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HomeMy WebLinkAboutGeotechnical ReportSouth Sound Geotechnical Consulting P.O. Box 39500, Lakewood, WA 98496 (253) 973-0515 September 8, 2022 Mr. Richard Ramage c/o Hayne Architects P.O. Box 39 Malibu, CA 90265 Subject: Geotechnical Assessment – Landslide Hazard 750 McMinn Road Development Port Townsend, Washington SSGC Project No. 20068 Mr. Ramage, South Sound Geotechnical Consulting (SSGC) has prepared this landslide hazard assessment for the above referenced parcel in Port Townsend, Washington. Our scope of services included a site visit, review of available geologic, soil, topographic, and geologic hazard maps, and preparation of this letter. PROJECT INFORMATION The property is a long and narrow lot with the long axis oriented in a generally north-south direction. The McMinn Road easement bisects the property with the proposed residence on the north side of the lot. The northern boundary of the property is along the shore of the Strait of Juan De Fuca. It is characterized with a bluff along the shoreline having a height of approximately 100 (+/-) feet per Google satellite imagery. The remainder of the property is generally level with about 10 (+/-) feet of elevation change. Vegetation consists of generally mature forest growth (conifer trees) north of McMinn Road. DOCUMENT REVIEW The following documents were reviewed as part of our critical area assessment of the bluff on the north boundary of the property: ◼ U.S. Department of Agriculture Soil Conservation Service, Soil Survey of Jefferson County Area, Washington. ◼ Jefferson County Municipal Code (JCMC). ◼ Washington State DNR Geologic Information Portal Web Site. ◼ Washington State DNR “Geologic Map of the Port Townsend South and Part of the Port Townsend North 7.5-minute Quadrangle, Jefferson County, Washington”, dated 2005. ◼ Washington State Coastal Atlas Maps. ◼ Google Maps Geologic Assessment – Landslide Hazard SSGC 750 McMinn Road Port Townsend, Washington SSGC Project No. 20068 September 8, 2022 2 Document Summary Per Chapter 18.22 of the JCMC, the bluff along the north property boundary is in a landslide hazard area. The bluff is near vertical and has relief of around 100 feet. The Coastal Atlas map depicts the area within approximately 150 (+/-) feet of the bluff as unstable, with the remainder of the site as stable. The Washington DNR portal site and geologic map of the area does show the bluff throughout the area has experienced localized slides. SLOPE CONDITIONS SSGC completed a reconnaissance of the bluff on August 10, 2020 as part of our geotechnical evaluation of the property. Our observations include: ▪ The bluff consists of exposed glacially consolidated soil with exposed soil and some brush and tree growth. Mature conifer trees at the top of the bluff exhibited generally straight trunks. Evidence of recent slides on the bluff across the property boundaries was not observed. ▪ Evidence of existing slope movement (such as tension cracks, down-dropped blocks etc.) was not observed on the site above the bluff at the time of our visit. ▪ Seepage or surface water was not observed on the bluff at the time of our site visit. GEOLOGIC HAZARD AREAS DISCUSSION Chapter 18.22 of the JCMC addresses critical areas and hazard protection standards. Based upon our review of the previously referenced documents and our field observations, we offer the following statements regarding the landslide hazard areas as described in the JCMC. Soils on the northwest-facing bluff generally consist of dense glacially consolidated deposits. Evidence of recent landslide activity (tension cracks, down-dropped blocks, etc.) was not observed on the bluff at the time of our site visit. Currently, the planned residence will be at least 75 feet away from the top of the bluff. This setback is considered suitable based on observed and mapped conditions of the bluff. It is our opinion the development can be constructed without adversely affecting the stability of the bluff. Based on provided information, no planned construction activities will occur within 75 feet of the bluff. We recommend roof stormwater trenches for the proposed residence are located to the south of the building (away from the bluff). Concentrated runoff should not be allowed to flow onto the bluff. June 30, 2023 Richard Ramage 7051 Lincoln Parkway SW #E Seattle, Washington 98136 Updated Geotechnical Engineering Report Proposed Single-Family Residence 750 McMinn Road Jefferson Washington PN: 002014003 Doc ID: Ramage.McMinnRoad.RG INTRODUCTION This Updated Geotechnical Engineering Report summarizes our site observations, subsurface explorations, slope stability analysis, assessment of potential geologically hazardous areas at or near the site and provides geotechnical recommendations for a proposed single-family residence to be constructed at the site. The residence will be located at 750 McMinn Road in the Port Townsend area of Jefferson County, Washington. The general location of the site is shown on the attached Site Location Map, Figure 1. South Sound Geotechnical Consulting (SSGC) completed a Geotechnical Engineering Report for this project dated September 8, 2020. This Geotechnical Engineering Report addresses comments from Jefferson County (the County), as the County requested justification of a 75-foot setback from the top of a high-bank shoreline bluff previously recommended in the SSGC report. Our understanding of the project is based on our conversations and email correspondences with members of your design team including Andrew Stephenson, Vader Engineering, and Holli Lynn Jackowski, Hayne Architects; our review of the SSGC report for this project dated September 8, 2020; our review of the Preliminary Grading and Storm Drainage Plan dated May 24, 2023 and the Preliminary Site Plan dated March 14, 2023; our review of the publicly available geologic literature for the project area; our June 19, 2023 site visit and subsurface explorations; our understanding of the Jefferson County Unified Development Code for Critical Areas, and our experience in Jefferson County. The site is currently undeveloped. As shown on the Site & Exploration Plan, Figure 2, a 3,324 square foot single-family residence is proposed in the upper, southeast corner of the parcel with onsite septic and water well, 700 square-foot garage, driveway, and other associated residential utilities. As recommended in the SSGC geotechnical report for this project, the proposed residence and garage will be founded on conventional spread footings. SSGC recommended that the residence be setback 75 feet from the top of the bluff, but there was no stability analysis or deep subsurface explorations to justify the setback. The County comment requested an updated report be prepared supporting the proposed setback. SCOPE Our scope of services was to evaluate the site conditions as a basis for assessing the recommended 75-foot setback distance from the top of the site’s high-bank shoreline bluff Ramage.McMinnRoad.RG June 30, 2023 page | 2 recommended in the SSGC geotechnical engineering report for this project. Specifically, the scope of services included the following: 1. Reviewing the available geologic, hydrogeologic, and geotechnical data for the site area; 2. Exploring surface conditions by reconnoitering the site and drilling two borings to depths of 21.5 feet and 60.8 feet below the existing grade; 3. Describing surface and subsurface conditions, including soil type and depth to groundwater; 4. Providing seismic design parameters, including 2018 IBC site class; 5. Performing a slope stability analysis using RocScience software SLIDE2 to verify the recommended setback distance of 75-feet from the high-bank shoreline bluff is sufficient for both static and pseudo-static (seismic) conditions; 6. Updating the assessment geologic hazards at the site in accordance with the Jefferson County Unified Development Title 18 Chapter 18.22 Critical Areas for Article V. Geologically Hazardous Areas, including an estimated annual bluff erosion rate; 7. Updating appropriate sections of the 2020 report by South Sound Geotechnical to address current site conditions and the current plans, including the seismic consideration section to the 2018 International Building Code (IBC); 8. Reviewing and providing our professional opinion on the provided stormwater drainage and septic plan; 9. Preparing this Geotechnical Engineering Report summarizing our site observations and conclusions, and our geotechnical recommendations and design criteria, along with the supporting data. The above scope of work was completed in accordance with our Proposal for Services dated June 7, 2023. We received written authorization for our services on June 12, 2023. SITE CONDITIONS Surface Conditions The project site consists of a single tax parcel listed at 750 McMinn Road in the Port Townsend area of Jefferson County, Washington. The site is in an area of existing large-lot, high-bank shoreline residential development and is situated along the top of the north facing high-bank shoreline bluff on the south side of the Strait of Juan De Fuca. As shown on the online tax parcel viewer for Jefferson County, the irregularly shaped parcel measures approximately 85 to 285 feet wide (north to south) by approximately 315 to 390 feet long (east to west) and encompasses approximately 1.46 acres as shown on Figure 3. The site is bounded by the shoreline of the Strait of Juan De Fuca to the north, an undeveloped parcel to the south, and by large lot residential development to the east and west. The description of the site topography is based on the 2-foot topographic contours shown on the Preliminary Grading and Storm Drainage Plan (Vader Engineering, 2023) and our site observations on June 19, 2023. The high bank bluff slopes up from the shoreline from northwest to southeast at about 130 percent with a vertical relief of 120 feet. According to the tax parcel viewer for Jefferson County, the east and west property boundaries extend across the mid slope of the shoreline bluff. From the top of the bluff, the site grades slope slightly up to the southeast and south at 2 to 14 percent to the south and east parcel boundaries with a total vertical relief of about 7 feet. The topographic relief across the site is on the order of about 80 feet. The site and shoreline topography Ramage.McMinnRoad.RG June 30, 2023 page | 3 are shown on an excerpt of the Preliminary Grading and Storm Drainage Plan (Vader Engineering, 2023) included as part of Figure 2. The general topography of the surrounding area is shown on the Site Vicinity Map, Figure 3 is based on 5-foot topographic contours from Jefferson County GIS. Vegetation across the site generally consists of Douglas Fir and ferns. No seeps, springs, or standing water was observed at the time of our site reconnaissance. No signs of active erosion or deep-seated landslide activity were observed at the site during our site reconnaissance on June 19, 2023, but our access was limited to the top of the high-bank shoreline bluff. We anticipate, based on our experience with similar shoreline bluffs, that active erosion is occurring on the face and at the toe of the bluff. Site Soils The USDA Natural Resources Conservation Survey (NRCS) Web Soil Survey mapping for Jefferson County (WA631) has the site soils as Clallam gravelly sandy loam (CmC) and coastal beaches (Co). An excerpt of the NRCS mapping for Jefferson County that covers the site and surrounding area is attached as Figure 4. • Clallam gravelly sandy loam (CmC): Mapped across most of the site, this soil is derived from basal till, forms on slopes of 0 to 15 percent, is considered a “moderate” erosion hazard when exposed, and is included in hydrologic soils group D. • Coastal Beaches (Co): Mapped as the soil on the northwest boundary of the parcel, this soil is derived from colluvium, forms on slopes of 1 to 5 percent, is “not rated” as an erosion hazard and is not included in a hydrologic soils group. Site Geology According to the Geologic Map of the Port Townsend South and Part of the Port Townsend North 7.5-minute Quadrangle, Jefferson, Washington by Henry W. Schassse and Stephen I. Slaughter (2005) the geology of the site and shoreline bluff is glacial till (Qgt), ablation till (Qgta), and glacial and nonglacial deposits, undivided (Qguc). The glacial and ablation till were deposited during the Vashon Stade of the Fraser Glaciation, some 12,000 to 15,000 years ago. The glacial and nonglacial deposits, undivided include geologic units from the Fraser Glaciation and from pre–Fraser non-glacial and glacial periods. A post-Fraser Glaciation landslide deposit (Qls) is mapped by the referenced geologic map on the face of the shoreline bluff northeast of the site. A digitized version of the above referenced geologic map completed by the Washington Geological Survey is attached as Figure 5. • Ablation till (Qgta): Mapped under the upper, flatter, south and southeast portions of the site, ablation till typically consists of a heterogeneous mixture of clay, silt, sand, and gravel that was deposited as subglacial and supraglacial melt-out (direct sediment deposition through the melting of stagnant or very slowly moving debris-rich ice) from the continental ice sheet associated with the Vashon Stade of the Fraser Glaciation. The ablation till is typically encountered in a loose condition, is considered non-consolidated, and exhibits moderate to low strength and compressibility characteristics when undisturbed. • Glacial till (Qgt): Mapped across the northeast and central portions of the site, glacial till typically consists of a heterogeneous mixture of clay, silt, sand, and gravel that was deposited at the base of the continental ice sheet associated with the Vashon Stade of the Fraser Glaciation. The glacial till was typically overridden by the ice sheet during advancement, and Ramage.McMinnRoad.RG June 30, 2023 page | 4 as such is considered over consolidated, is encountered in a dense to very dense condition, and exhibits high strength and low compressibility characteristics when undisturbed. • Glacial and nonglacial deposits, undivided (Qguc): Mapped across the northwest portion of the site and a portion of the shoreline bluff, the undivided glacial and nonglacial deposits typically consist of clay, silt, sand, gravel, glaciomarine drift and till where exposures are poor, and the deposits cannot be reliably divided into separate geologic units. These deposits were typically overridden by ice sheets during glacial periods, and as such are considered over consolidated, encountered in a dense to very dense condition, and exhibits high strength and low compressibility characteristics when undisturbed. Peat and other organics can be observed in the nonglacial deposits. • Landslide Deposits (Qls): Mapped to the northeast of the parcel on the face of the high-bank shoreline bluff, landslide deposits consist of unsorted gravel, sand, silt, clay, boulders, and organics typically deposited post Fraser Glaciation. These deposits are the result of mass wasting activity other than soil creep typically observed on very steep to over-steepened shoreline buffs, slopes with adverse geologic contacts (permeable soils over low permeable soils), slopes with groundwater seepage, or slopes with any combination of the three. We reviewed the Washington Geological Survey (WGS) protocol landslide mapping and other compiled landslide mapping groups for the site and surrounding area. The landslide mapping from these sources is shown on the Washington State Department of Natural Resources (WA DNR) Geologic Information Portal. The WGS protocol maps landslide landforms and landslide susceptibility using Lidar based on the criteria provided in the Protocol for Landslide Mapping from Lidar Data in Washington State (Slaughter, et al, 2017) and the Protocol for Shallow-Landslide Susceptibility Mapping (Burns and others, 2012). The other compiled landslide mapping is referenced from published geologic maps and reports. Where overlap of sources occurs, the WGS-protocol landslide mapping supersedes the other compiled landslide mapping. The compilation mapping shows landslide deposits, including the one on the referenced geologic map discussed above, extending across the lower northeastern portion of the bluff. An excerpt of the landslide compilation mapping as shown on the WA DNR Geologic Information Portal that covers the site and shoreline bluff is attached as Figure 6. We also reviewed the Washington State Department of Ecology (DOE) Coastal Atlas shoreline mapping for the surrounding area. The slope stability mapping was originally published as a hard copy map in the Coastal Zone Atlas of Washington between 1978 and 1980 and eventually digitized for reference. The digitized coastal atlas slope stability maps the upland portion of the site as “stable”. The high bank shoreline bluff is mapped as “unstable - old slide” which approximately corresponds to the WGS landslide compilation mapping. An excerpt of the Coastal Atlas map for slope stability of the site and surrounding area is included as Figure 7. Oblique shoreline photographs of the northwest shoreline of the Strait of Juan De Fuca from 1990, 2000, and 2016 that includes the site’s high bank shoreline bluff is attached as Figures 8a through 8c. The shoreline photo from 2000 shows a deep-seated landslide just northeast of the site. The dated sequences of images show the bluff is prone to surficial failure and bluff regression. The landslide compilation mapping as referenced above includes this landslide in the dataset. Ramage.McMinnRoad.RG June 30, 2023 page | 5 Subsurface Explorations On June 19, 2023, we visited the site and monitored the drilling of two borings to the depths of approximately 21.5 and 60.8 feet below existing site grades. The locations of the borings were selected by GeoResources personnel based on site access limitations, the proposed layout for the site, location of the recommended setback distance in the SSGC geotechnical engineering report for this project, and consideration for underground utilities. The borings were located by taping and pacing from features shown on publicly available data from Jefferson County GIS. As such, the locations of the explorations should only be considered accurate to the degree implied by our measuring methods. Table 1 summarizes the functional location, approximate elevation, and approximate termination elevation of the boring. TABLE 1: APPROXIMATE LOCATIONS AND DEPTHS OF EXPLORATIONS Boring Number Functional Location Surface Elevation1 (feet) Termination Depth (feet) Termination Elevation1 (feet) B-1 B-2 45 feet from top of high-bank shoreline bluff 110 feet southeast of boring B-1 132 136 60.8 21.5 71.2 114.5 Notes: 1 Preliminary Grading and Storm Drainage Plan for the Ramage residence by Vador Engineering, May 24, 2023. The boring rig was operated by a licensed drilling contractor working for GeoResources. Soil samples were obtained at 2½ and 5-foot depth intervals in accordance with Standard Penetration Test (SPT) as per the test method outlined by ASTM D1586. The SPT method consists of driving a standard 2-inch-diameter split-spoon sampler 18 inches into the soil with a 140-pound hammer. The number of blows required to drive the sampler through each 6-inch interval is counted, and the total number of blows during the final 12 inches of sampling is recorded as the Standard Penetration Resistance, or “SPT blow count”. If a total of 50 blows are recorded within any 6-inch interval (refusal), the driving is stopped, and the blow counts are recorded as 50 blows for the distance driven. The resulting SPT values indicate the relative density of granular soils and the relative consistency of cohesive soils. Each boring exploration was backfilled by the drilling subcontractor with bentonite chips in accordance with Washington State Department of Ecology requirements. An experienced and licensed geologist from our office continuously monitored the boring, maintained logs of the subsurface conditions encountered, obtained representative soil samples, and observed pertinent site features. Representative soil samples obtained from the borings were placed in sealed plastic bags and taken to our laboratory for further examination and testing as deemed necessary. The soils encountered were visually classified in accordance with the Unified Soil Classification System (USCS), which is included in Appendix A as Figure A-1. The descriptive logs of the borings are included as Figures A-2 and A-3. The location of each boring is shown on the attached Figure 2. Subsurface Conditions Our borings encountered subsurface conditions that were consistent with the soils logged in the test pit explorations from the SSGC geotechnical engineering report and generally confirmed the broad geologic mapping of undivided glacial and nonglacial deposits. Based on drilling conditions, Ramage.McMinnRoad.RG June 30, 2023 page | 6 density, and grain size, we split the Qguc soils into several distinct subunits. Each soil layer/type encountered at each boring location with the interpreted geologic unit for each soil layer is described below, while the thickness, depth, and elevation of each unit is described below in Table 2. TABLE 2: APPROXIMATE THICKNESS, DEPTHS, AND ELEVATION OF ENCOUNTERED SOIL TYPES Boring Number Thickness in feet of: Depth to Glacial and Non-Glacial Deposits (feet) Elevation1 of Glacial and Non-Glacial Deposits (feet) Topsoil Advance Glaciolacustrine Advance Outwash Glacial Till B-1 B-2 1 1 0 12.5 27 >9 40 NE 55 NE 77 NE Notes: 1 Preliminary Grading and Storm Drainage Plan for the Ramage residence by Vador Engineering, May 24, 2023. • Topsoil: At each boring location we observed about 1 foot of dark brown topsoil as the upper most soil layer, confirming the topsoil thickness noted in the test pit logs for the SSGC geotechnical engineering report. • Vashon Advance Glaciolacustrine Deposits: Underlying the topsoil at boring B-2 we observed about 5 feet of medium dense silty sand to poorly graded very fine sand with some silt mantling 7.5 feet of very stiff to hard grey to dark grey silt with some sand and variable amounts of gravels. We interpreted this soil to be advance glaciolacustrine deposits. Similar soil descriptions were noted in two exploration test pits from the SSGC geotechnical engineering report. • Vashon Advance Outwash: Underlying the topsoil at boring B-1 and the advance glaciolacustrine deposits at boring B-2 was a medium dense to dense brown, grey, to light grey poorly graded fine sand with some to trace silt and some to minor gravels. We interpret these soils to be fluvial advance outwash deposits and this deposit was observed to the full depth explored at boring B-2. Similar soils were described in one exploration test pit and an infiltration test pit from the SSGC geotechnical engineering report. • Glacial Till: Underlying the advance outwash at boring B-1 we observed about 25 feet of dense to very dense grey to dark grey gravelly silty sand in a moist condition. We interpreted this soil layer to be glacial till deposits. • Glacial and nonglacial deposits: Underlying the glacial till deposits at boring B-1 we observed a very dense grey silty sand in a dry to moist condition to the full depth explored. We interpreted this soil layer to be glacial and nonglacial deposits. Laboratory Testing Geotechnical laboratory tests were performed on select samples retrieved from the borings to estimate index engineering properties of the soils encountered. Laboratory testing included visual soil classification per ASTM D2488 and ASTM D2487, moisture content determinations per ASTM D2216, grain size analyses per ASTM D6913, washes per ASTMD1140-17 and Atterberg Limit determinations per ASTM D4318 standard procedures. Test results are included in Appendix B and summarized below in Table 3. Ramage.McMinnRoad.RG June 30, 2023 page | 7 TABLE 3: LABORATORY TEST RESULTS FOR ON-SITE SOILS Sample Soil Type Gravel Content (percent) Sand Content (percent) Silt/Clay Content (percent) Moisture Content (percent) B-1, S-11, 55.0ft SM 0.6 83.9 15.5 2.6 B-2, S-3+4, 5.0ft & 7.5ft CL ND ND 88.0 18.0 Sample Soil Type Liquid Limit (percent) Plastic Limit (percent) Plasticity Index (percent) Moisture Content (percent) B-2, S-3+4, 5.0ft & 7.5ft CL 44 21 23 18.0 Notes: ND = Not Determined, wash per ASTM D1170 Groundwater Conditions No groundwater seepage was observed during the drilling of each boring exploration. The drilling occurred during the dry season months (typically May to September), when groundwater levels are typically at their lowest. Groundwater seepage was noted in one test pit exploration from the SSGC geotechnical engineering report, at 9.5 feet below the existing grade. The test pit with the groundwater seepage was located about 450 feet southwest from boring B-2 and was also excavated during the dry season months. Based on the observed soil conditions, some areas of the site may be susceptible to perched groundwater during periods of prolonged wet weather. Some areas of the site appear to have a thin soil layer of silty sand or poorly graded sand overlying silt and clay soils at shallow depths, which can create the conditions needed for the development of a perched groundwater table. Silt and clay soils act as a low permeable soil and restrict the vertical movement of stormwater runoff. Perched groundwater tables are typically limited in thickness and can vary widely in lateral extent. Relatively rapid fluctuations of groundwater levels should be expected with seasonality and precipitation events. We reviewed two water well reports for private water wells installed at 620 McMinn Road and 690 McMinn Road. The water well reports were obtained from the Washington State Department of Ecology online well search tool. The water wells at 620 and 690 McMinn Road are located within 500 feet of the site and are approximately labeled on the attached Figure 3. The static groundwater levels for the wells were recorded at 142 feet (approximate elevation of -7 feet below sea level) and 131 feet (approximate elevation of 7 feet above sea level) below the top of the well, respectively. The surface elevations for each well were referenced from the Digital Terrain Model 137 from the Olympics South OSPW 2019 Lidar data. Each well log is included in the attached Appendix C. ENGINEERING CONCLUSIONS AND RECOMMENDATIONS Based on our site observations, data review, subsurface explorations, and engineering analysis, it is our opinion from a geotechnical standpoint that the construction of the proposed single-family residence is feasible provided the recommendations in this report are incorporated into the final design. Based on our site reconnaissance and geological assessment, the high bank Ramage.McMinnRoad.RG June 30, 2023 page | 8 shoreline bluff at the site meets the criteria for a landslide hazard area as defined by JCC 18.10.120. Pertinent conclusions and geotechnical recommendations regarding the design and construction of the proposed residence are presented below. Our services were provided to assist in the design of a single-family residence in proximity to the top of a high bank shoreline bluff. Our recommendations are intended to improve the overall stability of the site and to reduce the potential for future property damage related to earth movements, drainage, or erosion. However, all development on slopes involves risk, only part of which can be mitigated through qualified engineering and construction practices. Seismic Design The site is in the Puget Sound region of western Washington, which is seismically active. Seismicity in this region is attributed primarily to the interaction between the Pacific, Juan de Fuca, and North American plates. The Juan de Fuca plate is subducting beneath the North American plate at the Cascadia Subduction Zone (CSZ), creating the conditions for both intercrustal (between plates) and intracrustal (within a plate) earthquakes. In the following sections we discuss the design criteria and potential hazards associated with regional seismicity. Seismic Site Class Based on relative densities of soils observed in our boring explorations, we interpret the structural site conditions to correspond to a seismic Site Class “C” in accordance with the 2018 IBC documents and American Society of Civil Engineers (ASCE) standard 7-16. Single-family residences are typically classified as seismic rick category II. Design parameters The U.S. Geological Survey (USGS) completed probabilistic seismic hazard analyses (PSHA) for the entire country in November 1996, which were updated and republished in 2002 and 2008. We used the ATC Hazard by Location website to estimate seismic design parameters at the site. Table 4 summarizes the recommended design parameters. TABLE 4: 2018 IBC PARAMETERS FOR DESIGN OF SEISMIC STRUCTURES Spectral Response Acceleration (SRA) and Site Coefficients Short Period Risk Category II Mapped SRA Site Coefficients (Site Class C) Maximum Considered Earthquake SRA Design SRA Ss = 1.330g Fa = 1.200 SMS = 1.596g SDS = 1.064 g Peak Ground Acceleration The mapped peak ground acceleration (PGA) for this site is 0.569g. To account for site class the PGA is multiplied by a site amplification factor (FPGA) of 1.2. The resulting site modified peak ground Ramage.McMinnRoad.RG June 30, 2023 page | 9 acceleration (PGAM) is 0.683g. In general, estimating seismic earth pressures (kh) by the Mononobe- Okabe method is taken as 50 percent of the PGAM, or 0.342g. Seismic Hazards Earthquake-induced geologic hazards may include liquefaction, lateral spreading, slope instability, and ground surface fault rupture. Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in pore water pressure in soils. The increase in pore water pressure is induced by seismic vibrations. Liquefaction primarily affects geologically recent deposits of loose, uniformly graded, fine-grained sands and granular silts that are below the groundwater table. The soils observed in our boring explorations are glacially consolidated soils, therefore it is our opinion that the risk to the development from liquefaction is low to negligible. This is consistent with the Liquefaction susceptibility and site class maps of Washington State, by county: Washington Division of Geology and Earth Resources Open File Report 2004-20 by Palmer et. al. (2007) includes the site in the “very low” category for liquefaction susceptibility. An excerpt of the susceptibility mapping referenced above is attached as Figure 9. The Department of Natural Resources Geologic Hazards Map (Geologic Information Portal) infers an unnamed fault about 1,180 feet southwest of the site. The fault zone ends at the shoreline of the Strait of Juan De Fuca and continues northwest across the Strait of Juan De Fuca for about 4 miles. Tacoma fault zone to be more than 3 miles to the north and east of the site. An excerpt of the WA DNR fault hazard mapping showing the unnamed fault in proximity to the site is attached as Figure 10. No evidence of ground fault rupture was observed in the deeper boring exploration or out site reconnaissance. But it is possible evidence of a fault rupture is located beneath the final depth of our deepest boring exploration at the site. In our opinion, the proposed structure should have no greater risk of ground fault rupture than other structures located in the area. Slope Stability Analysis We analyzed the global slope stability of the site and high-bank shoreline bluff for profile A- A’. Both static and pseudo-static conditions were modeled for the slope stability analysis. The location of profile A-A’ was selected based on the location of our borings and proposed single-family residence to the shoreline bluff. The cross-section line A-A’ is labeled on the attached Figure 2. Methodology of Slope Stability Analysis The analysis was completed using SLIDE2 by RocScience software. SLIDE2 uses several methods to estimate the factor of safety (FS) of the stability of a slope by analyzing the shear and normal forces acting on a series of vertical “slices” that comprise a failure surface. Each vertical slice is treated as a rigid body; therefore, the forces and/or moments acting on each slice are assumed to satisfy static equilibrium (i.e., a limit equilibrium analysis). The FS is defined as the ratio of the forces available to resist movement to the forces of the driving mass. An FS of 1.0 means that the driving and resisting forces are equal; an FS less than 1.0 indicates that the driving forces are greater than the resisting forces (indicating failure). We used the Generalized Limit Equilibrium method using the Morgenstern-Price analysis, which satisfies both moment and force equilibrium, to search for the location of the most critical failure surfaces and their corresponding FS. The Morgenstern-Price methodology satisfies both moment and force equilibrium. The most critical surfaces are those with the lowest FS for a given loading condition and therefore are the most likely to move. Ramage.McMinnRoad.RG June 30, 2023 page | 10 Surface and Subsurface Profile for Profile A-A’ The surface profile for profile A-A’ was drawn using the 2-foot elevation contours shown on the Preliminary Grading and Storm Drainage Plan for the Ramage residence by Vader Engineering dated May 24, 2023. The subsurface geology of profile A-A’ was approximated by referencing the soils observed in our boring explorations, the test pit logs from the SSGC geotechnical engineering report, the water well reports within 500 feet of the site, and the Geologic Map of the Port Townsend South and Part of the Port Townsend North 7.5-minute Quadrangle, Jefferson, Washington by Henry W. Schassse and Stephen I. Slaughter (2005). The groundwater table was determined from the static groundwater elevations recorded in the water well reports from 620 and 690 McMinn Road. Material Properties for Stability Analysis For estimating the material properties for the slope stability analysis, we reviewed the Koloski, Schwarz, and Tubbs (1989) Geotechnical Properties of Geologic Materials, Engineering Geology in Washington, Washington Division of Geology and Earth Resources Bulletin 78 Volume I and the Edwin L. Harp, John A. Michael, and William T. Laprade (2006) Shallow-Landslide Hazard Map of Seattle, Washington, U.S. Geological Survey Open-File Report 2006-1139. We also reviewed the engineering properties for the various soils encountered on site per Chapter 5 of the 2019 Washington State Department of Transportation (WSDOT) Geotechnical Design Manual (M46-03.12). Table 5 summarizes the values published in the two referenced reports. Ramage.McMinnRoad.RG June 30, 2023 page | 11 TABLE 5: SOIL PROPERTIES FOR VARIOUS NATIVE SOIL TYPES ENCOUNTERED IN THE PUGET SOUND Deposit Source Dry Unit Weight (pcf) Friction Angle (degrees) Cohesion (psf) Glacial Till (ML, SM) Geotechnical Properties of Geologic Materials 120-140 35-45 1,000-4,000 Outwash (GW, GP, SW, SP, SM) 115-130 30-40 0-1,000 Beach deposits Shallow-Landslide Hazard Map of Seattle, Washington NA 34 0 Vashon recessional lacustrine deposits 24 ~400 Vashon till 36 ~2,000 Vashon advance outwash 34 ~250 Pre-Fraser fine grained deposits 26 ~600 Glacial Till WSDOT Geotechnical Design Manual (M46-03.12) 130-140 40 - 45 1,000-4,000 Outwash NA 40 - 45 01 Notes: 1 = GDM does not provide a range for outwash, but it states “near zero cohesion for clean deposits” Table 6 summarizes the estimated soil properties used in our slope stability analysis. A seismic load of 0.17g for till and firm glaciated soils, using the minimum general values of horizontal peak ground accelerations as defined in JCC 18.22.945.2.c and the blow counts observed during our boring explorations. TABLE 6: ASSIGNED SOIL STRENGTH PROPERTIES FOR SLOPE STABILITY ANALYSIS Deposit Unit Weight (pcf) Saturated Unit Weight (pcf) Friction Angle (degrees) Cohesion (psf) Beach Deposits 120 - 34 0 Advance Glaciolacustrine 110 - 24 400 Advance Outwash 125 - 40 100 Glacial Till 130 - 45 1500 Glacial & Nonglacial Deposits 110 120 36 600 Ramage.McMinnRoad.RG June 30, 2023 page | 12 Results of Stability Analysis Table 7 summarizes the factors of safety along the most critical slip surface identified from the stability analysis. The results of our slope stability analysis for cross section A-A’ and B-B’ are included in Appendix D. TABLE 7: GLOBAL STABILITY ANALYSES RESULTS Section Condition Loading Condition Lowest Factor of Safety Factor of Safety 75 feet bluff A-A’ Existing Static a = 0.17g for till, firm glaciated soils 1.2 1.0 1.5 1.1 Proposed Static a = 0.17g for till, firm glaciated soils 1.2 1.0 1.5 1.1 GEOLOGICALLY HAZARDOUS AREAS We completed an assessment of the geologically hazardous areas for the upland portion of the site and high-bank shoreline bluff. Jefferson County Title 18.22.510 defines geologically hazardous areas based on the following classification/designation: Erosion Hazard Areas (as defined in JCC 18.10.050) The site is located at the top of an over steepened high-bank shoreline bluff, likely created from erosion associated with wave, tidal, and wind energy. Accordingly, the site does meet the definition of an erosion hazard. The high bank shoreline bluff is a coastal erosion-prone area and should be considered an erosion hazard area. Erosion hazards can be mitigated by applying Best Management Practices outlined in the 2019 SWMMWW. We recommend that the single-family residence use conventional flow-control best management practices (BMPs) to address runoff from the residence. The location of the single- family residence is outside the conservative 120-year regression rate for the high-bank shoreline bluff, thus maintaining at least a 120-year useful life of the structure from coastal erosion hazards. The estimated regression limit for 120 years using a conservative yearly regression rate of 6-inches per year is labeled on the attached Figure 11. Landslide Hazard Areas (as defined in JCC 18.10.120) The high bank shoreline bluff at the site meets five indicators of a landslide hazard area as defined by Jefferson County Title 18.10.120(A) (indicators i, ii, iii, iv, and ix). Our slope stability analysis of the high bank shoreline bluff for existing configuration had factors of safety below 1.5 and 1.1 respectively for the static and dynamic conditions. The high bank shoreline bluff is a landslide hazard area. The landslide hazard area is labeled on the attached Figure 11. Ramage.McMinnRoad.RG June 30, 2023 page | 13 Buffer and Setback from Landslide Hazard Area Based on the result of our slope stability analysis, we support a 60-foot vegetated buffer with an additional 15-foot building setback from the edge of the vegetated buffer. Grading, decks, and septic systems are allowed within the 15-foot building setback. The buffer and setback are labeled on the attached Figure 2 and 11. Stormwater Management Jefferson County has adopted the 2019 Washington State Department of Ecology Stormwater Management Manual for Western Washington for use in stormwater management and design. Per the provided preliminary storm drainage plans for the single-family residence, an infiltration trench measuring 4 feet (width) x 4 feet (depth) x 40 feet (length) is proposed within the 15-foot building setback and is located approximately 50 feet from the top of the shoreline high bank bluff. We assess the high bank shoreline bluff as a landslide hazard area and a 200-foot setback from a landslide hazard area is required unless evaluated by a geotechnical professional. The proposed infiltration trench is located within the proposed setback associated with the recommended buffer. The proximity of the trench to the top of the slope was not discussed in the original SSGC (Verify) report. Converting the infiltration trench to a dispersion would limit the amount of point-sourced infiltration but the dispersion trench would not have the prerequisite 100- foot vegetated flow path to the slope. However, flowing through the vegetated buffer would provide protection from erosion and allow for runoff to be taken up by the root mass. Alternatively, we would recommend an HDP tightline down the bluff conveying runoff to discharge on the beach at the toe of the bluff. We understand the County has pushed back on the use of tightline conveyance systems to shorelines because of the need for special shoreline permits. Our experience is that such tightline conveyance systems are permitted through a Shoreline Exemption permit because they are an auxiliary appurtenant structure, but that a Hydraulic Activity Permit (HPA) would be required by the Department of Fish and Wildlife. Additionally, installation of the spreader pipe at the toe of the bluff may also be challenging given the difficult access to the beach. “ LIMITATIONS We have prepared this report for use by Mr. Richard Ramage and other members of the design team, for use in the design of a portion of this project. The data used in preparing this report and this report should be provided to prospective contractors for their bidding or estimating purposes only. Our report, conclusions and interpretations are based on our subsurface explorations, data from others and limited site reconnaissance, and should not be construed as a warranty of the subsurface conditions. Variations in subsurface conditions are possible between the explorations and may also occur with time. A contingency for unanticipated conditions should be included in the budget and schedule. Sufficient monitoring, testing and consultation should be provided by our firm during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether earthwork and foundation installation activities comply with contract plans and specifications. Ramage.McMinnRoad.RG June 30, 2023 page | 14 If there are any changes in the loads, grades, locations, configurations or type of facilities to be constructed, the conclusions and recommendations presented in this report may not be fully applicable. If such changes are made, we should be given the opportunity to review our recommendations and provide written modifications or verifications, as appropriate.    Ramage.McMinnRoad.RG June 30, 2023 page I 15 We appreciate the opportunity to be of service to you on this project. If you have any questions or comments, please do not hesitate to call at your earliest convenience. Respectfully submitted, GeoResources, LLC ErikJ. Fina, LG Senior Staff Geologist Keith S. Schembs, LEG Principal EJF:KSS:EWH/ejf DoclD: Ramage.McMinnRoad.RG Attachments: Figure 1: Site Location Map Figure 2: Site & Exploration Plan Figure 3: Site Vicinity Map Figure 4: NRCS Soils Map Figure 5: Geologic Map Figure 6: WGS Landslide Compilation Mapping Figure 7: WA DOE Coastal Atlas Figure 8a-8c: -Shoreline Oblique Photos Figure 9: Liquefaction Susceptibility Map Figure 10: Fault Hazard Mapping Figure 11: Geologically Hazardous Areas Appendix A: Subsurface Explorations Appendix B: Laboratory Test Results Appendix C: Water Well Reports Appendix D: Slope Stability Results Eric W. Heller, PE Senior Geotechnical Engineer GEORESOURCES earth science & geotechnical engineering Approximate Site Location Figure created from Jefferson County Public Land Records GIS website (https://gisweb.jeffcowa.us/LandRecords/) Not to Scale Site Location Map Proposed Single-Family Residence 750 McMinn Road Port Townsend, Washington PN: 002014003 Doc ID: Ramage.McMinnRoad.F Jun 2023 Figure 1 A ASetbackBuffer A A' B-2 B-1 Doc ID: Ramage.McMinnRoad.F July 2023 Preliminary Site Plan prepared by Vader Engineering, dated March 14, 2023.Coordinate System: NAD 1983 HARN StatePlane Washington North FIPS 4601 FeetProjection: Lambert Conformal ConicDatum: North American 1983 HARN 0 25 50 75 10012.5 Feet Proposed Single-Family Residence750 McMinn RoadJefferson County, WashingtonPN: 002014003 1 inch = 50 feet Figure 2 Site & Exploration PlanLegend A Number and approximate location of boring Cross Section Setback Buffer Approximate Site Location Figure created from Jefferson County Public Land Records GIS website (https://gisweb.jeffcowa.us/LandRecords/) Not to Scale Site Vicinity Map Proposed Single-Family Residence 750 McMinn Road Port Townsend, Washington PN: 002014003 Doc ID: Ramage.McMinnRoad.F Jun 2023 Figure 3 620 McMinn Rd 690 McMinn Rd 2014003 Source: Esri, Maxar, Earthstar Geographics, IGN, and the GIS User Community Approximate Site Location Figure created from Web Soil Survey (http://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx) Soil Type Soil Name Parent Material Slopes Erosion Hazard Hydrologic Soils Group CmC Clallam gravelly sandy loam Basal till 0 to 15 Moderate D Co Coastal beaches Colluvium 1 to 5 Not rated -- HuC Hoypus gravelly loamy sand Glacial outwash 0 to 15 Moderate A Not to Scale NRCS Soils Map Proposed Single-Family Residence 750 McMinn Road Port Townsend, Washington PN: 002014003 Doc ID: Ramage.McMinnRoad.F Jun 2023 Figure 4 CmC HuC Co 2014003 Source: Esri, Maxar, Earthstar Geographics, IGN, and the GIS User Community Approximate Site Location A Washington Geological Survey digitized version of the Geologic Map of the Port Townsend South and Part of the Port Townsend North 7.5-Minute Quadrangles, Jefferson County, Washington by Henry W. Schasse and Stephen I. Slaughter (2005). Symbol Geologic Unit Qb Beach deposits Qls Landslide deposits Qgoi Ice-contact stratified drift Qgt Lodgment till Qgta Ablation till Qguc Glacial and nonglacial deposits, undivided Not to Scale Geologic Map Proposed Single-Family Residence 750 McMinn Road Port Townsend, Washington PN: 002014003 Doc ID: Ramage.McMinnRoad.F Jun 2023 Figure 5 wtr Qgt(a) Qgt Qgo(i)Qguc Qguc QlsQb Qls 2014003 Approximate Site Location An excerpt from the WGS database set for Landslide Compilation, overlayed on World Imagery and a DTM from the Olympics South ospw 2019 Lidar Not to Scale WGS Landslide Compilation Mapping Proposed Single-Family Residence 750 McMinn Road Port Townsend, Washington PN: 002014003 Doc ID: Ramage.McMinnRoad.F Jun 2023 Figure 6 Qls Qls 2014003 Source: Esri, Maxar, Earthstar Geographics, IGN, and the GIS User Community 1:24,000-scale Landslides from Geologic Mapping Approximate Site Location An excerpt from the WA DOE Coastal Zone Atlas Map (https://apps.ecology.wa.gov/coavstalatlas/tools/Map.aspx) Not to Scale WA DOE Coastal Atlas Proposed Single-Family Residence 750 McMinn Road Port Townsend, Washington PN: 002014003 Doc ID: Ramage.McMinnRoad.F Jun 2023 Figure 7 Stable slope Unstable-old slideFBDZ LtoR 2014003 Source: Esri, Maxar, Earthstar Geographics, IGN, and the GIS User Community Approximate Site Location Shoreline oblique photo from 1990 Not to Scale Shoreline Oblique Photos Proposed Single-Family Residence 750 McMinn Road Port Townsend, Washington PN: 002014003 Doc ID: Ramage.McMinnRoad.F Jun 2023 Figure 8a Approximate Site Location Shoreline oblique photo from 2000 Not to Scale Shoreline Oblique Photos Proposed Single-Family Residence 750 McMinn Road Port Townsend, Washington PN: 002014003 Doc ID: Ramage.McMinnRoad.F Jun 2023 Figure 8b Approximate Site Location Shoreline oblique photo from 2016 Not to Scale Shoreline Oblique Photos Proposed Single-Family Residence 750 McMinn Road Port Townsend, Washington PN: 002014003 Doc ID: Ramage.McMinnRoad.F Jun 2023 Figure 8c Approximate Site Location Palmer, Stephen P.; Magsino, Sammantha L.; Bilderback, Eric L.; Poelstra, James L.; Folger, Derek S.; Niggemann, Rebecca A., 2007, Liquefaction susceptibility and site class maps of Washington State, by county: Washington Division of Geology and Earth Resources Open File Report 2004-20, [78 plates, 45 p. text]. http://www.dnr.wa.gov/publications Not to Scale Liquefaction Susceptibility Map Proposed Single-Family Residence 750 McMinn Road Port Townsend, Washington PN: 002014003 Doc ID: Ramage.McMinnRoad.F Jun 2023 Figure 9 Approximate Site Location An excerpt from the Washington State Department of Natural Resources Geologic Information Portal (https://geologyportal.dnr.wa.gov/) Not to Scale Fault Hazard Mapping Proposed Single-Family Residence 750 McMinn Road Port Townsend, Washington PN: 0020140037 Doc ID: Ramage.McMinnRoad.F Jun 2023 Figure 10 2014003 U n n a me d f a u lt (cla s s B ) © OpenStreetMap (and) contributors, CC-BY-SA 1,180 feet SW of Site SetbackBuffer120 Yr Regression LimitFigure 11Doc ID: Ramage.McMinnRoad.F July 2023 Preliminary Site Plan prepared by Vader Engineering, dated March 14, 2023.Coordinate System: NAD 1983 HARN StatePlane Washington North FIPS 4601 FeetProjection: Lambert Conformal ConicDatum: North American 1983 HARN 0 25 50 75 10012.5 Feet Proposed Single-Family Residence750 McMinn RoadJefferson County, WashingtonPN: 002014003 Geologically Hazardous Areas 1 inch = 50 feet Legend Setback Buffer Shoreline Regression Limit Landslide and Erosion Hazard Area Appendix A Subsurface Explorations SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP SYMBOL GROUP NAME COARSE GRAINED SOILS GRAVEL CLEAN GRAVEL GW WELL-GRADED GRAVEL, FINE TO COARSE GRAVEL GP POORLY-GRADED GRAVEL More than 50% Of Coarse Fraction Retained on No. 4 Sieve GRAVEL WITH FINES GM SILTY GRAVEL GC CLAYEY GRAVEL More than 50% Retained on No. 200 Sieve SAND CLEAN SAND SW WELL-GRADED SAND, FINE TO COARSE SAND SP POORLY-GRADED SAND More than 50% Of Coarse Fraction Passes No. 4 Sieve SAND WITH FINES SM SILTY SAND SC CLAYEY SAND FINE GRAINED SOILS SILT AND CLAY INORGANIC ML SILT CL CLAY Liquid Limit Less than 50 ORGANIC OL ORGANIC SILT, ORGANIC CLAY More than 50% Passes No. 200 Sieve SILT AND CLAY INORGANIC MH SILT OF HIGH PLASTICITY, ELASTIC SILT CH CLAY OF HIGH PLASTICITY, FAT CLAY Liquid Limit 50 or more ORGANIC OH ORGANIC CLAY, ORGANIC SILT HIGHLY ORGANIC SOILS PT PEAT NOTES: SOIL MOISTURE MODIFIERS: 1. Field classification is based on visual examination of soil Dry- Absence of moisture, dry to the touch in general accordance with ASTM D2488-90. Moist- Damp, but no visible water 2. Soil classification using laboratory tests is based on ASTM D6913. Wet- Visible free water or saturated, usually soil is obtained from below water table 3. Description of soil density or consistency are based on interpretation of blow count data, visual appearance of soils, and or test data. Unified Soils Classification System Proposed Single-Family Residence 750 McMinn Road Port Townsend, Washington PN: 002014003 Doc ID: Ramage.McMinnRoad.F Jun 2023 Figure A-1 0 5 10 15 20 25 30 130 125 120 115 110 105 100 Blow counts overstated first 6- inches, sampling on gravel or cobble Upper contact of Glacial Till Dark brown topsoil Cuttings visually classifed as silty SAND (SM) with some gravels (Vashon Advance Outwash) Brownish grey poorly graded fine SAND with some gravel and silt (SP-SM) (medium dense, moist) Brownish grey gravelly poorly graded fine SAND with some silt (SP-SM) interbedded with grey silt (medium dense, dry to moist) Light grey poorly graded fine SAND with some gravel and trace silt (SP) (dense, dry to moist) Light grey poorly graded fine to very fine SAND with some silt and trace gravel (SP-SM) (dense, dry to moist) Ligh grey poorly graded SAND with some gravel and silt (dense, dry to moist) Grey gravelly silty SAND (SM) (very dense, dry to moist) (Glacial Till) 7 8 10 9 12 16 9 15 34 43 20 26 12 18 21 21 32 40 72 LOG OF BORING B-1 Proposed Single-Family Residence750 McMinn RoadPort Townsend, Washington 1. Refer to log key for definition of symbols, abbreviations, and codes 2. USCS disination is based on visual manual classification and selected lab testing 3. Groundwater level, if indicated, is for the date shown and may vary 4. NE = Not Encountered 5. ATD = At Time of Drilling Drilling Company:Boretec, Inc.Logged By:EJF Drilling Method:Hollow Stem Auger Drilling Date:06/19/2023 Drilling Rig:EC Track Rig Datum:NAVD88 Sampler Type:Spilt Spoon Elevation:132 feet Hammer Type:Rope Pulled Cathead Termination Depth:60.8 feet Hammer Weight:140lbs Latitude: Notes:Longitude: Topsoil Silty sand Poorly graded sand with silt Poorly graded sand Silty sand and gravel Sheet 1 of JOB:Ramage.McMinnRoad FIG.A-2Depth(feet)Elevation (feet)Exploration notes Soil description SPT BlowcountsSamplerSymbolTest Results 1020304050Penetration - (blows per foot) % Water Content % Fines (<0.075mm)Plastic Limit Liquid Limit Groundwater2 35 40 45 50 55 60 95 90 85 80 75 70 Dark grey gravelly silty SAND (SM) (dense, moist to wet) Groundwater seepage? Dark grey gravelly silty SAND (SM) (very dense, moist) Grey silty SAND (SM) (very dense, moist) (Glacial and Nonglacial Deposits) Grey silty SAND (SM) (very dense, dry to moist) (Termination Depth - 06/19/2023) 19 22 26 18 32 49 50/4" 50/3" 48 50/5" 42 50/4" 81 150 200 120 150 LOG OF BORING B-1 Proposed Single-Family Residence750 McMinn RoadPort Townsend, Washington 1. Refer to log key for definition of symbols, abbreviations, and codes 2. USCS disination is based on visual manual classification and selected lab testing 3. Groundwater level, if indicated, is for the date shown and may vary 4. NE = Not Encountered 5. ATD = At Time of Drilling Drilling Company:Boretec, Inc.Logged By:EJF Drilling Method:Hollow Stem Auger Drilling Date:06/19/2023 Drilling Rig:EC Track Rig Datum:NAVD88 Sampler Type:Spilt Spoon Elevation:132 feet Hammer Type:Rope Pulled Cathead Termination Depth:60.8 feet Hammer Weight:140lbs Latitude: Notes:Longitude: Topsoil Silty sand Poorly graded sand with silt Poorly graded sand Silty sand and gravel Sheet 2 of JOB:Ramage.McMinnRoad FIG.A-2Depth(feet)Elevation (feet)Exploration notes Soil description SPT BlowcountsSamplerSymbolTest Results 1020304050Penetration - (blows per foot) % Water Content % Fines (<0.075mm)Plastic Limit Liquid Limit Groundwater2 0 5 10 15 20 25 30 135 130 125 120 115 110 105 Upper Contact Vashon Advance Outwash Dark brown topsoil Cuttings visually classifed as silty SAND (SM) with some gravels (Vashon Advance Glaciolacustrine) Brownish grey gravelly poorly graded very fine SAND with some silt (SP-SM) (medium dense, moist) Grey CLAY with some silt and trace sand (CL) (hard, dry to moist) LL=44, PL=21, PI=23 (S-2 and S-3 combined) Grey CLAY with some silt and trace sand (CL) (very stiff, dry to moist) Dark grey CLAY with some silt and trace sand (CL) (very stiff, moist) silty sand at tip spilt spoon and in shoe Grey silty SAND with some gravels (SM) (dense, dry to moist) (Vashon Advance Outwash) Brown gravelly poorly graded SAND with trace silt (SP) (very dense, dry to moist) (Termination Depth - 06/19/2023) 7 8 7 7 13 20 8 12 15 43 20 26 16 17 23 15 24 32 88.0 LOG OF BORING B-2 Proposed Single-Family Residence750 McMinn RoadPort Townsend, Washington 1. Refer to log key for definition of symbols, abbreviations, and codes 2. USCS disination is based on visual manual classification and selected lab testing 3. Groundwater level, if indicated, is for the date shown and may vary 4. NE = Not Encountered 5. ATD = At Time of Drilling Drilling Company:Boretec, Inc.Logged By:EJF Drilling Method:Hollow Stem Auger Drilling Date:06/19/2023 Drilling Rig:EC Track Rig Datum:NAVD88 Sampler Type:Spilt Spoon Elevation:136 feet Hammer Type:Rope Pulled Cathead Termination Depth:21.5 feet Hammer Weight:140lbs Latitude: Notes:Longitude: Topsoil Silty sand Poorly graded sand with silt Low plasticity clay Poorly graded sand Sheet 1 of JOB:Ramage.McMinnRoad FIG.A-3Depth(feet)Elevation (feet)Exploration notes Soil description SPT BlowcountsSamplerSymbolTest Results 1020304050Penetration - (blows per foot) % Water Content % Fines (<0.075mm)Plastic Limit Liquid Limit Groundwater1 Appendix B Laboratory Test Results These results are for the exclusive use of the client for whom they were obtained. They apply only to the samples tested and are not indicitive of apparently identical samples.Tested By: Checked By: Particle Size Distribution Report PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 0.0 0.6 0.8 14.6 68.5 15.56 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200Test Results (ASTM D 6913 & ASTM D 1140) Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Source of Sample: B-1 Depth: 55 Sample Number: S-11 Client: Project: Project No:Figure silty sand 0.375 #4 #10 #20 #40 #60 #100 #200 100.0 99.4 98.6 95.9 84.0 49.4 29.0 15.5 NP NV NP SM A-2-4(0) 0.4952 0.4339 0.2936 0.2526 0.1556 Natural Moisture: 6/19/23 6/22/23 MAW KSS PM 6/19/23 Richard Ramage Proposed Single-Family Residence Ramage.McMinnRoad PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) GeoResources, LLC Fife, WA B-1 These results are for the exclusive use of the client for whom they were obtained. They apply only to the samples tested and are not indicitive of apparently identical samples.Tested By: Checked By: Particle Size Distribution Report PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 88.06 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200Test Results (ASTM D 6913 & ASTM D 1140) Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Source of Sample: B-2 Depth: 7.5 Sample Number: S-3 Client: Project: Project No:Figure Clay with some silt #200 88.0 21 44 23 CL Natural Moisture: 6/19/23 6/22/23 MAW KSS PM 6/19/23 Richard Ramage Proposed Single-Family Residence Ramage.McMinnRoad PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) GeoResources, LLC Fife, WA B-2a These results are for the exclusive use of the client for whom they were obtained. They apply only to the samples tested and are not indicitive of apparently identical samples.Tested By: Checked By: GeoResources, LLC Fife, WA Client: Project: Project No.:Figure Richard Ramage Proposed Single-Family Residence Ramage.McMinnRoad B-2b SYMBOL SOURCE NATURAL USCSSAMPLEDEPTHWATERPLASTICLIQUIDPLASTICITY NO.CONTENT LIMIT LIMIT INDEX (%)(%)(%)(%) SOIL DATAPLASTICITY INDEX0 10 20 30 40 50 60 LIQUID LIMIT 0 10 20 30 40 50 60 70 80 90 100 110 CL-ML CL or OL CH or O H ML or OL MH or OH Dashed line indicates the approximate upper limit boundary for natural soils 47 LIQUID AND PLASTIC LIMITS TEST REPORT B-2 S-3 7.5 18.1 21 44 23 CL Appendix C Water Well Reports Appendix D Slope Stability Results 1.2051.4921.205WW1.2051.4921.205RuHu TypeWater SurfacePhi (deg)Cohesion (psf)Strength TypeSat. Unit Weight (lbs/ft3)Unit Weight (lbs/ft3)ColorMaterial Name0None340Mohr-Coulomb120Beach Deposits0None24400Mohr-Coulomb110Silty CLAY with some sand (ML) BC 33 to 46 (Vashon Advance Glaciolacustrine)0None40100Mohr-Coulomb125Poorly graded SAND with some to minor gravel and some to trace silt (SP, SP-SM) BC 18 to 49 (Vashon Advance Outwash)0None451500Mohr-Coulomb130Gravelly silty SAND (SM) BC > 50 (Glacial Till)Automatically CalculatedWater Surface36600Mohr-Coulomb120110Silty SAND (SM) BC > 50 (Glacial and Nonglacial Deposits, undivided)Boring B-1Boring B-277.4553002001000-100-50050100150200250300350400450500ScenarioStatic ConditionsGroupExisting ConfigurationCompanyGeoResources, LLCDrawn ByEJF/MAEFile NameRamage.McMinnRoad.slmdDate6/19/2023, 10:06:01 AMProjectSlide2 - An Interactive Slope Stability ProgramSLIDEINTERPRET 9.026 WW1.0931.0930.9500.9500.9500.950RuHu TypeWater SurfacePhi (deg)Cohesion (psf)Strength TypeSat. Unit Weight (lbs/ft3)Unit Weight (lbs/ft3)ColorMaterial Name034 None0Mohr-Coulomb120Beach Deposits024 None400Mohr-Coulomb110Silty CLAY with some sand (ML) BC 33 to 46 (Vashon Advance Glaciolacustrine)040 None100Mohr-Coulomb125Poorly graded SAND with some to minor gravel and some to trace silt (SP, SP-SM) BC 18 to 49 (Vashon Advance Outwash)045 None1500Mohr-Coulomb130Gravelly silty SAND (SM) BC > 50 (Glacial Till)Automatically CalculatedWater 36Surface600Mohr-Coulomb120110Silty SAND (SM) BC > 50 (Glacial and Nonglacial Deposits, undivided)72.461Boring B-2Boring B-1 0.173002001000-100-50050100150200250300350400450500ScenaPserioudo-Static Conditions for till, firm glaciated soils (JeffersonGroupExisting ConfigurationCompanyDrawn ByEJF/MAEFile NameRamage.McMinnRoad.slmdDate6/19/2023, 10:06:01 AMProjectSlide2 - An Interactive Slope Stability ProgramSLIDEINTERPRET 9.026 1.2051.4811.205WW 2000.00 lbs/ft21.2051.4811.205Boring B-2Boring B-1RuHu TypeWater SurfacePhi (deg)Cohesion (psf)Strength TypeSat. Unit Weight (lbs/ft3)Unit Weight (lbs/ft3)ColorMaterial Name0None500Mohr-Coulomb150Concrete0None340Mohr-Coulomb120Beach Deposits0None24400Mohr-Coulomb110Silty CLAY with some sand (ML) BC 33 to 46 (Vashon Advance Glaciolacustrine)0None40100Mohr-Coulomb125Poorly graded SAND with some to minor gravel and some to trace silt (SP, SP-SM) BC 18 to 49 (Vashon Advance Outwash)0None451500Mohr-Coulomb130Gravelly silty SAND (SM) BC > 50 (Glacial Till)Automatically CalculatedWater Surface36600Mohr-Coulomb120110Silty SAND (SM) BC > 50 (Glacial and Nonglacial Deposits, undivided)Proposed Footprint of Residence75Ō Recommended Buffer + Setback250200150100500-50-50050100150200250300350400ScenarioStatic ConditionsGroupProposed Site Configuration CompanyGeoResources, LLCDrawn ByEJF/MAEFile NameRamage.McMinnRoad.slmdDate6/19/2023, 10:06:01 AMProjectSlide2 - An Interactive Slope Stability ProgramSLIDEINTERPRET 9.026 WW 2000.00 lbs/ft21.0991.0990.9500.9500.9500.950Boring B-Boring B-172.528RuHu TypeWater SurfacePhi (deg)Cohesion (psf)Strength TypeSat. Unit Weight (lbs/ft3)Unit Weight Color(lbs/ft3)Material Name0None500Mohr-Coulomb150Concrete0None340Mohr-Coulomb120Beach Deposits0None24400Mohr-Coulomb110Silty CLAY with some sand (ML) BC 33 to 46 (Vashon Advance Glaciolacustrine)0None40100Mohr-Coulomb125Poorly graded SAND with some to minor gravel and some to trace silt (SP, SP-SM) BC 18 to 49 (Vashon Advance Outwash)0None451500Mohr-Coulomb130Gravelly silty SAND (SM) BC > 50 (Glacial Till)Automatically CalculatedWater 36Surface600Mohr-Coulomb120110Silty SAND (SM) BC > 50 (Glacial and Nonglacial Deposits, undivided) 0.173002001000-1000100200300400500ScenaPserioudo-Static Conditions for till, firm glaciated soils (JeffersonGroupProposed Site Configuration CompanyDrawn ByEJF/MAEFile NameRamage.McMinnRoad.slmdDate6/19/2023, 10:06:01 AMProjectSlide2 - An Interactive Slope Stability ProgramSLIDEINTERPRET 9.026 South Sound Geotechnical Consulting September 8, 2020 Mr. Richard Ramage c/o Chambers Bay Construction 3800A Bridgeport Way, Suite 162 Subject: Geotechnical Engineering Report 750 McMinn Road Development Port Townsend, Washington SSGC Project No. 20068 Mr. Ramage, South Sound Geotechnical Consulting (SSGC) has completed a geotechnical assessment for the planned development on the above address property in Port Townsend, Washington. Our services have been completed in general conformance with our proposal P20058 (dated July 29, 2020) and authorized per signature of our agreement for services. Our scope of services included completion of three test pits and one infiltration test, laboratory testing, engineering analyses, and preparation of this report. PROJECT INFORMATION The property is a long and narrow lot with the long axis oriented in a generally north-south direction. The McMinn Road easement bisects the property with the proposed residence on the north side of the lot. A second residence may be located in the southern portion of the lot in the future We anticipate conventional spread footing foundations will be used for support of new structures. Infiltration facilities will be used to support stormwater control. SITE CONDITIONS The northern boundary of the property is along the shore of the Strait of Juan De Fuca. It is characterized with a bluff along the shoreline having a height of approximately 100 (+/-) feet per Google satellite imagery. The remainder of the property is generally level with about 10 (+/-) feet of elevation change. Vegetation consists of generally mature forest growth (conifer trees) north of McMinn Road, with mixed forest and brush in the southern portion. SUBSURFACE CONDITIONS Subsurface conditions were characterized by completing three test pits and one infiltration test on the site on August 8, 2020. Test holes were advanced to final depths between about 8 and 10 feet below existing ground surface. Approximate locations of test pits and infiltration test sites are shown on Figure 1, Exploration Plan. Logs of these explorations are provided in Appendix A. A summary description of observed subgrade conditions is provided below. Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 2 Soil Conditions Topsoil/duff was observed below the surface and extended to an average depth of about 1 foot at the test locations. Native soil below the topsoil in the northern portion of the site (Test pit TP-1 and infiltration test PIT-1 consisted of an upper silty sand with variable gravel. This soil was in a loose condition and extended to a depth of around 2.5 feet. Gravelly sand with trace silt to sand was below the upper layer. This soil was in a loose to medium dense condition and extended to the termination depth of these excavations. Native soil below the topsoil/cuff in test pits TP-2 and TP-3 consisted of silt/clay with some fine sand. This soil was in a stiff condition and extended to depths of 4 in TP-2 and to the termination depth of 10 feet in pit TP-3. Sand with some silt and gravel was below the silt/clay in test pit TP- 2 and extended to the termination depth of 10 feet. Groundwater Conditions Groundwater was observed in test pit TP-2 at a depth of about 9.5 feet at the time of excavation. This water was associated with the sand and gravel below the upper silt/clay soil. Groundwater was not observed in the remaining excavations. Groundwater levels will vary throughout the year based on seasonal precipitation and on- and off-site drainage patterns. Geologic Setting Soils on the site are mapped as “Clallam gravelly sandy loam” per the USDA Soil Conservation Service map of Jefferson County. Clallam soil reportedly formed on glacial terraces. Granular soils in the explorations appear to generally conform with the mapped soil type, with less fines. However, the upper clay and silt observed in test pits TP-2 and TP-3 are interpreted to be a different soil type. The bluff on the north side of the lot is mapped as Pre-Fraser (last glacial advance) glacial drift and till per the Washington State DNR “Geologic Map of the Port Townsend South and Part of the Port Townsend North 7.5-minute Quadrangle, Jefferson County, Washington”, dated 2005. The level portion of the site (above the bluff) is mapped as ablation till. GEOTECHNICAL DESIGN CONSIDERATIONS Planned development is considered feasible based on observed soil conditions in the explorations. Properly prepared native soils can be used for support of conventional spread footing foundations, floor slabs, and pavements. Currently, the new planned residence will be on the order of 100 feet south of the bluff. Infiltration to assist in stormwater control is considered feasible in the granular soils observed in test pit TP-1 and the PIT-1 site. However, infiltration in the silt/clay soils observed in test pits TP-2 and TP-3 is not feasible. Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 3 Recommendations presented in the following sections should be considered general and may require modifications at the time of construction. They are based upon the subsurface conditions observed in the explorations and the assumption that finish site grades will be similar to existing grades. It should be noted subsurface conditions across the site can vary from those depicted on the exploration logs and can change with time. Therefore, proper site preparation will depend upon the weather and soil conditions encountered at the time of construction. We recommend SSGC review final plans and further assess subgrade conditions at the time of construction, as warranted. General Site Preparation Site grading and earthwork should include procedures to control surface water runoff. Grading the site without adequate drainage control measures may negatively impact site soils, resulting in increased export of impacted soil and import of fill materials, thereby potentially increasing the cost of the earthwork and subgrade preparation phases of the project. Site grading should include removal (stripping) of topsoil/duff and any fill encountered, or very loose or soft soils in building and pavement areas. Topsoil extended to a depth of about 1 foot in the test holes but may be deeper or shallower in other areas. Final stripping depths can only be determined at the time of construction. Subgrades should consist of firm, undisturbed native soils following stripping. General Subgrade Preparation Subgrades in building footprints and pavement areas should consist of firm, undisturbed native soils. We recommend exposed subgrades in building and conventional pavement areas are proofrolled using a large roller, loaded dump truck, or other mechanical equipment to assess subgrade conditions following stripping. Proofrolling efforts should result in the upper 1 foot of subgrade soils in building and conventional pavement areas achieving a firm and unyielding condition (or a compaction level of at least 95 percent of the maximum dry density (MDD) per the ASTM D1557 test method). Wet, loose, or soft subgrades that pump or cannot achieve this compaction level should be removed (over-excavated) and replaced with structural fill. The depth of over-excavation should be based on soil conditions at the time of construction. A representative of SSGC should be present to assess subgrade conditions during proofrolling. Grading and Drainage Positive drainage should be provided during construction and maintained throughout the life of the development. Surface water should not be allowed to flow into construction excavations or fill areas. Structural Fill Materials The suitability of soil for use as structural fill will depend on the gradation and moisture content of the soil when it is placed. Soils with higher fines content (soil fraction passing the U.S. No. 200 sieve) will Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 4 become sensitive with higher moisture content. It is often difficult to achieve adequate compaction if soil moisture is outside of optimum ranges for soils that contain more than about 5 percent fines. Site Soils: Organic rich soils (topsoil/duff) and any fill are not considered suitable as structural fill. Native sand and gravel soils observed are considered suitable for structural fill, if properly moisture conditioned. The silt/clay is not considered suitable for structural fill as it is moisture sensitive and will be difficult to achieve optimum moisture content and uniform compaction. Import Fill Materials: We recommend imported structural fill placed during dry weather consist of material which meets the specifications for Gravel Borrow as described in Section 9-03.14(1) of the 2018 Washington State Department of Transportation (WSDOT) Specifications for Road, Bridge, and Municipal Construction manual (Publication M 41-10). Gravel Borrow should be protected from disturbance if exposed to wet conditions after placement. During wet weather, or for backfill on wet subgrades, import soil suitable for compaction in wetter conditions should be provided. Imported fill for use in wet conditions should conform to specifications for Select Borrow as described in Section 9-03.14(2), or Crushed Surfacing per Section 9-03.9(3) of the 2018 WSDOT M-41 manual, with the modification that a maximum of 5 percent by weight shall pass the U.S. No. 200 sieve for these soil types. Structural fill placement and compaction is weather-dependent. Delays due to inclement weather are common, even when using select granular fill. We recommend site grading and earthwork be scheduled for the drier months of the year. Structural fill should not consist of frozen material. Structural Fill Placement We recommend structural fill is placed in lifts not exceeding about 10 inches in loose measure. It may be necessary to adjust lift thickness based on site and fill conditions during placement and compaction. Finer grained soil used as structural fill and/or lighter weight compaction equipment may require significantly thinner lifts to attain required compaction levels. Granular soil with lower fines contents could potentially be placed in thicker lifts (1 foot maximum) if they can be adequately compacted. Structural fill should be compacted to attain the recommended levels presented in Table 1, Compaction Criteria. Table 1. Compaction Criteria Fill Application Compaction Criteria* Footing areas 95 % Upper 2 feet in pavement areas, flatwork, and utility trenches 95 % Below 2 feet in pavement areas, flatwork, and utility trenches 92 % Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 5 Utility trenches or general fill in non-paved or -building areas 90 % *Per the ASTM D 1557 test method. Trench backfill within about 2 feet of utility lines should not be over-compacted to reduce the risk of damage to the line. In some instances, the top of the utility line may be within 2 feet of the surface. Backfill in these circumstances should be compacted to a firm and unyielding condition. We recommend fill procedures include maintaining grades that promote drainage and do not allow ponding of water within the fill area. The contractor should protect compacted fill subgrades from disturbance during wet weather. In the event of rain during structural fill placement, the exposed fill surface should be allowed to dry prior to placement of additional fill. Alternatively, the wet soil can be removed. We recommend consideration is given to protecting haul routes and other high traffic areas with free-draining granular fill material (i.e. sand and gravel containing less than 5 percent fines) or quarry spalls to reduce the potential for disturbance to the subgrade during inclement weather. Earthwork Procedures Conventional earthmoving equipment should be suitable for earthwork at this site. Earthwork may be difficult during periods of wet weather or if elevated soil moisture is present. Excavated site soils may not be suitable as structural fill depending on the soil moisture content and weather conditions at the time of earthwork. If soils are stockpiled and wet weather is anticipated, the stockpile should be protected with securely anchored plastic sheeting. If stockpiled soils become wet and unusable, it will become necessary to import clean, granular soils to complete wet weather site work. Wet or disturbed subgrade soils should be over-excavated to expose firm, non-yielding, non-organic soils and backfilled with compacted structural fill. We recommend the earthwork portion of this project be completed during extended periods of dry weather. If earthwork is completed during the wet season (typically October through April) it may be necessary to take extra measures to protect subgrade soils. If earthwork takes place during freezing conditions, we recommend the exposed subgrade is allowed to thaw and re-compacted prior to placing subsequent lifts of structural fill. Alternatively, the frozen soil can be removed to unfrozen soil and replaced with structural fill. The contractor is responsible for designing and constructing stable, temporary excavations (including utility trenches) as required to maintain stability of excavation sides and bottoms. Excavations should be sloped or shored in the interest of safety following local and federal regulations, including current OSHA excavation and trench safety standards. Temporary excavation cuts should be sloped at inclinations of 1.5H:1V (Horizontal:Vertical) or flatter, unless the contractor can demonstrate the safety of steeper cut slopes. It should be noted cleaner sand and gravel soils have the tendency to cave into open excavations. Shoring may be necessary for deeper utility trenches on this site. Permanent cut and fill slopes should be inclined at grades of 2H:1V, or flatter. Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 6 A geotechnical engineer and accredited materials testing firm should be retained during the construction phase of the project to observe earthwork operations and to perform necessary tests and observations during subgrade preparation, placement and compaction of structural fill, and backfilling of excavations. Foundations Foundations can be placed on firm native soils or on a zone of structural fill above prepared subgrades as described in this report. The following recommendations are for conventional spread footing foundations: Bearing Capacity (net allowable): 2,000 pounds per square foot (psf) for footings supported on firm native soils or structural fill over native subgrades prepared as described in this report. Footing Width (Minimum): 16 inches (Strip) 24 inches (Column) Embedment Depth (Minimum): 18 inches (Exterior) 12 inches (Interior) Settlement: Total: < 1 inch Differential: < 1/2 inch (over 30 feet) Allowable Lateral Passive Resistance: 300 psf/ft* (below 12 inches) Allowable Coefficient of Friction: 0.35* *These values include a factor of safety of approximately 1.5. The net allowable bearing pressures presented above may be increased by one-third to resist transient, dynamic loads such as wind or seismic forces. Lateral resistance to footings should be ignored in the upper 12-inches from exterior finish grade unless restricted. Foundation Construction Considerations All foundation subgrades should be free of water and loose soil prior to placing concrete, and should be prepared as recommended in this report. Concrete should be placed soon after excavating and compaction to reduce disturbance to bearing soils. Should soils at foundation level become excessively dry, disturbed, saturated, or frozen, the affected soil should be removed prior to placing concrete. We recommend SSGC observe foundation subgrades prior to placement of concrete. Foundation Drainage Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 7 Ground surface adjacent foundations should be sloped away to facilitate drainage. We recommend footing drains are installed around perimeter footings. Footing drains should include a minimum 4- inch diameter perforated rigid plastic or metal drain line installed along the exterior base of the footing. The perforated drain lines should be connected to a tight line pipe that discharges to an approved storm drain receptor. The drain line should be surrounded by a zone of clean, free-draining granular material having less than 5 percent passing the No. 200 sieve or meeting the requirements of section 9-03.12(2) “Gravel Backfill for Walls” in the 2018 WSDOT (M41-10) manual. The free- draining aggregate zone should be at least 12 inches wide and wrapped in filter fabric. The granular fill should extend to within 6 inches of final grade where it should be capped with compacted fill containing sufficient fines to reduce infiltration of surface water into the footing drains. Alternately, the ground surface can be paved with asphalt or concrete. Cleanouts are recommended for maintenance of the drain system. On-Grade Floor Slabs On-grade floor slabs should be placed on native soils or structural fill prepared as described in this report. We recommend a modulus subgrade reaction of 175 pounds per square inch per inch (psi/in) for native soil or compacted granular structural fill over properly prepared native soil. We recommend a capillary break is provided between the prepared subgrade and bottom of slab. Capillary break material should be a minimum of 4 inches thick and consist of compacted clean, free- draining, well graded coarse sand and gravel. The capillary break material should contain less than 5 percent fines, based on that soil fraction passing the U.S. No. 4 sieve. Alternatively, a clean angular gravel such as No. 7 aggregate per Section 9-03.1(4) C of the 2018 WSDOT (M41-10) manual could be used for this purpose. We recommend positive separations and/or isolation joints are provided between slabs and foundations, and columns or utility lines to allow independent movement where needed. Backfill in interior trenches beneath slabs should be compacted in accordance with recommendations presented in this report. A vapor retarder should be considered beneath concrete slabs that will be covered with moisture sensitive or impervious coverings (such as tile, wood, etc.), or when the slab will support equipment or stored materials sensitive to moisture. We recommend the slab designer refer to ACI 302 and/or ACI 360 for procedures and limitations regarding the use and placement of vapor retarders. Seismic Considerations Recommended seismic parameters and values in Table 2 are based on the 2015 International Building Code (IBC) Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 8 Table 2. Seismic Parameters PARAMETER VALUE 2015 International Building Code (IBC) Site Classification1 D Ss Spectral Acceleration for a Short Period 1.293 S1 Spectral Acceleration for a 1-Second Period 0.525g Fa Site Coefficient for a Short Period 1.00 Fv Site Coefficient for a 1-Second Period 1.5 1 Note: In general accordance with 2015 International Building Code, Section 1613.3.1 for risk categories I,II,III. IBC Site Class is based on the estimated characteristics of the upper 100 feet of the subsurface profile. Ss, S1, Fa, and Fv values based on the OSHPD Seismic Design Maps website. Liquefaction Soil liquefaction is a condition where loose, typically granular soils located below the groundwater surface lose strength during ground shaking, and is often associated with earthquakes. The Jefferson County “Liquefaction Susceptibility” map identifies this area as having a very low to low risk to liquefaction. Subgrade soils consist of glacially consolidated drift and till and are not considered highly susceptible to liquefaction. Infiltration Characteristics We understand stormwater control will use infiltration facilities, where feasible. General assessment of infiltration potential of native soils was performed by completing one small-scale Pilot Infiltration Test (PIT) on the site per the 2012 WDOE Stormwater Management Manual for Western Washington. Test PIT-1 was completed in native gravelly sand on the north side of McMinn Road. Results of the infiltration test is presented in Table 3. Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 9 Table 3. Infiltration Test Results Infiltration Test No. Depth of Test from Surface (feet) Soil Type Field Infiltration Rate (in/hr) Corrected Infiltration Rate (in/hr) Correction Factors* (CFv/CFt/CFm) PIT-1 3 Native Gravel/Sand 6 2.1 (0.8/0.5/0.9) *Correction Factors from the 2012 WDOE SWMM for Western Washington. The tested infiltration rate from PIT-1 is considered appropriate for the observed native soil. We recommend an average long-term design rate of 2 inches per hour (in/hr) for the native glacial soils to account for soil variability. Should final site grades remain similar to existing, it appears that sufficient separation from groundwater or impermeable soils should be achievable for conventional infiltration systems and individual roof trench systems in the site, north of the McMinn Road easement. Future development in the southern portion of the lot may require retention/detention or shallow dispersion systems to facilitate stormwater control due to the silt/clay observed in the test pits in this area. Cation Exchange Capacity (CEC) and organic content tests were completed on a sample from the bottom of infiltration test hole. Test results are summarized in Table 4. Table 4. CEC and Organic Content Results Test Location, Sample Number, Depth CEC Results (milliequivalents) CEC Required* (milliequivalents) Organic Content Results (%) Organic Content Required* (%) PIT-1, S-1, 3 feet 7.4 ≥ 5 1.45 ≥1.0 *Per the 2012 WDOE SWMM for Western Washington. Organic content and CEC test results satisfy state criteria on the tested sample. GEOLOGIC ASSESSMENT - CRITICAL AREA SLOPES The following documents were reviewed as part of our critical area assessment of the bluff on the north boundary of the property: Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 10 ◼ U.S. Department of Agriculture Soil Conservation Service, Soil Survey of Jefferson County Area, Washington. ◼ Jefferson County Municipal Code (JCMC). ◼ Washington State DNR Geologic Information Portal Web Site. ◼ Washington State DNR “Geologic Map of the Port Townsend South and Part of the Port Townsend North 7.5-minute Quadrangle, Jefferson County, Washington”, dated 2005. ◼ Washington State Coastal Atlas Maps. ◼ Google Maps Document Summary Per Chapter 18.22 of the JCMC, the bluff along the north property boundary is in a landslide hazard area. The bluff is near vertical and has relief of around 100 feet. The Coastal Atlas map depicts the area within approximately 150 (+/-) feet of the bluff as unstable, with the remainder of the site as stable. The Washington DNR portal site and geologic map of the area does show the bluff throughout the area has experienced localized slides. SLOPE CONDITIONS SSGC completed a reconnaissance of the bluff on August 10, 2020 as part of our geotechnical evaluation of the property. Our observations include: ▪ The bluff consists of exposed glacially consolidated soil with exposed soil and some brush and tree growth. Mature conifer trees at the top of the bluff exhibited generally straight trunks. Evidence of recent slides on the bluff across the property boundaries was not observed. ▪ Evidence of existing slope movement (such as tension cracks, down-dropped blocks etc.) was not observed on the site above the bluff at the time of our visit. ▪ Seepage or surface water was not observed on the bluff at the time of our site visit. Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 11 GEOLOGIC HAZARD AREAS DISCUSSION Chapter 18.22 of the JCMC addresses critical areas and hazard protection standards. Based upon our review of the previously referenced documents and our field observations, we offer the following statements regarding the landslide hazard areas as described in the JCMC. Soils on the northwest-facing bluff generally consist of dense glacially consolidated deposits. Evidence of recent landslide activity (tension cracks, down-dropped blocks, etc.) was not observed on the bluff at the time of our site visit. Currently, the planned residence will be on the order of 100 feet away from the top of the bluff. This setback is considered suitable based on observed and mapped conditions of the bluff. It is our opinion the development can be constructed without adversely affecting the stability of the bluff. Based on provided information, no planned construction activities will occur within 100 feet of the bluff. We recommend roof stormwater trenches for the proposed residence are located to the south of the building (away from the bluff). Concentrated runoff should not be allowed to flow onto the bluff. Erosion Hazard The proposed development will not require earthwork or alteration to the steep northwest-facing bluff. With regard to construction for this development, it is our opinion that Best Management Practices (BMP) for erosion control (silt fencing, straw bales, etc.) can be utilized such that the risk of off-site transport of sediment is limited during construction. Additional erosion control measures may be necessary if earthwork is scheduled during the wetter seasons. All erosion control provisions should be in compliance with Jefferson County regulations to reduce the risk of off-site transport of sediments. Exposed soils following any construction should be vegetated as soon as possible. Irrigation should be minimized on or near steeper slopes. Temporary and permanent stormwater control measures should prevent concentrated flow onto the northwest-facing bluff. REPORT CONDITIONS This report has been prepared for the exclusive use of Mr. Richard Ramage and his agents for specific application to the project discussed, and has been prepared in accordance with generally accepted geotechnical engineering practices in the area. No warranties, either express or implied, are intended or made. The analysis and recommendations presented in this report are based on observed soil conditions and test results at the indicated locations, and from other geologic information discussed. This report does not reflect variations that may occur across the site, or due to the modifying effects of construction or weather or other natural events. The nature and extent of such variations may not become evident until during or after construction. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided. Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 12 This report was prepared for the planned type of development of the site as discussed herein. It is not valid for third party entities or alternate types of development on the site without the express written consent of SSGC. If development plans change we should be notified to review those changes and modify our recommendations as necessary. The scope of services for this project does not include any environmental or biological assessment of the site including identification or prevention of pollutants, hazardous materials, or conditions. Other studies should be completed if the owner is concerned about the potential for contamination or pollution. We appreciate the opportunity to work with you on this project. Please contact us if additional information is required or we can be of further assistance. Respectfully, South Sound Geotechnical Consulting DRAFT Timothy H. Roberts, P.E. Member/Geotechnical Engineer Attachments: Figure 1 – Exploration Plan Appendix A – Field Exploration Procedures and Exploration Logs Appendix B – Laboratory Testing and Results Unified Soil Classification System N South Sound Geotechnical Consulting P.O. Box 39500 Lakewood, WA 98496 (253) 973-0515 Figure 1 – Exploration Plan 750 McMinn Road Port Townsend, WA SSGC Project #20068 Approximate Test Pit Location PIT - 1 TP - 1 PIT - 1 Approximate Infiltration Test Location Scale: NTS Base map Google Maps Legend PIT-1 TP-2 TP-1 TP-3 Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 A-1 Appendix A Field Exploration Procedures and Exploration Logs Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 Field Exploration Procedures Our field exploration for this project included three test pits and one infiltration test completed on August 8, 2020. The approximate locations of the explorations are shown on Figure 1, Exploration Plan. The exploration locations were determined by pacing from site features. Ground surface elevations referenced on the logs were inferred from Google Satellite imagery. Test pit locations and elevations should be considered accurate only to the degree implied by the means and methods used. A client provided backhoe and operator dug the test holes. Soil samples were collected and stored in moisture tight for further assessment and laboratory testing. Explorations were backfilled with excavated soils and tamped when completed. Please note that backfill in the explorations may settle with time. Backfill material located in building or road areas should be re-excavated and recompacted, or replaced with structural fill. The following logs indicate the observed lithology of soils and other materials observed in the explorations at the time of excavation. Where a soil contact was observed to be gradational, our log indicates the average contact depth. Our logs also indicate the approximate depth to groundwater (where observed at the time of excavation), along with sample numbers and approximate sample depths. Soil descriptions on the logs are based on the Unified Soil Classification System. Project: McMinn Rd Residence SSGC Job # 20068 EXPLORATION LOGS PAGE 1 OF 2 Location: Port Townsend, WA TEST PIT LOGS FIGURE A-1 South Sound Geotechnical Consulting PIT-1, TP-1 through TP-3 Logged by: THR Infiltration Test PIT-1 Depth (feet) Material Description 0 – 1 1 – 2.5 2.5 – 8 Topsoil/Duff: Silt, sand, with roots: Loose, damp, brown. Silty SAND with occasional gravel: Loose, damp, light brown. (SM) Gravelly SAND with trace silt: Loose to medium dense, damp, gray. (SP) (Sample S-1 @ 3 feet) Test hole completed at approximately 8 feet on 8/10/20. Infiltration test completed at 3 feet. Groundwater not observed at time of excavation. Approximate surface elevation: 140 feet Test Pit TP-1 Depth (feet) Material Description 0 – 1 1 – 2.5 2.5 – 8 8 – 9.5 Topsoil/Duff: Silt, sand, with roots: Loose, damp, brown. Silty SAND with occasional gravel: Loose, damp, light brown. (SM) Gravelly SAND with trace silt: Loose to medium dense, damp, gray. (SP) (Sample S-1 @ 3 feet) SAND with some silt and occasional gravel: Medium dense, moist, gray. (SM) (Sample S-2 @ 8 feet) Test pit completed at approximately 9.5 feet on 8/10/20. Groundwater not observed at time of excavation. Approximate surface elevation: 138 feet Project: McMinn Rd Residence SSGC Job # 20068 EXPLORATION LOGS PAGE 2 OF 2 Location: Port Townsend, WA TEST PIT LOGS FIGURE A-1 South Sound Geotechnical Consulting PIT-1, TP-1 through TP-3 Logged by: THR Test Pit TP-2 Depth (feet) Material Description 0 – 1 1 – 4 4 – 10 Topsoil/Duff: Silt, sand, with roots: Loose, damp, brown. CLAY/SILT with some fine sand: Stiff, moist, gray. (CL/ML) SAND with gravel and trace to some silt: Medium dense, moist, brownish gray. (SP) Test pit completed at approximately 10 feet on 8/10/20. Groundwater observed at 9.5 feet at time of excavation. Approximate surface elevation: 145 feet Test Pit TP-3 Depth (feet) Material Description 0 – 1 1 – 10 Topsoil/Duff: Silt, sand, with roots: Loose, damp, brown. CLAY/SILT with some fine sand: Stiff, moist, gray. (CL/ML) Test pit completed at approximately 10 feet on 8/10/20. Groundwater not observed at time of excavation. Approximate surface elevation: 143 feet Geotechnical Engineering Report SSGC Vista Heights Development – 66th Street East Fife, WA SSGC Project No. 20024 April 23, 2020 C-1 Appendix B Laboratory Testing and Results Geotechnical Engineering Report SSGC 750 McMinn Road Port Townsend, WA SSGC Project No. 20068 September 8, 2020 B-1 Laboratory Testing Select soil samples were tested for organic content and cation exchange capacity (CEC) by Northwest Agricultural Consultants of Kennewick, Washington. Gradation tests were completed by Construction Testing Laboratories (CTL) of Puyallup, Washington. Results of the laboratory testing are included in this appendix. Report shall not be reproduced except in full without the written approval of the Laboratory. Report pertains only to the material tested.Tested By: R Rowden Checked By: C Pedersen Particle Size Distribution Report ASTM C-117, C-136 PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0 0 23 10 24 38 56 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200SIEVE PERCENT SPEC.*PASS? SIZE FINER PERCENT (X=NO) Material Description Atterberg Limits Classification Remarks Source of Sample: PIT #1 Sample Number: 20-1116 Date: Client: Project: Project No:Figure Grab Sample, S-1 Sampled at 3'3/4" 1/2" 3/8" #4 #8 #10 #16 #40 #100 #200 100 96 90 77 70 67 62 43 8 5.3 Report: #02 Sampled by: Client South Sound Geotechnical McMinn (20068) 8665 PL=LL=PI= USCS=AASHTO= *(no specification provided) 08-10-20 Construction Testing Laboratories 400 Valley Ave. NE, Suite #102 Puyallup WA, 98372 Tel. (253) 383-8778 Report shall not be reproduced except in full without the written approval of the Laboratory. Report pertains only to the material tested.Tested By: M Armstrong Checked By: C Pedersen Particle Size Distribution Report ASTM C-117, C-136 PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0 6 28 23 28 13 26 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200SIEVE PERCENT SPEC.*PASS? SIZE FINER PERCENT (X=NO) Material Description Atterberg Limits Classification Remarks Source of Sample: TP-1 Sample Number: 20-1114 Date: Client: Project: Project No:Figure Grab Sample, S-1 Sampled at 3'1" 3/4" 1/2" 3/8" #4 #8 #10 #16 #40 #100 #200 100 94 87 83 66 47 43 34 15 3 2.2 SP Report: #01 Sampled by: Client South Sound Geotechnical McMinn (20068) 8665 PL=LL=PI= USCS=AASHTO= *(no specification provided) 08-10-20 Construction Testing Laboratories 400 Valley Ave. NE, Suite #102 Puyallup WA, 98372 Tel. (253) 383-8778 2545 W Falls Avenue Kennewick, WA 99336 509.783.7450 www.nwag.com lab@nwag.com Sample ID Organic Matter Cation Exchange Capacity Pit-1, S-1 1.45% 7.4 meq/100g Method ASTM D2974 EPA 9081 South Sound Geotechnical Consulting PO Box 39500 Lakewood, WA 98496 Report: 52354-1-1 Date: August 24, 2020 Project No: 20068 Project Name: McMinn Rd UNIFIED SOIL CLASSIFICATION SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory TestsA Soil Classification Group Symbol Group NameB Coarse Grained Soils More than 50% retained on No. 200 sieve Gravels More than 50% of coarse fraction retained on No. 4 sieve Clean Gravels Less than 5% finesC Cu  4 and 1  Cc  3E GW Well-graded gravelF Cu  4 and/or 1  Cc  3E GP Poorly graded gravelF Gravels with Fines More than 12% finesC Fines classify as ML or MH GM Silty gravelF,G, H Fines classify as CL or CH GC Clayey gravelF,G,H Sands 50% or more of coarse fraction passes No. 4 sieve Clean Sands Less than 5% finesD Cu  6 and 1  Cc  3E SW Well-graded sandI Cu  6 and/or 1  Cc  3E SP Poorly graded sandI Sands with Fines More than 12% finesD Fines classify as ML or MH SM Silty sandG,H,I Fines Classify as CL or CH SC Clayey sandG,H,I Fine-Grained Soils 50% or more passes the No. 200 sieve Silts and Clays Liquid limit less than 50 inorganic PI  7 and plots on or above “A” lineJ CL Lean clayK,L,M PI  4 or plots below “A” lineJ ML SiltK,L,M organic Liquid limit - oven dried  0.75 OL Organic clayK,L,M,N Liquid limit - not dried Organic siltK,L,M,O Silts and Clays Liquid limit 50 or more inorganic PI plots on or above “A” line CH Fat clayK,L,M PI plots below “A” line MH Elastic SiltK,L,M organic Liquid limit - oven dried  0.75 OH Organic clayK,L,M,P Liquid limit - not dried Organic siltK,L,M,Q Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat A Based on the material passing the 3-in. (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name. C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay. D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay E Cu = D60/D10 Cc = 6010 2 30 DxD )(D F If soil contains  15% sand, add “with sand” to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM. HIf fines are organic, add “with organic fines” to group name. I If soil contains  15% gravel, add “with gravel” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant. L If soil contains  30% plus No. 200 predominantly sand, add “sandy” to group name. M If soil contains  30% plus No. 200, predominantly gravel, add “gravelly” to group name. N PI  4 and plots on or above “A” line. O PI  4 or plots below “A” line. P PI plots on or above “A” line. Q PI plots below “A” line.