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Home My WebLink AboutGEO2023-00087 COM2023-00100 Communication Tower - COM Engineering / Geo-Tech Reports - 11/1/2023 JE6 20-Z3 - �`�4- f_&L, G0m 2623 - 06 ,00 GEOTECHNICAL ENGINEERING REPORT Proposed North Mountain Communication Tower Shelton, Mason County, Washington R L G LE I V ED Project No. 2228.01 ' U 1 2023 August 15, 2023 615 W. Alder Street Prepared for: WSH North Bay Broadcasting, LLC T 1674W., .. _ •.� �� T S�-•'+ a -1• Mot ,. _�* •-�T ./ i �._ "'^w..: ♦ � _ yam- �-'`7 - Prepared by: ZipperitU Geoprofessional Consultants 19019 36`h Ave West, Suite E I Lynnwood, WA 98036 1 Phone: 425.582.9928 1 zippergeo.com Zipp rGeo Geoprofessional Consultants Project No. 228.01 August 15, 2023 WSH North Bay Broadcasting, LLC c/o Tower Engineering Company 21907 64th Avenue West, Suite 140 Mountlake Terrace,Washington 98043 Attention: Mr. Gregory Smith Subject: Geotechnical Engineering Report Proposed North Mountain Communication Tower Shelton, Mason County, Washington Dear Mr. Smith, In accordance with your request and written authorization, Zipper Geo Associates, LLC (ZGA) has completed the geotechnical engineering report for the above-referenced project. This report presents our findings and geotechnical recommendations for project design and construction. Our work was completed in general accordance with our Proposal for Geotechnical Engineering Services (Proposal No. P19267) dated 16 July 2019 and our Supplemental Service Agreement(P19267A) dated 10 August 2023. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report,or if we may be of further service, please contact us. Sincerely, Zipper Geo Associates, LLC {W ash 81151,23 r 8115123 O =74 ��4f rc 1783 �` Qt8'1'$a��{ �h$ed GOO �fONAL I,' DAMES P. (3EORGM James P. Georgis, LG, LEG Thomas A.Jones, PE Principal Principal Copies: Addressee (1) 19019 36th Ave West, Suite E Lynnwood, WA 98036 Phone: 425.582.9928 1 zippergeo.com TABLE OF CONTENTS Page INTRODUCTION .....................................................................................................................................................1 SITECONDITIONS...................................................................................................................................................1 PROJECTUNDERSTANDING....................................................................................................................................2 SUBSURFACECONDITIONS.....................................................................................................................................2 RegionalGeology.............................................................................................................................................2 FieldExploration Procedures ..........................................................................................................................3 SoilConditions.................................................................................................................................................3 GroundwaterConditions.................................................................................................................................4 FIELDAND LABORATORY TESTING.........................................................................................................................4 Grain-Size Analyses .........................................................................................................................................4 ResistivityTest Results....................................................................................................................................4 CONCLUSIONS AND RECOMMENDATIONS.............................................................................................................5 General ..........................................................................................................................................................5 Environmental Critical Areas Considerations..................................................................................................5 SlopeStability Analysis....................................................................................................................................6 SitePreparation...............................................................................................................................................7 TemporaryErosion Control.............................................................................................................................8 PermanentErosion Control.............................................................................................................................8 Temporary and Permanent Cut Slopes ...........................................................................................................9 StructuralFill ...................................................................................................................................................9 IBC Seismic Design Parameters.....................................................................................................................11 TowerMat Foundation..................................................................................................................................11 Equipment Building Grading Considerations ................................................................................................12 Equipment Building Shallow Foundations.....................................................................................................12 Equipment Building Slab-On-Grade Concrete Floor......................................................................................13 EcologyBlock Retaining Wall ........................................................................................................................14 CLOSURE..............................................................................................................................................................14 APPENDIX A Figure 1-Site Location Map Figure 2-Site and Exploration Plan Figure 3-Site Location Aerial Photograph Figure 4-Geologic Map of the Project Area Figure 5-LiDAR Generated Topographic Map with 10 Foot Contours Figure 6-LiDAR Generated Topographic Map on Aerial Photograph with 10 Foot Contours Figure 7-LiDAR Generated Topographic Map with 10 Foot Contours and Slopes in Percent Figure 8-Cross Section from LiDAR Generated Topographic Map with 10 Foot Contours Figure 9-Results of Static Slope Stability Analysis Figure 10-Results of Pseudo-Static Slope Stability Analysis Boring Logs B-1 through B-4 Laboratory Test Results Mason County Department of Community Development Submittal Checklist for a Geotechnical Report GEOTECHNICAL ENGINEERING REPORT PROPOSED NORTH MOUNTAIN COMMUNICATION TOWER SHELTON, MASON COUNTY, WASHINGTON Project No. 2228.01 August 15, 2023 INTRODUCTION This report documents the surface and subsurface conditions encountered at the site and our geotechnical engineering recommendations for the proposed North Mountain Communication Tower Project near Shelton, Mason County, Washington. Thomas Jones, currently a principal at ZGA, was the engineer of record for the two previous geotechnical reports for the subject site listed below. • Report of Geotechnical Services, Proposed Radio Tower, North Mountain, Mason County, Washington, prepared by Zipper Zeman Associates, Inc., dated May 2, 2003. • Geotechnical Engineering Report, Proposed Radio Broadcast Tower, North Mountain, Shelton, Mason County, Washington, prepared by Terracon, dated September 14, 2009. The purpose of this study was to review updated redevelopment plans for the proposed communications tower and existing project geotechnical data, complete a site reconnaissance of existing site conditions, and prepare an updated design geotechnical report for the project. This report incorporates data from and supersedes the previous reports for this project referenced above. The project description, site conditions and our geotechnical conclusions and design recommendations are presented in the text of this report. Supporting data including figures, exploration logs, and laboratory test results are presented in Appendix A. SITE CONDITIONS ZGA completed a surficial reconnaissance of the site on July 31,2019. The conditions observed in 2019 were generally consistent with those observed during the previous site evaluations,as summarized below. The project site is located in the SE%of Section 8,T21N, RSW, on North Mountain, northwest of the town of Shelton, in Mason County,Washington. The general location of the site with respect to the USGS Vance Creek Quadrangle Map is presented on the enclosed Site Location Map, Figure 1. The project site is currently undeveloped but is surrounded by existing cellular communication and radio towers and equipment buildings, most of which are situated above the project site at the top of North Mountain. The project site is situated on the south side of the complex, about 20 feet below the top of the mountain and adjacent to an approximate 2H:1V slope that dips down from the top. A single cellular communication tower is situated west of the project site, closer to the south-dipping slopes of North Mountain. Page 1 Z• Proposed North Mountain Communication Tower i pperGeo Shelton, Mason County,Washington Geoprofessional Consultants Project No.: 2228.01 August 15, 2023 The site, as well as the slope between the project site and the top of the mountain, is essentially bare of vegetation. In the vicinity of the site, road cuts have exposed soils that appear to consist of extremely weathered residual basalt. Downslope of the site,the slopes are covered with brush and immature trees. We did not observe any surficial indications of recent slope failures at the site or on the nearby slopes in the vicinity of the site. No standing or flowing surface water was observed on or in the vicinity of the site at the time of our visits. Figure 3 presents the project site location on an aerial photograph. PROJECT UNDERSTANDING We understand that the project includes construction of a 100-foot tall self-supporting tower supported on a mat foundation, a 12-foot by 56-foot equipment shelter with shallow foundations and a slab-on-grade concrete floor, and an ecology block retaining wall. We understand that the ecology block wall will have a maximum height of about 4 feet(two blocks tall). Existing site features and the proposed development are shown on the enclosed Site and Exploration Plan, Figure 1. SUBSURFACE CONDITIONS Regional Geology The 2003 Washington State Department of Natural Resources Open File Report, OFR 2003-15, titled Geologic Map of the Shelton 1:100,000 Quadrangle, Washington, maps the project site as being underlain by Crescent Formation Basalt, flow dominated, Evcf. The Crescent Formation basalt is described as consisting primarily of lower to middle Eocene-age rock. The Geologic Map of the Project Area, Figure 4, presents an excerpt of the above-referenced map and the mapped geology in the project vicinity. According to the USDA Natural Resources Conservation Service,Soil Survey of Mason County,Washington (http://websoilsurveV.nres.usda.gov/appi),the site is mapped as being underlain by Rough mountainous land, Tebo soil material (Rd). We did not observe any intact bedrock in our explorations; therefore, it is our opinion that the soils more closely resemble the Tebo gravelly loam. The Tebo series is described as consisting of reddish-brown, well-drained upland soils. These soils were developed in place from weathered basalt or andesitic rock. According to the NRCS, this Rough mountainous land soil unit has slopes that are generally in the 30 to 70 percent range. This correlates with the LiDAR generated topographic maps that are presented on Figures 5, 6, and 7. The information presented herein is generalized for the Rough mountainous land and Tebo soils and can vary between areas of the same material based on topography, localized groundwater conditions, alterations to the land by man, and other geologic factors. Page 2 Proposed North Mountain Communication Tower Zi ppe rGeo Shelton, Mason County,Washington Geoprofessional Consultants Project No.: 2228.01 August 15, 2023 Field Exploration Procedures The site subsurface conditions were completed in April 2003 and May 2009. The subsurface conditions are described below while the interpretive logs of the explorations and laboratory test results are presented in Appendix A.The approximate exploration locations relative to an existing Verizon equipment storage building are shown on the enclosed Site and Exploration Plan, Figure 2. The subsurface exploration program conducted in 2003 consisted of completing three hollow-stem auger borings utilizing a CME-45 track-mounted drill rig while the 2009 study consisted of completing one hollow-stem auger boring utilizing a BK truck-mounted drill rig.The location and depth of the explorations were selected based upon two potential tower locations. The exploration locations were determined by measuring from existing site features with a fiberglass tape. As such, the exploration locations shown on Figure 2 should be considered accurate only to the degree implied by the measurement method. The borings were completed to depths ranging from 16% to 31% feet below the existing ground surface. Approximate ground surface elevations at the exploration locations were interpreted from a topographic map provided to us and are referenced relative to a site-specific benchmark set at elevation 100 feet at the ground surface adjacent to the northwest corner of the existing Verizon equipment storage building south of the site. A geotechnical engineer monitored the borings and logged the soil and groundwater conditions encountered. Relative soil density was determined by the Standard Penetration Test Method using a 140- pound hammer and driving a split-spoon sampler 18 inches into the soil. Representative soil samples were collected and sealed in moisture tight containers and transported to a laboratory testing. Soil types and conditions can vary between explorations. The nature and extent of variations between the explorations may not become evident until construction. If variations become apparent during construction, it may be necessary to reevaluate the recommendations of this report Soil Conditions The subsurface conditions disclosed in borings B-1 through B-3 (2003) generally consisted of medium dense,silty sandy gravel and silty gravelly sand that was interpreted to be very severely weathered basalt. In boring B-1, dense grading to very dense conditions were encountered at a depth of approximately 13 feet. In boring B-2, medium dense conditions were encountered to the full 21%2-foot depth explored. In boring B-3, dense grading to very dense conditions were encountered at a depth of approximately 12% feet. Boring B-4 (2009) was completed at an alternate location about 50 to 60 feet southeast of boring B- 2.Approximately 18 feet of very loose to loose, interlayered, silty sand with varying proportions of gravel was encountered over medium dense, interlayered, silty sand with varying proportions of gravel to the full 31%:-foot depth explored. In general, the entire site is underlain by residual soils derived from weathered basalt. Page 3 p r Proposed North Mountain Communication Tower Z i p pe fGeo Geoprofessional Consultants Project No.:2228.01 August 15, 2023 The borings were completed under the supervision of Zipper Zeman Associates and Terracon geotechnical engineers who visually inspected the soil samples, prepared logs of the borings, interpreted stratigraphy, and classified and collected the samples. The boring logs included visual classifications of the materials encountered during drilling,as well as the engineer's interpretation of the subsurface conditions between samples. The soil samples were placed in sealed plastic bags to prevent moisture loss and were sent to the laboratory for further visual observation and laboratory testing. Groundwater Conditions Groundwater seepage was not observed in the borings at the time of exploration.Given the mountaintop location of the site and the observed surface and subsurface conditions, we do not anticipate significant groundwater seepage within anticipated excavation depths. However, due to the increase in relative density with depth, the formation of shallow perched groundwater may develop during and shortly after periods of sustained wet weather. Fluctuations of the groundwater level can occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the borings were performed. Groundwater levels during construction or at other times in the life of the structure may vary from those indicated on the logs. FIELD AND LABORATORY TESTING Grain-Size Analyses Grain size distribution tests were completed on representative samples collected during the 2003 site investigation. Grain-size analysis test results are enclosed in Appendix A. Resistivity Test Results Field measurements of soil resistivity using the Wenner Four-Electrode Method were performed in during previous studies in general accordance with ASTM G 57-78.A series of soil resistivity tests was performed along a traverse line within the existing road using a Megger DET5/41) meter. The traverse line was approximately 34 feet north of the northeast corner of the Verizon equipment building located on the north side of the access road and paralleled the road in the east-west direction.The Wenner arrangement (equal electrode spacing) was used with the "a" spacing incrementally increasing from 5 to 20 feet. The resistivity values obtained represent the average resistivity of the soil to a depth equal to the pin (electrode) spacing. Results of the soil resistivity measurements are presented in the table below. Interpretation of the data from this survey was not included in our scope of services for this project. Page 4 Proposed North Mountain Communication Tower Z i p pe rG eo Shelton, Mason County,Washington Geoprofessional Consultant Project No.: 2228.01 August 15, 2023 Results of Soil Resistivity Measurements a= 5 FEET 10 FEET 15 FEET 20 FEET Test Direction Formula: p = Rx957.5 Rx1915 Rx2872.5 Rx3830 R (ohms measured) 98.3 32.3 16.2 8.3 East-West p (ohm-cm) -F 94,122 61,854 46,534 _T 31,789 CONCLUSIONS AND RECOMMENDATIONS General Based on the subsurface exploration program and our analysis, we conclude that the proposed communication tower project is feasible from a geotechnical standpoint,contingent on proper design and construction practices. Based on our analyses, a mat foundation can be used for the communication tower and conventional spread footings with a slab-on-grade concrete floor can be used for the new equipment building. Based on the results of our slope stability analyses,we recommend that the radio tower be set back from the top of the slope to the west a minimum distance of 35 feet so that its location will not adversely affect the stability of the existing slope or be impacted by the predicted earth movement during a design earthquake. Environmental Critical Areas Considerations Section 8.52 of the Mason County Resource Ordinance (MCRO) presents definitions of environmentally critical areas that are considered by the Mason County Department of Community Development during the development review process. This report addresses the nature of geologically hazardous areas, seismic hazard areas, and erosion hazard areas regulated under the ordinance relative to the project site and planned development. Geologically Hazardous Areas: In our opinion, the project site itself does not meet the criteria for a "geologically hazard area"as presented in MCRO Sections 8.52.030 and 8.52.140.1.A. As part of the MCRO requirement, we reviewed the Coastal Zone Atlas and geologic maps presented in Section 8.52.140.1.B. These references do not cover the project site.However,we did review the Washington State Department of Natural Resources Open File Report, OFR 2003-15, titled Geologic Map of the Shelton 1:100,000 Quadrangle, Washington, (2003).The closest landslides are mapped more than 1 mile north and west of the project site.These slides appear to be associated with side slopes of stream drainages. The project site is estimated to be set back about 35 to 70 feet from a slope that essentially comprises the southern side of North Mountain. Figures 3, 4, and 5 present topographic maps of the North Mountain Page 5 Proposed North Mountain Communication Tower Zi ppe rGeo Shelton, Mason County,Washington Geoprofessional Consultants Project No.: 2228.01 August 15, 2023 area.These maps were generated using LiDAR data obtained from the Puget Sound LiDAR Consortium. In general,the nearby slopes are steeper than 40 percent and extend vertically for hundreds of feet over at least % mile horizontally. Figure 5 presents the distribution of slopes around the project site. It is clear that the slopes to the south of the project site would be classified as a geologically hazardous area based on slope inclinations in excess of 40 percent(8.52.140.1.A.vi).Section 8.52.140.4.F.ii states that a 50-foot buffer or the minimum buffer recommended by the geotechnical professional in the geotechnical report is required around geologically hazardous area. Currently, the "buffer" area is essentially bare and there is a telecommunication tower and equipment building in this area. Given the existing conditions and the results of slope stability analyses presented in the following section of this report, we recommend that a 35-foot buffer be maintained and that the property owner and tower operator ensure through periodic inspection that accelerated erosion does not occur during or after tower construction. Seismic Hazard Areas: In our opinion,the project site itself does not meet the criteria for a "seismic hazard area" as presented in MICRO Sections 5.52.030 and 5.52.150. However,the project site is estimated to be set back about 35 to 70 feet from a slope that meets the definition of a geologically hazardous area (referenced as a landslide hazard area in 8.52.150.1.A.vi) and therefore meets the definition of a seismic hazard area.The MCRO indicates that the project geotechnical report must demonstrate conclusively that the seismic hazard can be overcome. Erosion Hazard Areas: In our opinion, the project site itself does not meet the criteria for an "erosion hazard area" as presented in MCRO Sections 5.52.030 and 5.52.160. The site is underlain by the Tebo gravelly loam (Tf), which is not subject to severe erosion according to the USDA Soil Survey of Mason County. It is described as being in Hydrologic Soil Group B. Based on the slope stability analysis presented in the following section of this report, It is our opinion that a setback distance of 35 feet for the proposed tower and equipment building is a satisfactory distance from the geologically hazardous area and seismic hazard area and their location will not adversely affect the stability of the existing slope, nor would the predicted earth movement during a design earthquake adversely affect the planned site improvements Slope Stability Analysis A slope stability analysis was completed on a representative profile, as shown on Figure 7, using SLOPE/W (2007 Version). The profile used to develop the slope stability model is presented on Figure 8. Soil properties were estimated by back-calculation using the topographic and subsurface profiles developed for the model and the peak ground acceleration measured in Shelton, Washington during the February 28, 2001 Nisqually Earthquake that was measured at Richter magnitude 6.8. The peak horizontal ground acceleration measured in Shelton was 0.097g.This data was obtained from the Pacific Northwest Seismic Network website (http://www.pnsn.org/). Because no indications of slope movement were observed during the site visits, a conservative safety factor of 1.1 was assumed during the 1991 earthquake and Page 6 Proposed North Mountain Communication Tower Shelton, Mason County,Washington Project No.: 2228.01 August 15, 2023 back calculated soil properties for the model were determined. Based on the back calculated soil properties, a static safety factor against sliding was calculated. For the static condition, a minimum safety factor of 1.41 was determined for shallow slides that would not extend more than a few feet past the top of the steep slope and would not affect the proposed tower site. It should be noted that the slope stability analysis presented herein was originally completed as part of a 2009 study completed by Terracon under the direction of now ZGA principal Thomas Jones. As such, the seismic stability analysis began by considering a pseudo-static horizontal ground acceleration of 0.28g per the 2003 IBC and USGS 1996 Interactive Deaggregation for the site coordinates (requirements in 2009). A minimum safety factor of 0.82 was obtained indicating that a relatively shallow slope failure extending a few feet past the top of the steep slope could occur during the design earthquake. Section 8.52.140.5.E.iv of the current MCRO requires a seismic evaluation using a pseudo-static horizontal acceleration 0.15g. This analysis was also completed as part of the 2009 study. Using a 0.28g ground acceleration, the pseudo-static model indicates that slide configurations with a safety factor of less than 1.1 could extend up to about 28 feet west of the top of the slope. Using a 0.15g ground acceleration, the pseudo-static model indicates that slide configurations with a safety factor of less than 1.1 could extend up to about 16 feet west of the top of the slope. In our opinion, the 2009 analysis is appropriate for the site conditions and current code requirements. The static and pseudo-static models indicate that the most probable slides with static safety factors less than 1.5 and pseudo-static safety factors less than 1.1 will be of the relatively shallow, near-surface type and will not extend back into the proposed tower area. The site is estimated to be about 50 feet away from the top of the slope. It is our opinion that a setback distance of at least 35 feet for the proposed tower and equipment building is a satisfactory distance from the geologically hazardous area and its location will not adversely affect the stability of the existing slope, nor would the seismic slope instability adversely affect the tower. Site Preparation We anticipate that minimal site preparation work will be necessary due to the absence of topsoil, vegetation, and unsuitable fill soils.The surficial soils are interpreted to consist of gravelly silty sand with trace clay. This material could be prone to disturbance in the presence of excess moisture. A working surface of quarry spalls or crushed gravel may be necessary if site work is performed during wet weather or site conditions. If earthwork takes place during freezing conditions, we recommend that all exposed subgrades be allowed to thaw and be recompacted prior to placing subsequent lifts of structural fill or foundation elements. Page 7 Proposed North Mountain Communication Tower Zi pp�rGeo Shelton, Mason County,Washington Geoprofessional Consultant Project No.: 2228.01 August 15, 2023 Temporary Erosion Control We recommend installing temporary erosion control BMP's prior to earthwork at the site in order to reduce erosion and sediment transport during construction. We recommend consideration of the following: • Clearly defining the limits of earthwork; • Install erosion controls measures such as a silt fence on the down-gradient sides of the site; • Cover stockpiled soils with anchored sheet plastic if wet weather is forecasted; • Utilize straw wattles, as necessary, to control erosion and sediment transport downslope of the site; and, • Cover temporary work areas with 4 inches of 2-inch minus crushed gravel if construction takes place in the wetter periods of the year. Permanent Erosion Control Appropriate permanent erosion control measures should be incorporated into the site development plans in order to satisfy Mason County requirements. We recommend installing and maintaining permanent erosion and sedimentation control BMP's as necessary to limit long-term degradation of the site and surrounding area. We recommend consideration of the following: • Stabilize the ground surface within the tower footprint and at least 5 feet beyond by covering with 4 to 6 inches of 2-inch minus crushed gravel. This would protect the soil from the erosive forces of raindrop and water droplet (off the tower) impact. • Locate water bars upslope or downslope of the site, if necessary, to convey runoff to vegetated areas where erosion can be controlled; • If straw wattles are used for temporary erosion control, leave them in place after construction to trap sediment and promote development of vegetation strips; • Grades should be incorporated that reduce the opportunity for concentrated runoff to develop that could lead to accelerated erosion; and, • Maintain the existing vegetation on the steeper slopes west of the site. Utilizing(as necessary)the temporary and permanent erosion and sedimentation control BMP's discussed above, it is our opinion that on- and off-site impacts as a result of site development will be minimal. Provided that the geotechnically-related aspects of the project are constructed and monitored in accordance with the project plans and specifications, applicable construction standards, and recommendations based on observed field conditions, it is our opinion that construction and development will not increase the potential for adverse soil movement. Page 8 Proposed North Mountain Communication Tower Zi pperGeo Shelton, Mason County,Washington Geoprofessional Consultants Project No.: 2228.01 August 15, 2023 Temporary and Permanent Cut Slopes Temporary slope stability is a function of many factors, including the following: • The presence and abundance of groundwater; • The type and density of the various soil strata; • The depth of cut; • Surcharge loads and slopes adjacent to the excavation, and; • The length of time the excavation remains open. It is exceedingly difficult under the variable circumstances to pre-establish a safe and "maintenance-free" temporary cut slope angle. Therefore, it should be the responsibility of the contractor to maintain safe slope configurations since the contractor is continuously at the job site, able to observe the nature and condition of the cut slopes, and able to monitor the subsurface materials and groundwater conditions encountered. It may be necessary to drape temporary slopes with plastic or to otherwise protect the slopes from the elements and minimize sloughing and erosion. We do not recommend vertical slopes or cuts deeper than 4 feet if worker access is necessary.The cuts should be adequately sloped or supported to prevent injury to personnel from local sloughing and spalling. The excavation should conform to applicable Federal, State, and local regulations. According to Chapter 296-155, Part N, Excavation, Trenching and Sheeting, of the Washington Administrative Code (WAC), it is our opinion that the upper 8 feet of soil encountered in borings B-1 through B-3,would be classified as Type C soils.According to the Code,excavations less than 20 feet deep in Type C soils may be cut at a maximum temporary slope angle of 1.5H:1V(34 degrees).We recommend that temporary cuts exposed to inclement weather be covered with sheet plastic to reduce the risk of erosion and destabilization.The towerfoundation excavation should take into consideration the proximity to an existing slope immediately to the north of the project site. Temporary and permanent excavations should not negatively impact the stability of the existing slope. We recommend all permanent slopes be designed at a 2H:1V inclination or flatter. It has been our experience that the permanent slopes steeper than 2H:1V will tend to ravel and slough to a flatter inclination over time. In addition, with the steeper slopes, topsoil erodes readily, and it is more difficult and takes longer to establish vegetation for slope protection. Structural Fill All structural fill should be free of organic material, debris, or other deleterious material. Individual particle size should be less than 6 inches in maximum dimension.Structural fill should be placed in lifts no greater than 8 inches in loose thickness. In general, structural fill should be compacted to a firm and non- yielding condition of at least 90 percent of the modified Proctor maximum dry density as determined by the ASTM: D 1557 test procedure. Page 9 Proposed North Mountain Communication Tower Shelton, Mason County,Washington Project No.: 2228.01 August 15, 2023 Structural fill is not recommended beneath the tower foundation due to the recommended bearing capacity. Instead, if fill is necessary beneath the foundation, we recommend that it consist of lean-mix concrete with a minimum 28-day compressive strength of 150 psi. Permanent fill placed on existing slopes or temporary cut slopes steeper than 5H:1V (20% or 11 degrees) should be keyed and benched into native soils of the underlying slope. We recommend that the base downslope key be cut into undisturbed native soil. The key slot should be at least 4 feet wide and 2 feet deep. The hillside benches cut into the native soil should be at least 3 feet in width. The face of the embankment should be compacted to the same 90 percent relative compaction as the body of the fill. This may be accomplished by overbuilding the embankment and cutting back to the compacted core. Alternatively, the surface of the slope may be compacted as it is built or upon completion of the embankment fill placement. The suitability of soils for structural fill use depends primarily on the gradation and moisture content of the soil when it is placed. As the amount of fines (that soil fraction passing the U.S. No. 200 sieve) increases, soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult, or impossible, to achieve. Generally, soils containing more than about 5 percent fines by weight (based on that soil fraction passing the U.S. No. 4 sieve) cannot be compacted to a firm, non-yielding condition when the moisture content is more than 2 percent above or below optimum. The optimum moisture content is that moisture which yields the greatest dry density under a specified compactive effort. In our opinion, the on-site soils available for reuse as structural fill are suitable for use as structural fill provided the moisture content can be controlled to achieve the minimum recommended levels of compaction. Based on the proposed site development, we anticipate that the majority of the available on-site soil will consist of gravelly silty sand with trace clay. At the time of the subsurface evaluation, the site soils encountered in the explorations had moisture contents above their estimated optimum moisture content with respect to their possible use as structural fill. However, soil moisture conditions should be expected to change throughout the year.The use of the soil as structural fill will require that strict control of the moisture content be maintained during the grading process. Selective drying of over-optimum moisture soils may be achieved by scarifying or windrowing surficial materials during extended periods of dry weather. Soils which are dry of optimum may be moistened through the application of water and thorough blending to facilitate a uniform moisture distribution in the soil prior to compaction. In the event that inclement weather or wet site conditions prevent the use of on-site soil or non-select material as structural fill, we recommend that a "clean", free-draining pit-run sand and gravel or crushed gravel be used. Such materials should generally contain less than 5 percent fines, based on that soil fraction passing the U.S. No.4 sieve,and not contain discrete particles greater than 6 inches in maximum Page 10 Proposed North Mountain Communication Tower Shelton, Mason County,Washington Project No.: 2228.01 August 15, 2023 dimension. It should be noted that the placement of structural fill is, in many cases, weather dependent. Delays due to inclement weather are common, even when using select granular fill. We recommend that site grading and earthwork be scheduled for the drier months, if at all possible. IBC Seismic Design Parameters 2018 IBC Seismic Design parameters are summarized on the table below. Code Used Site Classification 2018 International Building Code(IBC)1 B Z S,Spectral Acceleration for a Short Period 1.579g Si Spectral Acceleration for a 1-Second Period 0.620g Fa Site Coefficient for a Short Period 1.000 F�Site Coefficient for a 1-Second Period 1.000 SMs Maximum considered spectral response acceleration 1.579g for a Short Period Sm,Maximum considered spectral response acceleration 0.620g for a 1-Second Period 5os Five-percent damped design spectral response 1.053g acceleration for a Short Period 5o1 Five-percent damped design spectral response 0.413g acceleration for a 1-Second Period 1. In general accordance with the 2018 International Building Code and ASCE 7-16. IBC Site Class is based on the average characteristics of the upper 100 feet of the subsurface profile. 2. The site borings extended to a maximum depth of 31.5 feet below grade.ZGA therefore determined the Site Class assuming that very dense residual soils and bedrock extend to 100 feet as suggested by published geologic maps for the project area. Tower Mat Foundation The mat foundation subgrade should consist of medium dense to dense, undisturbed,firm and unyielding native soils or lean-mix concrete placed above undisturbed native soils. If lean mix concrete is used below the foundation, we recommend that it extend at least 6 inches beyond the foundation footprint and have a minimum 28-day compressive strength of 150 psi. The lean mix concrete may be formed or cast neat against excavation walls. Foundations should never be cast atop soft, loose, organic, or frozen soils, or atop subgrades covered by standing water. A representative of our firm should observe all subgrades before the bottom mat of reinforcing steel is placed or any concrete or lean mix is poured in order to observe that subgrade soils have been adequately prepared. Page 11 Proposed North Mountain Communication Tower Z i p pe rG eo Shelton, Mason County,Washington Geoprofessional Consultants Project No.: 2228.01 August 15, 2023 Medium dense to dense, gravelly silty sand (weathered basalt bedrock) soils suitable for mat foundation support were encountered at variable depths below the existing ground surface. Adequate bearing soils were encountered at a depth of about 8 feet in boring B-1 located about 30 to 35 feet east of the proposed tower location. A bedrock outcrop is located west of the proposed tower location. As such,we anticipate that the depth to adequate bearing soils at the tower location may be less than 8 feet. A maximum allowable soil bearing pressure of 5,000 pounds per square foot is recommended for static footing loads if any portion of the mat foundation is supported on medium dense soil and is embedded at least 4 feet below the lowest adjacent grade around the foundation.This bearing pressure incorporates a factor of safety of 3 and can be increased by one-third to accommodate transient wind or seismic loads. We expect that uplift loads will be resisted by the dead load of the mat foundation, as well as the soil material covering the mat. Native soils used to cover the mat and compacted to a minimum of 90 percent of the modified Proctor maximum dry density could be assumed to have a unit density of 120 pcf. Lateral loads on the foundation, caused by seismic or transient loading conditions, may be resisted by a combination of passive soil pressure against the side of the foundation and shear friction resistance along the base. An allowable base friction value of 0.35 and an allowable passive earth pressure of 350 pounds per cubic foot (pcf), expressed as an equivalent fluid unit weight, may be used for that portion of the foundation embedded more than 18 inches below surrounding finish grade. If structural fill is placed around the mat rather than casting neat against the soil, a passive resistance of 250 pcf should be used full-depth, provided the backfill is compacted to a minimum of 90 percent of its modified Proctor maximum dry density. If this is the case, enough space between the excavation sidewalls and the mat should be provided to provide access for compaction equipment. We estimate that total and differential post-construction settlements of a properly designed and constructed foundation bearing on a properly prepared subgrade could approach 1 inch. Equipment Building Grading Considerations In order to construct the building pad, it may be necessary to cut into the toe of the existing slope to the north. In order to reduce the cut into the slope, we recommend that the building pad be elevated. Designing a balanced cut/fill building pad would provide for the reuse of the cut soils as structural fill in the fill portion of the building pad. Any fill placed beneath the building should be compacted to a minimum of 95 percent of the modified Proctor maximum dry density determined in accordance with ASTM D 1557. Equipment Building Shallow Foundations Project plans indicate that the equipment building will be supported on perimeter shallow spread footings with interior thickened slab footings. Based on our analyses, conventional spread footings will provide adequate support for the proposed building provided that the foundation subgrades are properly Page 12 Proposed North Mountain Communication Tower Z i p pe rG eo Shelton, Mason County,Washington Geoprofessional Consultants Project No.:2228.01 August 15, 2023 prepared. We anticipate that foundation subgrade soils will generally consist of loose to medium dense silty sand with variable gravel content. Foundations should not be supported on existing fill soils. The following sections provide recommendations for the equipment building shallow foundations. Allowable Bearing Pressure: We recommend that all exposed foundation subgrades be moisture conditioned and compacted to a firm and non-yielding condition and to at least 95 percent of the modified Proctor maximum dry density determined in accordance with ASTM D 1557. Continuous and isolated column footings bearing on compacted existing site soils or structural fill placed and compacted in accordance with this report may be designed for a maximum allowable, net, bearing capacity of 2,500 psf. A one-third increase of these bearing pressures may be used for short-term transient loads such as wind and seismic forces. The above-recommended allowable bearing pressure includes a 3.0 factor of safety. Shallow Foundation Depth and Width: For frost protection, the bottom of all exterior footings should bear at least 24 inches below the lowest adjacent outside grade,whereas the bottoms of interior footings should bear at least 12 inches below the surrounding slab surface level. We recommend that all continuous and isolated column footings be at least 12 and 24 inches wide, respectively. Lateral Resistance: Resistance to lateral loads can be calculated assuming an allowable passive resistance of 250 pcf equivalent fluid pressure (triangular distribution) and an allowable base friction coefficient of 0.35. We recommend that passive resistance be neglected in the upper 18 inches of embedment. Estimated Settlement: Assuming the foundation subgrade soils are prepared in accordance with recommendations presented herein,we estimate that total and differential settlements will be less than 1 inch and % inch over a distance of about 40 feet, respectively. Equipment Building Slab-On-Grade Concrete Floor Floor slabs for the equipment building may be supported on the medium dense residual soil deposits or new structural fill placed in accordance with the recommendations provided in this report. Floor slabs should not be supported on existing fill soils. The following sections provide recommendations for on- grade floor slabs. Subgrade Preparation: We recommend that all exposed floor slab subgrades be moisture conditioned and compacted to a firm and non-yielding condition and to at least 95 percent of the modified Proctor maximum dry density determined in accordance with ASTM D 1557. Capillary Break: To provide a capillary break, uniform slab bearing surface, and a minimum subgrade modulus of 200 pci, we recommend the on-grade slabs be underlain by a 6-inch thick layer of compacted, crushed rock meeting the requirements of WSDOT Standard Specification Section 9-03.9(3), Crushed Surfacing Top Course, with the modification of a maximum of 7 percent passing the U.S. No. 200 sieve. Alternatively, a clean angular gravel such as No. 7 aggregate per WSDOT: 9-03.1(4)C could be used for this Page 13 Proposed North Mountain Communication Tower Zi ppe rGeo Shelton, Mason County,Washington Geoprof, ^nal:o „!tant Project NO.: 2228.01 August 15, 2023 purpose. Alternative capillary break materials should be submitted to the geotechnical engineer for review and approval before use. Vapor Retarder: From a geotechnical perspective,a vapor retarder is not necessary. However,if potential slab moisture is a concern due to the presence of moisture sensitive equipment within the building or where moisture sensitive floor coverings are planned, we recommend using a puncture-resistant 10- to 15-mil thick product such as Stego Wrap, or an approved equivalent, that is classified as a Class A vapor retarder in accordance with ASTM E 1745. To avoid puncturing of the vapor barrier, construction equipment should not be allowed to drive over any vapor retarder material. Where pipes and other objects penetrate the barrier, we recommend taping these per the manufacturer's recommendations. We recommend the slab designer and slab contractor refer to ACI 302 and ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder/barrier. Ecology Block Retaining Wall We understand that the development will include an ecology block retaining supporting a cut into the toe of the slope along the north side of the equipment building. We understand that the ecology block wall will have a maximum height of about 4 feet (2 blocks tall) and a maximum backslope angle of 2H:1V. We recommend that the retaining wall incorporate the follow design features. • Embed the base course of blocks at least 6 inches below finished grade at the wall face. • Batter the wall into the slope at an inclination of 1H:6V. • Place blocks in a running bond pattern to prevent continuous vertical joints. • Found the wall on a firm and non-yielding subgrade compacted to at least 95 percent of the modified Proctor maximum dry density per ASTM D 1557. A leveling course consisting of 4 to 6 inches of compacted crushed rock may be used below the base course of blocks to assist in grade control and uniform support of the wall. • Incorporate an 18-inch wide zone of quarry spalls or permeable ballast between the back of the wall and the temporary cut slope to facilitate drainage and reduce the potential for hydrostatic loads. CLOSURE The recommendations presented in this report are based, in part, on the explorations reviewed for this study.The performance of earthwork, structural fill, foundations, retaining walls, and floor slabs, depend greatly on proper site preparation and construction procedures. We recommend that Zipper Geo Associates, LLC be retained to provide geotechnical engineering services during the foundation construction phases of the project. If variations in subsurface conditions are observed at that time, a qualified geotechnical engineer could provide additional geotechnical recommendations to the contractor Page 14 Proposed North Mountain Communication Tower Zi ppe rGeo Shelton, Mason County,Washington Geop ofessional Consultant Project No.: 2228.01 August 15, 2023 and design team in a timely manner as the project construction progresses. This report has been prepared for the exclusive use of WSH North Bay Broadcasting, LLC, and its agents, for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, express or implied, are intended or made. Site safety,excavation support,and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Zipper Geo Associates, LLC reviews the changes and either verifies or modifies the conclusions of this report in writing. Page 1S APPENDIX A _ - � i � ,J -"t ems•kite - - ...r r i- P i' - tape _.- .. ._ .- • . SITE LOCATION , NOTES: N Geotechnical Engineering Report North Mountain Communications Tower Shelton,Mason County,Washington THIS SITE MAP WAS EXCERPTED FROM THE USGS 7.5 MINUTE VANCE CREEK OUAD MAP SITE LOCATION MAP SITE MAP!S FOR GENERAL LOCATION ONLY AND IS NOT INTENDED FOP CONSTRUCTION Date:August 2019 Job No. 2228.01 PURPOSES Zipper Geo Associates,LLC FIGURE 19019 36th Ave.W.,Suite E 1 EFERENCE:Geotechnical Engineering Report,Proposed Radio Broadcast Tower,North Mountain,Figure 1,prepared by Terracon 2009. Lynnwood,WA i SHT 1 of 1 LEGEND B-1 BORING NUMBER AND APPROXIMATE LOCATION FrAUIVG x:, - -%&2 - ' GEOLOGIC HAZARD AND SEISMIC HAZARD AREAS IT",u:r � 30 0 15 U�4:^Lll. W.i T'r"�;=: - — STALE IN FEET I. r :L(!1:ilCY! Gentec -ll EN—IM Re Norm MouMam Commurucelim Toeei Stenon.Masan Carty.WasM1iglan SITE AND EXPLORATION PLAN DATE A 2019 bbw TJ1B91 Lpp«Geo An—We LLC FIGURE 19019 36th Ave.W.,SuHe E REFERENCE:Sile Pion and V nuy Map,Sheet S-2,prepared by Tower Englneerirg Company 2019 Ly--d,WA SHT 101 i I - • .•,-• v ' I1 �•V 'd t�� '/ ,{1�t1•a• r II f `� i� ./ ' '``S.rF ,y�;�t. t � •is � Wig' y . .�+ *,v .�f �ij1f� ,;,ia t. i�aY j• taw �..C- Y _ ��]1A r`,r .•-J + r:, st 't}Te 5 T,�1Y'' f •Sr t , f�•. i, r,t ,at. 4. IFIL / 1 r +� f i.♦�� it ,'• h � r, .45 .�p1 1'•.j <•�� t� ,.`• '}i,(r f�'1 ' t f „`�Yt �f� t .�i � r<,•r't"1i`.�'�:J O f yyr, �4 j• tI •fY. � i ;i�':tiy�� 4 �. • ; , ��r�r'• �tt� art++� �yc :� /'ar fS'< �X7. l�Y ��'�r ��r,��r _,��#�i� Yfi� �� '- r �! ��- a •t //)��•..f•.•.�['`` K. t .{'!. i• �. j"►i•i� ' '► � �.'. �Y: _t .r a�"e.+aral �•� »�`� ♦' _. � t- -illw 7. '•:Si �!' •{ ___I� t:. -.'ii'i1-� f _1 N Geotechnical Engineering Report North Mountain Communications Tower Shelton,Mason County,Washington SITE LOCATION AERIAL PHOTOGRAPH Date:August 2019 Job No 2228.01 Zipper Geo Associates,LLC FIGURE ^ 19019 36th Ave.W.'s.ne E 3 EFERENCE:Geotechnical Engineering Report,Proposed Radio Broadcast Tower,North Mountain,Figure 3,prepared by Terracon 2009. Lynnwood,WA SHT.1 of 1 ad„ Q1d _ b T• ^" fvA ago o 4 _ SITE LOCATION ,� T A - 011 DW ds ,m 31 Im � ap me, a ok Oa aM Ere ° 00 ow ogo OP o,° C. ow QV Wnb NOTES. Geologic map developed from Washington State Department of N GeOteChniCal Engineering Report Natural Resources . Geologic Map of the Shelton 1:100.000 Quads ngle.Washington.Robert L.Logan.2003. North Mountain Communications Tower Shelton,Mason County,Washington GEOLOGIC MAP OF PROJECT AREA Date:August 2019 Job No. 222801 Zipper Goo Associates,L!C FIGURE 19019 36th Ave.W.,Sude E EFERENCE:Geotechnical Engineering Report,Proposed Radio Broadcast Tower,North Mountain,Figure 4,prepared by Terracon 2009. Lynnwood,WA SHT.1 of 1 WINjail, t i D e r SM 4 193 a tam I'll", NOTES N Geotechnical Engineering Report North Mountain Communications Tower Topographrc map developed from UDAR data provided by the Shelton,Mason County,Washington Po"Sound LIDAR Consortium UDAR GENERATER TOPOGRAPHIC MAP 10 FOOT CONTOURS Date:August 2019 Job No. 2228,01 Zipper Geo Associates,LLC FIGURE 19019 36th Ave.W.-Suite E EFERENCE:Geotechnical Engineering Report,Proposed Radio Broadcast Tower,North Mountain,Figure 5,prepared by Terracon 2009. Lynnwood,WA SHT 1 of 1 lip �� ► Y��• �, 1�. '��}ill •�` � �� -�t �L= \,1�.` _ t )� _ .� UK �� ! r _ l _-S1TE L0�'170N 7 t J \- SLOPE STABIVITY PROFILE LINE i .. 250 rt 5lJ n 6Y1 n 750R EXPLANATION: Orange Areas Slopes greater than 70% Greer.Areas Slopes between 40%-70% White Areas Slopes less than 40% N Geotechnical Engineering Repoli North Mountain Communications Tower Shelton,Mason County,Washington Data Reference UDAR Bare Earth DEM(Digital Elevation Model)047123c31 BE,2000-2005.The Woodlands. LIDAR GENERATER TOPOGRAPHIC MAP TX Terrapomt Available Puget Sound UDAR Consortium.Seattle.Washington, 10 FOOT CONTOURS-SLOPES IN PERCENT http:Urc ay2 ess washmgton.edu!datarraster/lidarnndex htm(JL.ly 13,2009) Elevation accuracy considered to Date:A ust 2019 Job No. 2228.01 be accurate to 1 foot vertical in the 1 inch=1.000 It horizontal sale Horizontal Datum NAD83-State Plane Zipper Goo Associates,LLC FIGURE 19019 36th Ave.W-Suite E 7 REFERENCE:Geotechnical Engineering Report,Proposed Radio Broadcast Tower,North Mountain,Figure 7,prepared by Terracon 2009. Lynnwood,WA SHT.1 of 1 From Pos: 1017290.89, 126879.69 To Pos: 1017416.10, 126386.92 2850ft - - - - - - - - - - - - - - — - - - - - - - - - - - - - - - 2800ft - — - — - — - — - — - — - — - - - - - - - 275Vft - - - - - - - - - - - - - - - - - - - - -~�- - - - - - - - - - - - - - - `100tt — — - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - — - — - — . 125 ft 250 ft 375 ft 509 ft NOT,S Topographic map developed from LIDAR data provided by the Puget Sound LIDAR Consortium, N Geotechnical Engineering Report North Mountain Communications Tower Shelton,Mason County,Washington CROSS SECTION FROM LiDAR GENERATED TOPOGRAPHIC MAP-10 FOOT CONTOURS Date:August 2019 Job No. 2228.01 Zipper Geo Associates,LLC FIGURE 19019 36th Ave.W.,Suite E 81 REFERENCE:Geotechnical Engineering Report,Proposed Radio Broadcast Tower,North Mountain,Figure 8,prepared by Terracon 2009. Lynnwood,WA SHT 1 of 1 i.Rb • : : • • • • 2100 • I 1P. II(A y� 9aabn YO•Ilie y iv tea i hi,�r�.ry�,V�. \ N•me:r bn•eblau•Yry•uidY w'errv•Ltro aatl {�� Y�„Jh� _ Mobl WxCaNlu� h.ii .(f:..'4 uell w.MK toe z� wpm In n.aNi;,-i-otf�, ' 5-��, - 4" ��y,. ��°i1?��'`�w Nan•: c•M ono ar a.w o•map, irsa ��•.��jj````i 'Nim DPrbvey tlPw ergunewa 1-•n� Me0 coM•-e•is pe i.P ,r a. iw _ .a ¢ vo i.. w. a:� ,-, ,- •z.' ..� EepYNrrsl6gerarg Repan NOM Maulairi Camaaeolm Tower DNt— shmw Mean Cwty.welrglan STATIC SLOPE STABILITY ANALYSIS DATE 2019 Am No 222501 appP Gee Aewa,h.,UC FIGURE ^ eotephnica 1901936th Ave W..S.KeE 7 REFERENCE Gl Enpiroerrrg Report,Proposed Radio Broad 9 Tower,Na h Nbintain.Fg—9.prepared ey Terracon 20M Lynrnvaod.WA SNT 1ef1 1 .iaD..u Xw...A+�M a vr.a..X.oe ota.• \ Mm.c wn,-co,Xomo Ph{8 B; a NXmeDma.to aV'Y dmwaL'h..M Mg�X+at ``\ NDrrx. \wms^xXL'weNwpuW ata \ ModN:MOM pTM� Mudd'YDXr-CauoMr \\\\ Unn Ww�pnt iT5 UnX We•�nt 1J0 D" a :2D J# COb.aron>0 Wr r'N9 0' 11r: GXdeCtr Erg,mmg Rtpal N.h MDu—Cammur -T-., SIe m Masan CCMXy.VV s VO Diatexe PSEUDO-STATIC SLOPE STABILITY ANALYSIS DATE 1019 Jm ND 221E DI 1 gal G6u AaX W Su,LLC FIGURE 1901936M Ave.W..Sude E REFERENCE.Geot-h,,-I Engmeenng Report.Proposed Radio Broadcast Tower,Nonb Mountain,Figure 10,prepared by Terracon 2009 Lynnwood,WA SHT 1 ofi PROJECT:North Mountain Tower JOB NO. J-1592 BORING B-1 PAGE 1 OF 1 Location: Approximate Elevation: 101 feet± Soil Description m m L D Penetration Resistance y ad ac C d c CL C Standard Blows per foot Other m o N to Z C9 Z H 0 10 20 30 40 S-1 AL: ; 13 Bare soil surface over medium dense,wet,orange- _ ___ brown,gravelly,silty SAND with trace clay �.-- --r--r-- r--r--r --T--T- -T- -T-- ---------------------------------------------- Grades to very loose,wet,orange-brown,silty,gravelly S-2 ; 4 SAND 5 ---------------------------------------------- S-3 1 ; ; 10 Medium dense,wet,orange-brown,silty,gravelly _ SAND -- ----- - - --- ---- - - -- - --- Grades to medium dense,wet,gray-brown,silty,sandy S-4 * 20 GRAVEL — -- --•--•- - • 10 S-5 ; 29 L__L __ L __L __ L -_L__ !_ _ J_ _J -------------------------------------------_-_ ...- _--r-- r--T--T-- r--T--T- -T Dense to very dense,wet,gray-brown,silty sandy S-6 49 GRAVEL __L-- -- -- -- -- -- - - ' -- -- 15 Boring completed at 16.5 feet on 4/15/03 ; No groundwater observeded at the time of drilling ; ----- - ------- - 20 --•- r--r--r--r--T-- --t- - T LL__L__L__ L__l__1_ _ 1_- J __ 25 ; Explanation 0 10 20 30 40 50 Monitoring Well Key Moisture Content I 2-inch O.D.split spoon sample Plastic Limit Natural Liquid Limit Clean Sand 3-inch I.D Shelby tube sample ISS Bentonite ® No Recovery fi• Grout/Concrete Drilling Method: B Screened Casing GSA Grain Size Groundwater level at time of drilling ATD or date of measurement Blank Casing 200 Wash Fines Content Zipper Zeman Associates,Inc. BORING LOG Figure A-1 Geotechnical& Environmental Consulting Date Drilled:4/15/03 Logged By:TAJ PROJECT:North Mountain Tower JOB NO. J-1592 BORING B-2 PAGE 1 OF 1 Location: Approximate Elevation: 102 feet+ Soil Description Penetration Resistance w QN Z Standard Blows per foot Other j 0 10 20 30 40 Z Bare soil over -�•�•- __L _L__L __1__1__ 1__L__1__!__ __i__T__T_ _T__ _ 5 Medium dense,wet,orange-brown,silty,sandy _�� S-1 ; ; ; 12 GRAVEL with silty,gravelly SAND with trace clay ___ __ __ _____ _;__;__ ; _;__ 10 Medium dense,wet,orange-brown,silty,sandy S-2 11 GRAVEL with silty,gravelly SAND with trace clay --- -- --- -- -- -- -- - -- r__ r__ _ _ _ _ T __ T_ _T__T__T_ Medium dense,wet,orange-brown,silty,gravelly SAND S-3 ; 13 20 Medium dense,moist,brown,silty SAND with some gravel and trace clay S4 23 L Boring completed at 21.5 feet on 4/15/03 No groundwater encountered ; r__T_ _ T__T__ l _ 25 Explanation 0 10 20 30 40 50 Monitoring Well Key Moisture Content I 2-inch O.D.split spoon sample Plastic Limit Natural Liquid Limit M Clean Sand TF 3-inch I.D Shelby tube sample ® Bentonite ® No Recovery Grout/Concrete Drilling Method: B Screened Casing GSA Grain Size Groundwater level at time of drilling ATD or date of measurement 0 Blank Casing 200 Wash Fines Content Zipper Zeman Associates, Inc. BORING LOG Figure A-2 Geotechnical i Environmental Consulting Date Drilled:4/15/03 Logged By:TAJ PROJECT: North Mountain Tower JOB NO. J-1592 BORING B-3 PAGE 1 OF 1 Location: Approximate Elevation: 105 feet± Soil Description Penetration Resistance IL ? w o F� cn Standard Blows per toot Other w Z � H 0 10 20 30 40 Z Bare soil over L- - L- 1- - 1 -- r-_ r_ _ T__T_ _ T__T-_ __ _ Medium dense,wet,orange-brown,gravelly,silty �V 5 SAND with trace day ---------------------------------------------- S-1 Medium dense,moist,dark brown,silty,sandy - GRAVEL --- ----------- --------- --- - - ------- --- --- L- Dense,moist,dark brown,gravelly,silty,SAND with S-2 * 35 trace clay -- --�-- --r-- ....- . . L__L L__1__1_ _ 1 __1_ _1 _ 1 . Dense,moist,brown,gravelly,silty,SAND with trace --r--r - -r--r--;- - ----- ---- --- clay S-3 45 15 Boring completed at 16.5 feet on 4/15/03No groundwater encountered at time of drilling ; 20 ; L_ !_ __T__ T__T__T._i _i_ 25 Explanation 0 10 20 30 40 50 I Monitoring Well Key Moisture Content 2-inch O.D.split spoon sample Plastic Limit Natural Liquid Limit 0 Clean Sand F3-inch I.D Shelby tube sample ® Bentonite ® No Recovery Grout/Concrete Drilling Method: 8 Screened Casing GSA Grain Size Groundwater level at time of drilling 200 Wash Fines Content AM or date of measurement 0 Blank Casing Zipper Zeman Associates,Inc. BORING LOG Figure A-3 Geotechnical&Environmental Consulting Date Drilled:4/15/03 Logged By: TAJ LOG OF BORING NO. B-4 Page 1 of 1 CLIENT South Sound Broadcasting SITE North Mountain PROJECT Mason County,Washington North Mountain Tower SAMPLES TESTS C7 JO 5 p a DESCRIPTION g > z= U � } W LU Z F— U_C~7 _ to W N W W Z Z LU o � z W am go o a DU)i Bare soil over SANDY SILTY GRAVEL to GRAVELLY SM S-1 SS 3 SILTY SAND, orange-brown, very loose, wet SANDY SILTY GRAVEL to GRAVELLY 5 SM S-2 SS 2 SILTY SAND, orange-brown,very loose, wet SANDY SILTY GRAVEL to GRAVELLY SM S-3 SS 5 SILTY SAND, orange-brown, loose, wet SANDY SILTY GRAVEL to GRAVELLY 10 SM S-4 SS 10 SILTY SAND, orange-brown, loose to medium dense,wet SANDY SILTY GRAVEL to GRAVELLY SM S-5 SS 5 SILTY SAND, orange-brown, loose, wet SANDY SILTY GRAVEL to GRAVELLY 15 SM S-6 SS 3 SILTY SAND, orange-brown, very loose, wet Driller reports increased gravel at 18.5 feet SANDY SILTY GRAVEL to GRAVELLY 20 SM S-7 SS 14 SILTY SAND, orange-brown, medium dense,wet n :: 25 SANDY SILTY GRAVEL to GRAVELLY SM S-8 SS 30 o SILTY SAND, orange-brown,medium •: dense to dense, wet w . 4 SANDY SILTY GRAVEL to GRAVELLY 30 SM S-9 SS 28 0 31.5 SILTY SAND, orange-brown, medium dense,wet Boring completed at 31.5 feet on 5/7/09. Z No groundwater observed while drilling. a 0 m o The stratification lines represent the approximate boundary lines between soil and rock types: in-situ,the transition may be gradual. 0 w WATER LEVEL OBSERVATIONS, ft Irerracon BORING STARTED 5-7-09 w WL BORING COMPLETED 5-7-09 WL 21905 64th Avenue West,Ste. 100 RIG BK Truck CO. Holocene 0 WL Mountlake Terrace,WA 98043 T:425-771-3304 F:425-771-3549 LOGGED TAJ JOB# 81095036 GRAIN SIZE ANALYSIS Test Results Summary ASTM D 1140,422 SIZE OF OPENING IN INCHES U.S.STANDARD SIEVE SIZE HYDROMETER 36' 12' B' 3' 11/2' 3/4' 3/8' 4 10 20 40 50 10D 20D 10 9 = 8 0 LU 7 } m W6 Z CL E— 5 Z LU iJ LU 4 IL 3 2 1 1000.000 100.000 10.000 1.000 0.100 0.010 0.001 PARTICLE SIZE IN MILLIMETERS Coarse Fine Coarse Medium Fine Sllt Clay BOULDERS COBBLES GRAVEL SAND FINE GRAINED Comments: Exploration Sample Depth (feet) Moisture (%) Fines (%) Description B-1 S-1 0-1.5' 32 27.7 gravelly silty SAND with trace clay PROJECT NO: J-1592 PROJECT NAME: Zinser Zeman Associates, Inc. DATE OF TESTING: 4117103 North Mountain Tower Geotechnical and Environmental Consulting GRAIN SIZE ANALYSIS Test Results Summary ASTM D 1140,422 SIZE OF OPENING IN INCHES U.S.STANDARD SIEVE SIZE HYDROMETER 36' 12' 6' 3' 11/2' 314' 3/6' 4 10 20 40 50 100 200 10 9 2 8 W 7 m � 6 W Z LL Z5 W V W 4 COL. 3 2 1 1000.000 100.000 10.000 1.000 0.100 0.010 0.001 PARTICLE SIZE IN MILLIMETERS Coarse Fine Coarse Medium Flne Sllt Clay BOULDERS COBBLES GRAVEL SAND FINE GRAINED Comments: Exploration Sample Depth (feet) Moisture (%) Fines(%) Description B-2 S-4 20 21.5' 34 39.7 silty SAND with trace clay&some gravel PROJECT NO: J-1592 PROJECT NAME: Zipper Zeman Associates' Inc. DATE OF TESTING: 4/17/03 North Mountain Tower Geotechnical and Environmental Consulting GRAIN SIZE ANALYSIS Test Results Summary ASTM D 1140,422 SIZE OF OPENING IN INCHES U.S.STANDARD SIEVE SIZE HYDROMETER 36. 12' 6' 3' 11/2' 3/4' 318' 4 10 20 40 50 100 200 10 9 = 80 0 W �S 7 } m W 6 W Z LL F- 5 Z W C� W 4 a- 30 2 1 1000.000 100.000 10.000 1.000 0.100 0.010 0.001 PARTICLE SIZE IN MILLIMETERS Coarse Fine Coarse Medium Fine Silt Clay BOULDERS COBBLES GRAVEL SAND FINE GRAINED Comments: Exploration Sample Depth (feet) Moisture (%) Fines(%) Description B-3 S-3 12.5-14' 20 28.6 gravelly silty SAND with trace clay Zipper Zeman Associates, Inc. PROJECT NO: J-1592 PROJECT NAME: DATE OF TESTING: 4/17/03 North Mountain Tower Geotechnical and Environmental Consulting MASON COUNTY Submittal checklist COMMUNITY SERVICES Geological Assessment Bullding,Planning.Environmental Health,Community Health Instructions: This checklist must be submitted with a Geological Assessment and completed, signed, and stamped by the licensed professional(s)who prepared the Geological Assessment 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 ws Fl Noe,ti &A)( Rio 0L,A 4t...,.i-Lt,Parcel# 5;L -s -3o -DOD o0 Site Address 6001 w, s;.., as9K 805 Rok tt Ske14�—EI (1) A discussion of geologic conditions in the general vicinity of the proposed development,with geologic unit designation based on referenced maps. Located on page(s) (2) (a)A discussion of the ground water conditions at the site, Located on page(s) L1 (b) A discussion of the estimated depth to water, Located on page(s) 4 (c) A discussion of the quantity of surface seepage, Located on page(s) ,Z (d) A discussion of the upslope geomorphology, Located on page(s) I—02 (e) A discussion of location of upland waterbodies and wetlands. Located on page(s) 1 - o` (3) The approximate depth to hard or dense competent soil,e.g.glacial till or outwash sand. Located on page(s) 3 (4) A discussion of any geomorphic expression of past slope instability(presence of hummocky ground or ground cracks,terraced topography indicative of landslide block movement, bowed or arched trees indicating downslope movement, etc.). Located on page(s) oZ (5) A discussion of the history of landslide activity in the vicinity, as available in the referenced maps and records. Located on page(s) .5 (6) An opinion on whether the proposed development is within the landslide hazard area or its associated buffer or setback and the potential for landslide activity at the site in light of the proposed development. Located on page(s) 5-6 (7) A recommendation by the preparer whether a Geotechnical Report should be required to further evaluate site conditions and the proposed development of the subject property. Rev.February 2018 Located onpage(s) NA bte4tcl.r.: �11 rt or{-T pa•-cd. (8) If the presence of a hazard is determined within 300 feet of the proposed development, then the following are delineated on a geologic map/site map: (a) the area of the proposed development, Located on Map(s) F?q is /- 7 (b) the boundaries of the landslide hazard area (top, both sides, and toe), Located on Map(s) F I H r t. Z (c) the associated buffers (top, both sides, and toe), Located on Map(s) Fi A "v e- Z (d) building or other setbacks(top, both sides, and toe). Located on Map(s) F;,,., r (9) 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) t 2 1, TIC n w. A. Jo c 5 hereby certify under penalty of perjury that I am a civil engineer licensed in the State of Washington with specialized knowledge of geotechnical/geological 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 Geological Assessment, dated AL. M k t+ 13 �-ol 4 and entitled AfoosrtTeVa CTEA A/e/*k 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 landslide hazard can be mitigated through the included geotechnical design recommendations, and that all hazards are mitigated in such a manner as to prevent harm to property and public health and safety. s o A � IQIPAL (Signature and Stamp) Page 2 of 2 Disclaimer.Mason County does not certify the quality of the work done in this Geological Assessment.