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HomeMy WebLinkAbout002014003 Geotech ReportSouth 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 230 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.