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HomeMy WebLinkAboutGEO2024-00048 BLD2024-00542 Piles, Piers - BLD Engineering / Geo-tech Reports - 4/3/2024 RECEIVED cr"�aoa y- "Jo PLANNING APR _ 3 2024 MASON COUNTY 15 W. Alder Ifital Checklist COMMUNITY SERVICES6 Building.Planning,Environmental Health.Community Health Geotechnical Report instructions: This checklist must be submitted with a Geotechnical Report and completed, signed, and stamped by the licensed professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to the Mason County Resource Ordinance. If an item is found not applicable, the report should explain the basis for the conclusion. Note:Unless specifically documented,this report does not provide compliance to the International Residential Code Sections R403.1.7 for foundations on or adjacent to slopes,Section R403.1.8 for expansive soils or section 1808.7.1 of the International Building Code Section for Foundations on or adjacent to slopes. Applicant/Owner Teresa Baker Parcel# 422125110503 Site Address 70 N Cedardale Lane, Hoodsport, WA (1) (a) A discussion of general geologic conditions in the vicinity of the proposed development, Located on page(s) 2 (b) A discussion of specific soil types, Located on page(s) 4 (c) A discussion of ground water conditions, Located on page(s) 4 (d) A discussion of the upslope geomorphology, Located on page(s) 2 (e) A discussion of the location of upland waterbodies and wetlands, Located on page(s) NIA,none are present to best of our knowledge (f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and records. Located on page(s) 6 (2) A site plan which identifies the important development and geologic features. Located on Map(s) Figure 2 (3) Locations and logs of exploratory holes or probes. Located on Map(s) Figure 2 (4) The area of the proposed development, the boundaries of the hazard, and associated buffers and setbacks shall be delineated (top, both sides, and toe)on a geologic map of the site. Located on Map(s) Figure 2 (5) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and which incorporates the details of proposed grade changes. Located on Map(s) N/A, no grade changes are planned (6) A description and results of slope stability analyses performed for both static and seismic loading conditions. Analysis should examine worst case failures.The analysis should include the Simplified Bishop's Method of Circles.The minimum static safety factor is 1.5,the minimum seismic safety factor is 1.1, and the quasi-static analysis coefficients should be a value of 0.15. Located on page(s) NIA,see section 8.2.2 for review of slope stability on a qualitative basis (7) (a) Appropriate restrictions on placement of drainage features, Rev.February 2018 Located on page(s NIA, project does not include new drains (b) Appropriate restrictions on placement of septic drain fields, Located on page(s) N/A,project does not include new septic system (c) Appropriate restrictions on placement of compacted fills and footings, Located on page(s) NIA,fills will be limited Io backfifling localized excavations next to home (d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes. Located on page(s) NIA,all work will be done adjacent to existing home (e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes. Located on page(s) NIA,all work will be done adjacent to existing home (8) Recommendations for the preparation of a detailed clearing and grading plan which specifically identifies vegetation to be removed, a schedule for vegetation removal and replanting, and the method of vegetation removal. Located on page(s) NIA,all work will be adjacent to existing foundations (9) Recommendations for the preparation of a detailed temporary erosion control plan which identifies the specific mitigating measures to be implemented during construction to protect the slope from erosion, landslides and harmful construction methods. Located on page(s) NIA,all work will be done adjacent to existing home (10) An analysis of both on-site and off-site impacts of the proposed development. Located on page(s) NIA,project will not have an appreciable on-site or off-site (11) Specifications of final development conditions such as,vegetative management, drainage, erosion control, and buffer widths. Located on page(s) N/A,all work will be done adjacent to existing home (12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation. Located on page(s) 7 through 9 (13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location and nature of existing and proposed development on the site. Located on Map(s) Figure 2 Brad Wilcox, P.E., hereby certify under penalty of perjury that I am a civil engineer.licensed in the State of Washington with specialized knowledge of geotechnicaVgeological engineering or a geologist or engineering geologist licensed in the State of Washington with special knowledge of the local conditions. I also certify that the -- Geotechnical Report, dated April 3, 2024 , and entitled © o�W'`s` ��t "Report of Geotechnical Investigation" i y / p meets all the requirements of the Mason County Resource Ordinance, .. Geologically Hazardous Areas Section, is complete and true, that the assessment demonstrates conclusively that the risks posed by the art landslide hazard can be mitigated through the included geotechnical jo design recommendations, and that all hazards are mitigated in such a Z manner as to prevent harm to property and public health and safety. Page 2 of 2 Disclaimer. Mason County does not certify the quality of the Mork done in this Geotechnical Report. Carlson Geotechnical Bend Office (541)330-9155 �p.RLsoy Eugene Office (541)345-0289 A division of Carlson Testing, Inc. Salem Office (503)589-1252 Phone:(503)601-8250 Tigard Office (503)684-3460 www.carlsontestinct.com April 3, 2024 Ashley Haney TerraFirma Foundation Systems 13110 SW Wall Street Tigard, Oregon 97223 Report of Geotechnical Investigation Baker Residence 70 North Cedardale Lane Mason County,Washington CGT Project Number G2406096 1.0 INTRODUCTION Carlson Geotechnical (CGT), a division of Carlson Testing, Inc. (CTI), is pleased to submit this report summarizing the results of our geotechnical investigation for the proposed foundation improvements at the Baker Residence. The site is located at 70 North Cedardale Lane in Mason County, Washington. We performed our work in general accordance with CGT Proposal GP24-040, dated February 12, 2024. Written authorization for our services was received on February 26, 2024. 2.0 PROJECT UNDERSTANDING CGT developed an understanding of the proposed project based on our correspondence and review of the provided structural plans, prepared by Vista Structural Engineering LLC. Current plans for the project include the installation of four push piers and eight driven pin (pipe) piles to underpin the existing continuous wall foundations along the north and east perimeter walls of the existing residential structure in order to help alleviate structural distress. Design of the piers and piles will rest with others. Per our recent correspondence, geotechnical investigation is needed to help assess subsurface conditions and develop recommendations for use in final design and installation of the specialty piling. Based on our correspondence, we understand the local building official, Mason County, has required a geotechnical report be prepared for this project as part of permitting. 3.0 SCOPE OF SERVICES Our scope of work included the following: • Contact the Washington Utilities Notification Center to mark the locations of any public utilities within a 20-foot radius of our explorations at the site. • Explore subsurface conditions at the site by advancing three hand auger borings to practical refusal depths of up to about 63/4 feet below ground surface (bgs). • Classify the soils encountered in the borings in general accordance with ASTM D2488 (Visual-Manual Procedure). • Collect representative, disturbed (grab) samples of the soils encountered within the borings in order to perform laboratory testing and to confirm our field classifications. Office: 18270 SW Boones Ferry Road, Suite 6, Durham, Oregon 97224 Mailing: P.O. Box 230997,Tigard, Oregon 97281 Baker Residence Mason County, Washington CGT Project Number G2406096 April3, 2024 • Perform laboratory testing of soil samples taken from within our borings, including four moisture content determinations (ASTM D2216) and one plasticity (Atterberg limits) test(ASTM D4318). • Prepare this written report to include the following: o A site vicinity map and site plan showing the approximate location of the explorations relative to existing site features. o Logs of the borings, including results of laboratory testing performed on selected soil samples. o A technical narrative describing the completed field investigation and descriptions of the subsurface materials encountered. o Recommendations for Seismic Site Class, mapped spectral response accelerations, site seismic coefficients, and maximum considered earthquake (MCE) response accelerations. o A qualitative evaluation of seismic hazards at the site, including earthquake-induced liquefaction, landsliding, and surface rupture due to faulting or lateral spread. o Geotechnical recommendations for use in design and installation of push piers and driven pin piles at the site. 4.0 SITE DESCRIPTION 4.1 Site Geology Based on available geologic mapping' of the area, the site is located near a contact between two glacial till and outwash deposits: Olympic sourced glacial deposits (Qapd) and northern sourced glacial deposits (Qpd). Both of these deposits pre-date the Fraser glaciation, which includes the commonly seen Vashon Deposits, which are 10,000 to 20,000 years old. The Olympic deposits consist of compacted, gray to orange/brown, cobbles, gravels and boulders in a sandy to clayey matrix and were derived from glaciation and resulting outwash at high elevations in the Olympic Mountains. The northern sourced glacial deposits are identified on the basis of containing high-grade metamorphic and plutonic rocks which are not part of the Olympic range, and are identified as having a "northern" source. These deposits consist of gravel and cobbles in a sandy to clayey matrix, and include the above mentioned high-grade metamorphic rock clasts. Based on review of nearby well logs, the glacial till and outwash deposits extend over 100 feet bgs. 4.2 Site Surface Conditions At the time of our field investigation, the site was bordered by forested land to the north and west, Highway 101 to the east, and North Cedardale Lane to the south. The site gently descended to the east/northeast in a terrace like manner and was occupied by the existing residential structure, an attached garage/shop building, an attached wood- and concrete-framed deck, concrete hardscaping (sidewalks), a gravel-surfaced driveway, and landscaping features (grass, isolated shrubs, and trees). The east margin of the site was forested and exhibited steeper gradients that were visually estimated to be up to 1 HA V(horizontal:vertical). The area adjacent to the north portion of the structure (below the overlying deck) contained a deteriorating tree log placed in an east-west orientation and that log was retaining a localized soil-surfaced ascending slope that led to the structure's north continuous wall foundation. Small gaps (voids) were present below the concrete foundation near the northeast corner of the structure. The area directly east of the deck/patio was surfaced with bark dust and was steeply descending to the east/northeast near the northeast comer of the Polenz, Michael, Hughes, J.F., Carson, R.J.,Walsh,T.J., Clark, K.P., Perry, B.B., Davies, Nigel, and Miller, B.A., 2012. Geologic map of the Hoodsport 7.5-minute quadrangle,Mason County,Washington:Washington Division of Geology and Earth Resources, Open File Report 2011-3,scale 1:24,000. Carlson Geotechnical Page 2 of 11 Baker Residence Mason County, Washington CGT Project Number G2406096 April 3, 2024 structure. Site layout and surface conditions at the time of our field investigation are shown on the attached Site Plan (Figure 2) and Site Photographs (Figure 3). 5.0 FIELD INVESTIGATION 5.1 Hand Auger Borings CGT advanced three hand auger borings (HA-1 through HA-3) at the site on March 15, 2024, to practical refusal depths of up to about 6% feet bgs. Practical refusal occurs when occurs when the auger cannot be advanced further, often due to coarse gravel particles in the soil. The approximate locations of the borings are shown on the attached Site Plan, Figure 2. The borings were located in the field using approximate measurements from existing site features (e.g. corners of residential structure) shown on Figure 2. The borings were advanced using a manual, 3-inch diameter hand auger provided and operated by CGT. Upon completion, the borings were loosely backfilled with the spoils. 5.2 Wildcat Dynamic Cone Penetrometer Tests In conjunction with each hand auger boring, we advanced dynamic cone penetrometer tests to practical refusal depths of up to about 7% feet bgs. The dynamic cone penetrometer tests were performed using a Wildcat Dynamic Cone Penetrometer (WDCP) provided and operated by CGT. The WDCP test is described on the attached Exploration Key, Figure 4. Results of the WDCP tests are shown on the respective boring logs. 5.3 Soil Classification &Sampling A qualified member of CGT's geotechnical staff logged the soils observed within the borings in general accordance with the Visual-Manual Procedure outlined in ASTM D2488 and collected representative, disturbed (grab) samples of the materials encountered. An explanation of this procedure is presented on the attached Soil Classification Criteria&Terminology, Figure 5. The soil samples were stored in sealable plastic bags and transported to our laboratory for further examination and testing. Our geotechnical staff visually examined all samples returned to our laboratory in order to refine the field classifications. 6.0 LABORATORY TESTING Laboratory testing of soil samples collected in the field was performed in our laboratory to refine our field classifications and determine in-situ parameters of the on-site soils. Laboratory testing included four moisture content determinations(ASTM D2216) and one plasticity (Atterberg limits) test(ASTM D4318). Results of the laboratory tests are shown on the Exploration Logs, Figures 6 through 8. 7.0 SUBSURFACE CONDITIONS Logs of the explorations are attached as Figures 6 through 8. Surface elevations indicated on the logs were determined relative to a temporary elevation benchmark (finished floor elevation of the existing residential structure). The benchmark was assigned an arbitrary elevation of 100 feet. Elevations shown on the logs should be considered approximate. The following sections describe subsurface conditions encountered in the borings. Carlson Geotechnical Page 3 of 11 Baker Residence Mason County, Washington CGT Project Number G2406096 April3, 2024 7.1 Soils Organic Soil (OL): Organic soil was encountered at the surface of HA-1 and extended to a depth of about'/z- foot bgs. The organic soil was typically brown, moist, exhibited low plasticity and contained abundant rootlets and trace rounded gravel up to 2-inches in diameter. Silt to Silt with Gravel Fill (ML Fill): Silt to silt with gravel fill was encountered at the surface of HA-2 and HA-3 and extended to depths of about 4'/2 to 6 feet bgs, respectively. This soil was typically brown, most, exhibited low to medium plasticity and contained a varying amount of subrounded gravel up to 3-inches in diameter. Elastic Silt to Silty Gravel (MH, GM): Underlying the organic soil in HA-1 and the fill soils in HA-2 and HA-3 was native, elastic silt to silty gravel. This soil ranged from medium stiff/dense to stiff, brown and gray mottled, moist, exhibited medium plasticity fines and contained subrounded gravel up to 2-inches in diameter. This soil extended to the full depth explored, about 3%to 63/4 feet bgs, where practical refusal was encountered on coarse rock fragment(s). 7.2 Groundwater We did not encounter groundwater within the depths explored at the site on March 15, 2024. To determine approximate regional groundwater levels in the area, we researched well logs available on the Washington Department of Ecology (WDE)z website for wells located within Section 13, Township 22 North, Range 4 West, Willamette Meridian. Our review indicated that groundwater levels in the area generally ranged from about 66 to 89 feet bgs. Deeper water zones were reported at depths of about 122 feet bgs. It should be noted groundwater levels vary with local topography. In addition, the groundwater levels reported on the OWRD logs often reflect the purpose of the well, so water well logs may only report deeper, confined groundwater, while geotechnical or environmental borings will often report any groundwater encountered, including shallow, unconfined groundwater. Therefore, the levels reported on the WDE well logs referenced above are considered generally indicative of local water levels and may not reflect actual groundwater levels at the project site. We anticipate that groundwater levels will fluctuate due to seasonal and annual variations in precipitation, changes in site utilization, or other factors. 8.0 SEISMIC CONSIDERATIONS 8.1 Seismic Design The 2021 Washington Residential Specialty Code (2021 WRSC) requires the determination of seismic site class be determined in accordance with Chapter 20 of the American Society of Civil Engineers Minimum Design Loads for Buildings and Other Structures (ASCE 7-16). We have assigned the site as Site Class D ("Stiff Soil") based on geologic mapping and subsurface conditions encountered during our investigation. Seismic ground motion values were determined in accordance with Section R301.2.2 of the 2021 WRSC using the Seismic Hazards by Location calculator on the ATC website 3. The Seismic Design Category was determined from Table R301.2.2.1.1 of the 2021 WRSC. The site Latitude 47.3991240 North and Longitude 2 Washington State Department of Ecology, 2023. Well Log Records, accessed March 2024, from web site: https//fortress wa gov/ecv/waterresources/map/WCLSWebMao/textsearch aspx 3 Applied Technology Council (ATC), 2024. USGS seismic design parameters determined using "Seismic Hazards by Location," accessed March 2024,from the ATC website https:Hhazards.atcouncii.oro/. Carlson Geotechnical Page 4 of 11 Baker Residence Mason County, Washington CGT Project Number G2406096 April 3, 2024 123.143284'West were input as the site location. The following table shows the recommended seismic design parameters for the site. Table 1 Seismic Ground Motion Values Parameter Value Mapped Acceleration Parameters Spectral Acceleration, 0.2 second(Ss) 1.564g Spectral Acceleration, 1.0 second(Si) 0.587g Coefficients Site Coefficient,0.2 second(FA) 1.000 (Site Class D) Site Coefficient, 1.0 second(Fv)1 1.713 Adjusted MCE Spectral MCE Spectral Acceleration,0.2 second(SMs) 1.564g Response Parameters MCE Spectral Acceleration,1.0 second(SM1) 1.006g Design Spectral Acceleration,0.2 second(SDs) 1.043g Design Spectral Response Accelerations Design Spectral Acceleration,1.0 second(SD1) 0.671g Seismic Design Category(Risk Category ll) D Value determined from 2021 IBC-WA Table R301.2.2.1.1. 8.2 Seismic Hazards 8.2.1 Liquefaction In general, liquefaction occurs when deposits of loose/soft, saturated, cohesionless soils, generally sands and silts, are subjected to strong earthquake shaking. If these deposits cannot drain quickly enough, pore water pressures can increase, approaching the value of the overburden pressure. The shear strength of a cohesionless soil is directly proportional to the effective stress, which is equal to the difference between the overburden pressure and the pore water pressure. When the pore water pressure increases to the value of the overburden pressure, the shear strength of the soil approaches zero, and the soil can liquefy. The liquefied soils can undergo rapid consolidation or, if unconfined, can flow as a liquid. Structures supported by the liquefied soils can experience rapid, excessive settlement, shearing, or even catastrophic failure. For fine-grained soils, susceptibility to liquefaction is evaluated based on penetration resistance and plasticity, among other characteristics. Criteria for identifying non-liquefiable, fine-grained soils are constantly evolving. Current practice to identify non-liquefiable, fine-grained soils is based on moisture content and plasticity characteristics of the soils4,5,e The susceptibility of sands, gravels, and sand-gravel mixtures to liquefaction is typically assessed based on penetration resistance, as measured using SPTs, CPTs, or Becker Hammer Penetration tests (BPTs). Based on the lack of saturated conditions, the onsite silty soils (MH, GM) are considered non-liquefiable within the depths explored. The Washington State Department of Natural Resources Geologic Information Portal? shows a low susceptibility to liquefaction for the site and immediate vicinity. Based on the review of ° Seed, R.B. et al., 2003. Recent Advances in Soil Liquefaction Engineering: A Unified and Consistent Framework. Earthquake Engineering Research Center Report No. EERC 2003-06. 5 Bray, Jonathan D., Sancio, Rodolfo B., et al., 2006. Liquefaction Susceptibility of Fine-Grained Soils,Journal of Geotechnical and Geoenvironmental Engineering,Volume 132, Issue 9,September 2006. 6 Idriss, I.M., Boulanger, R.W.,2008.Soil Liquefaction During Earthquakes, Earthquakes Engineering Research Institute Monograph MNO-12. Washington State Department of Natural Resources, 2024. Washington Geologic Information Portal, accessed March 2024, from WA DNR website: hftps://geoloovportal.dnr.wa.gov/. Carlson Geotechnical Page 5 of 11 Baker Residence Mason County, Washington CGT Project Number G2406096 April 3, 2024 geologic mapping, and anticipated depths to the groundwater level, we do not anticipate liquefiable conditions are present at depths below those explored as part of this assignment. 8.2.2 Slope Instability We did not observe any obvious signs of past or on-going slope instability at the site. Review of the Washington State Department of Natural Resources Geologic Information Portal shows no historic or prehistoric landslides at or in the immediate vicinity of the site. Given the lack of evidence of previous landslides in the vicinity, and the 60-foot setback of the residential structure from the steep slope along the east margin of the site, the risk of seismically-induced slope instability impacting the project area (i.e. existing residential structure) is considered low. 8.2.3 Surface Rupture 8.2.3.1 Faultin Although the site is situated in a region of the country with known active faults and historic seismic activity, no known faults exist on or immediately adjacent to the site. Therefore, the risk of surface rupture at the site due to faulting is considered low. 8.2.3.2 Lateral Spread Surface rupture due to lateral spread can occur on sites underlain by liquefiable soils that are located on or immediately adjacent to slopes steeper than about 3 degrees (20H:1V), and/or adjacent to a free face, such as a stream bank or the shore of an open body of water. During lateral spread, the materials overlying the liquefied soils are subject to lateral movement downslope or toward the free face. Based on the non- liquefiable nature of the soils, the risk of damage associated with lateral spread is negligible. 9.0 CONCLUSIONS As indicated above, we encountered undocumented fill within explorations HA-2 and HA-3 in close proximity to the affected portion of the residential structure. The existing fill extended to depths of about 4% to 6 feet bgs and consisted of silt to silt with gravel fill (ML Fill). SPT N60 values, correlated from the WDCP tests, within the fill material were highly variable, ranging from 0 to 10. Due to its variable relative densities, we conclude the existing silt fill was not compacted in accordance with typical code requirements for structural fill. Based on our explorations, analyses, and review of geologic mapping, it is our opinion that the voluntary foundation retrofitting and improvements, as described in Section 2.0 of this report, may proceed as currently proposed. Site subsurface conditions are conducive for installation of the specialty piling systems (push piers and driven pin piles) proposed at this site. Geotechnical recommendations for push piers and driven pin piles are presented later in this report. 10.0 RECOMMENDATIONS The following paragraphs present specific geotechnical recommendations for design and construction of the proposed project. The recommendations presented in this report are based on the information provided to us, results of the field investigation, laboratory data, and professional judgment. CGT has observed only a small portion of the pertinent subsurface conditions. The recommendations are based on the assumption that the subsurface conditions do not deviate appreciably from those found during the field investigation. CGT Carlson Geotechnical Page 6 of 11 Baker Residence Mason County, Washington CGT Project Number G2406096 April3, 2024 should be consulted for further recommendations if variations and/or undesirable geotechnical conditions are encountered at the site. 10.1 Foundation Underpinning—Vertical Support 10.1.1 Push Piers 10.1.1.1 Overview Push piers consist of high quality steel tube sections hydraulically pushed into the ground surface until achieving the specified design installation pressure. Push piers are proprietary foundation systems. The specialty pile contractor, in coordination with the project structural engineer, typically develops design plans for push pier supported foundations and establishes pushing termination criteria. 10.1.1.2 Soil Strength Parameters We have provided recommended values for soil parameters, including drained friction angle (('), effective cohesion (c'), total unit weight (YA and undrained shear strength (S„), for use in push pier design in the following table. The parameters provided below were based on the results of the borings, laboratory testing, published correlations, and our experience with similar soils. In the event additional geotechnical (soil) parameters are required for design, the geotechnical engineer should be consulted. Table 2 Recommended Soil Strength Parameters for Use in Push Pier Design Soil Shear Strength Parameter2 Depth Layer (feet) Description Soil Type �' c' Tr SU (degrees) (psf) (pcf) (psf) 1 0 to 6 Undocumented Fill(ML Fill) Cohesionless Neglect contribution 2 6+ Medium stiffldense to better,Elastic Silt and Silty Cohesionless 36 0 115 0 Gravel (MH, GM) 1 Relative to existing grades along the exterior of the perimeter continuous wall footings to be underpinned. 2 If additional soil parameters are required to facilitate design,the geotechnical engineer should be consulted. 10.1.1.3 Installation Depth Consideration Generally speaking, the push piers should be installed to penetrate existing fill materials and to achieve the pushing termination criteria outlined by the pier designer. For this site, we recommend push piers be installed a minimum of 6 feet below the current grade adjacent to the foundation to be underpinned. 10.1.1.4 Load Testinq The load test program, including actual number of load tests, load increments used during testing, and duration, should be defined by the pier designer. As a general guideline, push pier load testing may be conducted in general accordance with ASTM D1143 — Pile Under Static Axial Compressive Loads (quick method). We recommend push pier load testing be conducted on at least one test pier. The test pier(s) should be loaded to at least two times the allowable capacity. Since failure of the test or reaction pier(s) may occur, we recommend that test pier(s) not be used for service piers. All push pier load test(s) should be conducted under the technical supervision of the geotechnical engineer. The test pier(s) should be installed using the same equipment and procedures that will be used to install service piers. The geotechnical engineer or his representative should witness the installation of both test and service pier(s). Total allowable pile movements shall be limited to that indicated by the project structural engineer. Carlson Geotechnical Page 7 of 11 Baker Residence Mason County, Washington CGT Project Number G2406096 April 3, 2024 10.1.2 Driven Pin Piles 10.1.2.1 Overview Pin piles commonly consist of Schedule 40 or 80, A-53, steel pipes, 2-to 6-inches in diameter, driven into the ground to refusal using a compressed air hammer or other installation techniques. The terminal driving resistance will depend on the size (diameter) of the pile and the pile driving equipment used. Final terminal driving criteria is confirmed in the field by the geotechnical engineer or his representative using hammer specifications (weight, blows per minute, and efficiency) provided by the pile contractor's engineer. 10.1.2.2 Design Considerations When driven to refusal, pin piles typically exhibit allowable axial pile capacities ranging from 6 to 25 kips. Subject to review of the structural engineer, allowable axial pile capacities should be confirmed in the field with in-place load test(s) as detailed below. The following table presents allowable axial capacities of 2, 3, 4, and 6-inch-diameter, pin piles that are driven to practical refusal using typical hammer equipment. Table 3 Allowable Axial Capacities of Pin Piles Driven to Refusal Pin Pile Diameter(inches) Allowable Axial Capacity(kips)* 2 6 3 12 4 18 6 25 *The allowable capacities presented herein are based on experience with similar projects and assume the hammer(s) selected to drive the piles delivers sufficient energy to achieve these loads. A wave equation analysis of pile driving (WEAP) is typically performed to finalize design axial capacities once the hammer(s)have been selected. 10.1.2.3 Installation Depth Consideration Pin piles should be driven to practical refusal (final driving criteria) specified by the pile contractor's engineer. For this site, we recommend piles be driven a minimum of 6 feet relative to existing site grades. It is anticipated that piling will need to penetrate the native sandy soils several to tens of feet in order to develop resistance and achieve design load capacities. 10.1.2.4 Lateral Capacity In general, pin piles do not provide much resistance to lateral loading due to their relatively small cross- sectional diameter. Therefore, pin piles are typically driven into the ground at an angle (i.e. battered) in order to develop required lateral capacities through the horizontal component of the pin pile capacity. If battered piles are considered, the presence of the nearby site features(e.g. utilities) should be assessed. 10.1.2.5 Load Testing As a general guideline, pin pile load testing may be conducted in general accordance with ASTM D1143 — Pile Under Static Axial Compressive Loads (quick method). We recommend pin pile load testing be conducted on at least one test pile. The test pile(s) should be loaded to at least two times the allowable capacity. Since failure of the test or reaction pile(s) may occur, we recommend that test pile(s) not be used for service piles. All pin pile load test(s) should be conducted under the technical supervision of the geotechnical engineer. The test pile(s) should be installed using the same equipment and procedures that will be used to install service piles. The geotechnical engineer or his representative should witness the Carlson Geotechnical Page 8 of 11 Baker Residence Mason County, Washington CGT Project Number G2406096 April 3, 2024 installation of both test and service pile(s). Total allowable pile movements shall be limited to that indicated by the project structural engineer. 10.2 Foundation Underpinning—Lateral Support A maximum passive (equivalent fluid) earth pressure of 100 pounds per cubic foot (pcf) is recommended for design of pier-supported concrete footings confined by the existing silt fill (ML Fill), the native silty soils (MH, GM), or imported granular structural fill that is properly placed and compacted during construction. Development of passive resistance assumes that some lateral movement of the foundation is allowed into the surrounding soil, thereby developing a passive soil wedge. The recommended earth pressure was computed using a factor of safety of 1'/2, which is appropriate due to the amount of movement required to develop full passive resistance. In order to develop the above capacity, the following should be understood: 1. Concrete must be poured neat in excavations or the grade-beam foundations must be backfilled with imported granular structural fill, 2. The adjacent grade must be level, 3. The static ground water level must remain below the base of the footings throughout the year. 4. Adjacent floor slabs, pavements, or the upper 18-inch-depth of adjacent, unpaved areas should not be considered when calculating passive resistance. 10.3 Imported Granular Structural Fill (if required) Imported granular structural fill should consist of angular pit or quarry run rock, crushed rock, or crushed gravel that is fairly well graded between coarse and fine particle sizes. The granular fill should contain no organic matter, debris, or particles larger than 1%2 inches, and have less than 5 percent material passing the U.S. Standard No. 200 Sieve. The percentage of fines can be increased to 12 percent of the material passing the U.S. Standard No. 200 Sieve if placed during dry weather, and provided the fill material is moisture-conditioned, as necessary, for proper compaction. Imported granular fill material should be placed in maximum 12-inch thick loose lifts and compacted to not less than 90 percent of the material's maximum dry density, as determined in general accordance with ASTM D1557 (Modified Proctor). 11.0 LIMITATIONS &CLOSURE We have prepared this report for use by the client and other members of the design and construction team for the proposed development. The opinions and recommendations contained within this report are forwarded to assist in the planning and design process and are not intended to be, nor should they be construed as, a warranty of subsurface conditions. We have made observations based on our explorations that indicate the soil conditions at only those specific locations and only to the depths penetrated. These observations do not necessarily reflect soil types, strata thickness, or water level variations that may exist between or away from our explorations. If subsurface conditions vary from those encountered in our site explorations, CGT should be alerted to the change in conditions so that we may provide additional geotechnical recommendations, if necessary. Observation by experienced geotechnical personnel should be considered an integral part of the construction process. The owner/developer is responsible for ensuring that the project designers and contractors implement our recommendations. When the design has been finalized, prior to releasing bid packets to contractors, we recommend that the design drawings and specifications be reviewed by our firm to see that our Carlson Geotechnical Page 9 of 11 Baker Residence Mason County, Washington CGT Project Number G2406096 April 3, 2024 recommendations have been interpreted and implemented as intended. If design changes are made, we request that we be retained to review our conclusions and recommendations and to provide a written modification or verification. Design review and construction phase testing and observation services are beyond the scope of our current assignment, but will be provided for an additional fee. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractor's methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. Geotechnical engineering and the geologic sciences are characterized by a degree of uncertainty... Professional judgments presented in this report are based on our understanding of the proposed construction, familiarity with similar projects in the area, and on general experience. Within the limitations of scope, schedule, and budget, our services have been executed in accordance with the generally accepted practices in this area at the time this report was prepared; no warranty, expressed or implied, is made. This report is subject to review and should not be relied upon after a period of three years. Should you have any questions regarding the recommendations or opinions presented in this report, please contact us at(503) 601-8250. Sincerely, S-A" . CARLSON GEOTECHNICAL \�`'1AC-C ^ 4 ` r EXPiPIS Ariana Tenold, G.I.T. Brad M. Wilcox, P.E. Geotechnical Project Manager Principal Geotechnical Engineer atenold(a)carlsontestino.com bwilcox(dcarlsontestina.com Note: The observations of existing conditions at the time of our site visit were based solely on visual methods. Our reports pertain to the locations observed at the time of our visit only. Information contained herein is not to be reproduced, except in full, without prior authorization from this office. The information contained in this report is provided subject to all terms and conditions of CGTs General Conditions in effect at the time this report is prepared. No party other than those to whom CGT has distributed this report shall be entitled to use or rely upon the information contained in this document. Carlson Geotechnical Page 10 of 11 Baker Residence Mason County, Washington CGT Project Number G2406096 April 3, 2024 ATTACHMENTS: Site Location, Figure 1 Site Plan, Figure 2 Site Photographs, Figure 3 Exploration Key, Figure 4 Soil Classification & Criteria, Figure 5 Exploration Logs, Figure 6 through 8 Doc ID:G:\GEOTECH\PROJECTS\2024 Projects\G2406096-Baker Residence\G2406096-GEO\008-Deliverables\Report\G2406096 Geotechn ical I nvestigation.docx Carlson Geotechnical Page 11 of 11 BAKER RESIDENCE-MASON COUNTY, WASHINGTON FIGURE 1 Project Number G2406096 Site Location i f f' I" y ' t1. ff \ f Site Location r r I j USGS Topographic base map created with The National Map, 2024, at Latitude:47.39912' North P y https://apps.nationaImap.gov/viewer/ Longitude: 123.14328'West 1 Inch=2,000 feet 503.601-6250 Township 22 North, Range 4 West,Section 13,Willamette Meridian 0 2000 4000 DMW byAET BAKER RESIDENCE- MASON COUNTY, WASHINGTON FIGURE 2 Project Number G2406096 Site Plan �. 3 _1 t �y� 3 � I i e _ r - � 3y t EL GEND HA-1 Hand auger boring&WDCP test.Depth of fill Orientation of site photographs shown on Figure 3 indicated in(). Elevation benchmark-Assumed 100-foot elevation at B� the finished floor elevation of the existing building p.R O NOTES:2023 aerial photograph from Mason County Mapping System C T72 1 Inch=25 Feet https:l/gis.masoncountywa.gov/mason.All locations are approximate. 503-6® 0 25 50 i Dafted hy.AET BAKER RESIDENCE- MASON COUNTY, WASHINGTON FIGURE 3 Project Number G2406096 Site Photographs .s Photograph 1 Photograph 2 ze 5 : yAN •.b -"tee` _ _ `Y'S..t,`,. 5�0� �§�*'a �--y }. .7R1 * Photograph 3 Photograph 4 O �� See Figure 2 for approximate photograph locations and directions. Photographs were taken at the time of our fieldwork. 503-601-8250 BAKER RESIDENCE-MASON COUNTY, WASHINGTON FIGURE 4 Project Number G2406096 Exploration Key PAL �L- Atterberg limits (plasticity) test results (ASTM D4318): PL= Plastic Limit, LL= Liquid Limit, and MC= Moisture Content MC (ASTM D2216) ❑FINES CONTENT(%) Percentage passing the U.S.Standard No.200 Sieve(ASTM D1140) SAMPLING ij GRAB Grab sample BULK Bulk sample Standard Penetration Test(SPT) consists of driving a 2-inch, outside-diameter, split-spoon sampler into the undis- turbed formation with repeated blows of a 140-pound, hammer falling a vertical distance of 30 inches (ASTM D1586). SPT The number of blows(N-value)required to drive the sampler the last 12 inches of an 18-inch sample interval is used to characterize the soil consistency or relative density. The drill rig was equipped with an cat-head or automatic hammer to conduct the SPTs. The observed N-values,hammer efficiency,and N60 are noted on the boring logs. Modified California sampling consists of 3-inch, outside-diameter, split-spoon sampler(ASTM D3550)driven similarly to e MC the SPT sampling method described above. A sampler diameter correction factor of 0.44 is applied to calculate the equivalent SPT N60 value per Lacroix and Horn, 1973. CORE Rock Coring interval ' SH Shelby Tube is a 3-inch, inner-diameter, thin-walled, steel tube push sampler(ASTM D1587) used to collect relatively undisturbed samples of fine-grained soils. Wildcat Dynamic Cone Penetrometer (WDCP) test consists of driving 1.1-inch diameter, steel rods with a 1.4-inch WDCP diameter, cone tip into the ground using a 35-pound drop hammer with a 15-inch free-fall height. The number of blows required to drive the steel rods is recorded for each 10 centimeters(3.94 inches)of penetration. The blow count for each interval is then converted to the corresponding SPT N60 values. Dynamic Cone Penetrometer (DCP) test consists of driving a 20-millimeter diameter, hardened steel cone on 16- DCP millimeter diameter steel rods into the ground using a 10-kilogram drop hammer with a 460-millimeter free-fall height. The depth of penetration in millimeters is recorded for each drop of the hammer. POCKET Pocket Penetrometer test is a hand-held instrument that provides an approximation of the unconfined compressive PEN.(tsf) strength in tons per square foot(tsf)of cohesive,fine-grained soils. CONTACTS Observed(measured)contact between soil or rock units. ———- Inferred(approximate)contact between soil or rock units. Transitional(gradational)contact between soil or rock units. ADDITIONAL NOTATIONS Italics Notes drilling action or digging effort {Braces} Interpretation of material origin/geologic formation (e.g.{Base Rock}or{Columbia River Basalt}) P � All measurements are approximate. 503-601-8250 BAKER RESIDENCE-MASON COUNTY, WASHINGTON FIGURE 5 Project Number G2406096 Soil Classification Classification of Terms and Content Grain Size U.S.Standard Steve NAME: Group Name and Symbol Fines <#200(0.075 mm) Relative Density or Consistency Fine #200-#40(0.425 mm) Color Sand Medium #40-#10(2 mm) Moisture Content Coarse #10-#4(4.75 mm) Plasticity Other Constituents Gravel Fine #4- inch inch i Other.Grain Shape,Approximate Gradation Coarse 0.75 nch-3 inches Organics,Cement,Structure,Odor,etc. Cobbles 3 to 12 inches Geologic Name or Formation Boulders >12 inches Coarse-Grained(Granular)Soils Relative Density Minor Constituents SPT N60 Value Density Perby Volume nt Descriptor Example 0-4 Very Loose 0-5% 'Trace"as part of soil description "trace silt" 4-10 Loose 10-30 Medium Dense 5-15% "With"as part of group name "POORLY GRADED SAND WITH SILT" 30-50 Dense 15-49% Modifier to group name "SILTY SAND" >50 Very Dense Fine-Grained(Cohesive)Soils SPT Torvane tsf Pocket Pen tsf Consistency Manual Penetration Test Minor Constituents N60-Value Shear Strength Unconfined <2 <0.13 <0.25 Very Soft Thumb penetrates more than 1 inch Percent 2-4 0.13-0.25 0,25-0.50 Soft Thumb penetrates about 1 inch by Volume Descriptor Example 4-8 0.25-0.50 0.50-1.00 Medium Stiff Thumb penetrates about%,inch 0-5% "Trace"as part of soil description 'trace fine-grained sand" 8-15 0.50-1.00 1.00-2.00 Stiff Thumb penetrates less than Y4 inch 5-15% "Some"as part of soil description "some fine-grained sand" 15-30 1.00-2.00 2.00-4.00 Very Stiff Readily indented by thumbnail 15-30% "With"as part of group name "SILT WITH SAND" >30 >2.00 >4.00 Hard Difficult to indent by thumbnail 30-49/o Modifier to group name "SANDY SILT" Moisture Content Structure Dry: Absence of moisture,dusty,dry to the touch Stratified:Alternating layers of material or color>6 mm thick Moist Leaves moisture on hand Laminated: Alternating layers<6 mm thick Wet: Visible free water,likely from below water table Fissured: Breaks along definite fracture planes Plasticity Dry Strength Dilatancy Toughness Slickensided: Striated,polished,or glossy fracture planes ML Non to Low Non to Low Slow to Rapid Low,can't roll Blocky: Cohesive soil that can be broken down into small angular lumps which resist further breakdown CL Low to Medium Medium to High None to Slow Medium MH Medium to High Low to Medium None to Slow Low to Medium Lenses: Has small pockets of different soils,note thickness CH Medium to High High to Very High None High Homogeneous:Same color and appearance throughout Visual-Manual Classification Major Divisions Group Typical Names Symbols Clean GW Well-graded gravels and gravel/sand mixtures,little or no fines Coarse Gravels:50%or more Gravels GP Poorly-graded gravels and gravel/sand mixtures,little or no fines Grained retained on the No.4 sieve Gravels GM Silty gravels,gravel/sandisilt mixtures Soils: with Fines GC Clayey gravels,gravel/sand/clay mixtures More than 50%retained Clean SW Well-graded sands and gravelly sands,little or no fines Sands:More than Sands SP Poori raded sands and ravel) sands,little or no fines on No.200 50%passing the y� gravelly sieve No.4 sieve Sands SM Silty sands,sand/sift mixtures with Fines SC Clayey sands,sand/clay mixtures ML Inorganic silts,rock flour,clayey silts Sift S Fin Soils: Low Plasticity and Clayslasticity Fines CL Inorganic clays of low to medium plasticity,gravelly clays,sandy clays,lean clays Soils: 50%or more OL Organic soil of low plasticity Passes No. MH Inorganic sifts,clayey silts High Plasticity Fines 200 Sieve Sift and Clays CH Inorganic clays of high plasticity,fat clays OH Organic soil of medium to high plasticity Highly Organic Soils PT Peat,muck,and other highly organic soils R References: ASTM D2487 Standard Practice for Classification of Soils for Engineering Purposes(Unified Soil Classification System) ASTM D2488 Standard Practice for Description and Identification of Soils(Visual-Manual Procedure) sas-Sol-azso Terzaghi, K., and Peck, R.B., 1948, Soil Mechanics in Engineering Practice,John Wiley&Sons. GPR _ Carlson Geotechnical FIGURE 6 A Division of Carlson Testing, Inc. www.carlsontesting.com Boring HA-1 PAGE 1 OF 1 CLIENT TerraFirma Foundation Systems PROJECT NAME Baker Residence PROJECT NUMBER G2406096 PROJECT LOCATION 70 North Cedardale Lane-Mason County,Washingt n DATE STARTED 3/15/24 GROUND ELEVATION 93 ft ELEVATION DATUM See Figure 2 WEATHER Sunny SURFACE Soil LOGGED BY BMW REVIEWED BY BMW DRILLING CONTRACTOR CGT SEEPAGE — EQUIPMENT Manual Hand Auger&WDCP GROUNDWATER DURING DRILLING -- DRILLING METHOD 3 inch diameter hand auger GROUNDWATER AFTER DRILLING — O w w o Z A WDCP N60 VALUE A a w 0.0 MATERIAL DESCRIPTION p o L g >(� p Q w w Z a > QJ o_ Z Lu o O� Y" p� MC p w O O O Q Z w Z O � ❑FINES CONTENT(%)❑ ix of 0 0 20 40 60 80100 co Of a p ORGANIC SOIL:Brown,moist,abundant rootlets 1 OL with trace rounded gravel up to 2-inches in diameter. 1 ELASTIC SILT:Soft,brown,moist,medium 92 plasticity,with trace rounded gravel up to 1-inch in 0 diameter. 0 1 MH 2 1 SRAE 100 3 1 ss: 5 Medium stiff below 2'/2 feet bgs. 5 90 Increased gravel content below 3 feet bgs. 2 4 •Boring terminated at 3%feet bgs due to practical refusal on coarse-grained particles. 4 16 •No groundwater or caving encountered. •Boring loosely backfilled with excavated material 25 upon completion. 88 Uj w a m a w F- LL a d' Q N a 86 a c7 ai 0 0 J F- LL a a U g r 0 84 r a 0 J a x w r 0 GQ•R O Carlson Geotechnical FIGURE 7 A Division of Carlson Testing, Inc. Boring HA-2 www.cadsontesting.com PAGE 1 OF 1 CLIENT TerraFirma Foundation Systems PROJECT NAME Baker Residence PROJECT NUMBER G2406096 PROJECT LOCATION 70 North Cedardale Lane-Mason County,Washington DATE STARTED 3115/24 GROUND ELEVATION 95.5 ft ELEVATION DATUM See Figure 2 WEATHER Sunny SURFACE Soil LOGGED BY BMW REVIEWED BY BMW DRILLING CONTRACTOR CGT SEEPAGE — EQUIPMENT Manual Hand Auger&WDCP GROUNDWATER DURING DRILLING -- DRILLING METHOD 3 inch diameter hand auger GROUNDWATER AFTER DRILLING — O w Wa o Z A WDCP N60 VALUE A O U g ¢ o r W w ~ o-p U) MATERIAL DESCRIPTION o ate.i _j 2 >0 �¢ W 2 Z 0 Pi•_ !;L a-+ a Z W" aZ) O� Yv D'a MC o W O O O Q Z W Z U ❑FINES CONTENT(%)❑ co rr a o 0 1 10 20 40 60 80 100 SILT WITH GRAVEL FILL:Brown,moist,low 1 plasticity,with subrounded gravel up to 3-inches in diameter. 1 1 1 94 2 2 3 ML 6 FILL 7 100 3 34 92 4 3 4 3 2 ELASTIC SILT:Soft to medium stiff,brown and gray mottled,moist,medium plasticity some 3 35 54 subrounded gravel up to 1-inch in diameter. 8 90 15 w MH Stiff to very stiff below 5%feet bgs. a 25 m 6 0 w < Q Q N V • Boring terminated at 6Y:feet bgs due to practical refusal on coarse-grained particles. °0 88 • No groundwater or caving encountered. • Boring loosely backfilled with excavated material upon completion. 0 0 a U 2 r 3 z 0 a ° 86 a x w r . U GP'R O Carlson Geotechnical FIGURE 8 ® A Division of Carlson Testing, Inc. Boring HA-3 www.cadsontesting.com PAGE 1 OF 1 CLIENT TerraFirma Foundation Systems PROJECT NAME Baker Residence PROJECT NUMBER G2406096 PROJECT LOCATION 70 North Cedardale Lane-Mason County,Washingt n DATE STARTED 3/15/24 GROUND ELEVATION 99.5 ft ELEVATION DATUM See Figure 2 WEATHER Sunny SURFACE Soil LOGGED BY BMW REVIEWED BY BMW DRILLING CONTRACTOR CGT SEEPAGE — EQUIPMENT Manual Hand Auger&WDCP GROUNDWATER DURING DRILLING — DRILLING METHOD 3 inch diameter hand auger GROUNDWATER AFTER DRILLING — O w a o Z A WDCP N60 VALUE A m w w =C� ~m wp v �� �-c PL LL Q a 0 m MATERIAL DESCRIPTION p o g >C3 p Q w w z Q I� l >" Q_j a Z Lu— ap OS > Y" p' MC w p w O O O Q Z w Z O ❑FINES CONTENT(%)❑ m G✓ o p 0 1 10 20 40 60 80100 SILT FILL:Brown,moist,low to medium 3 plasticity,trace subrounded gravel up to 1-inch in diameter. 3 3 3 98 3 2 3 3 10 10 ML FILL RA 6 96 1 100 3 2a 3 4 2 1 0 Moist to wet below 5 feet bgs. 2 94 4 L < 3 m 6 SILTY GRAVEL:Medium dense,brown to gray 4 LL mottled,moist, rounded,up to 2-inches in GM diameter,with medium plasticity fines. 16 0 N 11 Q •Boring terminated at 6'/.feet bgs due to practical 4 refusal on coarse-grained particles. 16 °0 92 •No groundwater or caving encountered. •Boring loosely backfilled with excavated material 25 upon completion. 0-1 a U x r z ° r a ° 90 J a x w r U