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HomeMy WebLinkAboutEX11_TIR PRELIMINARY TECHNICAL INFORMATION REPORT Vaughn Property 1400 Aberdeen Ave NE Renton, Washington Prepared for: MainVue WA, LLC 1110 112th Ave N.E., Suite 202 Bellevue, WA 98004 March 24, 2021 Our Job No. 21348 3/25/21 EXHIBIT 11 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx TABLE OF CONTENTS 1.0 PROJECT OVERVIEW Figure 1.0.1 – Technical Information Report (TIR) Worksheet Figure 1.0.2 – Vicinity Map Figure 1.0.3 – Predeveloped Drainage Basin Map Figure 1.0.4 – Soil Survey Map Figure 1.0.5 – Assessor's Map Figure 1.0.6 – FEMA Map Figure 1.0.7 – Sensitive Area Map Figure 1.0.8 – Developed Drainage Basin Map Figure 1.0.9 – Downstream Basin Map 2.0 CONDITIONS AND REQUIREMENTS SUMMARY 2.1 Analysis of the Core Requirements and Special Requirements 3.0 OFF-SITE ANALYSIS 4.0 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN 4.1 Existing Site Hydrology 4.2 Developed Site Hydrology 4.3 Performance Standards 4.4 Flow Control System Figure 4.4.1 – Permeable Pavement Calculations 4.5 Water Quality System 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN 6.0 SPECIAL REPORTS AND STUDIES 6.1 Geotechnical Engineering Study prepared by Earth Solutions NW, LLC. dated March 16, 2021 7.0 OTHER PERMITS 8.0 ESC ANALYSIS AND DESIGN 9.0 BOND QUANTITIES AND FACILITY SUMMARIES 10.0 OPERATIONS AND MAINTENANCE MANUAL DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Tab 1.0 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 1.0 PROJECT OVERVIEW This section contains the following information: Figure 1.0.1 – Technical Information Report (TIR) Worksheet Figure 1.0.2 – Vicinity Map Figure 1.0.3 – Predeveloped Drainage Basin Map Figure 1.0.4 – Soil Survey Map Figure 1.0.5 – Assessor's Map Figure 1.0.6 – FEMA Map Figure 1.0.7 – Sensitive Area Map Figure 1.0.8 – Developed Drainage Basin Map Figure 1.0.9 – Downstream Basin Map DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 1.0 PROJECT OVERVIEW The Vaughn Property project is a single-family residential project consisting of the redevelopment of an existing parcel in the City of Renton. The project includes approximately 1.7 acres of parcel area located on 1400 Aberdeen Ave NE. The proposed development will construct 8 single-family lots with associated roads, tracts, utilities, and stormwater facilities. Four existing buildings will be demolished to make room for the development. The project site is located within a portion of Section 5, Township 23 North, Range 5 East, Willamette Meridian, in the City of Renton, Washington. The property contains four existing buildings, two of which receive access from Aberdeen Ave NE through gravel and concrete driveways. On-site vegetation consists of maintained lawn and several trees scattered throughout the site. There are no natural drainage courses of any kind on the property. Elevations range from 306 to 290 feet across the site with slopes ranging from approximately 2 to 12%. The USDA Web Soil Survey for this area shown in Figure 1.0.4 of this section indicates that the on- site soils are considered Indianola loamy sand with 5 to 15 percent slopes. The Geotechnical Engineering Study prepared by Earth Solutions NW, LLC identified the underlying native soil as sand with fines in the initial 5 feet of soil depth and cleaner sand for depths below 5 feet. These soils are considered feasible for infiltration facilities per the Geotechnical Engineering Study included in Section 6.1 of this report. On-site construction will include a public roadway with curb and gutter, sidewalk and a planter strip. Additionally, stormwater catch basins, storm pipes, water mains and sewer utilities will be constructed on-site. Frontage improvements along Aberdeen Ave NE will consist of roadway widening with vertical curb and sidewalk, planter strip, storm pipes and catch basins. Stormwater runoff generated by the on-site road, sidewalks and lot driveways will be infiltrated through permeable pavement located within the on-site roadway section. Water quality will be provided by a 6-inch sand layer located below the permeable pavement section. Runoff from impervious areas within each lot will be routed to drywells designed to infiltrate the runoff into the native soil. Runoff from the frontage improvements along Aberdeen Ave NE will be collected and routed south by a tightlined conveyance system. The storm drainage design is based on the 2017 City of Renton Surface Water Design Manual which is an amended version of the 2016 King County Surface Water Design Manual (KCSWDM). Please refer to Section 4.0 of this TIR for further details regarding the drainage facility design. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 3/24/2021 03/24/21 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Horizontal: Scale: Vertical: For: Title: V I C I N I T Y M A P Job Number N.T.S.N/A 21348 D AT E: 03/19/21 Vaughn Short Plat Renton, Washington P:\21000s\21348\exhibit\graphics\21348 vmap.cdr RE FER ENC E: MapQuest (2021) SITE Figure 1.0.2 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 For:Title: 21348 1 MAINVUE WA, LLC 1110 112TH AVE NE, SUITE 202 BELLEVUE, WA 98004 CONTACT: LISA CAVELL CITY OF RENTON, KING COUNTY, WASHINGTONVAUGHN PROPERTYA PORTION OF SECTION 05, TOWNSHIP 23 N., RANGE 05 E., W.M.OFVAUGH PROPERTY PREDEVELOPED BASIN MAPPREDEVELOPED BASIN MAP FOR 1 ABERDEEN AVE NE NE 15TH STPREDEVELOPED ON-SITE BASINSCALE: 1"=20'PREDEVELOPEDFRONTAGE BASINFigure 1.0.3DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Horizontal: Scale: Vertical: For: Title: S O I L S U RV E Y M A P Job Number N.T.S.N/A 21348 D AT E: 03/19/21 Vaughn Short Plat Renton, Washington P:\21000s\21348\exhibit\graphics\21348 soil.cdr HSG A RE FER ENCE: US DA, Natural Resources Conservation Service LE GEN D: InC = Indianola loamy sand, 5-15% slopes SITE Figure 1.0.4 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Horizontal: Scale: Vertical: For: Title: A S S E S S O R M A P Job Number N.T.S.N/A 21348 D AT E: 03/19/21 Vaughn Short Plat Renton, Washington P:\21000s\21348\exhibit\graphics\21348 amap.cdr SITE RE FER ENC E: King County Department of Assessments (Jan. 2020) Figure 1.0.5 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Horizontal: Scale: Vertical: For: Title: F E M A M A P Job Number N.T.S.N/A 21348 D AT E: 03/19/21 Vaughn Short Plat Renton, Washington P:\21000s\21348\exhibit\graphics\21348 fema.cdr REFER EN CE: Federal Emergency Management Agency (Portion of Map 53033C0664G, Aug. 2020) Areas determined to be outside the 0.2% annual chance floodplain. ZONE X OTHER AREAS L E G E N D SITE Figure 1.0.6 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Horizontal: Scale: Vertical: For: Title: S E N S I T I V E A R E A S M A P Job Number N.T.S.N/A 21348 D AT E: 03/19/21 Vaughn Short Plat Renton, Washington P:\21000s\21348\exhibit\graphics\21348 sens.cdr SITE RE FER ENC E: COR Maps (rentonwa.gov 2021) Figure 1.0.7 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 For:Title: 21348 1 MAINVUE WA, LLC 1110 112TH AVE NE, SUITE 202 BELLEVUE, WA 98004 CONTACT: LISA CAVELL CITY OF RENTON, KING COUNTY, WASHINGTONVAUGHN PROPERTYA PORTION OF SECTION 05, TOWNSHIP 23 N., RANGE 05 E., W.M.OFVAUGH PROPERTY DEVELOPED BASIN MAPDEVELOPED BASIN MAP FOR 1 ABERDEEN AVE NE NE 15TH STDEVELOPED ON-SITE BASINSCALE: 1"=20'ROAD A12348765TRACT ATRACT BTRACT CTRACT DTRACT EDEVELOPEDON-SITE BASINDEVELOPEDFRONTAGEBASINDEVELOPEDFRONTAGEBASINDEVELOPED FRONTAGE BASINLEGEND:Figure 1.0.8DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 For:Title: 21348 1 MAINVUE WA, LLC 1110 112TH AVE NE, SUITE 202 BELLEVUE, WA 98004 CONTACT: LISA CAVELL CITY OF RENTON, KING COUNTY, WASHINGTONVAUGHN PROPERTYA PORTION OF SECTION 05, TOWNSHIP 23 N., RANGE 05 E., W.M.OFVAUGH PROPERTY DOWNSTREAM BASIN MAPDOWNSTREAM BASIN MAP FOR 1 ABERDEEN AVE NE NE 15TH STSCALE: 1"=100'FLOWPATH LEGENDSPECIAL NOTES1/4 MILE DOWNSTREAMFROM SITENE 12TH STABERDEEN AVE NE MONTEREY AVE NENE 14TH STNE SUNSET BLVDPROJECTSITEBLAINE AVE NE NE 13TH STFRONTAGEDRAINAGE BASINFRONTAGEDRAINAGE BASINFigure 1.0.9DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Tab 2.0 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 2.0 CONDITIONS AND REQUIREMENTS SUMMARY This section contains the following information: 2.1 Analysis of the Core Requirements and Special Requirements DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 2.1 Analysis of the Core Requirements and Special Requirements CORE REQUIREMENTS HOW PROJECT HAS ADDRESSED REQUIREMENT No. 1: Discharge at Natural Location The proposed development will maintain the natural discharge location of the drainage basin since runoff up to the 100-year storm will be infiltrated on-site through permeable pavement and drywells. Runoff from the existing road along the site frontage is conveyed south through a thickened edge curb and eventually flows into an existing catch basin near the southwest corner of the site. Runoff from the frontage improvements along Aberdeen Ave NE will be collected and routed south through a tightlined conveyance system that will eventually connect to the existing catch basin in this area. Because of this, the natural discharge location of this drainage basin will be maintained. Please see the Predeveloped and Developed Drainage Basin Maps in this section and the Developed Site Hydrology in Section 4.0 for further detail. No. 2: Off-Site Analysis The off-site analysis has been included within Section 3.0 of this Technical Information Report. No. 3: Flow Control This site is subject to the Peak Rate Flow Control Standard. Runoff from all on-site target surfaces in the developed site will be infiltrated through permeable pavement and drywells up to the 100-year storm event. No. 4: Conveyance System Any excess on-site runoff above the 100-year storm event will be collected by two catch basins located at the low point of the road. This runoff will be routed to the tightlined conveyance system located along the frontage improvements of Aberdeen Ave NE. The frontage and on-site conveyance systems will be designed per the 2017 City of Renton Surface Water Design Manual, and will be included in Section 5.0 of the Technical Information Report at final engineering. No. 5: Erosion and Sediment Control Temporary erosion control measures for this project will include: stabilized construction entrances, perimeter runoff control, cover practices, sedimentation facilities, and construction sequencing. No. 6: Maintenance and Operations An Operations and Maintenance Manual, if required, will be provided at final engineering. No. 7: Bonds and Liability Bonding will be completed as required by the City of Renton at final engineering. No. 8: Water Quality Water quality is achieved for on-site runoff by providing a 6” sand layer beneath the permeable pavement road section No. 9; Flow Control BMPs Full Dispersion and Basic Dispersion cannot be applied for this project as a native vegetated flowpath cannot be provided due to site constraints. The BMP requirements are met through the use of permeable pavement in the on-site road section and drywells to infiltrate rooftop runoff. In addition, all pervious surfaces will incorporate the soil amendment as detailed in the 2016 KCSWDM. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx SPECIAL REQUIREMENTS HOW PROJECT HAS ADDRESSED REQUIREMENT No. 1: Other Adopted Area Specific Requirements This special requirement does not apply to this project. No. 2: Floodplain/Floodway Delineation The proposed development is not located within the 100-year floodplain. No. 3: Flood Protection Facilities This project does not rely on an existing flood protection facility nor propose to modify or construct a new flood protection facility, therefore this special requirement does not apply. No. 4: Source Controls This project is a single-family residential project and is not subject to this special requirement. No. 5: Oil Control This site is not classified as a high-use site given the criteria found in the 2017 City of Renton Surface Water Design Manual, therefore no special oil control treatment is necessary. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Tab 3.0 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 3.0 OFF-SITE ANALYSIS This section contains the following information: Task 1 – Study Area Definitions and Maps Task 2 – Resource Review Task 3 – Field Inspection 3.1 Conveyance System Nuisance Problems (Type 1) 3.2 Severe Erosion Problems (Type 2) 3.3 Severe Flooding Problems (Type 3) 3.4 Downstream Water Quality Problems Task 4 – Drainage System Description and Problem Descriptions DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx TASK 1 – STUDY AREA DEFINITION AND MAPS The Vaughn Property project consists of the development of 8 single-family lots in a 1.7 acre site. The site is located at 1400 Aberdeen Ave NE, Renton, WA 98056 in a portion of Section 5, Township 23 North, Range 5 East, Willamette Meridian, in the City of Renton, Washington. The site is surrounded by existing single-family residences to the north, south, and east. Due to these existing developments having existing conveyance systems, there is no upstream runoff expected to flow into the site. This site is also bordered by Aberdeen Ave NE to the west, which conveys runoff south through an existing conveyance system. Topography on-site slopes in a southeast manner with slopes ranging from 2 to 12%. Elevations range from 306 to 290 feet across the site. The project proposes to collect and infiltrate all on-site runoff up to the 100-year storm event through permeable pavement and drywells. Any excess on-site runoff above the 100-year storm event will be routed westward and connect to the existing conveyance system on Aberdeen Ave NE. Runoff tributary to the frontage improvements along Aberdeen Ave NE will be routed southward along the frontage of the site and will eventually connect to the existing conveyance system near the southwest corner of the site. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx TASK 2 – RESOURCE REVIEW  Adopted Basin Plans: The site is tributary to the East Lake Washington – Renton Drainage Basin. There are no known basin plans which impact the proposed project.  Finalized Drainage Studies: There are no finalized drainage studies found within one mile of the downstream of the project site.  Basin Reconnaissance Summary Report: This is not applicable.  Floodplain and Floodway FEMA Maps: The project site is not located in a floodplain area, therefore this is not applicable.  Other Off-Site Analysis Reports: A site investigation was conducted as a Level 1 Off-Site Drainage Analysis.  Critical and Sensitive Area maps: Based on a review of King County iMap, there are no Critical or Sensitive Areas in the vicinity of the project site.  Sensitive Area maps from City of Renton were also reviewed. According to the City of Renton COR map, the site is located in a Zone 2 Aquifer Protection Area.  United States Department of Agriculture Web Soil Survey: Based on the Soils Map for this area (see Figure 1.0.4 – Soil Survey Map in Section 1.0), the site is located on Indianola loamy sand. This soils type is confirmed by the Geotechnical Engineering Study prepared for the project.  Wetland Inventory Map: Neither the King County iMap or the City of Renton COR map show wetlands in the vicinity of the project site.  Drainage Complaints along the downstream path from the site were reviewed on King County iMap. The only complaint found within 1 mile downstream of the site pertains to flooding near the garage of an existing home. This complaint is very old as it was filed in 1988 and no additional complaints were filed in the area. In addition, no flooding issues were observed in the area during the downstream analysis. Because of this, the proposed development will not impact the downstream system. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx TASK 3 – FIELD INSPECTION Level 1 Off-Site Drainage Analysis: As detailed in Section 4.1, on-site runoff in the existing condition infiltrates fully due to the underlying soil characteristics. This means that there is very little runoff that leaves the site even during large storm events. Runoff along the east side of Aberdeen Ave NE, which runs along the west boundary of the site, flows in a southward manner through a thickened edge curb and tightlined conveyance system. In the developed condition, stormwater runoff from the required frontage improvements along Aberdeen Ave NE will be collected by a tightlined conveyance system and routed to an existing catch basin on Aberdeen Ave NE near the southwest corner of the site. A field reconnaissance for the Level 1 Off-Site Drainage Analysis was conducted on March 23, 2021 for the runoff flowing south along Aberdeen Ave NE. On the day of the site visit, conditions were sunny and dry. A series of photos taken during the site visit with a detailed description of the downstream flowpath are shown below: The photo above shows the existing catch basin on Aberdeen Ave NE located near the southwest corner of the site. Runoff tributary to the site frontage improvements will be collected by a tightlined conveyance system and routed into the catch basin shown above. Once reaching this catch basin, runoff crosses the street and flows into a catch basin on the west side of Aberdeen Ave NE. From there, runoff begins to flow south. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx The above photos show several catch basins located on the west side of Aberdeen Ave NE. These catch basins continue to convey runoff to the south. The above right picture shows the catch basin at the intersection of Aberdeen Ave NE and NE 12th St. After crossing NE 12th St, runoff continues to flow south before reaching the catch basin shown on the left photo above. This catch basin is located on the east side of Aberdeen Ave NE and approximately 175 feet north of the bridge crossing above NE Sunset Blvd. Once runoff reaches this catch basin, it flows south in a steep manner before entering the conveyance system along NE Sunset Blvd. From there, runoff begins to flow west for approximately 30 feet before reaching one- DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx quarter mile downstream. The right picture above shows the storm drain located on the east side of NE Sunset Blvd looking west. See the Downstream Drainage Map in Section 1.0 for further details on this analysis. 3.1 Conveyance System Nuisance Problems (Type 1) Conveyance system nuisance problems are minor but not chronic flooding or erosion problems that result from the overflow of a constructed conveyance system that is substandard or has become too small as a result of upstream development. Such problems warrant additional attention because of their chronic nature and because they result from the failure of a conveyance system to provide a minimum acceptable level of protection. There were no conveyance system nuisance problems observed during the March 23, 2021 site visit. 3.2 Severe Erosion Problems (Type 2) Severe erosion problems can be caused by conveyance system overflows or the concentration of runoff into erosion-sensitive open drainage features. Severe erosion problems warrant additional attention because they pose a significant threat either to health and safety, or to public or private property. Runoff within one-quarter mile downstream of the project site is not discharged into any erosion-sensitive open drainage features. In addition, there were no conveyance system overflows observed during the March 23, 2021 site visit. Because of this, no future erosion problems should occur downstream. 3.3 Severe Flooding Problems (Type 3) Severe flooding problems can be caused by conveyance system overflows or the elevated water surfaces of ponds, lakes, wetlands, or closed depressions. Severe flooding problems are defined as follows:  Flooding of the finished area of a habitable building for runoff events less than or equal to the 100-year event. Examples include flooding of finished floors of homes and commercial or industrial buildings. Flooding in electrical/heating systems and components in the crawlspace or garage of a home. Such problems are referred to as "severe building flooding problems."  Flooding over all lanes of a roadway or severely impacting a sole access driveway for runoff events less than or equal to the 100-year event. Such problems are referred to as "severe roadway flooding problems." Based on a review of the FEMA Map (Section 1.0) the proposed site is not located in any floodplain areas therefore no severe flooding problems are expected. 3.4 Downstream Water Quality Problems After reviewing the Washington State Department of Ecology Water Quality Atlas, there are no Category 5, 4 or 2 Waterbodies located within one-quarter mile downstream of the project site therefore no water quality problems are expected from this development. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx TASK 4 – DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS UPSTREAM DRAINAGE ANALYSIS There is no upstream basin runoff contributing to the site. Along the north, east and south sides of the site, stormwater originating from the existing subdivisions is contained by an existing conveyance system in each case. There are no pipes or water features flowing into the site. The si te is located to the east of Aberdeen Ave NE, which conveys road runoff to the south through a thickened edge curb and tightlined conveyance system. Because of this, no runoff from Aberdeen Ave NE enters the project site. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Tab 4.0 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 4.0 FLOW CONTROL AND WAT ER QUALITY FACILITY AN ALYSIS AND DESIGN This section contains the following information: 4.1 Existing Site Hydrology 4.2 Developed Site Hydrology 4.3 Performance Standards 4.4 Flow Control System 4.5 Water Quality System DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 4.1 Existing Site Hydrology The existing conditions of the project site consist of four existing buildings surrounded by large open space of maintained lawn with scattered trees around the site. The site topography slopes in a southeast manner with slopes ranging from 2 to 12%. The Geotechnical Engineering Study prepared by Earth Solutions NW, LLC identified the on-site soils as sand with fines in the initial 5 feet of soil depth and cleaner sand for depths below 5 feet. This matches the on-site soil classification shown in the USDA W eb Soil Survey (Figure 1.0.4) which identifies the on-site soils as Indianola loamy sand with slopes ranging from 5 to 15%. As detailed in the Geotechnical Engineering Study, a Pilot Infiltration Test was conducted on the on-site soils. This test measured the on-site infiltration rate to be 44 inches per hour. Because of this, it is reasonable to assume that the majority of the on-site stormwater runoff is infiltrated and little to no runoff leaves the site. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 4.2 Developed Site Hydrology When completed, the Vaughn Property project will create 8 new single-family residences. The project development will consist of an access road, sidewalks, driveways, landscaped pervious areas and utilities. As shown in the Developed Drainage Basin Map, the Developed Basin for this project was divided into two areas: On-Site Drainage Basin and Frontage Drainage Basin. On-Site Drainage Basin The On-Site Drainage Basin consists of all on-site impervious and pervious areas including the access road, sidewalks, driveways, lot areas and landscape areas. Due to the high infiltration capacity of the underlying soil, all impervious on-site runoff will be infiltrated through the use of permeable pavement and drywells. As shown in the tables below, the on-site drainage basin was further divided to separate the areas tributary to the permeable pavement and the drywells. For further detail please refer to the Developed Basin Map in Section 1.0. On-Site Drainage Basin Sub Basin Impervious Concrete Impervious Pavement Impervious Driveways Impervious Roof Pervious Pavement Pervious Landscape Total Area Right-of- Way 0.12 Ac(1) 0.01 Ac 0.14 Ac 0.06 Ac 0.33 Ac Lots 0.07 Ac(3) 0.65 Ac(2) 0.58 Ac 1.30 Ac Notes: 1. Sidewalks, Curb and Gutter and Driveway Cuts 2. 55% of total lot area 3. Routed to the permeable pavement road section As shown above, the on-site drainage basin was further divided into the right-of-way and lot sub- basins. This was done so the permeable pavement within the on-site road received runoff from the Right-Of-Way Sub-Basin and the drywells within each lot received runoff from the Lots Sub-Basin. Please refer to Section 4.4 for further detail on the sizing of the permeable pavement and drywell BMP’s. Frontage Drainage Basin The Frontage Drainage Basin consists of all runoff attributed to the frontage improvements required for this project. The areas included in this drainage basin include roads, sidewalks and landscape areas. Please note that the pavement within the frontage road section is standard pavement and not permeable pavement. A detailed breakdown of the frontage basin areas is shown below: Frontage Drainage Basin Impervious Concrete Impervious Pavement Pervious Landscape Total Area 0.04 Ac(1) 0.05 Ac 0.05 Ac 0.14 Ac Notes: 1. Sidewalks and Curb and Gutter DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx Runoff from the Frontage Drainage Basin is exempt from the flow control and water quality standards required for this project. The criteria for this exemption is found in the 2017 City of Renton Surface Water Design Manual and is outlined below. 1. Less than 5,000 square feet of new plus replaced pollution generating impervious surfaces will be created. 2. Less than 3/4 acre of new pollution generating pervious surface will be added. As shown in the area breakdown table above, the frontage drainage basin consists of 3,920 SF of pollution generating impervious surface and 2,180 SF of pollution generating pervious surface, therefore this basin is exempt of the flow control and water quality requirements. Runoff from the frontage improvements will continue to be routed south and will eventually connect to the existing conveyance system on Aberdeen Ave NE. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 4.3 Performance Standards According to the Flow Control Applications Map for the City of Renton, this project shall conform to the Peak Flow Rate Flow Control Standard. As mentioned earlier, all on-site runoff is being infiltrated due to the high infiltration capacity of the underlying soil. All on-site impervious runoff is being infiltrated through the use of the permeable pavement and drywell BMP’s. In addition, all pervious surfaces will incorporate the soil amendment as detailed in the 2016 KCSWDM. Please refer to Section 4.4 of this report for further detail on the sizing of the permeable pavement and drywell BMP’s. This project is also subject to the Basic Water Quality standard. This is being achieved by providing a 6-inch sand layer below the permeable pavement road section. Please refer to Secti on 4.5 for further detail. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Preliminary Drainage Report.doc.docx 4.4 Flow Control System The Peak Flow Rate Flow Control Standard requirements based on the 2017 City of Renton Surface Water Design Manual states that developed peak discharge rates must match existing site conditions peak discharge rates for the 2-, 10- and 100-year return periods. This standard is being achieved for all on-site runoff in the developed condition through the permeable pavement and drywell BMP’s. Permeable Pavement BMP The tributary areas to this BMP are outlined in the Right-of-Way Sub-Basin within the On-Site Drainage Basin table. In addition, the expected impervious areas from the driveways to be constructed in each lot will be “run-on” to the permeable pavement roadway section and were therefore included in the sizing calculations. The infiltration rate used for the permeable pavement sizing calculations was calculated through a Pilot Infiltration Test conducted by Earth Solutions NW, LLC which can be found in the Geotechnical Engineering Study within Section 6.1 of this report. The measured infiltration rate resulting from this test was 44 inches per hour. After applying the required correction factors, the design infiltration rate used for the permeable pavement design was 14.8 inches per hour. In addition, the Geotechnical Engineering Study outlines the minimum permeable pavement thicknesses to meet the H-20 loading specifications. The minimum requirements for the permeable pavement road section are as follows: · 3 inches of permeable warm-mix asphalt underlain by 4 inches of asphalt-treated base · 12 inches of permeable base course with a void content of 30 to 40 percent The minimum thicknesses outlined above and the design infiltration rate of 14.3 inches per hour were input into the permeable pavement element contained in the 2012 WWHM program. The dimensions of the on-site permeable pavement road section which were also input into the 2012 WWHM program are 24 feet wide by 248 feet long. After routing the applicable tributary areas to the pavement, it was found that runoff is fully infiltrated up to the 100-year storm event. Please refer to Figure 4.4.1 for further detail on the WWHM permeable pavement calculations. Drywells BMP The tributary areas to this BMP are outlined in the Lots Sub-Basin within the On-Site Drainage Basin table. Please note that the driveway areas to be constructed within the lots will be routed to the permeable pavement BMP. In addition, the pervious areas contained in the lots are assumed to naturally infiltrate due to the high infiltration rate of the underlying soil. As outlined in the Geotechnical Engineering Study found in Section 6.1, the dominant soil grain size within the underlying on-site soil should be considered “medium sand.” According to the 2017 City of Renton Surface Water Design Manual, drywells must contain at least 90 cubic feet of gravel per 1,000 square feet of impervious surface served for drywells located in medium sand soils. Because each lot will have its own drywell, the maximum proposed lot impervious area of 7,150 SF was used for the sizing of all lot drywells. The required gravel volume for this impervious area is 354 cubic feet. The proposed drywells for each lot will have dimensions of 5-foot wide by 9-foot long by 9-foot deep. Accounting for 1 foot of topsoil over these trenches, the provided gravel volume is 360 cubic feet. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 WWHM2012 PROJECT REPORT Figure 4.4.1 Permeable Pavement Design Vaughn Property DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Premeable Pavement 3/22/2021 2:32:38 PM Page 2 General Model Information Project Name:Premeable Pavement Site Name: Site Address: City: Report Date:3/22/2021 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2019/09/13 Version:4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Premeable Pavement 3/22/2021 2:32:38 PM Page 4 Mitigated Land Use Lateral I Basin 1 Bypass:No Impervious Land Use acre SIDEWALKS FLAT LAT 0.19 Element Flows To: Outlet 1 Outlet 2 Permeable Pavement 1 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Premeable Pavement 3/22/2021 2:32:38 PM Page 5 Lateral I Basin 2 Bypass:No Impervious Land Use acre ROADS FLAT LAT 0.01 Element Flows To: Outlet 1 Outlet 2 Permeable Pavement 1 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Premeable Pavement 3/22/2021 2:32:38 PM Page 7 Mitigated Routing Permeable Pavement 1 Pavement Area:0.1366 acre.Pavement Length: 248.00 ft. Pavement Width: 24.00 ft. Pavement slope 1:1 To 1 Pavement thickness: 0.58 Pour Space of Pavement: 0.15 Material thickness of second layer: 1 Pour Space of material for second layer: 0.3 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Infiltration On Infiltration rate:14.8 Infiltration safety factor:1 Total Volume Infiltrated (ac-ft.):50.575 Total Volume Through Riser (ac-ft.):0 Total Volume Through Facility (ac-ft.):50.575 Percent Infiltrated:100 Total Precip Applied to Facility:0 Total Evap From Facility:1.771 Element Flows To: Outlet 1 Outlet 2 Permeable Pavement Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.136 0.000 0.000 0.000 0.0300 0.136 0.001 0.000 2.039 0.0600 0.137 0.002 0.000 2.039 0.0900 0.137 0.003 0.000 2.039 0.1200 0.137 0.004 0.000 2.039 0.1500 0.137 0.006 0.000 2.039 0.1800 0.137 0.007 0.000 2.039 0.2100 0.138 0.008 0.000 2.039 0.2400 0.138 0.009 0.000 2.039 0.2700 0.138 0.011 0.000 2.039 0.3000 0.138 0.012 0.000 2.039 0.3300 0.138 0.013 0.000 2.039 0.3600 0.139 0.014 0.000 2.039 0.3900 0.139 0.016 0.000 2.039 0.4200 0.139 0.017 0.000 2.039 0.4500 0.139 0.018 0.000 2.039 0.4800 0.139 0.019 0.000 2.039 0.5100 0.140 0.021 0.000 2.039 0.5400 0.140 0.022 0.000 2.039 0.5700 0.140 0.023 0.000 2.039 0.6000 0.140 0.025 0.000 2.039 0.6300 0.140 0.026 0.000 2.039 0.6600 0.141 0.027 0.000 2.039 0.6900 0.141 0.028 0.000 2.039 0.7200 0.141 0.030 0.000 2.039 0.7500 0.141 0.031 0.000 2.039 0.7800 0.142 0.032 0.000 2.039 0.8100 0.142 0.033 0.000 2.039 0.8400 0.142 0.035 0.000 2.039 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Premeable Pavement 3/22/2021 2:32:38 PM Page 8 0.8700 0.142 0.036 0.000 2.039 0.9000 0.142 0.037 0.000 2.039 0.9300 0.143 0.039 0.000 2.039 0.9600 0.143 0.040 0.000 2.039 0.9900 0.143 0.041 0.000 2.039 1.0200 0.143 0.042 0.000 2.039 1.0500 0.143 0.042 0.000 2.039 1.0800 0.144 0.043 0.000 2.039 1.1100 0.144 0.044 0.000 2.039 1.1400 0.144 0.044 0.000 2.039 1.1700 0.144 0.045 0.000 2.039 1.2000 0.144 0.046 0.000 2.039 1.2300 0.145 0.046 0.000 2.039 1.2600 0.145 0.047 0.000 2.039 1.2900 0.145 0.048 0.000 2.039 1.3200 0.145 0.048 0.000 2.039 1.3500 0.145 0.049 0.000 2.039 1.3800 0.146 0.050 0.000 2.039 1.4100 0.146 0.050 0.000 2.039 1.4400 0.146 0.051 0.000 2.039 1.4700 0.146 0.052 0.000 2.039 1.5000 0.146 0.052 0.000 2.039 1.5300 0.147 0.053 0.000 2.039 1.5600 0.147 0.054 0.000 2.039 1.5900 0.147 0.058 0.016 2.039 1.6200 0.147 0.062 0.133 2.039 1.6500 0.148 0.067 0.308 2.039 1.6800 0.148 0.071 0.526 2.039 1.7100 0.148 0.076 0.780 2.039 1.7400 0.148 0.080 1.065 2.039 1.7700 0.148 0.085 1.378 2.039 1.8000 0.149 0.089 1.718 2.039 1.8300 0.149 0.094 2.081 2.039 1.8600 0.149 0.098 2.466 2.039 1.8900 0.149 0.103 2.873 2.039 1.9200 0.149 0.107 3.300 2.039 1.9500 0.150 0.112 3.747 2.039 1.9800 0.150 0.116 4.212 2.039 2.0100 0.150 0.121 4.694 2.039 2.0400 0.150 0.125 5.194 2.039 2.0700 0.150 0.130 5.711 2.039 2.1000 0.151 0.134 6.243 2.039 2.1300 0.151 0.139 6.791 2.039 2.1600 0.151 0.143 7.354 2.039 2.1900 0.151 0.148 7.932 2.039 2.2200 0.152 0.152 8.524 2.039 2.2500 0.152 0.157 9.131 2.039 2.2800 0.152 0.161 9.751 2.039 2.3100 0.152 0.166 10.38 2.039 2.3400 0.152 0.171 11.03 2.039 2.3700 0.153 0.175 11.69 2.039 2.4000 0.153 0.180 12.36 2.039 2.4300 0.153 0.184 13.04 2.039 2.4600 0.153 0.189 13.74 2.039 2.4900 0.153 0.194 14.45 2.039 2.5200 0.154 0.198 15.17 2.039 2.5500 0.154 0.203 15.90 2.039 2.5800 0.154 0.207 16.65 2.039 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Premeable Pavement 3/22/2021 2:32:38 PM Page 9 2.6100 0.154 0.212 17.40 2.039 2.6400 0.154 0.217 18.17 2.039 2.6700 0.155 0.221 18.94 2.039 2.7000 0.155 0.226 19.73 2.039 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Premeable Pavement 3/22/2021 2:34:13 PM Page 18 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Premeable Pavement 3/22/2021 2:34:19 PM Page 20 Mitigated Schematic DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Premeable Pavement 3/22/2021 2:34:23 PM Page 25 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2021; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 4.5 Water Quality System This project is required to provide Basic Water Quality treatment according to the 2017 City of Renton Surface Water Design Manual. According to this manual, the soil properties below the permeable pavement section must meet certain requirements to provide water quality treatment for all pollution generating impervious surfaces. The requirements for the underlying soil are as follows:  Minimum organic matter content of 1.0% and  Minimum cation exchange capacity of 8 milliequivalents per 100 grams The City of Renton Surface Water Design Manual states that if the underlying soil does not meet these minimum requirements, a 6-inch sand layer must be included in the design beneath the permeable pavement section. According to the Soil Properties for Groundwater Protection section found in the Geotechnical Engineering Study prepared by Earth Solutions NW, the underlying soil does not meet these minimum requirements. Because of this, a 6-inch sand layer will be placed below the proposed permeable pavement road section. The proposed drywells located within each lot will only receive runoff from rooftop areas which are classified as non-pollution generating impervious surfaces. Because of this, water quality requirements are satisfied through the use of this BMP. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Tab 5.0 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN The on-site and frontage conveyance system will consist of curb, gutter, catch basins and storm drainage pipe. Conveyance calculations for the pipes will be completed using the rational method and will be provided during final engineering. These conveyance systems will be designed in accordance with the City of Renton Surface Water Design Manual. The on-site conveyance system will also be designed to collect any excess runoff above the 100-year storm that is not infiltrated by the permeable pavement road section. This runoff will be routed back to Aberdeen Ave NE and connect to the proposed conveyance system along the project frontage. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Tab 6.0 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 6.0 SPECIAL REPORTS AND STUDIES 6.1 Geotechnical Engineering Study prepared by Earth Solutions NW, LLC. dated March 16, 2021 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 EarthSolutionsNWLLC EarthSolutions NW LLC Geotechnical Engineering Construction Observation/Testing Environmental Services 15365 N.E.90th Street,Suite 100 Redmond,WA 98052 (425)449-4704 Fax (425)449-4711 www.earthsolutionsnw.com GEOTECHNICAL ENGINEERING STUDY PROPOSED SHORT PLAT 1400 ABERDEEN AVENUE NORTHEAST RENTON,WASHINGTON ES-7334 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 PREPARED FOR MAINVUE WA, LLC March 16, 2021 _________________________ Keven D. Hoffmann, P.E. Senior Project Manager _________________________ Kyle R. Campbell, P.E. Principal Engineer GEOTECHNICAL ENGINEERING STUDY PROPOSED SHORT PLAT 1400 ABERDEEN AVENUE NORTHEAST RENTON, WASHINGTON ES-7334 Earth Solutions NW, LLC 15365 Northeast 90th Street, Suite 100 Redmond, Washington 98052 Phone: 425-449-4704 | Fax: 425-449-4711 www.earthsolutionsnw.com 03/16/2021 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Geotechnical-Engineering Report Important Information about This Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes. While you cannot eliminate all such risks, you can manage them. The following information is provided to help. The Geoprofessional Business Association (GBA) has prepared this advisory to help you – assumedly a client representative – interpret and apply this geotechnical-engineering report as effectively as possible. In that way, you can benefit from a lowered exposure to problems associated with subsurface conditions at project sites and development of them that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed herein, contact your GBA-member geotechnical engineer. Active engagement in GBA exposes geotechnical engineers to a wide array of risk-confrontation techniques that can be of genuine benefit for everyone involved with a construction project. Understand the Geotechnical-Engineering Services Provided for this Report Geotechnical-engineering services typically include the planning, collection, interpretation, and analysis of exploratory data from widely spaced borings and/or test pits. Field data are combined with results from laboratory tests of soil and rock samples obtained from field exploration (if applicable), observations made during site reconnaissance, and historical information to form one or more models of the expected subsurface conditions beneath the site. Local geology and alterations of the site surface and subsurface by previous and proposed construction are also important considerations. Geotechnical engineers apply their engineering training, experience, and judgment to adapt the requirements of the prospective project to the subsurface model(s). Estimates are made of the subsurface conditions that will likely be exposed during construction as well as the expected performance of foundations and other structures being planned and/or affected by construction activities. The culmination of these geotechnical-engineering services is typically a geotechnical-engineering report providing the data obtained, a discussion of the subsurface model(s), the engineering and geologic engineering assessments and analyses made, and the recommendations developed to satisfy the given requirements of the project. These reports may be titled investigations, explorations, studies, assessments, or evaluations. Regardless of the title used, the geotechnical-engineering report is an engineering interpretation of the subsurface conditions within the context of the project and does not represent a close examination, systematic inquiry, or thorough investigation of all site and subsurface conditions. Geotechnical-Engineering Services are Performed for Specific Purposes, Persons, and Projects, and At Specific Times Geotechnical engineers structure their services to meet the specific needs, goals, and risk management preferences of their clients. A geotechnical-engineering study conducted for a given civil engineer will not likely meet the needs of a civil-works constructor or even a different civil engineer. Because each geotechnical-engineering study is unique, each geotechnical-engineering report is unique, prepared solely for the client. Likewise, geotechnical-engineering services are performed for a specific project and purpose. For example, it is unlikely that a geotechnical- engineering study for a refrigerated warehouse will be the same as one prepared for a parking garage; and a few borings drilled during a preliminary study to evaluate site feasibility will not be adequate to develop geotechnical design recommendations for the project. Do not rely on this report if your geotechnical engineer prepared it: • for a different client; • for a different project or purpose; • for a different site (that may or may not include all or a portion of the original site); or • before important events occurred at the site or adjacent to it; e.g., man-made events like construction or environmental remediation, or natural events like floods, droughts, earthquakes, or groundwater fluctuations. Note, too, the reliability of a geotechnical-engineering report can be affected by the passage of time, because of factors like changed subsurface conditions; new or modified codes, standards, or regulations; or new techniques or tools. If you are the least bit uncertain about the continued reliability of this report, contact your geotechnical engineer before applying the recommendations in it. A minor amount of additional testing or analysis after the passage of time – if any is required at all – could prevent major problems. Read this Report in Full Costly problems have occurred because those relying on a geotechnical- engineering report did not read the report in its entirety. Do not rely on an executive summary. Do not read selective elements only. Read and refer to the report in full. You Need to Inform Your Geotechnical Engineer About Change Your geotechnical engineer considered unique, project-specific factors when developing the scope of study behind this report and developing the confirmation-dependent recommendations the report conveys. Typical changes that could erode the reliability of this report include those that affect: • the site’s size or shape; • the elevation, configuration, location, orientation, function or weight of the proposed structure and the desired performance criteria; • the composition of the design team; or • project ownership. As a general rule, always inform your geotechnical engineer of project or site changes – even minor ones – and request an assessment of their impact. The geotechnical engineer who prepared this report cannot accept DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered. Most of the “Findings” Related in This Report Are Professional Opinions Before construction begins, geotechnical engineers explore a site’s subsurface using various sampling and testing procedures. Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing is performed. The data derived from that sampling and testing were reviewed by your geotechnical engineer, who then applied professional judgement to form opinions about subsurface conditions throughout the site. Actual sitewide-subsurface conditions may differ – maybe significantly – from those indicated in this report. Confront that risk by retaining your geotechnical engineer to serve on the design team through project completion to obtain informed guidance quickly, whenever needed. This Report’s Recommendations Are Confirmation-Dependent The recommendations included in this report – including any options or alternatives – are confirmation-dependent. In other words, they are not final, because the geotechnical engineer who developed them relied heavily on judgement and opinion to do so. Your geotechnical engineer can finalize the recommendations only after observing actual subsurface conditions exposed during construction. If through observation your geotechnical engineer confirms that the conditions assumed to exist actually do exist, the recommendations can be relied upon, assuming no other changes have occurred. The geotechnical engineer who prepared this report cannot assume responsibility or liability for confirmation-dependent recommendations if you fail to retain that engineer to perform construction observation. This Report Could Be Misinterpreted Other design professionals’ misinterpretation of geotechnical- engineering reports has resulted in costly problems. Confront that risk by having your geotechnical engineer serve as a continuing member of the design team, to: • confer with other design-team members; • help develop specifications; • review pertinent elements of other design professionals’ plans and specifications; and • be available whenever geotechnical-engineering guidance is needed. You should also confront the risk of constructors misinterpreting this report. Do so by retaining your geotechnical engineer to participate in prebid and preconstruction conferences and to perform construction- phase observations. Give Constructors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can shift unanticipated-subsurface-conditions liability to constructors by limiting the information they provide for bid preparation. To help prevent the costly, contentious problems this practice has caused, include the complete geotechnical-engineering report, along with any attachments or appendices, with your contract documents, but be certain to note conspicuously that you’ve included the material for information purposes only. To avoid misunderstanding, you may also want to note that “informational purposes” means constructors have no right to rely on the interpretations, opinions, conclusions, or recommendations in the report. Be certain that constructors know they may learn about specific project requirements, including options selected from the report, only from the design drawings and specifications. Remind constructors that they may perform their own studies if they want to, and be sure to allow enough time to permit them to do so. Only then might you be in a position to give constructors the information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Conducting prebid and preconstruction conferences can also be valuable in this respect. Read Responsibility Provisions Closely Some client representatives, design professionals, and constructors do not realize that geotechnical engineering is far less exact than other engineering disciplines. This happens in part because soil and rock on project sites are typically heterogeneous and not manufactured materials with well-defined engineering properties like steel and concrete. That lack of understanding has nurtured unrealistic expectations that have resulted in disappointments, delays, cost overruns, claims, and disputes. To confront that risk, geotechnical engineers commonly include explanatory provisions in their reports. Sometimes labeled “limitations,” many of these provisions indicate where geotechnical engineers’ responsibilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions. Your geotechnical engineer should respond fully and frankly. Geoenvironmental Concerns Are Not Covered The personnel, equipment, and techniques used to perform an environmental study – e.g., a “phase-one” or “phase-two” environmental site assessment – differ significantly from those used to perform a geotechnical-engineering study. For that reason, a geotechnical-engineering report does not usually provide environmental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated subsurface environmental problems have led to project failures. If you have not obtained your own environmental information about the project site, ask your geotechnical consultant for a recommendation on how to find environmental risk-management guidance. Obtain Professional Assistance to Deal with Moisture Infiltration and Mold While your geotechnical engineer may have addressed groundwater, water infiltration, or similar issues in this report, the engineer’s services were not designed, conducted, or intended to prevent migration of moisture – including water vapor – from the soil through building slabs and walls and into the building interior, where it can cause mold growth and material-performance deficiencies. Accordingly, proper implementation of the geotechnical engineer’s recommendations will not of itself be sufficient to prevent moisture infiltration. Confront the risk of moisture infiltration by including building-envelope or mold specialists on the design team. Geotechnical engineers are not building-envelope or mold specialists. Copyright 2019 by Geoprofessional Business Association (GBA). Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly prohibited, except with GBA’s specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission of GBA, and only for purposes of scholarly research or book review. Only members of GBA may use this document or its wording as a complement to or as an element of a report of any kind. Any other firm, individual, or other entity that so uses this document without being a GBA member could be committing negligent or intentional (fraudulent) misrepresentation. Telephone: 301/565-2733 e-mail: info@geoprofessional.org www.geoprofessional.org DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 March 16, 2021 ES-7334 MainVue WA, LLC 1110 – 112th Avenue Northeast, Suite 202 Bellevue, Washington 98004 Attention: Ms. Lisa Cavell Greetings, Ms. Cavell: Earth Solutions NW, LLC (ESNW) is pleased to present this geotechnical report for the subject site. Our investigation indicates the proposed short plat is feasible from a geotechnical standpoint generally as planned. The site is underlain primarily by recessional outwash sand, with varying fines content. The proposed residential structures can be supported on conventional spread and continuous footings bearing on undisturbed competent native soil, compacted native soil, or new structural fill. We anticipate competent native soil suitable for support of foundations will be encountered beginning at a depth of about two feet below existing grades. Where loose or unsuitable soil conditions are encountered at foundation subgrade elevations, compaction of the soil to the specifications of structural fill or overexcavation and replacement with suitable structural fill will likely be necessary. This report provides geotechnical analyses and recommendations for the proposed short plat. The opportunity to be of service to you is appreciated. If you have any questions regarding the content of this geotechnical engineering study, please call. Sincerely, EARTH SOLUTIONS NW, LLC Keven D. Hoffmann, P.E. Senior Project Manager 15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 •(425) 449-4704 • FAX (425) 449-4711 Earth Solutions NW LLC Geotechnical Engineering, Construction Observation/Testing and Environmental Services DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Earth Solutions NW, LLC Table of Contents ES-7334 PAGE INTRODUCTION ................................................................................. 1 General..................................................................................... 1 Project Description ................................................................. 2 SITE CONDITIONS ............................................................................. 2 Surface ..................................................................................... 2 Subsurface .............................................................................. 2 Topsoil and Fill ............................................................. 3 Native Soil ..................................................................... 3 Geologic Setting ........................................................... 3 Groundwater ................................................................. 3 Critical Areas Review ............................................................. 3 DISCUSSION AND RECOMMENDATIONS ....................................... 4 General..................................................................................... 4 Site Preparation and Earthwork ............................................. 4 Temporary Erosion Control ......................................... 4 In-Situ and Imported Soil ............................................. 5 Structural Fill ................................................................ 5 Subgrade Preparation .................................................. 6 Excavations and Slopes .............................................. 6 Foundations ............................................................................ 6 Seismic Design ....................................................................... 7 Slab-on-Grade Floors ............................................................. 8 Retaining Walls ....................................................................... 8 Drainage................................................................................... 9 Infiltration Testing & Design ....................................... 9 Permeable Pavement Design ...................................... 10 Soil Properties for Groundwater Protection .............. 11 Drywells & Gravel-filled Trenches .............................. 11 Utility Support and Trench Backfill ....................................... 11 LIMITATIONS ...................................................................................... 12 Additional Services ................................................................. 12 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Earth Solutions NW, LLC Table of Contents Cont’d ES-7334 GRAPHICS Plate 1 Vicinity Map Plate 2 Test Pit Location Plan Plate 3 Retaining Wall Drainage Detail Plate 4 Footing Drain Detail APPENDICES Appendix A Subsurface Exploration Test Pit Logs Appendix B Laboratory Test Results DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Earth Solutions NW, LLC GEOTECHNICAL ENGINEERING STUDY PROPOSED SHORT PLAT 1400 ABERDEEN AVENUE NORTHEAST RENTON, WASHINGTON ES-7334 INTRODUCTION General This geotechnical engineering study was prepared for the proposed short plat to be constructed southeast of the intersection between Northeast 15th Street and Aberdeen Avenue Northeast, in Renton, Washington. This report was prepared to aid the subject project with respect to the currently proposed site layout. To prepare this report, the following scope items or services were completed:  Subsurface exploration to characterize the soil and groundwater conditions.  In-situ infiltration testing.  Laboratory testing of representative soil samples collected on site.  Review of on-site critical areas.  Engineering analyses and recommendations for the proposed short plat. The following documents and resources were reviewed as part of our report preparation:  Draft ALTA/NSPS Land Title Survey, prepared by Barghausen Consulting Engineers, Inc., dated November 21, 2020.  Geologic Map of King County, compiled by Derek B. Booth, Kathy G. Troost, and Aaron P. Wisher, dated March 2007.  Online Web Soil Survey (WSS) resource, maintained by the Natural Resources Conservation Service (NRCS) under the United States Department of Agriculture (USDA).  Liquefaction Susceptibility of King County (Map 11-5), endorsed by the King County Flood Control District, dated May 2010.  Renton Municipal Code (RMC).  Online COR Maps Resource, maintained by the City of Renton.  2017 City of Renton Surface Water Design Manual. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 2 Earth Solutions NW, LLC Project Description We understand the existing residential structures will be removed, and a short plat will be constructed. At the time this report was prepared, neither a formal site plan nor building load values were available for review. However, we anticipate the proposed residential structures will be two to three stories and constructed using relatively lightly loaded wood framing supported atop conventional foundation systems. Based on our experience with similar developments, we estimate wall loads of about 1 to 2 kips per linear foot and slab-on-grade loading of 150 pounds per square foot (psf) will be incorporated into the final design. Grade cuts and fills to establish individual-lot subgrade and finish grade elevations are expected to be less than five feet. Retaining walls or rockeries may be constructed across the plat to accommodate grade transitions, where necessary. A stormwater infiltration facility will likely be constructed within the topographically low area of the site (southeastern corner). If the above design assumptions either change or are incorrect, ESNW should be contacted to review the recommendations provided in this report. ESNW should review final designs to verify the geotechnical recommendations provided in this report have been incorporated into the plans. SITE CONDITIONS Surface The subject site is located southeast of the intersection between Northeast 15 th Street and Aberdeen Avenue Northeast, in Renton, Washington. The approximate location of the property is illustrated on Plate 1 (Vicinity Map). The site is comprised of one tax parcel (King County Parcel No. 334390-1680), totaling about 1.68 acres. The site is currently occupied by a single-family residence and various outbuildings. The existing topography descends generally from north to south, with an estimated 10 to 15 feet of elevation change across the site. Vegetation consists mainly of lawn areas, with several scattered trees. Subsurface An ESNW representative observed, logged, and sampled six test pits on June 4, 2020. The test pits were excavated at accessible locations within the property, using a trackhoe and operator retained by our firm. The approximate locations of the test pits are depicted on Plate 2 (Test Pit Location Plan). Please refer to the test pit logs provided in Appendix A for a more detailed description of subsurface conditions. Representative soil samples collected at the test pit locations were analyzed in general accordance with both Unified Soil Classification System (USCS) and USDA methods and procedures. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 3 Earth Solutions NW, LLC Topsoil and Fill Topsoil was generally encountered within the upper six inches of existing grades at the test locations. The topsoil was characterized by a dark brown color, the presence of fine organic material, and small root intrusions. Fill was encountered at TP-2 to a depth of roughly six inches below the existing ground surface (bgs). The fill contained wire debris and trace root intrusions. Fill was not encountered elsewhere on site. Native Soil Underneath the topsoil, the native soil consisted primarily of poorly graded sand with varying silt content. Within roughly the upper two-and-one-half to five feet of existing grades, sand with appreciable fines content (USCS: SP-SM or SM) was encountered. The native soil graded to comparatively cleaner sand (USCS: SP) at depth, except at TP-4. The native deposits were observed primarily in a “moist” or “moist to wet” condition at the time of the exploration. The maximum exploration depth was roughly 18.5 feet bgs. Geologic Setting Based on our review of the referenced geologic map, the site is underlain by recessional outwash (Qvr). Recessional outwash was deposited by glacial meltwater and is readily comprised of silt, clay, sand, and gravel. The referenced WSS resource identifies Indianola loamy sand (Map Unit Symbol: InC) across the site and surrounding area. The Indianola series was formed in eskers, kames, and terraces. Based on our field observations, the native soil encountered on site is generally consistent with the information presented in the referenced geologic and soil mapping resources. Groundwater Groundwater was not encountered at the test locations during the June 2020 exploration. Nonetheless, transient, perched groundwater seepage may develop seasonally and may be encountered within site excavations depending on the time of year and extent of grading activities. Seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater flow rates are higher during the winter, spring, and early summer months. Critical Areas Review To evaluate the presence of critical areas on site, we reviewed RMC Chapter 4-3 and the online COR Maps resource. The RMC provides designation and definition criteria for identifying critical areas and developing appropriate site development plans to limit adverse impacts to critical areas both on and off site. Based on our review, the site is mapped within Zone 2 of a Wellhead Protection Area (WPA). No other critical areas (including coalmine hazard, high erosion hazard, flood hazard, landslide hazard, regulated slopes, and seismic hazard) are mapped on site or immediately adjacent to the site. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 4 Earth Solutions NW, LLC With respect to the mapped WPA, the proposal should comply with the requirements of RMC 4- 3-050, particularly concerning activities that are not permitted within a WPA. Residential plats are commonly constructed within WPAs and critical aquifer recharge areas, including those that incorporate stormwater infiltration into the final design. Based on our understanding of the project, the proposal does not intend to incorporate activities that would adversely impact the WPA or would otherwise be prohibited under the RMC. ESNW can provide additional consulting and plan review services pertaining to the WPA, upon request. DISCUSSION AND RECOMMENDATIONS General Based on the results of our investigation, construction of the proposed short plat is feasible from a geotechnical standpoint. The primary geotechnical considerations associated with the proposed development include site preparation and earthwork, suitability of on-site soil as structural fill, subgrade preparation, temporary excavations, building foundations, and stormwater facility construction. Site Preparation and Earthwork Site preparation activities should consist of installing temporary erosion control measures, removing existing structural improvements, and performing site stripping within the designated clearing limits. Subsequent earthwork activities will involve mass grading and utility installations. Temporary Erosion Control The following temporary erosion and sediment control (TESC) Best Management Practices (BMPs) are offered:  Temporary construction entrances and drive lanes, consisting of at least six inches of quarry spalls, should be considered to both minimize off-site soil tracking and provide a stable access entrance surface. Placing geotextile fabric underneath the quarry spalls will provide greater stability, if needed.  Silt fencing should be placed around appropriate portions of the site perimeter.  When not in use, soil stockpiles should be covered or otherwise protected to reduce the potential for soil erosion, especially during periods of wet weather.  Temporary measures for controlling surface water runoff, such as interceptor trenches, sumps, or interceptor swales, should be installed prior to beginning earthwork activities.  Dry soils disturbed during construction should be wetted to minimize dust.  When appropriate, permanent planting or hydroseeding will help to stabilize the site soil. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 5 Earth Solutions NW, LLC Additional TESC BMPs, as specified by the project civil engineer and indicated on the plans, should be incorporated into construction activities. TESC measures may be modified during construction as site conditions require but should be discussed with and approved by the site erosion control lead. In-Situ and Imported Soil On-site soil exposed during earthwork and grading activities will likely consist primarily of silty sand and poorly graded sand with silt. The native soil possesses moderate moisture sensitivity and will not be suitable for use as structural fill unless the soil is at (or slightly above) the optimum moisture content at the time of placement and compaction. If the on-site soil cannot be successfully compacted, the use of an imported soil may be necessary. In our opinion, a contingency should be provided in the project budget for export of soil that cannot be successfully compacted as structural fill if grading activities take place during periods of rainfall activity. We recommend avoiding construction-equipment tracking across the native soil and generally active site work during periods of heavy rainfall; such disturbance has the potential to degrade the native soil beyond a workable state. Imported soil intended for use as structural fill should consist of a well-graded, granular soil with a moisture content that is at (or slightly above) the optimum level. During wet weather conditions, imported soil intended for use as structural fill should consist of a well-graded, granular soil with a fines content of 5 percent or less (where the fines content is defined as the percent passing the Number 200 sieve, based on the minus three-quarter-inch fraction). Structural Fill Structural fill is defined as compacted soil placed in foundation, slab-on-grade, roadway, permanent slope, retaining wall, and utility trench backfill areas. Structural fill placed and compacted during site grading activities should meet the following specifications and guidelines:  Structural fill material Granular soil*  Moisture content At or slightly above optimum †  Relative compaction (minimum) 95 percent (Modified Proctor)  Loose lift thickness (maximum) 12 inches * Existing soil will not be suitable for use as structural fill unless at (or slightly above) the optimum moisture content at the time of placement and compaction. † Soil shall not be placed dry of optimum and should be evaluated by ESNW during construction. With respect to underground utility installations and backfill, local jurisdictions may dictate the soil type(s) and compaction requirements. Unsuitable material or debris must be removed from structural areas if encountered. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 6 Earth Solutions NW, LLC Subgrade Preparation Following site stripping, ESNW should observe the subgrade to confirm soil conditions are as anticipated and to provide supplementary recommendations for subgrade preparation, as necessary. In general, foundation subgrade surfaces should be compacted in situ to a minimum depth of one foot below the design subgrade elevation. Uniform compaction of the foundation and slab subgrade areas will establish a relatively consistent subgrade condition below the foundation and slab elements. Supplementary recommendations for subgrade improvement may be provided at the time of construction and would likely include further mechanical compaction or overexcavation and replacement with suitable structural fill. Excavations and Slopes Excavation activities are likely to expose medium dense silty sand and/or poorly graded sand. Based on the soil conditions observed at the test pit locations, a maximum inclination of one-and- one-half horizontal to one vertical (1.5H:1V) is recommended for temporary excavations and slopes. Per Federal Occupation Safety and Health Administration and Washington Industrial Safety and Health Act standards, the native soil classifies as Type C. Steeper temporary inclinations with dense, undisturbed native soil (such as 1H:1V) may be feasible but must be evaluated by ESNW on a case-by-case basis during construction. Permanent slopes should be planted with vegetation to both enhance stability and minimize erosion and should maintain a gradient of 2H:1V or flatter. An ESNW representative should observe temporary and permanent slopes to confirm the slope inclinations are suitable for the exposed soil conditions and to provide additional excavation and slope recommendations, as necessary. Foundations The proposed residential structures can be supported on conventional spread and continuous footings bearing on undisturbed competent native soil, compacted native soil, or new structural fill. We anticipate competent native soil suitable for support of foundations will be encountered beginning at a depth of about two feet bgs. Where loose or unsuitable soil conditions are encountered at foundation subgrade elevations, compaction of the soil to the specifications of structural fill or overexcavation and replacement with suitable structural fill will likely be necessary. Provided the structure will be supported as described above, the following parameters may be used for design of the new foundations:  Allowable soil bearing capacity 2,500 psf  Passive earth pressure 300 pcf  Coefficient of friction 0.40 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 7 Earth Solutions NW, LLC A one-third increase in the allowable soil bearing capacity can be assumed for short-term wind and seismic loading conditions. The passive earth pressure and coefficient of friction values include a safety factor of 1.5. With structural loading as expected, total settlement in the range of one inch is anticipated, with differential settlement of about one-half inch. Most of the settlement should occur during construction when dead loads are applied. Seismic Design The 2018 International Building Code (2018 IBC) recognizes the most recent edition of the Minimum Design Loads for Buildings and Other Structures manual (ASCE 7-16) for seismic design, specifically with respect to earthquake loads. Based on the soil conditions encountered at the test pit locations, the parameters and values provided below are recommended for seismic design per the 2018 IBC. Parameter Value Site Class D* Mapped short period spectral response acceleration, S S (g) 1.437 Mapped 1-second period spectral response acceleration, S 1 (g) 0.492 Short period site coefficient, Fa 1.000 Long period site coefficient, Fv 1.808† Adjusted short period spectral response acceleration, S MS (g) 1.437 Adjusted 1-second period spectral response acceleration, S M1 (g) 0.890† Design short period spectral response acceleration, S DS (g) 0.958 Design 1-second period spectral response acceleration, S D1 (g) 0.593† * Assumes medium dense native soil conditions, encountered to a maximum depth of 18.5 feet bgs during the June 2020 field exploration, remain medium dense (or dense) to at least 100 feet bgs. † Values assume Fv may be determined using linear interpolation per Table 11.4-2 in ASCE 7-16. As indicated in the table footnote, several of the seismic design values provided above are dependent on the assumption that site-specific ground motion analysis (per Section 11.4.8 of ASCE 7-16) will not be required for the subject project. ESNW recommends the validity of this assumption be confirmed at the earliest available opportunity during the planning and early design stages of the project. Further discussion between the project structural engineer, the project owner, and ESNW may be prudent to determine the possible impacts to the structural design due to increased earthquake load requirements under the 2018 IBC. ESNW can provide additional consulting services to aid with design efforts, including supplementary geotechnical and geophysical investigation, upon request. Liquefaction is a phenomenon where saturated or loose soil suddenly loses internal strength and behaves as a fluid. This behavior is in response to increased pore water pressures resulting from an earthquake or another intense ground shaking. In our opinion, site susceptibility to liquefaction may be considered low. The absence of a shallow groundwater table and the relatively dense characteristics of the native soil were the primary bases for this opinion. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 8 Earth Solutions NW, LLC Slab-on-Grade Floors Slab-on-grade floors should be supported on firm and unyielding subgrades consisting of competent native soil or at least 12 inches of new structural fill. Unstable or yielding subgrade areas should be recompacted or overexcavated and replaced with suitable structural fill prior to slab construction. A capillary break consisting of a minimum of four inches of free-draining crushed rock or gravel should be placed below each slab. The free-draining material should have a fines content of 5 percent or less (where the fines content is defined as the percent passing the Number 200 sieve, based on the minus three-quarter-inch fraction). In areas where slab moisture is undesirable, installation of a vapor barrier below the slab should be considered. If used, the vapor barrier should consist of a material specifically designed to function as a vapor barrier and should be installed in accordance with the manufacturer’s specifications. Retaining Walls Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The following parameters may be used for retaining wall design:  Active earth pressure (unrestrained condition) 35 pcf  At-rest earth pressure (restrained condition) 55 pcf  Traffic surcharge (passenger vehicles) 70 psf (rectangular distribution)  Passive earth pressure 300 pcf  Coefficient of friction 0.40  Seismic surcharge 8H psf* * Where H equals the retained height (in feet) The passive earth pressure and coefficient of friction values include a safety factor of 1.5. Additional surcharge loading from adjacent foundations, sloped backfill, or other loads should be included in the retaining wall design. Drainage should be provided behind retaining walls such that hydrostatic pressures do not develop. If drainage is not provided, hydrostatic pressures should be included in the wall design. Retaining walls should be backfilled with free-draining material that extends along the height of the wall and a distance of at least 18 inches behind the wall. The upper 12 inches of the wall backfill may consist of a less permeable soil, if desired. A perforated drainpipe should be placed along the base of the wall and connected to an approved discharge location. A typical retaining wall drainage detail is provided on Plate 3. If drainage is not provided, hydrostatic pressures should be included in the wall design. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 9 Earth Solutions NW, LLC Drainage Discrete zones of perched groundwater seepage should be anticipated in site excavations depending on the time of year grading operations take place. Temporary measures to control surface water runoff and groundwater during construction would likely involve interceptor trenches, interceptor swales, and sumps. ESNW should be consulted during preliminary grading to both identify areas of seepage and provide recommendations to reduce the potential for seepage-related instability. Finish grades must be designed to direct surface drain water away from structures and slopes. Water must not be allowed to pond adjacent to structures or slopes. In our opinion, foundation drains should be installed along building perimeter footings. A typical foundation drain detail is provided on Plate 4. Infiltration Testing & Design In accordance with the 2017 City of Renton Surface Water Design Manual (2017 RSWDM), one small-scale Pilot Infiltration Test (PIT) was completed during the fieldwork. The PIT was completed at TP-3 by excavating a test pit with a roughly three-foot by four-foot base infiltration surface. The infiltration test was completed at a depth of about five feet bgs and followed the PIT procedure prescribed in the 2017 RSWDM. Based on the results of the PIT, the following design parameters are recommended:  Imeasured (measured infiltration rate; TP-3) 44 inches per hour (in/hr)  Ftesting 0.5 (small-scale PIT)  Fgeometry 0.75 (assumed)  Fplugging 0.9 (medium sand)  Idesign (calculated infiltration rate; TP-3) 14.8 in/hr ESNW should be contacted to review stormwater management plans if infiltration is used for design. Supplementary recommendations and/or testing may be necessary depending on the size, depth, and siting of infiltration facilities. Per pages 5-51 and 5-52 of the 2017 RSWDM, the native soil underneath an infiltration facility is expected to inherently possess specific characteristics to minimize groundwater contamination. The test results provided in the Soil Properties for Groundwater Protection section of this report indicate the native soil in the proposed infiltration facility area does not meet the groundwater- protection requirements, mainly due to suboptimal cation exchange capacity (CEC) values and rapid infiltration rates. Accordingly, water quality treatment will need to be provided prior to infiltration. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 10 Earth Solutions NW, LLC Permeable Pavement Design We understand permeable pavement may be incorporated into the final design. Because the permeable roadway surface would be used for occasional emergency vehicle access, the design must comply with H-20 loading specifications. Based on the soil conditions encountered at the exploration locations, the following permeable pavement sections are offered to meet H-20 loading specifications from a geotechnical standpoint:  Permeable base course (for either permeable asphalt or permeable concrete) o Minimum thickness: 12 inches o Material: Permeable ballast per WSDOT 9-03.9(2), or approved equivalent o Void content: 30 to 40 percent  Permeable asphalt o Minimum thickness: 3 inches of permeable warm-mix asphalt (WMA) underlain by 4 inches of asphalt-treated permeable base o Permeable hot-mix asphalt (HMA) is allowed in lieu of WMA, but WMA is preferred  Permeable concrete o Minimum thickness: 6 inches o Unit weight: 120 to 135 pcf o Void content: 18 to 20 percent Per page C-76 of the 2017 RSWDM, the native soil underneath the permeable pavement surface must meet minimum CEC and organic content (OC) values of 8 meq/100 g and 1.0 percent, respectively. The test results provided in the Soil Properties for Groundwater Protection section of this report indicate the native soil expected to underlie permeable pavement areas will not meet these minimum requirements. Accordingly, a six-inch sand layer must be included in the design beneath the permeable pavement. ESNW should be retained to observe pavement installation activities and provide applicable consulting and testing services. Supplementary recommendations may be provided at the time of construction, as needed. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 11 Earth Solutions NW, LLC Soil Properties for Groundwater Protection Representative soil samples were analyzed for CEC, OC, and grain size distribution. The results of the relevant testing are summarized in the table below, and the laboratory data is provided in Appendix B. Test Pit Depth (ft bgs) CEC (meq/100 g) OC (%) % Passing No. 4 Sieve % Passing No. 40 Sieve % Passing No. 100 Sieve TP-1 2.0 5.6 2.5 99.8 67.0 10.3 TP-2 2.0 7.9 3.4 (not sieved) TP-3 5.0 3.7 1.4 (not sieved) TP-3 10.5 2.8 1.1 98.3 23.0 2.1 TP-4 2.5 5.4 2.5 (not sieved) TP-5 3.0 5.1 2.0 100 82.5 24.4 TP-6 2.5 8.1 3.8 99.6 78.0 25.4 Drywells & Gravel-filled Trenches Where drywells and/or gravel-filled trenches are incorporated into the final design, it is our opinion the dominant soil grain size should be considered “medium sand”. Per page C-47 of the 2017 RSWDM, drywells must contain at least 90 cubic feet of gravel per 1,000 square feet of impervious surface served. Gravel-filled trenches must be at least 30 feet in length per 1,000 square feet of impervious surface served. ESNW can provide additional consulting services and recommendations for full infiltration BMPs, upon request. Utility Support and Trench Backfill In our opinion, the native soil will likely be suitable for support of utilities. Remedial measures may be necessary in some areas to provide support for utilities, such as overexcavation and replacement with structural fill and/or placement of geotextile fabric. Groundwater seepage may be encountered within utility excavations, and caving of trench walls should be anticipated given the cohesionless nature of site soils. Depending on the time of year and conditions encountered, dewatering or temporary trench shoring may be necessary during utility excavation and installation. In general, the native soil may not be suitable for use as structural backfill throughout utility trench excavations unless the soil is at (or slightly above) the optimum moisture content at the time of placement and compaction. Moisture conditioning of the soil may be necessary at some locations prior to use as structural fill. Each section of the utility lines must be adequately supported in appropriate bedding material. Utility trench backfill should be placed and compacted to the specifications of structural fill previously detailed in this report or to the applicable specifications of the presiding jurisdiction. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 12 Earth Solutions NW, LLC LIMITATIONS This study has been prepared for the exclusive use of MainVue WA, LLC, and its representatives. The recommendations and conclusions provided in the geotechnical engineering study are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. No warranty, express or implied, is made. Variations in the soil and groundwater conditions observed at the test pit locations may exist and may not become evident until construction. ESNW should reevaluate the conclusions provided in this geotechnical engineering study if variations are encountered. Additional Services ESNW should have an opportunity to review the final design with respect to the geotechnical recommendations provided in this report. ESNW should also be retained to provided testing and consultation services during construction. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Drwn.MRS Checked KDH Date Mar.2021 Date 03/09/2021 Proj.No.7334 Plate 1 Earth Solutions NWLLC Geotechnical Engineering,Construction EarthSolutionsNWLLC EarthSolutions NW LLC Obser vation/Testing and Environmental Services Vicinity Map Vaughn Short Plat Renton,Washington NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. Reference: King County,Washington OpenStreetMap.org NORTH SITE Renton DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Plate Proj.No. Date Checked By Drwn.ByEarthSolutionsNWLLCGeotechnicalEngineering,ConstructionObservation/TestingandEnvironmentalServicesEarthSolutionsNWLLCEarthSolutionsNWLLCTestPitLocationPlanVaughnShortPlatRenton,WashingtonNORTH NOT -TO -SCALE NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. NOTE:The graphics shown on this plate are not intended for design purposes or precise scale measurements,but only to illustrate the approximate test locations relative to the approximate locations of existing and /or proposed site features.The information illustrated is largely based on data provided by the client at the time of our study.ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. LEGEND Approximate Location of ESNW Test Pit,Proj.No. ES-7334,June 2020 Subject Site Existing Building TP-1 MRS KDH 03/09/2021 7334 2 TP-1 TP-2 TP-3 TP-4 TP-5 TP-6ABERDEEN AVENUE N.E.N .E. 1 5 T H S TR EE T 300 290 300 290292 294 296 298 302 304 306 292 294 296 298 302 304 306 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Drwn.MRS Checked KDH Date Mar.2021 Date 03/09/2021 Proj.No.7334 Plate 3 Earth Solutions NWLLCEarthSolutionsNWLLC EarthSolutions NW LLC Geotechnical Engineer ing,C onstr uction Observation/Testing and Environmental Services Retaining Wall Drainage Detail Vaughn Short Plat Renton,Washington NOTES: Free-draining Backfill should consist of soil having less than 5 percent fines. Percent passing No.4 sieve should be 25 to 75 percent. Sheet Drain may be feasible in lieu of Free-draining Backfill,per ESNW recommendations. Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1-inch Drain Rock. LEGEND: Free-draining Structural Backfill 1-inch Drain Rock 18"Min. Structural Fill Perforated Rigid Drain Pipe (Surround in Drain Rock) SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAWING DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Drwn.MRS Checked KDH Date Mar.2021 Date 03/09/2021 Proj.No.7334 Plate 4 Earth Solutions NWLLC Geotechnical Engineering,Construction Observation/Testing and Environmental Services EarthSolutionsNWLLC EarthSolutions NW LLC Footing Drain Detail Vaughn Short Plat Renton,Washington Slope Perforated Rigid Drain Pipe (Surround in Drain Rock) 18"Min. NOTES: Do NOT tie roof downspouts to Footing Drain. Surface Seal to consist of 12"of less permeable,suitable soil.Slope away from building. LEGEND: Surface Seal:native soil or other low-permeability material. 1-inch Drain Rock SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAW ING DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Earth Solutions NW, LLC Appendix A Subsurface Exploration Test Pit Logs ES-7334 Subsurface conditions on site were explored on June 4, 2020. Six test pits were excavated using a trackhoe and operator retained by our firm. The approximate locations of the test pits are illustrated on Plate 2 of this study. The test pit logs are provided in this Appendix. The test pits were advanced to a maximum depth of about 18.5 feet bgs. The final logs represent the interpretations of the field logs and the results of laboratory analyses. The stratification lines on the logs represent the approximate boundaries between soil types. In actuality, the transitions may be more gradual. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 GRAVEL AND GRAVELLY SOILS CLAYEY GRAVELS, GRAVEL - SAND - CLAY MIXTURES WELL-GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES POORLY-GRADED SANDS, GRAVELLY SAND, LITTLE OR NO FINES SILTY SANDS, SAND - SILT MIXTURES CLAYEY SANDS, SAND - CLAY MIXTURES INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SAND OR SILTY SOILS INORGANIC CLAYS OF HIGH PLASTICITY SILTS AND CLAYS MORE THAN 50% OF MATERIAL IS LARGER THAN NO. 200 SIEVE SIZE MORE THAN 50% OF MATERIAL IS SMALLER THAN NO. 200 SIEVE SIZE MORE THAN 50% OF COARSE FRACTION PASSING ON NO. 4 SIEVE MORE THAN 50% OF COARSE FRACTION RETAINED ON NO. 4 SIEVE SOIL CLASSIFICATION CHART (APPRECIABLE AMOUNT OF FINES) (APPRECIABLE AMOUNT OF FINES) (LITTLE OR NO FINES) FINE GRAINED SOILS SAND AND SANDY SOILS SILTS AND CLAYS ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS LETTERGRAPH SYMBOLSMAJOR DIVISIONS COARSE GRAINED SOILS TYPICAL DESCRIPTIONS WELL-GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES POORLY-GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES SILTY GRAVELS, GRAVEL - SAND - SILT MIXTURES CLEAN GRAVELS GRAVELS WITH FINES CLEAN SANDS (LITTLE OR NO FINES) SANDS WITH FINES LIQUID LIMIT LESS THAN 50 LIQUID LIMIT GREATER THAN 50 HIGHLY ORGANIC SOILS DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT Earth Solutions NW LLC DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 292.5 290.5 275.5 MC = 9.5% Fines = 5.0% CEC = 5.6 meq/100g OC = 2.5% MC = 6.0% Fines = 3.1% MC = 4.7% MC = 4.6% MC = 4.9% Fines = 2.1% MC = 7.9% MC = 6.4% MC = 5.9% TPSL SP- SM SP 0.5 2.5 17.5 Dark brown TOPSOIL Brown poorly graded SAND with silt, medium dense, moist [USDA Classification: slightly gravelly SAND] Gray poorly graded SAND, medium dense, moist [USDA Classification: slightly gravelly SAND] -notably coarser [USDA Classification: slightly gravelly coarse SAND] Test pit terminated at 17.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. NOTES Depth of Topsoil & Sod 6": grass GROUND ELEVATION 293 ft LOGGED BY KTK EXCAVATION METHOD TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: CHECKED BY KDH DATE STARTED 6/4/20 COMPLETED 6/4/20 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0 5 10 15 PAGE 1 OF 1 TEST PIT NUMBER TP-1 PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GENERAL BH / TP / WELL - 7334.GPJ - GINT STD US.GDT - 3/16/21Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 290.5 287.5 272.5 MC = 12.3% CEC = 7.9 meq/100g OC = 3.4% MC = 6.6% Fines = 4.5% MC = 8.8% MC = 8.0% MC = 7.7% MC = 7.5% Fines = 3.5% MC = 6.1% TPSL SP- SM SP 0.5 3.5 18.5 Dark brown TOPSOIL, trace roots to 1.5', wire debris (Fill) Brown poorly graded SAND with silt, medium dense, moist to wet Gray poorly graded SAND, medium dense, moist [USDA Classification: slightly gravelly SAND] -notably coarser [USDA Classification: slightly gravelly SAND] Test pit terminated at 18.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. NOTES Depth of Topsoil & Sod 6": grass GROUND ELEVATION 291 ft LOGGED BY KTK EXCAVATION METHOD TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: CHECKED BY KDH DATE STARTED 6/4/20 COMPLETED 6/4/20 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0 5 10 15 PAGE 1 OF 1 TEST PIT NUMBER TP-2 PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GENERAL BH / TP / WELL - 7334.GPJ - GINT STD US.GDT - 3/16/21Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 290.5 288.0 280.5 MC = 7.5% CEC = 3.7 meq/100g OC = 1.4% MC = 16.5% MC = 13.0% Fines = 1.1% CEC = 2.8 meq/100g OC = 1.1% TPSL SP- SM SP 0.5 3.0 10.5 Dark brown TOPSOIL Brown poorly graded SAND with silt, medium dense, moist Gray poorly graded SAND, medium dense, moist -infiltration test -increased moisture content to BOH due to infiltration test -notably coarser [USDA Classification: slightly gravelly coarse SAND] Test pit terminated at 10.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. NOTES Depth of Topsoil & Sod 6": grass GROUND ELEVATION 291 ft LOGGED BY KTK EXCAVATION METHOD TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: CHECKED BY KDH DATE STARTED 6/4/20 COMPLETED 6/4/20 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0 5 10 PAGE 1 OF 1 TEST PIT NUMBER TP-3 PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GENERAL BH / TP / WELL - 7334.GPJ - GINT STD US.GDT - 3/16/21Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 302.5 298.5 293.5 MC = 12.0% CEC = 5.4 meq/100g OC = 2.5% MC = 22.2% MC = 20.9% TPSL SP- SM SM 0.5 4.5 9.5 Dark brown TOPSOIL Brown poorly graded SAND with silt, medium dense, moist to wet Brown silty SAND, medium dense, wet -light iron oxide staining -notably coarser -becomes gray Test pit terminated at 9.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. NOTES Depth of Topsoil & Sod 6": grass GROUND ELEVATION 303 ft LOGGED BY KTK EXCAVATION METHOD TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: CHECKED BY KDH DATE STARTED 6/4/20 COMPLETED 6/4/20 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0 5 PAGE 1 OF 1 TEST PIT NUMBER TP-4 PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GENERAL BH / TP / WELL - 7334.GPJ - GINT STD US.GDT - 3/16/21Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 297.5 294.0 289.0 MC = 11.5% Fines = 10.4% CEC = 5.1 meq/100g OC = 2.0% MC = 8.8% MC = 6.6% TPSL SP- SM SP 0.5 4.0 9.0 Dark brown TOPSOIL Brown poorly graded SAND with silt, medium dense, moist to wet [USDA Classification: slightly gravelly SAND] Gray poorly graded SAND, medium dense, moist Test pit terminated at 9.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. NOTES Depth of Topsoil & Sod 6": grass GROUND ELEVATION 298 ft LOGGED BY KTK EXCAVATION METHOD TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: CHECKED BY KDH DATE STARTED 6/4/20 COMPLETED 6/4/20 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0 5 PAGE 1 OF 1 TEST PIT NUMBER TP-5 PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GENERAL BH / TP / WELL - 7334.GPJ - GINT STD US.GDT - 3/16/21Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 297.5 293.0 288.0 MC = 13.5% Fines = 14.7% CEC = 8.1 meq/100g OC = 3.8% MC = 5.9% MC = 5.2% TPSL SM SP 0.5 5.0 10.0 Dark brown TOPSOIL Brown silty SAND, medium dense, moist to wet [USDA Classification: slightly gravelly SAND] Gray poorly graded SAND, medium dense, moist Test pit terminated at 10.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. NOTES Depth of Topsoil & Sod 6": grass GROUND ELEVATION 298 ft LOGGED BY KTK EXCAVATION METHOD TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: CHECKED BY KDH DATE STARTED 6/4/20 COMPLETED 6/4/20 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0 5 10 PAGE 1 OF 1 TEST PIT NUMBER TP-6 PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GENERAL BH / TP / WELL - 7334.GPJ - GINT STD US.GDT - 3/16/21Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Earth Solutions NW, LLC Appendix B Laboratory Test Results ES-7334 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 0.0010.010.1110100 3 D100 140 Specimen Identification 1 fine 6 HYDROMETER 304 5.0 3.1 2.1 4.5 3.5 101/2 COBBLES Specimen Identification 4 coarse 20 401.5 8 14 USDA: Brown Slightly Gravelly Sand. USCS: SP-SM. USDA: Gray Slightly Gravelly Sand. USCS: SP. USDA: Gray Slightly Gravelly Coarse Sand. USCS: SP. USDA: Gray Slightly Gravelly Sand. USCS: SP. USDA: Gray Slightly Gravelly Sand. USCS: SP. 6 60 PERCENT FINER BY WEIGHTD10 0.263 0.29 0.491 0.234 0.34 0.399 0.422 0.913 0.366 0.568 GRAIN SIZE DISTRIBUTION 100 2.77 2.38 3.29 2.92 2.69 LL TP-01 TP-01 TP-01 TP-02 TP-02 0.144 0.177 0.278 0.125 0.211 3/4 U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS GRAVEL SAND 9.5 9.5 9.5 4.75 9.5 %Silt 1.20 1.13 0.95 1.19 0.96 TP-01 TP-01 TP-01 TP-02 TP-02 2 2003 Cc CuClassification %Clay 16 PID60 D30 coarse SILT OR CLAYfinemedium GRAIN SIZE IN MILLIMETERS 3/8 50 2.0ft. 4.0ft. 12.0ft. 5.0ft. 16.0ft. 2.00ft. 4.00ft. 12.00ft. 5.00ft. 16.00ft. PL PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GRAIN SIZE USDA ES-7334 VAUGHN SP.GPJ GINT US LAB.GDT 10/22/20Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 0.0010.010.1110100 3 D100 140 Specimen Identification 1 fine 6 HYDROMETER 304 1.1 10.4 14.7 101/2 COBBLES Specimen Identification 4 coarse 20 401.5 8 14 USDA: Gray Slightly Gravelly Coarse Sand. USCS: SP. USDA: Brown Slightly Gravelly Sand. USCS: SP-SM. USDA: Brown Slightly Gravelly Sand. USCS: SM. 6 60 PERCENT FINER BY WEIGHTD10 0.45 0.165 0.166 0.846 0.278 0.314 GRAIN SIZE DISTRIBUTION 100 3.03 3.78 LL TP-03 TP-05 TP-06 0.279 3/4 U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS GRAVEL SAND 9.5 4.75 9.5 %Silt 0.86 1.33 TP-03 TP-05 TP-06 2 2003 Cc CuClassification %Clay 16 PID60 D30 coarse SILT OR CLAYfinemedium GRAIN SIZE IN MILLIMETERS 3/8 50 10.5ft. 3.0ft. 2.5ft. 10.50ft. 3.00ft. 2.50ft. PL PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GRAIN SIZE USDA ES-7334 VAUGHN SP.GPJ GINT US LAB.GDT 10/22/20Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Am Test Inc. 13600 NE 126TH PL Suite C Kirkland, WA 98034 (425) 885-1664 www.amtestlab.com Professional Analytical Services ANALYSIS REPORT EARTH SOLUTIONS NW Date Received: 10/19/20 15365 NE 90TH ST Date Reported: 10/27/20 REDMOND, WA 98052 Attention: KEVEN HOFFMANN Project Name: VAUGHN SP Project #: ES-7334 All results reported on an as received basis. _________________________________________________________________________________________________ AMTEST Identification Number 20-A017147 Client Identification TP 01, 2' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 5.6 meq/100g 0.5 SW-846 9081 JDR 10/27/20 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 2.5 %SM 2540G DM 10/23/20 _________________________________________________________________________________________________ AMTEST Identification Number 20-A017148 Client Identification TP 02, 2' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 7.9 meq/100g 0.5 SW-846 9081 JDR 10/27/20 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 EARTH SOLUTIONS NW Project Name: VAUGHN SP AmTest ID: 20-A017148 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 3.4 %SM 2540G DM 10/23/20 _________________________________________________________________________________________________ AMTEST Identification Number 20-A017149 Client Identification TP 03, 5' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 3.7 meq/100g 0.5 SW-846 9081 JDR 10/27/20 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 1.4 %SM 2540G DM 10/23/20 _________________________________________________________________________________________________ AMTEST Identification Number 20-A017150 Client Identification TP 03, 10.5' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 2.8 meq/100g 0.5 SW-846 9081 JDR 10/27/20 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 1.1 %SM 2540G DM 10/23/20 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 EARTH SOLUTIONS NW Project Name: VAUGHN SP AmTest ID: 20-A017151 _________________________________________________________________________________________________ AMTEST Identification Number 20-A017151 Client Identification TP 04, 2.5' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 5.4 meq/100g 0.5 SW-846 9081 JDR 10/27/20 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 2.5 %SM 2540G DM 10/23/20 _________________________________________________________________________________________________ AMTEST Identification Number 20-A017152 Client Identification TP 05, 3' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 5.1 meq/100g 0.5 SW-846 9081 JDR 10/27/20 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 2.0 %SM 2540G DM 10/23/20 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 EARTH SOLUTIONS NW Project Name: VAUGHN SP AmTest ID: 20-A017153 _________________________________________________________________________________________________ AMTEST Identification Number 20-A017153 Client Identification TP 06, 2.5' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 8.1 meq/100g 0.5 SW-846 9081 JDR 10/27/20 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 3.8 %SM 2540G DM 10/23/20 _________________________________ Kathy Fugiel President DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Earth Solutions NW, LLC Report Distribution ES-7334 EMAIL ONLY MainVue WA, LLC 1110 – 112th Avenue Northeast, Suite 202 Bellevue, Washington 98004 Attention: Ms. Lisa Cavell EMAIL ONLY Barghausen Consulting Engineers, Inc. 18215 – 72nd Avenue South Kent, Washington 98032 Attention: Mr. Barry Talkington, P.E. Mr. Tom Barghausen, P.E. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Tab 7.0 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 7.0 OTHER PERMITS All permits required will be provided during final engineering. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Tab 8.0 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 8.0 ESC ANALYSIS AND DESIGN An erosion and sediment control plan will be provided during final engineering. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Tab 9.0 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 9.0 BOND QUANTITIES AND FACILITY SUMMARIES This section will be completed during final engineering. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Tab 10.0 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 21348-TIR.docx 10.0 OPERATIONS AND MAINTENANCE MANUAL An Operations and Maintenance Manual will be provided during final engineering. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56