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Home My WebLink AboutEx_12_Krazan Report.pdf & A S S O C I A T E S, I N C. GEOTECHNICAL ENGINEERING • ENVIRONMENTAL ENGINEERING CONSTRUCTION TESTING & INSPECTION Offices Serving the Western United States 825 Center Street, Ste. A, Tacoma, Washington 98409 (253) 939-2500 • Fax (253) 939-2556 July 9, 2020 KA Project No. 062-20013 Abbey Road Group Land Development Services Company, LLC P.O. Box 1224 Puyallup, WA 98371 Attn: Mr. Phil Becker Email: Phil.Becker@AbbeyRoadGroup.com Tel: (253) 435-3699 (ext. 104) Reference: Limited Geotechnical Engineering Investigation Letter Mei Lin View Short Plat 1833 NE 12th Street Renton, WA Dear Mr. Becker, This letter presents the findings and recommendations of our limited geotechnical engineering investigation for the Mei Lin View Short Plat project located at 1833 NE 12th Street in Renton, Washington. Introduction and Scope The site consists of one parcel covering an area of approximately 0.94 acres. We understand that the site will be subdivided into three (3) buildings lots. Lots 1 and 2 will be located in the easternmost portion of the site and will cover an area of approximately 5,000 square feet. Lot 3 will be the remainder of the site to the west, and will cover an area of approximately 31,581 square feet. The proposed development on Lot 3 is planned near the top of an existing west facing steep slope, which is classified as a Geological Hazardous Area per the City of Renton Municipal Code. We understand that a geotechnical report titled “Subsurface Exploration and Limited Geotechnical Engineering Services – Proposed Rankin Short Plat”, prepared by Bergquist Engineering Services (BES), dated October 17, 2017 was prepared for the site. The City of Renton requested a peer review of the BES geotechnical report by GeoEngineers Inc. We were provided with GeoEngineers’ review letter dated May 11, 2020. We were also provided with the project plans titled “Mei Lin View”, prepared by Abbey Road Group Land Development Services Company, LLC, dated February 5, 2020. We have been requested to prepare this geotechnical engineering letter to address GeoEngineers’ review comments and provide recommendations as needed for development of Lot 3. Our scope of services was performed in general accordance with our proposal for this project, dated May 28, 2020 (Proposal Number G202027WAT) and included the following: KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 2 of 16 Krazan & Associates, Inc. Offices Serving the Western United States • Exploration of the subsurface soil and groundwater conditions by conducting approximately two (2) geotechnical borings using a subcontracted drill rig under the direction of a Krazan geotechnical engineer; • A site plan showing the geotechnical boring locations, and comprehensive boring logs including soil stratification and classification, and groundwater levels where applicable; • Geotechnical engineering evaluation and opinions regarding slope stability; • Recommended foundation type(s) for future anticipated structure, if needed; • Recommendations for structural fill materials, placement, and compaction, if needed; • Recommendations for suitability of onsite soils as structural fill, if needed; • Recommendations for temporary excavations, if needed; and • Recommendations for site drainage and erosion control. Geologic Setting The site lies within the central Puget Lowland. The lowland is part of a regional north-south trending trough that extends from southwestern British Columbia to near Eugene, Oregon. North of Olympia, Washington, this lowland is glacially carved, with a depositional and erosional history including at least four separate glacial advances and retreats. The Puget Lowland is bounded to the west by the Olympic Mountains and to the east by the Cascade Range. The lowland is filled with glacial and nonglacial sediments. The “Geologic Map of King County,” prepared by Derek B. Booth, Kathy A. Troost, and Aaron P. Wisher (ESS, University of Washington, and GeoMapNW - March 2007) indicates that the site is underlain by the Vashon subglacial till (Qvt) and nearby contact with Vashon recessional outwash deposits (Qvr). In general, the subglacial till is described as compact diamict of clay, silt, sand, gravel, cobbles and boulders, containing sub-rounded to well-rounded clasts, glacially transported and deposited at the base of continental ice sheet. Vashon recessional outwash is described as sand and gravel deposits with lenses and thin beds of silt and fine sand. Our explorations generally encountered undocumented fill overlying the native glacial soils. Subsurface Exploration and Condition Two (2) exploratory soil borings were completed to evaluate the subsurface soil and groundwater conditions near the top of the slope on Lot 3. The soil borings were completed on June 4, 2020. An engineer from Krazan and Associates was present during the explorations, examined the soil and geologic conditions encountered, obtained samples of the different soil types, and maintained logs of the explorations. The approximate locations of the soil explorations are shown on the Site Plan in Figure 2. KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 3 of 16 Krazan & Associates, Inc. Offices Serving the Western United States The borings were advanced using a subcontracted track-mounted drill rig equipped with hollow stem augers. Soil samples were obtained by using the Standard Penetration Test (SPT) as described in ASTM Test Method D1586. The Standard Penetration Test and sampling method consists of driving a standard 2-inch outside- diameter, split barrel sampler into the subsoil with a 140-pound hammer free falling a vertical distance of 30 inches. The summation of hammer blows required to drive the sampler the final 12 inches of an 18-inch long sample interval is defined as the Standard Penetration Resistance, or N-value. The blow count is presented graphically on the boring logs attached to this letter. The resistance, or N-value, provides a measure of the relative density of granular soils or of the relative consistency of cohesive soils. Representative samples of the subsurface soils encountered in the geotechnical explorations were collected, sealed in plastic bags, and transported to our laboratory for testing. The soils encountered in the explorations were visually classified in general accordance with the Unified Soil Classification System (USCS). The laboratory test results are included on the soil boring logs, where applicable, and graphically presented with this letter. The soil borings, designated B-1 and B-2, were advanced to depths of approximately 31.0 feet below the existing ground surface (bgs). Both of our soil borings generally encountered undocumented fill overlying the native glacial soils. A general description of the subsurface conditions is provided below. Detailed descriptions of the soils encountered in each of the borings are presented in the boring logs attached to this letter. Organic Topsoil/Duff: Roughly 8-inches and 9-inches of organic topsoil/duff was encountered in borings B-1 and B-2, respectively. Undocumented Fill: Below the organic topsoil/duff, the soil borings encountered moist, brown silty sand with gravel, which extended to roughly 11.0 feet bgs in boring B-1 and 13.5 feet bgs in boring B-2. We interpreted this material to be undocumented fill. SPT N-values ranged from 3 to 19 blows per foot (bpf) which indicate the undocumented fill to be in a very loose to medium dense relative density. The moisture content of the fill ranged between 4.3 to 13.5 percent. Native Glacial Soils: Beneath the undocumented fill, the soil borings generally encountered moist, medium dense, brownish gray silty sand with gravel, which extended to roughly 15.0 feet bgs in B-1 and 20.0 feet bgs in B-2. We interpreted the medium dense, brownish gray silty sand with gravel to be native weathered till. Underlying the weathered till, the borings generally encountered moist, very dense, gray silty sand with gravel extending to the maximum explored depth of the borings at about 31.0 feet bgs. We interpreted the very dense, gray silty sand with gravel to be glacial till. N-values of 23 and 25 bpf were recorded in the weathered till, while N-values in the underlying very dense glacial till ranged from 51 bpf to an equivalent of greater than 100 bpf. Groundwater Observations: Groundwater seepage was not encountered in our soil borings at the time of exploration. It should be recognized that groundwater elevations may fluctuate with time. The groundwater level will be dependent upon seasonal precipitation, irrigation, land use, and climatic conditions, as well as other factors. Therefore, groundwater levels at the time of the field investigation may be different from those KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 4 of 16 Krazan & Associates, Inc. Offices Serving the Western United States encountered during the construction phase of the project. The evaluation of such factors is beyond the scope of this report. Conclusions and Recommendations We have reviewed the review comments by GeoEngineers Inc. for the BES geotechnical report. Our responses to the review comments and our associated recommendations are addressed in the following pages. Slope Stability Analyses Slope stability analyses were performed using the commercially available GeoStudio Slope/W computer program. The west-facing slope (section A-A’) on Lot 3 was modelled with three (3) soil layers, identified as Undocumented Fill, Native Weathered Till, and Native Glacial Till. Soil strength parameters used in our analyses for each layer were estimated based on the results of our exploratory borings, laboratory testing, and published soil parameter correlations, and are presented in the following table. The pseudo-static method was used for the slope stability analyses to estimate the Factor of Safety (FS) under seismic conditions. The seismic coefficient used in a pseudo-static analysis is typically taken to be 1/2 of the peak ground acceleration (PGA) that the site is estimated to experience during the design earthquake. A seismic coefficient of 0.3g was used for the pseudo-static analysis. Soil Parameters for Slope Stability Analyses Material Description Estimated Effective Angle of Internal Friction (degrees) Estimated Effective Cohesion (psf) Estimated Soil Unit Weight (Moist) (pcf) Very loose to medium dense silty sand with gravel (Undocumented Fill) 26 0 115 Medium dense silty sand with gravel (Native Weathered Till) 34 100 125 Dense to very dense silty sand with trace gravel (Native Glacial Till) 40 100 135 KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 5 of 16 Krazan & Associates, Inc. Offices Serving the Western United States The results of slope stability analyses are expressed as a Factor of Safety, FS, against displacement failure. The FS is the ratio of resisting forces to driving forces. A FS of 1.0 represents an equilibrium state, i.e. resisting forces are equal to driving forces in the modelled slope. A FS of less than 1.0 indicates failure of the modelled slope. Typically, a minimum FS of 1.5 for static conditions and 1.1 for seismic (pseudo-static) conditions are considered adequate in standard local engineering practice. A FS between 1.0 and 1.5 under static conditions or less than 1.1 under seismic conditions are not adequate due to the uncertainties in the modeling process. A lower FS for seismic conditions than for static conditions is considered adequate as the probability of occurrence of the seismic conditions is relatively low. The results of the slope stability analyses for the static and seismic condition are presented in the following tables. A graphical presentation of the results of the static and seismic slope stability analyses are presented in the attached Figures 4 and 5, respectively. Slope Stability Results (Static Condition) Calculated Factor of Safety Factor of Safety Required Section A-A’ Global Stability 2.84 1.5 Slope Stability Results (Seismic Condition) Calculated Factor of Safety Factor of Safety Required Section A-A’ Global Stability 1.34 1.1 The project plans show minimal grading at Lot 3. Based on this, the pre-development (existing) and post- development conditions are basically the same, and separate slope stability analyses were not conducted. Based on our communication with Abbey Road, it is our understanding that the proposed buildable area will be roughly 6,000 square feet in the northeast corner of Lot 3, as highlighted on the Site Plan in Figure 2. The remainder of Lot 3, including the west facing slope, will be considered a sensitive tract or easement. Based on the extent of the proposed development on Lot 3, our field exploration, and slope stability analyses, it is our opinion that the proposed development will not adversely impact the existing western steep slopes, or increase the threat of the geological hazard to adjacent or abutting properties. Uncertainties related to building along the top of steep slopes are typically addressed by the use of building setbacks. The purpose of the setback is to establish a “buffer zone” between the structure and the top of the slope so that ample space is allowed for normal slope recession during a reasonable life span of the structure. In a general sense, the greater the setback, the lower the risk of slope failures to impact the structure. From a geological standpoint, the setback dimension is based on the slope’s physical characteristics, such as slope height, surface angle, material composition, and hydrology. Other factors such as historical slope activity, rate of regression, and the type and desired life span of the development are important considerations as well. The current plans do not show specific building locations. However, we understand that a 30-foot horizontal distance, consisting of a 15-foot set-back and a 15-foot buffer zone, from the top of the western slope will be KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 6 of 16 Krazan & Associates, Inc. Offices Serving the Western United States maintained and the potential building/development will be constructed outside of this total 30-foot zone. Based on our slope stability analyses, it is our opinion that the 30-foot restrictive zone (15-foot setback and 15-foot buffer) should be adequate. We recommend that minimal (if needed) or no disturbance of the existing vegetation be allowed within the setback zone. Circumstances where minimal disturbance of the setback area would be considered allowable include short-term activities to install new utilities for the proposed development. The areas near the slope were heavily vegetated with brambles, tall grass, and bamboo-like knotweed during our site visit, and some cutting of the brambles and knotweed were required to access the boring locations. The underlying grass and roots were not removed during the clearing activities for the boring locations. We did observe some debris, consisting of abandoned electronic parts, bucket of oil, and bag of trash, dumped on the ground surface at one location. However, we did not observe any indications of below grade debris during our field exploration. If any debris or spoils are noted during the development of the site, then we recommend that they be removed from the setback area. Any disturbed soils resulting from removal of debris or spoils should be rolled to a firm condition and sealed to limit moisture penetration. Any setback areas disturbed during construction, such as for installation of a new utility, should be planted with vegetation as soon as possible to reduce the potential for erosion. Replacement of vegetation in the setback areas should be performed in accordance with the City of Renton Municipal Code. No material of any kind should be placed on the slope or be allowed to reach the slope, such as excavation spoils, lawn clippings and other yard waste, trash, or soil stockpiles. Under no circumstances should water be allowed to concentrate on the steep slopes. Response to GeoEngineers Comments Comment 1) Analysis should be provided that directly demonstrates that the following review criteria can be met: (1) Per Renton Municipal Code Section 4-3-050F.2.a.ii. (a) “The proposal will not increase the threat of the geological hazard to adjacent or abutting properties beyond pre-development conditions”. In our opinion this can be demonstrated by comparing the calculated stability of the existing conditions to the calculated stability of the proposed conditions with the inclusion of typical or design building loads as appropriate. And, (2) Per Section 4-3-050F.2.a.ii. (c) “The development can be safely accommodated on the site.” In our opinion this can be demonstrated by evaluating slope failure surfaces that would affect structures located within the recommended building setbacks. Typically factors of safety greater than 1.5 for static conditions and greater than 1.05 for seismic conditions are considered appropriate. The licensed geotechnical professional preparing the analysis should have some discretion in determining appropriate factors of safety, but must ultimately provide a statement that, in their professional opinion, the criteria have been met. Based on our communications with the design team, it is our understanding that minimal grading is being proposed on Lot 3. All of the proposed development will be at least 30 feet horizontal distance from the top of the slope. Based on our field exploration and slope stability analyses, it is our opinion that the proposed development will not increase the threat of the geologic hazard to adjacent or abutting properties beyond pre-development conditions, and the proposed development can safely be accommodated at Lot 3. Please refer to the slope stability and foundations sections of this letter. KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 7 of 16 Krazan & Associates, Inc. Offices Serving the Western United States Comment 2) The report states that a seismic coefficient of 0.2g was applied to the project. It is not clear what seismic design level (i.e., return period) and site class this is based on or if a reduction was included. A seismic event with a 2 percent probability of exceedance in 50 years (about 2,475-year return period in accordance with the International Building Code [IBC]) is typically used to analyze slopes and potential failures that will impact inhabited structures. For a pseudo-static analysis, one-half of the Peak Ground Acceleration (PGA) is typically used based on the assumption that some permanent slope movement is acceptable. We referred to the Applied Technology Council (ATC) website, ASCE 7-10, and 2015 IBC to obtain seismic design parameters, which are provided in the seismic design section of this letter. We have used a PGA of 0.594 having a 2 percent probability of being exceeded in 50 years, for Site Class D. A seismic coefficient of 0.30g was used for the pseudo-static analysis to evaluate the factor of safety (FS) under seismic conditions. Comment 3) It is unclear between the text and the stability analyses provided in Appendix B, which soil parameters are used for which subsurface unit and at what elevation these are applied (some apparent inconsistencies are noted below). We suggest providing a table within the text or appendix stating the elevations and parameters used to model each unit. Soil parameters used for our slope stability analyses are provided in the slope stability section of this letter and in the attached Figures 4 and 5. Comment 4) Some of the analyses are reported to use a cohesion of 100 pounds per square foot (psf) in “the uppermost soils to account for strength due to roots”. The analysis provided in the appendix appears to apply the 100 psf cohesion to units well over 10 feet deep, which is beyond what could be expected for significant root penetration. Inclusion of the effects of vegetation, over any extent, to maintain or develop slope stability could, at a minimum, require a Native Growth Protection Area per Renton Municipal Code. Additionally, inclusion of this strength over the entire surface of the site appears to be in contradiction with the recommendation in Section 6.3 Site Preparation that states, “The site should be stripped of all vegetation prior to construction.” Additional information should be provided justifying the magnitude and extent of the root strength and the apparent contradictions should be clarified or explained. We have neglected the effects of roots in our slope stability analyses. Cohesion is not assumed in the fill layer for our slope stability analyses. Comment 5) A case was analyzed that assumes the upper 12 feet of loose fill soils were replaced with structural fill with a friction angle of 40 degrees. Structural fill of this strength usually requires specific gradation and high compaction criteria and could also require use of an angular or crushed aggregate. This is inconsistent with a soil that will develop significant root penetration to develop the equivalent of 100 psf cohesion, which was also assumed. There are also some apparent inconsistencies between what is stated in the text and what is in the analyses provided in Appendix B. For example, the fill unit appears to have been analyzed with a friction angel of 38 degrees and there is one unit with a cohesion of 150 psf. Additional KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 8 of 16 Krazan & Associates, Inc. Offices Serving the Western United States information should be provided justifying the strength of the proposed fill and the apparent inconsistencies should be clarified or explained. For our slope stability analyses, we have assumed that undocumented fill will be left in-place and have used soil parameters based on the soil boring test results, soil classification correlations, and our observations of its current condition. Comment 6) It is stated in Section 6.1 Residential Foundations of the report that “The uppermost soils at this site are not suitable for support of conventional spread footings that are typically used for residential structures.” and that “deep foundations will likely be required”. The slope stability analysis considers a case where the upper loose fill is removed and replaced with structural fill and this section recommends deep foundations to support structures. It is unclear how the structures are proposed to be supported. If the future structure will be supported on structural fill after the removal of the existing fill, then the grading plan appears insufficient to address this level of earthwork. If the structure is supported on deep foundations or with a combination of deep foundations and slope stabilizing structures as suggested in the report, then these features should be considered when evaluating slope stability and evaluating if the construction of such structures will increase the threat of the geological hazard to adjacent or abutting properties. We are recommending that the potential structure on Lot 3 be supported on either a shallow foundation supported on structural fill extending to medium dense or firmer native glacial soils, or on a deep foundation system. Based on our slope stability analyses, and with the foundation loads being transferred to the underlying medium dense (shallow foundation) or dense to very dense (deep foundation) glacial soils, it is our opinion that the proposed structure will not adversely impact the existing western slope stability, or increase the threat of the geological hazard to adjacent or abutting properties. Seismic Design The 2015 International Building Code (IBC), Section 1613.3.2, refers to Chapter 20 of ASCE 7 for Site Class Definitions. It is our opinion that the overall soil profile corresponds to Site Class D as defined by Table 20.3-1 “Site Class Definitions,” according to the 2010 ASCE 7 Standard. Site Class D applies to a “stiff soil” profile. The seismic site class is based on a soil profile extending to a depth of 100 feet. The soil explorations on this site extended to a maximum depth of approximately 31.0 feet and this seismic site class designation is based on the assumption that dense to very dense conditions continue below the depth explored. We referred to the Applied Technology Council (ATC) website and 2015 IBC to obtain values for SS, SMS, SDS, S1, SM1, SD1, PGA, Fa, and Fv. The ATC website utilizes the most updated published data on seismic conditions from the United States Geological Survey. The seismic design parameters for this site are presented in the following table: KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 9 of 16 Krazan & Associates, Inc. Offices Serving the Western United States Seismic Design Parameters (Reference: 2015 IBC Section 1613.3.2, ASCE, and ATC) Seismic Item Value Site Coefficient Fa 1.0 Ss 1.440 SMS 1.440 SDS 0.960 Site Coefficient Fv 1.5 S1 0.541 SM1 0.812 SD1 0.541 PGA* 0.594 * 2 percent probability of being exceeded in 50 years Structural Fill Fill placed beneath foundations or other settlement-sensitive structures should be placed as structural fill. Structural fill, by definition, is placed in accordance with prescribed methods and standards, and is monitored by an experienced geotechnical professional. Based on the materials used, field monitoring procedures would include either visual observation for clean rock placement, or the performance of a representative number of in-place density tests to document the attainment of the desired degree of relative compaction. A representative of the geotechnical engineer should evaluate the subgrade prior to structural fill placement. The onsite soils may be suitable for re-use as structural fill, provided the soil is free of organic material and debris and it is within ± 2 percent of its optimum moisture content. If the native soils are stockpiled for later use as structural fill, the stockpiles should be covered to protect the soil from wet weather conditions. We recommend that a representative of Krazan & Associates be on site during the excavation work to determine which soils are suitable for placement as structural fill. Imported, all weather structural fill material should consist of well-graded gravel or a sand and gravel mixture with a maximum grain size of 3 inches and less than 5 percent fines (material passing the U.S. Standard No. 200 Sieve). Structural fill also can consist crushed rock, rock spalls, or Controlled Density Fill (CDF). All structural fill material should be submitted for approval to the geotechnical engineer at least 48 hours prior to delivery to the site. Granular fill soils should be placed in horizontal lifts not exceeding 8 inches in thickness prior to compaction, moisture-conditioned as necessary (moisture content of soil shall not vary by more than ±2 percent of optimum moisture), and the material should be compacted to at least 95 percent of the maximum dry density based on ASTM D1557 Test Method. In-place density tests should be performed on all structural KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 10 of 16 Krazan & Associates, Inc. Offices Serving the Western United States fill to document proper moisture content and adequate compaction. Additional lifts should not be placed if the previous lift did not meet the compaction requirements or if soil conditions are not considered stable. Foundations General: The proposed structure may be supported on a conventional spread foundation system bearing on the medium dense or firmer native soils or on structural fill extending to the medium dense or firmer native soils. Structural fill materials may include granular soils, rock spalls, or Control Density Fill (CDF). Based on our soil explorations, we interpreted the medium dense or firmer native load bearing soils in the potential building area to be approximately 11.0 to 13.5 feet below the existing grade. We recommend that we evaluate the foundation subgrade soils during construction to determine the consistency throughout the building pad. We have assumed column loads of 35,000 pounds and wall loads of 1,000 to 2,000 pounds per lineal foot (plf) for the soil bearing capacity and settlement analyses. We should be contacted to re-evaluate the potential settlement and the allowable bearing pressure, if the design loads vary significantly from these assumed values. Shallow Foundations: Conventional shallow spread footings supported on medium dense of firmer native soils, or on structural fill extending to the medium dense or firmer native soils, may be designed using an allowable soil bearing pressure of 2,500 pounds per square foot (psf) for dead plus live loads. This value may be increased by 1/3 for short duration loads such as wind or seismic loading. A representative of Krazan and Associates should evaluate the foundation bearing soil prior to the placement of forms or steel reinforcement and observe structural fill placement. Footings should have a minimum embedment depth of 18 inches below pad subgrade (soil grade) or adjacent exterior grade, whichever is lower. Footing widths should be based on the anticipated loads and allowable soil bearing pressure. Footings should have a minimum width of at least 12 inches regardless of load. All undocumented fill and loose or disturbed soils should be removed from the foundation excavations prior to placing concrete. Water should not be allowed to collect in the foundation excavations. Structural Fill in Footing Areas: If the structural fill consists of granular soils or rock spalls, then the foundation excavations would need to be widened on both sides of the footing a distance equal to one-half of the depth of the over-excavation below the bottom of the footing. Structural fill consisting of granular soils should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557. To reduce the volume of extra excavation needed for the footing trenches and to simplify structural fill placement, it may be practical to place Control Density Fill (CDF) to fill the deeper footing trenches to the planned footing subgrade elevations. If CDF is used, the trench may be excavated only slightly wider (6 inches wider on each side) than the footing. Potential Foundation Settlement: For foundations constructed as recommended, the total settlement is not expected to exceed 1-inch. Differential settlement should be less than ½-inch. Most settlement is expected to occur during construction, as the loads are applied. However, additional post-construction settlement may KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 11 of 16 Krazan & Associates, Inc. Offices Serving the Western United States occur if the foundation soils are flooded or saturated. It should be noted that the risk of liquefaction is considered low, given the composition and density of the native, onsite soils. Lateral Resistance: Resistance to lateral displacement can be computed using an allowable friction factor of 0.35 acting between the bases of foundations and the supporting subgrade soil. Lateral resistance for footings can alternatively be developed using an allowable equivalent fluid passive pressure of 250 pounds per cubic foot (pcf) acting against the appropriate vertical footing faces (neglecting the upper 12 inches). The allowable friction factor and allowable equivalent fluid passive pressure values include a factor of safety of 1.5. The frictional and passive resistance of the soil may be combined without reduction in determining the total lateral resistance. These values are based on footings founded on competent native soils or on structural fill extending to the competent native soils Foundation Drainage: Seasonal rainfall, water run-off, and the normal practice of watering trees and landscaping areas around the proposed structures, should not be permitted to flood and/or saturate foundation subgrade soils. To prevent the build-up of water within the footing areas, continuous footing drains (with cleanouts) should be provided at the base of the footings. The footing drains should consist of a minimum 4- inch diameter rigid perforated PVC pipe, sloped to drain, with perforations placed near the bottom and enveloped in all directions by washed rock and wrapped with filter fabric to limit the migration of silt and clay into the drain. Deep Foundations – Pin Piles: Alternatively, due to the presence of a deeper layer of undocumented fill, and the potential magnitude of total and differential settlements associated with this fill, a deep foundation system consisting of pin piles could be utilized to support the planned structural loads. Pin piles would also eliminate the need for over-excavation as the piles would be driven through the undocumented fill to transfer the building loads to the underlying dense native soils. Debris was not present in the undocumented fill encountered in our soil borings. However, undocumented fill may include debris and there is a possibility some piles may be obstructed. There should be contingencies in the budget and design for removal of obstructions and/or additional/relocated piles to replace piles that may be obstructed by debris in the fill. Below we provide the installation recommendations and allowable pile loads for 2-, 3-, and 4-inch diameter pipe piles. The pile capacities stated below are based on pile center to center spacing of at least 3 pile diameters to avoid group effects. For 2-inch diameter pipe piles driven to refusal using a hand-held, 90-pound jackhammer, we recommend a design axial compression capacity of three tons for each pile. The refusal criterion for this pile and hammer size is defined as less than one inch of pile penetration during 60 seconds of continuous driving. We recommend using extra strong (Schedule 80) galvanized steel pipe for the 2-inch diameter pipe piles. We recommend that the 3-inch diameter pipe piles be driven using a hydraulic hammer with a weight class of at least 850 lbs. For this pile diameter and hammer size, we recommend a design axial compression capacity KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 12 of 16 Krazan & Associates, Inc. Offices Serving the Western United States of six tons for each pile driven to refusal. The refusal criterion for this pile and hammer size is defined as less than one inch of pile penetration during 20 seconds of continuous driving. We recommend that the 4-inch diameter pipe piles be driven using a hydraulic hammer, with a weight class of at least 1,100 lbs. For this pile and hammer size, we recommend a design capacity of ten tons for each pile driven to refusal. The refusal criterion for this pile and hammer size is defined as less than one inch of pile penetration during 20 seconds of continuous driving. The above design capacities for the 3- and 4-inch diameter piles are based on theoretical numerical pile driving analysis. We recommend that 3 percent of the piles (minimum of one pile and up to five pile maximum) be load tested to verify the design values. We recommend that the piles be loaded to at least 200 percent of the design capacity, and that Krazan be retained to observe and evaluate the pile load test. A factor of safety of two could be used to reduce the ultimate capacity achieved from the pile load test to a design capacity. Actual pile load test procedures should be discussed with your contractor and Krazan prior to pile testing. We should be retained to review final plans, monitor installation of the piles, and evaluate pile refusal as well as pile load tests. Final pile depths should be expected to vary somewhat and will depend on the actual depth of the existing fill, and nature of the underlying competent soils and ground water conditions. The pin piles should penetrate a minimum of five feet into the competent native soil in order to develop the design capacity. Based on our field exploration, we would anticipate piles to extend roughly 16 to 20 feet below existing ground surface. Piles that do not meet this minimum embedment criterion or piles that are obstructed on debris in the fill should be rejected, and replacement piles should be driven after consulting with the structural engineer regarding the new pile locations. Due to the relatively small slenderness ratio of pin piles, maintaining pin pile confinement and lateral support is essential to preventing pile buckling. Pin piles should not stick above the finished ground surface. Vertically driven pin piles do not provide meaningful lateral capacity. However, battered piles can provide a lateral resistance component. The structural engineer should determine the degree of batter, and the number and location of battered piles, if required. The maximum degree of batter should not be greater than 1 Horizontal to 4 Vertical (1H:4V). Temporary Excavations The onsite soils have variable friction and cohesion strengths, therefore the safe angles to which these materials may be cut for temporary excavations is variable, as the soils may be prone to caving and slope failures in temporary excavations deeper than 4 feet. Temporary excavations in the competent native soils should be sloped no steeper than 1H:1V (horizontal to vertical) where room permits. Excavations in the undocumented fill should be sloped no steeper than 2H:1V where room permits. Flatter inclinations may be necessary where groundwater seepage is present. All temporary cuts should be in accordance with Washington Administrative Code (WAC) Part N, Excavation, Trenching, and Shoring. The temporary slope cuts should be visually inspected daily by a KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 13 of 16 Krazan & Associates, Inc. Offices Serving the Western United States qualified person during construction work activities and the results of the inspections should be included in daily reports. The contractor is responsible for maintaining the stability of the temporary cut slopes and minimizing slope erosion during construction. The temporary cut slopes should be covered with plastic sheeting to help minimize erosion during wet weather and the slopes should be closely monitored until the permanent retaining systems are complete. Materials should not be stored and equipment operated within 10 feet of the top of any temporary cut slope. A Krazan & Associates geologist or geotechnical engineer should observe, at least periodically, the temporary cut slopes during the excavation work. The reason for this is that all soil conditions may not be fully delineated by the limited sampling of the site from the geotechnical explorations. In the case of temporary slope cuts, the existing soil conditions may not be fully revealed until the excavation work exposes the soil. Typically, as excavation work progresses, the maximum inclination of the temporary slope will need to be evaluated by the geotechnical engineer so that supplemental recommendations can be made. Soil and groundwater conditions can be highly variable. Scheduling for soil work will need to be adjustable, to deal with unanticipated conditions, so that the project can proceed smoothly and required deadlines can be met. If any variations or undesirable conditions are encountered during construction, Krazan & Associates should be notified so that supplemental recommendations can be made. Drainage and Erosion Control The ground surface should slope away from building pads and pavement areas, toward appropriate drop inlets or other surface drainage devices. It is recommended that adjacent exterior grades be sloped a minimum of 2 percent for a minimum distance of 5 feet away from structures. Roof drains should be tightlined away from foundations. Roof drains should not be connected to the footing drains. Surface water runoff should not be allowed to flow over the western steep slope during or after construction. Specific recommendations for and design of storm water disposal systems or septic disposal systems are beyond the scope of our services and should be prepared by other consultants that are familiar with design and discharge requirements. Erosion and sediment control (ESC) is used to minimize the transportation of sediment to wetlands, streams, lakes, drainage systems, and adjacent properties. Erosion and sediment control measures should be implemented and these measures should be in general accordance with local regulations. As a minimum, the following basic recommendations should be incorporated into the design of the erosion and sediment control features of the site: 1) Phase the soil, foundation, utility and other work, requiring excavation or the disturbance of the site soils, to take place during the dry season (generally May through September). However, provided precautions are taken using Best Management Practices (BMP’s), grading activities can be undertaken during the wet season (generally October through April), but it should also be known that this may increase the overall cost of the project. 2) All site work should be completed and stabilized as quickly as possible. KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 14 of 16 Krazan & Associates, Inc. Offices Serving the Western United States 3) Additional perimeter erosion and sediment control features may be required to reduce the possibility of sediment entering the surface water. This may include additional silt fences, silt fences with a higher Apparent Opening Size (AOS), construction of a berm, or other filtration systems. 4) Any runoff generated by dewatering discharge should be treated through construction of a sediment trap if there is sufficient space. If space is limited, other filtration methods will need to be incorporated. Limitations Geotechnical engineering is one of the newest divisions of Civil Engineering. This branch of Civil Engineering is constantly improving as new technologies and understanding of earth sciences improves. Although your site was analyzed using the most appropriate current techniques and methods, undoubtedly there will be substantial future improvements in this branch of engineering. In addition to improvements in the field of geotechnical engineering, physical changes in the site either due to excavation or fill placement, new agency regulations or possible changes in the proposed structure after the time of completion of the soils report may require the soils report to be professionally reviewed. In light of this, the owner should be aware that there is a practical limit to the usefulness of this report without critical review. Although the time limit for this review is strictly arbitrary, it is suggested that two years be considered a reasonable time for the usefulness of this report. This report has been prepared for the exclusive use of the Abbey Road Group Land Development Services Company, LLC and their assigns. Foundation and earthwork construction is characterized by the presence of a calculated risk that soil and groundwater conditions have been fully revealed by the original foundation investigation. This risk is derived from the practical necessity of basing interpretations and design conclusions on limited sampling of the earth. Our report, design conclusions and interpretations should not be construed as a warranty of the subsurface conditions. Actual subsurface conditions may differ, sometimes significantly, from those indicated in this report. The recommendations made in this report are based on the assumption that soil conditions do not vary significantly from those disclosed during our field investigation. The findings and conclusions of this report can be affected by the passage of time, such as seasonal weather conditions, manmade influences, such as construction on or adjacent to the site, natural events such as earthquakes, slope instability, flooding, or groundwater fluctuations. If any variations or undesirable conditions are encountered during construction, the geotechnical engineer should be notified so that supplemental recommendations can be made. The conclusions of this report are based on the information provided regarding the proposed construction. If the proposed construction is relocated or redesigned, the conclusions in this report may not be valid. The geotechnical engineer should be notified of any changes so that the recommendations can be reviewed and reevaluated. Misinterpretations of this report by other design team members can result in project delays and cost overruns. These risks can be reduced by having Krazan & Associates, Inc. involved with the design team’s meetings and discussions before, during, and after submission of our report. Krazan & Associates, Inc. should also be KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 15 of 16 Krazan & Associates, Inc. Offices Serving the Western United States retained for reviewing pertinent elements of the design team’s plans and specifications. Contractors can also misinterpret this report. To reduce this risk, Krazan & Associates. Inc. should participate in pre-bid and pre- construction meetings, and provide construction observations and testing during the site work. This report is a geotechnical engineering investigation with the purpose of evaluating the soil conditions in terms of foundation design. The scope of our services did not include any environmental site assessment for the presence or absence of hazardous and/or toxic materials in the soil, groundwater or atmosphere, or the presence of wetlands. Any statements or absence of statements, in this report or on any soils log regarding odors, unusual or suspicious items, or conditions observed are strictly for descriptive purposes and are not intended to convey engineering judgment regarding potential hazardous and/or toxic assessments. The geotechnical information presented herein is based upon professional interpretation utilizing standard engineering practices and a degree of conservatism deemed proper for this project. It is not warranted that such information and interpretation cannot be superseded by future geotechnical developments. We emphasize that this report is valid for this project as outlined above, and should not be used for any other site. Our report is prepared for the exclusive use of our client. No other party may rely on the product of our services unless we agree in advance to such reliance in writing. Properties on Hillsides: During our site visit, we did not observe indications of current deep-seated land sliding or scarps from potential past slope failures within the exposed portion of the property. Signs of shallow soil movement, such as curved tree trunks, were also not observed at the site. Shallow soil movement is typically caused by the movement of loose/soft surficial soils in a wet condition. Relatively shallow failures, as well as surficial erosion, are natural processes and should be expected to occur within sloping ground. It should be noted that the western steep slope is heavily vegetated and much of the ground surface on the slope was not visible at the time of our site visit. Although indications of erosion and current significant land sliding were not observed on the exposed portion of the property during our site visit, it is our opinion that there is always some potential for soil movement on sloping ground. Property owners with structures on or near hillsides should realize that landslide movements are always a possibility. It may be prudent for the property owner to retain a qualified geotechnical professional to periodically inspect the slope, especially after a winter storm event or when any distress is evident. The probability that landsliding will occur is substantially reduced by the proper implementation and maintenance of drainage control measures at the site. Therefore, the property owner should take responsibility for performing such maintenance. KA Project No. 062-20013 Mei Lin View Short Plat July 9, 2020 Page No. 16 of 16 Krazan & Associates, Inc. Offices Serving the Western United States We appreciate the opportunity to provide service to you on this project. If you have any questions, or if we may be of further assistance, please do not hesitate to contact our office at (253) 939-2500. Respectfully submitted, KRAZAN & ASSOCIATES, INC. 07/9/20 Vijay Chaudhary, P.E. Theresa Nunan Assistant Regional Engineering Manager Project Manager Attachments: Figure 1 - Vicinity Map Figure 2 - Site Plan Soil Classification Chart Soil Boring Logs Laboratory Test Results Figure 3 - Slope Stability Cross Section A-A’ Figure 4 - Slope Stability Static Condition Figure 5 - Slope Stability Seismic Condition Project Number: 062-20013Date: June 2020 Drawn By: VC Figure: 1 Mei Lin Short Plat: 1833 NE 12th Street, Renton, WA Not to scale Number and Approximate Location of Hand Auger Exploration LEGEND Reference: USGS topographic map titled "Mercer Island Quadrangle, Washington - King County, 7.5-Minute Series", dated 2020. H-1SWCampusDrive132nd Ave NELot C Proposed Building Proposed Building Lot D B-1 B-2 B-1B-2 B-3 B-1 B-2 B-4 B-3 B-5 H-1 H-2 TP-1 TP-1 TP-1 TP-2 TP-6 TP-1 Vicinity Map AA'REFERENCE: GRADING PLAN PREPARED BY ABBEY RAOD GROUP, DATED FEBRUARY 5, 2020.B-2B-1PROPOSED DEVELOPMENT AREAB-1LEGENDNUMBER AND APPROXIMATELOCATION OF SOIL BORINGSSITE PLANFIGURE 2PROJECT NAME:MEI LIN SHORT PLATPROJECT NUMBER:062-20013SCALE: 0.375" = 1'(NOT FOR CONSTRUCTION)DATE: JUNE 2020 Project Number: 062-20013 & A S S O C I A T E S, I N C. Date: June 2020 Drawn By: TRN References: USCS Soil Classification Mei Lin Short Plat Relative Density with Respect to SPT N-Value Coarse-Grained Soils Density Very Loose Very Soft Soft Medium Stiff Stiff Very Stiff Hard 0 - 4 0 - 1 2 - 4 5 - 8 9 - 15 16 - 30 > 30 5 -10 11 - 30 31 - 50 > 50 Loose Medium Dense Dense Very Dense DensityN-Value (Blows/Ft)N-Value (Blows/Ft) Fine-Grained Soils USCS Soil Classification Major Division Coarse- Grained Soils < 50% passes #200 sieve Gravel and Gravelly Soils < 50% coarse fraction passes #4 sieve Gravel (with little or no fines) GW Well-Graded Gravel Poorly Graded Gravel Silty Gravel Clayey Gravel Well-Graded Sand Poorly Graded Sand Silty Sand Clayey Sand Silt Lean Clay Organic Silt and Clay (Low Plasticity) Inorganic Silt Inorganic Clay Organic Clay and Silt (Med. to High Plasticity) Peat GP GM GC SW SP SM SC ML CL OL MH CH OH PT Sand (with little or no fines) Gravel (with > 12% fines) Sand (with > 12% fines) Sand and Sandy Soils > 50% coarse fraction passes #4 sieve Silt and Clay Liquid Limit < 50 Silt and Clay Liquid Limit > 50 Highly Organic Soils Fine- Grained Soils > 50% passes #200 sieve Group Description Project Number: Started: Field Engineer:Completed: Backfilled: Ground Surface Elevation:Groundwater Depth: 3 2 7 5 6 11 6 4 2 2 1 2 2 5 20 23 42 55 20 1 of 2 Drilling Method: Hammer Type: 3.25" ID Hollow Stem Augers Automatic, 140#SPTS-6 97 MC = 4.3% MC = 13.1% MC = 11.2% 8" of Decayed Vegetation (leaves, grass, plants) Brown Silty SAND (SM) with Gravel, medium dense to loose, moist - - - becomes very loose Brownish Gray Silty SAND (SM), trace Gravel, fine to medium grained sand, trace coarse sand, medium dense, moist 9 17 6 3 25 (FILL)SPTS-4 SPTS-5SPTS-1 SPTS-2 SPTS-3 Project:Client:B-1Mei Lin Short Plat 062-20013 Abbey Road Group Boring No. Address, City, State:Drilling Company: 1833 NE 12th Street, Renton, WA Advanced Drill Technologies Project Manager:DateEquipment: Theresa Nunan 6.4.2020 Automatic Hammer Theresa Nunan 6.4.2020 6.4.2020 Total Depth of Boring: 239 +/- feet Not Encountered 31.0 feet Elev. (feet)Depth (feet)Sample TypeSample IDBlow Counts N-Value(blows/ft)Graphic LogClassification Lab Results 1 2 4 5 8 3 11 12 6 7 14 15 9 10 16 17 13 (WEATHERED TILL) Brownish Gray/Gray Silty SAND (SM), trace Gravel, fine to medium grained sand, trace coarse sand, very dense, moist Page 18 19 Project Number: Started: Field Engineer:Completed: Backfilled: Ground Surface Elevation:Groundwater Depth: 10 42 50/4" 30 50 29 50 40 2 of 2 MC = 12.1% MC = 5.0% MC = 7.8% Brownish Gray/Gray Silty SAND (SM), trace Gravel, fine to medium grained sand, trace coarse sand, very dense, moist (GLACIAL TILL) 50/6"SPTS-6 50/6" End of Boring at 31.0 Feet 39 PageSPTS-7 92/10" 35 36 37 38 32 33 34 29 30 31 SPTS-8 26 27 28 23 24 25 Graphic LogClassification Lab Results 21 22 Total Depth of Boring: 239 +/- feet Not Encountered 31.0 feet Elev. (feet)Depth (feet)Sample TypeSample IDBlow Counts N-Value(blows/ft)Drilling Method: Theresa Nunan 6.4.2020 3.25" ID Hollow Stem Augers Hammer Type: 6.4.2020 Automatic, 140# Address, City, State:Drilling Company: 1833 NE 12th Street, Renton, WA Advanced Drill Technologies Project Manager:DateEquipment: Theresa Nunan 6.4.2020 Automatic Hammer Project:Client:Boring No.B-1Mei Lin Short Plat 062-20013 Abbey Road Group Project Number: Started: Field Engineer:Completed: Backfilled: Ground Surface Elevation:Groundwater Depth: 8 11 8 4 3 2 2 3 3 2 4 3 2 2 2 2 4 10 8 11 12 20 SPT S-8 40 1 of 2 MC = 9.2% MC = 10.3% Brown Silty SAND (SM) with Gravel, medium dense, moist - - - becomes loose, trace Gravel (FILL) Mottled Brown and Gray Silty SAND (SM), trace Gravel, fine to medium grained sand, trace coarse sand, medium dense, moist - - - becomes very loose - - - becomes loose MC = 13.0%SPTS-5 4SPT %G = 4 %Sa = 59 %Si/Cl = 37 MC = 14.2% 19 16 Page (WEATHERED TILL) MC = 7.8% MC = 13.5%SPTS-6 14 23 S-4 7 SPTS-7 17 18 13 14 15 9 10 11 12 6 7 8 4 5 SPTS-3 6 192 3 SPTS-2 5 Graphic LogClassification Lab Results 9" of Decayed Vegetation (leaves, grass, plants) 1 SPTS-1 Total Depth of Boring: 238 +/- feet Not Encountered 31.0 feet Elev. (feet)Depth (feet)Sample TypeSample IDBlow Counts N-Value(blows/ft)Drilling Method: Theresa Nunan 6.4.2020 3.25" ID Hollow Stem Augers Hammer Type: 6.4.2020 Automatic, 140# Address, City, State:Drilling Company: 1833 NE 12th Street, Renton, WA Advanced Drill Technologies Project Manager:DateEquipment: Theresa Nunan 6.4.2020 Automatic Hammer Project:Client:Boring No.B-2Mei Lin Short Plat 062-20013 Abbey Road Group Project Number: Started: Field Engineer:Completed: Backfilled: Ground Surface Elevation:Groundwater Depth: SPT S-8 50 50/6" 24 50/4" 12 18 33 40 2 of 2Page MC = 8.2% MC = 12.7%SPTS-9 50/4" End of Boring at 31.0 Feet S-10 36 37 38 39 33 34 35 31 32 SPT5130 %G = 8 %Sa = 54 %Si/Cl = 38 MC = 18.8% Dark Gray Silty SAND/Sandy SILT ((SM/ML), trace Gravel, very dense/very hard, moist 29 (GLACIAL TILL) (GLACIAL TILL) 27 28 24 25 26 21 22 23 Graphic LogClassification Lab Results Grey Silty SAND (SM), with Gravel, fine to medium grained sand, trace coarse sand, very dense, moist Total Depth of Boring: 238 +/- feet Not Encountered 31.0 feet Elev. (feet)Depth (feet)Sample TypeSample IDBlow Counts N-Value(blows/ft)Drilling Method: Theresa Nunan 6.4.2020 3.25" ID Hollow Stem Augers Hammer Type: 6.4.2020 Automatic, 140# Address, City, State:Drilling Company: 1833 NE 12th Street, Renton, WA Advanced Drill Technologies Project Manager:DateEquipment: Theresa Nunan 6.4.2020 Automatic Hammer Project:Client:Boring No.B-2Mei Lin Short Plat 062-20013 Abbey Road Group Particle 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 % Fines 0 1 7 4 13 37 386 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 (C-136 & C-117) 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:Location: B-2 Sample Number: 20L276 Depth: 24.5' to 26' Client: Project: Project No:Figure Grey silty sand. Sampled by T.Nunan. 1 .75 .625 .5 .375 #4 #8 #10 #16 #20 #40 #60 #80 #100 #200 100 99 98 96 95 92 89 88 87 86 75 62 54 49 38 NP NV NP SM A-4(0) 2.9077 0.7262 0.2290 0.1536 Moisture Content(ASTM D2216):8.8% 6-4-12 6-9-20 M.Thomas T.Nunan Project Manager 6-4-12 Abbey Road Group Land Development Services Company, LLC. Mei Lin View Short Plat 066-20013 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) Particle 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 % Fines 0 0 4 2 11 46 376 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 (C-136 & C-117) 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:Location: B-2 Sample Number: 20L278 Depth: 15' to 16.5' Client: Project: Project No:Figure Brown & gray mottled silty sand. Sampled by T.Nunan. .75 .625 .5 .375 #4 #8 #10 #16 #20 #40 #60 #80 #100 #200 100 99 99 98 96 95 94 92 92 83 68 58 52 37 NP NV NP SM A-4(0) 0.6383 0.4752 0.1901 0.1398 Moisture Content(ASTM D2216):14.2% 6-4-20 6-9-20 M.Thomas M.Thomas Materials Laboratory Manager 6-4-20 Abbey Road Group Land Development Services Company, LLC. Mei Lin View Short Plat 066-20013 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) CROSS-SECTION AA'050100150200250190200210220230240(EAST-WEST)250180170160150300350400825 Center StreetTacoma, WA 98409Phone: (253) 939-2500Fax: (253) 939-2556SCALE0.25" = 1' Project Number: 062-20013Date: June 2020 Drawn By: VC Figure: 4 Slope Stability (Static Condition) Mei Lin Short Plat Not to scale Number and Approximate Location of Hand Auger Exploration LEGEND H-1SWCampusDrive132nd Ave NELot C Proposed Building Proposed Building Lot D B-1 B-2 B-1B-2 B-3 B-1 B-2 B-4 B-3 B-5 H-1 H-2 TP-1 TP-1 TP-1 TP-2 TP-6 TP-1 Project Number: 062-20013Date: June 2020 Drawn By: VC Figure: 5 Slope Stability (Seismic Condition) Mei Lin Short Plat Not to scale Number and Approximate Location of Hand Auger Exploration LEGEND H-1SWCampusDrive132nd Ave NELot C Proposed Building Proposed Building Lot D B-1 B-2 B-1B-2 B-3 B-1 B-2 B-4 B-3 B-5 H-1 H-2 TP-1 TP-1 TP-1 TP-2 TP-6 TP-1