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APPROVED PLN CANOD BLD2020-0474Applicant: TOWN CONST & DEVELOPMENT INC Property Owner: BIRKBY CRAIG & SHARON Critical Area File #: CRA2020-0113 Permit Number: BLD2020-0474 Site Location: 839 CARY RD Parcel Number: 27032400212400 Project Description: BIRKBY-ADDITION AND REMODEL Conditional Waiver. No critical area report is required for the project described above. There will be no alteration of a critical area. The proposal is an allowed activity pursuant to ECDC 23.40.220, 23.50.020, and/or 23.80.040. The proposal is exempt pursuant to ECDC 23.40.230. Erosion Hazard. Project is within erosion hazard area. Applicant must prepare an erosion and sediment control plan in compliance with ECDC 18.30. X Critical Area Report The project is within a critical area and/or critical area buffer and a report has been evaluated for Required. compliance with applicable criteria. Geotechnical report consistent with the requirements of ECDC 23.80.050 and address the criteria of ECDC 23.80.060 and 23.80.070 was reviewed and approved with the application. X Favorable Critical Area The proposed project as described above and as shown on the attached site plan meets or is Decision exempt from the criteria in ECDC 23.40.160, Review Criteria, and complies with the applicable provisions of the City of Edmonds critical area regulations. Any subsequent changes to the proposal shall void this decision pending re -review of the proposal. Conditions. Critical area specific condition(s) have been applied to the permit number referenced above. See referenced permit number for specific condition(s). X Notice on Title. Critical area notice on title recorded under AFN 20207200675. � Date July 30, 2020 Reviewer Appeals: Any decision to approve, condition, or deny a development proposal or other activity boased on the requirements of critical area regulations may be appealed according to, and as part of, the appeal procedure, if any, for the permit or approval involved. mom I LW RILEYGROUP C"telVI :ICIDr—Amill10I01Mall W,I;c'l20,14Z9]:i1 PREPARED BY: THE RILEY GROUP, INC. 17522 BOTHELL WAY NORTHEAST BOTHELL, WASHINGTON 98011 PREPARED FOR: CRAIG AND SHARON BIRKBY 495 2ND AVENUE NORTH EDMONDS, WASHINGTON 98029 RGI PROJECT No. 2020-286-1 BIRKBY ADDITION 839 CARY ROAD EDMONDS, WASHINGTON JULY 1, 2020 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone 425.415.0551 * Fax 425.415.0311 www.riley-group.com mom 1 L RILEYGROUP July 1, 2020 Craig and Sharon Birkby 495 2nd Avenue North Edmonds, Washington 98029 Subject: Geotechnical Engineering Report Birkby Addition 839 Cary Road Edmonds, Washington RGI Project No. 2020-286-1 Dear Mr. and Mrs. Birkby: As requested, The Riley Group, Inc. (RGI) has performed a Geotechnical Engineering Report (GER) for the Birkby Addition located at 839 Cary Road, Edmonds, Washington. Our services were completed in accordance with our proposal 2020-286-PRP1 dated June 9, 2020 and authorized by you on June 11, 2020. The information in this GER is based on our understanding of the proposed construction, and -Che soil and groundwater conditions encountered in the borings and hand auger completed by RGI at the site on June 24, 2020. Based on our explorations and analysis, the proposed construction including the deck are feasible from a geotechnical engineering standpoint. The slope offsite to the west is stable in its present condition and configuration and the development as proposed will no adversely affect the stability of the slope. If you have any questions or require additional information, please contact us. Respectfully submitted, THE RILEY GROUP, INC. Eric L. Woods, LG Project Geologist SARI& 4 WASrl�� zt s A 7 / 2D Z6 Kristina M. Weller, PE Principal Geotechnical Engineer Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone 425.415.0551 ®Fox 425.415.0311 www.riley-group.com Geotechnical Engineering Report i July 1, 2020 Birkby Addition, Edmonds, Washington RGI Project No. 2020-286-1 TABLE OF CONTENTS 1.0 INTRODUCTION...............................................................................................................................1 2.0 PROJECT DESCRIPTION............................................................................................................... 1 3.0 FIELD EXPLORATION AND LABORATORY TESTING.......................................................... 1 3.1 FIELD EXPLORATION................................................................................................................................... 1 3.2 LABORATORY TESTING................................................................................................................................2 4.0 SITE CONDITIONS........................................................................................................................... 2 4.1 SURFACE..................................................................................................................................................2 4.2 GEOLOGY.................................................................................................................................................2 4.3 SOILS.......................................................................................................................................................2 4.4 GROUNDWATER........................................................................................................................................3 4.5 SEISMIC CONSIDERATIONS...........................................................................................................................3 4.6 GEOLOGIC HAZARD AREAS..........................................................................................................................4 5.0 DISCUSSION AND RECOMMENDATIONS................................................................................. 4 5.1 GEOTECHNICAL CONSIDERATIONS .................................................................................................................4 5.2 EARTHWORK.............................................................................................................................................4 5.2.1 Erosion and Sediment Control.....................................................................................................4 5.2.2 Stripping and Subgrade Preparation............................................................................................5 5.2.3 Excavations...................................................................................................................................6 5.2.4 Structural Fill................................................................................................................................6 5.2.5 Wet Weather Construction Considerations.................................................................................7 5.3 FOUNDATIONS.......................................................................................................................................... 8 5.4 RETAINING WALLS.....................................................................................................................................9 5.5 SLAB -ON -GRADE CONSTRUCTION................................................................................................................. 9 5.6 DRAINAGE..............................................................................................................................................10 5.6.1 Surface.......................................................................................................................................10 5.6.2 Subsurface..................................................................................................................................10 5.6.3 Permeable pavements...............................................................................................................10 6.0 LIMITATIONS................................................................................................................................. 10 LIST OF FIGURES AND APPENDICES Figure1.....................................................................................................................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 mom 1 LW RILEYGRDIIR Geotechnical Engineering Report ii July 1, 2020 BirkbyAddition, Edmonds, Washington RGI Project No. 2020-286-1 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 two borings and one hand auger to approximate depths of 4 to 11.5 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 fill comprised of very loose to loose silty sand with some gravel over native deposits of very loose to very dense silty sand with trace to some gravel. 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. 1 LM RILEYGROUP Geotechnical Engineering Report 1 July 1, 2020 BirkbyAddition, Edmonds, Washington RGI Project No. 2020-286-1 1.0 Introduction This Geotechnical Engineering Report (GER) presents the results of the geotechnical engineering services provided for the Birkby Addition in Edmonds, Washington. The purpose of this evaluation is to assess subsurface conditions and provide geotechnical recommendations for the construction of an addition to an existing single family residence, a deck, and a new driveway. 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 839 Cary Road in Edmonds, Washington. The approximate location of the site is shown on Figure 1. The site is currently occupied by a single family residence. RGI understands that additions and a deck will be constructed on the west side of the existing single family residence, and an existing driveway will be replaced. 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. 3.0 Field Exploration and Laboratory Testing 3.1 FIELD EXPLORATION On June 24, 2020, RGI observed the drilling of two borings and one hand auger. The approximate exploration locations are shown on Figure 2. Field logs of each exploration were prepared by the geologist that continuously observed the drilling. These logs included visual classifications of the materials encountered during drilling as well as our interpretation of the subsurface conditions between samples. The boring and hand auger logs included in Appendix A represent an interpretation of the field 1 LM RILEYGROUP Geotechnical Engineering Report 2 July 1, 2020 BirkbyAddition, Edmonds, Washington RGI Project No. 2020-286-1 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 borings and hand auger 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 an irregular -shaped parcel of land approximately 0.72 acres in size. The site is bound to the north and south by single family residences, to the east by Cary Road, and to the west by Puget Sound. A railroad easement extends through the western portion of the property. The existing site is occupied by a single family residence in the central portion of the property. A paved driveway extends west from Cary Road to the residence. The central and eastern portion of the property slope generally east with about 15 feet of elevation change at gradients of about 5 percent. The western portion of the property slopes west with about 35 feet of elevation change, with an upper slope that descends to the railroad easement at gradients of over 100 percent and a lower bulkhead that descends from the railroad easement to Puget Sound at gradients of about 40 percent. The site is vegetated with grass and decorative plants and shrubs and scattered small- to large -diameter trees. 4.2 GEOLOGY Review of the Geologic Map of the Edmonds East and part of the Edmonds West Quadrangles, Washington, by James P. Minard, (1983) indicates that the soil in the project vicinity is mapped as Whidbey Formation (Map Unit Qw), which are bedded interglacial sediments deposited below Possesion Drift glacial deposits. These descriptions are generally similar to the findings in our field explorations. 4.3 SOILS The soils encountered during field exploration include fill comprised of very loose to loose silty sand with some gravel over native deposits of very loose to very dense silty sand with trace to some gravel. 1 LW RILEYGROUP Geotechnical Engineering Report 3 July 1, 2020 BirkbyAddition, Edmonds, Washington RGI Project No. 2020-286-1 More detailed descriptions of the subsurface conditions encountered are presented in the boring and hand auger logs included in Appendix A. Sieve analysis was performed on four selected soil samples. Grain size distribution curves are included in Appendix A. 4.4 GROUNDWATER No groundwater seepage was encountered during our subsurface exploration. No surface water was observed. 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. 4.5 SEISMIC CONSIDERATIONS Based on the International Building Code (IBC), RGI recommends the follow seismic parameters for design. Table 1 IBC Parameter 2015 Value 2018 Value Site Soil Class' CZ Site Latitude 47.8198 Site Longitude-122.3751 Short Period Spectral Response Acceleration, Ss (g) 1.276 1.291 1-Second Period Spectral Response Acceleration, Sl (g) 0.5 0.455 Adjusted Short Period Spectral Response Acceleration, SMs (g) 1.276 1.549 Adjusted 1-Sec Period Spectral Response Acceleration, Sm, (g) 0.65 0.683 Numeric seismic design value at 0.2 second; SDs(g) 0.85 1.033 Numeric seismic design value at 1.0 second; Soi(g) 0.433 0.455 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 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. Borings and hand auger extended to a maximum depth of 11.5 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 1 LW RILEYGROUP Geotechnical Engineering Report 4 July 1, 2020 BirkbyAddition, Edmonds, Washington RGI Project No. 2020-286-1 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 glacially consolidated deposits and lack an established shallow groundwater table, RGI considers that the possibility of liquefaction during an earthquake is minimal. 4.E GEOLOGIC HAZARD AREAS Regulated geologically hazardous areas include erosion, landslide, earthquake, or other geological hazards. Based on the definition in the Edmonds Community Development Code (ECDC), the 20 foot high slope on the west side of the existing yard area is an erosion and landslide hazard area. We recommend a setback of 20 foot for all structures. This setback will maintain factors of safety for the slope greater than provided in Sections 23.80.060 and 23.80.070 of the ECDC. The slope stability analysis is included in Appendix B. 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 and deck can be supported on conventional spread footings bearing on competent 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 foundations. Erosion control measures should be installed prior to earth disturbance. 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. 1 LW RILEYGROUP Geotechnical Engineering Report 5 July 1, 2020 BirkbyAddition, Edmonds, Washington RGI Project No. 2020-286-1 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 ➢ 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 borings and hand auger encountered about 4 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 1 LW RILEYGROUP Geotechnical Engineering Report 6 July 1, 2020 BirkbyAddition, Edmonds, Washington RGI Project No. 2020-286-1 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 very loose to very dense silty sand with trace to some gravel. 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 ➢ 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 low LM RILEYGROUP Geotechnical Engineering Report 7 July 1, 2020 BirkbyAddition, Edmonds, Washington RGI Project No. 2020-286-1 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 American Society of Testing and Materials D1557-09 Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (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. 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. Table 2 Structural Fill Gradation U.S. Sieve Size 4 inches No. 4 sieve No. 200 sieve *Based on minus 3/4 inch fraction. Percent Passing 100 22 to 100 0to5* 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 to at least 95 percent of the maximum dry density. The soil's maximum density and optimum moisture should be determined by ASTM D1557. 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 project. Free water should not be allowed to pond on the subgrade soils. RGI anticipates that the 1 LW RILEYGROUP Geotechnical Engineering Report 8 July 1, 2020 BirkbyAddition, Edmonds, Washington RGI Project No. 2020-286-1 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 competent 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 loose soils are encountered, the soils should be moisture conditioned and compacted to a firm and unyielding condition. The foundation design value assumes the foundation is supported on at least two feet of medium dense native soil or structural fill. 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 3 Foundation Design Design Parameter Value Allowable Bearing Capacity 2,000 psfl 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. 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. 1 LW RILEYGROUP Geotechnical Engineering Report 9 BirkbyAddition, Edmonds, Washington July 1, 2020 RGI Project No. 2020-286-1 5.4 RETAINING WALLS If retaining walls are needed in the building area, 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 4 Retaining Wall Design Design Parameter Value Allowable Bearing Capacity I 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. 1 LM RILEYGROUP Geotechnical Engineering Report 10 July 1, 2020 BirkbyAddition, Edmonds, Washington RGI Project No. 2020-286-1 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 PERMEABLE PAVEMENTS We understand it is proposed to expand the existing driveway. A permeable surface is being considered. The soils in the area of the existing driveway consist of silty sand with gravel and should be suitable for a permeable surface. Some of the driveway may be closer to the landslide hazard area than 50 feet, however the placement of the permeable surface should not adversely impact the stability of the slope. 6.0 Limitations This GER is the property of RGI, Craig and Sharon Birkby, and their 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 Birkby Addition project in Edmonds, Washington, and for the exclusive use of Craig and Sharon Birkby and their 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 now LW RILEYGROUP Geotechnical Engineering Report 11 July 1, 2020 BirkbyAddition, Edmonds, Washington RGI Project No. 2020-286-1 and extent of which may not become evident until construction. If variations 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. 1 LM RILEYGROUP =r� IN �' Suns,et Beach Q `'a u _ DALEY ST___ a. Edmo Ferry PO Landing ® LL ST- / 0V DAYTON.ST ,Q MAPLE ST ��.. �_. AeDERIST I� WALNUT 5T In i P USGS, 2014, Edmonds West, Washington Approximate Scale: 1"=1000' USGS, 2017, Edmonds East, Washington A 7.5-Minute Quadrangle 0 500 1000 2000 N Corporate Office Birkby Addition Figure 1 17522 Bothell Way Northeast -Bothell, Washington 98011 RGI Project Number: Site Vicinity Map Date Drawn: Phone: 425.415.0551 2020-286-1 07�2020 RILEYGROUP Fax:425.415.0311 Address: 839 Cary Road, Edmonds, Washington 98029 `Ij y. r k •� 903 M e� B- 01 B-1 839 HA-1 r, L" 82,7 m = Hand auger by RGI, 06/24/20 = Boring by RGI, 06/24/20 ApIMMIproximate Scale: 1"=60' = ASite boundary 0 30 60 120 N Corporate Office Birkby Addition Figure 2 17522 Bothell Way Northeast RGI Project Number: Date Drawn: &Q Bothell, Washington 98011 Geotechnical Exploration Plan Phone: 425.415.0551 2020-286-1 07/2020 RILEY00000 Fax: 425.415.0311 Address: 839 Cary Road, Edmonds, Washington 98029 12" Minimum Wide Free -Draining Gravel I Slope to Drain �r vialIICUci rv%, Perforated Pipe Not to Scale I Slope )rt for ate )ns) ural Import) Corporate Office Birkby Addition Figure 3 17522 Bothell Way Northeast RGI Project Number: Date Drawn: -Bothell, Washington 98011 2020-286-1 Retaining Wall Drainage Detail Phone: 425.415.0551 07�2020 RILEYGROUP Fax:425.415.0311 Address: 839 Cary Road, Edmonds, Washington 98029 a/-+ VVa311cu iAuUnui rca "JIavuI Not to Scale Corporate Office Birkby Addition Figure 4 17522 Bothell Way Northeast RGI Project Number: Date Drawn: -Bothell, Washington 98011 2020-286-1 Typical Footing Drain Detail Phone: 425.415.0551 07�2020 RILEYGROUP Fax:425.415.0311 Address: 839 Cary Road, Edmonds, Washington 98029 Geotechnical Engineering Report July 1, 2020 BirkbyAddition, Edmonds, Washington RGI Project No. 2020-286-1 APPENDIX A FIELD EXPLORATION AND LABORATORY TESTING On June 24, 2020, RGI performed field explorations using an acker limited access drill rig and a hand auger. We explored subsurface soil conditions at the site by observing the drilling of two borings and one hand auger to a maximum depth of 11.5 feet below existing grade. The boring and hand auger locations are shown on Figure 2. The boring and hand auger 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 boring and hand auger 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 four of the samples. 1 LW RILEYGROUP Project Name: Birkby Addition Boring No.: B-1 Project Number: 2020-286-1 1 L- Client: Craig and Sharon Birkby RILEYGROUP Sheet 1 of 1 Date(s) Drilled: 6/24/2020 Logged By: ELW Surface Conditions: Grass Drilling Method(s): Hollow Stem Auger Drill Bit Size/Type: 6" auger Total Depth of Borehole: 11.42 feet bgs Drill Rig Type: Acker Drilling Contractor: Bortec Approximate N/A Surface Elevation: Groundwater Level: Not Encountered Sampling Method(s): SPT Hammer Data: 140 lb, 30" drop, rope and cathead Borehole Backfill: Bentonite Chips Location: 839 Cary Road, Edmonds, Washington ai U C w ^Q. N N N n 0 c C 0)^ i T U) J U_ V L Q N O Ct) Q N w 0 U) <n Z a 0 Z) 0 MATERIAL DESCRIPTION � Fill JBrown silty SAND with some gravel, very loose to loose, moist (Fill) 1 2 3 4 SM Tan mottled silty SAND with trace gravel, very loose to loose, moist to wet 17 4 5tA I I I MI —Becomes gray, dense, moist 39% fines 37 12 6 Contains thin sand interbeds, localized iron oxide staining 7 very dense, contains sand interbeds 10 8 Boring terminated at 11' 5" Project Name: Birkby Addition Boring No.: B-2 Project Number: 2020-286-1 1 L- Client: Craig and Sharon Birkby RILEYGROUP Sheet 1 of 1 Date(s) Drilled: 6/24/2020 Logged By: ELW Surface Conditions: Grass Drilling Method(s): Hollow Stem Auger Drill Bit Size/Type: 6" auger Total Depth of Borehole: 10.92 feet bgs Drill Rig Type: Acker Drilling Contractor: Bortec Approximate N/A Surface Elevation: Groundwater Level: Not Encountered Sampling Method(s): SPT Hammer Data: 140 lb, 30" drop, rope and cathead Borehole Backfill: Bentonite Chips Location: 839 Cary Road, Edmonds, Washington ai U C w ^Q. N N N n 0 c C 0)^ i T U) J U_ V L S1 N O in Q N w 0 in <n Z � � Z) 0 MATERIAL DESCRIPTION � 0 TPSL 4" topsoil Fill JgBrown silty SAND with some gravel, loose, moist (Fill) 1 SM Reddish brown silty SAND with trace gravel, loose, moist 2 Becomes tan, mottled, moist to wet 3 7 16 4 gray, dense, moist 35 6 7 very dense 8 50/6" m 8 10 SMK—Borino Gray silty SAND with some gravel, very dense, moist 50/5" 30% fines 9 11 terminated at 10' 11" 12 Project Name: Birkby Addition Key to Log of Boring Project Number: 2020-286-1 1 L- Client: Craig and Sharon Birkby RILEYGROUP Sheet 1 of 1 w C w ^ a) La 0 N0. U) 0 U C co N 0) a !N Cn —Z° ^ 0 i - O 0 n T Ct) Z) O0 J � Q 0 MATERIAL DESCRIPTION c 7 N � 1 2 3 L4J [A COLUMN DESCRIPTIONS 1 Elevation (feet): Elevation (MSL, feet). © Recovery (%): Core Recovery Percentage is determined based on 2 Depth (feet): Depth in feet below the ground surface. a ratio of the length of core sample recovered compared to the LIJ Sample Type: Type of soil sample collected at the depth interval cored interval length. shown. 7 USCS Symbol: USCS symbol of the subsurface material. ® Sampling Resistance, blows/ft: Number of blows to advance driven 8 Graphic Log: Graphic depiction of the subsurface material sampler one foot (or distance shown) beyond seating interval encountered. using the hammer identified on the boring log. 0 MATERIAL DESCRIPTION: Description of material encountered. ROD (%): Rock Quality Designation is a relative index of the rock May include consistency, moisture, color, and other descriptive mass quality calculated by comparing the cumulative length of text. intact pieces of core exceeding 100 mm in length to the cored Moisture (%): Moisture, expressed as a water content. interval length. FIELD AND LABORATORY TEST ABBREVIATIONS CHEM: Chemical tests to assess corrosivity PI: Plasticity Index, percent COMP: Compaction test SA: Sieve analysis (percent passing No. 200 Sieve) CONS: One-dimensional consolidation test UC: Unconfined compressive strength test, Qu, in ksf LL: Liquid Limit, percent WA: Wash sieve (percent passing No. 200 Sieve) MATERIAL GRAPHIC SYMBOLS 9M AF ® Silty SAND (SM) Topsoil TYPICAL SAMPLER GRAPHIC SYMBOLS OTHER GRAPHIC SYMBOLS Auger sampler CME Sampler Pitcher Sample Water level (at time of drilling, ATD) Bulk Sample Grab Sample Water level (after waiting) 2-inch-unlined split Minor change in material properties within a spoon PT) (S 3-inch-OD California w/ ' 2.5-inch-OD Modified brass rings California w/ brass liners stratum Shelby Tube (Thin -walled, - Inferred/gradational contact between strata fixed head) —?- 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. Project Name: Birkby Addition Hand Auger No.: HA-1 Project Number: 2020-286-1 Client: Craig and Sharon Birkby RILEYGROUP Sheet 1 of 1 Date(s) Drilled: 6/24/2020 Logged By: ELW Surface Conditions: Grass Drilling Method(s): Hand Auger Drill Bit Size/Type: N/A Total Depth of Borehole: 4 feet bgs Drill Rig Type: N/A Drilling Contractor: N/A Approximate N/A Surface Elevation: Groundwater Level: Not Encountered Sampling Method(s): Auger Hammer Data: N/A Borehole Backfill: Cuttings Location: 839 Cary Road, Edmonds, Washington i Z Zey croup, rnc. 11111 Bothell Way NE, Bothell, WA 98011 Project Name: Birkby Addition Key to Log of Boring Project Number: 2020-286-1 Client: Craig and Sharon Birkby RILEYGROUP Sheet 1 of 1 6 U C co w ^ N0. N N n O0 c C a)i d N C N T U) J U (6 L fl. fl. N 0O (n Q N w 0 in Un <n Z � Z) 0 MATERIAL DESCRIPTION � COLUMN DESCRIPTIONS 1 Elevation (feet): Elevation (MSL, feet). © Recovery (%): Core Recovery Percentage is determined based on 2 Depth (feet): Depth in feet below the ground surface. a ratio of the length of core sample recovered compared to the LIJ Sample Type: Type of soil sample collected at the depth interval cored interval length. shown. 7 USCS Symbol: USCS symbol of the subsurface material. B4 Sample ID: Sample identification number. 8 Graphic Log: Graphic depiction of the subsurface material 5 Sampling Resistance, blows/ft: Number of blows to advance driven encountered. sampler one foot (or distance shown) beyond seating interval �9 MATERIAL DESCRIPTION: Description of material encountered. using the hammer identified on the boring log. May include consistency, moisture, color, and other descriptive text. 1� Moisture (%): Moisture, expressed as a water content. FIELD AND LABORATORY TEST ABBREVIATIONS CHEM: Chemical tests to assess corrosivity COMP: Compaction test CONS: One-dimensional consolidation test LL: Liquid Limit, percent MATERIAL GRAPHIC SYMBOLS TYPICAL SAMPLER GRAPHIC SYMBOLS Auger sampler Bulk Sample 3-inch-OD California w/ brass rings GENERAL NOTES CME Sampler Grab Sample 2.5-inch-OD Modified California w/ brass liners 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) go Silty SAND (SM) : 4b SA7. Topsoil OTHER GRAPHIC SYMBOLS Pitcher Sample Water level (at time of drilling, ATD) 2-inch-OD unlined split Water level (after waiting) spoon (SPT) Minor change in material properties within a stratum Shelby Tube (Thin -walled, — — Inferred/gradational contact between strata fixed head) —?- Queried contact between strata 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. The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 THE RILEY GROUP, INC. PHONE: (425) 415-0551 17522 Bothell Way NE FAX: (425) 415-0311 Bothell, WA 98011 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Birkby Addition SAMPLE ID/TYPE B-1 PROJECT NO. 2020-286-1 SAMPLE DEPTH 5' TECH/TEST DATE ELW 6/24/2020 DATE RECEIVED 6/24/2020 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moistu Wt Wet Soil & Tare (gm) (w1) 500.7 Weight Of Sample (gm) 447.3 Wt Dry Soil & Tare (gm) (w2) 447.3 Tare Weight (gm) 16.1 Weight of Tare (gm) (w3) 16.1 (W6) Total Dry Weight (gm) 431.2 Weight of Water (gm) (w4=w1-w2) 53.4 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 431.2 Cumulative Moisture Content (%) (w4/w5)*100 12 Wt Ret Wt-Tare (%Retained) % PASS +Tare f(wtret/w6)*1001 (100-9/.ret) % COBBLES 0.0 12.0" % C GRAVEL 0.0 3.0" • F GRAVEL 9.8 2.5" % C SAND 5.5 2.0" % M SAND 17.2 1.5" % F SAND 28.8 1.0" • FINES 38.8 0.75" % TOTAL 100.0 0.50" 0.375" D10 (mm) #4 D30 (mm) #10 D60 (mm) #20 Cu #40 Cc #60 #100 #200 PAN 16.1 0.00 0.00 100.00 16.1 0.00 0.00 100.00 16.1 0.00 0.00 100.00 16.1 0.00 0.00 100.00 35.5 19.40 4.50 95.50 58.2 42.10 9.76 90.24 81.9 65.80 15.26 84.74 155.9 139.80 32.42 67.58 251.0 234.90 54.48 45.52 279.9 263.80 61.18 38.82 447.3 431.20 100.00 0.00 12" 3" 2" 1".75 .375" #4 #10 #20 #40 #60 #100 #200 % 100 90 80 P 70 A 60 S 50 40 S 30 1 20 N 10 0 G 1000 100 10 1 0.1 0.01 Grain size in millimeters DESCRIPTION Silty SAND with trace gravel USCS SM Prepared For: Craig and Sharon Birkby Reviewed By: KMW cobbles coarse gravel coarse gravel coarse gravel coarse gravel coarse gravel fine gravel fine gravel fine gravel coarse sand medium sand medium sand fine sand fine sand fine sand fines silt/clay 0.001 mom ,_ RILEYGROUP THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 PROJECT TITLE Birkby Addition PROJECT NO. 2020-286-1 TECH/TEST DATE ELW WATER CONTENT (Delivered Moisture) GRAIN SIZE ANALYSIS II ASTM D421, D422, D1140, D2487, D6913 Wt Wet Soil & Tare (gm) (w1) Wt Dry Soil & Tare (gm) (w2) Weight of Tare (gm) (w3) Weight of Water (gm) (w4=w1-w2) Weight of Dry Soil (gm) (w5=w2-w3) Moisture Content (%) (w4/w5)*100 6/24/2020 479.3 443.0 16.3 36.3 426.7 9 % COBBLES 0.0 12.0' % C GRAVEL 0.0 3.0' % F GRAVEL 15.4 2.5' %CSAND 6.6 2.0' % M SAND 18.3 1.5' % F SAND 30.1 1.0' % FINES 29.7 0.75' % TOTAL 100.0 0.50' 0.375' D10 (mm) #4 D30 (mm) #1c D60 (mm) #2C Cu #4C Cc #6C #10c #20C PAN 12" 3" 2" 1".75" .375" #4 o� P A S S I N G 100 90 80 70 60 50 40 30 20 10 0 SAMPLE ID/TYPE SAMPLE DEPTH DATE RECEIVED B-2 10, 6/24/2020 Weight Of Sample (gm) 443.0 Tare Weight (gm) 16.3 (W6) Total Dry Weight (gm) 426.7 SIEVE ANALYSIS Cumulative Wt Ret Wt-Tare (%Retained) % PASS +Tare 1(wtrPt/w61*1001 (100-%ret) 16.3 0.00 0.00 100.00 16.3 0.00 0.00 100.00 16.3 0.00 0.00 100.00 16.3 0.00 0.00 100.00 51.1 34.80 8.16 91.84 82.0 65.70 15.40 84.60 110.1 93.80 21.98 78.02 188.0 171.70 40.24 59.76 285.7 269.40 63.14 36.86 316.4 300.10 70.33 29.67 443.0 426.70 100.00 0.00 #10 #20 #40 #60 #100 #200 1000 100 10 1 Grain size in millimeters DESCRIPTION Silty SAND with some gravel USCS SM Prepared For: Craig and Sharon eirkby Reviewed By: KMW :obbles :oarse gravel :oarse gravel :oarse gravel :oarse gravel :oarse gravel fine gravel fine gravel fine gravel :oarse sand medium sand medium sand fine sand fine sand fine sand fines silt/clay 0.1 0.01 0.001 mom ,- RILEYGROUP THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 PROJECT TITLE Birkby Addition PROJECT NO. 2020-286-1 TECH/TEST DATE ELW WATER CONTENT (Delivered Moisture) GRAIN SIZE ANALYSIS II ASTM D421, D422, D1140, D2487, D6913 Wt Wet Soil & Tare (gm) (w1) Wt Dry Soil & Tare (gm) (w2) Weight of Tare (gm) (w3) Weight of Water (gm) (w4=w1-w2) Weight of Dry Soil (gm) (w5=w2-w3) Moisture Content (%) (w4/w5)*100 6/24/2020 251.6 216.4 16.1 35.2 200.3 18 % COBBLES 0.0 12.0" % C GRAVEL 0.0 3.0" % F GRAVEL 6.4 2.5" % C SAND 5.0 2.0" % M SAND 18.9 1.5" % F SAND 41.3 1.0" % FINES 28.4 0.75" % TOTAL 100.0 0.50" 0.375" D10 (mm) #4 D30 (mm) #10 D60 (mm) #20 Cu #40 Cc #60 #100 #200 PAN 12" 3" 2" 1".75" .375" #4 o� P A S S I N G 100 90 80 70 60 50 40 30 20 10 0 SAMPLE ID/TYPE SAMPLE DEPTH DATE RECEIVED HA-1 1.51 6/24/2020 Weight Of Sample (gm) 216.4 Tare Weight (gm) 16.1 (W6) Total Dry Weight (gm) 200.3 SIEVE ANALYSIS Cumulative Wt Ret Wt-Tare (%Retained) % PASS +Tare 1(wtrPt/w61*1001 (100-%ret) 16.1 0.00 0.00 100.00 16.1 0.00 0.00 100.00 16.1 0.00 0.00 100.00 16.1 0.00 0.00 100.00 22.2 6.10 3.05 96.95 29.0 12.90 6.44 93.56 39.0 22.90 11.43 88.57 76.8 60.70 30.30 69.70 141.4 125.30 62.56 37.44 159.5 143.40 71.59 28.41 216.4 200.30 100.00 0.00 #10 #20 #40 #60 #100 #200 1000 100 10 1 Grain size in millimeters DESCRIPTION Silty SAND with trace gravel USCS SM Prepared For: Craig and Sharon eirkby Reviewed By: KMW :obbles :oarse gravel :oarse gravel :oarse gravel :oarse gravel :oarse gravel fine gravel fine gravel fine gravel :oarse sand medium sand medium sand fine sand fine sand fine sand fines silt/clay 0.1 0.01 0.001 mom ,- RILEYGROUP THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 PROJECT TITLE Birkby Addition PROJECT NO. 2020-286-1 TECH/TEST DATE ELW WATER CONTENT (Delivered Moisture) GRAIN SIZE ANALYSIS II ASTM D421, D422, D1140, D2487, D6913 Wt Wet Soil & Tare (gm) (w1) Wt Dry Soil & Tare (gm) (w2) Weight of Tare (gm) (w3) Weight of Water (gm) (w4=w1-w2) Weight of Dry Soil (gm) (w5=w2-w3) Moisture Content (%) (w4/w5)*100 6/24/2020 315.8 285.2 16.0 30.6 269.2 11 % COBBLES 0.0 12.0' % C GRAVEL 0.0 3.0' % F GRAVEL 5.5 2.5' %CSAND 8.0 2.0' % M SAND 29.3 1.5' % F SAND 33.8 1.0' % FINES 23.4 0.75' % TOTAL 100.0 0.50' 0.375' D10 (mm) #4 D30 (mm) #1C D60 (mm) #2C Cu #4C Cc #6C #10C #20C PAN 12" 3" 2" 1".75" .375" #4 o� P A S S I N G 100 90 80 70 60 50 40 30 20 10 0 SAMPLE ID/TYPE SAMPLE DEPTH DATE RECEIVED HA-1 3.5' 6/24/2020 Weight Of Sample (gm) 285.2 Tare Weight (gm) 16.0 (W6) Total Dry Weight (gm) 269.2 SIEVE ANALYSIS Cumulative Wt Ret Wt-Tare (%Retained) % PASS +Tare 1(wtrPt/w61*1001 (100-%ret) 16.0 0.00 0.00 100.00 16.0 0.00 0.00 100.00 16.0 0.00 0.00 100.00 16.0 0.00 0.00 100.00 17.3 1.30 0.48 99.52 30.8 14.80 5.50 94.50 52.3 36.30 13.48 86.52 131.3 115.30 42.83 57.17 208.3 192.30 71.43 28.57 222.2 206.20 76.60 23.40 285.2 269.20 100.00 0.00 #10 #20 #40 #60 #100 #200 1000 100 10 1 Grain size in millimeters DESCRIPTION Silty SAND with trace gravel USCS SM Prepared For: Craig and Sharon eirkby Reviewed By: KMW :obbles :oarse gravel :oarse gravel :oarse gravel :oarse gravel :oarse gravel fine gravel fine gravel fine gravel :oarse sand medium sand medium sand fine sand fine sand fine sand fines silt/clay 0.1 0.01 0.001 mom ,- RILEYGROUP Geotechnical Engineering Report BirkbyAddition, Edmonds, Washington July 1, 2020 RGI Project No. 2020-286-1 APPENDIX B SLOPE STABILITY RGI performed the slope stability analysis by using a computer program, Slide version 6.0, which was developed by Rocscience. The safety factor for the critical surfaces was calculated by the Bishop Method. The analyses were performed for the slopes under existing and post -construction static and seismic conditions. For seismic analysis, peak ground acceleration (PGA) was determined to be 0.518g based on ASCE 7-10 Standard. Following the procedure recommended in NCHRP Seismic Analysis and Design of Retaining Walls, Buried Structures, Slopes, and Embankments (Report 611) and FHWA LRFD Seismic Analysis and Design of Transportation Geotechnical Features and Structural Foundations Manual (2011), a seismic coefficient of 0.23 was determined which is used in the pseudo -static slope stability analysis. 1 LW RILEYGROUP Safety Factor 0 0.000 0.250 0.5.00 4.180 0.750 1.000 1.250 1.500 1.750 0 2.000 ao 2.250 2.500 2.750 Unit Weight Cohesion Water Material Name Color Strength Type phi Surface Ru Safety Factor 0 0.000 0.250 0 .5.0 0 t 0.23 1.968 0.750 1.000 1.250 1.500 1.750 0 2.000 ao 2.250 2.500 2.750 Unit Weight Cohesion Water Safety Factor 0 0.000 0.250 0 .5.0 0 2.681 0.750 1.000 1.250 1.500 1.750 0 2.000 ao 2.250 2.500 / 2.750 Unit Weight Cohesion Water Material Name Color Strength Type phi Ru Safety Factor 0 0.000 0.250 0 .5.0 0 t 0.23 1.491 0.750 1.000 1.250 1.500 1.750 0 2.000 ao 2.250 2.500 2.750 Unit Weight Cohesion Water Material Name Color Strength Type phi Surface Ru