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APPROVED ENG PLN BLD2024-0149+ALL INFO ONE DOCUMENT.+2.3.2024_11.26.13_AM+4038371RECEIVED Feb 06 2024 CITY OF EDMONDS w \ DEVELOPMENTSERVICES4 p (v e t A Geosyntec Company February 1, 2024 Lilin Wu and Yutian Yao 18430 Olympic View Drive Edmonds, Washington 98020 --------------- Reviewed by 1 City of Edmonds ; 1 1 Planning DivisionIL 1 ------------ City Of Edmonds ALL WORK SUBJECT TO FIELD Building p De artment INSPECTION FOR WorkRetaining - -------------........._.......... CODE COMPLIANCE Block wall In ELSHAA Address 18430 Olympic View Drive APPROVED Owner;WU, Lilin PLANS MUST BE -------- ------- ... ----------- - --- ----------------- .... ..... --- .......-- ON JOB SITE Approved Date 4 �2 4/- 2 0 2 4 Building Official L/4CrKpy1L/Z O rLLL Permit Number BLD2 0 2 4 - 014 9 APPROVED BY PLANNING CAIII- Mar 07 2024 Re: Response to Building Permit Submittal Completeness Check, Permit BLD2023-1121 Parcel # 00565600200203 18430 Olympic View Drive -------------------- SPECIAL INSPECTION(S) REQUIRED FOR THIS ' Edmonds, WA 98020 PERMIT. Project No. AS230020A ' 1 1. Soils as per the Geo-tech. Engineer report 2. Structural observation and installation of block wall i and its components from the Geo technical Engineer. Dear Lilin and Yutian, This letter is provided in response to a Building Permit Submittal Completeness Check issued by the City of Edmonds (City) dated September 8, 2023. Seven items were marked as "Incomplete" in the Completeness Check document. The title of each item is listed below in bold italics (A through G) and addressed in plain text following. A. Site Development Plan. See Figure 1. B. Temporary Erosion and Sedimentation Control and Tree Retention Plan. 1. Temporary Erosion and Sedimentation Control (TESC) (ref ECDC 18.30.060) General notes: The project is in an area mapped as having erosion hazard and landslide hazard due to steep slope and geologic materials. For details, refer to Aspect Consulting's (Aspect), "Geotechnical Assessment in Support of Landscaping Wall Repair," June 8, 2023, included as Appendix A. The work area is on a moderate slope (<15%) adjacent to, but not on, the steep slope. The following TESC guidelines for the project will greatly reduce the erosion hazard. • All work will be done by hand. No motorized equipment will be used. • The area of ground disturbance will be less than 50 square feet immediately surrounding the area of landscaping wall repair. • The work will be performed during dry weather to reduce erosion hazard. • Washed rock will be placed behind the repaired wall section to facilitate drainage. Refer to the construction notes and drawing in Aspect's report "Response to City of Edmonds Building Permit Submittal Completeness Check," November, 15, 2023, included as Appendix B. • New impervious surfaces will be less than 5 square feet. Existing drainage at the project site will be adequate for the impervious area. • After construction is complete, any bare soil will be covered with erosion control materials such as mulch. • Permanent erosion control (plantings) will be installed as soon as practical after construction. RECEIVED Lilin Wu and Yutian )ftb 06 2024 February 1, 2024 CITY OF EDMONDS Project No. AS230020A DEVELOPMENT SERVICES DEPARTMENT 2. Tree retention and protection (ref EDC 23.10.060 and 23.10.070). General notes: All work will be done by hand and the complete work area is about 50 square feet. There are three trees near the work area: one mature conifer tree is about 5 feet west of the work area and two mature deciduous trees are about 20 feet from the work area — one to the east and one to the north. The trees will not be negatively impacted by the work because of the following factors. • No trees will be removed as part of this work. All trees will be retained. • While it is impractical to erect temporary fencing in such a small area, each tree will be flagged to remind workers to take care to protect the trees during construction. • A trench about 1 foot wide and less than 1 foot deep will be dug in the work area with hand tools. The trench will not impact any tree's critical root zone. • Gravel will be placed in the bottom of the trench and compacted with hand tools. Because of the small amount of gravel (less than '/4 cubic yard), the small footprint of the trench, and the light compaction force, the compaction will not negatively impact any tree's critical root zone. • The new impervious surface (the top of the repaired wall) that will be placed near the trees will be less than 5 square feet in area. • All work will be done with hand tools. • The grade will not be changed near any tree. C. Utility Plans — Water Sewer, Storm, Dry Utilities. See Figure 1. D. Plans scaled and legible. See Figure 1. E. Storm system rim, inverts, and material. See Figure 1. No ground disturbance will occur within about 60 feet of any mapped storm system elements and no excavation will be deeper than 12 inches. Rim and invert elevations are not shown. F. Sewer system cleanouts rim, inverts, and material. See Figure 1. No ground disturbance will occur within about 80 feet of any mapped sewer system elements and no excavation will be deeper than 12 inches. Rim and invert elevations are not shown. G. Water system meter and pipe size and material. See Figure 1. No ground disturbance will occur within about 20 feet of any mapped water system elements and no excavation will be deeper than 12 inches. Additional comments. 1. Clearly show all on -site improvements. See Figure 1. 2. Show existing side sewer and water service lines. See Figure 1. 3. Show onsite stormwater on plans. See Figure 1. 4. Show nearby City easements. See Figure 1. 5. Show to where the wall will drain. The drain rock behind the existing walls facilitates drainage and infiltration into the underlying gravelly fill and glacial outwash. The repaired section of the wall will have that same design. There is no drainpipe in the existing walls, and there will be no new pipe in the repaired wall section, that ties into a pipe that discharges to Puget Sound. Page 2 RECEIVED Lilin Wu and Yutian )ftb 06 2024 February 1, 2024 CITY OF EDMONDS Project No. AS230020A DEVELOPMENT SERVICES DEPARTMENT 6. Show proposed staging and equipment locations. All work for this project will be done with hand tools and no large equipment (drill rigs, excavators, etc.) will be used. Existing driveways and carports are adequate for this small project. Please do not hesitate to contact me with questions or comments. Limitations Work for this project was performed for Lilin Wu and Yutian Yao (Client), and this report was prepared consistent with recognized standards of professionals in the same locality and involving similar conditions, at the time the work was performed. No other warranty, expressed or implied, is made by Aspect Consulting (Aspect). Recommendations presented herein are based on our interpretation of site conditions, geotechnical engineering calculations, and judgment in accordance with our mutually agreed -upon scope of work. Our recommendations are unique and specific to the project, site, and Client. Application of this report for any purpose other than the project should be done only after consultation with Aspect. Variations may exist between the soil and groundwater conditions reported and those actually underlying the site. The nature and extent of such soil variations may change over time and may not be evident before construction begins. If any soil conditions are encountered at the site that are different from those described in this report, Aspect should be notified immediately to review the applicability of our recommendations. Risks are inherent with any site involving slopes and no recommendations, geologic analysis, or engineering design can assure slope stability. Our observations, findings, and opinions are a means to identify and reduce the inherent risks to the Client. It is the Client's responsibility to see that all parties to this project, including the designer, contractor, subcontractors, and agents, are made aware of this report in its entirety. If project developments result in changes from the preliminary project information, Aspect should be contacted to determine if our recommendations contained in this report should be revised and/or expanded upon. The scope of work does not include services related to construction safety precautions. Site safety is typically the responsibility of the contractor, and our recommendations are not intended to direct the contractor's site safety methods, techniques, sequences, or procedures. The scope of our work also does not include the assessment of environmental characteristics, particularly those involving potentially hazardous substances in soil or groundwater. All reports prepared by Aspect for the Client apply only to the services described in the Agreement(s) with the Client. Any use or reuse by any party other than the Client is at the sole risk of that party, and without liability to Aspect. Aspect's original files/reports shall govern in the event of any dispute regarding the content of electronic documents furnished to others. Please refer to Appendix D titled "Report Limitations and Guidelines for Use" for additional information governing the use of this report. Page 3 RECEIVED Lilin Wu and Yutian )ftb 06 2024 February 1, 2024 CITY OF EDMONDS Project No. AS230020A DEVELOPMENT SERVICES DEPARTMENT We appreciate the opportunity to perform these services. Sincerely, Aspect consulting Engineering Geoiogis, O 2931 �'C �Sed Geo�o 2/1/24 Matthew A. von der Ahe Matthew von der Ahe, L.E.G Project Geologist Matthew.vonderAhe@aspectconsulting.com Attachments: Figure 1 — Caption Appendix A — Geotechnical Assessment in Support of Landscaping Wall Repair (Aspect) Appendix B — Response to City of Edmonds Building Permit Submittal Completeness Check (Aspect) Appendix C — Building Permit Submittal Completeness Check (City of Edmonds) Appendix D — Report Limitations and Guidelines for Use V:\230020 Wu Property Geotech Srvcs\Deliverables\2024.2.1_Response to Competeness Check\Completeness check response_final.docx Page 4 RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT FIGURES RECEIVED Feb 06 2024 CITY OFEDMONDS OWNER/CONTRACTOR RESPONSIBLE FOR LOCATING Applicant shall re air/replace all DEVELOPMENT SERVICES ALL ON SITE UTILITIES. RELOCATION/REVISION TO ANY dama e to utilit s orfronta e 9 9 DEPARTMENT UTILITIES MAY REQUIRE A SEPERATE PERMIT. improvement�in ity right-of-way per city standard that is caused or o Ju wS occurs during th permitted project. T 11 50, 0 2S, o 0 Carport 100 00 ti Water Easements Meter I I ' o I o I Zib jss Q 0 TQs 8, R 15^ GbNCR�f JQ S 2 ENGINEERING DIVISION o APPROVED AS NOTED Driveway - Site Access 150 JdJ Wga",mt 03/12/2024 OWNER/CONTRACTOR IS RESPONSIBLE FOR VV EROSION CONTROL AND DRAINAGE House Sewer Site Map Property Boundary p Y Y Water Response to Completeness Check N H Cross Section A -A' Stormwater Wu-Yao Property o is ao 18430 Olympic View Drive 5-foot Topographic Contours ® Stormwater Discharge i Edmonds Washington (North Puget Sound 2017, NAVD88 feet) Feet — — — Landscaping Walls Q Downspout All feature locations are approximate ev Source: Utility and easement locations from City of Aspect MAY-2023 MAV/NLK FIGURE NO. Area of Landscaping Wall Repair p g p Edmonds GIS Web Map; https://maps.edmondswa.gov- /Html5Viewer/?viewer=Edmonds r_SSL.HTML ra SM coNsuIrlNc 2300 0020 --/ -/--- RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT APPENDIX A Geotechnical Assessment in Support of Landscaping Wall Repair (Aspect) %As ect CONSULTING June 8, 2023 RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Lilin Wu and Yutian Yao 18430 Olympic View Drive Edmonds, Washington 98020 City Of Edmonds Building Department -------------------------------------------- Work RETAINING WALL REPAIR , Address 8430 OLYMPIC VIEW DR --------- -------------------------- Owner Wu ---------------------------------- Approved Date Building Official Permit Number; BLD2024-0149 Re: Geotechnical Assessment in Support of Landscaping Wall Repair Parcel # 00565600200203 18430 Olympic View Drive Edmonds, WA 98020 Project No. 230020 Dear Lilin and Yutian: This letter report summarizes Aspect Consulting, LLC's (Aspect) geotechnical assessment of a steep slope and terraced landscaping wall (Project) on the subject property, also known as Snohomish County parcel number 00565600200203, located at 18430 Olympic View Drive in Edmonds, Washington (Site; Figure 1). We performed a Site reconnaissance, subsurface exploration, and geotechnical engineering evaluation in accordance with our proposal authorized by you on January 23, 2023, and a contract change authorized April 14, 2023. Our reconnaissance and subsurface exploration of the property were performed on January 24, 2023 and April 20, 2023, respectively. This letter presents the findings of our Site visits and subsurface exploration, and our conclusions and recommendations. Project Understanding On December 27, 2022, water and debris flooded from a 36-inch-diameter pipe that was buried within the lower portion of a terraced landscaping wall on the east side of the back yard. The flood damaged the lowest portion of the landscaping wall and deposited soil and debris in the back yard and residence. We understand you now wish to repair the landscaping wall and will seek a building permit from the City of Edmonds. The site of the proposed wall is in an area the City considers to have geologic hazards (Image 1). Edmonds Municipal Code Chapter 23.80 requires a geotechnical report be submitted when development work is proposed within a geologic hazard area. This geotechnical report fulfills that requirement. Site Conditions Aspect assessed the surface conditions of the Site through a literature review and field observations. Before our visit to the Site, we reviewed City and County critical area maps, State and Federal geologic maps, topographic maps and digital surface models derived from LiDAR, and current and historical aerial imagery. We also conducted visits to the Site and surrounding area on January 24, 2023, and performed a limited subsurface exploration on April 20,- 2023. The Site is a 0.26-acre residential parcel located along the east side of the Puget Sound in Edmonds, Washington (Figure 1). It is bounded by Olympic View Drive to the east and single-family residences to the north, west, and south (Figure 1). Access to the Site is via a shared, paved driveway from Olympic View Drive. RECEIVED Feb 06 2024 Wu Residence LandsICES ESDE�OP aRs June 8, 2023 DEPARTMENT Project No. 230020 The eastern portion of the Site consists of an approximately 25-foot-tall, bowl -shaped steep slope that extends from Olympic View Drive down to the east side of the Residence. This slope is terraced and each of the four terraces is supported by a landscaping wall built of concrete masonry units (CMU). The CMUs are each 6 inches high, 15 inches long, and 11 inches deep; the exposed height of the walls range in height from 3 to 4 feet. (Photograph 1, 2). The bottom CMU courses of each terraced wall are founded on several inches of compacted angular gravel and the lowest one to two courses of CMUs are embedded/buried. We understand that the terraced landscaping wall was constructed between 2020 and 2021. To the east, a detached carport is situated at the top of the terraced landscaping wall, with the parking elevation approximately 7 feet below the surface of Olympic View Drive. Your 2,023- square-foot residence sits to the west and below the lower terraced landscaping wall. During a storm event on December 27, 2022, stormwater discharged at high velocity from an existing 36-inch-diameter pipe located behind the lowest portion of the landscaping wall. We observed damage to the landscaping wall where water forcefully eroded the CMUs, soil, and vegetation in the vicinity of the pipe. We observed no damage to other parts of the landscaping wall. At the time of our reconnaissance, debris, including sand, gravel, cobbles, and concrete blocks, was deposited throughout the yard and against the north and east sides of the residence. .77 .i.�►i • ,gip;, . ,s- . , .. Photograph 1. Landscaping wall along the steep slope at the eastern edge of the Site. Pipe and damage to the wall visible in center of photo. Viewing east. Page 2 RECEIVED Feb 06 2024 Wu Residence Landsca�xins June 8, 2023 DEVE DEPARTMENT ICES Project No. 230020 Vt '--_ w Photograph 2. Site residence viewed from the top of the landscaping wall. Debris from flood visible extending towards residence. Viewing west. .S O Landslide and Erosion Hazard . Landslide Hazard Area 40% 0 Severe Erosion Hazard 15%-40% Image 1. The City's geologic hazard map designates the Site as having landslide and erosion hazard areas. Page 3 RECEIVED Feb 06 2024 Wu Residence LandsICES ESDE�OP aRs June 8, 2023 DEPARTMENT Project No. 230020 Surface Topography The Site slopes up to the east from approximate Elevation 1151 on the western edge to Elevation 145 on the eastern edge. The residence and back yard sit on a bench on the western and central part of the site. The terraced landscaping wall rises from the east side of the back yard, at approximate Elevation 120, to the carport at Elevation 140, at an inclination of about 45 degrees (100 percent). East of the carport the Site slopes up another 7 feet at an inclination of about 20 degrees (35 percent). Drainage No standing water or surface flow was observed at the time of our initial Site reconnaissance or during subsequent Site visits. We did observe evidence that water and debris had flowed from the pipe buried in the base of the bottom landscaping wall and across the back yard, but no water was flowing from it when we were on Site. Stormwater from the carport's paved surface and roof appears to be directed to the south along the shared paved driveway. Stormwater collected from roof gutter downspouts around the residence are "tightlined" into buried pipes which presumably are directed to municipal stormwater conveyance infrastructure. Surface drainage conditions as well as groundwater conditions at the Site will vary with fluctuations in precipitation, Site usage (such as irrigation), and off -Site land use. Vegetation The landscaping wall terraces are vegetated with small shrubs and grasses as well as several mature alders and Douglas -fir trees. Near the base of the landscaping wall, there are two 3- to 4-foot- diameter Douglas -fir trees, as well as a 4.5-foot diameter cedar stump. The alders and Douglas -fir trees are straight and vertical. Upslope of the wall, the slope is vegetated with English ivy, sword ferns, and herbaceous ground cover. No hydrophilic vegetation was observed anywhere on the site. Subsurface Conditions Subsurface conditions at the Site were inferred from our subsurface explorations advanced at the Site on April 20, 2023, review of applicable geologic literature, our experience with the local geology, and nearby well logs. The following sections discuss the results of our assessment (Figure 2). Geology The Site is located within the Puget Lowland, a broad area of tectonic subsidence flanked by two mountain ranges: the Cascades to the east and the Olympics to the west. The sediments within the Puget Lowland are the result of repeated cycles of glacial and nonglacial deposition and erosion. The most recent cycle, the Vashon Stade of the Fraser Glaciation (about 13,000 to 16,000 years ago), is responsible for most of the present day geologic and topographic conditions. During the Vashon Stade, the 3,000-foot-thick Cordilleran Glacier advanced into the Puget Lowland. As the Cordilleran Glacier advanced southward, lacustrine and fluvial sediments were deposited in front of the advancing ice sheet. These sediments were overridden and consolidated by the advancing glacier, creating dense and hard soil deposits referred to as "Vashon glacial advance deposits." At the interface between the advance soils and the glacial ice, the Cordilleran Glacier sculpted and smoothed the surface, and then deposited a consolidated basal till. As the Cordilleran Glacier 1 Elevations in feet referenced to the North American Vertical Datum of 1988 (NAVD88). Page 4 RECEIVED Feb 06 2024 Wu Residence LandsICES ESDE�OP aRs June 8, 2023 DEPARTMENT Project No. 230020 receded northward from the Puget Lowland to British Columbia, it left an unconsolidated sediment veneer over glacially consolidated deposits, referred to as "Vashon glacial recessional deposits." Geologic mapping (Minard, 1983) indicates that the Site is underlain by Vashon recessional outwash deposits. Vashon recessional outwash typically consists of loose to medium dense stratified sand, silt, and gravel that was deposited during the retreat of the Vashon ice sheet during the last glaciation in the Puget Sound region. The Vashon recessional outwash is generally well - draining and provides stable sites for construction. The geologic map implies that the recessional outwash is underlain by glacial advance deposits and pre -glacial to glacial transitional beds. Site Stratigraphy Subsurface conditions at the Site were inferred from the five hand -auger explorations completed for this study, visual reconnaissance of the Site, and review of applicable geologic literature. The following sections present a summary of subsurface conditions encountered in our hand -auger explorations, AHA-01 through AHA-05. Detailed descriptions of the soils encountered in our exploration, as well as the depths where characteristics of the soils changed, are indicated on the hand -auger logs in Appendix A. At several different depths within the explorations, we estimated the in situ density of the soil with dynamic cone penetrometer tests (DCPT). With the DCP test, a hammer of known weight is dropped a known distance onto an anvil, driving a cone of known dimensions into the soil. The number of blows per 1.75 inches of penetration is recorded and the blows compared to established standards (Sowers and Hedges, 1966). Topsoil We observed a layer of loose topsoil, several inches thick, consisting of sandy organic silt (symbol OL in the United Soil Classification System (USCS) (ASTM, 2018) and containing roots and wood debris, at the ground surface in all the explorations on the slope and terraces. Fill In some of the explorations, below the topsoil we encountered loose to medium dense sand with silt and gravel (symbol SP-SM). In the planted areas behind the landscaping walls, the fill had been placed to provide structural support and drainage to the walls. In some explorations, we were unable to advance into the fill due to the gravel content. We infer that a thick wedge of fill was placed to bury the 36-inch diameter pipe from which the flood emerged. That fill material is not shown on geologic maps and we encountered a few feet of it in one of our explorations, but we infer its presence based on the location of the pipe at the bottom of the slope. Colluvium Beneath the topsoil and fill, we encountered loose to medium dense, silty sand with gravel and cobbles (SM). This material contained silt- to gravel -sized fragments of decaying organic material. We interpret this material to be colluvium, the native material on the slope derived from the underlying material and modified by weathering and other shallow surface processes. Page 5 RECEIVED Feb 06 2024 Wu Residence LandsICES ESDE�OP aRs June 8, 2023 DEPARTMENT Project No. 230020 Vashon recessional outwash In two of the explorations, beneath the colluvium we encountered medium dense sand with silt and gravel (SP-SM) that we interpret as Vashon recessional outwash. The material was distinguished from colluvium by its near total lack of organic content. Groundwater No groundwater seepage was observed on our reconnaissance, and no groundwater was encountered in our hand -auger exploration. Geologic Hazards Erosion Hazard The City of Edmonds' Critical Areas map shows the steep slope in the eastern area of the Site as an erosion hazard area (City, 2023). We concur with the City's assessment. Bare soils at the Site are at risk for erosion due to the steepness of the slope, whether the exposure of the soil is due to slope failure, such as exists at the damaged section of wall, due to construction, or other causes. During the repair of the damaged section of the landscaping wall, the erosion hazard should be addressed through standard temporary erosion and sedimentation controls (TESC) and erosion best management practices (BMPs). The intact portions of the landscaping walls are currently demonstrably reducing the hazard of erosion on the Site, and erosion hazard will be permanently reduced once the repair of the damaged section of the wall is complete and the terraces are replanted. Landslide Hazards The City of Edmonds' Critical Areas map classifies the steep slope at the Site as having a high landslide hazard (City, 2023). The Washington Department of Ecology (Ecology, 1979) classifies the steep slope at the Site as "Unstable" regarding landslides due to the geology, groundwater, slope, or erosion factors. A USGS landslide survey shows that the Site is located adjacent to a known unstable slope area (Baum et al., 2000). After our assessment of the Site, we concur with the USGS, state, and City classifications. The Site, like similarly located sites around the Puget Sound, will continue to experience landslides. Construction of slope stability measures can substantially decrease the severity and frequency of landslides. Four types of landslides are possible on the Site and on similar sites and slopes along the shoreline in the Puget Sound area (Varnes, 1978): deep-seated rotational landslides, translational landslides, topples, and shallow flows. Deep -Seated Rotational Landslides Deep-seated rotational landslides consist of relatively deep (feet to tens of feet) failures that typically involve slipping along a curved shear plane. Rotational landslides may transport masses of semi -intact soil downslope, resulting in steep headscarps along the upper portion of the failure plane and level or back -rotated benches in the middle and bottom of the slope. At the Site, we did not observe any topographic evidence of recent or ancient rotational landslides, and we consider it very unlikely such a slide will occur in the future. Page 6 RECEIVED Feb 06 2024 Wu Residence LandsICES ESDE�OP aRs June 8, 2023 DEPARTMENT Project No. 230020 Translational Slides Translational landslides consist of the landslide mass moving down the slope along a roughly planar surface with little rotation or backward tilting. Translational landslides can transport large, more -or -less intact masses of soil downslope, resulting in steep headscarps at the upper portion of the failure and flat "islands" or blocks of material deposited on the bottom of the failure, often with intact vegetation and upright trees. We did not observe evidence of recent or ancient translational slides at the Site and we consider it very unlikely such a slide will occur in the future. Toppling Failures Toppling failures involve a mass of soil peeling off along tension cracks which form in soils at the crest of steep slopes and bluffs. These tension cracks may provide conduits for surface water migration and flow and they can promote growth of tree roots that can extend many feet downward into the cracks. As the roots grow and the face of the slope progresses through freeze -thaw cycles, or when the toe of the layer becomes oversteepened and undermined by erosion, these cracks often become failure planes, and a slab of soil will spall or topple off the slope face. Failures of this kind are typically a few feet thick and occur only on very steep to near -vertical slope sections. We did not observe evidence of recent or ancient toppling failures at the Site and we consider it very unlikely such a slide will occur in the future. Shallow Flow Landslides Shallow flow landslides consist of failures that involve sliding of loose fill, colluvium, and overlying vegetation that typically mantle steep slopes. Shallow flows are typically triggered by a significant increase in the moisture content within the upper few feet of soil on a slope and commonly result from periods of extended or heavy precipitation, groundwater seepage, or concentrated surface water discharge onto a slope. Shallow flows occur within the upper few feet of a slope and typically do not extensively affect the deep-seated or overall stability of a slope. The Site and nearby areas contain steep slopes that have experienced shallow flows in the past and are susceptible to shallow flow failures in the future. The likelihood of future shallow flow landslide activity is dependent upon factors affecting shallow groundwater such as precipitation, drainage, upslope development, root reinforcement from vegetation on the slope, and seismic forces. The existing terraced landscaping wall has reduced the likelihood of shallow landslides occurring at the Site and the proposed repair to the wall will further reduce the likelihood and severity. Conclusions Re -construction of the damaged landscaping wall will decrease the erosion and landslide hazard at the Site. If the repair is constructed in a manner similar to the existing walls, the walls will continue to reduce the likelihood and severity of erosion on the site. The pipe that the December flood came from was apparently believed to be abandoned and decommissioned, but obviously was not. After the flood, we understand the City has taken measures to fully and properly abandon this pipe to eliminate the possibility of further discharges onto the property. Page 7 RECEIVED Feb 06 2024 Wu Residence LandsICES ESDE�OP aRs June 8, 2023 DEPARTMENT Project No. 230020 It is our opinion that the steep slope at the Site is stable. We did not observe any signs of recent or ongoing slope instability. The large conifer and deciduous trees growing on the slope indicate that the slope has been stable for at least the past several decades, predating development of the Site. The construction of the existing terraced landscaping walls is adequate for their intended purpose. We did not observe wall construction, but we interviewed the homeowner who built the terraced landscaping walls. The subgrade appears to have been prepared properly and the base course of crushed rock appears to have been adequately compacted. The batter of the walls is at 1H:6V, which is appropriate for this setting. The walls have performed as intended since they were built we observed no settling or misalignment in the walls, even after the lowest wall was damaged by the storm event. From a geotechnical engineering perspective these terraced landscaping walls serve no structural purpose. The terraced landscaping walls do not support the carport above, or the house below them. Reconstructing the damaged portions of wall to match the original construction will not destabilize the slope nor any of the nearby developed infrastructure on the subject property. Recommendations Earthwork It is our opinion that basic excavation and grading necessary for the Project can be completed with hand tools. Appropriate erosion control measures should be implemented prior to beginning earthwork activities in accordance with the local regulations. Site Preparation Site preparation within the proposed construction area footprint should include removal of all debris and any other deleterious material. Additionally, all soils with significant root debris, and nonnative soils, within the proposed footing areas should be removed. Foundation No part of the retaining wall should be founded on or above yielding/loose or organic soils. All yielding, loose, or organic soil should be removed before the placement of the base course. The lowest course of CMUs should bear on a 4-inch (minimum) thick pad of compacted crushed rock. The bottom course of CMUs should be buried at least 6 inches (one block height) below the ground surface. Drainage Considerations The upslope side of the repaired wall should be provided with a drainage system consisting of clean, free -draining sand and gravel meeting the requirements of Section 9-03.12(4) of the WSDOT Standard Specifications for Gravel Backfill for Drains. The free -draining material should be at least 1 foot thick and should extend from the footing continuously upward to within 1 foot of the ground surface. Additional Project Design and Construction Monitoring An Aspect geo-professional should be present during wall re -construction to verify the foregoing recommendations have been properly implemented. The integrity of the wall depends on proper Site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event of variations in subsurface conditions. Page 8 RECEIVED Feb 06 2024 Wu Residence LandsICES ESDE�OP aRs June 8, 2023 DEPARTMENT Project No. 230020 This letter report is issued with the understanding that the information and recommendations contained herein will be incorporated into the Project, and that the necessary steps will be taken to verify that the builder carry out such recommendations in the field. We do not direct the builder's operations, and we cannot be responsible for the safety of personnel other than our own on the Site; the safety of others is the responsibility of the builder. The builder should notify appropriate personnel if he considers any of the recommended actions presented herein unsafe. References ASTM International (ASTM), 2018, Annual Book of ASTM Standards, West Conshohocken, Pennsylvania. Baum, R.L., Harp, E.L., and Hultman, W.A., 2000, Map showing recent and historic landslide activity on coastal bluffs of Puget Sound between Shilshole Bay and Everett, Washington, USGS, Miscellaneous Field Studies Map 2346. City of Edmonds GIS, 2023, https://maps.edmondswa.gov/, accessed March, 2023. Minard, J.P., 1983, Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, Washington, USGS, Miscellaneous Field Studies Map MF-1541. Sowers, G.F. and Hedges, C.S., Dynamic Cone for Shallow In -Situ Penetration Testing, ASTM STP 399, ASTM, 1966, p. 29. Varnes, D.J., 1978, Slope movement types and processes, in Schuster, R.L., and Krizek, R.J., eds., Landslides —Analysis and control: National Research Council, Washington, D.C., Transportation Research Board, Special Report 176, p. 11-33. Washington State Department of Ecology (Ecology), 1979, Coastal Zone Atlas of Washington, Shoreline and Coastal Zone Management Program, Volume 10, https:Hfortress.wa.gov/ecy/coastalatlas/tools/Map.aspx. Washington State Department of Transportation (WSDOT), 2021, Standard Specifications for Road, Bridge and Municipal Construction, Document M 41-10. Limitations The conclusions and recommendations provided above are based on the information collected during our Site reconnaissance, subsurface exploration, our experience with the local geology near the Site, and pertinent available published data. Within the limitations of scope, schedule, and budget, our services have been performed for Lilin Wu (Client), and this letter report was prepared in accordance with generally accepted geotechnical engineering and engineering geology practices in effect in this area at the time our letter report was prepared. This letter report does not represent a legal opinion. No other warranty, expressed or implied, is made. All reports prepared by Aspect Consulting for the Client apply only to the services described in the Agreement(s) with the Client. Any use or reuse by any party other than the Client is at the sole risk of that party, and without liability to Aspect Consulting. Aspect Consulting's original files/reports shall govern in the event of any dispute regarding the content of electronic documents furnished to others. Page 9 RECEIVED Feb 06 2024 Wu Residence Lands ICES ESDEP@NERs June 8, 2023 DEPARTMENT Project No. 230020 We are able to offer further assistance with this project, if desired. Please contact us to coordinate these activities. It has been a pleasure to provide these services to you. If you have any questions, please do not hesitate to call. Sincerely, Aspect consulting, LLC 36468 t 1STE09 6/8/2023 Erik O. Andersen, PE Principal Engineer eandersen@aspectconsulting.com Attachments Figure 1 — Site Map Figure 2 — Geologic Cross Sectiono Appendix A — Boring Logs V:\230020 Wu Property Geotech Srvcs\Deliverables\Wu Letter Report_6.8.23.docx /off w ash Engineering Geologist 2931 ed Geoff° 6/8/2023 Matthew A. von der Ahe Matthew von der Ahe, LEG Project Geologist mvonderahe@aspectconsulting.com Page 10 RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT FIGURES RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT a ti Jt0 T A O 5 O Oh 1°O ti AHA-04 AHA-05 �, 3 Too titi° AHA-02 � 1ss c� AHA-01 a AHA-03 0 JQS TQ S ISO 0 Hand Auger � Site Map ✓lid House N Geotechnical Report rMl Property Boundary Wu-Yao Property B 15 30 18430 Olympic View Drive H Cross Section A -A' I Feet Edmonds Washington (� . 5-foot Topographic Contours By FIGURE NO. �./ (North Puget Sound 2017, NAVD88 feet) Aspect MAY-2023 MAV / NLK 'Aspect 1 PROIECTNO. REVISED BM 230020 --- / --- A 20 West 15 5 Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Original Location of Damaged Landscaping Wall L Fence Asphalt Carport Geotexti le Landscaping / Wall / N I / n Geotextile / n/ / Colluvium j/. / Recessional Outwash / n 0 Abandoned Drainage Pipe// E / 20 A' East 15 F-- W W 10 LD 5 o — 0 0 5 10 15 20 25 30 35 DISTANCE (FEET) Legend Lithology Graphics Contacts DISCLAIMER: The subsurface conditions presented in this Geologic Cross Section Recent Debris F-1 Flow Deposits Colluvium Contact - Observed 0 2.5 5 Feet geologic cross section are conceptual. Variations may exist between the soil and groundwater conditions depicted on thoseis repo Landactually oringl gsforhurthercont to the contents of this report and boring logs for further context. contents of Geotechnical Report Wu Yao Property 18430 Olympic View Drive Topsoil Recessional Outwash Contact - Inferred Horizontal Scale 1" = 2.5' Notes:•Cross section surface generated from field measurments obtained by Aspect staff. Edmonds, Washington Vertical Scale 1" = 2.5' Site features and exploration locations are �,spect /CONSULTING MAY-2023 Br. SBC FIGURE NO. 2 —7— —7— —7— —7— Vertical Exaggeration 1x Fill Contact - Queried approximate. PROJECT 0 230020 REVISED BY: MVA RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT APPENDIX A Boring Logs RECEIVED . 0 . 0 e 0 0 Well -graded a1 F6MONDs 0 ; o 0000 GW Well-grad®"IRW&WETOIZ ND LL c DEPARTMENT N N N In > LL c o0000 in NI00000 Poorly -graded GRAVEL 0 0 00000 GP Poorly graded GRAVEL WITH SAND o CN ci 6 0 Z 00000 00000 o LID o 00.0 r GM SILTY GRAVEL -oo W cc u o 0" 0 SILTY GRAVEL WITH SAND a� 6K 'm o aNi NI CLAYEY GRAVEL o GC CLAYEY GRAVEL WITH SAND LO cs Ln c m � o Well -graded SAND o Well -graded SAND WITH GRAVEL g LL- a.... _ o iZ . - U) 0 wl -=. -- Poorly -graded SAND :_ SP Poorly -graded SAND WITH GRAVEL qai o m o Z N o (n SM SILTY SAND SILTY SAND WITH GRAVEL co o a c - SAND 0 LO �CLAYEY SC CLAYEY SAND WITH GRAVEL SILT ML SANDY or GRAVELLY SILT > LLO SILT WITH SAND m in c co SILT WITH GRAVEL o s 0 w LEAN CLAY o c Zn CL SANDY or GRAVELLY LEAN CLAY Z m �, LEAN CLAY WITH SAND On LEAN CLAY WITH GRAVEL U) a — ORGANIC SILT m a — — IL SANDY or GRAVELLY ORGANIC SILT m o _ — — ORGANIC SILT WITH SAND 2 � ORGANIC SILT WITH GRAVEL O ELASTIC SILT o °' SANDY or GRAVELLY ELASTIC SILT Ln o MH ELASTIC SILT WITH SAND rn T ELASTIC SILT WITH GRAVEL cc 0 c0 5 ,� FAT CLAY c LOLn CH SANDY or GRAVELLY FAT CLAY m = FAT CLAY WITH SAND E J FAT CLAY WITH GRAVEL CJ= ORGANIC CLAY ii a i��ii OH SANDY or GRAVELLY ORGANIC CLAY ORGANIC CLAY WITH SAND ORGANIC CLAY WITH GRAVEL T.E D PEAT and other oU) PT mostly organic soils "WITH SILT" or "WITH CLAY" means 5 to 15%silt and clay, denoted by a "" in the group name; e.g., SP-SM . "SILTY" or "CLAYEY" means >15%silt and clay. "WITH SAND" or "WITH GRAVEL" means 15 to 30%sand and gravel.. "SANDY" or "GRAVELLY" means >30%sand and gravel.. "Well -graded" means approximately equal amounts of fine to coarse grain sizes. "Poorly graded" means unequal amounts of grain sizes . Group names separated by "/" means soil contains layers of the two soil types; e.g., SM/ML. Soils were described and identified in the field in general accordance with the methods described in ASTM D2488. Where indicated in the log, soils were classified using ASTM D2487 or other laboratory tests as appropriate. Refer to the report accompanying these exploration logs for details. 1. Estimated or measured percentage by dry weight 2. (SPT) Standard Penetration Test (ASTM D1586) 3. Determined by SPT, DCPT (ASTM STP399) or other field methods. See report text for details. MC = Natural Moisture Content GEOTECHNICAL LAB TESTS PS = Particle Size Distribution FC = Fines Content (% < 0.075 mm) GH = Hydrometer Test AL = Atterberg Limits C = Consolidation Test Str = Strength Test OC = Organic Content (% Loss by Ignition) Comp = Proctor Test K = Hydraulic Conductivity Test SG = Specific Gravity Test Organic Chemicals CHEMICAL LAB TESTS BTEX = Benzene, Toluene, Ethylbenzene, Xylenes TPH-Dx = Diesel and Oil -Range Petroleum Hydrocarbons TPH-G = Gasoline -Range Petroleum Hydrocarbons VOCs = Volatile Organic Compounds SVOCs = Semi -Volatile Organic Compounds PAHs = Polycyclic Aromatic Hydrocarbon Compounds PCBs = Polychlorinated Biphenyls Metals RCRA8 = As, Ba, Cd, Cr, Pb, Hg, Se, Ag, (d = dissolved, t = total) MTCA5 = As, Cd, Cr, Hg, Pb (d = dissolved, t = total) PP-13 = Ag, As, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, TI, Zn (d=dissolved, t=total) PID = Photoionization Detector FIELD TESTS Sheen = Oil Sheen Test SPT2 = Standard Penetration Test NSPT = Non -Standard Penetration Test DCPT = Dynamic Cone Penetration Test Descriptive Term Size Range and Sieve Number COMPONENT Boulders = Larger than 12 inches DEFINITIONS Cobbles = 3 inches to 12 inches Coarse Gravel = 3 inches to 3/4 inches Fine Gravel = 3/4 inches to No. 4 (4.75 mm) Coarse Sand = No. 4 (4.75 mm) to No. 10 (2.00 mm) Medium Sand = No. 10 (2.00 mm) to No. 40 (0.425 mm) Fine Sand = No. 40 (0.425 mm) to No. 200 (0.075 mm) Silt and Clay = Smaller than No. 200 (0.075 mm) % by Weight Modifier % by Weight Modifier ESTIMATED' <1 = Subtrace 15 to 25 = Little PERCENTAGE 1 to <5 = Trace 30 to 45 = Some 5 to 10 = Few >50 = Mostly Dry = Absence of moisture, dusty, dry to the touch MOISTURE Slightly Moist = Perceptible moisture CONTENT Moist = Damp but no visible water Very Moist = Water visible but not free draining Wet = Visible free water, usually from below water table Non -Cohesive or Coarse -Grained Soils RELATIVE DENSITY Density3 SPT2 Blows/Foot Penetration with 1/2" Diameter Rod Very Loose = 0 to 4 >_ 2' Loose = 5 to 10 1' to 2' Medium Dense = 11 to 30 3" to 1' Dense = 31 to 50 1" to 3" Very Dense = > 50 < 1" Cohesive or Fine -Grained Soils CONSISTENCY Consistency3 SPT2 Blows/Foot Manual Test Very Soft = 0 to 1 Penetrated >1" easily by thumb. Extrudes between thumb & fingers. Soft = 2 to 4 Penetrated 1/4" to 1" easily by thumb. Easily molded. Medium Stiff = 5 to 8 Penetrated >1/4" with effort by thumb. Molded with strong pressure. Stiff = 9 to 15 Indented —1/4" with effort by thumb. Very Stiff = 16 to 30 Indented easily by thumbnail. Hard = > 30 Indented with difficulty by thumbnail. GEOLOGIC CONTACTS Observed and Distinct Observed and Gradual Inferred Aspect CONSULTING Exploration Log Key �Ca�CI\/C11 u si eence - 230020 Geotechnical Ex loration Log %0��RFct P ress & Site Specific Locafion Coordinates (Lat,Lon WGS84) Exploration Number I N G 184WOgfrov DrViCESive, Edmonds, WA, Refer to Figure 2 47.8313,-122.3610 (est) AHA-� 1 Contractor U 1RTMENT Sampling Method Ground Surface Elev. Aspect Consulting Hand Auger Grab 125' (est) Operator Exploration Method(s) Work StarbCompletion Dates Top of Casing Elev. Depth to Water (Below GS) MRH/SBC Hand tools 4/20/2023 NA No Water Encountered Depth Elev. Exploration Notes and Sample Blows/foot • water Content/)* Blows/6 Tests Material Description Depth (feet) (feet) Completion Details Type/ID 050 Type (ft) COLLUVIUM SILTY SAND (SM); very loose, slightly moist, orange brown; fine to coarse sand; fine, subrounded to subangular excavated with excavated material - organic material. ravel; trace or g g 1 124 53 DCPT=2,2,4 - 2 123 — — 2 SILTY SAND WITH GRAVEL (SM); loose, slightly moist, orange brown; fine to coarse sand; fine to coarse, subrounded to subangular gravel; iron -oxide staining; 3 122 M — — DCPT=6,9,a - woody debris; gravel -sized dark organic fragments. 3 4 121 — — — 4 a DCPT SILTY SAND WITH GRAVEL AND COBBLES (SM); -6,1z,16 medium dense, moist, orange brown; fine to coarse sand; fine to coarse, subrounded to subangular gravel; subrounded cobbles; gravel -sized dark organic fragments; diamict. 5 120 DCPT 5 =11,12,14 DCPT 6 =11,12,20 Difficult augering 7 118 RECESSIONAL OUTWASH - SAND WITH SILT, GRAVEL, AND COBBLES (SP-SM); DCPT _ medium dense, moist, brown; fine to trace coarse sand; =10,14,16 fine to trace coarse, subrounded to subangular gravel; subrounded cobbles. DCPT=20 - Refusal on gravel and cobbles Bottom of exploration at 8.7 ft. bgs. 9 116 — — — 9 Legend Plastic Limit Liquid Limit � E 0. a_® 75 Grab sample @ > No Water Encountered See Exploration Log Key for explanation of symbols Exploration Log Logged by: MRH/SBC in l_ AHA-01 Approved by: MvA 5/20/2023 Sheet 1 of 1 �C�CI\/C11 u si eence - 230020 Geotechnical Ex loration Log %0��RFct P ress & Site Specific Locafion Coordinates (Lat,Lon WGS84) Exploration Number I N G 184WOgfrov DrViCESive, Edmonds, WA, Refer to Figure 2 47.8313,-122.3609 (est) AHA-02 Contractor U 1RTMENT Sampling Method Ground Surface Elev. Aspect Consulting Hand Auger Grab 157' (est) Operator Exploration Method(s) Work StarbCompletion Dates Top of Casing Elev. Depth to Water (Below GS) MRH/SBC Hand tools 4/20/2023 NA No Water Encountered Depth Elev. Exploration Notes and Sample Blows/foot • water Content/)* Blows/6 Tests Material Description Depth (feet) (feet) Completion Details Type/ID 050 Type (ft) — —_ TOPSOIL SANDY ORGANIC SILT (OL); very loose, slightly moist, dark brown; garden bed. FILL - -- SAND WITH SILT AND GRAVEL (SP-SM); very loose, slightly moist, dark brown; fine to coarse sand; fine gravel. 1 SILTY SAND WITH GRAVEL (SM); very loose, slightly moist, brown; fine to coarse sand; fine to coarse, _ subrounded to subangular gravel; gravel -sized woody DCPT=3,4,4 -- - - debris, organic fragments. 2 155 — — 2 N DCPT=4,3,3 -- - 3 154 — — 3 4 153 — — — SILTY SAND WITH GRAVEL (SM); loose, slightly moist, 4 light brown; fine to coarse sand; fine to coarse, M subrounded to subangular gravel; trace cobbles; iron -oxide (n DCPT staining; gravel -sized dark organic fragments. Refusal on gravel and cobbles =7.7,10 Bottom of exploration at 4.7 ft. bgs. 5 152 5 6 151 — — 6 7 150 — — 7 8 149 — — — 8 9 148 — — — 9 Legend Plastic Limit t---i Liquid Limit � E 0. T 75 ® Grab sample @ > No Water Encountered See Exploration Log Key for explanation of symbols Exploration Log Logged by: MRH/SBC in l_ AHA-02 Approved by: MvA 5/20/2023 Sheet 1 of 1 �C�CI\/C11 u esi ence - 230020 Geotechnical Ex loration Log %0��RFct P ress & Site Specific Locafion Coordinates (Lat,Lon WGS84) Exploration Number I N G 184WOgfrov DrViCESive, Edmonds, WA, Refer to Figure 2 47.8313,-122.3610 (est) AHA-03 Contractor U 1RTMENT Sampling Method Ground Surface Elev. Aspect Consulting Hand Auger Grab 137' (est) Operator Exploration Method(s) Work StarbCompletion Dates Top of Casing Elev. Depth to Water (Below GS) MRH/SBC Hand tools 4/20/2023 NA No Water Encountered Depth (feet) Elev. (feet) Exploration Notes and Completion Details Sample Type/ID Blows/foot • water Content/)* Blows/6 Tests Material Type Description Depth (ft) 050 _ = TOPSOIL SANDY ORGANIC SILT (OL); very loose, slightly moist, dark brown; garden bed; geotextile at 3 inches bgs. FILL SILTY SAND WITH GRAVEL (SM); very loose, slightly moist, brown; fine to coarse sand; fine to coarse, 1 136 — — — subrounded to subangular gravel; trace rootlets; 0.5 to 1 1-inch-thick charcoal fragments; brick fragments. DCPT=2,3,4 -- 2 135 — — 2 SILTY SAND (SM); loose, slightly moist, tan; fine to DCPT medium sand; fine to coarse, subrounded to subangular Refusal on gravel and =12,7,9 gravel. cobbles Bottom of exploration at 2.7 ft. bgs. 3 134 — — 3 4 133 — — — 4 5 132 5 6 131 — — 6 7 130 — — 7 8 129 — — — 8 9 128 — — — 9 Legend Plastic Limit t---i Liquid Limit � E 0. T 75 ® Grab sample @ > No Water Encountered See Exploration Log Key for explanation of symbols Exploration Log Logged by: MRH/SBC in I— AHA-03 Approved by: MvA 5/20/2023 Sheet 1 of 1 �C�CI\/C11 u sI eence - 230020 Geotechnical Ex loration Log %0��RFct P ress & Site Specific Locafion Coordinates (Lat,Lon WGS84) Exploration Number I N G 184WOgfrov DrViCESive, Edmonds, WA, Refer to Figure 2 47.8314,-122.3609 (est) AHA-04 Contractor U 1RTMENT Sampling Method Ground Surface Elev. Aspect Consulting Hand Auger Grab 137' (est) Operator Exploration Method(s) Work StarbCompletion Dates Top of Casing Elev. Depth to Water (Below GS) MRH/SBC Hand tools 4/20/2023 NA No Water Encountered Depth Elev. Exploration Notes and Sample Blows/foot • water Content/)* Blows/6 Tests Material Description Depth (feet) (feet) Completion Details Type/ID 050 Type (ft) — — TOPSOIL — — - SANDY ORGANIC SILT (OL); very loose, slightly moist, dark brown; garden bed; geotextile at 3 inches bgs. COLLUVIUM SILTY SAND WITH GRAVEL (SM); loose, slightly moist, tan; fine to coarse sand; fine to coarse, subrounded to subangular gravel; trace gravel -sized dark organic 1 fragments. 2 135 N — — DCPT Becomes medium dense 2 =5,12,14 3 134 — — DCPT=5,5,7 - 3 4 133 5 M DCPT=2,5,7 RECESSIONAL OUTWASH 5 132 Refusal on gravel and SILTY SAND WITH GRAVEL (SM); medium dense, 5 cobbles lightly moist, yellow brown; fine to coarse sand; fine to Soarse, subrounded gravel. Bottom of exploration at 5 ft. bgs. 6 131 — — 6 7 130 — — 7 8 129 — — — 8 9 128 — — — 9 Legend Plastic Limit t---i Liquid Limit � E 0. T 75 ® Grab sample @ > No Water Encountered See Exploration Log Key for explanation of symbols Exploration Log Logged by: MRH/SBC in l_ AHA-04 Approved by: MvA 5/20/2023 Sheet 1 of 1 �C�CI\/C11 u esI ence - 230020 Geotechnical Ex loration Log %0��RFct P ress & Site Specific Locafion Coordinates (Lat,Lon WGS84) Exploration Number I N G 184WOgfrov DrViCESive, Edmonds, WA, Refer to Figure 2 47.8314,-122.3610 (est) AHA-05 Contractor U 1RTMENT Sampling Method Ground Surface Elev. Aspect Consulting Hand Auger Grab 134' (est) Operator Exploration Method(s) Work StarbCompletion Dates Top of Casing Elev. Depth to Water (Below GS) MRH/SBC Hand tools 4/20/2023 NA No Water Encountered Depth Elev. Exploration Notes and Sample Blows/foot • water Content/)* Blows/6 Tests Material Description Depth (feet) (feet) Completion Details Type/ID 050 Type (ft) _ = TOPSOIL SANDY ORGANIC SILT (OL); very loose, slightly moist, dark brown; abundant organic material, roots. COLLUVIUM SILTY SAND WITH GRAVEL AND COBBLES (SM); loose, slightly moist, light brown to brown; fine to coarse 1 133 — — — sand; fine to coarse, subrounded to subangular gravel; 1 subrounded cobbles. 2 132 — — 2 DCPT=3,4,5 -- - 3 131 — — 3 Refusal on gravel and cobbles Bottom of exploration at 3.5 ft. bgs. 4 130 — — — 4 5 129 5 6 128 — — 6 7 127 — — 7 8 126 — — — 8 9 125 — — — 9 Legend Plastic Limit t---i Liquid Limit � E 0. T 75 ® Grab sample @ > No Water Encountered See Exploration Log Key for explanation of symbols Exploration Log Logged by: MRH/SBC in I— AHA-05 Approved by: MvA 5/20/2023 Sheet 1 of 1 RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT APPENDIX B Response to City of Edmonds Building Permit Submittal Completeness Check (Aspect) RECEIVED Feb 06 2024 CITY OF EDMONDS s OPMENT SE e c t DEVELDEPARTMENRVICES A Rc Company November 15, 2023 Lilin Wu and Yutian Yao 18430 Olympic View Drive Edmonds, Washington 98020 Re: Response to City of Edmonds Building Permit Submittal Completeness Check City of Edmonds Permit BLD2023-1121 Aspect Project No. AS23002OA-03 Dear Lilin and Yutian: This letter is provided as a response to a review and correction notice from Donoval Akau with the City of Edmonds (City) dated September 11, 2023, for Aspect Consulting's (Aspect) work at 18430 Olympic View Drive, Edmonds, Washington 98020 (Site). We understand that the existing steep Site slope meets the City's definition of an environmentally critical area (ECA). We also understand and acknowledge that these non-structural landscaping walls were constructed without a building permit. Based on visual inspection following the extreme stormwater blowout and resulting localized wall failure, Aspect concludes that the existing un-failed sections of terraced landscaping wall are adequately stable under normal static loading conditions. These terraced landscaping walls should continue to serve their intended purpose as non-structural site features. See Photo 1 below. Only a limited portion of the block wall failed due to the stormwater flood. We understand that the owner now wishes to rebuild the failed sections to match the existing un-failed sections. RECEIVED Feb 06 2024 Lilin Wu and Yutian YaVOF EDMONDS DEVELOPMENT SERVICES November 15, 2023 DEPARTMENT Project No. AS230020A-03 Photo 1: Landscaping walls, showing damaged section of bottom wall and intact and functioning upper walls. From a geotechnical engineering and slope stability perspective, Aspect concludes that re- constructing the failed sections of wall will (a) not destabilize the overall slope on the subject or adjacent properties, and (b) will serve to reduce the potential for localized erosion during heavy rainfall events. In addition, Aspect provides these specific recommendations for non-structural landscaping block wall re -construction. See Figure 1. • The subgrade along the re -constructed wall area should be prepared by removal of existing organic rich debris until suitable mineral soil is encountered. An Aspect geo-professional should observe and verify suitable subgrade. The exposed and approved subgrade should be compacted using a hand tamper or small walk -behind vibratory plate compactor. • A leveling/bearing pad consisting of imported 5/8- or 3/4-inch clear crushed rock should be placed over the prepared subgrade and up to the proper block elevation. The clear crushed rock leveling/bearing pad material should be placed in 3-inch-thick lifts and compacted to a dense, unyielding condition using a hand tamper or a small walk -behind vibratory plate compactor. Page 2 RECEIVED Feb 06 2024 Lilin Wu and Yutian YaVOF EDMONDS DEVELOPMENT SERVICES November 15, 2023 DEPARTMENT Project No. AS23002OA-03 • Existing (or new matching) pre -cast concrete landscaping blocks may then be placed over the prepared leveling/bearing pad. The base course of block should be buried one full block height (6 inches) below the final ground surface in front (downslope) of the wall. • Successive courses of block should be staggered by a half -block, to avoid any continuous vertical joints in the face of the block wall. • Wall backfill within the reconstructed zone should consist of the same imported 5/8- or 3/4- inch clear crushed rock as used for levelingibearing pad. The "clear crushed" material is sometimes also referred to a "rock chips." Aspect can provide guidance as to suitable sources of clear crushed rock material. Aspect should approve the material prior to placement. • The compacted clear crushed rock will have high shear strength and will be freely draining. Any groundwater or infiltrated stormwater will quickly seep through the material and under the wall. No additional drainage measures such as perforated pipes are necessary. • Wall backfill behind the blocks should be systematically placed in approximately 3-inch horizontal layers and compacted using a hand tamper or walk -behind vibratory plate compactor. • An organic -rich topsoil planting layer may be placed at the very top of the completed wall to promote establishment of landscape plantings. Plantings should be small shrubs or ground cover. Large, deep -rooting trees are discouraged as their roots will tend to deform the wall over time. Limitations Work for this project was performed for Lilin Wu and Yutian Yao (Client), and this report was prepared consistent with recognized standards of professionals in the same locality and involving similar conditions, at the time the work was performed. No other warranty, expressed or implied, is made by Aspect Consulting (Aspect). Recommendations presented herein are based on our interpretation of site conditions, geotechnical engineering calculations, and judgment in accordance with our mutually agreed -upon scope of work. Our recommendations are unique and specific to the project, site, and Client. Application of this report for any purpose other than the project should be done only after consultation with Aspect. Variations may exist between the soil and groundwater conditions reported and those actually underlying the site. The nature and extent of such soil variations may change over time and may not be evident before construction begins. If any soil conditions are encountered at the site that are different from those described in this report, Aspect should be notified immediately to review the applicability of our recommendations. Page 3 RECEIVED Feb 06 2024 Lilin Wu and Yutian YaVOF EDMONDS DEVELOPMENT SERVICES November 15, 2023 DEPARTMENT Project No. AS23002OA-03 Risks are inherent with any site involving slopes and no recommendations, geologic analysis, or engineering design can assure slope stability. Our observations, findings, and opinions are a means to identify and reduce the inherent risks to the Client. It is the Client's responsibility to see that all parties to this project, including the designer, contractor, subcontractors, and agents, are made aware of this report in its entirety. If project developments result in changes from the preliminary project information, Aspect should be contacted to determine if our recommendations contained in this report should be revised and/or expanded upon. The scope of work does not include services related to construction safety precautions. Site safety is typically the responsibility of the contractor, and our recommendations are not intended to direct the contractor's site safety methods, techniques, sequences, or procedures. The scope of our work also does not include the assessment of environmental characteristics, particularly those involving potentially hazardous substances in soil or groundwater. All reports prepared by Aspect for the Client apply only to the services described in the Agreement(s) with the Client. Any use or reuse by any party other than the Client is at the sole risk of that party, and without liability to Aspect. Aspect's original files/reports shall govern in the event of any dispute regarding the content of electronic documents furnished to others. Please refer to Appendix A titled "Report Limitations and Guidelines for Use" for additional information governing the use of this report. Page 4 RECEIVED Feb 06 2024 Lilin Wu and Yutian YaIDOF EDMONDS DEVELOPMENT SERVICES November 15, 2023 DEPARTMENT We appreciate the opportunity to perform these services. Sincerely, Aspect consulting k1'EngineeringGeoogy�Se 29Ge0�011/15/23 Matthew A. von der Ahe Matthew von der Ahe, L.E.G. Project Geologist Matthew.vonderAhe@aspectconsulting.com Project No. AS23002OA-03 15/23 Erik O. Andersen, P.E. Senior Principal Geotechnical Engineer erik.andersen@aspectconsulting.com Attachments: Figure 1 — Reconstructed Landscaping Block Wall Geologic Cross Section Appendix A — Report Limitations and Guidelines for Use V:\230020 Wu Property Geotech Srvcs\Deliverables\Wu Residence - Review and Correction Response.docx Page 5 RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT FIGURES 20 20 A A' West CD9vNLMm V(U OTES East Fence • The subgrade along the re-aMmrW gall area should be prepared by removal ` \\y, of existing organic rich debris until suitable mineral soil is encountered. An Aspect Asphalt geo-professional should observe and verify suitable subgrade. The exposed and approved subgrade should be compacted using a hand tamper or small walk -behind Carport vibratory plate compactor. • A leveling/bearing pad consisting of imported 5/8- or 3/4-inch clear crushed rock should be placed over the prepared subgrade and up to the proper block elevation. Geotextl l e • The clear crushed rock leveling/ bearing pad material should be placed in 3-inch-thick lifts and compacted to a dense, unyielding condition using a hand tamper or a small walk -behind vibratory plate compactor. • Existing (or new matching) pre -cast concrete landscaping blocks may then be placed over the prepared leveling/bearing pad. The base course of block should be buried one full block height (6 inches) below the final ground surface in front Existing, Intact 15 (downslope) of the wall. 15 • Successive courses of block should be staggered by a half -block, to avoid any Landscaping Wall continuous vertical joints in the face of block wall. • Wall backfill within the reconstructed zone should consist of imported 5/8- or "clear N 3/4-inch clear crushed rock, as shall be used for leveling/bearing pad. The crushed" material is sometimes also referred to as "rock chips." Aspect can provide Q guidance as to suitable sources of clear crushed rock material. Aspect should approve the material prior to placement. a • The compacted clear crushed rock will have high shear strength and will be freely draining. Any groundwater or infiltrated stormwater will quickly seep through the material and under the wall. No additional drainage measures -such as perforated pipes - are necessary. • Wall backfill behind the blocks should be systematically placed in approximately 3-inch horizontal layers and compacted using a hand -tamper or walk -behind vibratory LLJ w plate compactor. LU 11 •An organic -rich topsoil planting layer may be placed at the very top of the completed 6-inches Geotextile - -•••—•••— - LU wall to promote establishment of landscape plantings. Plantings should be small = 10 shrubs or ground cover. Large, deep -rooting trees are discouraged as their roots will Topsoil 10 = 0 tend to deform the wall over time. 0 w 2 — w 2 Reconstruct Wall at Original Location . Colluvium 6-inch Minimum a n Embedment oDaa o:. — Recessional Outwash 5 Compacted 5/8- or 5 Below Finished 000'o°��? 3/4-inch Clean Grade Crushed Rock oQq�D. 000�Q' o�oD.a Abandoned Draina a Pipe v O� 4• 4.Q' ? 'off' oO •�a •0 4 : • a Debris Removed to Expose 2H:1V o o.�e a O D °.ca °.ca . Max oo°��'�oa�oo�Q�oa�oo�Q o Compentent Subgrade '�� o®`���� ��� •O'�%o. t>a•O'QO.oD.taa••O•. ... ... .. ... ... moo' �.v• Q��' �.v � Q. - - 0 0 0 5 10 15 20 25 30 35 DISTANCE (FEET) Legend Reconstructed Landscaping Lithology Graphics Contacts DISCLAIMER: The subsurface conditions presented in this geologic cross section are conceptual. Variations may exist Block Wall Geologic Cross Section ®•a° 3/4-inch Clean ■ C011uViurn 0 2.5 5 between the soil and groundwater conditions depicted on Response to Correction Notice Crushed Rock Contact -Observed this figure and those actually underlying the site. Refer to the this boring logs for further Wu-Yao Property Feet contents of report and context. Topsoil ■ Recessional Outwash Contact -Inferred Horizontal Scale 1" = 2.5' Notes: •meaCross section surfacegenerated byAspecfrom staf. field measurments obtained by Aspect staff. 18430 Olympic View Drive Edmonds, Washington Vertical Scale 1" = 2.5' -Site features and exploration locations are �,spect NOV-2023 Br. SBC FIGURE NO. —7— —7— —7— —7— o Vertical Exaggeration 1x Fill Contact Queried approximate. PROJECT NO. REVISED BY: p, �coNSULTING 230020 MVA/EOA RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT APPENDIX A Report Limitations and Guidelines for Use RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT REPORT LIMITATIONS AND GUIDELINES FOR USE Geoscience is Not Exact The geoscience practices (geotechnical engineering, geology, and environmental science) are far less exact than other engineering and natural science disciplines. It is important to recognize this limitation in evaluating the content of the report. If you are unclear how these "Report Limitations and Guidelines for Use" apply to your project or property, you should contact Aspect Consulting (Aspect). This Report and Project -Specific Factors Aspect's services are designed to meet the specific needs of our clients. Aspect has performed the services in general accordance with our agreement (the Agreement) with the Client (defined under the Limitations section of this project's work product). This report has been prepared for the exclusive use of the Client. This report should not be applied for any purpose or project except the purpose described in the Agreement. Aspect considered many unique, project -specific factors when establishing the Scope of Work for this project and report. You should not rely on this report if it was: • Not prepared for you; • Not prepared for the specific purpose identified in the Agreement; • Not prepared for the specific subject property assessed; or • Completed before important changes occurred concerning the subject property, project, or governmental regulatory actions. If changes are made to the project or subject property after the date of this report, Aspect should be retained to assess the impact of the changes with respect to the conclusions contained in the report. Reliance Conditions for Third Parties This report was prepared for the exclusive use of the Client. No other party may rely on the product of our services unless we agree in advance to such reliance in writing. This is to provide our firm with reasonable protection against liability claims by third parties with whom there would otherwise be no contractual limitations. Within the limitations of scope, schedule, and budget, our services have been executed in accordance with our Agreement with the Client and recognized geoscience practices in the same locality and involving similar conditions at the time this report was prepared Property Conditions Change Over Time This report is based on conditions that existed at the time the study was performed. The findings and conclusions of this report may be affected by the passage of time, by events such as a change in property use or occupancy, or by natural events, such as floods, earthquakes, slope instability, or groundwater fluctuations. If any of the described events may have occurred following the issuance of the report, you should contact Aspect so that we may evaluate whether changed conditions affect the continued reliability or applicability of our conclusions and recommendations. RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT ASPECT CONSULTING Geotechnical, Geologic, and Environmental Reports Are Not Interchangeable The equipment, techniques, and personnel used to perform a geotechnical or geologic study differ significantly from those used to perform an environmental study and vice versa. For that reason, a geotechnical engineering or geologic report does not usually address any environmental findings, conclusions, or recommendations (e.g., about the likelihood of encountering underground storage tanks or regulated contaminants). Similarly, environmental reports are not used to address geotechnical or geologic concerns regarding the subject property. We appreciate the opportunity to perform these services. If you have any questions, please contact the Aspect Project Manager for this project. RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT APPENDIX C Building Permit Submittal Completeness Check (City of Edmonds) RECEIVED ENGINEERING DIVISION Feb 0ED CITY OF D Idin Permit Submittal DEVELOPMENT DEPARTMENT Completeness Check PERMITTING & DEVELOPMENT 121 5th Avenue N P: 425.771.0220 www.edmondswa.gov www.maps.edmondswa.gov Project Name: Wu — Retaining Wall Repair Reviewer: Natalie Griggs Address: 18430 Olympic View Dr Date: September 8, 2023 The Engineering Division has noted the following deficiencies in the permit application. The applicant shall address each item identified prior to building permit application acceptance. OK Incomplete N/A Have the following REPORTS/DOCUMENTS been provided? X Transportation Impact Analysis — Appendix A (worksheet) or Appendix B (study) X Stormwater Report consistent with ECDC 18.30 and 2014 DOE Manual or Stormwater Memo if part of a subdivision X Geotechnical Report — See Checklist #4 for Infiltration Test Requirements X Water/Sewer Availability Determination — see City website for applications OK Incomplete N/A PLANS X Site Development Plan X Temporary Erosion & Sedimentation Control and Tree Retention Plan X Utility Plans —Water, Sewer, Storm, Dry Utilities (required to be underground) X Civil Plans and Landscape Plan consistent (utilities also shown on landscape) X Plans scaled and legible OK Incomplete N/A City utilities located on private property? X Proposed structure located over the City utility? X Proposed structure located within City easement? OK Incomplete N/A Other Information X Subdivision file number X Street dedication X Existing and proposed easements with AFN reference X Structures/features to be demolished X Driveway shown with connection to City street Building Permit Completeness Check— Engineering Division Page I of 2 RECEIVED ENGINEERING DIVISION Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES X Driveway slope less than 14% X Frontage improvements X Road widening along with street cross section X Storm system(s) shown (rim, i.e's, pipe material) X Sewer system shown (cleanouts — rim & Le's, pipe material) X Water system shown (water meter & pipe — size & material) ADDITIONAL COMMENTS: 1. Clearly show all on -site improvements (house, driveways, patios, walkways, etc.), property lines, Olympic View Dr, utilities, and the location of the retaining walls on the site plan. 2. Show existing side sewer and water service line on the plans. 3. If there is an on -site storm system, please show on the plans. 4. Show all nearby City easements on the site plan if there are any on the subject property. 5. To where will the retaining wall be draining? a. If proposing to tie into an existing storm pipe that discharges to Puget Sound, the applicant will need to obtain BNSF approval for this connection prior to approval from the City. 6. Show the proposed staging and equipment locations for this project. How will vehicles, drill rigs, materials, etc. be brought down to the work area? Show on the site plan. The comments provided herein do not constitute a comalete elan review and have been rovided as minimum requirements only. Building Permit Completeness Check — Engineering Division Page 2 of 2 RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT APPENDIX D Report Limitations and Guidelines for Use RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT REPORT LIMITATIONS AND GUIDELINES FOR USE Geoscience is Not Exact The geoscience practices (geotechnical engineering, geology, and environmental science) are far less exact than other engineering and natural science disciplines. It is important to recognize this limitation in evaluating the content of the report. If you are unclear how these "Report Limitations and Guidelines for Use" apply to your project or property, you should contact Aspect Consulting (Aspect). This Report and Project -Specific Factors Aspect's services are designed to meet the specific needs of our clients. Aspect has performed the services in general accordance with our agreement (the Agreement) with the Client (defined under the Limitations section of this project's work product). This report has been prepared for the exclusive use of the Client. This report should not be applied for any purpose or project except the purpose described in the Agreement. Aspect considered many unique, project -specific factors when establishing the Scope of Work for this project and report. You should not rely on this report if it was: • Not prepared for you; • Not prepared for the specific purpose identified in the Agreement; • Not prepared for the specific subject property assessed; or • Completed before important changes occurred concerning the subject property, project, or governmental regulatory actions. If changes are made to the project or subject property after the date of this report, Aspect should be retained to assess the impact of the changes with respect to the conclusions contained in the report. Reliance Conditions for Third Parties This report was prepared for the exclusive use of the Client. No other parry may rely on the product of our services unless we agree in advance to such reliance in writing. This is to provide our firm with reasonable protection against liability claims by third parties with whom there would otherwise be no contractual limitations. Within the limitations of scope, schedule, and budget, our services have been executed in accordance with our Agreement with the Client and recognized geoscience practices in the same locality and involving similar conditions at the time this report was prepared. Property Conditions Change Over Time This report is based on conditions that existed at the time the study was performed. The findings and conclusions of this report may be affected by the passage of time, by events such as a change in property use or occupancy, or by natural events, such as floods, earthquakes, slope instability, or groundwater fluctuations. If any of the described events may have occurred following the issuance of the report, you should contact Aspect so that we may evaluate whether changed conditions affect the continued reliability or applicability of our conclusions and recommendations. RECEIVED Feb 06 2024 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT ASPECT CONSULTING Geotechnical, Geologic, and Environmental Reports Are Not Interchangeable The equipment, techniques, and personnel used to perform a geotechnical or geologic study differ significantly from those used to perform an environmental study and vice versa. For that reason, a geotechnical engineering or geologic report does not usually address any environmental findings, conclusions, or recommendations (e.g., about the likelihood of encountering underground storage tanks or regulated contaminants). Similarly, environmental reports are not used to address geotechnical or geologic concerns regarding the subject property. We appreciate the opportunity to perform these services. If you have any questions, please contact the Aspect Project Manager for this project.