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23-101052-SU Geotechnical Report 2-28-23 1 10/26/2022 Roman Koval 23118 126th Ave SE Kent, WA Subject: Geotechnical Services Report Koval Short Plat Geotechnical Consultation TPN: 7575600130; 27634 25th Dr. S, Federal Way, WA Project Number: QG22-173 Dear Mr. Koval, At your request, Quality Geo NW, PLLC (QG) has completed a soils investigation of the above referenced project. The investigation was performed in accordance with our proposal for professional services. We would be pleased to continue our role as your geotechnical consultant of record during the project planning and construction phases, as local inspection firms have not been found to be as familiar or reliably experienced with geotechnical design. This may include soil subgrade inspections, periodic review of special inspection reports, or supplemental recommendations if changes occur during construction. We will happily meet with you at your convenience to discuss these and other additional Time & Materials services. We thank you for the opportunity to be of service on this project and trust this report satisfies your project needs currently. QG wishes you the best while completing the project. Respectfully Submitted, Quality Geo NW, PLLC Alexander Barnes Staff Geologist Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 2 SOILS REPORT KOVAL SHORT PLAT TPN: 7575600130, 27634 25th DRIVE SOUTH FEDERAL WAY, WA Roman Koval 23118 126th Ave SE Kent, WA Prepared by: Approved by: Alexander Barnes Luke Preston McCann, L.E.G. Staff Geologist Principal Licensed Engineering Geologist Quality Geo NW, PLLC Geotechnical Investigation & Engineering Consultation Phone: 360-878-9750| Web: qualitygeonw.com Mail: 4631 Whitman Ln SE, Ste D, Lacey, WA 98513 10/26/2022 QG Project # QG22-173 Copyright © 2022 Quality Geo NW, PLLC All Rights Reserved 10/26/2022 Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 3 TABLE OF CONTENTS 1.0 INTRODUCTION ...............................................................................................................4 1.1 PROJECT DESCRIPTION ............................................................................................................................. 4 1.2 FIELD WORK ................................................................................................................................................ 4 2.0 EXISTING SITE CONDITIONS ........................................................................................5 2.1 AREA GEOLOGY .......................................................................................................................................... 5 2.2 SITE & SURFACE CONDITIONS ................................................................................................................ 5 2.3 SOIL LOG ....................................................................................................................................................... 6 2.4 SURFACE WATER AND GROUNDWATER CONDITIONS ..................................................................... 6 3.0 GEOTECHNICAL RECOMMENDATIONS .....................................................................7 3.1 SETBACK RECOMMENDATIONS ............................................................................................................. 7 3.2 SHALLOW FOUNDATION RECOMMENDATIONS ................................................................................. 7 3.2.1 BUILDING SLAB ON GRADE FLOOR ............................................................................................. 9 3.3 INFILTRATION RATE DETERMINATION .............................................................................................. 10 3.3.1 INFILTRATION FEASIBILITY ....................................................................................................... 10 3.3.2 DRAINAGE RECOMMENDATIONS ............................................................................................... 10 4.0 CONSTRUCTION RECOMMENDATIONS ...................................................................11 4.1 EARTHWORK ............................................................................................................................................. 11 4.1.1 GRADING & EXCAVATION ............................................................................................................ 11 4.1.2 SUBGRADE EVALUATION & PREPARATION ............................................................................ 11 4.1.3 SITE PREPARATION, EROSION CONTROLL, WET WEATHER............................................... 11 4.2 STRUCTURAL FILL MATERIALS AND COMPACTION ....................................................................... 12 4.2.1 MATERIALS ...................................................................................................................................... 12 4.2.2 FILL PLACEMENT AND COMPACTION ...................................................................................... 13 4.3 TEMPORARY EXCAVATIONS AND TRENCHES .................................................................................. 13 5.0 SPECIAL INSPECTION ...................................................................................................15 6.0 LIMITATIONS ..................................................................................................................16 Region & Vicinity Maps ................................................................................................................ 17 Exploration Map ............................................................................................................................. 18 Slope Profile A-A’.......................................................................................................................... 19 Exploration Logs ............................................................................................................................ 20 Laboratory Results .......................................................................................................................... 22 Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 4 1.0 INTRODUCTION This report presents the findings and recommendations of Quality Geo NW’s (QG) soil investigation conducted in support of new site surface improvements. 1.1 PROJECT DESCRIPTION QG understands the project entails new construction within a presently developed parcel. QG has been contracted to evaluate soil, foundation, infiltration conditions, and necessary slope setbacks. 1.2 FIELD WORK Site exploration activities were performed on 9/19/2022. Exploration locations were marked in the field by a QG Staff Geologist with respect to the provided map and cleared for private and public conductible utilities. Our exploration locations were selected by an QG Staff Geologist prior to field work to provide safest access to relevant soil conditions. The geologist directed the advancement of 1 excavated test pit (TP). The test pit was advanced within the vicinity of the anticipated development footprint area, to a maximum depth of 10.0 feet below present grade (BPG) in general accordance with the specified contract depth. During explorations QG logged each soil horizon encountered, and field classified them in accordance with the Unified Soil Classification System (USCS). Representative soil samples were collected from each unit, identified according to boring location and depth, placed in plastic bags to protect against moisture loss, and were transported to the soil laboratory for supplemental classification and other tests. QG advanced 1 Wildcat Dynamic Cone Penetrometer (DCP) tests at a representative location within the vicinity of a proposed structure location and as slope conditions permitted. The penetrometer test was terminated upon reaching the equipment’s maximum practical extent. During penetrometer advancement, blow counts were recorded in 10-centimeter increments as a thirty-five-pound weight was dropped a distance of 15 inches. Blow counts were then converted to resistance (kg/cm2), standard penetration blow counts (N-values), and corresponding soil consistency, with complete results shown on the attached logs. An aerial site plan with relevant features is presented in Appendix B. Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 5 2.0 EXISTING SITE CONDITIONS 2.1 AREA GEOLOGY QG reviewed available map publications to assess known geologic conditions and hazards present at the site location. The Washington Geologic Information Portal (WGIP), maintained by the Department of Natural Resources Division of Geology and Earth Resources, provides 1:24,000- scale geologic mapping of the region. Geology of the site location and vicinity consists of Vashon till (Qvt). The deposits on site are described as “Compact diamict containing subrounded to well- rounded clasts in massive, silt- or sand-rich matrix. Glacially transported and deposited. Generally, a few meters to a few tens of meters thick, forming undulatory surface. Also found sporadically within areas mapped as unit Qvi.” The WGIP Map also offers layers of mapped geohazard conditions within the state. According to the regional-scale interactive map, there are no mapped landslide deposits to exist within the extent or vicinity of the parcel. Available LiDAR imagery of the site did not reveal any obvious or prominent geologic hazards within the site or immediate vicinity. The United States Department of Agriculture portal (USDA) provides a soil mapping of the region. The soils in the southern vicinity are mapped as Alderwood gravelly sandy loam (AgD) formed as ridges and hills. The parent material for the soils on site is glacial drift and/or glacial outwash over dense glaciomarine deposits. The soils are described as gravelly sandy loam from 0 to 7 inches, and very gravelly sandy loam from 7 to 59 inches. Depth to restrictive feature is 20 to 39 inches to densic material. Capacity of most limiting layer to transmit water (ksat), is listed as very low to moderately low (0.00 to 0.06 in/hr). Depth to water table is 18 to 37 inches. 2.2 SITE & SURFACE CONDITIONS The parcel is divided in half north to south and contains an existing residential home north of the build site. When QG arrived on site, the project area had been graded with a generally level platform cut into the gentle north-south trending slope, with loose cuttings and fill covering an over-steepened slope facing west and grading downward to the boundary of the parcel. The build site it undeveloped and has no vegetation, with the exception of remaining young and mature maple trees on the western slope. Native soils and intact vegetation north of the fill material consist of bushes and dense brambles, making the slope inaccessible. No surface water features were observed on site. The natural slope west of the house displayed tension cracks at the crest of the slope, within 5-10 feet of the foundation. Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 6 2.3 SOIL LOG Representative lab samples were taken from TP-1 from an estimated 3 feet below native grade within the graded project area. Soil conditions on site were as follows: • 0’ to 10.0’ – Silty Sand with Gravel (SM): A dominant soil unit characterized as brown, moist, and presenting few organics. Cobbles were present and observed up to 5-inches in diameter. Layer was dense to very dense condition, common with till soils and glacial drift. 2.4 SURFACE WATER AND GROUNDWATER CONDITIONS No active surface water features are present on site. In the near vicinity, Star Lake is ~2400 feet east of the parcel. During our test pit explorations, no groundwater table was encountered. Available groundwater data does not exist based on well logs made publicly available by the WA Department of Ecology. QG’s scope of work did not include determination or monitoring of seasonal groundwater elevation variations, formal documentation of wet season site conditions, or conclusive measurement of groundwater elevations at depths past the extent feasible for explorations at the time of the field explorations. Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 7 3.0 GEOTECHNICAL RECOMMENDATIONS 3.1 SETBACK RECOMMENDATIONS Considering the inclination and conditions of the adjacent slope, specific setback requirements must be followed for successful construction at this location. The local critical area ordinance delineates minimum slope toe setbacks for slopes inclined greater than 40% (~22°), which may be further reduced upon review by a licensed geotechnical professional. QG’s reviewed existing topographic data and general site observations made during our visit to infer general slope face and slope toe setbacks based on height and inclination of the typical slopes present on the site in proximity to the proposed structure. Horizontal setbacks were determined based on standard International Building Code (IBC) requirements as accepted by the State of Washington. The IBC details required setback delineations for slopes with an overall inclination less than or equal to 45 degrees. Structures in the vicinity of descending slopes shall maintain a minimum horizontal slope crest setback, the lesser of H/3 or 40 feet. Structures shall also maintain a minimum slope toe setback, H/2 or 15 feet from ascending slopes. These setbacks can commonly be achieved through a combination of increasing footing embedment depths, in combination with expanding the building fill pad, and/or partially adjusting the footprint location. QG made limited inclination measurements in the field and reviewed existing topographic and LIDAR data, in comparison to our general site observations made during our visit, to evaluate the adjusted setback requirements. QG recommends a minimum 9-foot horizontal crest setback for any new foundation (see Appendix C). This does not apply to lightweight surface improvements such as uncovered decks, patios, walkways, landscaping, pathways, septic drainfields, etc. QG does not recommend reducing the setback unless further site-specific foundation design efforts are undertaken to ensure building and slope stability is maintained. 3.2 SHALLOW FOUNDATION RECOMMENDATIONS QG recommends excavating loose or organic cover soils down to firm bearing conditions expected within 2.0 feet from the surface. As the variability in subgrade support between consolidated glacial deposits and weathered medium dense cover soils may result in differential settlement, QG recommends that foundations be placed on compacted native soils wherever, or on firm structural fill installed over these compacted soils to achieve footing grade. Assuming site preparation is completed as described above, we recommend the following: Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 8 • Subgrade Preparation QG recommends excavating and clearing any loose or organic cover soils, including overriding topsoil where necessary, from areas of proposed construction, down to firm bearing conditions and benching the final bottom of subgrade elevation flat. Excavations should be performed with a smooth blade bucket to limit disturbance of subgrade soils. Vibratory compaction methods are suitable for densification of the non-organic native soils. After excavations have been completed to the planned subgrade elevations, but before placing fill or structural elements, the exposed subgrade should be evaluated under the periodic guidance of a QG representative. Any areas that are identified as being soft or yielding during subgrade evaluation should be brought to the attention of the geotechnical engineer. Where over excavation is performed below a structure, the over excavation area should extend beyond the outside of the footing a distance equal to the depth of the over excavation below the footing. The over excavated areas should be backfilled with properly compacted structural fill. The proposed buildings may utilize either stepped or continuous footings with slab-on-grade elements. For continuous footing elements, upon reaching bearing strata, we recommend benching foundation lines flat. Continuous perimeter and strip foundations may be stepped as needed to accommodate variations in final subgrade level. We also recommend maximum steps of 18 inches with spacing of at least 5 feet be constructed unless specified otherwise by the design engineer. Structural fill may then be placed as needed to reestablish final foundation grade. • Allowable Bearing Capacity: Up to 1,500 pounds per square foot (psf) for foundations placed on compacted native soil or on approved structural fill soils placed in accordance with the recommendations of Section 4.2. Bearing capacities, at or below 1,500 psf may eliminate the need for additional inspection requirements if approved by the county. The allowable bearing capacity may be increased by 1/3 for transient loading due to wind and seismic events. • Minimum Footing Depth: For a shallow perimeter and spread footing system, all exterior footings shall be embedded a minimum of 18 inches and all interior footings shall be embedded a minimum of 12 inches below the lowest adjacent finished grade, but not less than the depth required by design. However, all footings must also penetrate to the prescribed bearing stratum cited above. Minimum depths are referenced per IBC requirements for frost protection; other design concerns may dictate greater values be applied. Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 9 • Minimum Footing Width: Footings should be proportioned to meet the stated bearing capacity and/or the IBC 2012 (or current) minimum requirements. For a shallow perimeter and spread footing system, continuous strip footings should be a minimum of 16 inches wide and interior or isolated column footings should be a minimum of 24 inches wide. • Estimated Settlements: All concrete settles after placement. We estimate that the maximum settlements will be on the order of 0.5 inch, or less, with a differential settlement of ½ inch, or less, over 50 linear feet. Settlement is anticipated to occur soon after the load is applied during construction. 3.2.1 BUILDING SLAB ON GRADE FLOOR QG anticipates that slab-on-grade floors are planned for the interior of the proposed building. Based on typical construction practices, we assume finished slab grade will be similar to or marginally above present grade for the below recommendations. If floor grades are planned to be substantially raised or lowered from existing grade, QG should be contacted to provide revised or alternative recommendations. • Capillary Break: A capillary break will be helpful to maintain a dry slab floor and reduce the potential for floor damage resulting from shallow perched water inundation. To provide a capillary moisture break, a 6-inch thick, properly compacted granular mat consisting of open-graded, free- draining angular aggregate is recommended below floor slabs. To provide additional slab structural support, or to substitute for a structural fill base pad where specified, QG recommends the capillary break should consist of crushed rock all passing the 1-inch sieve and no more than 3 percent (by weight) passing the U.S. No. #4 sieve, compacted in accordance with Section 5.2.2 of this report. • Vapor Barrier: A vapor retarding membrane such as 10 mil polyethylene film should be placed beneath all floor slabs to prevent transmission of moisture where floor coverings may be affected. Care should be taken during construction not to puncture or damage the membrane. To protect the membrane, a layer of sand no more than 2 inches thick may be placed over the membrane if desired. If excessive relict organic fill material is discovered at any location, additional sealant or more industrial gas barriers may be required to prevent off-gassing of decaying material from infiltrating the new structure. These measures shall be determined by the structural engineer to meet local code requirements as necessary. Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 10 • Structural Design Considerations: QG assumes design and specifications of slabs will be assessed by the project design engineer. We suggest a minimum unreinforced concrete structural section of 4.0 inches be considered to help protect against cracking and localized settlement, especially where larger equipment or localized loads are anticipated. It is generally recommended that any floor slabs and annular exterior concrete paving subject to vehicular loading be designed to incorporate reinforcing. Additionally, some level of reinforcing, such as a wire mesh may be desirable to prolong slab life due to the overwhelming presence of such poor underlying soils. It should be noted that QG does not express any guarantee or warranty for proposed slab sections. 3.3 INFILTRATION RATE DETERMINATION QG understands design of on-site stormwater controls are pending the results of this study to confirm design parameters and interpreted depths to perched seasonal groundwater and restrictive soil features. 3.3.1 INFILTRATION FEASIBILITY Qg does not recommend dispersion or infiltration of collected stormwater on slopes, as increased runoff or localized stormwater inundation can negatively impact long-term erosional and global slope stability. Stormwater management measures will be the responsibility of the clients retained site designer. 3.3.2 DRAINAGE RECOMMENDATIONS QG recommends proper drainage controls for stormwater runoff during and after site development to protect the site. The ground surface adjacent to structures should be sloped to drain away at a 5% minimum to prevent ponding of water adjacent to them. QG recommends all stormwater catchments (new or existing) be tightlined (piped) away from structures to an existing catch basin, stormwater system, established channel, or approved outfall to be released using appropriate energy-dissipating features at the outfall to minimize point erosion. Roof and footing drains should be tightlined separately or should be gathered in an appropriately sized catch basin structure and redistributed collectively. If storm drains are incorporated for impervious flatworks (driveways, sidewalks, etc.) collected waters should also be discharged according to the above recommendations. Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 11 4.0 CONSTRUCTION RECOMMENDATIONS 4.1 EARTHWORK 4.1.1 GRADING & EXCAVATION A grading plan was not available to QG at the time of this report. However, based on provided conceptual plans, this study assumes finished site grade will approximate current grade. Therefore, depths referred to in this report are considered roughly equivalent to final depths. Excavations can generally be performed with conventional earthmoving equipment such as bulldozers, scrapers, and excavators. 4.1.2 SUBGRADE EVALUATION & PREPARATION After excavations have been completed to the planned subgrade elevations, but before placing fill or structural elements, the exposed subgrade should be evaluated under the part-time observation and guidance of an QG representative. The special inspection firm should continuously evaluate all backfilling. Any areas that are identified as being soft or yielding during subgrade evaluation should be over excavated to a firm and unyielding condition or to the depth determined by the geotechnical engineer. Where over excavation is performed below a structure, the over excavation area should extend beyond the outside of the footing a distance equal to the depth of the over excavation below the footing. The over excavated areas should be backfilled with properly compacted structural fill. 4.1.3 SITE PREPARATION, EROSION CONTROLL, WET WEATHER Any silty or organic rich native soils may be moisture-sensitive and become soft and difficult to traverse with construction equipment when wet. During wet weather, the contractor should take measures to protect any exposed soil subgrades, limit construction traffic during earthwork activities, and limit machine use only to areas undergoing active preparation. Once the geotechnical engineer has approved subgrade, further measures should be implemented to prevent degradation or disturbance of the subgrade. These measures could include, but are not limited to, placing a layer of crushed rock or lean concrete on the exposed subgrade, or covering the exposed subgrade with a plastic tarp and keeping construction traffic off the subgrade. Once subgrade has been approved, any disturbance because the subgrade was not protected should be repaired by the contractor at no cost to the owner. During wet weather, earthen berms or other methods should be used to prevent runoff from draining into excavations. All runoffs should be collected and disposed of properly. Measures may Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 12 also be required to reduce the moisture content of on-site soils in the event of wet weather. These measures can include, but are not limited to, air drying and soil amendment, etc. QG recommends earthwork activities take place during the summer dry season. 4.2 STRUCTURAL FILL MATERIALS AND COMPACTION 4.2.1 MATERIALS All material placed below structures or pavement areas should be considered structural fill. Excavated native soils may be considered suitable for reuse as structural fill on a case-by-case basis. Imported material can also be used as structural fill. Care should be taken by the earthwork contractor during grading to avoid contaminating stockpiled soils that are planned for reuse as structural fill with native organic materials. Frozen soil is not suitable for use as structural fill. Fill material may not be placed on frozen soil. Structural fill material shall be free of deleterious materials, have a maximum particle size of 4 inches, and be compactable to the required compaction level. Imported structural fill material should conform to the WSDOT manual Section 9-03.14(1) Gravel Borrow, or an approved alternative import material. Controlled-density fill (CDF) or lean mix concrete can be used as an alternative to structural fill materials, except in areas where free-draining materials are required or specified. Imported materials utilized for trench back fill shall conform to Section 9-03.19, Trench Backfill, of the most recent edition (at the time of construction) of the State of Washington Department of Transportation Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT Standard Specifications). Imported materials utilize as grade fill beneath roads shall conform to WSDOT Section 9-03.10, Gravel Base. Pipe bedding material should conform to the manufacturer’s recommendations and be worked around the pipe to provide uniform support. Cobbles exposed in the bottom of utility excavations should be covered with pipe bedding or removed to avoid inducing concentrated stresses on the pipe. Soils with fines content near or greater than 10% fines content may likely be moisture sensitive and become difficult to use during wet weather. Care should be taken by the earthwork contractor during grading to avoid contaminating stockpiled soils that are planned for reuse as structural fill with native organic materials. The contractor should submit samples of each of the required earthwork materials to the materials testing lab for evaluation and approval prior to delivery to the site. The samples should be Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 13 submitted at least 5 days prior to their delivery and sufficiently in advance of the work to allow the contractor to identify alternative sources if the material proves unsatisfactory. 4.2.2 FILL PLACEMENT AND COMPACTION For lateral and bearing support, structural fill placement below footings shall extend at minimum a distance past each edge of the base of the footing equal to the depth of structural fill placed below the footing [i.e. extending at least a 1H:1V past both the interior and the exterior of the concrete footing]. Prior to placement and compaction, structural fill should be moisture conditioned to within 3 percent of its optimum moisture content. Loose lifts of structural fill shall not exceed 12 inches in thickness. All structural fill shall be compacted to a firm and unyielding condition and to a minimum percent compaction based on its modified Proctor maximum dry density as determined per ASTM D1557. Structural fill placed beneath each of the following shall be compacted to the indicated percent compaction: • Foundation and Floor Slab Subgrades: 95 Percent • Pavement Subgrades & wall backfill (upper 2 feet): 95 Percent • Pavement Subgrades & wall backfill (below 2 feet): 90 Percent • Utility Trenches (upper 4 feet): 95 Percent • Utility Trenches (below 4 feet): 90 Percent A sufficient number of tests should be performed to verify compaction of each lift. The number of tests required will vary depending on the fill material, its moisture condition and the equipment being used. Initially, more frequent tests will be required while the contractor establishes the means and methods required to achieve proper compaction. Jetting or flooding is not a substitute for mechanical compaction and should not be allowed. 4.3 TEMPORARY EXCAVATIONS AND TRENCHES All excavations and trenches must comply with applicable local, state, and federal safety regulations. Construction site safety is the sole responsibility of the Contractor, who shall also be solely responsible for the means, methods, and sequencing of construction operations. We are providing soil type information solely as a service to our client for planning purposes. Under no circumstances should the information be interpreted to mean that QG is assuming responsibility for construction site safety or the Contractor’s activities; such responsibility is not being implied and should not be inferred. The contractor shall be responsible for the safety of personnel working in utility trenches. Given that steep excavations in native soils may be prone to caving, we recommend all utility trenches, but particularly those greater than 4 feet in depth, be supported in Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 14 accordance with state and federal safety regulations. Heavy construction equipment, building materials, excavated soil, and vehicular traffic should not be allowed near the top of any excavation. Temporary excavations and trenches should be protected from the elements by covering with plastic sheeting or some other similar impermeable material. Sheeting sections should overlap by at least 12 inches and be tightly secured with sandbags, tires, staking, or other means to prevent wind from exposing the soils under the sheeting. Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 15 5.0 SPECIAL INSPECTION The recommendations made in this report assume that an adequate program of tests and observations will be made throughout construction to verify compliance with these recommendations. Testing and observations performed during construction should include, but not necessarily be limited to, the following: • Geotechnical plan review and engineering consultation as needed prior to construction phase, • Observations and testing during site preparation, earthwork, structural fill, and pavement section placement, • Consultation on temporary excavation cutslopes and shoring if needed, • Consultation as necessary during construction. QG recommends that a local and reputable materials testing & inspection firm be retained for construction phase testing and observation in accordance with the local code requirements. We also strongly recommend that QG be retained as the project Geotechnical Engineering Firm of Record (GER) during the construction of this project to perform periodic supplementary geotechnical observations and review the special inspectors reports during construction. Our knowledge of the project site and the design recommendations contained herein will be of great benefit in the event that difficulties arise and either modifications or additional geotechnical engineering recommendations are required or desired. We can also, in a timely fashion observe the actual soil conditions encountered during construction, evaluate the applicability of the recommendations presented in this report to the soil conditions encountered, and recommend appropriate changes in design or construction procedures if conditions differ from those described herein. We would be pleased to meet with you at your convenience to discuss the Time & Materials scope and cost for these services. Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 16 6.0 LIMITATIONS Upon acceptance and use of this report, and its interpretations and recommendations, the user shall agree to indemnify and hold harmless QG, including its owners, employees and subcontractors, from any adverse effects resulting from development and occupation of the subject site. Ultimately, it is the owner’s choice to develop and live in such an area of possible geohazards (which exist in perpetuity across the earth in one form or another), and therefore the future consequences, both anticipated and unknown, are solely the responsibility of the owner. By using this report for development of the subject property, the owner must accept and understand that it is not possible to fully anticipate all inherent risks of development. The recommendations provided above are intended to reduce (but may not eliminate) such risks. This report does not represent a construction specification or engineered plan and shall not be used or referenced as such. The information included in this report should be considered supplemental to the requirements contained in the project plans & specifications and should be read in conjunction with the above referenced information. The selected recommendations presented in this report are intended to inform only the specific corresponding subjects. All other requirements of the above-mentioned items remain valid, unless otherwise specified. Recommendations contained in this report are based on our understanding of the proposed development and construction activities, field observations and explorations, and laboratory test results. It is possible that soil and groundwater conditions could vary and differ between or beyond the points explored. If soil or groundwater conditions are encountered during construction that differ from those described herein, or if the scope of the proposed construction changes from that described in this report, QG should be notified immediately in order to review and provide supplemental recommendations. The findings of this study are limited by the level of scope applied. We have prepared this report in substantial accordance with the generally accepted geotechnical engineering practice as it exists in the subject region. No warranty, expressed or implied, is made. The recommendations provided in this report assume that an adequate program of tests and observations will be conducted by a WABO approved special inspection firm during the construction phase in order to evaluate compliance with our recommendations. This report may be used only by the Client and their design consultants and only for the purposes stated within a reasonable time from its issuance, but in no event later than 18 months from the date of the report. It is the Client's responsibility to ensure that the Designer, Contractor, Subcontractors, etc. are made aware of this report in its entirety. Note that if another firm assumes Geotechnical Engineer of Record responsibilities, they need to review this report and either concur with the findings, conclusions, and recommendations or provide alternate findings, conclusions and recommendation. Land or facility use, on- and off-site conditions, regulations, or other factors may change over time, and additional work may be required. Based on the intended use of the report, QG may recommend that additional work be performed and that an updated report be issued. Non-compliance with any of these requirements by the Client or anyone else will release QG from any liability resulting from the use of this report. The Client, the design consultants, and any unauthorized party, agree to defend, indemnify, and hold harmless QG from any claim or liability associated with such unauthorized use or non-compliance. We recommend that QG be given the opportunity to review the final project plans and specifications to evaluate if our recommendations have been properly interpreted. We assume no responsibility for misinterpretation of our recommendations. Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 17 Region & Vicinity Maps REGION VICINITY Quality Geo NW, PLLC Site Region Koval Short Plat Geo Figure 1 Source: Google Imagery, 2022 Scale & Locations are approx. Not for Construction Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 18 Exploration Map Figure 2 Source: King Co. GIS, 2022 Scale & Locations are approx. Not for Construction 30 0 SCALE (FEET) Quality Geo NW, PLLC Site Map Koval Short Plat Geo A A’ Toe TP-1 DCP-1 Build site Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 19 Slope Profile A-A’ Quality Geo NW, PLLC Slope Profile A-A’ Koval Short Plat Geo Figure 3 Source: WA LIDAR 2021 & Hand Measurements Scale & Locations are approx. Not for Construction 15° 45° H ≈ 26ft Minimum 9 ft horizontal crest setback Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 20 Exploration Logs Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 21 Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 22 Laboratory Results Koval Short Plat Geo - Soils Report Quality Geo NW, PLLC 10/26/2022 Project # QG22-173 23