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RS_TIR_Woo_Developments_LLC_190719_v1
Western Washington Division Eastern Washington Division 165 NE Juniper St., Ste 201, Issaquah, WA 98027 108 East 2nd Street, Cle Elum, WA 98922 Phone: (425) 392-0250 Fax: (425) 391-3055 Phone: (509) 674-7433 Fax: (509) 674-7419 www.EncompassES.net PRELIMINARY TECHNICAL INFORMATION REPORT City of Renton For Jefferson Highlands Unit Lot Subdivision 1526 Jefferson Ave NE Renton, WA 98056 May 17, 2019 5/17/19 Prepared By: Noah Anderson Encompass Engineering Job No. 17735 Prepared For: Anita Woo 12906 NE 25th Place Bellevue, WA 98005 Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page i Table of Contents I. PROJECT OVERVIEW ................................................................................................................ 1 II. CONDITIONS AND REQUIREMENTS SUMMARY ...................................................................... 5 III. OFF-SITE ANALYSIS .................................................................................................................. 8 IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ........................... 12 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN ..................................................................... 14 VI. SPECIAL REPORTS AND STUDIES ............................................................................................ 14 VII. OTHER PERMITS ..................................................................................................................... 14 VIII. CSWPPP ANALYSIS AND DESIGN............................................................................................ 15 IX. BOND QUANTITIES AND DECLARATION OF COVENANT ....................................................... 15 X. OPERATION AND MAINTENANCE MANUAL .......................................................................... 15 List of Figures 1. Vicinity Map 2. Soils Map and Legend 3. Existing Conditions Map 4. Developed Conditions Map 5. Flow Control Applications Map 6. Aquifer Protection Zone Map 7. Downstream Map 8. Flow Frequency Return Periods 9. Biopod Details Appendix A Geotechnical Engineering Report by The Riley Group, Inc. dated April 6, 2018 Appendix B WWHM2012 Output Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 1 I. PROJECT OVERVIEW Project: Jefferson Highlands Tax Parcel #: 722780-1560/722780-1485 Site Address: 1526 Jefferson Avenue NE/1513 Kirkland Avenue NE, Renton WA 98056 (See Figure 1: Vicinity Map) Site Area: The combined tax parcel area is 0.79 Acres Site Location: Renton Highlands # 2 Correct Plat Figure 1: Vicinity Map This project involves platting two parcels totaling 0.79 acres into 13 lots. The site is zoned R-14. Existing Site Conditions: The site is currently developed with two existing duplex residences, detached garage, out buildings and an asphalt driveway. The site is vegetated with grass, trees, and shrubs. The site slopes down southeast and southwest towards the center of the site at about 2% to 5%. Critical Areas: The parcel contains no critical areas or critical area buffers. Soils: Per the US Department of Agriculture (USDA), Natural Resources Conservation Service (NCRS) Web Soil Survey (WSS) information, the project site is generally underlain with Arents, Alderwood material (AmC), and Indianola loamy sand (InC). Per the Geotechnical Engineering Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 2 Report prepared by Riley Group, dated April 6, 2018, the site is underlain with some fill over native silty sand and sand with varying amounts of gravel, sand and silt. Dense glacial till was encountered at one area. A field infiltration test was performed with a calculated long term, design infiltration rate of 2.6 inches/hour. The Geotechnical Engineering Report is included in Appendix A of this TIR. Figure 2. Soils Map and Legend Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 5 Developed Site Conditions: The proposal incorporated the demolition, clearing, and grading of the project site to accommodate the construction of thirteen single-family residences. Fee simple homes will be constructed townhouse configurations. Alleys will be used to access the lots. The two fronting streets will be upgraded with new curb/gutters, sidewalks and planter strips. The project will be accessed via Jefferson Ave NE. A combination of full infiltration trenches and a Biopod system will provide the required stormwater controls for water quality and flow control. Th ese will overflow into the existing storm system in Kirkland Avenue NE. II. CONDITIONS AND REQUIREMENTS SUMMARY The 2017 City of Renton Surface Water Design Manual (CRSWDM) along with the 2016 King County Surface Water Design Manual (KCSWDM) was utilized for stormwater design per the City of Renton requirements. Core Requirements: Core Requirement #1: Discharge at the Natural Location The existing site drains to the existing, public storm system in Kirkland Avenue NE (in addition to infiltrating into the underlying soil). The project proposes to emulate the existing site drainage patterns. Core Requirement #2: Offsite Analysis A Level 1 Downstream analysis has been prepared and is included in Section III of this TIR. Core Requirement #3: Flow Control Facilities After applying the BMP credit for full infiltration per Table 1.2.9.A of the 2017 CRSWDM, the WWHM output displayed an increase in peak flow runoff of less than 0.15 CFS using 15-minute timesteps. Therefore, the project meets the exemption for Conservation Flow Control Areas per Section 1.2.3.1 of the 2017 CRSWDM and no further flow control facilities are required. See Section IV for full discussion of flow control facilities and Appendix A for full WWHM2012 Output. Core Requirement #4: Conveyance System Design and analysis of on and off-site conveyance systems will be submitted with final engineering. Core Requirement #5: Erosion and Sediment Control A temporary erosion and sediment control (TESC) plan will provide BMPs to be implemented during construction. This plan and included BMPs will be provided during final engineering. Core Requirement #6: Maintenance and Operations See Section X – Operation and Maintenance Manual, to be provided during final engineering. Core Requirement #7: Financial Guarantees and Liability The owner will arrange for any financial guarantees and liabilities required by the permit. Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 6 Core Requirement #8: Water Quality Facilities Because there will be greater than 5,000 sq-ft of new PGIS, water quality requirements are proposed to be met using an Oldcastle Biopod. This biofiltration device has been sized to provide enhanced water quality treatment for the site. This proprietary facility has been approved per an email from Jonathan Chavez, P.E. for the City of Renton. See Section IV of this TIR for full discussion of water quality facilit ies and Figure 9 for Biopod details. Core Requirement #9: Flow Control BMPs Per the Flow Control Application Map in the 2017 CRSWDM (Figure 5), this project site is within the “Peak Rate Flow Control Standard (Existing Site Conditions)” area. In this area, flow control facilities are required to be designed to match the existing conditions 2-, 10- , and 100-year peak-rate runoff from the site. This site is designed to comply with the Small Subdivision Project BMP Requirements detailed in Section 1.2.9.3.1 of the 2017 CRSWDM. Flow Control BMPs below were considered in order of preference as prescribed by the Small Subdivision Project BMP Requirements. See Section IV of this TIR for complete Flow Control details. Figure 5: Flow Control Application Map Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 7 Full Dispersion: Infeasible; site design does not allow for minimum native vegetated flowpath lengths per Appendix C.2.1. Full Infiltration: Feasible; per Geotech report. • Full infiltration of the 11,058 SF of rooftop areas is proposed for the site in the form of Gravel Filled Trenches per Appendix C.2.2.3. Limited Infiltration: Feasible; per Geotech report. Full Infiltration is proposed to achieve onsite flow control. Bioretention: Feasible; per Geotech report. • Bioretention is proposed for off-site flow control in the form of bioretention cells per Appendix C.2.6 along Jefferson Avenue NE and Kirkland Avenue NE. Bioretention cells will be designed with final engineering. Soil Amendment: Feasible; retention of existing soils and restoration of disturbed soils shall be applied to the landscaped areas of the site. Special Requirement #1: Other Adopted Area-Specific Requirements Master Drainage Plan – N/A Basin Plan – N/A Salmon Conservation Plan – N/A Lake Management Plan – N/A Hazard Mitigation Plan – N/A Shared Facility Drainage Plan – N/A Special Requirement #2: Flood Hazard Area Delineation The limits of this project do not lie in the FEMA 100-year floodplain. Special Requirement #3: Flood Protection Facilities This special requirement is for Class 1 or 2 streams with an existing flood protection facility. The site does not contain any streams and is therefore not applicable. Special Requirement #4: Source controls Source control is not required for this project. Special Requirement #5: Oil Control This project is not considered high-use in need of oil control. Special Requirement #6: Aquifer Protection Area This site is located in Zone 2 of the Aquifer Protection Area per COR GIS Maps (Figure 6). This project therefore is designed to comply with the re quirements detailed in Section 1.3.6 of the 2017 CRSWDM. Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 8 Figure 6: Aquifer Protection Zone Map III. OFF-SITE ANALYSIS A Level 1 Downstream Analysis was performed by Encompass Engineering and Surveying on Monday March 12, 2018. The analysis was performed at approximately 8:00 AM with a temperature of about 55°. The project site is comprised of two adjacent tax parcels. Both parcels are currently developed with single-family residences with attached garages. The majority of the site is cleared lawn with small patches of trees on each site. The site is contained within a single drainage basin. Slopes range from 5-15% across the site. The site is divided by a low point that runs through center of the overall project site. The Eastern parcel is also divided by a high point that runs through the center. Runoff from the Eastern quarter of the project site sheet flows towards Kirkland Ave NE. It then runs South along the existing curb to a CB approximately 200’ downstream of the project site. Runoff from the remaining portion of the site sheet flows to the center of the site. It then flows to the Southeast approximately 370’ before reaching Kirkland Ave NE and sheet flowing South to the nearest CB. This is where the runoff from the two areas converge and continue South. The Kirkland Ave NE drainage system is comprised of 12” Concrete stormwater main with 8” concrete connection pipes to CBs on either side of the road. Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 9 Approximately 1,100’ downstream of the project site, the Kirkland Ave NE drainage system converges with NE 12th St drainage system flowing West. This system is comprised of 36” CMP. This is where the downstream analysis was completed. Based on this exploration no downstream problems exist or will arise with the proposed construction. From the City of Renton COR Mapping we can see that this system continues to East and Southeast approximately 6,500’ before outfalling to a stormwater wetland/pond Facility ID NO. 111416 near the Boing 737 Plant. See Figure 7: Downstream Map and photos on the following pages for more information. King County iMap and City of Renton GIS Maps show no drainage complaints relevant to the project. Figure 7: Downstream Map Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 10 Existing Residence on Eastern Parcel Kirkland Ave NE and Existing Access (Taken Facing South) Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 11 Existing Residence and Backyard on West Parcel Jefferson Ave NE (Taken Facing South) Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 12 Intersection of Kirkland Ave NE and NE 12th Std IV. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Flow Control Design: Per the Flow Control Application Map in the 2017 City of Renton Surface Water Design Manual, this project site is within the “Peak Rate Flow Control Standard (Existing Site Conditions)” area. In this area, flow control facilities are required to match the existing conditions 2-, 10-, and 100- year peak-rate runoff from the site. This site is designed to comply with the Small Subdivision Project BMP Requirements detailed in Section 1.2.9.3.1 of the 2017 CRSWDM. All stormwater runoff flows will be discharged to the natural location or locations identified in the Offsite Analysis. Basin areas are listed in the table below and full WWHM outputs are attached in Appendix B. Impervious areas fully infiltrated (Rooftops) are subtracted from the WWHM model per Table 1.2.9.A of the 2017 CRSWDM. The Soil Amendment BMP shall be implemented for onsite vegetated areas per Appendix C.2.13 of the 2017 CRSWDM. Areas meeting this criterion are modeled as “pasture” rather than “lawn” for WWHM modeling. Refer to Figures 3 and 4 for Existing and Developed Conditions Map. Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 13 Area Breakdown Existing Proposed Condition Measured (AC) Measured (AC) Modeled (AC) Pasture: 0.000 0.297 0.297 Lawn: 0.604 0.000 0.000 Roof: 0.099 0.254 0.000 Paved: 0.086 0.238 0.238 Total Developed: 0.185 0.492 0.492 Total Area: 0.788 0.788 0.535 Table 1: Area Breakdown Full Infiltration of 11,058 SF (0.254 AC) of rooftop area is proposed for the site in the form of Gravel Filled Trenches for Full Infiltration per Appendix C.2.2.3. Per the Geotech report, the site is underlain with silty sand and requires a 20-foot-long section per 1,000 SF of rooftop area infiltrated. A total of 222-feet of trenching is required to fully infiltrate the tributary area. Two 2-foot-wide, 80-foot-long trenches and one 2-foot-wide, 75-foot-long trench are proposed for a total of 235-feet of trenching. The infiltration trenches are designed with 6” emergency overflows connecting to the proposed Biopod and the further storm drain system. This project is designed to comply with the Zone 2 Aquifer Protection Area requirements detailed in Section 1.3.6 of the 2017 CRSWDM. Per the Grain Size Analysis of the Geotech report included in Appendix A, the site does not meet the “soil properties required within groundwater protection areas” detailed in Section 5.2.1 of the 2017 CRSWDM. Therefore, the infiltration facilities are designed to meet the “Inside Groundwater Protections Areas” criteria detailed in Section 6.2.4. Infiltration trenches shall utilize an organic soil layer per Section 6.2.4.2 to comply with these requirements. Figure 8: Flow Frequency Return Periods Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 14 The proposed project shows a peak flow increase of less than 0.15 CFS and therefore meets the Flow Control exemption detailed in Section 1.2.3 of the 2017 CRSWDM. The use of further flow control BMPs is not required. Water Quality Design: Stormwater runoff from the driveway and walkway areas will be treated for Enhanced Water quality per the 2017 CRSWDM. A Biopod manufactured by Oldcastle Infrastructure will provide the required treatment. This design has been approved per an email from Jonathan Chavez, P.E. for the City of Renton. See Figure 9 below for structure details. Figure 9: Biopod Detail V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN Conveyance system analysis and design will be provided with final engineering. VI. SPECIAL REPORTS AND STUDIES Geotechnical Engineering Report prepared by Riley Group, dated April 6, 2018— See Appendix A VII. OTHER PERMITS Building Permits will be required. Jefferson Highlands Preliminary Technical Information Report 5/17/19 Page 15 VIII. CSWPPP ANALYSIS AND DESIGN CSWPPP Analysis and Design will be provided with final engineering. IX. BOND QUANTITIES and DECLARATION of COVENANT Bond Quantities and Declaration of Covenant will be provided with final engineering . X. OPERATION AND MAINTENANCE MANUAL An Operation and Maintenance Manual will be provided with final engineering. Jefferson Highlands Preliminary Technical Information Report 5/17/19 Appendix A Geotechnical Engineering Report prepared by Riley Group, dated April 6, 2018 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone 425.415.0551 ♦ Fax 425.415.0311 www.riley-group.com GEOTECHNICAL ENGINEERING REPORT PREPARED BY: THE RILEY GROUP, INC. 17522 BOTHELL WAY NORTHEAST BOTHELL, WASHINGTON 98011 PREPARED FOR: ANITA WOO 12906 NORTHEAST 25TH PLACE BELLEVUE, WASHINGTON 98004 RGI PROJECT NO. 2018-070 JEFFERSON AND KIRKLAND TOWNHOMES 1513 KIRKLAND AVENUE NORTHEAST AND 1526 JEFFERSON AVENUE NORTHEAST RENTON, WASHINGTON APRIL 6, 2018 Geotechnical Engineering Report i April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 TABLE OF CONTENTS 1.0 INTRODUCTION ............................................................................................................................... 1 2.0 PROJECT DESCRIPTION ............................................................................................................... 1 3.0 FIELD EXPLORATION AND LABORATORY TESTING .......................................................... 2 3.1 FIELD EXPLORATION ................................................................................................................................... 2 3.2 LABORATORY TESTING ................................................................................................................................ 2 4.0 SITE CONDITIONS ........................................................................................................................... 2 4.1 SURFACE .................................................................................................................................................. 2 4.2 GEOLOGY ................................................................................................................................................. 3 4.3 SOILS ....................................................................................................................................................... 3 4.4 GROUNDWATER ........................................................................................................................................ 3 4.5 SEISMIC CONSIDERATIONS ........................................................................................................................... 4 4.6 GEOLOGIC HAZARD AREAS .......................................................................................................................... 4 5.0 DISCUSSION AND RECOMMENDATIONS ................................................................................. 5 5.1 GEOTECHNICAL CONSIDERATIONS ................................................................................................................. 5 5.2 EARTHWORK ............................................................................................................................................. 5 5.2.1 Erosion and Sediment Control ..................................................................................................... 5 5.2.2 Stripping and Subgrade Preparation ............................................................................................ 6 5.2.3 Excavations................................................................................................................................... 6 5.2.4 Structural Fill ................................................................................................................................ 7 5.2.5 Wet Weather Construction Considerations ................................................................................. 8 5.3 FOUNDATIONS .......................................................................................................................................... 9 5.4 RETAINING WALLS ................................................................................................................................... 10 5.5 SLAB-ON-GRADE CONSTRUCTION ............................................................................................................... 10 5.6 DRAINAGE .............................................................................................................................................. 11 5.6.1 Surface ....................................................................................................................................... 11 5.6.2 Subsurface .................................................................................................................................. 11 5.6.3 Infiltration .................................................................................................................................. 11 5.7 UTILITIES ................................................................................................................................................ 12 6.0 ADDITIONAL SERVICES .............................................................................................................. 12 7.0 LIMITATIONS ................................................................................................................................. 12 LIST OF FIGURES AND APPENDICES Figure 1 ..................................................................................................................... Site Vicinity Map Figure 2 ............................................................................................... Geotechnical Exploration Plan Figure 3 ............................................................................................... Retaining Wall Drainage Detail Figure 4 ....................................................................................................Typical Footing Drain Detail Appendix A .......................................................................... Field Exploration and Laboratory Testing Geotechnical Engineering Report ii April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 Executive Summary This Executive Summary should be used in conjunction with the entire Geotechnical Engineering Report (GER) for design and/or construction purposes. It should be recognized that specific details were not included or fully developed in this section, and the GER must be read in its entirety for a comprehensive understanding of the items contained herein. Section 7.0 should be read for an understanding of limitations. RGI’s geotechnical scope of work included the advancement of five test pits to approximate depths of 5 to 9.5 feet below existing site grades. Based on the information obtained from our subsurface exploration, the site is suitable for development of the proposed project. The following geotechnical considerations were identified: Soil Conditions: The soils encountered during field exploration include loose to medium dense fill comprised of silty sand with trace gravel and sand with some silt and trace gravel over native deposits of loose to dense silty sand with varying amounts of gravel, sand with varying amounts of silt and gravel and gravel with varying amounts of sand and silt. Very dense glacial till comprised of silty sand with some gravel was encountered at one location. Groundwater: No groundwater seepage was encountered during our subsurface exploration. Foundations: Foundations for the proposed building may be supported on conventional spread footings bearing on medium dense to dense native soil or structural fill. Slab-on-grade: Slab-on-grade floors and slabs for the proposed building can be supported on medium dense to dense native soil or structural fill. Geotechnical Engineering Report 1 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 1.0 Introduction This Geotechnical Engineering Report (GER) presents the results of the geotechnical engineering services provided for the Jefferson and Kirkland Townhomes in Renton, Washington. The purpose of this evaluation is to assess subsurface conditions and provide geotechnical recommendations for the construction of 11 townhomes. Our scope of services included field explorations, laboratory testing, engineering analyses, and preparation of this GER. The recommendations in the following sections of this GER are based upon our current understanding of the proposed site development as outlined below. If actual features vary or changes are made, RGI should review them in order to modify our recommendations as required. In addition, RGI requests to review the site grading plan, final design drawings and specifications when available to verify that our project understanding is correct and that our recommendations have been properly interpreted and incorporated into the project design and construction. 2.0 Project description The project site is located at 1513 Kirkland Avenue Northeast and 1526 Jefferson Avenue Northeast in Renton, Washington. The approximate location of the site is shown on Figure 1. The site is currently occupied by two multi-family homes, one adjacent to Jefferson Avenue Northeast and one adjacent to Kirkland Avenue Northeast. Several outbuildings also occupy the site. RGI understands that 11 townhomes will be constructed at the site. Based on review of a proposed site layout prepared by Daniel Umbach Architect, 6 units will be located along Jefferson Avenue Northeast, and 5 units along Kirkland Avenue Northeast. Vehicle access will be via a paved driveway extending west from Kirkland Avenue Northeast in the southeast site corner, with garages in the lower level of each unit. RGI understands the central portion of the site is being considered for infiltration of stormwater. At the time of preparing this GER, building plans were not available for our review. Based on our experience with similar construction, RGI anticipates that the proposed building will be supported on perimeter walls with bearing loads of two to six kips per linear foot, and a series of columns with a maximum load up to 30 kips. Slab-on-grade floor loading of 250 pounds per square foot (psf) are expected. Geotechnical Engineering Report 2 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 3.0 Field Exploration and Laboratory Testing 3.1 FIELD EXPLORATION On March 30, 2018, RGI observed the excavation of five test pits and completed one infiltration test. The approximate exploration locations are shown on Figure 2. Field logs of each exploration were prepared by the geologist that continuously observed the excavation. These logs included visual classifications of the materials encountered during excavation as well as our interpretation of the subsurface conditions between samples. The test pits logs included in Appendix A represent an interpretation of the field logs and include modifications based on laboratory observation and analysis of the samples. 3.2 LABORATORY TESTING During the field exploration, a representative portion of each recovered sample was sealed in containers and transported to our laboratory for further visual and laboratory examination. Selected samples retrieved from the test pits were tested for moisture content and grain size analysis to aid in soil classification and provide input for the recommendations provided in this GER. The results and descriptions of the laboratory tests are enclosed in Appendix A. 4.0 Site Conditions 4.1 SURFACE The subject site is comprised of two rectangular-shaped parcels of land totaling approximately 0.77 acres in size. The site is bound to the north and south by residential properties, to the east by Kirkland Avenue Northeast, and to the west by Jefferson Avenue Northeast. The existing site is occupied by two multi-family homes and several outbuildings. A concrete slab that appears to be from a garage is located in the northeast site corner. Several small brick walls and numerous fences divide the property into four yard areas. The site is relatively flat with about five feet of elevation change across the site. The site slopes down from the streets along the east and west perimeter to a topographic low extending in a north-south direction through the central portion of the property, which has a slight slope toward the south. The site is vegetated primarily with grass, with numerous decorative plants, shrubs, and fruit trees scattered about the property. A large- diameter cedar tree is located in the south-central portion of the property. Geotechnical Engineering Report 3 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 4.2 GEOLOGY Review of the Preliminary Geologic Map of Seattle and Vicinity, Washington, by Howard H. Waldron, etc. (1962) indicates that the soil in the project vicinity is mapped as Vashon till (Qt), which is light to dark gray, nonsorted, nonstratified mixture of clay, silt, sand, and gravel. Till was encountered at a depth of 9 feet in TP-1, and likely underlies the entire property. The sand and gravel soils encountered above the till throughout the site match the descriptions for Younger Sand (Qys) and Younger Gravel (Qyg) mapped to the west and northwest of the site. 4.3 SOILS The soils encountered during field exploration include loose to medium dense fill comprised of silty sand with trace gravel and sand with some silt and trace gravel over native deposits of loose to dense silty sand with varying amounts of gravel, sand with varying amounts of silt and gravel and gravel with varying amounts of sand and silt. Very dense glacial till comprised of silty sand with some gravel was encountered at one location. More detailed descriptions of the subsurface conditions encountered are presented in the test pits included in Appendix A. Sieve analysis was performed on seven selected soil samples. Grain size distribution curves are included in Appendix A. 4.4 GROUNDWATER No groundwater seepage was encountered during our subsurface exploration. Iron oxide staining was observed that may be indicative of seasonal groundwater travelling through subsurface soils. It should be recognized that fluctuations of the groundwater table will occur due to seasonal variations in the amount of rainfall, runoff, and other factors not evident at the time the explorations were performed. In addition, perched water can develop within seams and layers contained in fill soils or higher permeability soils overlying less permeable soils following periods of heavy or prolonged precipitation. Therefore, groundwater levels during construction or at other times in the future may be higher or lower than the levels indicated on the logs. Groundwater level fluctuations should be considered when developing the design and construction plans for the project. Geotechnical Engineering Report 4 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 4.5 SEISMIC CONSIDERATIONS Based on the 2012/2015 International Building Code (IBC), RGI recommends the follow seismic parameters for design. Table 1 2012/2015 IBC Parameter Value Site Soil Class1 D2 Site Latitude 47.50635oN Site Longitude 122.17967oW Short Period Spectral Response Acceleration, SS (g) 1.426 1-Second Period Spectral Response Acceleration, S1 (g) 0.537 Adjusted Short Period Spectral Response Acceleration, SMS (g) 1.426 Adjusted 1-Second Period Spectral Response Acceleration, SM1 (g) 0.806 1. Note: In general accordance with Chapter 20 of ASCE 7-10. The Site Class is based on the average characteristics of the upper 100 feet of the subsurface profile. 2. Note: The 2012/2015 IBC and ASCE 7-10 require a site soil profile determination extending to a depth of 100 feet for seismic site classification. The current scope of our services does not include the required 100 foot soil profile determination. Test pits extended to a maximum depth of 9.5 feet, and this seismic site class definition considers that similar soil continues below the maximum depth of the subsurface exploration. Additional exploration to deeper depths would be required to confirm the conditions below the current depth of exploration. Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in water pressure induced by vibrations from a seismic event. Liquefaction mainly affects geologically recent deposits of fine-grained sands that are below the groundwater table. Soils of this nature derive their strength from intergranular friction. The generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular friction, thus reducing or eliminating the soil’s strength. RGI reviewed the results of the field and laboratory testing and assessed the potential for liquefaction of the site’s soil during an earthquake. Since the site is underlain by glacial till and depth and lacks a shallow groundwater table, RGI considers that the possibility of liquefaction during an earthquake is minimal. 4.6 GEOLOGIC HAZARD AREAS Regulated geologically hazardous areas include erosion, landslide, earthquake, or other geological hazards. Based on the definition in the Renton Municipal Code, the site does not contain geologically hazardous areas. Geotechnical Engineering Report 5 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 5.0 Discussion and Recommendations 5.1 GEOTECHNICAL CONSIDERATIONS Based on our study, the site is suitable for the proposed construction from a geotechnical standpoint. Foundations for the proposed building can be supported on conventional spread footings bearing on medium dense to dense native soil or structural fill. Slab-on- grade floors can be similarly supported. Detailed recommendations regarding the above issues and other geotechnical design considerations are provided in the following sections. These recommendations should be incorporated into the final design drawings and construction specifications. 5.2 EARTHWORK The earthwork is expected to include excavating and backfilling the building foundations and preparing slab subgrades. 5.2.1 EROSION AND SEDIMENT CONTROL Potential sources or causes of erosion and sedimentation depend on construction methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type, construction sequencing and weather. The impacts on erosion-prone areas can be reduced by implementing an erosion and sedimentation control plan. The plan should be designed in accordance with applicable city and/or county standards. RGI recommends the following erosion control Best Management Practices (BMPs): Scheduling site preparation and grading for the drier summer and early fall months and undertaking activities that expose soil during periods of little or no rainfall Retaining existing vegetation whenever feasible Establishing a quarry spall construction entrance Installing siltation control fencing or anchored straw or coir wattles on the downhill side of work areas Covering soil stockpiles with anchored plastic sheeting Revegetating or mulching exposed soils with a minimum 3-inch thickness of straw if surfaces will be left undisturbed for more than one day during wet weather or one week in dry weather Directing runoff away from exposed soils and slopes Minimizing the length and steepness of slopes with exposed soils and cover excavation surfaces with anchored plastic sheeting Decreasing runoff velocities with check dams, straw bales or coir wattles Confining sediment to the project site Geotechnical Engineering Report 6 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 Inspecting and maintaining erosion and sediment control measures frequently (The contractor should be aware that inspection and maintenance of erosion control BMPs is critical toward their satisfactory performance. Repair and/or replacement of dysfunctional erosion control elements should be anticipated.) Permanent erosion protection should be provided by reestablishing vegetation using hydroseeding and/or landscape planting. Until the permanent erosion protection is established, site monitoring should be performed by qualified personnel to evaluate the effectiveness of the erosion control measures. Provisions for modifications to the erosion control system based on monitoring observations should be included in the erosion and sedimentation control plan. 5.2.2 STRIPPING AND SUBGRADE PREPARATION Stripping efforts should include removal of pavements, vegetation, organic materials, and deleterious debris from areas slated for building, pavement, and utility construction. The test pits encountered 6 to 16 inches of topsoil and rootmass. Deeper areas of stripping may be required in forested or heavily vegetated areas of the site. Subgrade soils that become disturbed due to elevated moisture conditions should be overexcavated to reveal firm, non-yielding, non-organic soils and backfilled with compacted structural fill. In order to maximize utilization of site soils as structural fill, RGI recommends that the earthwork portion of this project be completed during extended periods of warm and dry weather if possible. If earthwork is completed during the wet season (typically November through May) it will be necessary to take extra precautionary measures to protect subgrade soils. Wet season earthwork will require additional mitigative measures beyond that which would be expected during the drier summer and fall months. 5.2.3 EXCAVATIONS All temporary cut slopes associated with the site and utility excavations should be adequately inclined to prevent sloughing and collapse. The site soils consist of medium dense to dense silty sand with trace gravel and sand with some silt and trace gravel, with localized gravel beds. Accordingly, for excavations more than 4 feet but less than 20 feet in depth, the temporary side slopes should be laid back with a minimum slope inclination of 1H:1V (Horizontal:Vertical). If there is insufficient room to complete the excavations in this manner, or excavations greater than 20 feet in depth are planned, using temporary shoring to support the excavations should be considered. For open cuts at the site, RGI recommends: No traffic, construction equipment, stockpiles or building supplies are allowed at the top of cut slopes within a distance of at least five feet from the top of the cut Geotechnical Engineering Report 7 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 Exposed soil along the slope is protected from surface erosion using waterproof tarps and/or plastic sheeting Construction activities are scheduled so that the length of time the temporary cut is left open is minimized Surface water is diverted away from the excavation The general condition of slopes should be observed periodically by a geotechnical engineer to confirm adequate stability and erosion control measures In all cases, however, appropriate inclinations will depend on the actual soil and groundwater conditions encountered during earthwork. Ultimately, the site contractor must be responsible for maintaining safe excavation slopes that comply with applicable OSHA or WISHA guidelines. 5.2.4 STRUCTURAL FILL RGI recommends fill below the foundation and floor slab, behind retaining walls, and below pavement and hardscape surfaces be placed in accordance with the following recommendations for structural fill. The structural fill should be placed after completion of site preparation procedures as described above. The suitability of excavated site soils and import soils for compacted structural fill use will depend on the gradation and moisture content of the soil when it is placed. As the amount of fines (that portion passing the U.S. No. 200 sieve) increases, soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult or impossible to achieve. Soils containing more than about 5 percent fines cannot be consistently compacted to a dense, non-yielding condition when the moisture content is more than 2 percent above or below optimum. Optimum moisture content is that moisture that results in the greatest compacted dry density with a specified compactive effort. Non-organic site soils are only considered suitable for structural fill provided that their moisture content is within about two percent of the optimum moisture level as determined by ASTM D1557. Excavated site soils may not be suitable for re-use as structural fill depending on the moisture content and weather conditions at the time of construction. If soils are stockpiled for future reuse and wet weather is anticipated, the stockpile should be protected with plastic sheeting that is securely anchored. Even during dry weather, moisture conditioning (such as, windrowing and drying) of site soils to be reused as structural fill may be required. Some of the site soils are moisture sensitive and may require moisture conditioning prior to use as structural fill. If on-site soils are or become unusable, it may become necessary to import clean, granular soils to complete site work that meet the grading requirements listed in Table 2 to be used as structural fill. Geotechnical Engineering Report 8 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 Table 2 Structural Fill Gradation U.S. Sieve Size Percent Passing 4 inches 100 No. 4 sieve 22 to 100 No. 200 sieve 0 to 5* *Based on minus 3/4 inch fraction. Prior to use, an RGI representative should observe and test all materials imported to the site for use as structural fill. Structural fill materials should be placed in uniform loose layers not exceeding 12 inches and compacted as specified in Table 3. The soil’s maximum density and optimum moisture should be determined by ASTM D1557. Table 3 Structural Fill Compaction ASTM D1557 Location Material Type Minimum Compaction Percentage Moisture Content Range Foundations On-site granular or approved imported fill soils: 95 +2 -2 Retaining Wall Backfill On-site granular or approved imported fill soils: 92 +2 -2 Slab-on-grade On-site granular or approved imported fill soils: 95 +2 -2 General Fill (non- structural areas) On-site soils or approved imported fill soils: 90 +3 -2 Placement and compaction of structural fill should be observed by RGI. A representative number of in-place density tests should be performed as the fill is being placed to confirm that the recommended level of compaction is achieved. 5.2.5 WET WEATHER CONSTRUCTION CONSIDERATIONS RGI recommends that preparation for site grading and construction include procedures intended to drain ponded water, control surface water runoff, and to collect shallow subsurface seepage zones in excavations where encountered. It will not be possible to successfully compact the subgrade or utilize on-site soils as structural fill if accumulated water is not drained prior to grading or if drainage is not controlled during construction. Attempting to grade the site without adequate drainage control measures will reduce the amount of on-site soil effectively available for use, increase the amount of select import fill materials required, and ultimately increase the cost of the earthwork phases of the Geotechnical Engineering Report 9 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 project. Free water should not be allowed to pond on the subgrade soils. RGI anticipates that the use of berms and shallow drainage ditches, with sumps and pumps in utility trenches, will be required for surface water control during wet weather and/or wet site conditions. 5.3 FOUNDATIONS Following site preparation and grading, the proposed building foundation can be supported on conventional spread footings bearing on medium dense to dense native soil or structural fill. Loose, organic, or other unsuitable soils may be encountered in the proposed building footprint. If unsuitable soils are encountered, they should be overexcavated and backfilled with structural fill. If existing fill soils are encountered at subgrade elevations, the suitability of the soils for foundation support should be evaluated by a RGI representative. Perimeter foundations exposed to weather should be at a minimum depth of 18 inches below final exterior grades. Interior foundations can be constructed at any convenient depth below the floor slab. Finished grade is defined as the lowest adjacent grade within 5 feet of the foundation for perimeter (or exterior) footings and finished floor level for interior footings. Table 4 Foundation Design Design Parameter Value Allowable Bearing Capacity 2,000 psf1 Friction Coefficient 0.30 Passive pressure (equivalent fluid pressure) 250 pcf2 Minimum foundation dimensions Columns: 24 inches Walls: 16 inches 1. psf = pounds per square foot 2. pcf = pounds per cubic foot The allowable foundation bearing pressures apply to dead loads plus design live load conditions. For short-term loads, such as wind and seismic, a 1/3 increase in this allowable capacity may be used. At perimeter locations, RGI recommends not including the upper 12 inches of soil in the computation of passive pressures because they can be affected by weather or disturbed by future grading activity. The passive pressure value assumes the foundation will be constructed neat against competent soil or backfilled with structural fill as described in Section 5.2.4. The recommended base friction and passive resistance value includes a safety factor of about 1.5. Geotechnical Engineering Report 10 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 With spread footing foundations designed in accordance with the recommendations in this section, maximum total and differential post-construction settlements of 1 inch and 1/2 inch, respectively, should be expected. 5.4 RETAINING WALLS If retaining walls are needed in the building area or for a below grade vault, RGI recommends cast-in-place concrete walls be used. The magnitude of earth pressure development on retaining walls will partly depend on the quality of the wall backfill. RGI recommends placing and compacting wall backfill as structural fill. Wall drainage will be needed behind the wall face. A typical retaining wall drainage detail is shown in Figure 3. With wall backfill placed and compacted as recommended, and drainage properly installed, RGI recommends using the values in the following table for design. Table 5 Retaining Wall Design Design Parameter Value Allowable Bearing Capacity 2,000 psf Active Earth Pressure (unrestrained walls) 35 pcf At-rest Earth Pressure (restrained walls) 50 pcf For seismic design, an additional uniform load of 7 times the wall height (H) for unrestrained walls and 14H in psf for restrained walls should be applied to the wall surface. Friction at the base of foundations and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are provided in Section 5.3. 5.5 SLAB-ON-GRADE CONSTRUCTION Once site preparation has been completed as described in Section 5.2, suitable support for slab-on-grade construction should be provided. RGI recommends that the concrete slab be placed on top of medium dense native soil or structural fill. Immediately below the floor slab, RGI recommends placing a four-inch thick capillary break layer of clean, free-draining sand or gravel that has less than five percent passing the U.S. No. 200 sieve. This material will reduce the potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor slab. Where moisture by vapor transmission is undesirable, an 8- to 10-millimeter thick plastic membrane should be placed on a 4-inch thick layer of clean gravel. For the anticipated floor slab loading, we estimate post-construction floor settlements of 1/4- to 1/2-inch. Geotechnical Engineering Report 11 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 5.6 DRAINAGE 5.6.1 SURFACE Final exterior grades should promote free and positive drainage away from the building area. Water must not be allowed to pond or collect adjacent to foundations or within the immediate building area. For non-pavement locations, RGI recommends providing a minimum drainage gradient of 3 percent for a minimum distance of 10 feet from the building perimeter. In paved locations, a minimum gradient of 1 percent should be provided unless provisions are included for collection and disposal of surface water adjacent to the structure. 5.6.2 SUBSURFACE RGI recommends installing perimeter foundation drains. A typical footing drain detail is shown on Figure 4. The foundation drains and roof downspouts should be tightlined separately to an approved discharge facility. Subsurface drains must be laid with a gradient sufficient to promote positive flow to a controlled point of approved discharge. 5.6.3 INFILTRATION RGI understands that an infiltration system is being considered for the on-site disposal of stormwater run-off in the central portion of the property. A field infiltration test at test pit TP-2 was performed in general accordance with a Small-Scale Pilot Infiltration Test described in Reference 6A – Infiltration Rate Test Methods in the King County, Washington, Surface Water Design Manual. Table 6 Measured Infiltration Rates Test Location Test Depth Measured Rate (Inches per hour) Design Rate (Inches per hour) TP-2 4’ 6.5 2.6 King County Surface Water Design Manual correction factors were applied to the field measured rate of 6.5 inches per hour. No groundwater was encountered in the test pits. Very dense glacial till was encountered at 9 feet below grade in test pit, TP-1 and is a restrictive layer. Idesign = Imeasured x Ftesting x Fplugging x Fgeometry Correction factors of 0.5 (Ftesting) for the PIT test method and 0.8 (Fplugging) for fine sands were applied to the field measured rate to estimate the long-term design infiltration rate. We assumed Fgeometry = 1. The application of the correction factors yield a long-term design rate (Idesign) of 2.6 inches per hour. Geotechnical Engineering Report 12 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 5.7 UTILITIES Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) specifications. For site utilities located within the right-of-ways, bedding and backfill should be completed in accordance with City of Renton specifications. At a minimum, trench backfill should be placed and compacted as structural fill, as described in Section 5.2.4. Where utilities occur below unimproved areas, the degree of compaction can be reduced to a minimum of 90 percent of the soil’s maximum density as determined by the referenced ASTM D1557. 6.0 Additional Services RGI is available to provide further geotechnical consultation throughout the design phase of the project. RGI should review the final design and specifications in order to verify that earthwork and foundation recommendations have been properly interpreted and incorporated into project design and construction. RGI is also available to provide geotechnical engineering and construction monitoring services during construction. The integrity of the earthwork and construction depends on proper site preparation and procedures. In addition, engineering decisions may arise in the field in the event that variations in subsurface conditions become apparent. Construction monitoring services are not part of this scope of work. If these services are desired, please let us know and we will prepare a cost proposal. 7.0 Limitations This GER is the property of RGI, Anita Woo, and her designated agents. Within the limits of the scope and budget, this GER was prepared in accordance with generally accepted geotechnical engineering practices in the area at the time this GER was issued. This GER is intended for specific application to the Jefferson and Kirkland Townhomes project in Renton, Washington, and for the exclusive use of Anita Woo and her authorized representatives. No other warranty, expressed or implied, is made. Site safety, excavation support, and dewatering requirements are the responsibility of others. The scope of services for this project does not include either specifically or by implication any environmental or biological (for example, mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, we can provide a proposal for these services. The analyses and recommendations presented in this GER are based upon data obtained from the explorations performed on site. Variations in soil conditions can occur, the nature and extent of which may not become evident until construction. If variations Geotechnical Engineering Report 13 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 appear evident, RGI should be requested to reevaluate the recommendations in this GER prior to proceeding with construction. It is the client’s responsibility to see that all parties to the project, including the designers, contractors, subcontractors, are made aware of this GER in its entirety. The use of information contained in this GER for bidding purposes should be done at the contractor’s option and risk. USGS, 2014, Mercer Island, Washington USGS, 2014, Renton, Washington 7.5-Minute Quadrangle Approximate Scale: 1"=1000' 0 500 1000 2000 N Site Vicinity Map Figure 1 04/2018 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Jefferson and Kirkland Townhomes RGI Project Number 2018-070 Date Drawn: Address: 1513 Kirkland Avenue Northeast & 1526 Jefferson Avenue Northeast Renton, Washington 98056 SITE TP-1TP-2TP-3TP-4TP-504/2018Corporate Office17522 Bothell Way NortheastBothell, Washington 98011Phone: 425.415.0551Fax: 425.415.0311Jefferson and Kirkland TownhomesRGI Project Number2018-070Date Drawn:Address: 1513 Kirkland Avenue Northeast & 1526 Jefferson Avenue Northeast Renton, Washington 98056Geotechnical Exploration PlanFigure 2Approximate Scale: 1"=30'0153060N= Test pit by RGI, 3/30/18= Site boundary Incliniations) 12" Over the Pipe 3" Below the Pipe Perforated Pipe 4" Diameter PVC Compacted Structural Backfill (Native or Import) 12" min. Filter Fabric Material 12" Minimum Wide Free-Draining Gravel Slope to Drain (See Report for Appropriate Excavated Slope 04/2018 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Jefferson and Kirkland Townhomes RGI Project Number 2018-070 Date Drawn: Address: 1513 Kirkland Avenue Northeast & 1526 Jefferson Avenue Northeast Renton, Washington 98056 Retaining Wall Drainage Detail Figure 3 Not to Scale 3/4" Washed Rock or Pea Gravel 4" Perforated Pipe Building Slab Structural Backfill Compacted Filter Fabric 04/2018 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Jefferson and Kirkland Townhomes RGI Project Number 2018-070 Date Drawn: Address: 1513 Kirkland Avenue Northeast & 1526 Jefferson Avenue Northeast Renton, Washington 98056 Typical Footing Drain Detail Figure 4 Not to Scale Geotechnical Engineering Report April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 APPENDIX A FIELD EXPLORATION AND LABORATORY TESTING On March 30, RGI performed field explorations using a rubber tracked excavator. We explored subsurface soil conditions at the site by observing the excavation of five test pits to a maximum depth of 9.5 feet below existing grade. The test pit locations are shown on Figure 2. The test pit locations were approximately determined by measurements from existing property lines and paved roads. A geologist from our office conducted the field exploration and classified the soil conditions encountered, maintained a log of each test exploration, obtained representative soil samples, and observed pertinent site features. All soil samples were visually classified in accordance with the Unified Soil Classification System (USCS). Representative soil samples obtained from the explorations were placed in closed containers and taken to our laboratory for further examination and testing. As a part of the laboratory testing program, the soil samples were classified in our in house laboratory based on visual observation, texture, plasticity, and the limited laboratory testing described below. Moisture Content Determinations Moisture content determinations were performed in accordance with ASTM D2216-10 Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass (ASTM D2216) on representative samples obtained from the exploration in order to aid in identification and correlation of soil types. The moisture content of typical sample was measured and is reported on the test pit logs. Grain Size Analysis A grain size analysis indicates the range in diameter of soil particles included in a particular sample. Grain size analyses was determined using D6913-04(2009) Standard Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis (ASTM D6913) on seven of the samples. Project Name:Jefferson Highlands Townhomes Project Number:2018-070 Client:Anita Woo Test Pit No.: TP-1 Date(s) Excavated:3/30/2018 Excavation Method:Trackhoe Excavator Type:Rubber Tracked Excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By ELW Bucket Size:N/A Excavating Contractor:Ryatt Construction Sampling Method(s)Grab Location 1513 Kirkland Avenue NE & 1526 Jefferson Avenue NE, Renton, Washington Surface Conditions:Grass Total Depth of Excavation:9.5 feet bgs Approximate Surface Elevation N/A Compaction Method Bucket USCS SymbolTPSL SM GP SP-SM SM SM REMARKS AND OTHER TESTS 12% moisture 4% moisture, 1% fines 7% moisture, 10% fines 8% moisture, 15% fines 13% moistureGraphic LogMATERIAL DESCRIPTION 16" topsoil Reddish brown silty SAND with trace gravel, loose to medium dense, moist Gray GRAVEL with some sand and trace silt, medium dense, moist Gray SAND with some silt and trace gravel, medium dense, moist Contains roots Localized iron oxide staining Gray silty SAND with trace gravel, dense, moist Gray silty SAND with some gravel, very dense, moist (Glacial Till) Test Pit terminated at 9.5'Depth (feet)0 5 10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Jefferson Highlands Townhomes Project Number:2018-070 Client:Anita Woo Test Pit No.: TP-2 Date(s) Excavated:3/30/2018 Excavation Method:Trackhoe Excavator Type:Rubber Tracked Excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By ELW Bucket Size:N/A Excavating Contractor:Ryatt Construction Sampling Method(s)Grab Location 1513 Kirkland Avenue NE & 1526 Jefferson Avenue NE, Renton, Washington Surface Conditions:Grass Total Depth of Excavation:6.5 feet bgs Approximate Surface Elevation N/A Compaction Method Bucket USCS SymbolTPSL SM GP SP-SM SM REMARKS AND OTHER TESTS 3% moisture, 1% fines 9% moisture, 11% fines 15% moisture, 14% fines 12% moisture, 14% finesGraphic LogMATERIAL DESCRIPTION 12" topsoil Reddish brown silty SAND with trace gravel, loose to medium dense, moist Gray GRAVEL with some sand and trace silt, medium dense, moist Gray SAND with some silt and trace gravel, medium dense, moist Infiltration test at 4' Gray silty SAND with trace gravel, dense, wet Iron oxide staining Becomes moist to wet Test Pit terminated at 6.5'Depth (feet)0 5 10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Jefferson Highlands Townhomes Project Number:2018-070 Client:Anita Woo Test Pit No.: TP-3 Date(s) Excavated:3/30/2018 Excavation Method:Trackhoe Excavator Type:Rubber Tracked Excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By ELW Bucket Size:N/A Excavating Contractor:Ryatt Construction Sampling Method(s)Grab Location 1513 Kirkland Avenue NE & 1526 Jefferson Avenue NE, Renton, Washington Surface Conditions:Grass Total Depth of Excavation:5 feet bgs Approximate Surface Elevation N/A Compaction Method Bucket USCS SymbolTPSL SM SP-SM REMARKS AND OTHER TESTS 14% moisture 7% moisture 7% moistureGraphic LogMATERIAL DESCRIPTION 12" topsoil Reddish brown silty SAND with trace gravel, loose to medium dense, moist Gray SAND with some silt and trace gravel, medium dense, moist Test Pit terminated at 5'Depth (feet)0 5 10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Jefferson Highlands Townhomes Project Number:2018-070 Client:Anita Woo Test Pit No.: TP-4 Date(s) Excavated:3/30/2018 Excavation Method:Trackhoe Excavator Type:Rubber Tracked Excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By ELW Bucket Size:N/A Excavating Contractor:Ryatt Construction Sampling Method(s)Grab Location 1513 Kirkland Avenue NE & 1526 Jefferson Avenue NE, Renton, Washington Surface Conditions:Grass Total Depth of Excavation:5.5 feet bgs Approximate Surface Elevation N/A Compaction Method Bucket USCS SymbolTPSL Fill SM SP-SM SM REMARKS AND OTHER TESTS 17% moisture 9% moisture 12% moistureGraphic LogMATERIAL DESCRIPTION 6" topsoil Brown silty SAND with trace gravel, loose, moist (Fill) Contains brick debris Reddish brown silty SAND with trace gravel, loose to medium dense, moist Gray SAND with some silt and trace gravel, medium dense, moist Gray silty SAND with trace gravel, medium dense, moist Trace iron oxide stasining Test Pit terminated at 5.5'Depth (feet)0 5 10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Jefferson Highlands Townhomes Project Number:2018-070 Client:Anita Woo Test Pit No.: TP-5 Date(s) Excavated:3/30/2018 Excavation Method:Trackhoe Excavator Type:Rubber Tracked Excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By ELW Bucket Size:N/A Excavating Contractor:Ryatt Construction Sampling Method(s)Grab Location 1513 Kirkland Avenue NE & 1526 Jefferson Avenue NE, Renton, Washington Surface Conditions:Grass Total Depth of Excavation:6.5 feet bgs Approximate Surface Elevation N/A Compaction Method Bucket USCS SymbolTPSL Fill Fill TPSL SM SP-SM REMARKS AND OTHER TESTS 10% moisture 13% moisture 8% moistureGraphic LogMATERIAL DESCRIPTION 6" topsoil Brown silty SAND with trace gravel, medium dense, moist (Fill) Contains brick and metal debris Gray SAND with some silt and trace gravel, medium dense, moist (Fill) 6" topsoil Reddish brown silty SAND with trace gravel, medium dense, moist Gray SAND with some silt and trace gravel, medium dense, moist Test Pit terminated at 6.5'Depth (feet)0 5 10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Jefferson Highlands Townhomes Project Number:2018-070 Client:Anita Woo Key to Logs USCS SymbolREMARKS AND OTHER TESTSGraphic LogMATERIAL DESCRIPTIONDepth (feet)Sample NumberSample TypeElevation (feet)1 2 3 4 5 6 7 8 COLUMN DESCRIPTIONS 1 Elevation (feet): Elevation (MSL, feet). 2 Depth (feet): Depth in feet below the ground surface. 3 Sample Type: Type of soil sample collected at the depth interval shown. 4 Sample Number: Sample identification number. 5 USCS Symbol: USCS symbol of the subsurface material. 6 Graphic Log: Graphic depiction of the subsurface material encountered. 7 MATERIAL DESCRIPTION: Description of material encountered. May include consistency, moisture, color, and other descriptive text. 8 REMARKS AND OTHER TESTS: Comments and observations regarding drilling or sampling made by driller or field personnel. FIELD AND LABORATORY TEST ABBREVIATIONS CHEM: Chemical tests to assess corrosivity COMP: Compaction test CONS: One-dimensional consolidation test LL: Liquid Limit, percent PI: Plasticity Index, percent SA: Sieve analysis (percent passing No. 200 Sieve) UC: Unconfined compressive strength test, Qu, in ksf WA: Wash sieve (percent passing No. 200 Sieve) MATERIAL GRAPHIC SYMBOLS AF Poorly graded GRAVEL (GP) Silty SAND (SM) Poorly graded SAND with Silt (SP-SM) Topsoil TYPICAL SAMPLER GRAPHIC SYMBOLS Auger sampler Bulk Sample 3-inch-OD California w/ brass rings CME Sampler Grab Sample 2.5-inch-OD Modified California w/ brass liners Pitcher Sample 2-inch-OD unlined split spoon (SPT) Shelby Tube (Thin-walled, fixed head) OTHER GRAPHIC SYMBOLS Water level (at time of drilling, ATD) Water level (after waiting) Minor change in material properties within a stratum Inferred/gradational contact between strata ?Queried contact between strata GENERAL NOTES 1: Soil classifications are based on the Unified Soil Classification System. Descriptions and stratum lines are interpretive, and actual lithologic changes may be gradual. Field descriptions may have been modified to reflect results of lab tests. 2: Descriptions on these logs apply only at the specific boring locations and at the time the borings were advanced. They are not warranted to be representative of subsurface conditions at other locations or times. Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-1 PROJECT NO.2018-070 SAMPLE DEPTH 2.5' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)666.3 Weight Of Sample (gm)641.7 Wt Dry Soil & Tare (gm)(w2)641.7 Tare Weight (gm) 15.4 Weight of Tare (gm)(w3)15.4 (W6) Total Dry Weight (gm)626.3 Weight of Water (gm)(w4=w1-w2)24.6 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)626.3 Cumulative Moisture Content (%) (w4/w5)*100 4 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.4 0.00 0.00 100.00 cobbles % C GRAVEL 58.2 3.0"15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 14.8 2.5" coarse gravel % C SAND 2.6 2.0" coarse gravel % M SAND 14.5 1.5"15.4 0.00 0.00 100.00 coarse gravel % F SAND 9.0 1.0" coarse gravel % FINES 1.0 0.75"379.8 364.40 58.18 41.82 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"457.7 442.30 70.62 29.38 fine gravel D10 (mm)0.41 #4 472.6 457.20 73.00 27.00 coarse sand D30 (mm)9.5 #10 488.6 473.20 75.55 24.45 medium sand D60 (mm)23 #20 medium sand Cu 56.1 #40 579.4 564.00 90.05 9.95 fine sand Cc 9.6 #60 fine sand #100 630.3 614.90 98.18 1.82 fine sand #200 635.6 620.20 99.03 0.97 fines PAN 641.7 626.30 100.00 0.00 silt/clay 322 DESCRIPTION GRAVEL with some sand and trace silt USCS GP Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-1 PROJECT NO.2018-070 SAMPLE DEPTH 4' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)371.4 Weight Of Sample (gm)347.4 Wt Dry Soil & Tare (gm)(w2)347.4 Tare Weight (gm) 15.6 Weight of Tare (gm)(w3)15.6 (W6) Total Dry Weight (gm)331.8 Weight of Water (gm)(w4=w1-w2)24.0 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)331.8 Cumulative Moisture Content (%) (w4/w5)*100 7 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.6 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0"15.6 0.00 0.00 100.00 coarse gravel % F GRAVEL 6.7 2.5" coarse gravel % C SAND 4.2 2.0" coarse gravel % M SAND 26.8 1.5"15.6 0.00 0.00 100.00 coarse gravel % F SAND 52.0 1.0" coarse gravel % FINES 10.2 0.75"15.6 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"26.3 10.70 3.22 96.78 fine gravel D10 (mm)0.075 #4 37.9 22.30 6.72 93.28 coarse sand D30 (mm)0.2 #10 51.9 36.30 10.94 89.06 medium sand D60 (mm)0.4 #20 medium sand Cu 5.3 #40 140.9 125.30 37.76 62.24 fine sand Cc 1.3 #60 fine sand #100 288.0 272.40 82.10 17.90 fine sand #200 313.5 297.90 89.78 10.22 fines PAN 347.4 331.80 100.00 0.00 silt/clay 322 DESCRIPTION SAND with some silt and trace gravel USCS SP-SM Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-1 PROJECT NO.2018-070 SAMPLE DEPTH 6.5' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)490.6 Weight Of Sample (gm)454.9 Wt Dry Soil & Tare (gm)(w2)454.9 Tare Weight (gm) 15.4 Weight of Tare (gm)(w3)15.4 (W6) Total Dry Weight (gm)439.5 Weight of Water (gm)(w4=w1-w2)35.7 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)439.5 Cumulative Moisture Content (%) (w4/w5)*100 8 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.4 0.00 0.00 100.00 cobbles % C GRAVEL 5.1 3.0"15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 7.6 2.5" coarse gravel % C SAND 2.4 2.0" coarse gravel % M SAND 19.2 1.5"15.4 0.00 0.00 100.00 coarse gravel % F SAND 50.9 1.0" coarse gravel % FINES 14.9 0.75"37.9 22.50 5.12 94.88 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"65.9 50.50 11.49 88.51 fine gravel D10 (mm)#4 71.1 55.70 12.67 87.33 coarse sand D30 (mm)#10 81.6 66.20 15.06 84.94 medium sand D60 (mm)#20 medium sand Cu #40 165.8 150.40 34.22 65.78 fine sand Cc #60 fine sand #100 349.2 333.80 75.95 24.05 fine sand #200 389.3 373.90 85.07 14.93 fines PAN 454.9 439.50 100.00 0.00 silt/clay 322 DESCRIPTION Silty SAND with trace gravel USCS SM Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-2 PROJECT NO.2018-070 SAMPLE DEPTH 3' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)884.5 Weight Of Sample (gm)860.6 Wt Dry Soil & Tare (gm)(w2)860.6 Tare Weight (gm) 15.4 Weight of Tare (gm)(w3)15.4 (W6) Total Dry Weight (gm)845.2 Weight of Water (gm)(w4=w1-w2)23.9 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)845.2 Cumulative Moisture Content (%) (w4/w5)*100 3 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.4 0.00 0.00 100.00 cobbles % C GRAVEL 61.0 3.0"15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 17.8 2.5" coarse gravel % C SAND 3.5 2.0" coarse gravel % M SAND 12.1 1.5"15.4 0.00 0.00 100.00 coarse gravel % F SAND 4.9 1.0" coarse gravel % FINES 0.7 0.75"531.0 515.60 61.00 39.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"641.6 626.20 74.09 25.91 fine gravel D10 (mm)0.7 #4 681.7 666.30 78.83 21.17 coarse sand D30 (mm)12 #10 711.0 695.60 82.30 17.70 medium sand D60 (mm)24 #20 medium sand Cu 34.3 #40 813.2 797.80 94.39 5.61 fine sand Cc 8.6 #60 fine sand #100 850.4 835.00 98.79 1.21 fine sand #200 854.7 839.30 99.30 0.70 fines PAN 860.6 845.20 100.00 0.00 silt/clay 322 DESCRIPTION GRAVEL with some sand and trace silt USCS GP Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-2 PROJECT NO.2018-070 SAMPLE DEPTH 4' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)335.3 Weight Of Sample (gm)308.8 Wt Dry Soil & Tare (gm)(w2)308.8 Tare Weight (gm) 15.4 Weight of Tare (gm)(w3)15.4 (W6) Total Dry Weight (gm)293.4 Weight of Water (gm)(w4=w1-w2)26.5 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)293.4 Cumulative Moisture Content (%) (w4/w5)*100 9 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.4 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0"15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 9.6 2.5" coarse gravel % C SAND 5.2 2.0" coarse gravel % M SAND 21.0 1.5"15.4 0.00 0.00 100.00 coarse gravel % F SAND 53.1 1.0" coarse gravel % FINES 11.1 0.75"15.4 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"27.9 12.50 4.26 95.74 fine gravel D10 (mm)0.07 #4 43.7 28.30 9.65 90.35 coarse sand D30 (mm)0.19 #10 58.9 43.50 14.83 85.17 medium sand D60 (mm)0.39 #20 medium sand Cu 5.6 #40 120.6 105.20 35.86 64.14 fine sand Cc 1.3 #60 fine sand #100 249.7 234.30 79.86 20.14 fine sand #200 276.3 260.90 88.92 11.08 fines PAN 308.8 293.40 100.00 0.00 silt/clay 322 DESCRIPTION SAND with some silt and trace gravel USCS SP-SM Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-2 PROJECT NO.2018-070 SAMPLE DEPTH 5' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)499.0 Weight Of Sample (gm)435.6 Wt Dry Soil & Tare (gm)(w2)435.6 Tare Weight (gm) 15.4 Weight of Tare (gm)(w3)15.4 (W6) Total Dry Weight (gm)420.2 Weight of Water (gm)(w4=w1-w2)63.4 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)420.2 Cumulative Moisture Content (%) (w4/w5)*100 15 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.4 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0"15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 10.6 2.5" coarse gravel % C SAND 4.9 2.0" coarse gravel % M SAND 21.8 1.5"15.4 0.00 0.00 100.00 coarse gravel % F SAND 48.6 1.0" coarse gravel % FINES 14.1 0.75"15.4 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"33.4 18.00 4.28 95.72 fine gravel D10 (mm)#4 60.1 44.70 10.64 89.36 coarse sand D30 (mm)#10 80.7 65.30 15.54 84.46 medium sand D60 (mm)#20 medium sand Cu #40 172.3 156.90 37.34 62.66 fine sand Cc #60 fine sand #100 340.7 325.30 77.42 22.58 fine sand #200 376.4 361.00 85.91 14.09 fines PAN 435.6 420.20 100.00 0.00 silt/clay 322 DESCRIPTION Silty SAND with trace gravel USCS SM Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-2 PROJECT NO.2018-070 SAMPLE DEPTH 6' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)384.0 Weight Of Sample (gm)343.2 Wt Dry Soil & Tare (gm)(w2)343.2 Tare Weight (gm) 15.5 Weight of Tare (gm)(w3)15.5 (W6) Total Dry Weight (gm)327.7 Weight of Water (gm)(w4=w1-w2)40.8 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)327.7 Cumulative Moisture Content (%) (w4/w5)*100 12 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.5 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0"15.5 0.00 0.00 100.00 coarse gravel % F GRAVEL 10.5 2.5" coarse gravel % C SAND 5.5 2.0" coarse gravel % M SAND 24.4 1.5"15.5 0.00 0.00 100.00 coarse gravel % F SAND 45.7 1.0" coarse gravel % FINES 13.9 0.75"15.5 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"34.5 19.00 5.80 94.20 fine gravel D10 (mm)#4 49.9 34.40 10.50 89.50 coarse sand D30 (mm)#10 68.0 52.50 16.02 83.98 medium sand D60 (mm)#20 medium sand Cu #40 148.1 132.60 40.46 59.54 fine sand Cc #60 fine sand #100 272.1 256.60 78.30 21.70 fine sand #200 297.8 282.30 86.15 13.85 fines PAN 343.2 327.70 100.00 0.00 silt/clay 322 DESCRIPTION Silty SAND with trace gravel USCS SM Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 Jefferson Highlands Preliminary Technical Information Report 5/17/19 Appendix B WWHM2012 Output WWHM2012 PROJECT REPORT Jefferson Highlands 4/30/2019 10:08:09 AM Page 2 General Model Information Project Name:Jefferson Highlands Site Name: Site Address: City: Report Date:4/30/2019 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2018/10/10 Version:4.2.16 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year Jefferson Highlands 4/30/2019 10:08:09 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.604 Pervious Total 0.604 Impervious Land Use acre ROOF TOPS FLAT 0.099 DRIVEWAYS FLAT 0.086 Impervious Total 0.185 Basin Total 0.789 Element Flows To: Surface Interflow Groundwater Jefferson Highlands 4/30/2019 10:08:09 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Pasture, Mod 0.297 Pervious Total 0.297 Impervious Land Use acre DRIVEWAYS FLAT 0.238 Impervious Total 0.238 Basin Total 0.535 Element Flows To: Surface Interflow Groundwater Jefferson Highlands 4/30/2019 10:08:09 AM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.604 Total Impervious Area:0.185 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.297 Total Impervious Area:0.238 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.113655 5 year 0.166155 10 year 0.2052 25 year 0.259499 50 year 0.303627 100 year 0.350975 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.097246 5 year 0.125566 10 year 0.14554 25 year 0.172228 50 year 0.193195 100 year 0.21512 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.181 0.136 1950 0.187 0.127 1951 0.110 0.087 1952 0.066 0.065 1953 0.062 0.071 1954 0.090 0.081 1955 0.093 0.088 1956 0.094 0.087 1957 0.130 0.105 1958 0.080 0.079 Jefferson Highlands 4/30/2019 10:09:06 AM Page 16 Appendix Predeveloped Schematic Jefferson Highlands 4/30/2019 10:09:07 AM Page 17 Mitigated Schematic Jefferson Highlands 4/30/2019 10:09:08 AM Page 28 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. 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