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Exhibit_13_Geotech_Report
UPDATE TO GEOTECHNICAL ENGINEERING REPORT PROPOSED AFFORDABLE HOUSING DEVELOPMENT SUNSET GARDENS 2900 NORTHEAST 10TH STREET RENTON, WASHINGTON KING COUNTY PARCEL # 7227900075 PREPARED FOR: RENTON HOUSING AUTHORITY AND SUNSET GARDENS LLLP BY: OTTO ROSENAU & ASSOCIATES, INC. ORA JOB NO. 20-0569, REPORT NO. 1 OTTO ROSENAU & ASSOCIATES, INC. Geotechnical Engineering, Construction Inspection & Materials Testing PLANNING DIVISION 5/17/21 MHerrera RECEIVED DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Exhibit 13DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 TABLE OF CONTENTS 1. INTRODUCTION.................................................................................................................... 1 2. PROJECT DESCRIPTION ..................................................................................................... 1 3. SCOPE OF SERVICES.......................................................................................................... 1 4. SURFACE CONDITIONS ....................................................................................................... 2 5. SITE CHARACTERIZATION .................................................................................................. 3 6. SUBSURFACE CONDITIONS ............................................................................................... 3 6.1 Fill Materials ................................................................................................................... 3 6.2 Recessional Outwash Deposits ...................................................................................... 3 6.3 Groundwater Condition ................................................................................................... 4 7. LABORATORY TESTING ...................................................................................................... 4 8. DISCUSSION ......................................................................................................................... 4 9. CONCLUSIONS AND RECOMMENDATIONS ....................................................................... 4 9.1 General .......................................................................................................................... 4 9.2 Seismic Considerations .................................................................................................. 5 9.3 Foundation Systems ....................................................................................................... 6 9.3.1 Conventional Foundation System ........................................................................... 6 9.3.2 Driven Pin Pile Foundations: .................................................................................. 7 9.4 Concrete Slabs-On-Grade .............................................................................................. 8 9.5 Below-Grade Walls, Retaining Walls, and Temporary Shoring Walls .............................. 9 9.6 Temporary Excavation and Shoring.............................................................................. 10 9.6.1 Temporary Excavations ....................................................................................... 10 9.6.2 Temporary Soldier Pile and Lagging Shoring ....................................................... 10 9.7 Onsite Infiltration .......................................................................................................... 12 9.8 Earthwork ..................................................................................................................... 12 9.8.1 Foundation and Slab Subgrade Preparation ........................................................ 12 9.8.2 Structural Fill – Material, Placement and Compaction .......................................... 12 9.8.3 Erosion and Sedimentation Control ..................................................................... 13 9.9 Drainage....................................................................................................................... 14 9.9.1 Dewatering .......................................................................................................... 14 9.9.2 Below-Grade Wall Drainage ................................................................................ 14 10. REPORT LIMITATIONS ..................................................................................................... 14 11. REFERENCE ..................................................................................................................... 15 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 REPORT FIGURES Figure 1 - Vicinity Map Figure 2 - Site Plan Figure 3 - Geologic Map Figure 4 – Lateral Earth Pressure on Temporary Shoring Wall Figure 5 – Lateral Earth Pressure on Wall Due to Line Load Figure 6 – Lateral Earth Pressure on Wall Due to Strip Load APPENDIX A – EXPLORATIONS Boring Log Notes ................................................................................................................... A-1 Unified Soil Classification System .......................................................................................... A-3 Boring Logs ............................................................................................................................ A-4 APPENDIX B – LABORATORY TESTING Particle Size Distribution Results ........................................................................................... B-1 APPENDIX C – RESULTS OF THE REMI SURVEY Results of the ReMi Survey .................................................................................................... C-1 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 UPDATE TO GEOTECHNICAL ENGINEERING REPORT PROPOSED AFFORDABLE HOUSING DEVELOPMENT SUNSET GARDENS 2900 NORTHEAST 10TH STREET RENTON, WASHINGTON KING COUNTY PARCEL #7227900075 PREPARED FOR RENTON HOUSING AUTHORITY AND SUNSET GARDENS LLLP BY OTTO ROSENAU & ASSOCIATES, INC. APRIL 16, 2021 1. INTRODUCTION This updated report presents the results of our geotechnical engineering services for the proposed development to be located at 2900 Northeast 10th Street in Renton, Washington (King County Parcel # 7227900075). The approximate location of the site is shown on the Vicinity Map, Figure 1. 2. PROJECT DESCRIPTION We understand that proposed development planned for the site will be a seventy-six (76) unit residential complex over a commercial space and podium parking. The proposed building will consist of four (4) stories and in a L-shape configuration with a terraced area located in the central portion of the site. Also, it is our understanding that the current Renton Housing Authority’s Headquarters building will be demolished during the construction of the new development. 3. SCOPE OF SERVICES The scope of services included a reconnaissance of the site by a geotechnical engineer, a review of geologic literature, the completion of a geophysical evaluation using refraction micro-tremor profile (ReMi DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 2 of 15 Survey), and the witnessing of the completion of two (2) exploratory borings at the approximate locations shown on the attached Site Plan, Figure 2. The geotechnical engineering services were performed by Otto Rosenau and Associates, Inc. (ORA) to provide the following information: • A summary of the observed soil and groundwater conditions, • An evaluation of the existing site conditions, • A review of available geologic information, • A geophysical evaluation using a ReMi survey for determining the measured shear-wave velocity sounding of the underlying soils, • Seismic design considerations including liquefaction potential, • Suitable foundation systems with estimated settlements, • Allowable bearing capacity for conventional foundation systems, • Recommendations for deep foundation such as pin piles, • Lateral earth pressures and friction coefficients, • Recommendations for temporary cut slopes and temporary shoring, • Consideration of the site soils for infiltration, • Influence of groundwater on the proposed development, and • Site preparation and earthwork. 4. SURFACE CONDITIONS The site consists of an irregular-shaped parcel that with an area of approximately 55,757 square feet (1.28 acres). This site is bounded by Northeast 10th Street to the south and southwest; Index Avenue Northeast to the west, northwest, and north; and Jefferson Avenue Northeast to the southeast, east, northeast, and north. The existing office building is located in the southeast portion of the site. An asphalt parking and drive areas are located west and north of the existing building. A rockery wall, approximately 3 to 7 feet in height, is located along the southeast side of the site. See the Site Plan, Figure 2, showing the locations of the existing structures located at the site. The topography of the site is slopes downward from the east and northeast side of the property (located along Jefferson Avenue Northeast) with approximate elevations ranging from 365 to 370 feet (NAVD 88) to an approximate elevation of 357 feet (NAVD 88), located at the southwest corner of the property or near the intersection of Northeast 10th Street and Index Avenue Northeast. The perimeter of the site contains typical commercial landscaping that generally consists of trees and landscaping mulch. DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 3 of 15 5. SITE CHARACTERIZATION We reviewed the State of Washington Department of Natural Resource’s online “Washington Interactive Geologic Map” at https://geologyportal.dnr.wa.gov. The soils at and near the site are mapped as “Pleistocene age, recessional stratified drift outwash deposits” (Qpa) and “Pleistocene age, ground moraine or glacial till deposits” (Qgt). The recessional stratified drift outwash deposits (Qpa) generally consist of well-sorted sand and gravel deposits with sandy pebble and cobble gravel in the eastern most terraces, grades to interbedded sand and pebble gravel in the Renton area and to sand at the north edge of the quadrangle. The ground moraine or glacial till deposits (Qgt) generally consist of compact, coherent, unsorted mixture of sand, silt, clay, and gravel; commonly termed as hard pan. The till deposits are nearly impermeable and relatively difficult to excavate, but relatively stable in cut slopes. See the attached Geologic Map, Figure 3 for the location of the mapped soils. 6. SUBSURFACE CONDITIONS The subsurface soil and groundwater conditions at the site were evaluated by completing two (2) exploratory borings. The borings were completed using skid steer, rubber-tracked, hollow-stem auger drilling equipment to a maximum depth of approximately 61½ feet below the existing ground surface on August 27, 2020. The approximate locations of the borings are shown on the attached Site Plan, Figure 2. The details and explanations of the borings are presented on pages A-1 to A-8 of Appendix A - Explorations. In general, the soils encountered in the exploratory borings that was conducted at the sites can be divided into two soil units – fill materials and recessional outwash deposits. The following is a description of the characteristics of each soil units encountered. 6.1 Fill Materials Approximately 4 to 6 inches of fill materials were encountered in the exploratory borings underlying the 2 to 3½ inches of asphalt pavement. The fill materials generally consist of light brown, SAND with gravel. The fill material generally has a loose to medium dense consistency and in a moist condition. 6.2 Recessional Outwash Deposits The recessional outwash deposits were encountered in our exploratory borings underlying the fill material to maximum explored depth of 61½ feet below adjacent ground surface. The recessional outwash deposits generally consist of light brown, medium to fine SAND with silt (SP-SM) varying amounts of gravel. The recessional outwash deposits generally have a loose to very dense consistency and in a moist condition. DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 4 of 15 6.3 Groundwater Condition Groundwater was not encountered in any of our explorations. The actual groundwater levels at the sites are expected to fluctuate with precipitation levels and seasonally. We do not expect that groundwater will adversely affect the proposed renovations to be located at the sites. 7. LABORATORY TESTING We performed moisture content determinations on samples collected during our exploratory borings. The result of the moisture content determination is presented on the boring logs on pages A-4 to A-8 of Appendix A - Explorations. The particle size distribution or grain size analysis results are presented on pages B-1 and B-2 of Appendix B – Laboratory Testing. 8. DISCUSSION The engineering recommendations and advice presented in this report have been made in accordance with generally accepted geotechnical engineering practices in the area and are based on our understanding of the geology of the area and on our experience with similar projects. Project conditions, regarding type and location of structures and foundation loads, can change and subsurface conditions are not always similar to those encountered during the subsurface exploration. Therefore, if discrepancies are noticed, the geotechnical engineer must be contacted for review and for possible revision of the recommendations. 9. CONCLUSIONS AND RECOMMENDATIONS 9.1 General Based on the conditions of the underlying soils that were encountered during the exploratory borings and the configuration of the proposed development, we recommend that the foundation elements of the western portion of the proposed building be supported by conventional foundation system that bear directly on properly compacted structural fill materials that overly dense, outwash deposits. The southeast portion of the proposed building be supported by driven pin piles that bear into the underlying dense to very dense outwash deposits (encountered approximately 15 to 20 feet below existing ground surface). The area where the proposed building is going to be supported by conventional foundations, needs to be overexcavated approximately 7 to 15 feet below the existing grade to the underlying dense outwash deposits. The recommendations for the conventional footings are presented in the “Conventional Foundation” section of this report. The recommendations for temporary excavation and shoring are presented in the DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 5 of 15 “Temporary Excavation and Shoring” section of this report. The recommendations for the overexcavation of the area with the conventional foundation system are presented in the “Foundation and Slab Subgrade Preparation” of this report. The recommendations for the driven pin piles are present in the “Driven Pin Pile Foundation System” section of this report. 9.2 Seismic Considerations The seismic design of structures in the City of Renton is governed by the requirements of the 2018 edition of the International Building Code (IBC) and ASCE/SEI 7-16. A ReMi survey was performed along the northwest side of the site on April 7, 2021, by Atlas Technical Consultants. The results of the ReMi geophysical survey indicated that a measured average characteristic site shear-wave velocity down to a depth of approximately 100 feet below ground surface is 1243 feet per second. Based on the measured average shear-wave velocity of the underlying soils, we recommend that the site soils be categorized as Site Class C for design purposes. The results of the ReMi survey are presented in Appendix C – Results of the ReMi Survey of the updated report. Risk-targeted Maximum Considered Earthquake (MCER) ground motion response accelerations for this are based on the maps in the IBC (Figures 1613.3.1(1) and 1613.3.1(2)) for 0.2-second and 1-second spectral response accelerations on a bedrock site. The values for SS and S1 are spectral accelerations (SRA) for a maximum considered earthquake event with a 2,475 year return period, or a 2 percent probability of exceedance in 50 years. The values recommended for use in this updated report were obtained from the Structural Engineers Association of California (SEAOC) and California’s Office of Statewide Health Planning and Development (OSHPD) website at (http://seismicmaps.org). The input parameters used with this website were the latitude and longitude for the project site (47.4996° N, 122.1789° W). The following table presents recommended values from the 2015 IBC and ASCE 7-16 “Minimum Design Loads and Associated Criteria for Buildings and Other Structures” for seismic design: RECOMMENDED SEISMIC DESIGN PARAMETERS Risk Category II Site Soil Class C SS, g 1.426 S1, g 0.488 Site Coefficient, Fa 1.2 Site Coefficient, Fv 1.5 SMS, g 1.711 SM1, g 0.731 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 6 of 15 RECOMMENDED SEISMIC DESIGN PARAMETERS SDS, g 1.141 SD1, g 0.488 Liquefaction may be defined as the sudden loss of strength of soil as the soil is subjected to a rapid cyclic loading, such as during an earthquake. The mechanism that allows this to occur is that excess pore water pressures are generated between the soil particles. This excess pore water pressure reduces the frictional contact between the soil particles and reduces the shear strength of the soil. If the earthquake is of large magnitude and duration the soil can begin to behave more like a liquid than solid and “liquefy”. In order for liquefaction to occur several conditions must typically be present, these include the following: • Saturated soil. • Fine to medium sand matrix containing less than about 10 percent fines (soil that can pass a No. 200 sieve. • Very loose to medium dense soil conditions. This is usually defined as soils that have N- values of 15 or less. Based on the observed subsurface soil and groundwater (none encountered) conditions encountered at the site and our understanding of geologic conditions present at the site, it is our opinion that the potential for the occurrence of liquefaction at the project site is low. The sites are located approximately 1.5 to 2.0 miles southwest of the southern traces of the Seattle Fault and the project site is underlain with glacially-consolidated soils, as a result, it is our opinion that the risk of surface rupture from faulting, or due to lateral spread is low. 9.3 Foundation Systems 9.3.1 Conventional Foundation System: It is our opinion that the foundation elements for the western portion of the proposed development can be satisfactorily supported on the conventional footings that bear directly onto properly compacted structural fill materials overlying the dense outwash deposits. We recommend that foundation elements be sized using the following criteria, which includes a factor of safety of at least 3. We recommend that an allowable bearing value of 2,000 pounds per square foot (psf) should be used for the design of conventional foundation system that bear on properly compacted structural fill materials overlying dense, native outwash deposits. We recommend that the minimum width of continuous footings be at least 2 feet, and that the minimum width of column footings be 3 feet. All foundation elements shall be embedded at least 18 inches below DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 7 of 15 the lowest adjacent finished grade for frost protection, and the top of all interior foundation elements shall be embedded at least 12 inches below the top of slab elevation. The above-listed allowable bearing capacities may be increased by one-third for wind and seismic loads when using Allowable Stress Design (ASD). We anticipate that that maximum post-construction settlements will be less than three-quarters (3/4) of an inch and differential settlements will be less than one-half (1/2) of an inch between comparably loaded column footings or along a 25-foot long section of continuous wall footing. We anticipate that the majority of the foundation settlement will occur as load is applied. Passive resistance should be evaluated using an equivalent fluid pressure of 295 pounds per cubic foot (pcf) where foundation elements are cast on medium dense to dense, native soils or properly compacted structural fill materials. This value of passive pressure includes a factor of safety of 1.5. An allowable coefficient of friction between footings and bearing soils of 0.4 may be used to resist lateral foundation loads. This value includes a factor of safety of about 1.5. 9.3.2 Driven Pin Pile Foundations: The foundation system for the southeast portion of the proposed development will be supported on driven pin piles that consist of galvanized, 3-, 4-, or 6-inch diameter steel pipe that are to be driven to refusal. All piles must be driven to penetrate the through the underlying loose to medium dense, outwash deposits into the underlying dense to very dense, outwash deposits (encountered in our borings at approximate depths of 15 to 20 feet below existing ground surface). Once the required embedment into dense to very dense, outwash deposits is achieved, the driving criteria for the piles must be satisfied for at least 3 consecutive cycles. The driving criteria will be based on the pile and hammer selection made for the project by the contractor. Actual driving depths will be determined once pile installations begin and may be significantly greater than the anticipated depths depending on the encountered site conditions. Adjacent sections of pipe shall be joined with tight-fitting slip-joint connectors or by welding. Please refer to the following table for specific recommendations for the different pile sizes. DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 8 of 15 Pile Diameter (inches) Pile Schedule Minimum Hammer Size (pounds) Allowable Downward Pile Capacity (pounds) Refusal Criteria (inches per second) 3 40 600 (hydraulic) 12,000 12 4 40 850 (hydraulic) 20,000 16 6 40 2000 (hydraulic) 30,000 10 The refusal criteria for 3-, 4-, and 6-inch pin piles other than as listed above will be determined by the geotechnical engineer once final hammer selection is completed. If the refusal criteria cannot be achieved a pile load test may be required to evaluate the actual load carrying capacity of the installed piling. Pile load tests should be performed in accordance with the ASTM D1183 test procedure using the Quick Procedure. The IBC requires continuous monitoring of piling installation and load testing by the geotechnical engineer or his representative. An existing rockery wall is located along the eastern portion of the site and should be monitored during the installations of the driven pin piles. 9.4 Concrete Slabs-On-Grade Structural fill can be placed at future slab-on-grade areas only after the complete removal of any unsuitable soils. All fill placed below future slabs on grade must be placed as structural fill. We recommend that a 2-foot fill blanket of structural fill be placed under the concrete slab-on-grade located where the foundation elements are going to be supported on driven piles. The slabs-on-grade should bear on a minimum of 6-inch-thick, free-draining, clean, crushed, gravel base. A robust vapor retarder such as 10-mil polyethylene sheeting shall be included beneath the slab to minimize transmission of moisture through the concrete floor. A minimum, two-inch thick layer of clean sand with less than 3 percent fines may be placed on top of the polyethylene sheeting to protect the sheeting and to enhance the curing of the concrete slabs. The sand must not be saturated at the time of concrete placement in order to enhance concrete curing. If slabs–on-grade are being planned at heated areas, a more robust vapor barrier should be utilized, since the conditioned air in the heated areas will tend to draw moisture from the near-surface groundwater that is present beneath the site. ORA can provide recommendations for vapor barriers upon request. DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 9 of 15 9.5 Below-Grade Walls, Retaining Walls, and Temporary Shoring Walls The below-grade foundation walls for this project must be designed as retaining walls. Lateral earth pressures for design of permanent retaining walls and temporary shoring walls with no hydrostatic pressures or other surcharge loads, may be calculated using the following equivalent fluid densities in pounds per cubic foot (pcf): Level Back Slope Condition Active (unrestrained): Compacted granular soils or native soils against wall 36 pcf. Level Back Slope Condition Active (restrained): Compacted granular soils or native soils against wall 56 pcf. Passive: Embedded Portions of Foundation Elements 295 pcf. See the attached Figure 4 titled “Lateral Earth Pressures on Temporary Shoring Wall” showing the representation of the lateral earth pressures. “H” represents the height of the excavation and “D” represents the depth of the embedment of the piles for the permanent or temporary shoring walls. Lateral pressures exerted on the temporary shoring walls due to the presence of point loads and strip footing loads at the back of the wall are presented on attached Figure 5 titled “Lateral Earth Pressure on Wall Due to Line Load” and Figure 6 titled “Lateral Earther Pressure on Wall Due to Strip Load.” Active soil pressures on cantilevered temporary shoring walls may be assumed to act on the pile spacing above the base of the excavation and the diameter of the grouted hole below the base of the excavation. Passive pressures may be assumed to act on 2.5 times the grouted hole diameter for drilled soldier piles, and on 2.5 times the H-pile flange width for driven soldier piles. No factor of safety has been applied to the active pressure values listed above. A factor of safety of about 1.5 has been applied to the passive pressure value listed above. The geotechnical engineer should be contacted to determine appropriate lateral earth pressures for situations not described above. Seismic earth pressures were estimated using the Mononobe-Okabe pseudo-static method. We recommend that seismic earth pressures be estimated using a rectangular pressure distribution equal to 7H, where H is the height of the retained soil behind the wall. A total soil unit weight of 125 pounds per cubic foot should be used in design of any permanent below- grade wall, retaining structures, or temporary shoring walls. DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 10 of 15 Passive resistance should be evaluated using an equivalent fluid pressure of 295 pounds per cubic foot (pcf) where foundation elements are cast on structural fill and backfilled on both sides with structural fill compacted to at least 95 percent of maximum dry density (MDD). This value of passive pressure includes a factor of safety of 1.5. An allowable coefficient of friction between footings and bearing soils of 0.4 may be used to resist lateral foundation loads. This value includes a factor of safety of about 1.5. 9.6 Temporary Excavation and Shoring At time of the issuance of this report, the anticipated depths of the excavations for the construction of the proposed development is unknown. 9.6.1 Temporary Excavations: We recommend that the inclination of the temporary cut slopes be no greater than 1.5H:1V (horizontal to vertical) for the loose to dense, fill materials and native, sandy deposits. An ORA representative should evaluate the exposed soil conditions at the time of construction to verify that the recommended slope inclinations are appropriate for the conditions being encountered. In addition, the configuration for temporary cut slope inclinations may need to be modified during the course of construction if site conditions change. All temporary cut slopes and excavations must comply with the provisions of Washington Administrative Code (WAC) Chapter 296-155, Part N, “Excavation, Trenching and Shoring.” The contractor performing the work has the primary responsibility for protection of workers and adjacent improvements. 9.6.2 Temporary Soldier Pile and Lagging Shoring: If the temporary slopes for the overexcavation are not feasible due to job site constraints where temporary cut slopes would encroach on to the adjacent sidewalks and roadways, then temporary soldier pile and lagging shoring should be installed in those areas (along the north and west sides of the site). Soldier piles typically consist of driven steel wide flange (WF) sections, or pipe sections, or drilled holes into which a WF section, or pipe is placed and then the hole is backfilled with either structural concrete or lean concrete. The soldier piles are typically spaced 5 to 8 feet on center. As the construction of the wall proceeds, the timber lagging, or steel plate lagging is placed between the soldier piles. The voids between the lagging and face of the steep slope are to be filled with compacted native soils, a sand slurry mixture, or controlled density fill (CDF) to minimize the risk of soil movement. The excavation of the soldier pile shafts must be completed in a manner to prevent the loss of adjacent soils. The holes excavated for the soldier piles should provide a minimum of 3 inches of clearance between the sides and bottom of the hole and the nearest portion of a properly-centered soldier pile. The soldier piles should extend to a depth that is required for shear and moment equilibrium of the wall. DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 11 of 15 Lateral earth pressures should be estimated using the attached Figure 4 titled “Lateral Earth Pressure on Temporary Shoring Wall.” The holes for drilled soldier piles may be backfilled with structural concrete or CDF at depths below the bottom of the toe of the steep slope. The remaining portion of the hole should be backfilled with controlled density fill (CDF) with no more than 1.5 sacks of cement per cubic yard of concrete for ease of excavation at the time of lagging installation. We recommend that the timber lagging be pressure-treated and be sized for a uniform pressure equal to about two-thirds of the design maximum active lateral pressure. This pressure reduction is based on a maximum center to center soldier pile spacing of 8 feet. The timber lagging should be no less than 4 inches in thickness and should be installed with spaces no less than ¼” between lagging boards to allow drainage. The spaces between boards should be made with appropriately sized, flat metal shims. Any voids behind the lagging boards should be backfilled with sand/water slurry or other free-draining material as soon as possible to prevent the loss of soil and settlement behind the wall. Native soils which consist of sandy soils are suitable for use as backfill behind the shoring wall. Based on the observed soil conditions, we anticipate that drilled holes for soldier piles will have a short stand up time without collapse of unsupported hole sidewalls. If caving soils are encountered in the excavations for the soldier piles, the contractor must be prepared to fully-case the excavations or propose and implement an alternative method of advancing the shaft excavations without causing a loss of adjacent soil. If caving soils are encountered and no casing or other means of preventing the loss of adjacent soil is available, the hole must be backfilled immediately. The holes for soldier piles must be fully backfilled to the existing ground surface by the end of each work shift, and no hole may be left open for longer than 24 hours. We do not anticipate significant water seepage into the excavations for drilled soldier piles. If more than 12 inches of water is present at the base of the excavation for the soldier piles the concrete must be placed using a tremie pipe at the base of the excavation to displace the water upwards as the concrete is pumped. The tip of the tremie pipe must remain embedded at least 3 feet into the concrete as it is being placed to ensure that water or slurry is being displaced above the concrete. The installation of all soldier piles is to be witnessed by the geotechnical engineer or his representative. The City of Renton typically requires that the installation of all soldier piles be monitored by the geotechnical engineer or his representative. DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 12 of 15 9.7 Onsite Infiltration Based on the underlying soils encountered during our exploratory borings, we believe that onsite infiltration for surface water drainage could be feasible due to their granular nature (medium to fine SAND) and loose to medium dense condition. 9.8 Earthwork These recommendations presented in this report are predicated on fulfillment of the following earthwork recommendations. 9.8.1 Foundation and Slab Subgrade Preparation: All concrete slabs, undocumented fill, organic debris, and old topsoil must be removed from all foundation element locations and future slab areas. If construction activities are to be performed during periods of wet weather, we recommend that the exposed foundation subgrade soils be protected with 4 to 6 inches of thoroughly compacted 1-1/4 inch minus crushed rock, quarry spalls, controlled density fill (CDF), or a rat slab of structural concrete. The exposed subgrade soil conditions should be verified by a representative of ORA to ensure that the soils are adequately prepared to provide the required support. In the areas where the proposed building is going to be supported by conventional foundations, this area needs to be overexcavated down approximately 7 to 15 feet below adjacent ground surface to the dense outwash deposits. The exposed subgrade soils should be recompacted to a firm and unyielding condition prior to placement of structural fill materials. The exposed subgrade soil conditions should be verified by a representative of ORA prior to placement of the structural fill material to ensure that the soils are adequately prepared to provide the required support. The concrete slab-on-grade areas with the foundation elements being supported by driven pin piles should be overexcavated down to provide a fill blanket of approximately 2 feet thick below concrete slabs. The area should be moisture conditioned and recompacted to 95 percent of the maximum dry density as determined by modified Proctor test (ASTM D1557). 9.8.2 Structural Fill – Material, Placement and Compaction: The onsite sandy soils or granular import can be used as structural fill. All fill and backfill materials should be placed in relatively horizontal loose lifts, not exceeding 10 inches in thickness, and compacted to at least 95 percent of the maximum dry density (MDD) as determined by the modified Proctor test (ASTM D1557). If manually-operated equipment such as a jumping jack compactor is used, the thickness of each loose lift should be no greater than 6 inches. Light vibratory plate compactors are not suitable for the compaction of structural fill. Soils consisting of clay, silt, peat or containing deleterious matter are generally not suitable for use as structural fill. Structural fill material and the onsite sandy soils should be approved by ORA prior to use. The DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 13 of 15 following table summarizes our recommendations of fill material and compaction requirements for various types of aggregates. Intended Use Specification Compaction Requirements Structural fill below foundation elements Gravel backfill for Foundations (WSDOT 9-03.9) and the onsite sandy soils. Each lift must be compacted to 95 percent of MDD per ASTM D1557 test procedure. Fill behind below- grade walls (outside of zone of wall drainage material) Gravel Backfill for Walls (WSDOT 9- 03.12(2)) Fill placed within 5 feet of below- grade walls or retaining walls shall be compacted with manually-operated compaction equipment. Fill placed at depths greater than 2 feet below finish subgrade elevation compacted to 90 percent of MDD. Fill placed at depths within 2 feet of finish subgrade elevation must be compacted to 95 percent of MDD, if the area will be supporting pavements or roadway. Fill behind below- grade walls at zone of wall drainage material Gravel Backfill for Drains (WSDOT 9- 03.12(4)) No compaction until at least 18 inches of cover is present above perforated drain pipe. Each subsequent 12-inch lift lightly compacted using manual compaction equipment. Capillary break Material below slabs- on-grade Clean, 5/8-inch crushed rock Each lift must be compacted to a firm and unyielding condition over the firm subgrade soils. Structural fill to be compacted to 95 percent of MDD should be moisture-conditioned to within three (3) percent of optimum moisture. Structural fill to be compacted to 90 percent of MDD should be moisture- conditioned to within six (6) percent of optimum moisture content. Placement of frozen soils or placement of soils on frozen ground should not be attempted. 9.8.3 Erosion and Sedimentation Control: The migration of sediments from the site must be installed and controlled in accordance with City of Renton requirements. We recommend that the following minimum erosion control measures be employed at the site: DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 14 of 15 • Provide silt fencing around the construction area to delineate the construction limits. No construction or soil disturbance should take place outside of the construction limits. • Stockpiled soil at the site should be kept to a minimum. Any stockpiled soils should be covered with carefully secured plastic sheeting. • Catch basin socks should be installed in nearby catch basins located downhill of the work area that could be impacted by construction activities. • All sediment and soil should be removed from adjacent pavements at the end of each day of construction activities. • Periodic inspection of the adequacy and condition of the installed erosion control measures by a geotechnical engineer or an experienced representative assigned by the geotechnical engineer. Additional erosion control measures may be required as construction progresses. 9.9 Drainage 9.9.1 Dewatering: Based on our review of the proposed development, we do not anticipate that groundwater will be encountered during construction of the proposed structure. If groundwater or seepage is encountered during construction, we anticipate that dewatering could be satisfactorily completed by routing water through ditches to a low spot or sump in the excavation. We recommend that the sump depths be set to lower groundwater to at least 2 feet below the base of excavation elevation. Runoff water and groundwater collected in temporary excavations should be removed as soon as possible and should be discharged to a location approved by the City of Renton, in accordance with City of Renton requirements. 9.9.2 Below-Grade Wall Drainage: Good drainage is an integral part of the performance of earth- supported structures such as foundations and retaining walls. New drainage will need to be provided between the exposed soil at the excavations along the new foundation walls. We anticipate that this may be most easily accomplished using a composite drainage panel such as CCW MiraDrain 6000, or an approved equivalent. The composite drainage panel is installed with the filter fabric side against the soil and the plastic, dimpled board facing the interior of the foundation. Water collected by composite drainage panel will need to be routed to the interior of the foundation using a PVC pipe fitting made by the drainage panel manufacturer that is designed for the system being used and passes through the foundation wall or footing into an interior tight line collection system below the future subfloor. The collected water then may be routed to the outfall of the existing foundation drain system, which may require the use of a sump and sump pump, if gravity flow is not feasible. 10. REPORT LIMITATIONS The recommendations presented in this report are for the exclusive use by Renton Housing Authority and Sunset Gardens LLLP for the proposed development to be located at 2900 Northeast 10th Street in DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Sunset Gardens Affordable Housing Development ORA Project No.: 20-0569 April 16, 2021 Page 15 of 15 Renton, Washington. The recommendations are based on readily-available geologic literature, two (2) explorations that were completed on August 27, 2020, and the geophysical evaluation that was performed on site on April 7, 2021 by Atlas Technical Consultants. The recommendations of this report are not transferable to any other site. If there are any revisions to the plans, or if deviations from the subsurface conditions noted in this report are encountered during construction, Otto Rosenau & Associates, Inc. (ORA) should be notified immediately to determine whether changes to the design recommendations are required. 11. REFERENCE “Washington Interactive Geologic Map” provided by the State of Washington Department of Natural Resource’s at https://www.dnr.wa.gov/geology/. DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 © 2020 Microsoft Corporation © 2020 HERE PROJECT SITE 2900 NE 10th STREET VICINITY MAP OTTO ROSENAU & ASSOCIATES, INC. Date: August 20, 2020 Location: 2900 NE 10th Street, Renton, Washington For: Renton Housing Authority & Sunset Gardens LLLP Project Name: Sunset Garden LLLP Affordable Housing Development Reference: ©2020 Microsoft Corporation Bing Mapping Service. Figure: 1 ORA Project No.: 20-0569 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 2900 NE 10TH ST. B-1 B-2 N E 1 0 t h S T R E E TINDEX AVE NEJEFFERSON AVE NESITE PLAN OTTO ROSENAU & ASSOCIATES, INC. Note: The location of all features shown is approximate. Reference: King County Geographic Information System (KCGIS) Figure: 2 0' 12.5'50' 25'100' SCALE 1" = 50' LEGEND B-1 & 2 Borings exploration completed by ORA on 08/27/2020 Date: August 20, 2020 Location: 2900 NE 10th Street, Renton, Washington For: Renton Housing Authority & Sunset Gardens LLLP Project Name: Sunset Garden LLLP Affordable Housing Development ORA Project No.: 20-0569 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Qgt Qpa Qga Qgt Qu SUNSET GARDENS LLLP AFFORDABLE HOUSING DEVELOPMENT 2900 NE 10th STREET GEOLOGIC MAP OTTO ROSENAU & ASSOCIATES, INC. Figure: 3Date: August 20, 2020 Location: 2900 NE 10th Street, Renton, Washington For: Renton Housing Authority & Sunset Gardens LLLP Project Name: Sunset Garden LLLP Affordable Housing Development ORA Project No.: 20-0569 LEGEND: Qgt - Continental Glacial Till, Fraser Age (Pleistocene) Qpa - Continental Glacial Drift, Fraser Age (Pleistocene) or Recessional Stratified Drift Glacial Fluvial Deposits Qu - Un-differentiated Deposits (Pleistocene) Note: The location of all features shown is approximate. Reference: Washington Interactive Geologic Map online mapping service by Washington State Department of Natural Resources DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Ignore contribution of upper 2 feet for passive resistance for shoring design Earth Pressure (Active Case) Wall NOTES: 1. Active pressure acting on the lagging may be reduced by 33% due to soil arching. 2. Active pressure above the base of the excavation acts on a width equal to pile spacing. 3. Active pressure below the base of the excavation acts on a width equal to the diameter of the grouted hole for drilled soldier piles, or equal to the flange width of the H-pile for driven piles. 4. Passive pressure below the base of the excavation acts on a width equal to 2.5 times the diameter of the grouted hole for drilled soldier piles, or equal to 2.5 times the flange width of the H-pile for driven piles. The ultimate passive pressures calculated using the recommended values above should be reduced with a factor of safety equal to 1.5 to determine the allowable passive pressure. 47 (D) . 205 (D-2) 47 (H)H, where H is greater than 11' typcially D 12" Earth Pressure (Passive Case) LATERAL EARTH PRESSURE ON TEMPORARY SHORING WALL OTTO ROSENAU & ASSOCIATES, INC. Figure: 4Date: August 20, 2020 Location: 2900 NE 10th Street, Renton, Washington For: Renton Housing Authority & Sunset Gardens LLLP Project Name: Sunset Garden LLLP Affordable Housing Development ORA Project No.: 20-0569 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 H Wall Base of Excavation x = mH Line Load, Q Z = nH s = Horizontal Pressure due to Q at depth Z ELEVATION VIEW For m ≤ 0.4: s = Q H 0.20n (0.16 + n )2H For m ≥ 0.4:s = Q H 1.28m n (m + n )H 2 2 22 2 Resultant P = 0.55QH L Resultant P = 0.64 Q (m +1)H 2 L L L L NOTES: A line loading condition can arise from a narrow strip footing parallel to the wall. Units: Length - feet, Force - pounds, pressure - pounds per square foot. L P = Resultant ForceH H LATERAL EARTH PRESSURE ON WALL DUE TO LINE LOAD NOTE: Figure based on Figure 11 on page 7.2-74 of NAVFAC DM-7.02 Foundations and Earth Structures dated September 1986. OTTO ROSENAU & ASSOCIATES, INC. Figure: 5Date: August 20, 2020 Location: 2900 NE 10th Street, Renton, Washington For: Renton Housing Authority & Sunset Gardens LLLP Project Name: Sunset Garden LLLP Affordable Housing Development ORA Project No.: 20-0569 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 NOTES: A strip loading condition can arise from a large column footing, isolated surcharge load, or adjacent traffic loads. Units: Length - feet, Force - pounds, pressure - pounds per square foot. Wall s = (2q p ) (b -sinbcos2a)H q / unit area (psf) b a b a 0.5a Base of Excavation s = Horizontal Pressure due to strip load 'q' applied over width 'a' at depth ZH LATERAL EARTH PRESSURE ON WALL DUE TO STRIP LOAD NOTE: Figure based on Figure 5.17 on page 280 of Principles of Foundation Engineering 2nd Edition dated 1990 by Braja M. Das. OTTO ROSENAU & ASSOCIATES, INC. Figure: 6Date: August 20, 2020 Location: 2900 NE 10th Street, Renton, Washington For: Renton Housing Authority & Sunset Gardens LLLP Project Name: Sunset Garden LLLP Affordable Housing Development ORA Project No.: 20-0569 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 APPENDIX A EXPLORATIONS DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 BORING LOG NOTES These notes and boring logs are intended for use with this geotechnical report for the purposes and project described therein. The boring logs depict ORA’s interpretation of subsurface conditions at the location of the boring on the date noted. Subsurface conditions may vary, and groundwater levels may change because of seasonal or numerous other factors. Accordingly, the boring logs should not be made a part of construction plans or be used to define construction conditions. The approximate locations of the borings are shown on the Site Plan. The borings were located in the field by measuring from existing site features. “Hole Size” refers to the approximate diameter of auger used. “Sample Number and Type” refers to the sampling method and equipment used during exploration where: • “SS” indicates split-spoon sampler with 1-3/8” inside diameter and 2” outside diameter. “N-Values” refer to the Standard Penetration Test which records number of blows from a 140-pound hammer falling 30 inches required to advance a standard sampler eighteen inches. The blow counts required to drive the sampler through each 6 -inch interval is recorded. The number of blows to drive the sampler for the last 12 inches of driving are added together and is considered to be the N-Value. The N-Value is presented in parentheses on the boring logs. The actual blow count values for each 6-inch interval is also presented. If the sample is driven less than 6 inches for a given interval, the actual distance driven is recorded. “Moisture Content (MC)” refers to the moisture content of the soil exp ressed in percent by weight of dry sample as determined in the laboratory. “Grain Size (GS)” refers to a grain size distribution analysis completed in general accordance with the ASTM D422 test procedure. “Fines” is an estimate of the portion of a soil sample passing a No. 200 sieve as determined using the ASTM D422 test procedure. “Description and USCS Classification” refer to the materials encountered in the boring. The descriptions and classifications are generally based on visual examination in the field and laboratory. Where noted, laboratory tests were performed to determine the soil classification. The terms and symbols used in the boring logs are in general accordance with the Unified Soil Classification System. Laboratory tests are performed in general accordance with applicable procedures described by the American Society for Testing and Materials. A-1 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 BORING LOG NOTES (continued) “” Indicates location of groundwater at the time noted. TERMS for RELATIVE DENSITY of NON-COHESIVE SOIL Term Standard Penetration Resistance “N” Very Loose 4 or less Loose 5 to 10 Medium Dense 11 to 30 Dense 31 to 50 Very Dense Over 50 blows/foot TERMS for RELATIVE CONSISTENCY of COHESIVE SOIL Term Unconfined Compressive Strength Very Soft 0 to 0.25 tons/square-foot (tsf) Soft 0.25 to 0.50 tsf Medium Stiff 0.50 to 1.00 tsf Stiff 1.00 to 2.00 tsf Very Stiff 2.00 to 4.00 tsf Hard Over 4.00 tsf DEFINITION of MATERIAL by DIAMETER of PARTICLE Boulder 8-inches+ Cobble 3 to 8 inches Gravel 3 inches to 5mm Coarse Sand 5mm to 0.6mm Medium Sand 0.6mm to 0.2mm Fine Sand 0.2mm to 0.074mm Silt 0.074mm to 0.005mm Clay less than 0.005mm A-2 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 GW GM GC SW SP SC ML CL OL CH OH PT SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS TYPICAL GRAPH LETTER DESCRIPTIONS COARSE GRAINED SOILS MORE THAN 50% OF MATERIAL IS LARGER THAN NO. 200 SIEVE SIZE FINE GRAINED SOILS MORE THAN 50% OF MATERIAL IS SMALLER THAN NO. 200 SIEVE SIZE GRAVEL AND GRAVELLY SOILS MORE THAN 50% OF COARSE FRACTION RETAINED ON NO. 4 SIEVE SAND AND SANDY SOILS MORE THAN 50% OF COARSE FRACTION PASSING ON NO. 4 SIEVE SILTS AND CLAYS SILTS AND CLAYS CLEAN GRAVELS (LITTLE OR NO FINES) GRAVELS WITH FINES (MORE THAN 12% FINES) CLEAN SANDS (LITTLE OR NO FINES) SANDS WITH FINES (MORE THAN 12% FINES) LIQUID LIMIT LESS THAN 50 LIQUID LIMIT GREATER THAN 50 WELL-GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES POORLY-GRADED GRAVELS, GRAVEL GP - SAND MIXTURES, LITTLE OR NO FINES SILTY GRAVELS, GRAVEL - SAND - SILT MIXTURES CLAYEY GRAVELS, GRAVEL - SAND - CLAY MIXTURES WELL-GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES POORLY-GRADED SANDS, GRAVELLY SAND, LITTLE OR NO FINES SM SILTY SANDS, SAND - SILT MIXTURES CLAYEY SANDS, SAND - CLAY MIXTURES INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY INORGANIC SILTS, MICACEOUS OR MH DIATOMACEOUS FINE SAND OR SILTY SOILS INORGANIC CLAYS OF HIGH PLASTICITY ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS HIGHLY ORGANIC SOILS PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS NOTE: FINES ARE MATERIALS PASSING THE NO. 200 SIEVE. COARSE GRAINED SOILS RECEIVE DUAL SYMBOLS IF THEY CONTAIN BETWEEN 5% AND 12% FINES. FINE GRAINED SOILS RECEIVE DUAL SYMBOLS IF THEIR LIMITS PLOT LEFT OF THE "A" LINE WITH A PLASTICITY INDEX (PI) OF 4% TO 7%. A-3 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 SS 1 SS 2 SS 3 SS 4 SS 5 SS 6 SS 7 50 89 100 67 100 100 83 6-9-12 (21) 3-1-2 (3) 6-9-11 (20) 6-10-12 (22) 6-11-12 (23) 6-10-11 (21) 10-17-21 (38) MC=3% MC=10% MC=6% MC=6% MC=6% MC=6% MC=8% Fines=9% GS SP- SM SP- SM SP- SM SP- SM SP- SM SP- SM SP- SM SP- SM Asphalt pavement 4 to 6 inches of light brown, SAND with gravel, moist (fill) Medium dense, light brown, medium to fine SAND with Silt and some gravel, moist. (Recessional Outwash) Medium dense, light brown, medium to fine SAND with Silt and some gravel, moist. (Recessional Outwash) Very loose, light brown, medium to fine SAND with Silt and some gravel, moist. (Recessional Outwash) No gravel at 6' Medium dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Medium dense, light brown, medium to fine SAND with Silt , moist. (Recessional Outwash) Medium dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Medium dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Dense, light brown, medium to fine SAND with trace Silt, moist. (Recessional Outwash) NOTES Split spoon, 140# hammer, rope and cathead. N47.7998 W122.1790 GROUND ELEVATION 364 ft NAVD88 LOGGED BY Scott Hoobler, P.E. DRILLING METHOD Hollow Stem Auger (Skidsteer Track Rig)AT TIME OF DRILLING --- AT END OF DRILLING --- AFTER DRILLING --- HOLE SIZE 7" DRILLING CONTRACTOR Geologic Drill Partners GROUND WATER LEVELS: CHECKED BY Scott Hoobler, P.E. DATE STARTED 8/27/20 COMPLETED 8/27/20 DEPTH(ft)0 5 10 15 20 25 (Continued Next Page)SAMPLE TYPENUMBERPAGE 1 OF 2 BORING NUMBER B-1 CLIENT Renton Housing Authority & Sunset Gardens LLLP PROJECT NUMBER 20-0569 PROJECT NAME Sunset Gardens LLLP Affordable Housing Development PROJECT LOCATION 2900 NE 10th Street, Renton GENERAL BH / TP / WELL SUNSET GARDENS.GPJ GINT US.GDT 9/14/20OTTO ROSENAU & ASSOCIATES, INC. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 RECOVERY %BLOWCOUNTS(N VALUE)TESTS U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION A-4 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 SS 8 SS 9 89 61 10-15-17 (32) 13-14-14 (28) MC=9% MC=8% SP- SM SP- SM Dense, light brown, medium to fine SAND with trace Silt, moist. (Recessional Outwash) Medium dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Bottom of hole at 31.5 feet. 31.5DEPTH(ft)25 30 SAMPLE TYPENUMBERPAGE 2 OF 2 BORING NUMBER B-1 CLIENT Renton Housing Authority & Sunset Gardens LLLP PROJECT NUMBER 20-0569 PROJECT NAME Sunset Gardens LLLP Affordable Housing Development PROJECT LOCATION 2900 NE 10th Street, Renton GENERAL BH / TP / WELL SUNSET GARDENS.GPJ GINT US.GDT 9/14/20OTTO ROSENAU & ASSOCIATES, INC. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 RECOVERY %BLOWCOUNTS(N VALUE)TESTS U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION A-5 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 SS 1 SS 2 SS 3 SS 4 SS 5 SS 6 SS 7 67 83 100 100 100 100 100 3-2-4 (6) 4-6-7 (13) 6-10-10 (20) 7-11-13 (24) 6-9-12 (21) 7-13-17 (30) 11-15-16 (31) MC=7% MC=6% MC=6% MC=6% Fines=7% GS MC=6% MC=7% MC=8% SP- SM SP- SM SP- SM SP- SM SP- SM SP- SM SP- SM SP- SM Asphalt pavement 4 to 6 inches of light brown, SAND with Gravel, moist (Fill) Loose, light brown, medium to fine SAND with trace silt and gravel, moist. (Recessional Outwash) Medium dense, light brown, medium to fine SAND with Silt and trace gravel, moist. (Recessional Outwash) Medium dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Medium dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Medium dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Medium dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) NOTES Split spoon, 140# hammer, rope and cathead. N47.7996 W122.1793 GROUND ELEVATION 360 ft NAVD88 LOGGED BY Scott Hoobler, P.E. DRILLING METHOD Hollow Stem Auger (Skidsteer Track Rig)AT TIME OF DRILLING --- AT END OF DRILLING --- AFTER DRILLING --- HOLE SIZE 7" DRILLING CONTRACTOR Geologic Drill Partners GROUND WATER LEVELS: CHECKED BY Scott Hoobler, P.E. DATE STARTED 8/27/20 COMPLETED 8/27/20 DEPTH(ft)0 5 10 15 20 25 (Continued Next Page)SAMPLE TYPENUMBERPAGE 1 OF 3 BORING NUMBER B-2 CLIENT Renton Housing Authority & Sunset Gardens LLLP PROJECT NUMBER 20-0569 PROJECT NAME Sunset Gardens LLLP Affordable Housing Development PROJECT LOCATION 2900 NE 10th Street, Renton GENERAL BH / TP / WELL SUNSET GARDENS.GPJ GINT US.GDT 9/15/20OTTO ROSENAU & ASSOCIATES, INC. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 RECOVERY %BLOWCOUNTS(N VALUE)TESTS U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION A-6 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 SS 8 SS 9 SS 10 SS 11 SS 12 SS 13 100 100 89 81 100 100 9-14-15 (29) 13-21-21 (42) 10-14-17 (31) 9-16-20 (36) 11-19-27 (46) 9-15-26 (41) MC=5% MC=5% MC=7% MC=8% MC=6% MC=10% SP- SM SP- SM SP- SM SP- SM SP- SM SP- SM Medium dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Dense, light brown, medium to fine SAND with Silt, moist. (Recessional Outwash) Dense, light brown, fine SAND with Silt, moist. (Recessional Outwash) Dense, light brown, fine SAND with Silt, moist. (Recessional Outwash) Very dense at 52'DEPTH(ft)25 30 35 40 45 50 (Continued Next Page)SAMPLE TYPENUMBERPAGE 2 OF 3 BORING NUMBER B-2 CLIENT Renton Housing Authority & Sunset Gardens LLLP PROJECT NUMBER 20-0569 PROJECT NAME Sunset Gardens LLLP Affordable Housing Development PROJECT LOCATION 2900 NE 10th Street, Renton GENERAL BH / TP / WELL SUNSET GARDENS.GPJ GINT US.GDT 9/15/20OTTO ROSENAU & ASSOCIATES, INC. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 RECOVERY %BLOWCOUNTS(N VALUE)TESTS U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION A-7 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 SS 14 SS 15 100 100 25-28-29 (57) 15-15-17 (32) MC=9% MC=6% SP- SM SP- SM Dense, light brown, fine SAND with Silt, moist. (Recessional Outwash) Dense, light brown, fine SAND with Silt, moist. (Recessional Outwash) Bottom of hole at 61.5 feet. 61.5DEPTH(ft)55 60 SAMPLE TYPENUMBERPAGE 3 OF 3 BORING NUMBER B-2 CLIENT Renton Housing Authority & Sunset Gardens LLLP PROJECT NUMBER 20-0569 PROJECT NAME Sunset Gardens LLLP Affordable Housing Development PROJECT LOCATION 2900 NE 10th Street, Renton GENERAL BH / TP / WELL SUNSET GARDENS.GPJ GINT US.GDT 9/15/20OTTO ROSENAU & ASSOCIATES, INC. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 RECOVERY %BLOWCOUNTS(N VALUE)TESTS U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION A-8 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 APPENDIX B LABORATORY TESTING DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 This report applies to the items tested or reported and is the exclusive property of Otto Rosenau & Associates, Inc.Reproduction of this report, except in full, without written permission from our firm is strictly prohibited.Classification: ASTM D2487 Natural Moisture: ASTM D2216Particle Size Distribution Report PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 0.0 0.0 0.0 1.5 89.6 8.96 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200Test Results (ASTM D 422 & ASTM D 1140) Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Sample Number: B-1, Sample 7 Depth: 20' - 21.5' Client: Project: Project No:Figure ORA sample ID: 8498 Gray poorly graded sand with silt 2 1 1/4 1 3/4 5/8 1/2 3/8 1/4 #4 #8 #10 #40 #100 #200 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 98.5 15.4 8.9 SP-SM A-3 0.3742 0.3509 0.2649 0.2379 0.1886 0.1438 0.0847 3.13 1.59 Test equipment ID: Set 5 Was sample soaked? Not required As received MC: 7.9% 8/27/2020 8/31/2020 Andy Duong Scott Hoobler Professional Engineer 8/27/2020 Renton Housing Authority & Sunset Garden LLLP Sunset Gardens LLLP Affordable Housing Development 2900 NE 10th Street, Renton 20-0569 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) OTTO ROSENAU & ASSOCIATES, INC.8498, B-1 B-1 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 This report applies to the items tested or reported and is the exclusive property of Otto Rosenau & Associates, Inc.Reproduction of this report, except in full, without written permission from our firm is strictly prohibited.Classification: ASTM D2487 Natural Moisture: ASTM D2216Particle Size Distribution Report PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 0.0 0.0 0.1 5.9 87.0 7.06 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200Test Results (ASTM D 422 & ASTM D 1140) Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Sample Number: B-2, Sample 4 Depth: 10' - 11.5' Client: Project: Project No:Figure ORA sample ID: 8498 Gray poorly graded sand with silt 2 1 1/4 1 3/4 5/8 1/2 3/8 1/4 #4 #8 #10 #40 #100 #200 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 99.9 99.9 94.0 11.4 7.0 SP-SM A-3 0.3997 0.3730 0.2793 0.2507 0.1998 0.1612 0.1207 2.31 1.18 Test equipment ID: Set 5 Was sample soaked? Not required As received MC: 5.8% 8/27/2020 8/31/2020 Andy Duong Scott Hoobler Professional Engineer 8/27/2020 Renton Housing Authority & Sunset Garden LLLP Sunset Gardens LLLP Affordable Housing Development 2900 NE 10th Street, Renton 20-0569 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) OTTO ROSENAU & ASSOCIATES, INC.8498, B-2 B-2 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 APPENDIX C RESULTS OF THE REMI SURVEY DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Page | 1 15115 SW Sequoia Parkway, Suite 130 Portland, Oregon 97224 (503) 836-7022 | oneatlas.com April 9, 2021 Atlas No. 421008SWG Report No. 1 MR. SCOTT HOOBLER, PE OTTO ROSENAU & ASSOCIATES, INC. 6747 MARTIN LUTHER KING JR WAY S SEATTLE, WA 98118 Subject: Geophysical Evaluation Sunset Gardens LLLP Affordable Housing Development ReMi Study Renton, Washington Dear Mr. Hoobler: In accordance with your authorization, Atlas Technical Consultants has performed a geophysical evaluation pertaining to the Sunset Gardens LLLP Affordable Housing Development ReMi Study in Renton, Washington (Figure 1). The purpose of our evaluation was to develop a one- dimensional (1-D) shear-wave velocity profile to be used for design and construction at the project site. This report presents the survey methodology, equipment used, analysis, and findings from our study. Our services were conducted on April 7, 2021. Our scope of services for the project included the performance of one refraction microtremor (ReMi) profile (RL-1) at your designated area of the project site (Figure 2). The ReMi technique uses recorded surface waves (specifically Rayleigh waves) that are contained in background noise to develop a 1-D shear-wave velocity sounding of the study area down to a depth, in this case, of approximately 130 feet below ground surface (bgs). The depth of exploration is dependent on the length of the line and the frequency content of the background noise. The results of the ReMi method are displayed as a 1-D profile which represents the average condition across the length of the line. The ReMi method does not require an increase of material velocity with depth; therefore, low velocity zones (velocity inversions) are detectable with the ReMi method. Our ReMi evaluation included the use of a 24-channel Geometrics Geode seismograph and 24, 4.5-Hz vertical component geophones. The geophones were spaced 10 feet apart for a total line length of 230 feet at each line. A total of 20 records, 32 seconds in duration each at each line, were recorded and then downloaded to a field computer. The data were later processed using Surface Plus 9.1 - Advanced Surface Wave Processing Software (Geogiga Technology Corp., 2020), which uses the refraction microtremor method (Louie, 2001), and other surface wave analysis methods. The program generates phase-velocity dispersion curves for each record and provides an interactive dispersion modeling tool where the users determine the best fitting model. DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Atlas No. 421008SWG Report No. 1 Page | 2 The result is a 1-D shear-wave velocity model of the site with roughly 85 to 95 percent accuracy. Figure 2 depicts the general site conditions in the study area. Table 1 and Figure 3 present the results from our evaluation. Based on our analysis of the collected data, the average characteristic site shear-wave velocity down to a depth of 100 feet bgs is 1243 feet per second. These values both correspond to IBC seismic Site Class 'C' (IBC, 2018). It should be noted the ReMi results represent the average condition across the length of the line. Table 1 – ReMi Results Line No. Depth (feet) Shear Wave Velocity (feet/second) RL-1 (SW-NE) 0 - 5 621 5 - 15 840 15 - 26 1164 26 - 40 1224 40 - 56 1405 56 - 75 1456 75 - 88 1529 88 - 127 1639 127 - 130 1670 The field evaluation and geophysical analyses presented in this report have been conducted in general accordance with current practice and the standard of care exercised by consultants performing similar tasks in the project area. No warranty, express or implied, is made regarding the conclusions and opinions presented in this report. There is no evaluation detailed enough to reveal every subsurface condition. Variations may exist and conditions not observed or described in this report may be present. Uncertainties relative to subsurface conditions can be reduced through additional subsurface exploration. Additional subsurface evaluating will be performed upon request. This document is intended to be used only in its entirety. No portions of the document, by itself, is designed to completely represent any aspect of the project described herein. Atlas should be contacted if the reader requires additional information or has questions regarding the content, interpretations presented, or completeness of this document. This report is intended exclusively for use by the client. Any use of or reuse of the findings, conclusions, and/or recommendations of this report by parties other than the client is undertaken at said parties’ sole risk. DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 Atlas No. 421008SWG Report No. 1 Page | 3 We appreciate the opportunity to be of service on this project. Should you have questions related to this report, please contact the undersigned at your convenience. Respectfully submitted, Atlas Technical Consultants, LLC Andrew S. Baird Patrick F. Lehrmann, P.G. (CA, OR), P.Gp.(CA) Project Geophysicist Principal Geologist/Geophysicist ERC:ASB:PFLds Attachments: Figure 1 – Site Location Map Figure 2 – Seismic Line Location Map Figure 3 – ReMi Results (RL-1) Distribution: Scott Hoobler at scott@ottorosenau.com DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95 DocuSign Envelope ID: 79C68332-54C2-4835-BBF5-4E8BA45C5C95