………………………………7 2.1.2 Special Requirements…………………………………………………………8 3.0 Offsite Analysis…………………………………………………………………....10 3.1 Standard Requirements…………………………………………………..…..….10 3.2 Scope of Analysis…………………………………………………………….....10 3.2.1 Resource Review……………………………………………………………10 3.2.2 Field Inspection…………………………………………………………..…10 3.2.3 Drainage System Description and Problem Descriptions………………..…10 3.2.4 Mitigation of Existing or Potential Problems………………………………10 4.0 Flow Control and Water Quality Facility Analysis and Design………..………11 4.1 Existing Site Hydrology…………………………………………………………11 4.2 Proposed Site Hydrology………………………………………………………..11 4.3 Performance Standards………………………………………………………….11 4.4 Flow Control Facilities………………………………………………………….12 4.5 Water Quality Facilities…………………………………………………………12 5.0 Conveyance System Analysis and Design……………………………….……….13 5.1 Standards Requirements…………………………………………………………13 5.2 Proposed Conveyance System…………………………………………….….…13 6.0 Special Reports and Studies……………………………………………………...14 6.1 Geotechnical…………………………………………………………………….14 7.0 Other Permits……………………..……………………………………………….15 7.1 NPDES Permit…………………………………………………………………..15 8.0 CSWPPP Analysis and Design…………………………………………….……..16 8.1 ESC Plan………………………………………………………………………...16 9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant……………………………………………………….…17 9.1 Bond Quantities Plan………………………………………………………........17 9.2 Declaration of Covenant for Privately Maintained Flow Control BMPs……….17 10.0 Operations and Maintenance Manual…………………………………...……...18 10.1 Maintenance Recommendations……………………………………………….18 3 LIST OF FIGURES Figure 1 – Vicinity Map Figure 2 – Existing Conditions (Existing Drainage) Figure 3 – Developed Conditions (Proposed Drainage) Figure 4 – Flow Chart for Determining the Type of Drainage Review Required Figure 5 – Flow Control Application Map Figure 6 – Groundwater Protection Areas Figure 7 – Downstream Analysis Map Figure 8 – Bond Quantities Worksheet Figure 9 – Maintenance and Operations Manual Figure 10 – TIR Worksheet LIST OF TABLES Table 1 – Pre-Developed Conditions Surface Areas Table 2 – Developed Conditions Surface Areas LIST OF APPENDICES APPENDIX A – Geotechnical Report APPENDIX B – Drainage, Cross-sections and Detail Plans APPENDIX C – BMPs Design Criteria and Maintenance Standards APPENDIX D – Declaration of Covenant for Maintenance and Inspection of On-Site BMPs Appendix E – Continuous Model Calculations Output Appendix F – Stormwater Pollution Prevention Plan Appendix G – Drainage Basin Surface Areas Geotechnical Report 4 1.0 PROJECT OVERVIEW 1.1 General The Nguyen single-family homes Project proposes to construct three new single- family residences located at 2309 Aberdeen Avenue NE, in Renton, WA (See Figure 1 – Vicinity Map). The development will include the construction of three, two story, single-family residences, pathways, landscaping, On-site BMPs and associated right of way improvements along the Project frontage. 1.2 Pre-developed Condition The general location of the project site is shown on Figure 1 (Vicinity Map). The site consists of a roughly square-shaped covering approximately 0.84 acres. The site is currently vacant but was previously occupied by a single-family residence within the western portion of the site. Topography within the western and central portion of the site is kinda hilly from west of east of the site with moderately landslide. The eastern portion of the property is generally level. The site is generally vegetated by grass-covered yard areas, young to mature trees, and landscaping. A horseshoe-shaped gravel driveway is located within the eastern portion of the property. The property is bound to the north, south, and west by single-family residences, and to the east by Aberdeen Avenue NE. See Figure 2 for existing site conditions. See Table #1 below for Pre-Developed Condition Surface Areas. Table 1 – Pre-Developed Condition Surface Areas Type of Land Covers Area (ac) Ex. PGIS 0.0775 Ex. NPGIS 0.0420 Ex. Pervious 0.7205 Total Lot Area 0.8400 1.3 Proposed Developed Condition 5 The development proposes to construct three new single-family residences located at 2309 Aberdeen Avenue NE, in Renton, WA (See Figure 1 – Vicinity Map). The development will include the construction of three, two story, single- family residences, pathways, landscaping, On-site BMPs and associated right of way improvements along the Project frontage. See Table #2 below for proposed developed conditions surface areas and Figure 3 for developed site conditions. Table 2 – Developed Condition Surface Areas Type of Land Covers Area (ac) Dev. PGIS 0.1045 Dev. NPGIS 0.2755 Dev. Pervious 0.4600 Total Area 0.840 1.4 Proposed Storm Drainage Facilities The roof surface runoff for each of the residence will be tightline and convey to an infiltration trench on each lot. The access roadway and residences driveway will be conveyed to the proposed storm filter for water quality treatment then pipe to an infiltration trench for flow control for the runoff. See Figure 3 for the proposed BMPs location, cross-sections, and details. 1.5 Soils The geologic units for this site are shown on Preliminary Geologic Map of Seattle and Vicinity, Washington, by Waldron, H.H., Mulineaux, D.R., and Crandell, D.r., (USGS, 1961). This site is mapped as younger gravel (Qyg) with younger sand (Qys) and alluvium (Qa) mapped nearby. The younger gravel and sanddeposits are described as fine to coarse sand that contains varying amounts ofgravel. The alluvium is described as silt with varying amounts of sand andorganic material. Our explorations generally encountered fine to coarse sand withvarying amounts of sand and organic material. The explorations generally encountered fine to coarse sand with varying amounts of gravel and silt within thewestern and central portion of the property that we interpreted as youngeroutwash soils. The explorations within the very eastern portion of the propertygenerally encountered silt with sand and silty fine to medium sand that weinterpreted as native alluvium and younger sand deposits at depth. See Geotechnical Report in Appendix A for more detail of soil information. 6 2.0 CONDITIONS AND REQUIREMENTS SUMMARY 2.1 Conditions and Requirements Stormwater management for this project will be provided in accordance with the 2017 City of Renton Surface Water Design Manual requirements. The flow chart in Figure 5 – Flow Chart for Determining the Type of Drainage Review Required, provides the framework to determine which core Requirements apply to the Project. The Project will add/replace more than 5,000 square feet of impervious surface; therefore, directed drainage review is required. The Project must comply with Core Requirements #1 - #9 and Special Requirements #1 - #6 per 2017 Renton SWDM. 2.1.1 Core Requirements Core Requirement #1: Discharge at Natural Location •Stormwater plans have been prepared; a copy is in Appendix B. 2017 City of Renton Surface Water Design Manual requirements for flow controland water quality treatment through the use of infiltration trenches. Anyrunoff not detain by the infiltration trenches will be disperse and infiltrateinto ground by yard grass like “natural discharge location”. Core Requirement #2: Offsite Analysis •All projects are required to perform an offsite analysis. A Level 1 analysishas been performed and presented in Section 3.0 of this report. Core Requirement #3: Flow Control •The project falls within the duration flow control standard (ForestedConditions) based on the City of Renton Flow Control Application Map,See Figure 5. A continuous Model will be used to calculate the infiltration trenches sizes to handle the added flow for the project. Flow Control will be mitigated by matching the predeveloped durations for therange of predeveloped discharge rates from 50% of the 2-year peak flowup to the full 50-year peak. Core Requirement #4: Conveyance System •Runoff from the residence roofs will sheet flows to the downspout andpiped to each individual infiltration trench. Runoff from residencedriveways and access roadway flows to the storm filter and then to an infiltration trench. See figure 3 for infiltration trenches and catch basin filter locations. Core Requirement #5: Erosion and Sediment Control •Erosion and Sediment Control (ESC) Plans has been prepared and will be submitted with the Stormwater plans. Additionally, the Contractor will be 7 required to prepare a Stormwater Pollution Prevention and Spill (WSPPS) Plan to comply with County requirements. Applicable Best Management Practices (BMPs) will be selected and maintained by the Project Owner to control pollution. Core Requirement #6: Maintenance and Operations •A maintenance and operations manual had been prepared and is provided in Section 10.0 of this report. Core Requirement #7: Financial Guarantees and Liability •All required bonds will be paid by the Owner prior to permit approval, per City of Renton/ King County Manual. See Section 9.0 of this report forBond Quantities. Core Requirement #8: Water Quality •Runoff Treatment is not required for this project pollution generatingimpervious surfaces (PGIS). PGIS is less than 5,000 SF threshold. Butthis project will proposed to provide a stormfilter catch basin to providewater quality treatment for access roadway and driveways. Core Requirement #9: On-Site BMPs •This project required to implements On-Site BMPs per 2017 City ofRenton SWDM requirements for lot larger then 22,000 sf. According tothe Geotechnical Report, infiltration is feasible for this parcel. Each of the proposed roof runoff will be convey to each individual infiltration trench to mitigate for the roof impervious surface. Residence driveways androadway access will be mitigated by implemented catch basin filter then toan infiltration trench. This project proposed to use full infiltration tomitigate for the new added, replaced impervious surfaces. A continuous model was used to analyze the infiltration trenches to mitigate for each roofs, and the residence driveways/ access roadway. Flow Control will bemitigated by matching the predeveloped durations for the range ofpredeveloped discharge rates from 50% of the 2-year peak flow up to thefull 50-year peak. See Appendix E for model results and met all LID performance standards. 2.1.2 Special Requirements Special Requirement #1: Other Adopted Requirements •No other area-specific requirements apply to this Project. Special Requirement #2: Flood Hazard Delineation •Not applicable. The Project is not adjacent to a flood hazard area. Special Requirement #3: Flood Protection Facilities 8 •Not applicable. There are no flood protection facilities on or adjacent to the site. Special Requirement #4: Source Control •Not applicable. The Project does not require a commercial building orcommercial site development permit. Special Requirement #5: Oil Control •Not Applicable. This site is not classified as high-use roadway. Special Requirement #6 •Aquifer Protection Area.This project falls within Zone 2 of the APA. This project will complywith requirement to protect the aquifer protection area by implement liner wherever it is required to protect the aquifer. This project will useGeomembrance Liners described in Section 6.2.4.1 from the 2017 City ofRenton Surface Water Design Manual in all the infiltration trenches toprotect the Zone 2 of the APA. 9 3.0 OFF-SITE ANALYSIS 3.1 Standard Requirements Offsite analysis is required for all projects per 2017 City of Renton SWDM. This Project is not exempt from this requirement, since the project will add more than 2,000 square feet of impervious area. 3.2 Scope of Analysis As shown in Figure 7, the offsite analysis study area extends approximately ¼ mile downstream from the Project site. 3.2.1 Resource Review • City of Renton COR Map. 3.2.2 Field Inspections The study area was observed on March 9, 2021. Atmospheric conditions were chill and semi sunny. No evidence of downstream conveyance issues was identified. All of downstream conveyance is storm sewer pipe system underground. From the proposed development to May Creek is all underground drainage pipe system. From May Creek to Lake Washington open Creek channel flow to Lake Washington. 3.2.3 Drainage System Description and Problem Descriptions Figure 7 shows a map of the downstream system. No downstream drainage issues were identified by the Level 1 downstream analysis. 3.2.4 Mitigation of Existing or Potential Problems Since no downstream issues were identified no further downstream analysis will be required. No mitigation measures, in addition to the On-site BMP’s are proposed. 10 4.0 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN 4.1 Existing Site Hydrology The general location of the project site is shown on Figure 1 – Vicinity Map. The site consists of a roughly square-shaped covering approximately 0.84 acres. The site is currently vacant but was previously occupied by a single-family residence withing the western portion of the site. Topography within the western and central portion of the slopes gently down from the western property line to the eastern portion of the property. The eastern portion of the property is generally level. The site is generally vegetated by grass-covered yard areas, young to mature trees, and landscaping. A horseshoe-shaped gravel driveway is located within the eastern portion of the property. The site does not have any stormwater management. Stormwater runoff either infiltrate into the ground and/or sheet flows toward Aberdeen Avenue NE. See Figure 2 for an existing site conditions and photos. 4.2 Proposed Site Hydrology All of the residence roofs surface runoff sheet flow to downspouts. The downspout will be tightlined to each individual infiltration trench for each lot. Other impervious surfaces onsite, including residence driveways and access roadway has been graded to flows to a catch basin filter then the an infiltration trench. See Figure 3 for developed condition flow patterns. 4.3 Performance Standards The project falls within the duration flow control standard (Forested Conditions) based on COR Flow Control Application Map, See Figure 5. This project will use the continuous model MGSFlood application to size the infiltration trenches to meet the minimum required performance for flow control duration standard matching forested site conditions is; Developed discharge durations shall not exceed per developed durations for the range of pre-developed discharge rates form 50% of the 2-year peak flow up to the full 50-year peak flow. 4.4 Flow Control Facilities This project proposed four infiltration trenches, one in each lot to mitigate for the new roof surfaces. Each roof surface area equal to 4,000 sf. The fourth infiltration trench is proposed for the drivewways and the access roadway. Using the continuous Model MGSFlood Program to size the infiltration trench to meet pre-developed discharge rates form 50% of the 2-year peak flow up to the full 50- year peak flow. From the output, the required infiltration trench to mitigate for 11 the 4,000 sf of roof surface area is 20 ft x 10 ft x 2 ft. Residence driveways and roadway access impervious surfaces total is approximately 4,600 sf of impervious surface area. This project proposed a 110 ft x 2 ft x 2 ft to mitigate for added impervious area for the residence driveway and access roadway. See Appendix E for Program Output and See Appendix C for On-site BMPs for design criteria and Appendix B for BMPs location, cross sections and details. 4.5 Water Quality Facilities This project contains PGIS within the residence driveways and access roadway to the houses. The Project new plus replace PGIS is less 5,000 SF. Therefore, basic treatment for this project is not required. But this project is proposing a catch basin storm filter for the new plus replaced PGIS for treatment before piped to the infiltration trench for flow control. See Appendix C for details. 12 5.0 CONVEYANCE SYSTEMS ANALYSIS AND DESIGN 5.1 Standard Requirements New pipe systems shall be designed with sufficient capacity to convey and contain (at minimum) the 25 years peak flow.” All proposed conveyance systems will meet or exceed this requirement. Rational Method: Q = CIA/Kc I = m/(Tc)^n 25 year storm m=6.89 n=0.539 I = 6.89/(5 min.)^0.539 I = 2.98 in/hour Q = CIA/Kc C = 0.99, I = 2.98, A = 0.092, Kc = 1 Q = 0.99(2.98)(0.092)/1 Q = 0.271 cfs D = 1.33(nQ/ s )^3/8 ; Where n = 0.013, s = 2%, Q = 0.271 cfs D = 1.33 (0.013*0.271)/ .02 ^3/8 D = 0.333 ft D = 3.99 inches diameter pipe to convey the 25 yrs storm. This project proposed 6 inches diameter pipe for all conveyance pipes. 13 5.2 Proposed Conveyance System Roof surface runoff from the three residences will be collected in downspout tightlines and piped to infiltration trench for each lot. In general, runoff from non-building areas will either infiltrate into the ground through lawn area. Residence driveways and access roadway sheet flows to side of the roadway and gutter flow to catch basin filter then to infiltration trench. The project will utilize a 6-inch dia. PVC at 2.0% slope to tightline the residence roofs runoff to an infiltration trench. See Appendix B for drainage plans. 14 6.0 SPECIAL REPORTS AND STUDIES 6.1 Geotechnical A copy of the report titled, “Geotechnical Investigation,” dated February 26, 2021 by Nelson Geotechnical Associates, Inc. is provided in Appendix A. 15 7.0 OTHER PERMITS 7.1 NPDES Permit A Construction Stormwater General Permit is not required since the Project will be disturbing less than one acre with construction activities such as clearing, grading, or excavation. 16 8.0 CSWPPP ANALYSIS AND DESIGN 8.1 ESC Plan A preliminary ESC plan has been provided in Appendix B. A final ESC plan will be prepared by the Contractor according to The Contractor’s means and methods and construction sequencing. The ESC plan will be prepared in accordance with the City’s requirements. Erosion control measures indicated on the preliminary plan includes: marking clearing limits and the use of straw wattles. Sediment control measures indicated on the preliminary plan include a stabilized construction entrance and catch basin/inlet insert protection. SWPPS Plan A SWPPS plan will be prepared by the Contractor according to the Contractor’s means and methods. The SWPPS plan will be prepared in accordance with City’s requirements. 17 9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT 9.1 Bond Quantities Plan A Bond Quantities Worksheet is provided in Figure 10. 9.2 Declaration of Covenant for Privately Maintained Flow Control BMPs A copy of the unsigned Declaration of Covenant is provided in Appendix D. A furnished copy of the Declaration of Covenant will be provided by the Owner at a later time for the infiltration trenches and catch basin storm filter. 18 10.0 MAINTENANCE AND OPERATIONS MANUAL 10.1 Maintenance Recommendations Operation and maintenance requirements for the proposed drainage elements and On-site BMPs have been provided for reference in Figure 9. 19 Figure 1 Site Location 18 Figure 2 Existing Conditions (Existing Drainage) 19 Figure 3 Developed Conditions (Proposed Drainage) S-421002 DATE: FIELDBOOK: DRAWING NO: PAGE: SHEET: OF: SCALE: DESIGNED: DRAWN: CHECKED: APPROVED:NO.REVISION BY DATE APPR FILENAME:SURVEYED: VERTICAL: NAVD 1988 IF NOT ONE INCH ONE INCH AT FULL SCALE HORIZONTAL: NAD 1983/1991 SCALE ACCORDINGLY DATUM Planning/Building/Public Works Dept. CITY OF RENTON IN COMPLIANCE WITH CITY OF RENTON STANDARDSELE.=268.13BOTTOM OF DITCHNTS SCALE IN FEET 02010 20 40 LEGEND PROPOSED STROM DRAIN LINE EXISTING PROPERTY BOUNDARY LINE EXISTING CONTOUR LINE EXISTING EDGE PAVEMENT C-8.0 288 1 2 3 4 5 14 4 4 4 2 3 REMOVED EXISTING CB REMOVED EXISTING CB IE (E)=263.10 IE (S)=265.08 IE (N)=263.30 RIM=270.15 CB TYPE 2 74'ELE.=268.5BOTTOM OF DITCH6 BOTTOM INFILTRATION TRENCH ELEVATION 6 5 5 5 EXST. IE( N)= 262.79' EXST. IE (S)= 263.12' IE (W) = 263.10 EXST. IE (SE) = 265.24' RIM = 271.34' EXISTING SDMH IE (S)=264.50 IE (N)=264.60 RIM=269.70 CB TYPE 2 BUILDING PERMIT FUTURE BOT ELE.=273. TOP ELE.=275 FOR FOOTING DRAIN 2'X4' INFILTRATION TRENCH (FUTURE) R-421007 SEE COR.STD. 226.00 CLEAN OUT 6/16/2022 BUILDING PERMIT FUTURE RIM=270.31 THE TOP OF SIDEWALK ADJUST EXISTING MH TO FLUSH WITH DRAINAGE & SEWER PLAN TRAN-NGUYEN DEVELOPMENT NOTES SIDEWALKPLANTERBUILDING PERMIT FUTURE 6" STORM WATER PIPE MIN. 2.0% (ASTM D-3034 PVC) ROOF DRAIN MIN 2% GRADE (ASTM D-3034 PVC) AND FILL WITH SAND PLUG THE EXISTING DRAINAGE PIPE 12" STORM DRAIN, L=54.0', S=3.0% (ASTM D-3034 PVC) 12" STORM DRAIN, L=60.0', S=2.0% (ASTM D-3034 PVC) 12" STORM DRAIN, L=81.0', S=2.0% (ASTM D-3034 PVC) LINER WILL BE REQUIRED TO PROTECT AQUIFER DURING EACH BUILDING CONSTRUCTION INDIVIDUAL 10' X20' INFILTRATION TRENCH WILL BUILD IE (N)=266.70 RIM=270.88 EXISTING CB SEE COR.STD. 406.1 IE=268.20 RIM=272.20 SSCO # 3 SEE COR.STD. 406.1 IE=270.90 RIM=275.50 SSCO # 2 12/26/2022 SEE COR.STD. 406.1 IE=272.80 RIM=275.50 SSCO # 1 10' UTILITY EASEMENT CONTRACTOR SHALL FIELD VERIFY IE CONNECT WITH EXISTING 8 " SEWER LINE CONTRACTOR SHALL FIELD VERIFY IE CONNECT WITH EXISTING 8 " SEWER LINE SEE C-22.0 FOR DETAILS IE=269.50 RIM=271.8 CONTECH STORM FILTER SEE C-23.0 FOR DETAILS BOT ELE.=268.50 TOP ELE.=271.0 3' X 74' INFILTRATION TRENCH 0.5% IE ( S) = 266.24 IE ( N) = 269.80' IE (W) = 269.82' RIM = 273.45' CB TYPE 2 EXISTING CB REPLACE WITHWWP-27-4210TED-40-4210272 274276 147.8190'80' 20' 50' DF30DF22DF32 DF36 DF30 DS18DF30DF24DF26DF34DF28DF32 278 274290288 280 29082.6'147.81N0°30'04"ES89°10'27"W252.60'N0°29'37"E252.62'N89°08'52"E 282 284 286 272 278 276 274 0+00 1+00 1+701+70 ABERDEEN AVE NE 10'147.815'5' BSBL 20' BSBL20' BSBL20' BSBL 29' BSBL42' BSBL32' BSBL23' BSBL BSBL BSBL 24' BSBL 0+001+001+791+79 272 272 288 284 282 EXISTING GRAVEL DRIVEWAY 274 276 286 284 282 278 276 274 272 280 20 Figure 4 Flow Chart for Determining the Type of Drainage Review Required SECTION 1.1 DRAINAGE REVIEW 12/12/2016 2017 City of Renton Surface Water Design Manual 1-14 FIGURE 1.1.2.A FLOW CHART FOR DETERMINING TYPE OF DRAINAGE REVIEW REQUIRED 21 Figure 5 Flow Control /Water Quality Application Map LakeDesire ShadyLake (MudLake) PantherLake LakeYoungs LakeWashington B l a ck Ri ver Gr een Riv e r C edarRi verUV900 UV167 UV515 UV169 UV900 UV169 UV167BN IncBN IncBBNNIInnccSSEERReennttoonnIIssssaaqquuaahh RR dd RReennttoonnMMaapplleeVVaalllleeyyRRdd MMaapplleeVVaalllleeyyHHwwyy 110088tthhAAvveeSSEESSWWSSuunnsseettBBllvvdd RRaaii nnii eerr AAvveeNNNE 3rd StNE 3rd St SW 43rd StSW 43rd St SSEE CCaarrrrRR dd NE 4th StNE 4th St SSEERReennttoonn MMaappllee VVaalllleeyy RRddLLooggaannAAvveeNN SR 515SR 515PPaarrkkAAvveeNNOOaakkeessddaalleeAAvveeSSWWSSuunnsseettBBllvvddNNEE DDuuvvaallllAAvveeNNEEI-405 FWYI-405 FWY II--440055FFWWYYSR 167SR 167114400tthh WWaayySS EE NNEE2277tthhSStt 115566tthhAAvveeSSEEUUnniioonnAAvveeNNEE111166tthhAAvveeSSEESW 7th StSW 7th St N 8th StN 8th St PP uuggeettDDrrSSEE RR eennttoonnAAvvee SS SSWW 2277tthh SStt BBeennssoonnRRddSSWWiilllliiaammssAAvveeSSMMoonnrrooeeAAvveeNNEESE 128th StSE 128th St II nntt eerr uurr bbaannAAvveeSS HHooqquuiiaammAAvveeNNEE8844tthhAAvveeSSSSEEPPeett rr oovviitt sskkyyRRddEEVVaalllleeyyHHwwyySE 192nd StSE 192nd St SE 60th StSE 60th St TTaallbboottRRddSSRR ee nntt oo nn AAvveeSS116644tthhAAvveeSSEESE 208th StSE 208th St SE 72nd StSE 72nd St RRaaiinniieerrAAvvee SS 111166tthhAAvveeSSEES 128th StS 128th St NNeewwccaassttllee WWaayy SS 221122tthh SStt SS118800tthh SStt CCooaall CCrreeeekkPPkkwwyySSEESW 41st StSW 41st St 114400tthhAAvveeSSEE112288tthhAAvveeSSEE6688tthhAAvveeSSSSEE 116688tthh SStt NE 12th StNE 12th St BBee aa ccoonn AA vv ee SS FFoorreessttDDrr SSEE SSEE 116644tthh SStt 114488tthhAAvveeSSEESSEEMMaayy VVaalllleeyyRRdd SS EE JJoonneess RRdd SSEE 22 00 44 tthh WW aayySW 34th StSW 34th St SE 144th StSE 144th St 114488tthhAAvveeSSEE115544tthhPPllSSEELL aa kk ee WWaa sshhii nnggtt oonnBBll vvddNNEEddmmoonnddssAAvveeNNEEAAbbeerrddeeeennAAvveeNNEEEEMM eerrcceerrWWaayyWWeessttVVaalllleeyyHHwwyyEast Valley RdEast Valley Rd,§-405 ,§-405 ,§-405 µ0 1 2Miles Flow Control Application Map Reference 15-A Date: 01/09/2014 Flow Control Standards Peak Rate Flow Control Standard (Existing Site Conditions) Flow Control Duration Standard (Existing Site Conditions) Flow Control Duration Standard (Forested Conditions) Flood Problem Flow Unincorporated King County Flow Control Standards Renton City Limits Potential Annexation Area project site highlight and point the project location 22 Figure 6 Groundwater Protection Area/ Environmental Sensitive Areas 23 Figure 7 Downstream Analysis Map MAV CREEK. .,.. .. �� 6 � =�· ► ., j(; King County Eas1s1de Q Rail Comdor 9 Lakeview Crest by Tn Pointe Homes s ·,t ef r i ,l N-Sl zI ► : � NrJIIIIII z1 HJ1tll I . .,,. .. I Nll6l!ISI Kennydale .. _.� Beach Park N:IScl!St i l.. _ .. i !z z z : H:D•PI ..Boulevard Salon 9 IN SJNISt :I .. ✓ N:ll!ldSl KENNVDALE :N atSl Cloudbreak cal� 9Col�man Point N-$1 N 30th St ene Coulon Park Q .. ·-·I ► : z<.-f! N21thl'I •1s, N -11•-c, N27th l't �� ♦ � � ·" /' ici, �r � ! "'1-� z � N -SI Bella Vista9 • • " OK01•anc'1ulch \ !; • � I \ \ ' �,. � • i!f ·-· .. .,.,. .. ..... ..... ,, __ R&:11111 =\. \ 'I • i •[ \ • .. • -·Qors i ►:Ill Suzie's Swim School 9 1 S(f7th■ ·�... _ ,V•k D< HU5tl>., (J � i� B est Loving Car e 9Elderly Living Mllrd"1 .. ,« :13Jd Pl ........ Mayer-. �'fl' Jellybean Early 9leam,ng Center .. lit II Kennydale Memonal Hall Q .. ..... t j Kennydale \ Lions Park �2309 Aberdeen Ave N1'2&mSI G gle·. Renton, WA 98056 i ?' ; ... J g ll't . % ,., St M oy CrHk Pa,k 0, Iii =--• e.. � • ·-·.-I':, Mariana s AFH, Inc C ., .. Wmdtree Park Q ........ -4,._..� f HoneyOew Creek Tra il head N.EU#ISI ... _ .. NE .. May .re< Pork � 0 l \ 0-� .. , .. _., __ . .,,.,..,, ,..,_.J ... �-- 24 Figure 8 Bond Quantities worksheet 1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430‐7200Date Prepared: Name:PE Registration No:Firm Name:Firm Address:Phone No.Email Address:Project Name: Project Owner:CED Plan # (LUA):Phone:CED Permit # (C):Address: Site Address:Street Intersection:Addt'l Project Owner:Parcel #(s):Phone:Address: Clearing and grading greater than or equal to 5,000 board feet of timber? Yes/No:NOWater Service Provided by:If Yes, Provide Forest Practice Permit #:Sewer Service Provided by: AddressAbbreviated Legal Description:THE SOUTH ONE‐HALF OF THE NORTH ONE‐HALF OF TRACT 253, C.D. HILLMAM'S LAKE WASHINGTON GARDEN OF EDEN DIVISION NO.4, ACCORDING TO THE PLAN THEREOF RECORDED IN VOLUME 11 OF PLATS, PAGE 82, RECORDS OF KING COUNTY, City, State, Zip2309 Aberdeen Ave NE, Renton, WA 980562309 Aberdeen ave NEAdditional Project OwnerNE 24th St########21‐000206206‐384‐369012/28/2022Prepared by:FOR APPROVALProject Phase 1wu868good@outlook.comSTEVE WU38852Tendem engineering consultants inc8822 NE 178th St Bothell, WA 98011206‐795‐5674SITE IMPROVEMENT BOND QUANTITY WORKSHEETPROJECT INFORMATIONCITY OF RENTONCITY OF RENTONPhoneEngineer Stamp Required (all cost estimates must have original wet stamp and signature)Clearing and GradingUtility ProvidersN/AProject Location and DescriptionProject Owner InformationTran‐Nguyen DevelopmentRenton, WA 980563343901963Long & Thu Thuy Ngyuyen & Vu TranPage 1 of 2Ref 8‐H Bond Quantity WorksheetSECTION I PROJECT INFORMATIONUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/202212/28/2022 10.1%Total Estimated Construction CostsEA + B + C + D$ 236,287.86Estimated Civil Construction Permit ‐ Construction Costs2Stormwater (Drainage)C$ 27,872.13As outlined in City Ordinance No. 4345, 50% of the plan review and inspection fees are to be paid at Permit Submittal. The balance is due at Permit Issuance. Significant changes or additional review cycles (beyond 3 cycles) during the review process may result in adjustments to the final review fees.Roadway (Erosion Control + Transportation)D127,244.50$ WaterA54,361.88$ Wastewater (Sanitary Sewer)B26,809.35$ 2 All prices include labor, equipment, materials, overhead, profit, and taxes. City of Renton Sales Tax is:1 Select the current project status/phase from the following options:              For Approval ‐ Preliminary Data Enclosed, pending approval from the City;              For Construction ‐ Estimated Data Enclosed, Plans have been approved for contruction by the City;              Project Closeout ‐ Final Costs and Quantities Enclosed for Project Close‐out SubmittalPage 2 of 2Ref 8‐H Bond Quantity WorksheetSECTION I PROJECT INFORMATIONUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/2022 CED Permit #:########UnitReference #PriceUnitQuantity CostBackfill & compaction‐embankmentESC‐17.50$ CY7105,325.00Check dams, 4" minus rockESC‐2SWDM 5.4.6.390.00$ Each2180.00Catch Basin ProtectionESC‐3145.00$ Each4580.00Crushed surfacing 1 1/4" minusESC‐4WSDOT 9‐03.9(3)110.00$ CYDitchingESC‐510.50$ CY75787.50Excavation‐bulkESC‐62.30$ CY300690.00Fence, siltESC‐7SWDM 5.4.3.15.00$ LF7353,675.00Fence, Temporary (NGPE)ESC‐81.75$ LFGeotextile FabricESC‐93.00$ SYHay Bale Silt TrapESC‐100.60$ Each106.00HydroseedingESC‐11SWDM 5.4.2.40.90$ SY40003,600.00Interceptor Swale / DikeESC‐121.15$ LFJute MeshESC‐13SWDM 5.4.2.24.00$ SYLevel SpreaderESC‐142.00$ LFMulch, by hand, straw, 3" deepESC‐15SWDM 5.4.2.12.90$ SYMulch, by machine, straw, 2" deepESC‐16SWDM 5.4.2.12.30$ SYPiping, temporary, CPP, 6"ESC‐1713.75$ LFPiping, temporary, CPP, 8"ESC‐1816.00$ LFPiping, temporary, CPP, 12"ESC‐1920.50$ LFPlastic covering, 6mm thick, sandbaggedESC‐20SWDM 5.4.2.34.60$ SY10004,600.00Rip Rap, machine placed; slopesESC‐21WSDOT 9‐13.1(2)51.00$ CYRock Construction Entrance, 50'x15'x1'ESC‐22SWDM 5.4.4.12,050.00$ Each12,050.00Rock Construction Entrance, 100'x15'x1'ESC‐23SWDM 5.4.4.13,675.00$ EachSediment pond riser assemblyESC‐24SWDM 5.4.5.22,525.00$ Each12,525.00Sediment trap, 5'  high berm ESC‐25SWDM 5.4.5.122.00$ LFSed. trap, 5' high, riprapped spillway berm section ESC‐26SWDM 5.4.5.180.00$ LFSeeding, by handESC‐27SWDM 5.4.2.41.15$ SY50005,750.00Sodding, 1" deep, level groundESC‐28SWDM 5.4.2.59.20$ SYSodding, 1" deep, sloped groundESC‐29SWDM 5.4.2.511.50$ SYTESC SupervisorESC‐30125.00$ HR506,250.00Water truck, dust controlESC‐31SWDM 5.4.7160.00$ HR203,200.00UnitReference #PriceUnitQuantity CostEROSION/SEDIMENT SUBTOTAL:39,218.50SALES TAX @ 10.1%3,961.07EROSION/SEDIMENT TOTAL:43,179.57(A)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR EROSION & SEDIMENT CONTROLDescriptionNo.(A)WRITE‐IN‐ITEMS Page 1 of 1Ref 8‐H Bond Quantity WorksheetSECTION II.a EROSION_CONTROLUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/2022 CED Permit #:########ExistingFuture PublicPrivateRight‐of‐WayImprovementsImprovements(D) (E)DescriptionNo. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostGENERAL ITEMS Backfill & Compaction‐ embankmentGI‐17.00$              CY 78546.005603,920.00Backfill & Compaction‐ trenchGI‐2 10.25$            CY 20205.0040410.00Clear/Remove Brush, by hand (SY)GI‐31.15$              SY 200230.0020002,300.00Bollards ‐ fixedGI‐4 275.00$          EachBollards ‐ removableGI‐5 520.00$          EachClearing/Grubbing/Tree RemovalGI‐6 11,475.00$    Acre 0.11,147.500.33,442.50Excavation ‐ bulkGI‐72.30$              CYExcavation ‐ TrenchGI‐85.75$              CY 20115.0045258.75Fencing, cedar, 6' highGI‐9 23.00$            LF1703,910.00Fencing, chain link, 4'GI‐10 44.00$            LFFencing, chain link, vinyl coated,  6' highGI‐11 23.00$            LFFencing, chain link, gate, vinyl coated,  20' GI‐12 1,600.00$      EachFill & compact ‐ common barrowGI‐13 28.75$            CY 20575.00401,150.00Fill & compact ‐ gravel baseGI‐14 31.00$            CY 25775.0025775.00Fill & compact ‐ screened topsoilGI‐15 44.75$            CYGabion, 12" deep, stone filled mesh GI‐16 74.50$            SYGabion, 18" deep, stone filled mesh GI‐17 103.25$          SYGabion, 36" deep, stone filled meshGI‐18 172.00$          SYGrading, fine, by handGI‐19 2.90$              SYGrading, fine, with graderGI‐20 2.30$              SY 21004,830.00Monuments, 3' LongGI‐21 1,025.00$      EachSensitive Areas SignGI‐22 8.00$              EachSodding, 1" deep, sloped groundGI‐239.25$              SYSurveying, line & gradeGI‐24 975.00$          Day 1975.001975.00Surveying, lot location/linesGI‐25 2,050.00$      Acre 0.51,025.000.51,025.00Topsoil Type A (imported)GI‐26 32.75$            CY 421,375.5020655.00Traffic control crew ( 2 flaggers )GI‐27 137.75$          HR 608,265.00Trail, 4" chipped woodGI‐28 9.15$              SY 1501,372.502001,830.00Trail, 4" crushed cinderGI‐29 10.25$            SYTrail, 4" top courseGI‐30 13.75$            SYConduit, 2"GI‐31 5.75$              LFWall, retaining, concreteGI‐32 63.00$            SFWall, rockeryGI‐33 17.25$            SFSUBTOTAL THIS PAGE:21,436.5020,651.25(B)(C)(D)(E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B)(C)Page 1 of 3Ref 8‐H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/2022 CED Permit #:########ExistingFuture PublicPrivateRight‐of‐WayImprovementsImprovements(D) (E)DescriptionNo. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B)(C)ROAD IMPROVEMENT/PAVEMENT/SURFACINGAC Grinding, 4' wide machine < 1000syRI‐1 34.50$            SY 2107,245.00AC Grinding, 4' wide machine 1000‐2000sy RI‐2 18.25$            SYAC Grinding, 4' wide machine > 2000syRI‐3 11.50$            SYAC Removal/DisposalRI‐4 40.00$            SY 401,600.00Barricade, Type III ( Permanent )RI‐5 64.25$            LFGuard RailRI‐6 34.50$            LFCurb & Gutter, rolledRI‐7 19.50$            LFCurb & Gutter, verticalRI‐8 14.25$            LF 2002,850.00Curb and Gutter, demolition and disposal RI‐9 20.50$            LFCurb, extruded asphaltRI‐10 6.25$              LFCurb, extruded concreteRI‐11 8.00$              LFSawcut, asphalt, 3" depthRI‐12 3.00$              LFSawcut, concrete, per 1" depthRI‐13 5.00$              LF 150750.00Sealant, asphaltRI‐14 2.25$              LFShoulder, gravel, 4" thickRI‐15 17.25$            SYSidewalk, 4" thickRI‐16 43.50$            SY833,610.50Sidewalk, 4" thick, demolition and disposal RI‐17 37.00$            SYSidewalk, 5" thickRI‐18 47.00$            SYSidewalk, 5" thick, demolition and disposal RI‐19 46.00$            SYSign, Handicap RI‐20 97.00$            EachStriping, per stallRI‐21 8.00$              EachStriping, thermoplastic, ( for crosswalk )RI‐22 3.50$              SFStriping, 4" reflectorized lineRI‐23 0.55$              LFAdditional 2.5" Crushed SurfacingRI‐244.15$              SYHMA 1/2" Overlay 1.5" RI‐25 16.00$            SY 3205,120.00HMA 1/2" Overlay 2"RI‐26 20.75$            SYHMA Road, 2", 4" rock, First 2500 SYRI‐27 32.25$            SYHMA Road, 2", 4" rock, Qty. over 2500SY RI‐28 24.00$            SYHMA Road, 4", 6" rock, First 2500 SYRI‐29 51.75$            SYHMA Road, 4", 6" rock, Qty. over 2500 SY RI‐30 42.50$            SYHMA Road, 4", 4.5" ATBRI‐31 43.50$            SY2209,570.00Gravel Road, 4" rock, First 2500 SYRI‐32 17.25$            SYGravel Road, 4" rock, Qty. over 2500 SYRI‐33 11.50$            SYThickened EdgeRI‐34 10.00$            LFSUBTOTAL THIS PAGE:21,175.509,570.00(B)(C)(D)(E)Page 2 of 3Ref 8‐H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/2022 CED Permit #:########ExistingFuture PublicPrivateRight‐of‐WayImprovementsImprovements(D) (E)DescriptionNo. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B)(C)PARKING LOT SURFACING No.2" AC, 2" top course rock & 4" borrowPL‐1 24.00$            SY2" AC,  1.5"  top course & 2.5" base course PL‐2 32.00$            SY4" select borrowPL‐35.75$              SY1.5" top course rock & 2.5" base coursePL‐4 16.00$            SY2203,520.00SUBTOTAL PARKING LOT SURFACING:3,520.00(B)(C)(D)(E)LANDSCAPING & VEGETATION No.Street TreesLA‐1Median LandscapingLA‐2Right‐of‐Way LandscapingLA‐3Wetland LandscapingLA‐4SUBTOTAL LANDSCAPING & VEGETATION:(B)(C)(D)(E)TRAFFIC & LIGHTING No.SignsTR‐1Street Light System ( # of Poles)TR‐2Traffic SignalTR‐3Traffic Signal ModificationTR‐4SUBTOTAL TRAFFIC & LIGHTING:(B)(C)(D)(E)WRITE‐IN‐ITEMSSUBTOTAL WRITE‐IN ITEMS:STREET AND SITE IMPROVEMENTS SUBTOTAL:42,612.0033,741.25SALES TAX @ 10.1%4,303.813,407.87STREET AND SITE IMPROVEMENTS TOTAL:46,915.8137,149.12(B)(C)(D)(E)Page 3 of 3Ref 8‐H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/2022 CED Permit #:########ExistingFuture PublicPrivateRight‐of‐WayImprovementsImprovements(D) (E)DescriptionNo. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostDRAINAGE (CPE = Corrugated Polyethylene Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe.)Access Road, R/DD‐130.00$             SY* (CBs include frame and lid)BeehiveD‐2 103.00$           EachThrough‐curb Inlet FrameworkD‐3 460.00$           EachCB Type ID‐4 1,725.00$       Each11,725.00CB Type ILD‐5 2,000.00$       Each12,000.00CB Type II, 48" diameterD‐6 3,500.00$       Each     for additional depth over 4'    D‐7 550.00$           FTCB Type II, 54" diameterD‐8 4,075.00$       Each     for additional depth over 4'D‐9 570.00$           FTCB Type II, 60" diameterD‐10 4,225.00$       Each     for additional depth over 4'D‐11 690.00$           FTCB Type II, 72" diameterD‐12 6,900.00$       Each     for additional depth over 4'D‐13 975.00$           FTCB Type II, 96" diameterD‐14 16,000.00$     Each     for additional depth over 4'D‐15 1,050.00$       FTTrash Rack, 12"D‐16 400.00$           Each 2800.001400.00Trash Rack, 15"D‐17 470.00$           EachTrash Rack, 18"D‐18 550.00$           EachTrash Rack, 21"D‐19 630.00$           EachCleanout, PVC, 4"D‐20 170.00$           EachCleanout, PVC, 6"D‐21 195.00$           EachCleanout, PVC, 8"D‐22 230.00$           EachCulvert, PVC, 4" D‐23 11.50$             LFCulvert, PVC, 6" D‐24 15.00$             LF1001,500.00Culvert, PVC,  8" D‐25 17.00$             LFCulvert, PVC, 12" D‐26 26.00$             LF 1503,900.00Culvert, PVC, 15" D‐27 40.00$             LFCulvert, PVC, 18" D‐28 47.00$             LFCulvert, PVC, 24"D‐29 65.00$             LFCulvert, PVC, 30" D‐30 90.00$             LFCulvert, PVC, 36" D‐31 150.00$           LFCulvert, CMP, 8"D‐32 22.00$             LFCulvert, CMP, 12"D‐33 33.00$             LFSUBTOTAL THIS PAGE:10,700.005,625.00(B)(C)(D)(E)Quantity Remaining (Bond Reduction) (B)(C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESPage 1 of 5Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/202236,000.0 CED Permit #:########ExistingFuture PublicPrivateRight‐of‐WayImprovementsImprovements(D) (E)DescriptionNo. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostQuantity Remaining (Bond Reduction) (B)(C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESDRAINAGE (Continued)Culvert, CMP, 15"D‐34 40.00$             LFCulvert, CMP, 18"D‐35 47.00$             LFCulvert, CMP, 24"D‐36 64.00$             LFCulvert, CMP, 30"D‐37 90.00$             LFCulvert, CMP, 36"D‐38 150.00$           LFCulvert, CMP, 48"D‐39 218.00$           LFCulvert, CMP, 60"D‐40 310.00$           LFCulvert, CMP, 72"D‐41 400.00$           LFCulvert, Concrete, 8"D‐42 48.00$             LFCulvert, Concrete, 12"D‐43 55.00$             LFCulvert, Concrete, 15"D‐44 89.00$             LFCulvert, Concrete, 18"D‐45 100.00$           LFCulvert, Concrete, 24"D‐46 120.00$           LFCulvert, Concrete, 30"D‐47 145.00$           LFCulvert, Concrete, 36"D‐48 175.00$           LFCulvert, Concrete, 42"D‐49 200.00$           LFCulvert, Concrete, 48"D‐50 235.00$           LFCulvert, CPE Triple Wall, 6" D‐51 16.00$             LFCulvert, CPE Triple Wall, 8" D‐52 18.00$             LFCulvert, CPE Triple Wall, 12" D‐53 27.00$             LFCulvert, CPE Triple Wall, 15" D‐54 40.00$             LFCulvert, CPE Triple Wall, 18" D‐55 47.00$             LFCulvert, CPE Triple Wall, 24" D‐56 64.00$             LFCulvert, CPE Triple Wall, 30" D‐57 90.00$             LFCulvert, CPE Triple Wall, 36" D‐58 149.00$           LFCulvert, LCPE, 6"D‐5969.00$             LFCulvert, LCPE, 8"D‐60 83.00$             LFCulvert, LCPE, 12"D‐61 96.00$             LFCulvert, LCPE, 15"D‐62 110.00$           LFCulvert, LCPE, 18"D‐63 124.00$           LFCulvert, LCPE, 24"D‐64 138.00$           LFCulvert, LCPE, 30"D‐65 151.00$           LFCulvert, LCPE, 36"D‐66 165.00$           LFCulvert, LCPE, 48"D‐67 179.00$           LFCulvert, LCPE, 54"D‐68 193.00$           LFSUBTOTAL THIS PAGE:(B)(C)(D)(E)Page 2 of 5Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/2022 CED Permit #:########ExistingFuture PublicPrivateRight‐of‐WayImprovementsImprovements(D) (E)DescriptionNo. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostQuantity Remaining (Bond Reduction) (B)(C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESDRAINAGE (Continued)Culvert, LCPE, 60"D‐69 206.00$           LFCulvert, LCPE, 72"D‐70 220.00$           LFCulvert, HDPE, 6"D‐71 48.00$             LFCulvert, HDPE, 8"D‐72 60.00$             LFCulvert, HDPE, 12"D‐73 85.00$             LFCulvert, HDPE, 15"D‐74 122.00$           LFCulvert, HDPE, 18"D‐75 158.00$           LFCulvert, HDPE, 24"D‐76 254.00$           LFCulvert, HDPE, 30"D‐77 317.00$           LFCulvert, HDPE, 36"D‐78 380.00$           LFCulvert, HDPE, 48"D‐79 443.00$           LFCulvert, HDPE, 54"D‐80 506.00$           LFCulvert, HDPE, 60"D‐81 570.00$           LFCulvert, HDPE, 72"D‐82 632.00$           LFPipe, Polypropylene, 6"D‐83 96.00$             LFPipe, Polypropylene, 8"D‐84 100.00$           LFPipe, Polypropylene, 12"D‐85 100.00$           LFPipe, Polypropylene, 15"D‐86 103.00$           LFPipe, Polypropylene, 18"D‐87 106.00$           LFPipe, Polypropylene, 24"D‐88 119.00$           LFPipe, Polypropylene, 30"D‐89136.00$           LFPipe, Polypropylene, 36"D‐90 185.00$           LFPipe, Polypropylene, 48"D‐91 260.00$           LFPipe, Polypropylene, 54"D‐92 381.00$           LFPipe, Polypropylene, 60"D‐93 504.00$           LFPipe, Polypropylene, 72"D‐94 625.00$           LFCulvert, DI, 6"D‐95 70.00$             LFCulvert, DI, 8"D‐96 101.00$           LFCulvert, DI, 12"D‐97 121.00$           LFCulvert, DI, 15"D‐98 148.00$           LFCulvert, DI, 18"D‐99175.00$           LFCulvert, DI, 24"D‐100 200.00$           LFCulvert, DI, 30"D‐101 227.00$           LFCulvert, DI, 36"D‐102 252.00$           LFCulvert, DI, 48"D‐103 279.00$           LFCulvert, DI, 54"D‐104 305.00$           LFCulvert, DI, 60"D‐105 331.00$           LFCulvert, DI, 72"D‐106 357.00$           LFSUBTOTAL THIS PAGE:(B)(C)(D)(E)Page 3 of 5Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/2022 CED Permit #:########ExistingFuture PublicPrivateRight‐of‐WayImprovementsImprovements(D) (E)DescriptionNo. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostQuantity Remaining (Bond Reduction) (B)(C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESSpecialty Drainage ItemsDitching SD‐1 10.90$             CYFlow Dispersal Trench    (1,436 base+)SD‐3 32.00$             LFFrench Drain  (3' depth)SD‐4 30.00$             LFGeotextile, laid in trench, polypropylene SD‐53.40$               SYMid‐tank Access Riser, 48" dia,  6' deep SD‐6 2,300.00$       EachPond Overflow SpillwaySD‐7 18.25$             SYRestrictor/Oil Separator, 12"SD‐8 1,320.00$       EachRestrictor/Oil Separator, 15"SD‐9 1,550.00$       EachRestrictor/Oil Separator, 18"SD‐10 1,950.00$       EachRiprap, placedSD‐11 48.20$             CYTank End Reducer (36" diameter)SD‐12 1,375.00$       EachInfiltration pond testingSD‐13 143.00$           HRPermeable PavementSD‐14Permeable Concrete SidewalkSD‐15Culvert, Box      __ ft  x  __ ftSD‐16SUBTOTAL SPECIALTY DRAINAGE ITEMS:(B)(C)(D)(E)STORMWATER FACILITIES (Include Flow Control and Water Quality Facility Summary Sheet and Sketch)Detention PondSF‐1Each Detention TankSF‐2Each Detention VaultSF‐3Each Infiltration PondSF‐4Each Infiltration TankSF‐5Each Infiltration VaultSF‐6Each Infiltration TrenchesSF‐7Each Basic Biofiltration SwaleSF‐8Each Wet Biofiltration SwaleSF‐9Each WetpondSF‐10Each WetvaultSF‐11Each Sand FilterSF‐12Each Sand Filter VaultSF‐13Each Linear Sand FilterSF‐14Each Proprietary FacilitySF‐15Each Bioretention FacilitySF‐16Each SUBTOTAL STORMWATER FACILITIES:(B)(C)(D)(E)Page 4 of 5Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/2022 CED Permit #:########ExistingFuture PublicPrivateRight‐of‐WayImprovementsImprovements(D) (E)DescriptionNo. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostQuantity Remaining (Bond Reduction) (B)(C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESWRITE‐IN‐ITEMS (INCLUDE ON‐SITE BMPs)INFILTRATION TRENCHWI‐1 4,000.00$       14,000.00STORM FILTERWI‐2 5,000.00$       15,000.00WI‐3WI‐4WI‐5WI‐6WI‐7WI‐8WI‐9WI‐10WI‐11WI‐12WI‐13WI‐14WI‐15SUBTOTAL WRITE‐IN ITEMS:9,000.00DRAINAGE AND STORMWATER FACILITIES SUBTOTAL:10,700.0014,625.00SALES TAX @ 10.1%1,0701,477.13DRAINAGE AND STORMWATER FACILITIES TOTAL:11,77016,102.13(B)(C)(D)(E)Page 5 of 5Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/2022 CED Permit #:########ExistingFuture PublicPrivateRight‐of‐WayImprovementsImprovements(D) (E)DescriptionNo. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostConnection to Existing WatermainW‐1 3,400.00$      Each 13,400.00Ductile Iron Watermain, CL 52, 4 Inch Diameter W‐2 58.00$            LFDuctile Iron Watermain, CL 52, 6 Inch Diameter W‐3 65.00$            LFDuctile Iron Watermain, CL 52, 8 Inch Diameter W‐4 75.00$            LFDuctile Iron Watermain, CL 52, 10 Inch Diameter W‐5 80.00$            LFDuctile Iron Watermain, CL 52, 12 Inch Diameter W‐6 145.00$          LF 405,800.0016023,200.00Gate Valve, 4 inch DiameterW‐7 1,225.00$      EachGate Valve, 6 inch DiameterW‐8 1,350.00$      Each 11,350.00Gate Valve, 8 Inch DiameterW‐9 1,550.00$      EachGate Valve, 10 Inch DiameterW‐10 2,100.00$      EachGate Valve, 12 Inch DiameterW‐11 2,500.00$      EachFire Hydrant AssemblyW‐12 5,000.00$      Each 210,000.00Permanent Blow‐Off AssemblyW‐13 1,950.00$      Each 11,950.0011,950.00Air‐Vac Assembly,  2‐Inch DiameterW‐14 3,050.00$      EachAir‐Vac Assembly,  1‐Inch DiameterW‐15 1,725.00$      Each11,725.00Compound Meter Assembly 3‐inch Diameter W‐16 9,200.00$      EachCompound Meter Assembly 4‐inch Diameter W‐17 10,500.00$    EachCompound Meter Assembly 6‐inch Diameter W‐18 11,500.00$    EachPressure Reducing Valve Station 8‐inch to 10‐inch W‐19 23,000.00$    EachWATER SUBTOTAL:22,500.00 26,875.00SALES TAX @ 10.1%2,272.502,714.38WATER TOTAL:24,772.5029,589.38(B)(C)(D)(E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR WATERQuantity Remaining (Bond Reduction) (B)(C)Page 1 of 1Ref 8‐H Bond Quantity WorksheetSECTION II.d WATERUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/2022 CED Permit #:########ExistingFuture PublicPrivateRight‐of‐WayImprovementsImprovements(D) (E)DescriptionNo. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostClean OutsSS‐1 1,150.00$      Each33,450.00Grease Interceptor, 500 gallonSS‐2 9,200.00$      EachGrease Interceptor, 1000 gallonSS‐3 11,500.00$    EachGrease Interceptor, 1500 gallonSS‐4 17,200.00$    EachSide Sewer Pipe, PVC. 4 Inch DiameterSS‐5 92.00$            LFSide Sewer Pipe, PVC. 6 Inch DiameterSS‐6 110.00$          LF19020,900.00Sewer Pipe, PVC, 8 inch DiameterSS‐7 120.00$          LFSewer Pipe, PVC, 12 Inch DiameterSS‐8 144.00$          LFSewer Pipe, DI, 8 inch DiameterSS‐9 130.00$          LFSewer Pipe, DI, 12 Inch DiameterSS‐10 150.00$          LFManhole, 48 Inch DiameterSS‐11 6,900.00$      EachManhole, 54 Inch DiameterSS‐13 6,800.00$      EachManhole, 60 Inch DiameterSS‐15 7,600.00$      EachManhole, 72 Inch DiameterSS‐17 10,600.00$    EachManhole, 96 Inch DiameterSS‐19 16,000.00$    EachPipe, C‐900, 12 Inch DiameterSS‐21 205.00$          LFOutside DropSS‐24 1,700.00$      LSInside DropSS‐25 1,150.00$      LSSewer Pipe, PVC, ____ Inch DiameterSS‐26Lift Station (Entire System)SS‐27LSSANITARY SEWER SUBTOTAL:24,350.00SALES TAX @ 10.1%2,459.35SANITARY SEWER TOTAL:26,809.35(B)(C)(D)(E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR SANITARY SEWERQuantity Remaining (Bond Reduction) (B)(C)Page 1 of 1Ref 8‐H Bond Quantity WorksheetSECTION II.e SANITARY SEWERUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/2022 1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430‐7200Date:Name:Project Name: PE Registration No:CED Plan # (LUA):Firm Name:CED Permit # (C):Firm Address:Site Address:Phone No.Parcel #(s):Email Address:Project Phase: Site Restoration/Erosion Sediment Control Subtotal(a)Existing Right‐of‐Way Improvements Subtotal(b)(b)71,688.31$Future Public Improvements Subtotal(c)‐$Stormwater & Drainage Facilities (Public & Private) Subtotal(d)(d)27,872.13$(e)(f)Site RestorationExisting Right‐of‐Way and Storm Drainage ImprovementsMaintenance Bond19,912.09$Bond Reduction2Construction Permit Bond Amount 3Minimum Bond Amount is $10,000.001 Estimate Only  ‐ May involve multiple and variable components, which will be established on an individual basis by Development Engineering.2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% willcover all remaining items to be constructed. 3 Required Bond Amounts are subject to review and modification by Development Engineering.* Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton.** Note: All prices include labor, equipment, materials, overhead, profit, and taxes. EST1((b) + (c) + (d)) x 20%‐$ MAINTENANCE BOND */**(after final acceptance of construction)43,179.57$ 71,688.31$ 135,404.6$43,179.57$ ‐$ $ 27,872.13‐$ 175,787.31$P (a) x 100%SITE IMPROVEMENT BOND QUANTITY WORKSHEET BOND CALCULATIONS6/6/2022STEVE WU38852Tendem engineering consultants incR((b x 150%) + (d x 100%))S(e) x 150% + (f) x 100%Bond Reduction: Existing Right‐of‐Way Improvements (Quantity Remaining)2Bond Reduction: Stormwater & Drainage Facilities (Quantity Remaining)2T(P +R ‐ S)Prepared by:Project InformationCONSTRUCTION BOND AMOUNT */**(prior to permit issuance)206‐795‐5674wu868good@outlook.comTran‐Nguyen Development##‐######3343901963FOR APPROVAL########8822 NE 178th St Bothell, WA 98011Page 1 of 1Ref 8‐H Bond Quantity WorksheetSECTION III. BOND WORKSHEETUnit Prices Updated: 01/07/2022Version: 01/07/2022Printed 6/5/2022 M2-05 – Catch Basins Maintenance Component Defect Conditions When Maintenance is Needed Results Expected When Maintenance is performed General Trash & Debris Trash or debris which is located immediately in front of the catch basin opening or is blocking inletting capacity of the basin by more than 10%. No Trash or debris located immediately in front of catch basin or on grate opening. Trash or debris (in the basin) that exceeds 60percent of the sump depth as measured from the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of six inches clearance from the debris surface to the invert of the lowest pipe. No trash or debris in the catch basin. Trash or debris in any inlet or outlet pipe blocking more than 1/3 of its height. Inlet and outlet pipes free of trash or debris. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within the catch basin. Sediment Sediment (in the basin) that exceeds 60percent of the sump depth as measured from the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of 6 inches clearance from the sediment surface to the invert of the lowest pipe. No sediment in the catch basin Structure Damage to Frame and/or Top Slab Top slab has holes larger than 2 square inches or cracks wider than 1/4 inch (Intent is to make sure no material is running into basin). Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than 3/4 inch of the frame from the top slab. Frame not securely attached Frame is sitting flush on the riser rings or top slab and firmly attached. Fractures or Cracks in Basin Walls/Bottom Maintenance person judges that structure is unsound. Basin replaced or repaired to design standards. Grout fillet has separated or cracked wider than 1/2 inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. Pipe is regrouted and secure at basin wall. Settlement/Misalignment If failure of basin has created a safety, function, or design problem. Basin replaced or repaired to design standards. Vegetation Vegetation growing across and blocking more than 10% of the basin opening. No vegetation blocking opening to basin. Vegetation growing in inlet/outlet pipe joints that is more than six inches tall and less than six inches apart. No vegetation or root growth present. 13 25 Figure 9 Maintenance and Operations Manual M2-05 – Catch Basins Maintenance Component Defect Conditions When Maintenance is Needed Results Expected When Maintenance is performed Contamination and Pollution See "Detention Ponds" (No. 1). No pollution present. Catch Basin Cover Cover Not in Place Cover is missing or only partially in place. Any open catch basin requires maintenance. Catch basin cover is closed Locking Mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts into frame have less than 1/2 inch of thread. Mechanism opens with proper tools. Cover Difficult to Remove One maintenance person cannot remove lid after applying normal lifting pressure. (Intent is keep cover from sealing off access to maintenance.) Cover can be removed by one maintenance person. Ladder Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, not securely attached to basin wall, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access. Metal Grates (If Applicable) Grate opening Unsafe Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and Debris Trash and debris that is blocking more than20% of grate surface inletting capacity. Grate free of trash and debris. Damaged or Missing. Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. M2-06 – Debris Barriers (e.g., Trash Racks) Maintenance Components Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed General Trash and Debris Trash or debris that is plugging more than 20% of the openings in the barrier. Barrier cleared to design flow capacity. Metal Damaged/ Missing Bars. Bars are bent out of shape more than 3 inches. Bars in place with no bends more than 3/4 inch. Bars are missing or entire barrier missing. Bars in place according to design. Bars are loose and rust is causing 50% deterioration to any part of barrier. Barrier replaced or repaired to design standards. Inlet/Outlet Pipe Debris barrier missing or not attached to pipe Barrier firmly attached to pipe 14 M2-02 - Infiltration Maintenance Component Defect Conditions When Maintenance Is Needed Results Expected WhenMaintenance Is Performed General Trash & Debris See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1). Poisonous/Noxious Vegetation See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1). Contaminants and Pollution See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1). Rodent Holes See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1) Storage Area Sediment Water ponding in infiltration pond after rainfall ceases and appropriate time allowed for infiltration. (A percolation test pit or test of facilityindicates facility is only working at 90% of its designed capabilities. If two inches or more sediment is present, remove). Sediment is removed and/or facility is cleaned so that infiltration system works according to design. Filter Bags (if applicable) Filled with Sediment and Debris Sediment and debris fill bag more than 1/2 full. Filter bag is replaced or system is redesigned. Rock Filters Sediment and Debris By visual inspection, little or no water flows through filter during heavy rain storms. Gravel in rock filter is replaced. Side Slopes of Pond Erosion See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1). EmergencyOverflow Spillwayand Berms over 4 feet in height. Tree Growth See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1). Piping See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1). EmergencyOverflow Spillway Rock Missing See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1). Erosion See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1). Pre-settling Ponds and Vaults Facility or sumpfilled with Sediment and/or debris 6" or designed sediment trap depth of sediment. Sediment is removed. 10 Figure 10 TIR Worksheet CITY OF RENTON SURFACE WATER DESIGN MANUAL 2017 City of Renton Surface Water Design Manual 12/12/2016 8-A-1 REFERENCE 8-A TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner _____________________________ Phone ___________________________________ Address __________________________________ _________________________________________ Project Engineer ___________________________ Company _________________________________ Phone ___________________________________ Project Name __________________________ CED Permit # ________________________ Location Township ________________ Range __________________ Section _________________ Site Address __________________________ _____________________________________ Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Land Use (e.g., Subdivision / Short Subd.) Building (e.g., M/F / Commercial / SFR) Grading Right-of-Way Use Other _______________________ DFW HPA COE 404 DOE Dam Safety FEMA Floodplain COE Wetlands Other ________ ShorelineManagement StructuralRockery/Vault/_____ ESA Section 7 Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review (check one): Date (include revision dates): Date of Final: Full Targeted Simplified Large Project Directed ____________________________________ __________________ Plan Type (check one): Date (include revision dates): Date of Final: Full Modified Simplified ____________________________________ __________________ Long & Vu Tran Nguyen 11904 SE 228th PL Kent WA 98031 206-384-3690 STEVE WU TEC INC 206-795-5674 TRAN-NGUYEN DEVELOPMENT LUA 21-000206 23N 5E 5 2309 ABERDEEN AVE NE RENTON WA 98056 X REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-2 Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Blanket Description: (include conditions in TIR Section 2) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Approved Adjustment No. ______________________ Date of Approval: _______________________ Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: _______________________ Completion Date: _______________________ Describe: _________________________________ _________________________________________ _________________________________________ Re: SWDM Adjustment No. ________________ Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: ____________________________________________________________________ Special District Overlays: ______________________________________________________________ Drainage Basin: _____________________________________________________________________ Stormwater Requirements: _____________________________________________________________ Part 9 ONSITE AND ADJACENT SENSITIVE AREAS River/Stream ________________________ Lake ______________________________ Wetlands ____________________________ Closed Depression ____________________ Floodplain ___________________________ Other _______________________________ _______________________________ Steep Slope __________________________ Erosion Hazard _______________________ Landslide Hazard ______________________ Coal Mine Hazard ______________________ Seismic Hazard _______________________ Habitat Protection ______________________ _____________________________________Aquifer Protection Zone 2 Lake Washington Core #1 to Core #9 REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-3 Part 10 SOILS Soil Type ______________________ ______________________ ______________________ ______________________ Slopes ________________________ ________________________ ________________________ ________________________ Erosion Potential _________________________ _________________________ _________________________ _________________________  High Groundwater Table (within 5 feet)  Other ________________________________  Sole Source Aquifer  Seeps/Springs  Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE  Core 2 – Offsite Analysis_________________  Sensitive/Critical Areas__________________  SEPA________________________________  LID Infeasibility________________________  Other________________________________  _____________________________________ LIMITATION / SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________  Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Core Requirements (all 8 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__________________ Flow Control (include facility summary sheet) Standard: _______________________________ or Exemption Number: ____________ On-site BMPs: _______________________________ Conveyance System Spill containment located at: _____________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ Level 1 Loamy Sand 5-15%Yes March 9, 2021 During Matching forested conditions Infiltation trenches and bioretention cell REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-4 Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. _______________________ Special Requirements (as applicable): Area Specific Drainage Requirements Type: SDO / MDP / BP / Shared Fac. / None Name: ________________________ Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): _______________ Datum: Flood Protection Facilities Describe: Source Control (commercial / industrial land use) Describe land use: Describe any structural controls: Oil Control High-Use Site: Yes / No Treatment BMP: _________________________________ Maintenance Agreement: Yes / No with whom? _____________________________________ Other Drainage Structures Describe: 1 REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-5 Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION  Clearing Limits  Cover Measures  Perimeter Protection  Traffic Area Stabilization  Sediment Retention  Surface Water Collection  Dewatering Control  Dust Control  Flow Control  Control Pollutants  Protect Existing and Proposed BMPs/Facilities  Maintain Protective BMPs / Manage Project MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION  Stabilize exposed surfaces  Remove and restore Temporary ESC Facilities  Clean and remove all silt and debris, ensure operation of Permanent BMPs/Facilities, restore operation of BMPs/Facilities as necessary  Flag limits of sensitive areas and open space preservation areas  Other _______________________ Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch) Flow Control Type/Description Water Quality Type/Description  Detention  Infiltration  Regional Facility  Shared Facility  On-site BMPs  Other ________________ ________________ ________________ ________________ ________________ ________________  Vegetated Flowpath  Wetpool  Filtration  Oil Control  Spill Control  On-site BMPs  Other ________________ ________________ ________________ ________________ ________________ ________________ ________________ Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS  Drainage Easement  Covenant  Native Growth Protection Covenant  Tract  Other ____________________________  Cast in Place Vault  Retaining Wall  Rockery > 4′ High  Structural on Steep Slope  Other _______________________________ Bioretention Cell Trenches REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-6 Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. ____________________________________________________________________________________ Signed/Date 12/26/2022 26 APPENDIX A Geotechnical Report 27 APPENDIX B Drainage, Cross-sections and Details Plans DATE: FIELDBOOK: DRAWING NO: PAGE: SHEET: OF: SCALE: DESIGNED: DRAWN: CHECKED: APPROVED:NO.REVISION BY DATE APPR FILENAME:SURVEYED: VERTICAL: NAVD 1988 IF NOT ONE INCH ONE INCH AT FULL SCALE HORIZONTAL: NAD 1983/1991 SCALE ACCORDINGLY DATUM Planning/Building/Public Works Dept. CITY OF RENTON IN COMPLIANCE WITH CITY OF RENTON STANDARDS DRAINAGE DETAILS PLAN TRAN-NGUYEN DEVELOPMENT C-19.0 19TED-40-4210R-421013 28 6/16/2022 28 APPENDIX C On-site BMPs Design Criteria StormFilter Catch Basin Basic treatment level WQ flowrate = 0.01 cfs Peak (100yr) flow = <1.0 cfs (1) 18” tall ZPG cartridges in a SFCB-Steel - Required drop of 2.3’ from rim to outlet invert Total structure depth of 3.75’ Permanent pool located 1’ below structure rim 29 APPENDIX D Declaration of Covenant for Maintenance and Inspection of On-site BMPs Page 1 of ___ Return Address: City Clerk’s Office City of Renton 1055 S Grady Way Renton, WA 98057 DECLARATION OF COVENANT FOR INSPECTION AND MAINTENANCE OF DRAINAGE FACILITIES AND ON-SITE BMPS Grantor: Grantee: City of Renton, a Washington municipal corporation Legal Description: Assessor's Tax Parcel ID#: IN CONSIDERATION of the approved City of Renton (check one of the following) Residential Building Permit Commercial Building Permit Clearing and Grading Permit Civil Construction or Utility Permit for Permit(s)_____________________ (Construction/Building/Utility Permit #) relating to the real property ("Property") described above, the Grantor(s), the owner(s) in fee of that Property, hereby covenants (covenant) with the City of Renton (“City of Renton” or “City”), a municipal corporation of the state of Washington, that he/she (they) will observe, consent to, and abide by the conditions and obligations set forth and described in Paragraphs 1 through 9 below with regard to the Property, and hereby grants (grant) an easement as described in Paragraphs 2 and 3. Grantor(s) hereby grants (grant), covenants (covenant), and agrees (agree) as follows: 1.The Grantor(s) or his/her (their) successors in interest and assigns ("Owners ") shall at their own cost, operate, maintain, and keep in good repair, the Property's drainage facilities constructed as required in the approved construction plans and specifications __________________ (Project Plan #) on file with the City of Renton and submitted to the City of Renton for the review and approval of permit(s) _____________________________ (Construction/Building/Utility Permit #). The Property's drainage facilities are shown and/or listed on Exhibit A – Site Plan. The Property’s drainage facilities shall be maintained in compliance with the operation and maintenance schedule included and attached herein as Exhibit B – Operations and Maintenance. Drainage facilities include pipes, channels, flow control facilities, water quality facilities, on-site best management practices (BMPs) and other engineered structures designed to manage and/or Page 2 of ___ treat stormwater on the Property. On-site BMPs include dispersion and infiltration devices, bioretention, permeable pavements, rainwater harvesting systems, tree retention credit, reduced impervious surface footprint, vegetated roofs and other measures designed to mimic pre-developed hydrology and minimize stormwater runoff on the Property. 2.City of Renton shall have the right to ingress and egress over those portions of the Property necessary to perform inspections of the stormwater facilities and BMPs and conduct maintenance activities specified in this Declaration of Covenant and in accordance with the Renton Municipal Code. City of Renton shall provide at least thirty (30) days’ written notice to the Owners that entry on the Property is planned for the inspection of drainage facilities. After the thirty (30) days, the Owners shall allow the City of Renton to enter for the sole purpose of inspecting drainage facilities. In lieu of inspection by the City, the Owners may elect to engage a licensed civil engineer registered in the state of Washington who has expertise in drainage to inspect the drainage facilities and provide a written report describing their condition. If the engineer option is chosen, the Owners shall provide written notice to the City of Renton within fifteen (15) days of receiving the City’s notice of inspection. Within thirty (30) days of giving this notice, the Owners, or engineer on behalf of the Owners, shall provide the engineer’s report to the City of Renton. If the report is not provided in a timely manner as specified above, the City of Renton may inspect the drainage facilities without further notice. 3.If City of Renton determines from its inspection, or from an engineer’s report provided in accordance with Paragraph 2, that maintenance, repair, restoration, and/or mitigation work is required to be done to any of the drainage facilities, City of Renton shall notify the Owners of the specific maintenance, repair, restoration, and/or mitigation work (“Work”) required pursuant to the Renton Municipal Code. The City shall also set a reasonable deadline for the Owners to complete the Work, or to provide an engineer’s report that verifies completion of the Work. After the deadline has passed, the Owners shall allow the City access to re-inspect the drainage facilities unless an engineer’s report has been provided verifying completion of the Work. If the Work is not completed within the time frame set by the City, the City may initiate an enforcement action and/or perform the Work and hereby is given access to the Property for such purposes. Written notice will be sent to the Owners stating the City’s intention to perform such Work. This Work will not commence until at least seven (7) days after such notice is mailed. If, within the sole discretion of the City, there exists an imminent or present danger, the seven (7) day notice period will be waived and Work will begin immediately. 4.The Owners shall assume all responsibility for the cost of any Work, or any measures taken by the City to address conditions as described in Paragraph 3. Such responsibility shall include reimbursement to the City within thirty (30) days of the receipt of the invoice for any such Work performed. Overdue payments will require payment of interest at the maximum legal rate allowed by RCW 19.52.020 (currently twelve percent (12%)). If the City initiates legal action to enforce this agreement, the prevailing party in such action is entitled to recover reasonable litigation costs and attorney’s fees. 5.The Owners are required to obtain written approval from City of Renton prior to filling, piping, cutting, or removing vegetation (except in routine landscape maintenance) in open vegetated stormwater facilities (such as swales, channels, ditches, ponds, etc.), or performing any alterations or modifications to the drainage facilities referenced in this Declaration of Covenant. Page 3 of ___ 6.Any notice or consent required to be given or otherwise provided for by the provisions of this Agreement shall be effective upon personal delivery, or three (3) days after mailing by Certified Mail, return receipt requested. 7.With regard to the matters addressed herein, this agreement constitutes the entire agreement between the parties, and supersedes all prior discussions, negotiations, and all agreements whatsoever whether oral or written. 8.This Declaration of Covenant is intended to protect the value and desirability and promote efficient and effective management of surface water drainage of the real property described above, and shall inure to the benefit of all the citizens of the City of Renton and its successors and assigns. This Declaration of Covenant shall run with the land and be binding upon Grantor(s), and Grantor's(s') successors in interest, and assigns. 9.This Declaration of Covenant may be terminated by execution of a written agreement by the Owners and the City that is recorded by King County in its real property records. IN WITNESS WHEREOF, this Declaration of Covenant for the Inspection and Maintenance of Drainage Facilities is executed this _____ day of ____________________, 20_____. GRANTOR, owner of the Property GRANTOR, owner of the Property STATE OF WASHINGTON ) COUNTY OF KING )ss. On this day personally appeared before me: , to me known to be the individual(s) described in and who executed the within and foregoing instrument and acknowledged that they signed the same as their free and voluntary act and deed, for the uses and purposes therein stated. Given under my hand and official seal this _____ day of ___________________, 20_____. Printed name Notary Public in and for the State of Washington, residing at My appointment expires Page 4 of ___ Exhibit A – Site Plan Please replace this page with “Exhibit A - Site Plan” that is prepared in accordance with the Renton Surface Water Design Manual Appendix C Section C.4. See Example Declaration of Covenant for help preparing this document. Page 5 of ___ Exhibit B – Operations and Maintenance Please replace this page with all applicable “Exhibit B – Operations and Maintenance” Details referenced in the Renton Surface Water Design Manual Reference 8-M that are proposed to be constructed on the project site. See Example Declaration of Covenant for help preparing this document. Page 6 of ___ Exhibit C – Legal Description Please replace this page with “Exhibit C – Legal Description” if the property legal description does not fit within the space provided on Page 1 of the Declaration of Covenant. Add reference to “Exhibit C” in the legal description field on page 1 of the Declaration of Covenant document. 32 APPENDIX E Continuous Model Out for Infiltration Trenches ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.52 Program License Number: 300210203 Project Simulation Performed on: 03/12/2022 4:19 PM Report Generation Date: 03/12/2022 4:20 PM ————————————————————————————————— Input File Name: Infiltration trench.fld Project Name: Renton Analysis Title: Infiltration Trench Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 32 Full Period of Record Available used for Routing Precipitation Station : 99003805 Seattle 38 in_5min 10/01/1939-10/01/2097 Evaporation Station : 991038 Seattle 38 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.092 0.092 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 0.092 0.092 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Forest 0.092 ---------------------------------------------- Subbasin Total 0.092 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Impervious 0.092 ---------------------------------------------- Subbasin Total 0.092 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Infilt Trench Lnk1 Link Type: Infiltration Trench Downstream Link: None Trench Type : Trench on Embankment Sideslope Trench Length (ft) : 20.00 Trench Width (ft) : 10.00 Trench Depth (ft) : 2.00 Trench Bottom Elev (ft) : 100.00 Trench Rockfill Porosity (%) : 30.00 Hydraulic Conductivity (in/hr) : 6.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 1 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 15.011 _____________________________________ Total: 15.011 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 Link: New Infilt Trench Ln 38.958 _____________________________________ Total: 38.958 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.095 ac-ft/year, Post Developed: 0.247 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ********** Link: New Infilt Trench Lnk1 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 38.96 Inflow Volume Including PPT-Evap (ac-ft): 38.96 Total Runoff Infiltrated (ac-ft): 38.96, 100.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 0.00 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Link: New Infilt Trench Lnk1 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 1.992E-03 2-Year 0.000 5-Year 3.111E-03 5-Year 0.000 10-Year 3.987E-03 10-Year 0.000 25-Year 5.275E-03 25-Year 0.000 50-Year 5.548E-03 50-Year 0.000 100-Year 7.858E-03 100-Year 0.000 200-Year 1.236E-02 200-Year 9.203E-03 500-Year 1.833E-02 500-Year 2.160E-02 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -100.0% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -100.0% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -61.0% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -100.0% PASS Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -100.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL LID DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.52 Program License Number: 200210003 Project Simulation Performed on: 05/09/2022 3:36 PM Report Generation Date: 05/09/2022 3:37 PM ————————————————————————————————— Input File Name: Infiltration trench - Access Road.fld Project Name: Renton Analysis Title: Infiltration Trench Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 32 Full Period of Record Available used for Routing Precipitation Station : 99003805 Seattle 38 in_5min 10/01/1939-10/01/2097 Evaporation Station : 991038 Seattle 38 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.104 0.104 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 0.104 0.104 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Forest 0.104 ---------------------------------------------- Subbasin Total 0.104 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Impervious 0.104 ---------------------------------------------- Subbasin Total 0.104 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Infilt Trench Lnk1 Link Type: Infiltration Trench Downstream Link: None Trench Type : Trench on Embankment Sideslope Trench Length (ft) : 22.00 Trench Width (ft) : 10.00 Trench Depth (ft) : 2.00 Trench Bottom Elev (ft) : 100.00 Trench Rockfill Porosity (%) : 30.00 Hydraulic Conductivity (in/hr) : 6.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 1 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 17.006 _____________________________________ Total: 17.006 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 Link: New Infilt Trench Ln 44.136 _____________________________________ Total: 44.136 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.108 ac-ft/year, Post Developed: 0.279 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ********** Link: New Infilt Trench Lnk1 ********** Basic Wet Pond Volume (91% Exceedance): 483. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 725. cu-ft 2-Year Discharge Rate : 0.000 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.01 cfs Off-line Design Discharge Rate (91% Exceedance): 0.01 cfs Time to Infiltrate 91% Treatment Volume, (Hours): 3.66 Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 44.14 Inflow Volume Including PPT-Evap (ac-ft): 44.14 Total Runoff Infiltrated (ac-ft): 44.14, 100.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 0.00 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Link: New Infilt Trench Lnk1 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 2.257E-03 2-Year 0.000 5-Year 3.524E-03 5-Year 0.000 10-Year 4.516E-03 10-Year 0.000 25-Year 5.976E-03 25-Year 0.000 50-Year 6.285E-03 50-Year 0.000 100-Year 8.902E-03 100-Year 1.087E-02 200-Year 1.400E-02 200-Year 1.625E-02 500-Year 2.077E-02 500-Year 2.309E-02 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -100.0% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -100.0% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -2.6% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -100.0% PASS Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -100.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL LID DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- 32 APPENDIX F Stormwater Pollution Prevention Plan (SWPPP) extracted Construction Stormwater General Permit Stormwater Pollution Prevention Plan (SWPPP) for 2309 Aberdeen Renton, WA 98056 Prepared for: The Washington State Department of Ecology NORTHWEST REGIONAL OFFICE Permittee / Owner Developer Operator / Contractor Long Ngugyen Wei Huang Update as necessary. Certified Erosion and Sediment Control Lead (CESCL) Name Organization Contact Phone Number JIM WU TEC 206-383-8867 SWPPP Prepared By Name Organization Contact Phone Number STEVE WU TEC 206-795-5674 SWPPP Preparation Date 08/08/2021 Project Construction Dates Activity / Phase Start Date End Date 4/1/2021 12/31/2022 Page | 1 Table of Contents 1 Project Information ................................................................................................................. 4 1.1 Existing Conditions ......................................................................................................... 4 1.2 Proposed Construction Activities .................................................................................... 4 2 Construction Stormwater Best Management Practices (BMPs) .............................................. 2.1 The 13 Elements ............................................................................................................ 6 2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits .......................................... 6 2.1.2 Element 2: Establish Construction Access .............................................................. 7 2.1.3 Element 3: Control Flow Rates ................................................................................ 8 2.1.4 Element 4: Install Sediment Controls ...................................................................... 9 2.1.5 Element 5: Stabilize Soils ...................................................................................... 10 2.1.6 Element 6: Protect Slopes ..................................................................................... 11 2.1.7 Element 7: Protect Drain Inlets .............................................................................. 12 2.1.8 Element 8: Stabilize Channels and Outlets ........................................................... 13 2.1.9 Element 9: Control Pollutants ................................................................................ 14 2.1.10 Element 10: Control Dewatering ........................................................................... 16 2.1.11 Element 11: Maintain BMPs .................................................................................. 17 2.1.12 Element 12: Manage the Project ........................................................................... 18 2.1.13 Element 13: Protect on-site Stormwater Management BMPs for Runoff from roof and other Surface ................................................................................................................ 18 3 Pollution Prevention Team ................................................................................................... 19 4 Monitoring and Sampling Requirements .............................................................................. 20 4.1 Site Inspection .............................................................................................................. 20 4.2 Stormwater Quality Sampling ....................................................................................... 20 4.2.1 Turbidity Sampling ................................................................................................. 20 4.2.2 pH Sampling .......................................................................................................... 22 5 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies ......................... 23 5.1 303(d) Listed Waterbodies ........................................................................................... 23 5.2 TMDL Waterbodies ....................................................................................................... 23 6 Reporting and Record Keeping ........................................................................................... 24 6.1 Record Keeping ............................................................................................................ 24 6.1.1 Site Log Book ........................................................................................................ 24 6.1.2 Records Retention ................................................................................................. 24 6.1.3 Updating the SWPPP ............................................................................................ 24 6.2 Reporting ...................................................................................................................... 25 6.2.1 Discharge Monitoring Reports ............................................................................... 25 Page | 2 6.2.2 Notification of Noncompliance ............................................................................... 25 List of Tables Table 1 – pH-Modifying Sources ................................................................................................. 14 Table 2 – Management ............................................................................................................... 18 Table 3 – Team Information ........................................................................................................ 19 Table 4 – pH Sampling Method .................................................................................................. 22 List of Appendices Appendix/Glossary A. Site Map B. BMP Detail C. Site Inspection Form D. Sediment Trap Calculation Page | 3 List of Acronyms and Abbreviations Acronym / Abbreviation Explanation 303(d) Section of the Clean Water Act pertaining to Impaired Waterbodies BFO Bellingham Field Office of the Department of Ecology BMP(s) Best Management Practice(s) CESCL Certified Erosion and Sediment Control Lead CO2 Carbon Dioxide CRO Central Regional Office of the Department of Ecology CSWGP Construction Stormwater General Permit CWA Clean Water Act DMR Discharge Monitoring Report DO Dissolved Oxygen Ecology Washington State Department of Ecology EPA United States Environmental Protection Agency ERO Eastern Regional Office of the Department of Ecology ERTS Environmental Report Tracking System ESC Erosion and Sediment Control GULD General Use Level Designation NPDES National Pollutant Discharge Elimination System NTU Nephelometric Turbidity Units NWRO Northwest Regional Office of the Department of Ecology pH Power of Hydrogen RCW Revised Code of Washington SPCC Spill Prevention, Control, and Countermeasure su Standard Units SWMMEW Stormwater Management Manual for Eastern Washington SWMMWW Stormwater Management Manual for Western Washington SWPPP Stormwater Pollution Prevention Plan TESC Temporary Erosion and Sediment Control SWRO Southwest Regional Office of the Department of Ecology TMDL Total Maximum Daily Load VFO Vancouver Field Office of the Department of Ecology WAC Washington Administrative Code WSDOT Washington Department of Transportation WWHM Western Washington Hydrology Model Page | 4 Project Information Project/Site Name: Ning Workshop Street/Location: 221 Nyden Farms Rd City: Medina State: WA Zip code: 98258 Subdivision: Receiving waterbody: Lake Stevens Existing Conditions Total acreage (including support activities such as off-site equipment staging yards, material storage areas, borrow areas). Total acreage: 0.857 Disturbed acreage: 0.71 Existing structures: No existing structure on site. Landscape topography: Vegegations, tress, and brushes Drainage patterns: On site infiltration or sheets flows to the frontage road. Existing Vegetation: Well maintenance grass, brushes, and some trees. Critical Areas (wetlands, streams, high erosion risk, steep or difficult to stabilize slopes): No sensitive areas on site. List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the receiving waterbody: N/A Proposed Construction Activities Description of site development (example: subdivision): This project will subdivide the existing lot into three lots. The scope of this project will include gradation, construction of driveway, bioretention cell, installation of utilities, and build the sidewalk with planter along the property line on Aberdeen Ave NE. The site gradation will not impact adjacent to the neiborthood properties. existing contour is not expected to alter. No impact to the wetland. Description of construction activities (example: site preparation, demolition, excavation): Construction activities will include site preparation, TESC installation, site grade, excavation for the bioretention cell, and construct a 20’ width with 149’ in length driveway to connect with Aberdeen Ave NE. Description of site drainage including flow from and onto adjacent properties. Must be consistent with Site Map in Appendix A: No on site flow or onto adjacent properties. The site is covered with vegetations, on site infiltration is implement. The site slopes gently downward from west to east and northeast at magnitudes of 5 to 10 percent. Page | 5 Description of final stabilization (example: extent of revegetation, paving, landscaping): After the site graded, 20’ access paved road build, bioretention cell built, and all utilites are installed run off. The whole site will be covered by vegetations and trees. No bare ground will be exposed to the air. The bioretention cell will collect the access road run offs. Contaminated Site Information: Proposed activities regarding contaminated soils or groundwater (example: on-site treatment system, authorized sanitary sewer discharge): No on site contaminated materials are expected after completion of this project. sanitary sewer will connect with exiting setics on site. Page | 6 The SWPPP is a living document reflecting current conditions and changes throughout the life of the project. These changes may be informal (i.e., hand-written notes and deletions). Update the SWPPP when the CESCL has noted a deficiency in BMPs or deviation from original design. The 13 Elements Element 1: Preserve Vegetation / Mark Clearing Limits There are no wetlands, streams or sensitive areas near the clearing limits. To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land-disturbing activities begin. Existing vegetation (trees, bushes, shrubs, grasses) shall be preserved when removal is not necessary for the construction of the project. The contractor is required to survey, stake, and flag the clearing limits shown in the plans and/or areas not to be disturbed including easements, setbacks, sensitive and critical areas and their buffers, and drainage courses before any clearing or grubbing can begin. List and describe BMPs: Silt Fence will be installed prior any construction activites, high visible fence will be installed around the trees. Installation Schedules: Prior any construction activities. Inspection and Maintenance plan: Inspect silt fence once a week, replace any boken fence or any wear out. Responsible Staff: Jim W Page | 7 Element 2: Establish Construction Access The risk associated with establishing the construction access to the project is considered very low. The contractor is require to stabilize identified construction access points and need to be installed prior to major grading operations. Construction vehicles entering and exiting the project site and staging areas will use only identified access points. Sediment track out onto the street will be eliminated by effective implementation of construction road and entrance stabilization measures installed per Ecology BMP C105 Stabilized Construction Entrance. The construction entrance will be stabilized with quarry spalls/crushed rock or construction entrance plates to reduce the amount of sediment transported onto paved roads by vehicles or equipment. Properly maintained stabilized construction entrances and construction entrance plates should prevent track out under normal conditions. If track out is observed at any time onto offsite pavement, the road will be thoroughly cleaned as frequently as necessary. At a minimum, the streets will be cleaned at the end of each working day. Sediment will be removed from the roads by shoveling or sweeping. Soils collected by the street sweeper and any water used by the sweeper equipment are considered to be contaminated and will be collected and disposed of at an approved disposal facility. List and describe BMPs: Construction Entrance will be implement for this job site prior any construction activity. Street cleaning will be implement if necessary. Installation Schedules: Prior any construction activies. Inspection and Maintenance plan: check the construction entrance as least once a week. Responsible Staff: Jim Wu Page | 8 Element 3: Control Flow Rates The riskes associated with uncontrolled flow rates for this project is very low. The entire project site is covered by vegations and surrounding with private proerities, each with its own stormwater runoff drainage system draining to the public storm water main and on site infiltration. Will you construct stormwater retention and/or detention facilities? No. Detention is not required for this project. Will you use permanent infiltration ponds or other low impact development (example: rain gardens, bio-retention, porous pavement) to control flow during construction? infiltration trench will be used as temporary on site BMP as needed. No permanent infiltration pond or other low impact development BMP will be insalled after completion of the project. List and describe BMPs: Temporary infiltration trench, sediment traps. Installation Schedules: During construction Inspection and Maintenance plan: use DOE manual as guildlines Responsible Staff: Jim Wu Page | 9 Element 4: Install Sediment Controls Sediment control BMPs will be installed prior to soil disturbing activities, where feasible. Inlet protection will be provided for all existing and proposed catch basins in the project area and it vicinity to reduce the amount of sediment entering the conveyance system. . Any temporarily unworked or exposed soil on the project site will be covered by plastic covering or other approved equivalent to prevent the release of sediment into air or conveyance system. Construction stormwater runoff that has not contacted disturbed areas or that passes over fully stabilized areas will be protected from contamination, and where practical will be passed directly through the project site for discharge to the appropriate conveyance system as per permit requirement. Silt fence will also be used along the perimeter of the construction activities to help stabilize soils. The silt fence installation will be coordinated with installation of security fence, construction or other type of fencing. Any offsite flow (run-on) onto construction site will be diverted to downstream natural flow path using temporary curbs, asphalt berms or sand bags. To the maximum extent possible, sheet flow will be maintained, as sheet flow greatly reduces the potential for erosion and sediment transport. Silt fence and inlet protection will be used to settle out the sediment before discharging to an approved discharge locations. Street sweeping by dry sweeping, manual shoveling or street sweeper/scrubber will be employed to remove the sediment on roads. Water may be used for fugitive dust control on the project site. List and describe BMPs: Dust control, Materials on Hand, Nets and Blankets, Plastic covering. Storm Drain Inlet Protection, sediment trap will be established during construction. Installation Schedules: Prior construction and during construction for all BMPs listed above. Inspection and Maintenance plan: Check all BMPs at least once a week. Responsible Staff: JW Page | 10 Element 5: Stabilize Soils The risks associated with stabilizing the on-site soils are considered moderate. This project is scheduled to disturb approximately 0.7 acres of soil beginning in june 2022 and construction will last for 3 months. The amount of exposed soil will be limited. The amount of exposed or unworked soil in the working area will be limited to the amounts specified in the WSDOT Standard Specification 8-01.3(1). West of the Cascade Mountains Crest Season Dates Number of Days Soils Can be Left Exposed During the Dry Season May 1 – September 30 7 days During the Wet Season October 1 – April 30 2 days Soils must be stabilized at the end of the shift before a holiday or weekend if needed based on the weather forecast. Anticipated project dates: Start date: October 2021. End date: June, 2022. Will you construct during the wet season? No. No excavation will be anticipated during the wet seasion. List and describe BMPs: Materials on Hand, Nets and blankets, Plastic Covering, Top soiling, Dust Control, Schedule. Seeding. Installation Schedules: Prior construction activities and during construction. Inspection and Maintenance plan: Check all BMPs at least once a week. Responsible Staff: JW. Page | 11 Element 6: Protect Slopes The risk associated with the protection of slope is low. This project constructs cut and fill for the site gradation, bioretention cell, and driveway. No more than 3’ cut will be expected. They will have erosion control BMPs installed for slope protection as need. Cut and fill slopes will be constructed to minimize erosion. During the construction, plastic covering or other suitable cover material shall be applied to the exposed slopes. Finished slopes shall have permanent seeding or other vegetation applied. Any stockpiles on site will be located away from the storm drains inlets and drainage channels. Offsite run-on, if any, will be diverted away from slopes and disturbed areas with temporary curbs or sand bags. Will steep slopes be present at the site during construction? No. the site is realitive flat. List and describe BMPs: Nets and Blankets, Plastic Covering, seeding. Installation Schedules: Prior construction and during construction Inspection and Maintenance plan: Inspect all BMPs at least once a week and replace them as necessary. Responsible Staff: On site TESC lead. Page | 12 Element 7: Protect Drain Inlets Associated construction activities have no risk of potentially affecting water quality in Lake Stevens. All existing and proposed storm drains within the project site and in the vicinity of the project site will be protected by using storm drain inlet protection. This BMP is intended to trap sediment onsite and will be installed and be functional prior to any work or other land disturbing activities take place. The inlet protection will be properly maintained to ensure that inlets are functioning correctly. Inlets should be inspected weekly at the minimum and daily during storm events. Inlet protection devices should be cleaned or removed and replaced when sediment has filled one-third of the available storage (unless a different standard is specified by the product manufacturer). List and describe BMPs: Storm Drain Inlet Protection Installation Schedules: Prior construction Inspection and Maintenance plan: Check the Inlet Protection at least once a week, replace it as necessary. Responsible Staff: On site TESC personnel. Page | 13 Element 8: Stabilize Channels and Outlets No existing channels or outlets are located in the project area. Currently, no temporary conveyance channels are proposed on the TESC Plan Sheets. Since the project limits are completely flat and no offsite flows are expected into the site, any precipitation that falls on the site will not leave the construction area. If in situations where stormwater is observed to leave the site, trenches will be constructed at the perimeter of the project areas to collect the stormwater before it leaves the construction site. The trenches will then be used to convey (either by pumping or gravity flow) the stormwater to the portable storage and treatment system for testing and treatment if necessary prior to discharge to approved discharge location. Provide stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes, and downstream reaches, will be installed at the outlets of all conveyance systems. List and describe BMPs: N/A Installation Schedules: Inspection and Maintenance plan: Responsible Staff: Page | 14 Element 9: Control Pollutants The risk associated with pollutants from construction activities within project area is lowed. Procedures to prevent and control pollutants and handling of concrete and contaminated material are described in the Spill Prevention, Control, and Countermeasures (SPCC) Plan and the Concrete Containment and Disposal Plan (CCDP) prepared by the Contractor. List and describe BMPs: Dust Control, Concrete Handling, Material Delivery, Storage and Containment Installation Schedules: Installed prior construction or during construction. Inspection and Maintenance plan: Check BMPs at least once a week and replace them as necessary. Responsible Staff: On site TESC lead Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site? No List and describe BMPs: N/A Installation Schedules: Inspection and Maintenance plan: Responsible Staff: Will wheel wash or tire bath system BMPs be used during construction? No List and describe BMPs: N/A Installation Schedules: Inspection and Maintenance plan: Responsible Staff: Will pH-modifying sources be present on-site? No Table 1 – pH-Modifying Sources X None Bulk cement Cement kiln dust Fly ash Other cementitious materials New concrete washing or curing waters Waste streams generated from concrete grinding and sawing Exposed aggregate processes Page | 15 Dewatering concrete vaults Concrete pumping and mixer washout waters Recycled concrete Recycled concrete stockpiles Other (i.e., calcium lignosulfate) [please describe: ] List and describe BMPs: N/A Installation Schedules: Inspection and Maintenance plan: Responsible Staff: Concrete trucks must not be washed out onto the ground, or into storm drains, open ditches, streets, or streams. Excess concrete must not be dumped on-site, except in designated concrete washout areas with appropriate BMPs installed. Will uncontaminated water from water-only based shaft drilling for construction of building, road, and bridge foundations be infiltrated provided the wastewater is managed in a way that prohibits discharge to surface waters? No List and describe BMPs: N/A Installation Schedules:N/A Inspection and Maintenance plan: Responsible Staff: Page | 16 Element 10: Control Dewatering No Dewatering will be taking place for this project. The ground water table is present in the project area is approximately elevation 5 to 7 feet, it depends on the time of year. The house footing foundation is 1.5 feet below surface, so no dewatering will be expected for this project. List and describe BMPs: N/A Installation Schedules: Inspection and Maintenance plan: Responsible Staff: Page | 17 Element 11: Maintain BMP The associate risk from sediment entering Lake Washington from the construction site is very low. All temporary and permanent Erosion and Sediment Control (ESC) BMPs shall be maintained and repaired as needed to ensure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with each particular BMP specification (see Volume II of the SWMMWW or Chapter 7 of the SWMMEW). Visual monitoring of all BMPs installed at the site will be conducted at least once every calendar week and within 24 hours of any stormwater or non-stormwater discharge from the site. If the site becomes inactive and is temporarily stabilized, the inspection frequency may be reduced to once every calendar month. All temporary ESC BMPs shall be removed within 30 days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be stabilized on-site or removed. Disturbed soil resulting from removal of either BMPs or vegetation shall be permanently stabilized. Additionally, protection must be provided for all BMPs installed for the permanent control of stormwater from sediment and compaction. BMPs that are to remain in place following completion of construction shall be examined and restored to full operating condition. If sediment enters these BMPs during construction, the sediment shall be removed and the facility shall be returned to conditions specified in the construction documents. Page | 18 Element 12: Manage the Project The project will be managed based on the following principles: • Projects will be phased to the maximum extent practicable and seasonal work limitations will be taken into account. • Inspection and monitoring: o Inspection, maintenance and repair of all BMPs will occur as needed to ensure performance of their intended function. o Site inspections and monitoring will be conducted in accordance with Special Condition S4 of the CSWGP. Sampling locations are indicated on the Site Map. Sampling station(s) are located in accordance with applicable requirements of the CSWGP. • Maintain an updated SWPPP. o The SWPPP will be updated, maintained, and implemented in accordance with Special Conditions S3, S4, and S9 of the CSWGP. As site work progresses the SWPPP will be modified routinely to reflect changing site conditions. The SWPPP will be reviewed monthly to ensure the content is current. Table 2 – Management X Design the project to fit the existing topography, soils, and drainage patterns X Emphasize erosion control rather than sediment control X Minimize the extent and duration of the area exposed X Keep runoff velocities low X Retain sediment on-site X Thoroughly monitor site and maintain all ESC measures X Schedule major earthwork during the dry season Other (please describe) Element 13: Protect on-site stormwater management BMPs for runoff from roofs and other hard surface Infiltration Trench is proposed BMPs for the roof runff, storm filter catch basin will catch the driveay runoff from the driveway, then converys to infiltration trench. Protect all BMPs assicated with bioretention cell during construction activities. Excavate bioretention cell area to final grade only after all disturbed areas in the updgardient project drainage area have been permanently stabilized. No excavation of bioretention areas during wet or saturated conditions. Operate machinery outsid of bioretention cell area during the construction. If BMPs are impacted during construction, restore them to their original condition or design requirements. Page | 19 Pollution Prevention Team Table 3 – Team Information Title Name(s) Phone Number Certified Erosion and Sediment Control Lead (CESCL) Jim WU 206-383-8867 Resident Engineer Steve WU 206-795-5674 Emergency Ecology Contact Northwest Regional Office 425-649-7000 Emergency Permittee/ Owner Contact Tran Vu 206-384-3690 Non-Emergency Owner Contact Steve WU 206-795-5674 Monitoring Personnel Jim Wu 206-383-8867 Ecology Regional Office Northwest Regional Office 425-649-7000 Page | 20 Monitoring and Sampling Requirements Monitoring includes visual inspection, sampling for water quality parameters of concern, and documentation of the inspection and sampling findings in a site log book. A site log book will be maintained for all on-site construction activities and will include: •A record of the implementation of the SWPPP and other permit requirements •Site inspections •Stormwater sampling data Create your own Site Inspection Form or use the Construction Stormwater Site Inspection Form found on Ecology’s website. http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html File a blank form under Appendix D. The site log book must be maintained on-site within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. Numeric effluent limits may be required for certain discharges to 303(d) listed waterbodies. See CSWGP Special Condition S8 and Section 5 of this template. Site Inspection Site inspections will be conducted at least once every calendar week and within 24 hours following any discharge from the site. For sites that are temporarily stabilized and inactive, the required frequency is reduced to once per calendar month. The discharge point(s) are indicated on the Site Map (see Appendix A) and in accordance with the applicable requirements of the CSWGP. Stormwater Quality Sampling Turbidity Sampling Requirements include calibrated turbidity meter or transparency tube to sample site discharges for compliance with the CSWGP. Sampling will be conducted at all discharge points at least once per calendar week. Method for sampling turbidity: N/A for this project. If the discharge’s turbidity is 26 to 249 NTU or the transparency is less than 33 cm but equal to or greater than 6 cm, the following steps will be conducted: 1.Review the SWPPP for compliance with Special Condition S9. Make appropriate revisions within 7 days of the date the discharge exceeded the benchmark. 2.Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary Page | 21 treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period. 3. Document BMP implementation and maintenance in the site log book. If the turbidity exceeds 250 NTU or the transparency is 6 cm or less at any time, the following steps will be conducted: 1. Telephone or submit an electronic report to the applicable Ecology Region’s Environmental Report Tracking System (ERTS) within 24 hours. • Central Region (Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, Yakima): (509) 575-2490 or http://www.ecy.wa.gov/programs/spills/forms/nerts_online/CRO_nerts_online.html • Eastern Region (Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman): (509) 329-3400 or http://www.ecy.wa.gov/programs/spills/forms/nerts_online/ERO_nerts_online.html • Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish, Whatcom): (425) 649-7000 or http://www.ecy.wa.gov/programs/spills/forms/nerts_online/NWRO_nerts_online.html • Southwest Region (Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Lewis, Mason, Pacific, Pierce, Skamania, Thurston, Wahkiakum,): (360) 407-6300 or http://www.ecy.wa.gov/programs/spills/forms/nerts_online/SWRO_nerts_online.html 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period 3. Document BMP implementation and maintenance in the site log book. 4. Continue to sample discharges daily until one of the following is true: • Turbidity is 25 NTU (or lower). • Transparency is 33 cm (or greater). • Compliance with the water quality limit for turbidity is achieved. o 1 - 5 NTU over background turbidity, if background is less than 50 NTU o 1% - 10% over background turbidity, if background is 50 NTU or greater • The discharge stops or is eliminated. Page | 22 pH Sampling pH monitoring is required for “Significant concrete work” (i.e., greater than 1000 cubic yards poured concrete over the life of the project). The use of recycled concrete or engineered soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD] or fly ash) also requires pH monitoring. For significant concrete work, pH sampling will start the first day concrete is poured and continue until it is cured, typically three (3) weeks after the last pour. For engineered soils and recycled concrete, pH sampling begins when engineered soils or recycled concrete are first exposed to precipitation and continues until the area is fully stabilized. If the measured pH is 8.5 or greater, the following measures will be taken: 1.Prevent high pH water from entering storm sewer systems or surface water. 2.Adjust or neutralize the high pH water to the range of 6.5 to 8.5 su using appropriatetechnology such as carbon dioxide (CO2) sparging (liquid or dry ice). 3.Written approval will be obtained from Ecology prior to the use of chemical treatment other than CO2 sparging or dry ice. Method for sampling pH: N/A for this project. Table 4 – pH Sampling Method pH meter pH test kit X Wide range pH indicator paper Page | 23 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies 303(d) Listed Waterbodies Circle the applicable answer, if necessary: Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH? No TMDL Waterbodies Waste Load Allocation for CWSGP discharges: N/A List and describe BMPs: Discharges to TMDL receiving waterbodies will meet in-stream water quality criteria at the point of discharge. The Construction Stormwater General Permit Proposed New Discharge to an Impaired Water Body form is included in Appendix F. Page | 24 Reporting and Record Keeping Record Keeping Site Log Book A site log book will be maintained for all on-site construction activities and will include: •A record of the implementation of the SWPPP and other permit requirements •Site inspections •Sample logs Records Retention Records will be retained during the life of the project and for a minimum of three (3) years following the termination of permit coverage in accordance with Special Condition S5.C of the CSWGP. Permit documentation to be retained on-site: •CSWGP •Permit Coverage Letter •SWPPP •Site Log Book Permit documentation will be provided within 14 days of receipt of a written request from Ecology. A copy of the SWPPP or access to the SWPPP will be provided to the public when requested in writing in accordance with Special Condition S5.G.2.b of the CSWGP. Updating the SWPPP The SWPPP will be modified if: •Found ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. •There is a change in design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the State. The SWPPP will be modified within seven (7) days if inspection(s) or investigation(s) determine additional or modified BMPs are necessary for compliance. An updated timeline for BMP implementation will be prepared. Page | 25 Reporting Discharge Monitoring Reports Cumulative soil disturbance is less than one (1) acre; therefore, Discharge Monitoring Reports (DMRs) will not be submitted to Ecology because water quality sampling is not being conducted at the site. Notification of Noncompliance If any of the terms and conditions of the permit is not met, and the resulting noncompliance may cause a threat to human health or the environment, the following actions will be taken: 1.Ecology will be notified within 24-hours of the failure to comply by calling the applicable Regional office ERTS phone number (Regional office numbers listed below). 2.Immediate action will be taken to prevent the discharge/pollution or otherwise stop or correct the noncompliance. If applicable, sampling and analysis of any noncompliance will be repeated immediately and the results submitted to Ecology within five (5) days of becoming aware of the violation. 3.A detailed written report describing the noncompliance will be submitted to Ecology within five (5) days, unless requested earlier by Ecology. Anytime turbidity sampling indicates turbidity is 250 NTUs or greater, or water transparency is 6 cm or less, the Ecology Regional office will be notified by phone within 24 hours of analysis as required by Special Condition S5.A of the CSWGP. •Northwest Region at (425) 649-7000 for Island, King, Kitsap, San Juan, Skagit, Snohomish, or Whatcom County Include the following information: 1.Your name and / Phone number 2.Permit number 3.City / County of project 4.Sample results 5.Date / Time of call 6.Date / Time of sample 7.Project name In accordance with Special Condition S4.D.5.b of the CSWGP, the Ecology Regional office will be notified if chemical treatment other than CO2 sparging is planned for adjustment of high pH water. Page | 26 Appendix/Glossary A. Site Map The site map must meet the requirements of Special Condition S9.E of the CSWGP B. BMP Detail Insert BMPs specification sheets here. Download BMPs from the Ecology Construction Stormwater website at: http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html Select Resources and Guidance to find the links to the Stormwater Manuals. C. Site Inspection Form Create your own or download Ecology’s template: http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html Select Permit, Forms and Application to find the link to the Construction Stormwater Site Inspection Form. Type text here Q (cfs) Acre Square Area (S.F.) 0.143 0.42 297.9166667 See MDF for 2 ‐year storm event using 15‐minutes time steps Assumed: site  will disturb 0.4 acres soil  Note See WSDOT Temporary Erosion and Sediment Control Manual M3109.02 Charter 5,From Page 5‐44 to Page 5‐46 ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.52 Program License Number: 200210003 Project Simulation Performed on: 05/05/2022 11:55 AM Report Generation Date: 05/05/2022 11:56 AM ————————————————————————————————— Input File Name: Sediment trap.fld Project Name: Aberdeen Analysis Title: Sediment Trap Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 32 Full Period of Record Available used for Routing Precipitation Station : 99003805 Seattle 38 in_5min 10/01/1939-10/01/2097 Evaporation Station : 991038 Seattle 38 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.420 0.420 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 0.420 0.420 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Grass 0.420 ---------------------------------------------- Subbasin Total 0.420 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Impervious 0.420 ---------------------------------------------- Subbasin Total 0.420 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: Sediment Trap Link Type: Structure Downstream Link: None Prismatic Pond Option Used Pond Floor Elevation (ft) : 100.00 Riser Crest Elevation (ft) : 103.00 Max Pond Elevation (ft) : 104.00 Storage Depth (ft) : 3.00 Pond Bottom Length (ft) : 100.0 Pond Bottom Width (ft) : 50.0 Pond Side Slopes (ft/ft) : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 Bottom Area (sq-ft) : 5000. Area at Riser Crest El (sq-ft) : 8,024. (acres) : 0.184 Volume at Riser Crest (cu-ft) : 19,374. (ac-ft) : 0.445 Area at Max Elevation (sq-ft) : 9176. (acres) : 0.211 Vol at Max Elevation (cu-ft) : 27,968. (ac-ft) : 0.642 Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 24.00 Common Length (ft) : 0.000 Riser Crest Elevation : 103.00 ft Hydraulic Structure Geometry Number of Devices: 1 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 100.00 Diameter (in) : 1.00 Orientation : Horizontal Elbow : Yes **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 1 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 48.925 _____________________________________ Total: 48.925 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 Link: Sediment Trap Not Computed _____________________________________ Total: 0.000 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.310 ac-ft/year, Post Developed: 0.000 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Subbasin: Subbasin 1 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 2.939E-02 2-Year 0.143 5-Year 6.576E-02 5-Year 0.208 10-Year 9.457E-02 10-Year 0.242 25-Year 0.114 25-Year 0.294 50-Year 0.130 50-Year 0.316 100-Year 0.144 100-Year 0.335 200-Year 0.172 200-Year 0.380 500-Year 0.210 500-Year 0.440 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): 2137.7% FAIL Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): 11884.6% FAIL Maximum Excursion from Q2 to Q50 (Must be less than 10%): 99999.0% FAIL Percent Excursion from Q2 to Q50 (Must be less than 50%): 100.0% FAIL ------------------------------------------------------------------------------------------------- FLOW DURATION DESIGN CRITERIA: FAIL ------------------------------------------------------------------------------------------------- **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): 21.8% FAIL Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): 2137.7% FAIL ------------------------------------------------------------------------------------------------- LID DURATION DESIGN CRITERIA: FAIL ------------------------------------------------------------------------------------------------- TESC Best Management Practices Chapter 5 Page 5-44 WSDOT Temporary Erosion and Sediment Control Manual M 3109.02 May 2019 Additional Information Managing a large construction project with multiple contractors is a major coordination challenge. Weekly meetings, progress reports and schedules, or other methods of consistent communication are vital. Developing and following a specified work schedule that coordinates the timing of land-disturbing activity with the installation of appropriate BMPs requires effective communication between environmental site inspectors, CESCLs, contractors, subcontractors, and the Project Engineer. Construction practices that limit or phase land-clearing activity and provide timely installation of erosion and sediment control BMPs can significantly reduce potential environmental impacts. Sediment control (treatment) BMPs must be installed to protect potential discharge points prior to land-disturbing activity in an area. Whenever feasible:  Minimize grading or excavation work during the rainy season.  Phase work to minimize the total area of exposed soil at any one time.  Install sedimentation ponds or detention facilities, stabilized construction, and sediment control BMPs prior to work in an area.  Practice staged seeding in order to revegetate areas as soon as possible. 5-1.1.30 Sediment Traps No Standard Specification Standard Plan I-80.10 – Miscellaneous Erosion Control Details SWMM Volume II equivalent: BMP C240 Sediment Trap Function Sediment traps are used to aid in the settling of suspended sediments from concentrated flows. Chapter 5 TESC Best Management Practices WSDOT Temporary Erosion and Sediment Control Manual M 3109.02 May 2019 Page 5-45 Additional Information  Intended for use on sites where the tributary drainage area is less than 3 acres, with no unusual drainage features and with a projected build- out time of 6 months or less. If the tributary drainage area is more than 3 acres, use a temporary sediment pond.  Trap efficiency is enhanced when runoff is passed through multiple sediment control BMPs.  Sediment traps are limited to removing silt/larger-sized sediment particles.  Trap effectiveness increases with trap size. Design, Installation and Maintenance 1.Sizing Procedure  To determine the sediment trap geometry, first calculate the design surface area (SA) of the trap, measured at the invert of the weir. Use the following equation: SA = FS(Q/Vs) where: Q = Design inflow based on criteria below. Vs = The settling velocity of the soil particle of interest. The 0.02 mm (medium silt) particle with an assumed density of 2.65 g/cm3 has been selected as the particle of interest and has a settling velocity (Vs) of 0.00096 ft/sec. FS = A safety factor of 2 to account for non-ideal settling. Therefore, the equation for computing surface area becomes: SA = 2 x Q/0.00096 or 2,080 square feet per cfs of inflow Note: Even if permanent facilities are used, they must still have a surface area that is at least as large as that derived from the above formula. If they do not, the pond must be enlarged. TESC Best Management Practices Chapter 5 Page 5-46 WSDOT Temporary Erosion and Sediment Control Manual M 3109.02 May 2019  Design Q for sizing: Eastern Washington should be designed to handle the 2-year peak flow rate from the appropriate long duration storm event using a single event model. See HRM Appendix 4C to determine the Climatic Region and appropriate long duration storm event for the project. The designer should consult with Region Hydraulics staff to determine whether a higher level of protection is needed beyond the 2-year peak flow due to the time of year for construction (freezing conditions and snowmelt), the downstream conditions, or the expectation that the project will last several construction seasons. Western Washington should be designed to handle peak flows generated by the 2-year storm event using 15-minute time steps predicted by MGSFlood for the developed site condition without flow control. The designer should consult Region Hydraulics staff to determine if downstream conditions warrant a higher level of protection. The 10-year peak flow using 15-minute time steps should be used if the project is expected to last several construction seasons.  Note that sediment traps may not be feasible on utility projects due to the limited work space or the short-term nature of the work. Use portable tanks in place of sediment traps for utility projects.  Remove sediment from the trap when it reaches 1 foot in depth.  Repair any damage to the pond embankments or slopes. 5-1.1.31 Sedimentation Bags No Standard Specification or Standard Plan No SWMM Volume II equivalent Function Sedimentation bags are considered pre-treatment BMPs because they work to remove coarse sediment from turbid water before it receives additional treatment. Additional Information Sedimentation or filtration dewatering bags are a pretreatment BMP, meaning the water that filters through the bag must receive additional treatment prior to discharging to surface waters. Base the selection of the bag product on pump flow rate, the amount and type of suspended sediment in the water, and permittivity of the bag. As the bag fills with sediment, take measures to prevent bag failure or bursting (e.g., reduce pump flow APPENDIX G Drainage Basin Surface areas Geotechnical Report NELSON GEOTECHNICAL ASSOCIATES, INC. February 26, 2021 Mr. Long Nguyen 11904 SE 228th Place Kent, Washington 98051 VIA Email:longdnguyen@gmail.com Geotechnical Engineering Evaluation Nguyen Aberdeen Avenue NE Short Plat Residential Development 2309 Aberdeen Avenue NE Renton, Washington NGA File No. 1227220 Dear Mr. Nguyen: We are pleased to submit the attached report titled “Geotechnical Engineering Evaluation – Nguyen Aberdeen Avenue NE Short Plat Residential Development – 2309 Aberdeen Avenue NE – Renton, Washington.”This report summarizes our observations of the existing surface and subsurface conditions within the site and provides general recommendations for the proposed site development. Our services were completed in general accordance with the proposal issued to you on January21, 2021. The property is currently vacant but was previously occupied with an existing single-family residence within the western portion of the property. The ground surface within the property is relatively level to gently sloping down from the west to the east. We understand that the proposed development will include construction of three new single-family residences and associated roadways and underground utilities. We explored the subsurface conditions within the site with eleven trackhoe excavated test pits explorations. The explorations extended to depths in the range of 5.5 to 11.5 feet below the existing ground surface. Our explorations indicated that the site was underlain by surficial undocumented fill soils with competent native glacial outwash soils at depth. It is our opinion that the proposed site development is feasible from a geotechnical engineering standpoint, provided that our recommendations for site development are incorporated into project plans. In general, the native glacial bearing soils underlying the site should adequately support the planned structures. Foundations should be advanced through any loose and/or undocumented fill soils down to the competent glacial bearing material interpreted to underlie the site, for bearing capacity and settlement considerations. These soils should generally be encountered between approximately 2.0 to 6.0 feet below the existing ground surface, based on our explorations. The deepest areas of undocumented fill were generally encountered within the lower very eastern portion of the property. If deeper areas of loose soils or undocumented fill are encountered in unexplored areas of the site, they should be removed and replaced with structural fill for foundation and pavement support. Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Summary – Page 2 NELSON GEOTECHNICAL ASSOCIATES, INC. Specific grading and stormwater plans have not been finalized at the time this report was prepared. However, we understand that stormwater from the proposed development may be directed into on-site infiltration systems, if feasible. The City of Renton uses the 2016 King County Surface Water Design Manual, as amended by the City of Renton Storm Water Manual to determine the design of infiltration facilities. According to this manual and the City of Renton requirements, on-site infiltration testing consisting of the small Pilot Infiltration Test (PIT) is used to determine the long-term design infiltration rates. Based on the results of our on-site infiltration testing and granular nature of the native glacial outwash soils encountered within the western and central portion of the site, it is our opinion that the onsite native outwash soils within the western and central portion of the property are conducive for traditional stormwater infiltration methods. However, it is our opinion that stormwater infiltration is not feasible within the very eastern portion of the property due to the overall depth of the undocumented fill and presence of perched groundwater encountered at depth within our eastern explorations. This is discussed in more detail in the attached report. In the attached report, we have also provided general recommendations for site grading, slabs-on- grade, structural fill placement, retaining walls, erosion control, and drainage. We should be retained to review and comment on final development plans and observe the earthwork phase of construction. We also recommend that NGA be retained to provide monitoring and consultation services during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during construction differ from those anticipated, and to evaluate whether or not earthwork and foundation installation activities comply with contract plans and specifications. It has been a pleasure to provide service to you on this project. Please contact us if you have any questions regarding this report or require further information. Sincerely, NELSON GEOTECHNICAL ASSOCIATES, INC. Khaled M. Shawish, PE Principal Engineer TABLE OF CONTENTS INTRODUCTION .......................................................................................................... 1 SCOPE.........................................................................................................................1 SITE CONDITIONS........................................................................................................2 Surface Conditions........................................................................................................2 Subsurface Conditions..................................................................................................2 Hydrogeologic Conditions............................................................................................. 3 SENSITIVE AREA EVALUATION ..................................................................................... 4 Seismic Hazard .............................................................................................................. 4 Erosion Hazard .............................................................................................................. 4 CONCLUSIONS AND RECOMMENDATIONS .................................................................. 5 General ......................................................................................................................... 5 Erosion Control ............................................................................................................. 6 Site Preparation and Grading ....................................................................................... 6 Temporary and Permanent Slopes ............................................................................... 7 Foundations .................................................................................................................. 8 Retaining Walls ............................................................................................................. 9 Structural Fill ............................................................................................................... 10 Slab-on-Grade ............................................................................................................. 11 Pavements .................................................................................................................. 11 Utilities ........................................................................................................................ 11 Site Drainage ............................................................................................................... 12 CONSTRUCTION MONITORING .................................................................................. 14 USE OF THIS REPORT ................................................................................................. 14 LIST OF FIGURES Figure 1 – Vicinity Map Figure 2 – Site Plan Figure 3 – Soil Classification Chart Figures 4 through 6 – Exploration Logs Geotechnical Engineering Evaluation Nguyen Aberdeen Avenue NE Short Plat Residential Development 2309 Aberdeen Avenue NE Renton, Washington INTRODUCTION This report presents the results of our geotechnical engineering investigation and evaluation of the planned residential development project in Renton, Washington. The project site is located at 2309 Aberdeen Avenue NE, as shown on the Vicinity Map in Figure 1. The purpose of this study is to explore and characterize the site’s surface and subsurface conditions and to provide geotechnical recommendations for the planned site development. The property is currently vacant but was previously occupied with an existing single-family residence within the western portion of the property. The ground surface within the property is relatively level to gently sloping down from the west to the east. We understand that the proposed development will include construction of three new single-family residences and associated roadways and underground utilities. Final development and grading plans have not been prepared at the time this report was issued. Final stormwater plans have also not been developed, however, we understand that stormwater may be directed to on-site infiltration systems, if feasible. The existing site layout is shown on the Site Plan in Figure 2. SCOPE The purpose of this study is to explore and characterize the site surface and subsurface conditions and provide general recommendations for site development. Specifically, our scope of services included the following: 1. Review available soil and geologic maps of the area. 2. Explore the subsurface soil and groundwater conditions within the site with trackhoe excavated test pits. Trackhoe was subcontracted by NGA. 3. Perform grain-size sieve analysis on soil samples, as necessary. 4. Provide recommendations for structure foundations. 5. Provide recommendations for earthwork. 6. Provide recommendations for temporary and permanent slopes. 7. Provide recommendations for retaining walls. Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 2 NELSON GEOTECHNICAL ASSOCIATES, INC. 8. Provide recommendations for slab and pavement subgrade preparation. 9. Provide recommendations for utility installation. 10. Provide long-term design infiltration rates based on on-site Pilot Infiltration Testing (PIT) per the 2016 King County Surface Water Design Manual. Location and depth of tests were determined by the civil engineer. Water for the tests was secured by client. 11. Provide recommendations for infiltration system installation. 12. Provide recommendations for site drainage and erosion control. 13. Document the results of our findings, conclusions, and recommendations in a written geotechnical report. SITE CONDITIONS Surface Condition The site consists of a roughly square-shaped parcel covering approximately 0.84 acres. The site is currently vacant but was previously occupied by a single-family residence within the western portion of the site. Topography within the western and central portion of the slopes gently down from the western property line to the eastern portion of the property. The eastern portion of the property is generally level. The site is generally vegetated by grass-covered yard areas, young to mature trees, and landscaping. A horseshoe- shaped gravel driveway is located within the eastern portion of the property. The property is bound to the north, south, and west by single-family residences, and to the east by Aberdeen Avenue NE. We did not observe surface water within the site during our site visit on February 5, 2021. Subsurface Conditions Geology: The geologic units for this site are shown on Preliminary Geologic Map of Seattle and Vicinity, Washington, by Waldron, H.H., Leisch, B.A., Mullineaux, D.R., and Crandell, D.R., (USGS, 1961). The site is mapped as younger gravel (Qyg) with younger sand (Qys) and alluvium (Qa) mapped nearby. The younger gravel and sand deposits are described as fine to coarse sand that contains varying amounts of gravel. The alluvium is described as silt with varying amounts of sand and organic material. Our explorations generally encountered fine to coarse sand with varying amounts of gravel and silt within the western and central portion of the property that we interpreted as younger gravel outwash soils. Our explorations within the very eastern portion of the property generally encountered silt with sand and silty fine to medium sand that we interpreted as native alluvium and younger sand deposits at depth. Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 3 NELSON GEOTECHNICAL ASSOCIATES, INC. Explorations: The subsurface conditions within the site were explored on February 5, 2021 by excavating eleven test pits with a mini-trackhoe extending to depths in the range of 5.5 to 11.5 feet below the existing ground surface. The approximate locations of our explorations are shown on the Site Plan in Figure 2. A geologist from NGA was present during the explorations, examined the soils and geologic conditions encountered, obtained samples of the different soil types, and maintained logs of the test pits. The soils were visually classified in general accordance with the Unified Soil Classification System, presented in Figure 3. The logs of our explorations are attached to this report and are presented as Figures 4 through 6. We present a brief summary of the subsurface conditions in the following paragraph. For a detailed description of the subsurface conditions, the logs of the explorations should be reviewed. At the surface of all of our explorations, we encountered approximately 0.5 to 6.0 feet of surficial grass and loose to medium dense dark brown silty fine to medium sand with varying amounts of gravel, organics and debris that we interpreted as surficial topsoil and/or undocumented fill soils. Underlying the surficial topsoil/undocumented fill soils within Test Pit 1, 2, 8, and 9 within the eastern portion of the site, we encountered medium dense/stiff orange-brown to gray-brown silty fine to medium sand and silt with fine sand with varying amounts of gravel and organics that we interpreted as younger sand and alluvium deposits, respectively. Below the surficial topsoil and/or the undocumented fill in Test Pits 3 through 7, 10, and Infiltration Pit 1, we encountered medium dense to dense fine to coarse sand with varying amounts of silt and gravel that we interpreted as native younger gravel soils. All of our test pits were terminated within the native younger gravel and sand soils at depths in the range of 5.5 to 11.5 feet below the existing ground surface. Hydrogeologic Conditions We encountered minor to moderate groundwater seepage within Test Pits 1 and 8 at a depth of 8.0 feet below the existing ground surface. We interpreted this groundwater seepage to be perched groundwater. Perched water occurs when surface water infiltrates through less dense, more permeable soils and accumulates on top of a relatively low permeability material. Perched water does not represent a regional groundwater "table" within the upper soil horizons. Perched water tends to vary spatially and is dependent upon the amount of rainfall. We would expect the amount of perched groundwater to decrease during drier times of the year and increase during wetter periods. Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 4 NELSON GEOTECHNICAL ASSOCIATES, INC. SENSITIVE AREA EVALUATION Seismic Hazard We reviewed the 2018 International Building Code (IBC) for seismic site classification for this project. Since competent glacial soils are inferred to underlie the site at depth, the site conditions best fit the IBC description for Site Class D. Table 1 below provides seismic design parameters for the site that are in conformance with the 2018 IBC, which specifies a design earthquake having a two percent probability of occurrence in 50 years (return interval of 2,475 years), and the 2008 USGS seismic hazard maps. Table 1 – 2018 IBC Seismic Design Parameters Site Class Spectral Acceleration at 0.2 sec. (g) Ss Spectral Acceleration at 1.0 sec. (g) S1 Site Coefficients Design Spectral Response Parameters Fa Fv SDS SD1 D 1.473 0.542 1.000 1.500 0.958 0.542 The spectral response accelerations were obtained from the USGS Earthquake Hazards Program Interpolated Probabilistic Ground Motion website (2008 data) for the project latitude and longitude. Hazards associated with seismic activity include liquefaction potential and amplification of ground motion. Liquefaction is caused by a rise in pore pressures in a loose, fine sand deposit beneath the groundwater table. It is our opinion that the medium dense or better glacial outwash deposits interpreted to underlie the site and nearby vicinity have a low potential for liquefaction or amplification of ground motion. Erosion Hazard The criteria used for determination of the erosion hazard for affected areas include soil type, slope gradient, vegetation cover, and groundwater conditions. The erosion sensitivity is related to vegetative cover and the specific surface soil types, which are related to the underlying geologic soil units. The Soil Survey of King County Area, Washington, by the Natural Resources Conservation Service (NRCS), was reviewed to determine the erosion hazard of the on-site soils. The surface soils for this site were mapped as Indianola loamy sand, 5 to 15 percent slopes. The erosion hazard for this material is listed as slight. This site is relatively level to gently sloping and there are no steep slopes on the property. It is our opinion that the erosion hazard for site soils should be low in areas where the site is not disturbed. Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 5 NELSON GEOTECHNICAL ASSOCIATES, INC. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion that the planned development within the site is generally feasible from a geotechnical standpoint. Our explorations indicated that the site is generally underlain by competent native glacial till soils at depth throughout the site. The native glacial bearing soils encountered at depth should provide adequate support for foundation, slab, and pavement loads. We recommend that the planned structure be designed utilizing conventional shallow foundations. Footings should extend through any loose soil or undocumented fill soils and be founded on the underlying medium dense or better native glacial till soils, or structural fill extending to these soils. The medium dense or better native glacial bearing soils should typically be encountered approximately 2.0 to 6.0 feet below the existing surface, based on our explorations. In general, the competent native glacial soils were shallower within the western portion of the site and were deepest within the very eastern portion of the site. We should note that localized areas of deeper unsuitable soils and/or undocumented fill could be encountered at this site. This condition would require additional excavations in foundation, slab, and pavement areas to remove the unsuitable soils. Based on the results of our on-site infiltration testing and soil explorations throughout the site, it is our opinion that the onsite native granular outwash soils encountered within the western and central portion of the site are conducive for full stormwater infiltration methods. However, due to the deeper undocumented fill soils and presence of perched groundwater within our very eastern explorations, it is our opinion that stormwater infiltration is not feasible within the very eastern portion of the property. This is further discussed in the Site Drainage section of this report. The surficial soils encountered on this site are considered moisture-sensitive and will disturb easily when wet. We recommend that construction take place during the drier summer months, if possible. If construction is to take place during wet weather, the soils may disturb, and additional expenses and delays may be expected due to the wet conditions. Additional expenses could include the need for placing a blanket of rock spalls to protect exposed subgrades and construction traffic areas. Some of the native on- site soils may be suitable for use as structural fill depending on the moisture content of the soil during construction. NGA should be retained to determine if the on-site soils can be used as structural fill material during construction. Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 6 NELSON GEOTECHNICAL ASSOCIATES, INC. Erosion Control The erosion hazard for the on-site soils is interpreted to be slight to moderate for exposed soils, but actual erosion potential will be dependent on how the site is graded and how water is allowed to concentrate. Best Management Practices (BMPs) should be used to control erosion. Areas disturbed during construction should be protected from erosion. Erosion control measures may include diverting surface water away from the stripped or disturbed areas. Silt fences and/or straw bales should be erected to prevent muddy water from leaving the site. Disturbed areas should be planted as soon as practical and the vegetation should be maintained until it is established. The erosion potential of areas not stripped of vegetation should be low. Site Preparation and Grading After erosion control measures are implemented, site preparation should consist of stripping the topsoil, undocumented fill and loose soils from foundation, slab, pavement areas, and other structural areas, to expose medium dense or better native bearing glacial soils. The stripped soil should be removed from the site or stockpiled for later use as a landscaping fill. Based on our observations, we anticipate stripping depths of 2.0 to 6.0 feet, depending on the specific locations. In general, the competent native glacial soils were shallower within the western portion of the property and deeper within the eastern portion of the property. However, additional stripping may be required if areas of deeper undocumented fill and/or loose soil are encountered in unexplored areas of the site. After site stripping, if the exposed subgrade is deemed loose, it should be compacted to a non-yielding condition and then proof-rolled with a heavy rubber-tired piece of equipment. Areas observed to pump or weave during the proof-roll test should be reworked to structural fill specifications or over-excavated and replaced with properly compacted structural fill or rock spalls. If loose soils are encountered in the pavement areas, the loose soils should be removed and replaced with rock spalls or granular structural fill. If significant surface water flow is encountered during construction, this flow should be diverted around areas to be developed, and the exposed subgrades should be maintained in a semi-dry condition. If wet conditions are encountered, alternative site stripping and grading techniques might be necessary. These could include using large excavators equipped with wide tracks and a smooth bucket to complete site grading and covering exposed subgrade with a layer of crushed rock for protection. If wet conditions are encountered or construction is attempted in wet weather, the subgrade should not be compacted as this could cause further subgrade disturbance. In wet conditions, it may be necessary to cover the exposed subgrade with a layer of crushed rock as soon as it is exposed to protect the moisture sensitive soils from Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 7 NELSON GEOTECHNICAL ASSOCIATES, INC. disturbance by machine or foot traffic during construction. The prepared subgrade should be protected from construction traffic and surface water should be diverted around areas of prepared subgrade. The site soils are considered to be moisture-sensitive and will disturb easily when wet. We recommend that construction take place during the drier summer months if possible. However, if construction takes place during the wet season, additional expenses and delays should be expected due to the wet conditions. Additional expenses could include the need for placing a blanket of rock spalls on exposed subgrades, construction traffic areas, and paved areas prior to placing structural fill. Wet weather grading will also require additional erosion control and site drainage measures. Some of the native on-site soils may be suitable for use as structural fill, depending on the moisture content of the soil at the time of construction. NGA should be retained to evaluate the suitability of all on-site and imported structural fill material during construction. Temporary and Permanent Slopes Temporary cut slope stability is a function of many factors, including the type and consistency of soils, depth of the cut, surcharge loads adjacent to the excavation, length of time a cut remains open, and the presence of surface or groundwater. It is exceedingly difficult under these variable conditions to estimate a stable, temporary, cut slope angle. Therefore, it should be the responsibility of the contractor to maintain safe slope configurations at all times as indicated in OSHA guidelines for cut slopes. The following information is provided solely for the benefit of the owner and other design consultants and should not be construed to imply that Nelson Geotechnical Associates, Inc. assumes responsibility for job site safety. Job site safety is the sole responsibility of the project contractor. For planning purposes, we recommend that temporary cuts in the upper undocumented fill/surficial soils be no steeper than 2 Horizontal to 1 Vertical (2H:1V). Temporary cuts in the competent native glacial outwash soils at depth should be no steeper than 1.5H:1V. If significant groundwater seepage or surface water flow were encountered, we would expect that flatter inclinations would be necessary. We recommend that cut slopes be protected from erosion. The slope protection measures may include covering cut slopes with plastic sheeting and diverting surface runoff away from the top of cut slopes. We do not recommend vertical slopes for cuts deeper than four feet, if worker access is necessary. We recommend that cut slope heights and inclinations conform to appropriate OSHA/WISHA regulations. Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 8 NELSON GEOTECHNICAL ASSOCIATES, INC. Permanent cut and fill slopes should be no steeper than 2H:1V. However, flatter inclinations may be required in areas where loose soils are encountered. Permanent slopes should be vegetated, and the vegetative cover maintained until established. Foundations Conventional shallow spread foundations should be placed on medium dense or better native glacial outwash soils or be supported on structural fill or rock spalls extending to those soils. Native medium dense or better glacial bearing soils should be encountered approximately 2.0 to 6.0 feet below the existing ground surface based on our explorations. We typically encountered deeper areas of surficial undocumented fill soils within our explorations within the eastern portion of the site, and shallower undocumented fill soils within the western portion of the site. Where undocumented fill or less dense soils are encountered at footing bearing elevation, the subgrade should be over-excavated to expose native bearing soil. The over-excavation may be filled with structural fill, or the footings may be extended down to the competent native soils. If footings are supported on structural fill, the fill zone should extend outside the edges of the footing a distance equal to half of the depth of the over-excavation below the bottom of the footing. In case of excessive undocumented fill thickness, deep foundation options may be required. NGA is available to work with the structural engineer to explore those options. Footings should extend at least 18 inches below the lowest adjacent finished ground surface for frost protection and bearing capacity considerations. Foundations should be designed in accordance with the 2018 IBC. Footing widths should be based on the anticipated loads and allowable soil bearing pressure. Water should not be allowed to accumulate in footing trenches. All loose or disturbed soil should be removed from the foundation excavation prior to placing concrete. For foundations constructed as outlined above, we recommend an allowable bearing pressure of not more than 2,000 pounds per square foot (psf) be used for the design of footings founded on the medium dense or better native soils or structural fill extending to the competent native bearing material. The foundation bearing soil should be evaluated by a representative of NGA. We should be consulted if higher bearing pressures are needed. Current IBC guidelines should be used when considering increased allowable bearing pressure for short-term transitory wind or seismic loads. Potential foundation settlement using the recommended allowable bearing pressure is estimated to be less than 1-inch total and ½-inch differential between adjacent footings or across a distance of about 20 feet, based on our experience with similar projects. Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 9 NELSON GEOTECHNICAL ASSOCIATES, INC. Lateral loads may be resisted by friction on the base of the footing and passive resistance against the subsurface portions of the foundation. A coefficient of friction of 0.35 may be used to calculate the base friction and should be applied to the vertical dead load only. Passive resistance may be calculated as a triangular equivalent fluid pressure distribution. An equivalent fluid density of 200 pounds per cubic foot (pcf) should be used for passive resistance design for a level ground surface adjacent to the footing. This level surface should extend a distance equal to at least three times the footing depth. These recommended values incorporate safety factors of 1.5 and 2.0 applied to the estimated ultimate values for frictional and passive resistance, respectively. To achieve this value of passive resistance, the foundations should be poured “neat” against the native medium dense soils or compacted fill should be used as backfill against the front of the footing. We recommend that the upper one foot of soil be neglected when calculating the passive resistance. Retaining Walls Specific grading plans for this project were not available at the time this report was prepared but retaining walls may be incorporated into project plans. In general, the lateral pressure acting on retaining walls is dependent on the nature and density of the soil behind the wall, the amount of lateral wall movement which can occur as backfill is placed, wall drainage conditions, and the inclination of the backfill. For walls that are free to yield at the top at least one thousandth of the height of the wall (active condition), soil pressures will be less than if movement is limited by such factors as wall stiffness or bracing (at-rest condition). We recommend that walls supporting horizontal backfill and not subjected to hydrostatic forces, be designed using a triangular earth pressure distribution equivalent to that exerted by a fluid with a density of 35 pcf for yielding (active condition) walls, and 55 pcf for non-yielding (at-rest condition) walls. A seismic design loading of 8H should also be included in the wall design, where “H” represents the total height of the wall. These recommended lateral earth pressures are for a drained granular backfill and are based on the assumption of a horizontal ground surface behind the wall for a distance of at least the height of the wall, and do not account for surcharge loads. Additional lateral earth pressures should be considered for surcharge loads acting adjacent to walls and within a distance equal to the height of the wall. This would include the effects of surcharges such as traffic loads, floor slab loads, slopes, or other surface loads. We could consult with the structural engineer regarding additional loads on retaining walls during final design, if needed. Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 10 NELSON GEOTECHNICAL ASSOCIATES, INC. The lateral pressures on walls may be resisted by friction between the foundation and subgrade soil, and by passive resistance acting on the below-grade portion of the foundation. Recommendations for frictional and passive resistance to lateral loads are presented in the Foundations subsection of this report. All wall backfill should be well compacted as outlined in the Structural Fill subsection of this report. Care should be taken to prevent the buildup of excess lateral soil pressures due to over-compaction of the wall backfill. This can be accomplished by placing wall backfill in 8-inch loose lifts and compacting the backfill with small, hand-operated compactors within a distance behind the wall equal to at least one-half the height of the wall. The thickness of the loose lifts should be reduced to accommodate the lower compactive energy of the hand-operated equipment. The recommended level of compaction should still be maintained. Permanent drainage systems should be installed for retaining walls. Recommendations for these systems are found in the Subsurface Drainage subsection of this report. We recommend that we be retained to evaluate the proposed wall drain backfill material and observe installation of the drainage systems. Structural Fill General: Fill placed beneath foundations, pavement, or other settlement-sensitive structures should be placed as structural fill. Structural fill, by definition, is placed in accordance with prescribed methods and standards, and is monitored by an experienced geotechnical professional or soils technician. Field monitoring procedures would include the performance of a representative number of in-place density tests to document the attainment of the desired degree of relative compaction. The area to receive the fill should be suitably prepared as described in the Site Preparation and Grading subsection prior to beginning fill placement. Materials: Structural fill should consist of a good quality, granular soil, free of organics and other deleterious material, and be well graded to a maximum size of about three inches. All-weather fill should contain no more than five-percent fines (soil finer than U.S. No. 200 sieve, based on that fraction passing the U.S. 3/4-inch sieve). Some of the more granular native on-site soils may be suitable for use as structural fill, but this will be highly dependent on the moisture content of these soils at the time of construction. We should be retained to evaluate all proposed structural fill material prior to placement. Fill Placement: Following subgrade preparation, placement of structural fill may proceed. All filling should be accomplished in uniform lifts up to eight inches thick. Each lift should be spread evenly and be thoroughly compacted prior to placement of subsequent lifts. All structural fill underlying building areas and pavement subgrade should be compacted to a minimum of 95 percent of its maximum dry density. Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 11 NELSON GEOTECHNICAL ASSOCIATES, INC. Maximum dry density, in this report, refers to that density as determined by the ASTM D-1557 Compaction Test procedure. The moisture content of the soils to be compacted should be within about two percent of optimum so that a readily compactable condition exists. It may be necessary to over-excavate and remove wet soils in cases where drying to a compactable condition is not feasible. All compaction should be accomplished by equipment of a type and size sufficient to attain the desired degree of compaction and should be tested. Slab-on-Grade Slabs-on-grade should be supported on subgrade soils prepared as described in the Site Preparation and Grading subsection of this report. We recommend that all floor slabs be underlain by at least six inches of free-draining gravel with less than three percent by weight of the material passing Sieve #200 for use as a capillary break. A suitable vapor barrier, such as heavy plastic sheeting (6-mil, minimum), should be placed over the capillary break material. An additional 2-inch-thick moist sand layer may be used to cover the vapor barrier. This sand layer may be used to protect the vapor barrier membrane and to aid in curing the concrete. Pavements Pavement subgrade preparation and structural filling where required, should be completed as recommended in the Site Preparation and Grading and Structural Fill subsections of this report. The pavement subgrade should be proof-rolled with a heavy, rubber-tired piece of equipment, to identify soft or yielding areas that require repair. The pavement section should be underlain by a stable subgrade. We should be retained to observe the proof-rolling and recommend repairs prior to placement of the asphalt or hard surfaces. Utilities We recommend that underground utilities be bedded with a minimum six inches of pea gravel prior to backfilling the trench with on-site or imported material. Trenches within settlement sensitive areas should be compacted to 95 percent of the modified proctor as described in the Structural Fill subsection of this report. Trench backfill should be compacted to a minimum of 95 percent of the modified proctor maximum dry density. Trenches located in non-structural areas and five feet below roadway subgrade should be compacted to a minimum 90 percent of the maximum dry density. The trench backfill compaction should be tested. Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 12 NELSON GEOTECHNICAL ASSOCIATES, INC. Site Drainage Infiltration: The subsurface soils within our explorations at depth generally consisted of granular glacial outwash soils to the depths explored within the western and central portion of the site and native alluvial soils within the very eastern portion of the property. In accordance with the 2016 King County Surface Water Design Manual (KCSWDM), we conducted one Small PIT within Infiltration Pit 1 within the central portion of the property as shown on the attached Site Plan in Figure 2. Infiltration Pit 1 measured 4.0-feet long by 3.0-feet wide by 8.0-feet deep. Due to the granular nature of the site soils and the maximum capacity of the on-site water source, we were only able to maintain approximately 2.0-inches of standing water within Infiltration Pit 1 instead of the recommended 12-inches. This level was maintained for approximately 6 hours for the pre soak period of the test. After the 6-hour soaking period was completed, the water level was maintained at approximately 2-inches for one hour for the steady-state period with the maximum flow rate of the on-site water source. At this time, the water flow rate into the hole was monitored with a Great Plains Industries (GPI) TM 050 water flow meter. The maximum flow rate of the on-site water source for Infiltration Pit 1 stabilized at 6.67 gallons per minute (400.2 gallons per hour), which equates to an approximate infiltration rate of 53.50 inches per hour. The water was shut off after the steady-state period of the test and was monitored for the falling head portion of the test. After 2 minutes, the water level within the pit had fully infiltrated resulting in an infiltration rate of 60.0 inches per hour. It is our opinion that the native granular outwash soils encountered at depth within the western and central portion of the property are suitable for traditional stormwater infiltration. The subsurface soils within the western and central portion of the property generally consisted of granular outwash sand soils at depth. We have selected the most conservative measured field rate of 53.5 in/hr obtained from the falling head portions of the test in our infiltration pit to be utilized in determining the long-term design infiltration rate for the infiltration systems within the western and central portions of the property. We referenced Equation 5-11 within Chapter 5.2.1 of the (KCSWDM) that applies correction factors to the field measured infiltration rate to generate a long-term design infiltration rate. Correction factors of 0.50, 0.90, and 0.80 were utilized in this equation for Ftesting, Fgeometry, Fplugging respectively, resulting in an infiltration rate of 19.25 inches per hour, to be utilized to design any on-site infiltration systems founded within the native granular outwash soils within the western and central portions of the property. We recommend that the base of the infiltration systems within the western and central portions of the property be terminated within the native granular outwash soils encountered at approximately 0.5 to 6.0 feet below the existing ground surface within the western and central portions of the property. We recommend that stormwater infiltration systems not be located within the eastern portion of the property due to the presence of surficial Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 13 NELSON GEOTECHNICAL ASSOCIATES, INC. undocumented fill and perched groundwater encountered at depth within our explorations within the very eastern portion of the property. NGA should be retained to observe infiltration trench excavations. The stormwater manual recommends a three-foot separation between the base of an infiltration system and any underlying bedrock, impermeable horizon, or groundwater. We did not encounter groundwater seepage within our test pit explorations within the western and central portion of the site to a depth of approximately 11.5 feet below the existing ground surface. We recommend that the base of any proposed infiltration systems be located to maintain minimum separation from any groundwater and impermeable horizons in accordance with the stormwater manual and the City of Renton requirements. We also recommend that any proposed infiltration systems be placed as to not negatively impact any proposed or existing nearby structures and also meet all required setbacks from existing property lines, structures, and sensitive areas as discussed in the drainage manual. Infiltration systems should not be located within proposed fill areas within the site associated with site grading or retaining wall backfill as such condition could lead to failures of the placed fills and/or retaining structures. We recommend that the base of the on-site infiltration systems be extended through the upper undocumented fill and surficial soils and terminated within the native glacial outwash soils encountered at depth throughout the site. We should be retained during construction to evaluate the soils exposed in the infiltration systems to verify that the soils are appropriate for infiltration. Surface Drainage: The finished ground surface should be graded such that stormwater is directed to an approved stormwater collection system. Water should not be allowed to stand in any areas where footings, slabs, or pavements are to be constructed. Final site grades should allow for drainage away from the residences. We suggest that the finished ground be sloped downward at a minimum gradient of three percent, for a distance of at least 10 feet away from the residences. Surface water should be collected by permanent catch basins and drain lines and be discharged into an approved discharge system. Subsurface Drainage: If groundwater is encountered during construction, we recommend that the contractor slope the bottom of the excavation and collect the water into ditches and small sump pits where the water can be pumped out and routed into a permanent storm drain. We recommend the use of footing drains around the structures. Footing drains should be installed at least one foot below planned finished floor elevation. The drains should consist of a minimum 4-inch-diameter, rigid, slotted or perforated, PVC pipe surrounded by free-draining material wrapped in a filter fabric. We recommend that the free-draining material consist of an 18-inch-wide zone of clean (less than three- percent fines), granular material placed along the back of walls. Pea gravel is an acceptable drain material. Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 14 NELSON GEOTECHNICAL ASSOCIATES, INC. The free-draining material should extend up the wall to one foot below the finished surface. The top foot of backfill should consist of impermeable soil placed over plastic sheeting or building paper to minimize surface water or fines migration into the footing drain. Footing drains should discharge into tightlines leading to an approved collection and discharge point with convenient cleanouts to prolong the useful life of the drains. Roof drains should not be connected to wall or footing drains. CONSTRUCTION MONITORING We should be retained to provide construction monitoring services during the earthwork phase of the project to evaluate subgrade conditions, temporary cut conditions, fill compaction, and drainage system installation. USE OF THIS REPORT NGA has prepared this report for Mr. Long Nguyen and his agents, for use in the planning and design of the development on this site only. The scope of our work does not include services related to construction safety precautions and our recommendations are not intended to direct the contractors’ methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. There are possible variations in subsurface conditions between the explorations and also with time. Our report, conclusions, and interpretations should not be construed as a warranty of subsurface conditions. A contingency for unanticipated conditions should be included in the budget and schedule. We recommend that NGA be retained to provide monitoring and consultation services during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed differ from those anticipated, and to evaluate whether or not earthwork and foundation installation activities comply with contract plans and specifications. We should be contacted a minimum of one week prior to construction activities and could attend pre-construction meetings if requested. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering practices in effect in this area at the time this report was prepared. No other warranty, expressed or implied, is made. Our observations, findings, and opinions are a means to identify and reduce the inherent risks to the owner. o-o-o Geotechnical Engineering Evaluation NGA File No. 1227220 Nguyen Aberdeen Avenue NE Short Plat Residential Development February 26, 2021 Renton, Washington Page 15 NELSON GEOTECHNICAL ASSOCIATES, INC. It has been a pleasure to provide service to you on this project. If you have any questions or require further information, please call. Sincerely, NELSON GEOTECHNICAL ASSOCIATES, INC. Lee S. Bellah, LG Project Geologist Khaled M. Shawish, PE Principal LSB:KMS:dy Six Figures Attached LOG OF EXPLORATION DEPTH (FEET) USC SOIL DESCRIPTION DJO:DPN NELSON GEOTECHNICAL ASSOCIATES, INC. FILE NO 1227220 FIGURE 4 INFILTRATION PIT ONE 0.0 – 3.5 GRASS UNDERLAIN BY LIGHT BROWN TO DARK BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL, COBBLES, IRON OXIDE WEATHERING, ORGANICS, AND ROOTS (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 3.5 – 5.5 ORANGE-BROWN TO BROWN, SILTY FINE TO MEDIUM SAND WITH ROOTS, IRON OXIDE WEATHERING, GRAVEL, COBBLES, AND TRACE ORGANICS (MEDIUM DENSE, MOIST) (FILL) 5.5 – 10.0 SP-SM GRAY-BROWN TO GRAY, FINE TO COARSE SAND WITH GRAVEL, COBBLES, SILT, ROOTS, AND IRON OXIDE WEATHERING (MEDIUM DENSE TO DENSE, MOIST) SAMPLES WERE NOT COLLECTED GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 10.0 FEET ON 2/5/21 TEST PIT ONE 0.0 – 3.0 GRASS UNDERLAIN BY BROWN TO LIGHT BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL, ROOTS, AND ORGANICS (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 3.0 – 5.0 DARK BROWN TO BLACK, SILTY FINE TO MEDIUM SAND WITH GRAVEL, TRACE ROOTS, AND ORGANICS (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 5.0 – 8.0 ML GRAY TO GRAY-BROWN, SILT WITH FINE SAND, ORGANIC PARTICULATE, IRON OXIDE STAINING (STIFF TO VERY STIFF, MOIST) 8.0 – 10.0 SP-SM GRAY TO GRAY-BROWN, FINE TO MEDIUM SAND WITH SILT (MEDIUM DENSE TO DENSE, MOIST TO WET) SAMPLES WERE COLLECTED AT 5.5 AND 8.5 FEET GROUNDWATER SEEPAGE WAS ENCOUNTERED AT 8.0 TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 10.0 FEET ON 2/5/21 TEST PIT TWO 0.0 – 3.0 GRASS UNDERLAIN BY BROWN, SILTY FINE TO MEDIUM SAND WITH ROOTS, ORGANICS, AND GRAVEL (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 3.0 – 5.0 DARK BROWN TO BLACK, SILTY FINE TO MEDIUM SAND WITH GRAVEL, ROOTS, ORGANICS, ASPHALT CHUNKS AND TRACE COBBLES (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 5.0 – 10.0 SM ORANGE-BROWN TO BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL (MEDIUM DENSE, MOIST) SAMPLES WERE NOT COLLECTED GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 10.0 FEET ON 2/5/21 LOG OF EXPLORATION DEPTH (FEET) USC SOIL DESCRIPTION DJO:DPN NELSON GEOTECHNICAL ASSOCIATES, INC. FILE NO 1227220 FIGURE 5 TEST PIT THREE 0.0 – 0.5 GRASS UNDERLAIN BY SILTY, FINE TO MEDIUM SAND WITH ROOTS, ORGANICS, AND GRAVEL (LOOST TO MEDIUM DENSE, MOIST) (FILL) 0.5 – 1.5 SM GRAY-BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL AND IRON OXIDE STAINING (MEDIUM DENSE, MOIST) 1.5 – 10.5 SP BROWN-GRAY FINE TO COARSE SAND WITH GRAVEL AND TRACE SILT (MEDIUM DENSE TO DENSE, MOIST) SAMPLES WERE COLLECTED AT 3.0, 6.0, AND 9.0 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED SLIGHT TEST PIT CAVING WAS ENCOUNTERED BETWEEN 4.0 AND 10.0 FEET TEST PIT WAS COMPLETED AT 10.5 FEET ON 2/5/21 TEST PIT FOUR 0.0 – 0.5 GRASS UNDERLAIN BY DARK BROWN SILTY FINE TO MEDIUM SAND WITH GRAVEL, ROOTS, AND ORGANICS (LOOST TO MEDIUM DENSE, MOIST) (FILL) 0.5 – 3.0 SM BROWN-GRAY, SILTY FINE TO MEDIUM SAND WITH GRAVEL (MEDIUM DENSE, MOIST) 3.0 – 10.0 SP BROWN-GRAY, FINE TO COARSE SAND WITH GRAVEL AND TRACE SILT (MEDIUM DENSE TO DENSE, MOIST) SAMPLES WERE COLLECTED AT 5.0 AND 9.0 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS ENCOUNTERED BETWEEN 5.0 AND 10.0 FEET TEST PIT WAS COMPLETED AT 10.0 FEET ON 2/5/21 TEST PIT FIVE 0.0 – 1.5 GRASS UNDERLAIN BY DARK BROWN TO ORANGE BROWN, SILTY FINE TO COARSE SAND WITH GRAVEL, TRACE COBBLES, AND IRON OXIDE WEATHERING (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 1.5 – 11.0 SP GRAY TO ORANGE-GRAY, FINE TO COARSE SAND WITH GRAVEL, ROOTS, IRON-OXIDE WEATHERING, COBBLES, AND TRACE SILT (MEDIUM DENSE TO DENSE, MOIST) SAMPLES WERE COLLECTED AT 5.0 AND 9.0 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED SLIGHT TEST PIT CAVING WAS ENCOUNTERED AT 1.5 FEET TEST PIT WAS COMPLETED AT 11.0 FEET ON 2/5/21 TEST PIT SIX 0.0 – 1.0 GRASS UNDERLAIN BY DARK BROWN TO ORANGE-BROWN, SILTY FINE TO COARSE SAND WITH GRAVEL, TRACE COBBLES, AND IRON OXIDE WEATHERING (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 1.0 – 3.0 GRAY TO GRAY-BROWN, SILTY FINE SAND WITH ROOTS, ORGANICS, AND GRAVEL (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 3.0 – 5.5 DARK BROWN TO BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL, TRACE ROOTS, ORGANICS, IRON OXIDE WEATHERING, AND TRACE COBBLES (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 5.5 – 11.5 SP GRAY TO ORANGE-GRAY, FINE TO COARSE SAND WITH GRAVEL, ROOTS, IRON OXIDE WEATHERING, COBBLES, AND TRACE SILT (MEDIUM DENSE TO DENSE, MOIST) SAMPLES WERE COLLECTED 2.0, 5.0, AND 10 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 11.5 FEET ON 2/5/21 LOG OF EXPLORATION DEPTH (FEET) USC SOIL DESCRIPTION DJO:DPN NELSON GEOTECHNICAL ASSOCIATES, INC. FILE NO 1227220 FIGURE 6 TEST PIT SEVEN 0.0 – 3.0 GRASS UNDERLAIN BY LIGHT BROWN TO BROWN, SILTY FINE TO MEDIUM SAND WITH ROOTS, ORGANICS, AND GRAVEL (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 3.0 – 6.0 ORANGE-BROWN TO BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL, TRACE COBBLES, IRON OXIDE WEATHERING, AND ROOTS (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 5.5 – 11.5 SP GRAY TO ORANGE-GRAY, FINE TO COARSE SAND WITH GRAVEL, ROOTS, IRON OXIDE WEATHERING, COBBLES, AND TRACE SILT (MEDIUM DENSE TO DENSE, MOIST) SAMPLES WERE COLLECTED 2.0, 5.0, AND 10 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 11.5 FEET ON 2/5/21 TEST PIT EIGHT 0.0 – 4.5 GRASS UNDERLAIN BY DARK BROWN TO GRAY-BROWN, SILTY FINE TO MEDIUM SAND WITH ROOTS, GRAVEL, ORGANICS, AND IRON OXIDE STAINING (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 4.5 – 7.0 SM BROWN TO GRAY-BROWN, SILTY FINE TO MEDIUM SAND WITH TRACE GRAVEL, IRON OXIDE WEATHERING AND TRACE ROOTS (MEDIUM DENSE TO DENSE, MOIST TO WET) 7.0 – 10.5 SM GRAY TO GRAY-BROWN, SILTY FINE TO MEDIUM SAND WITH TRACE IRON OXIDE STAINING (MEDIUM DENSE TO DENSE, MOIST) SAMPLES WERE COLLECTED 6.0 AND 10.0 FEET GROUNDWATER SEEPAGE WAS ENCOUNTERED AT 8.0 FEET TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 10.5 FEET ON 2/5/21 TEST PIT NINE 0.0 – 4.5 GRASS UNDERLAIN BY DARK BROWN TO GRAY-BROWN, SILTY FINE TO MEDIUM SAND WITH ROOTS, GRAVEL, ORGANICS, AND IRON OXIDE STAINING (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 4.5 – 8.0 SM ORANGE-BROWN TO BROWN, SILTY FINE TO MEDIUM SAND WITH TRACE GRAVEL, IRON OXIDE WEATHERING AND TRACE ROOTS (MEDIUM DENSE TO DENSE, MOIST TO WET) 8.0 – 10.5 SM GRAY TO GRAY-BROWN, SILTY FINE TO MEDIUM SAND WITH TRACE IRON OXIDE STAINING (MEDIUM DENSE TO DENSE, MOIST) SAMPLE WAS COLLECTED 10.0 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED SLIGHT TEST PIT CAVING WAS ENCOUNTERED AT 8.0 FEET TEST PIT WAS COMPLETED AT 10.5 FEET ON 2/5/21 TEST PIT TEN 0.0 – 3.0 GRASS UNDERLAIN BY ORANGE BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL, TRACE COBBLES, AND IRON OXIDE WEATHERING (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 3.0 – 5.5 SP GRAY TO ORANGE-GRAY, FINE TO COARSE SAND WITH GRAVEL, ROOTS, IRON OXIDE WEATHERING, COBBLES, AND TRACE SILT (MEDIUM DENSE TO DENSE, MOIST) SAMPLES WERE NOT COLLECTED GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 5.5 FEET ON 2/5/21