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Home My WebLink AboutRS_Geotechnical_Report_Soils_240826_v1.pdfassociated earth sciences incorporated Associated Earth Sciences, Inc. www.aesgeo.com Kirkland | Mount Vernon | Tacoma Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report HAZEN HIGH SCHOOL MODERNIZATION Renton, Washington Prepared For: RENTON SCHOOL DISTRICT NO. 403 Project No. 20210251E003 August 26, 2024 Kirkland | Tacoma | Mount Vernon 425-827-7701 | www.aesgeo.com August 26, 2024 Project No. 20210251E003 Renton School District No. 403 7812 South 124th Street Seattle, Washington 98178 Attention: Mike Cato, P.E. Subject: Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report Hazen High School Modernization 1101 Hoquiam Avenue NE Renton, Washington Dear Mr. Cato: We are pleased to present this copy of our geotechnical engineering report for the referenced project. This report summarizes the results of our subsurface exploration, geologic hazard, and geotechnical engineering evaluation, and contains our geotechnical design recommendations for the proposed project. We have reviewed the 100% Design Development set and the plans have accurately incorporated the recommendations presented in this report. If any design changes are made, we recommend that we be allowed to review the recommendations in this report and modify them as necessary. We have enjoyed working with you on this study and are confident that the recommendations presented in this report will aid in the successful completion of your project. If you should have any questions, or if we can be of additional help to you, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington ______________________________ G. Bradford Drew, P.E. Associate Engineer BD/ld – 20210251E003-002 SUBSURFACE EXPLORATION, GEOLOGIC HAZARD, AND GEOTECHNICAL ENGINEERING REPORT HAZEN HIGH SCHOOL MODERNIZATION Renton, Washington Prepared for: Renton School District No. 403 7812 South 124th Street Seattle, Washington 98178 Prepared by: Associated Earth Sciences, Inc. 911 5th Avenue Kirkland, Washington 98033 425-827-7701 August 26, 2024 Project No. 20210251E003 Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 1 I. PROJECT AND SITE CONDITIONS 1.0 INTRODUCTION This report presents the results of Associated Earth Sciences, Inc.’s (AESI’s) subsurface exploration, geologic hazard assessment, and geotechnical engineering recommendations for the proposed building renovations and structural alterations to the existing Hazen High School campus in Renton, Washington. Our understanding of the project at the time of fieldwork was based on email correspondence with the design team and our review of conceptual markups indicated on the “Hazen High School Modernization Existing Plan - Level 1,” prepared by Integrus Architecture, dated January 9, 2024. The site location is shown on the “Vicinity Map,” Figure 1. The approximate locations of explorations completed for this study relative to existing and proposed site features are shown on the “Existing Site and Exploration Plan,” Figure 2. Interpretive exploration logs of subsurface explorations completed for this study are included in Appendix A. 1.1 Purpose and Scope The purpose of this study was to provide subsurface data and geotechnical engineering design recommendations to be utilized in the development and design of the project. Our study included reviewing available geologic literature, advancing six exploration borings, and performing geologic studies to assess the type, thickness, distribution, and physical properties of the subsurface sediments and shallow groundwater at the site. Geotechnical engineering studies were completed to formulate recommendations for site preparation, temporary cut slopes, erosion control, structural fill, building foundations, seismic site class, floor slabs, and site drainage. This report summarizes our current fieldwork and offers recommendations based on our present understanding of the project. We recommend that we be allowed to review the recommendations presented in this report and revise them, if needed, when a project design has been finalized. 1.2 Authorization Authorization to proceed with this study was granted by means of an agreement for Consulting Services issued by Renton School District No. 403 and executed on December 19, 2023. Our study was accomplished in general accordance with our proposal, dated December 12, 2023. This report has been prepared for the exclusive use of Renton School District No. 403 and their authorized agents for specific application to this project. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering and engineering geology practices in effect in this area at the time our report was prepared. No other warranty, express or implied, is made. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 2 2.0 PROJECT AND SITE DESCRIPTION The project site is located at the existing Hazen High School in Renton, Washington (Figure 1). We understand the existing school campus was originally constructed in 1969 and includes several classroom buildings near the center of the site with parking lots and driveways surrounding the buildings and grass athletic fields to the west and south. The site has been graded to its current configuration by past earthwork onsite. Topography across the site is generally flat to gently sloping down to the west with an overall vertical relief of less than 10 feet across the footprint of the main school buildings. The project involves the modernization of the existing school buildings including structural seismic upgrades and interior renovations. We understand that modernization elements will include the addition of shear walls, columns, footings, and other structural elements to meet current seismic requirements under the 2021 International Building Code (IBC). Details of the modernization elements were still in progress at the time of this report. We understand that all buildings are currently supported on conventional shallow foundations consisting of spread and strip footings. We understand that foundation improvements are focused near the central-eastern portion of the campus buildings with improvements also planned at the south end of the natatorium building. These areas are outlined on Figure 2. We anticipate that earthwork activities will be minimal for this project as building alterations and foundation improvements will be conducted inside of and/or adjacent to the existing building footprint. 3.0 PREVIOUS EXPLORATIONS AESI previously completed a total of 17 explorations at the school campus in 2009, 2021, and 2022. The approximate locations of our previous explorations onsite are shown on Figure 2, and copies of the exploration logs are included in Appendix B. In addition to previous work completed by AESI, the State of Washington completed a subsurface shear wave transmission velocity survey at the site in October 2020. Additional information regarding that study is included in the “Ground Motion/Seismic Site Class” section of this report. The previous explorations completed by AESI include:  Five borings (EB-1 through EB-5, completed in May 2009) located north of the existing natatorium for a new classroom addition. Borings EB-1 through EB-5 were advanced to a depth of about 21.5 feet below site grade. These borings generally encountered about 7 feet of existing fill overlying native soils that included a variable presence/thickness of medium dense recessional outwash, medium dense to dense ice-contact sediments, and Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 3 dense glacial till and/or hard silt at depth. Perched groundwater was encountered above the glacial till and hard silt at depths of 10 to 15 feet in early May.  One boring (EB-1, completed in October 2021) located to the west of the existing natatorium for the pool modernization project. This boring was advanced to a depth of 21.5 feet below existing site grade and encountered about 5 feet of existing fill overlying medium dense recessional outwash to 12 feet and dense glacial till to the termination depth of 21.5 feet. Perched groundwater was encountered above the glacial till at about 8 feet below existing grade in late October.  Eleven borings (EB-1 through EB-11, completed in March 2022) located within the northern parking lot areas and drive lanes for the parking lot upgrades project. These borings were shallow and extended to depths of 3 to 5 feet below parking lot grades. Most of these borings encountered existing fill to the termination depth. Three of the borings (EB-1, EB-5, and EB-6) encountered native recessional outwash sediments at depths of 1 to 2 feet below parking lot grades. 4.0 SUBSURFACE EXPLORATION Our field study was conducted for this project on January 2, 2024 and included advancing six exploration borings (EB-1 through EB-6) around the perimeter of the school near the locations of the planned improvements (see Figure 2) The conclusions and recommendations presented in this report are based, in part, on the explorations completed for this study. The number, locations, and depths of the explorations were completed within site and budgetary constraints. Because of the nature of exploratory work below ground, extrapolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this report and make appropriate changes. 4.1 Exploration Borings The exploration borings for this phase of the project were completed by Geologic Drill Partners, Inc., an independent firm working under subcontract to AESI, at the locations shown on Figure 2. The borings were completed by advancing a 6-inch outside-diameter, hollow-stem auger with a track-mounted drill rig. During the drilling process, samples were obtained at generally 2.5- to 5-foot-depth intervals. After completion of drilling, each borehole was backfilled with bentonite chips, and the surface was patched with the excavated soil in landscape areas and with asphalt cold patch in pavement areas. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 4 Disturbed but representative samples were obtained by using the Standard Penetration Test (SPT) procedure. This test and sampling method consists of driving a 2-inch outside-diameter, split-barrel sampler a distance of 18 inches into the soil with a 140-pound hammer free-falling a distance of 30 inches. The number of blows for each 6-inch interval is recorded, and the number of blows required to drive the sampler the final 12 inches is known as the Standard Penetration Resistance (“N”) or blow count. If a total of 50 is recorded within one 6-inch interval, the blow count is recorded as the number of blows for the corresponding number of inches of penetration. The resistance, or N-value, provides a measure of the relative density of granular soils or the relative consistency of cohesive soils; these values are plotted on the attached exploration boring logs. The exploration borings were continuously observed and logged by a geologist from our firm. The samples obtained from the split-barrel sampler were classified in the field and representative portions placed in watertight containers. The samples were then transported to our laboratory for further visual classification and laboratory testing, as necessary. The exploration logs presented in Appendix A are based on the N-values, field observations, and drilling action. 5.0 SUBSURFACE CONDITIONS Subsurface conditions at the project site were inferred from the field explorations accomplished for this study, our visual reconnaissance of the site, and review of selected geologic literature. The various types of sediments, as well as the depths where the characteristics of the sediments changed, are indicated on the exploration logs presented in Appendix A. The depths indicated on the logs where conditions changed may represent gradational variations between sediment types. If changes occurred between sample intervals in our exploration borings, they were interpreted. The exploration borings completed for this study generally encountered existing fill soils overlying Vashon ice-contact sediments, Vashon lodgement till, Vashon advance outwash (lacustrine) and/or pre-Fraser sediments observed at depth depending on location. The following section presents more detailed subsurface information organized from the shallowest (youngest) to the deepest (oldest) sediment types. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 5 5.1 Site Stratigraphy Asphalt Asphalt was encountered at the surface of exploration EB-3. The asphalt layer was approximately 3 inches in thickness. Topsoil/Mulch We encountered 2 to 3 inches of sod and topsoil at the ground surface in borings EB-1 and EB-2, and 4 to 6 inches of bark/mulch in EB-4 through EB-6. Fill Directly below the asphalt and topsoil/mulch, all borings encountered fill soils (those not naturally placed) to depths ranging from approximately 3 to 4.5 feet below the existing ground surface, except the fill in EB-2 was observed to extend deeper to about 8.5 feet below the ground surface. The fill generally consisted of loose to medium dense, moist, brown to dark brown with occasional orange oxidation staining, silty, fine to medium sand with variable gravel content and scattered to abundant organics (roots/rootlets/fine black organics). Due to the inherent variability of the fill and unknown placement and compaction methods, the fill soils are not considered suitable for direct foundation support and may require remedial measures for support of new hardscapes and slabs-on-grade. Excavated fill material may be suitable for reuse in structural fill applications if such reuse is specifically allowed by project plans and specifications, if excessively organic and any other deleterious materials are removed, and if moisture content is adjusted to allow compaction to the specified level and to a firm and unyielding condition. Fill soils are also likely present in unexplored areas of the site near the existing buildings, within existing utility trenches, and below previously graded/backfilled areas. Vashon Ice Contact Below the existing fill, exploration borings EB-1, EB-3, EB-4, and EB-5 encountered medium dense to dense sand with variable silt content ranging from trace to silty, and stiff to hard silt and sandy silt. These native sediments are interpreted to be representative of Vashon ice-contact sediments and extended to depths of 6.5 to 13.5 feet below the ground surface. Ice-contact sediments were deposited above, adjacent, or within a glacial ice mass and may have been redeposited as the ice melted or was reworked by the ice. Ice-contact sediments can have variable density and grain size and range from stratified to massive; stratification was observed in some of the samples. Some of the ice-contact sediments observed in our exploration borings contained large quantities Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 6 of silt and are considered highly moisture-sensitive. These sediments are suitable for foundation support with proper preparation. We noted a faint petroleum odor was encountered in a sample obtained from 5 to 6.5 feet within EB-3, near the contact between the existing fill and underlying ice-contact sediments. We are available to assist with additional explorations and analytical testing should earthwork be performed in this area or desired by the Owner. Vashon Lodgement Till Directly below the Vashon ice-contact deposits, explorations EB-4 and EB-5 encountered very dense, moist, brown, silty fine sand with some gravel to the termination depth of both borings at about 11 feet. We interpreted these sediments to be representative of Vashon lodgement till. The Vashon lodgement till was deposited by basal, debris-laden, glacial ice during the Vashon Stade of the Fraser Glaciation, approximately 12,500 to 15,000 years ago. The high relative density characteristic of the Vashon lodgement till is due to its consolidation by the massive weight of the glacial ice from which it was deposited. Consequently, lodgement till soils are typically dense to very dense and possess high-shear strength and low-compressibility and low-permeability characteristics. The lodgement till soils are favorable for support of foundations with proper preparation. Lodgement till soils are generally suitable for structural fill applications provided that these materials are placed and compacted at or near optimum moisture content. Vashon Advance Outwash (Lacustrine) Below the ice-contact sediments in EB-1 and EB-3 and below the existing fill in EB-2, we encountered massive to faintly bedded, dense to very dense, very moist to wet, sand and silty sand ranging to hard silt and sandy silt. Based on the density, grain-size distribution, stratification of samples observed and lack of organic sediments, we interpret this unit to be Vashon advance outwash deposited in a lacustrine (low-energy) environment. Vashon advance outwash sediments were deposited in front of an advancing ice sheet and were subsequently overridden. These sediments typically possesses high-strength and low-compressibility attributes that are favorable for support of foundations with proper preparation. The advance outwash sediments extended to depths of 11.5 and 23 feet within EB-1 and EB-3, respectively, and to the termination depth of EB-2 at about 16 feet. Pre-Fraser Sediments Below the advance outwash (lacustrine) sediments in EB-1 and EB-3 and below the existing fill in EB-6, we encountered very dense, very moist to wet, sand and silty sand and hard, slightly moist, Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 7 silt with some sand. Due to their density and stratigraphic position, we infer that these sediments are of pre-Fraser age and were deposited prior to the Fraser Glaciation that occurred from 12,500 to 15,000 years before present and have been consolidated by at least one glaciation. The pre-Fraser sediments extended beyond the maximum depths explored of approximately 26 feet, 25.5 feet, and 14.5 feet at EB-1, EB-3, and EB-6, respectively. This unit also possesses high- strength and low-compressibility attributes that are favorable for support of foundations with proper preparation. 5.2 Regional Geologic and Soils Mapping Review of the regional geologic map of the project area (Geologic Map of King County, Washington, by Derek B. Booth, Kathy A. Troost, and Aaron P. Wisher, GeoMapNW, 2007) indicates that the site vicinity is underlain by Vashon lodgement till with Vashon advance outwash exposed offsite to the northeast. The shallow native sediments observed in our explorations for this study are in partial agreement with this mapping in that we encountered Vashon lodgement till at depth within EB-4 and EB-5 and Vashon advance outwash (lacustrine) at depth within EB-1, EB-2, and EB-3. Directly below the existing fill, we encountered geologic units not depicted on the map which included Vashon ice-contact sediments above the lodgement till and advance outwash in EB-1, EB-3, EB-4, and EB-5, and pre-Fraser fine-grained sediments in EB-6 to the termination depth. 5.3 Hydrology Groundwater was encountered in explorations EB-1 and EB-2 within the Vashon advance outwash (lacustrine) sediments at depths of 7.5 and 10 feet below the existing ground surface at the time of drilling, respectively. We also observed groundwater in EB-3 within the Vashon ice-contact deposits at a depth of 8.5 feet. Where the Vashon advance lacustrine sediments and pre-Fraser sediments were primarily sand, such as EB-1, the water-bearing zone was greater than 15 feet thick and extended beyond the exploration depth. Groundwater elevations in EB-1, EB-2, and EB-3 ranged from about 457.5 to 460.5 feet. No groundwater was encountered in EB-4 and EB-5 which did not encounter the Vashon advance lacustrine sediments, or EB-6 which was located at a slightly higher elevation. Groundwater within the sandy Vashon advance lacustrine and pre-Fraser sediments is interpreted to be perennial. Shallower perched groundwater should also be expected within the fill and silty Vashon ice-contact sediments. Perched groundwater occurs as surface water percolates down through the near-surface, relatively permeable soils, and becomes trapped or “perched” atop underlying, lower-permeable, layers such as silty ice-contact and glacial till sediments. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 8 It should be noted that our explorations were completed in early January when groundwater levels are elevated and possibly rising. Groundwater levels may be higher during the late winter and spring months. The duration and quantity of groundwater seepage can be expected to vary in response to changes in season, precipitation patterns, on- and off-site land usage, site development, and other factors. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 9 II. GEOLOGIC HAZARDS AND MITIGATIONS The following discussion of potential geologic hazards is based on the geologic, slope, and ground and surface water conditions, as observed and discussed herein. The discussion will be limited to landslide, seismic, and erosion hazards. Individual geologic hazard topics are discussed in further detail below. 6.0 LANDSLIDE HAZARDS AND MITIGATIONS Topography across the site is generally flat to gently sloping down to the west with an overall vertical relief of less than 10 feet across the footprint of the existing school buildings. Based on our site reconnaissance and review of Light Detection and Ranging (LIDAR)-based topographic contours as shown on Figure 2, no steep slopes are present within the vicinity of the proposed building improvements. Therefore, it is our opinion that the potential risk of damage to the proposed improvements by landsliding is low and that no mitigation measures are warranted for the project. 7.0 SEISMIC HAZARDS AND MITIGATIONS The following discussion is a general assessment of seismic hazards that is intended to be useful to the project design team in terms of understanding seismic issues, and to the structural engineer for design. All of Western Washington is at risk of strong seismic events resulting from movement of the tectonic plates associated with the Cascadia Subduction Zone (CSZ), where the offshore Juan de Fuca plate subducts beneath the continental North American plate. The site lies within a zone of strong potential shaking from subduction zone earthquakes associated with the CSZ. The CSZ can produce earthquakes up to magnitude 9.0, and the recurrence interval is estimated to be on the order of 500 years. Geologists infer the most recent subduction zone earthquake occurred in 1700 (Goldfinger et al., 20121). Three main types of earthquakes are typically associated with subduction zone environments: crustal, intraplate, and interplate earthquakes. Seismic records in the Puget Sound region document a distinct zone of shallow crustal seismicity (e.g., the Seattle Fault Zone [SFZ]). These shallow fault zones may include surficial expressions of previous seismic events, such as fault scarps, displaced shorelines, and shallow bedrock exposures. The shallow 1 Goldfinger, C., Nelson, C.H., Morey, A.E., Johnson, J.E., Patton, J.R., Karabanov, E., Gutierrez-Pastor, J., Eriksson, A.T., Gracia, E., Dunhill, G., Enkin, R.J., Dallimore, A., and Vallier, T., 2012, Turbidite Event History—Methods and Implications for Holocene Paleoseismicity of the Cascadia Subduction Zone: U.S. Geological Survey Professional Paper 1661–F, 170. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 10 fault zones typically extend from the surface to depths ranging from 16 to 19 miles. A deeper zone of seismicity is associated with the subducting Juan de Fuca plate. Subduction zone seismic events produce intraplate earthquakes at depths ranging from 25 to 45 miles beneath the Puget Lowland including the 1949, 7.2-magnitude event; the 1965, 6.5-magnitude event; and the 2001, 6.8-magnitude event and interplate earthquakes at shallow depths near the Washington coast including the 1700 earthquake, which had a magnitude of approximately 9.0. The 1949 earthquake appears to have been the largest in this region during recorded history and was centered in the Olympia area. Evaluation of earthquake return rates indicates that an earthquake of the magnitude between 5.5 and 6.0 is likely within a given 20-year period. Generally, there are four types of potential geologic hazards associated with large seismic events: 1) surficial ground rupture, 2) seismically induced landslides or lateral spreading, 3) liquefaction, and 4) ground motion. The potential for each of these hazards to adversely impact the proposed project is discussed below. 7.1 Surficial Ground Rupture Seattle Fault Zone The site is located approximately 1 mile south of the mapped limits of the SFZ. The SFZ is a broad east-west oriented zone that extends from approximately Issaquah to Alki Beach, and is approximately 2.5 to 4 miles in width from north to south. The SFZ is speculated to contain multiple distinct fault “strands,” some of which are well understood and some of which may be poorly understood or unknown. Mapping of individual fault strands is imprecise, as a result of pervasive modification of the land surface by development, which has obscured possible surficial expression of past seismic events. Studies by the U.S. Geological Survey (USGS) and others have provided evidence of surficial ground rupture along strands of the SFZ (USGS, 20102; Pratt et al., 20153; Haugerud, 20054; Liberty et al., 20085). According to USGS studies the latest movement of this fault was about 1,100 years ago when about 20 feet of surficial displacement took place. This displacement can presently be seen in the form of raised, wave-cut beach terraces along Alki Point in West Seattle and Restoration Point at the south end of Bainbridge Island. Based on our review of the Washington State Department of Natural Resources (WADNR) website, inferred fault traces associated with the SFZ are located about 1 mile north of the site. Due to the 2 U.S. Geological Survey, 2010, Quaternary Fault and Fold Database for the United States, accessed November 10, 2010, from USGS web site: http://earthquake.usgs.gov/hazards/qfaults/. 3 Pratt et al., 2015, Kinematics of Shallow Backthrusts in the Seattle Fault Zone, Washington State: Geosphere, v. 11, no. 6, p. 1-27). 4 Haugerud, R.A., 2005, Preliminary Geologic Map of Bainbridge Island, Washington: U.S. Geological Survey Open-File Report 2005-1387, version 1.0, 1 sheet, scale 1:24,000. 5 Liberty, Lee M.; Pratt, Thomas L., 2008, Structure of the Eastern Seattle Fault Zone, Washington State - New Insights from Seismic Reflection Data: Bulletin of the Seismological Society of America, v. 98, no. 4, p. 1681-1695. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 11 suspected long recurrence interval, and the distance of the site to the fault traces, the potential for surficial ground rupture along the SFZ is considered to be low during the expected life of the proposed improvements. 7.2 Seismically Induced Landslides Similar to the discussion in Section 6.0, “Landslide Hazards and Mitigations,” it is our opinion that the potential risk of damage to the proposed improvements by seismically induced slope failures is low and that no mitigation measures are warranted for the project due to the lack of steep slopes in the immediate project area. 7.3 Liquefaction Liquefaction is a process through which unconsolidated soil loses strength as a result of vibrations, such as those which occur during a seismic event. During normal conditions, the weight of the soil is supported by both grain-to-grain contacts and by the fluid pressure within the pore spaces of the soil below the water table. Extreme vibratory shaking can disrupt the grain-to-grain contact, increase the pore pressure, and result in a temporary decrease in soil shear strength. The soil is said to be liquefied when nearly all of the weight of the soil is supported by pore pressure alone. Liquefaction can result in deformation of the sediment and settlement of overlying structures. Areas most susceptible to liquefaction include those areas underlain by very soft to stiff, non-cohesive silt and very loose to medium dense, non-silty to silty sands with low relative densities, accompanied by a shallow water table. The site is generally underlain by unsaturated existing fill overlying medium dense to very dense native sediments at relatively shallow depths. Where native sediments are saturated, they are typically dense to very dense and not considered susceptible to liquefaction. In our opinion, the potential risk of damage to the proposed improvements by liquefaction is low. No detailed liquefaction hazard analysis was performed as part of this study, and none is warranted, in our opinion. 7.4 Ground Motion/Seismic Site Class It is our opinion that earthquake damage to the proposed school improvements, when founded on suitable bearing strata in accordance with the recommendations contained herein, will likely be caused by the intensity and acceleration associated with the event. We understand that structural design of the building improvements will follow the 2021 IBC standards. Based on the subsurface conditions encountered within our exploration borings, we recommend using Site Class “C” as defined in Table 20.3-1 of American Society of Civil Engineers (ASCE) 7-16 Minimum Design Loads and Associated Criteria for Buildings and Other Structures. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 12 It should be noted that the Washington Geological Survey (WGS) conducted a seismic survey at the project site on October 22, 2020. The seismic survey was completed with an array of 48 geophones approximately 308 feet in length to measure the shear wave velocity within the upper 100 feet of soil. This array was located at the northwest corner of the campus near the existing ballfield. The average shear wave velocity was measured at 376 meters per second, which corresponds to Site Class C, near the C/D border. The shear wave velocity results are included in Appendix C. 8.0 EROSION HAZARDS AND MITIGATIONS The sediments underlying the site generally consist of fine to medium sand with varying amounts of silt and gravel. Where exposed to rain and wind, these sediments will be susceptible to erosion and off-site sediment transport when exposed during construction. We anticipate that construction will be contained within the existing building footprint and that earthwork will largely involve trench excavations for new footings. The project should follow best management practices (BMPs) to mitigate erosion hazards and potential for off-site sediment transport. To mitigate the potential for off-site sediment transport, we recommend the following: 1. The winter performance of a site is dependent on a well-conceived plan for control of site erosion and stormwater runoff. The project temporary erosion and sediment control (TESC) should include ground-cover measures, access roads, and staging areas. The contractor must implement and maintain the required measures. 2. TESC measures for a given area, to be graded or otherwise worked, should be installed prior to any activity within that area. The recommended sequence of construction within a given area would be to install sediment traps and/or ponds and establish perimeter flow control prior to starting earthwork. 3. During the wetter months of the year, or when large storm events are predicted during the summer months, each work area should be stabilized so that if precipitation occurs, the work area can receive the rainfall without excessive erosion or sediment transport. The required measures for an area to be “buttoned-up” will depend on the time of year and the duration the area will be left unworked. During the winter months, areas that are to be left unworked for more than 2 days should be mulched or covered with plastic. During the summer months, stabilization will usually consist of seal-rolling the subgrade. Such measures will aid in the contractor’s ability to get back into a work area after a storm event. The stabilization process also includes establishing temporary stormwater conveyance channels through work areas to route runoff to the approved treatment facilities. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 13 4. All disturbed areas should be revegetated as soon as possible. If it is outside of the growing season, the disturbed areas should be covered with mulch, or as recommended in the erosion control plan. Straw mulch provides a cost-effective cover measure and can be made wind-resistant with the application of a tackifier after it is placed. 5. Surface runoff and discharge should be controlled during and following development. Uncontrolled discharge may promote erosion and sediment transport. Soils that are to be reused around the site should be stored in such a manner as to reduce erosion from the stockpile. Protective measures may include, but are not limited to, covering with plastic sheeting, the use of low stockpiles in flat areas, or the use of straw bales/silt fences around pile perimeters. It is our opinion that with the proper implementation of the TESC plans and by field-adjusting appropriate mitigation elements (BMPs) throughout construction, the potential for adverse impacts from erosion hazards on the project may be mitigated. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 14 III. DESIGN RECOMMENDATIONS 9.0 INTRODUCTION Our explorations indicate that, from a geotechnical engineering standpoint, the proposed building renovations and structural alterations are feasible provided the recommendations contained herein are properly followed. At the locations explored, we encountered a surficial layer of existing fill underlain by medium dense to very dense native sediments. The native sediments will provide suitable support for conventional spread and strip footings. The existing fill soils are not considered suitable for direct foundation support and may require remedial measures for support of hardscapes and slabs-on-grade. The following sections provide our recommendations for site preparation, temporary cut slopes, structural fill, foundation support, lateral earth pressures on retaining walls, drainage considerations, and slab-on-grade support. 10.0 SITE PREPARATION Erosion and surface water control should be established around the perimeter of the excavation to satisfy City of Renton requirements. After any required demolition is complete, disturbed soils below finished grade should be removed. Existing fill should be removed from below the building foundations until suitable native soils are exposed, and the fill removal should extend laterally at least 2 feet beyond the footing limits. The resulting surface should then be compacted before placing structural fill, as necessary, to reach planned grades. 10.1 Site Disturbance The existing fill and native soils onsite contain substantial quantities of fine-grained material (silt) and are considered to be highly moisture-sensitive. Sediments containing more than approximately 5 percent fines (silt and clay) will be moisture-sensitive and subject to disturbance when wet. The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs, the softened soils should be removed and the area brought to grade with structural fill. 10.2 Temporary Cut Slopes In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction. For estimating purposes, however, we anticipate that temporary, unsupported cuts into the existing fill or native soils can be made near vertical to a Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 15 maximum depth of 4 feet. If excavations greater than 4 feet are required, then temporary, unsupported cut slopes can be planned at maximum inclinations of 1.5H:1V (Horizontal:Vertical) in existing fill and medium dense to dense native sediments. These slope angles are for areas where groundwater seepage is not present at the faces of the slopes. If groundwater or surface water is present when the temporary excavation slopes are exposed, flatter slope angles may be required. As is typical with earthwork operations, some sloughing and raveling may occur, especially if groundwater seepage is present in the excavation cuts, and cut slopes may have to be adjusted in the field. In addition, WISHA/OSHA regulations should be followed at all times. 11.0 STRUCTURAL FILL We anticipate that placement of structural fill may be necessary to establish desired grades at the site and for backfilling around foundation elements. All references to structural fill in this report refer to subgrade preparation, fill type, and placement and compaction of materials as discussed in this section. 11.1 Subgrade Compaction In areas that will receive structural fill, the upper 12 inches of exposed subgrade should be recompacted to a firm and unyielding condition. If the subgrade contains too much moisture, suitable recompaction may be difficult or impossible to attain and should probably not be attempted. In lieu of recompaction, the area to receive fill should be blanketed with washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the exposed ground remains soft and further overexcavation is impractical, placement of an engineering stabilization fabric may be necessary to prevent contamination of the free-draining layer by silt migration from below. After recompaction of the exposed ground is tested and approved, or a free-draining rock course is laid, structural fill may be placed to attain desired grades. 11.2 Structural Fill Compaction Structural fill is defined as non-organic soil, acceptable to the geotechnical engineer, placed in maximum 8-inch loose lifts, with each lift being compacted to at least 95 percent of the modified Proctor maximum dry density using ASTM International (ASTM) D-1557 as the standard. Utility trench backfill should be placed and compacted in accordance with applicable municipal codes and standards. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 16 11.3 Use of On-Site Soils as Structural Fill The existing fill and native sediments consisting primarily of sand and silty sand are suitable for use as structural fill provided the soil is free of roots or other deleterious materials and have a moisture content suitable for achieving the specified compaction. At the time of our exploration, the moisture content for the majority of the near-surface fill and native sediments encountered in our explorations appeared to be near or above optimum for achieving suitable compaction and will likely require drying. On-site sediments consisting primarily of silt and sandy silt are not considered suitable for use as structural fill due to the high silt content and high sensitivity to moisture which may lead to unstable conditions with elevated moisture and disturbance. The presence and thickness of the fine-grained sediments was variable between our explorations. Silt and sandy silt were encountered within EB-2 at 12.5 feet to the termination depth of 16.5 feet, EB-4 at 6.5 to 9.5 feet, EB-5 at 4.5 to 6.5 feet, and EB-6 at 6 to 12 feet. Soils in which the amount of fine-grained material (smaller than No. 200 sieve) is greater than approximately 5 percent (measured on the minus No. 4 sieve size) should be considered moisture-sensitive. The existing fill and native soils contain a substantial amount of silt and are considered highly moisture-sensitive. These soils may require moisture-conditioning before use as structural fill. Good construction practices and erosion control measures will be necessary to protect the fine-grained soils and prevent over-optimum moisture conditions from developing. If structural fill is placed during wet weather or if proper compaction cannot be obtained, a select import material consisting of a clean, free-draining gravel and/or sand should be used. Free-draining fill consists of non-organic soil, with the amount of fine-grained material (silt and clay) limited to 5 percent by weight when measured on the minus No. 4 sieve fraction, and at least 25 percent retained on the No. 4 sieve. 11.4 Structural Fill Testing Compaction testing will likely be required by the City of Renton. We recommend that a representative from our firm observe the subgrades and be present during placement of structural fill to observe the work and perform a representative number of in-place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses and any problem areas may be corrected at that time. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 17 12.0 FOUNDATIONS Based on the explorations completed for this study, native sediments that are suitable for support of conventional spread and strip footings were encountered at relatively shallow depths ranging from about 3 to 5 feet below the existing ground surface, except at exploration EB-2 the native sediments were deeper at about 8.5 feet. The suitable native sediments encountered at these depths include medium dense to dense ice-contact deposits, dense to very dense advance outwash (lacustrine), and hard pre-Fraser fine-grained sediments. Spread and strip footings may be used for building foundation support when founded either directly on the native sediments described above or on structural fill placed over native sediments after removal of existing fill. If loose ice-contact or other glacially-derived sediments are encountered below planned foundation areas at the time of construction, we recommend that the upper 12 inches of the material be recompacted to a firm and unyielding condition prior to structural fill placement. For footings founded as described above, we recommend using a maximum allowable bearing pressure of 3,000 pounds per square foot (psf) for design purposes, including both dead and live loads. An increase in the allowable bearing pressure of one-third may be used for short-term wind or seismic loading. If structural fill is placed below footing areas, the structural fill should extend horizontally beyond the footing by at least 2 feet. Perimeter footings should be buried at least 18 inches into the surrounding soil for frost protection. However, all foundations must penetrate to the prescribed bearing strata, and no foundations should be constructed in or above loose, organic, or existing fill soils. Anticipated settlement of footings founded as recommended should be less than 1 inch with differential settlement one-half of the anticipated total settlement. Most of this movement should occur during initial dead load applications. However, disturbed material not removed from footing trenches prior to footing placement could result in increased settlements. All footing areas should be observed by AESI prior to placing concrete to verify that the foundation subgrades are undisturbed and construction conforms to the recommendations contained in this report. Foundation bearing verification by AESI will likely be required by the City as a condition of permitting. Perimeter footing drains should be provided as discussed under the “Drainage Considerations” section of this report. It should be noted that the area bounded by lines extending downward at 1H:1V from any footing must not intersect another footing or intersect a filled area that has not been compacted to at least 95 percent of ASTM D-1557. In addition, a 1.5H:1V line extending down and away from any footing must not daylight because sloughing or raveling may eventually undermine the footing. Thus, footings should not be placed near the edges of steps or cuts in the bearing soils. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 18 The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs, the softened soils should be removed and foundations extended down to competent natural soil. If any foundation excavations will occur during the wet season and exposed to rain, consideration should be given to “armoring” the exposed subgrade with a thin layer of rock to provide a working surface during foundation construction. We recommend a 6-inch layer of crushed rock for this purpose. 12.1 Existing Footing Support Because the project will include foundation work on existing buildings, it may be necessary to excavate adjacent to existing footings that are intended to remain in service. We recommend that no excavations be made into the support zone of existing foundations, as defined by a line projected down and away from existing footings at an angle of 1H:1V. If excavation into the support zone of existing footings is required, we should be allowed to offer situation-specific recommendations for foundation underpinning, sequential partial excavations (slot cuts), or other methods to retain support for existing structures. 13.0 FOUNDATION WALLS The following recommendations may be applied to conventional walls up to 5 feet tall. We should be allowed to offer situation-specific input for taller walls. All backfill behind foundation walls or around foundation units should be placed as per our recommendations for structural fill and as described in this section of the report. Horizontally backfilled walls, which are free to yield laterally at least 0.1 percent of their height, may be designed to resist lateral earth pressure represented by an equivalent fluid equal to 35 pounds per cubic foot (pcf). Fully restrained, horizontally backfilled, rigid walls that cannot yield should be designed for an equivalent fluid of 55 pcf. Walls with sloping backfill up to a maximum gradient of 2H:1V should be designed using an equivalent fluid of 55 pcf for yielding conditions or 75 pcf for fully restrained conditions. If parking areas are adjacent to walls, a surcharge equivalent to 250 psf should be added to the wall height in determining lateral design forces. Retaining wall design should include a seismic surcharge pressure in addition to the equivalent fluid pressures presented above. Considering the site soils and the recommended wall backfill materials, we recommend a seismic surcharge pressure of 10H and 15H psf, where H is the wall height in feet for the “active” and “at-rest” loading conditions, respectively. The seismic surcharge should be modeled as a rectangular distribution with the resultant applied at the midpoint of the walls. Surcharges from adjacent footings or heavy construction equipment must be added to the above values. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 19 Perimeter footing drains should be provided for all retaining walls, as discussed under the “Drainage Considerations” section of this report. It is imperative that proper drainage be provided so that hydrostatic pressures do not develop against the walls. 13.1 Passive Resistance and Friction Factors Lateral loads can be resisted by friction between the base of the foundation and the natural soils or supporting structural fill soils and by passive earth pressure acting on the buried portions of the foundations. The foundations must be backfilled with structural fill and compacted to at least 95 percent of the maximum dry density to achieve the passive resistance provided below. We recommend the following allowable design parameters which include a factor of safety of 1.5:  Passive equivalent fluid = 300 pcf  Coefficient of friction = 0.30 14.0 FLOOR SUPPORT Slab-on-grade floors may be constructed directly on native sediments, on structural fill placed over native sediments, or on a minimum of 2 feet of structural fill where deeper existing fill soils are encountered. We recommend that the native sediments and any existing fill to remain in place be recompacted to a firm and unyielding condition prior to placement of the structural fill. All fill placed beneath the slab must be compacted to at least 95 percent of ASTM D-1557. Interior floor slabs should be cast atop a minimum of 4 inches of washed crushed “chip” rock to act as a capillary break. Interior floor slabs should also be protected from dampness by a plastic moisture vapor retarder at least 15 mils thick. The moisture vapor retarder should be placed between the capillary break material and the concrete slab. 15.0 DRAINAGE CONSIDERATIONS Traffic across the on-site soils when they are damp or wet will result in disturbance of the otherwise firm stratum. Therefore, during site work and construction, the contractor should provide surface drainage and subgrade protection, as necessary. Any retaining walls and all perimeter foundation walls should be provided with a drain at the base of the footing elevation. Drains should consist of rigid, perforated, PVC pipe surrounded by washed gravel. The level of the perforations in the pipe should be set at or slightly below the bottom of the footing at all locations and the drains should be constructed with sufficient gradient to allow gravity discharge away from the structures. In addition, any retaining or Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 20 subgrade walls should be lined with a minimum, 12-inch-thick, washed gravel blanket, backfilled completely with free-draining material over the full height of the wall (excluding the first 1 foot below the surface). This drainage aggregate should tie into and freely communicate with the footing drains. Roof and surface runoff should not discharge into the footing drain system, but should be handled by a separate, rigid, tightline drain. Exterior grades adjacent to walls should be sloped downward away from the structures to achieve natural surface drainage. Final exterior grades should promote free and positive drainage away from the buildings at all times. Water must not be allowed to pond or to collect adjacent to the foundation or within the immediate building areas. It is recommended that a gradient of at least 3 percent for a minimum distance of 10 feet from the building perimeter be provided, except in paved locations. In paved locations, a minimum gradient of 1 percent should be provided unless provisions are included for collection and disposal of surface water adjacent to the structures. 16.0 PROJECT DESIGN AND CONSTRUCTION MONITORING We have reviewed the 100% Design Development set and the plans have accurately incorporated the recommendations presented in this report. If any design changes are made, we recommend that we be allowed to review the recommendations in this report and modify them as necessary. The City may require geotechnical special inspections during construction and preparation of a final summary letter when construction is complete. We are available to provide geotechnical engineering services during construction. The integrity of the earthwork and foundations depends on proper site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 21 We have enjoyed working with you on this study and are confident these recommendations will aid in the successful completion of your project. If you should have any questions or require further assistance, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington ______________________________ Brendan C. Young, L.G. Senior Staff Geologist ______________________________ Kurt D. Merriman, P.E. G. Bradford Drew, P.E. Senior Principal Engineer Associate Engineer Attachments: Figure 1: Vicinity Map Figure 2: Existing Site and Exploration Plan Appendix A: Exploration Logs Appendix B: Historical Exploration Logs (AESI 2009, 2021, 2022) Appendix C: Shear Wave Velocity Results (WGS 2020) G:\GIS_Projects\aaY2021\210251 Hazen HS\APRX\E003\20210251E003 F1 VM_HazenHS.aprx | 20210251E003 F1 VM_Hazen HS | 2024-01-24 | mtropCOUNTY LOCALE LOCATION PROJECT NO.DATE FIGURE 11/2420210251E003 HAZEN HIGH SCHOOL MODERNIZATION RENTON, WASHINGTON VICINITY MAP ESRI, USGS, NATIONAL GEOGRAPHIC,DELORME, NATURALVUE, I-CUBED, GEBCO:ARCGIS ONLINE BASEMAP. WADOT STATE ROUTES 24K (12/20). KING CO: PARCELS (4/23), ROADS (5/23). NOTE: LOCATION AND DISTANCES SHOWNARE APPROXIMATE. BLACK AND WHITEREPRODUCTION OF THIS COLOR ORIGINAL MAY REDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION. King County DUVALL AVE NEHOQUIAM AVE NENE 12TH ST NE 10TH STCHELAN AVE NE900 KING COUNTYRENTON NEWCAS T L E RENTONRENTON RENTON NEWCASTLENEWCASTLE 0 2,000 FEET ± SITE BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAY REDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION. LOCATION AND DISTANCES SHOWN ARE APPROXIMATE.G:\GIS_Projects\aaY2021\210251 Hazen HS\APRX\E003\20210251E003 F2 ES_HazenHS.aprx | 20210251E003 F2 ES_HazenHS | 2024-01-24 | mtropPROJECT NO.DATE FIGURE ± 21/2420210251E003 HAZEN HIGH SCHOOL MODERNIZATION RENTON, WASHINGTON EXISTING SITE AND EXPLORATION PLAN DATA SOURCES/REFERENCES: KING COUNTY: ROADS (5/23), PARCELS (4/23). EAGLEVIEW TECHNOLOGIES, INC.: AERIAL IMAGERY (2021). WA DNR LIDAR: KING_COUNTY_WEST_2021, ACQUIRED 4/21, 1.5' CELL SIZE. CONTOURS DERIVED FROM LIDAR. 0 150 FEETDuvall Ave NEHoquiam Ave NENE 10th St NE 12th St NE 12th St NE 11th Pl NE 11th Ct NE 10th St NE 10th Pl NE 11th St Duvall Pl NEEB-1 EB-1 EB-2 EB-3 EB-4 EB-5 EB-1 EB-2 EB-3 EB-4 EB-5 EB-6 EB-7 EB-8 EB-9 EB-10 EB-11 EB-1 EB-2 EB-3 EB-4 EB-5 EB-6 HAZEN HIGH SCHOOL 470460450440430420460 450 480 470 46 0 450 450440470 470470 440440LEGEND SITE EXPLORATION BORING, 2024 EXPLORATION BORING, 2022 EXPLORATION BORING, 2021 EXPLORATION BORING, 2009 FOUNDATION WORK POTENTIAL FOUNDATION WORK CONTOUR 10 FT CONTOUR 2 FT PARCEL APPENDIX A Exploration Logs Classifications of soils in this report are based on visual field and/or laboratory observations, which include density/consistency, moisture condition, grain size, and plasticity estimates and should not be construed to imply field or laboratory testing unless presented herein. Visual-manual and/or laboratory classification methods of ASTM D-2487 and D-2488 were used as an identification guide for the Unified Soil Classification System. OH PT CH OL MH CL ML SM SC GW SP GC SW GM GP Well-graded gravel and gravel with sand, little to no fines Poorly-graded gravel and gravel with sand, little to no fines Clayey gravel and clayey gravel with sand Silty gravel and silty gravel with sand Well-graded sand and sand with gravel, little to no fines Poorly-graded sand and sand with gravel, little to no fines Clayey sand and clayey sand with gravel Organic clay or silt of low plasticity Organic clay or silt of medium to high plasticity Peat, muck and other highly organic soils Silty sand and silty sand with gravel Silt, sandy silt, gravelly silt, silt with sand or gravel Clay of low to medium plasticity; silty, sandy, or gravelly clay, lean clay Elastic silt, clayey silt, silt with micaceous or diatomaceous fine sand or silt Clay of high plasticity, sandy or gravelly clay, fat clay with sand or gravel(1)HighlyOrganicSoilsFine-Grained Soils - 50% or More Passes No. 200 Sieve(1)Coarse-Grained Soils - More than 50% Retained on No. 200 SieveGravels - More than 50% of Coarse FractionRetained on No. 4 Sieve12% Fines5% FinesSands - 50% or More of Coarse FractionPasses No. 4 SieveSilts and ClaysLiquid Limit Less than 50Silts and ClaysLiquid Limit 50 or More(1)(1)12% Fines5% Fines(2)(2)(2)(2)Terms Describing Relative Density and Consistency Estimated Percentage Moisture Content Percentage by Weight <5 5 to <12 12 to <30 30 to <50 Component Definitions Component Trace Some Modifier (silty, sandy, gravelly) Very modifier (silty, sandy, gravelly) Size Range and Sieve Number Larger than 12" Descriptive Term Smaller than No. 200 (0.075 mm) 3" to 12" Coarse- Grained Soils Fine- Grained Soils Density Very Loose Loose Medium Dense Dense Very Dense SPT blows/foot 0 to 4 4 to 10 10 to 30 30 to 50 >50 (3) 0 to 2 2 to 4 4 to 8 8 to 15 15 to 30 >30 Consistency Very Soft Soft Medium Stiff Stiff Very Stiff Hard SPT blows/foot(3) Test Symbols No. 4 (4.75 mm) to No. 200 (0.075 mm) Boulders Silt and Clay Gravel Coarse Gravel Fine Gravel Cobbles Sand Coarse Sand Medium Sand Fine Sand Dry - Absence of moisture, dusty, dry to the touch Slightly Moist - Perceptible moisture Moist - Damp but no visible water Very Moist - Water visible but not free draining Wet - Visible free water, usually from below water table G = Grain Size M = Moisture Content A = Atterberg Limits C = Chemical DD = Dry Density K = Permeability No. 4 (4.75 mm) to No. 10 (2.00 mm) No. 10 (2.00 mm) to No. 40 (0.425 mm) No. 40 (0.425 mm) to No. 200 (0.075 mm) 3" to No. 4 (4.75 mm) 3" to 3/4" 3/4" to No. 4 (4.75 mm) Symbols Sampler Type and Description Blows/6" or portion of 6"15 10 20 California Sampler Ring Sampler Continuous Sampling Grab Sample Portion not recovered Split-Spoon Sampler (SPT) Cement grout surface seal Bentonite seal Filter pack with blank casing section Screened casing or Hydrotip with filter pack End cap ATD At time of drilling Static water level (date) (1)Percentage by dry weight (2)Combined USCS symbols used for fines between 5% and 12% (3)(SPT) Standard Penetration Test (ASTM D-1586) (4)In General Accordance with Standard Practice for Description and Identification of Soils (ASTM D-2488) Groundwater depth i n c o r p o r a t e d e a r t h s c i e n c e s a s s o c i a t e d EXPLORATION LOG KEY FIGURE: A1Blocks\ dwg \ log_key 2022.dwg LAYOUT: Layout 5 - 2022 Logdraft 0 2.5 5 7.5 10 12.5 15 17.5 1 2 3 4 5 Sod/Topsoil - 3 inches Fill Upper 8 inches: Moist, brown to dark brown, silty, fine to medium SAND, some gravel; scattered organics (rootlets) (SM). Vashon Ice Contact Lower 10 inches: Moist, gray with orange oxidation staining, fine SAND, some silt (SP-SM). Very moist, brown to grayish brown, fine to medium SAND, some silt, some gravel; less silt with depth (SP-SM). Advance Outwash (Lacustrine) Wet, tan transitioning to gray, silty, fine to medium SAND, trace to some gravel; faintly bedded with silty, fine sand (SM). Very moist, brown with orange oxidation staining, silty, fine to medium SAND, some gravel, transitioning to gray, fine sandy, SILT, trace gravel; some medium sand present at tip of sample (SM). Pre-Fraser Non-Glacial Very moist to wet, gray, fine to medium SAND, trace to some gravel; massive (SP). 11 8 14 12 13 15 27 27 21 17 27 50/5" 31 50/4" 22 28 48 50/5" 50/4" Associated Earth Sciences, Inc. Exploration Boring EB-1 Hazen High School Modernization 1 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):25.8 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»468 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):7.5,14 Groundwater Depth Post Drilling (ft) (Date): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription Water LevelBlows/6"Blows/Foot 10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 1 of 2 20 22.5 25 27.5 30 32.5 35 37.5 6 7 Wet, gray, fine to medium SAND, trace to some gravel; occasional layer (up to 0.5 inches thick) of medium to coarse sand (SP). Wet, gray, fine to coarse SAND, trace to some gravel; occasional interbed (up to 0.25 inches thick) of silty, fine sand; occasional red sand grains (SP/SP-SM). Driller notes refusal due to hard drilling. Groundwater encountered at 7.5 feet and 14 feet ATD. 50/6" 37 50/4" 50/6" 50/4" Associated Earth Sciences, Inc. Exploration Boring EB-1 Hazen High School Modernization 2 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):25.8 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»468 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):7.5,14 Groundwater Depth Post Drilling (ft) (Date): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription Water LevelBlows/6"Blows/Foot 10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 2 of 2 0 2.5 5 7.5 10 12.5 15 17.5 1 2 3 4 5 Sod/Topsoil - 3 inches Fill Moist, dark brown with brown, silty, fine to medium SAND, some gravel; abundant organics (fine organics/rootlets/bark) (SM). Moist, tan to brown with orange mottling from oxidation staining, very silty, fine SAND; occasional gravel; rare organics (rootlets); disturbed texture (SM). Upper 9 inches: As above. Vashon Advance (Lacustrine) Lower 9 inches: Very moist, brown, fine SAND, trace silt (SP). Wet, brown, fine SAND, trace silt; occasional lamination of gray silt (SP). Slightly moist, tan, SILT, some fine sand; silt becomes gray and blue gray at tip of sampler (ML). Driller notes refusal due to hard drilling. Groundwater encountered at 10 feet ATD. 10 9 4 4 7 9 8 11 12 21 34 50/5" 27 33 50/5" 13 16 23 50/5" 50/5" Associated Earth Sciences, Inc. Exploration Boring EB-2 Hazen High School Modernization 1 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):16.4 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»468 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):10 Groundwater Depth Post Drilling (ft) (Date): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription Water LevelBlows/6"Blows/Foot 10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 1 of 1 0 2.5 5 7.5 10 12.5 15 17.5 1 2 3 4 5 Asphalt - 3 inches Fill Moist, brown to dark brown, silty, fine to medium SAND, trace to some gravel; abundant organics (fine black organics/rootlets) (SM). Vashon Ice Contact Moist, gray, fine SAND, trace silt; faint interbeds of silty, fine sand; faint petroleum odor (SP). Upper 12 inches: Very moist becoming wet, gray transitioning to tan, fine SAND (SP). Lower 6 inches: Wet, gray, fine to coarse SAND, some gravel, trace silt (SP). Wet, tan and light brown, fine to medium SAND, some silt, some gravel; broken gravel in spoon; blow count may be overstated (SP-SM). Vashon Advance Outwash (Lacustrine) Wet, brown heavily oxidized to orange, fine SAND, some silt; massive (SP- SM). 5 4 6 8 9 9 10 13 20 33 50/5" 18 50/6" 10 18 33 50/5" 50/6" Associated Earth Sciences, Inc. Exploration Boring EB-3 Hazen High School Modernization 1 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):25.4 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»466 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):8.5 Groundwater Depth Post Drilling (ft) (Date): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription Water LevelBlows/6"Blows/Foot 10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 1 of 2 20 22.5 25 27.5 30 32.5 35 37.5 6 7 Wet, tan to light brown with occasional orange oxidation staining, fine SAND, some silt; faintly bedded (SP-SM). Pre-Fraser Non-Glacial Moist to very moist, gray, silty, fine to coarse SAND; some gravel material coarsening with depth and becoming less moist; occasional organics; faint stratifications (SM). Driller notes refusal due to hard drilling. Groundwater encountered at 8.5 feet ATD. 18 34 47 50/5" 81 50/5" Associated Earth Sciences, Inc. Exploration Boring EB-3 Hazen High School Modernization 2 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):25.4 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»466 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):8.5 Groundwater Depth Post Drilling (ft) (Date): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription Water LevelBlows/6"Blows/Foot 10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 2 of 2 0 2.5 5 7.5 10 12.5 15 17.5 1 2 3 4 Bark/Mulch - 6 inches Fill Upper 6 inches: Moist, dark brown, silty, fine to medium SAND, some gravel; abundant organics (SM). Lower 12 inches: Moist, tan with orange oxidation staining, silty, fine SAND, some gravel; rare organics (bark) (SM). Vashon Ice Contact Moist, brown to gray with irregular orange mottling, silty to very silty, fine SAND (SM). Moist, gray with some orange oxidation staining, SILT, some fine sand, rare gravel; occasional interbed (up to 1/3-inches) of fine sand (ML). Vashon Lodgement Till Moist, brown, silty, fine SAND, some gravel; broken gravel in spoon; blow count may be overstated (SM). Driller notes refusal due to hard drilling. No groundwater encountered. 3 4 6 3 4 7 16 30 50/6" 50/6" 10 11 50/6" 50/6" Associated Earth Sciences, Inc. Exploration Boring EB-4 Hazen High School Modernization 1 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):11 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»468 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):Not encountered Groundwater Depth Post Drilling (ft) (Date): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription Water LevelBlows/6"Blows/Foot 10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 1 of 1 0 2.5 5 7.5 10 12.5 15 17.5 1 2 3 4 Bark/Mulch - 6 inches Fill Upper 6 inches: Moist, dark brown, silty, fine to medium SAND, some gravel; abundant organics (rootlets/fine organics) (SM). Lower 12 inches: Moist, tan to gray with large amounts of sub-horizontal orange oxidation staining, silty, fine SAND; rare gravel (SM). Vashon Ice Contact Very moist, tan to gray with minor orange oxidation staining, fine sandy, SILT; occasional interbeds of silty, fine sand (ML). Moist, brown, silty, fine to medium SAND, some gravel; unsorted; large lenses of gray, silty, fine sand at center of sample (SM). Vashon Lodgement Till Moist, brown, silty, fine SAND, some gravel; broken gravel in spoon; blow count may be overstated (SM). Driller notes refusal due to hard drilling. No groundwater encountered. 6 5 8 3 3 5 14 21 33 39 50/4" 13 8 54 50/4" Associated Earth Sciences, Inc. Exploration Boring EB-5 Hazen High School Modernization 1 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):10.8 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»468 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):Not encountered.Groundwater Depth Post Drilling (ft) (Date): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription Water LevelBlows/6"Blows/Foot 10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 1 of 1 0 2.5 5 7.5 10 12.5 15 17.5 1 2 3 4 5 6 Bark/Mulch - 4 inches Fill Moist, brown, silty, fine to medium SAND, some gravel; scattered organics (roots/rootlets) (SM). Moist to slightly moist, brown with gray inclusions, silty, fine SAND, some gravel; occasional lenses of gray, sandy, silt; broken gravel in spoon (SM). Pre-Fraser Fine Grained Slightly moist, brownish gray with some gray, very silty, fine SAND ranging to sandy, SILT; occasional interbed of gray silt (SM/ML). Slightly moist, grayish brown transitioning to gray with depth, SILT, some fine sand, some gravel (ML). Slightly moist, gray, SILT, some fine sand, trace gravel (ML). Slightly moist, gray to bluish gray, silty to very silty, fine SAND, trace to some gravel; unsorted (SM). Driller notes refusal due to hard drilling. No groundwater encountered. 14 19 25 20 30 45 26 27 33 32 37 45 50/6" 44 75 60 82 50/6" Associated Earth Sciences, Inc. Exploration Boring EB-6 Hazen High School Modernization 1 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):14.5 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»472 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):Not encountered Groundwater Depth Post Drilling (ft) (Date): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription Water LevelBlows/6"Blows/Foot 10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 1 of 1 APPENDIX B Historical Exploration Logs (AESI 2009, 2021, 2022) Asphalt - 2 inches Fill Upper 3 inches: Moist, grayish dark brown, silty, fine SAND, trace medium to coarse sand; faint organic odor (SM). Lower 15 inches: Moist, grayish brown, silty, fine SAND to fine sandy, SILT, trace gravel; massive (SM-ML). Vashon Recessional Outwash Moist, grayish brown, silty, fine SAND, trace gravel; unsorted (SM). S-1 S-2 15 10 10 11 18 21 Bottom of exploration boring at 3.5 feet No groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~466 5 10 EB-1 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number 20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet 1 of 1 NAVD 88 WellAESIBOR 20210251E002.GPJ March 21, 20222020 3939 Asphalt - 2 inches Fill Moist, dark brown, silty, fine SAND, some gravel; organics observed; faint organic odor (SM). Moist, brownish gray, silty, fine SAND, some gravel; some organics; faint organic odor; gravel in tip; poor recovery (SM). S-1 S-2 8 5 5 6 11 14 Bottom of exploration boring at 3 feet No groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~466 5 10 EB-2 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number 20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet 1 of 1 NAVD 88 WellAESIBOR 20210251E002.GPJ March 21, 20221010 2525 Asphalt - 1.75 inches Fill Moist, dark brown to grayish brown, fine SAND, some silt to silty, trace gravel; occasional organics; unsorted (SP-SM). Moist, dark brown, silty, fine SAND, trace medium sand; poor recovery (wood stuck in tip) (SM). S-1 S-2 7 5 5 6 9 10 Bottom of exploration boring at 3 feet No groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~465 5 10 EB-3 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number 20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet 1 of 1 NAVD 88 WellAESIBOR 20210251E002.GPJ March 21, 20221010 1919 Asphalt - 1.5 inches Fill Moist, dark brown to brownish gray, silty, fine SAND, some gravel; unsorted; occasional organics; faint organic odor; unsorted (SM). As above. Moist to wet, light gray, fine SAND, some silt; massive (SP-SM). S-1 S-2 S-3 6 4 5 5 8 8 9 13 17 Bottom of exploration boring at 5 feet Groundwater encountered at 3 feet. Ground Surface Elevation (ft) Grab SampleSymbol 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~465 5 10 EB-4 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number 20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet 1 of 1 NAVD 88 WellAESIBOR 20210251E002.GPJ March 21, 202299 1616 3030 Asphalt - 1.75 inches Gravel Base Course - 1 inch Vashon Recessional Outwash Moist, reddish brown, fine SAND, some silt, trace gravel; massive (SP-SM). As above. S-1 S-2 14 13 14 12 16 22 Bottom of exploration boring at 3 feet No groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~465 5 10 EB-5 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number 20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet 1 of 1 NAVD 88 WellAESIBOR 20210251E002.GPJ March 21, 20222727 3838 Asphalt - 3 inches (2 lifts) Fill Upper 6 inches: Moist, dark brown, silty, fine SAND, some gravel; unsorted (SM). Vashon Recessional Outwash Lower 12 inches: Moist, reddish brown, fine SAND,some silt, trace gravel; massive (SP-SM). As above. S-1 S-2 7 13 12 11 12 19 Bottom of exploration boring at 3 feet No groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~466 5 10 EB-6 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number 20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet 1 of 1 NAVD 88 WellAESIBOR 20210251E002.GPJ March 21, 20222525 3131 Asphalt - 2 inches Gravel Base Course - 3 inches Fill Moist, brownish gray to dark brown, silty, fine SAND, some gravel; unsorted; organics observed; layer (~3 inches thick) of coarse gravel; faint organic odor (SM) As above. S-1 S-2 5 2 5 3 11 16 Bottom of exploration boring at 3 feet No groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~466 5 10 EB-7 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number 20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet 1 of 1 NAVD 88 WellAESIBOR 20210251E002.GPJ March 21, 202277 2727 Asphalt - 1 inch Fill Moist, brownish gray, silty, fine SAND, some gravel; unsorted (SM). As above; contains organics. S-1 S-2 14 10 10 10 14 14 Bottom of exploration boring at 3 feet No groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~466 5 10 EB-8 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number 20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet 1 of 1 NAVD 88 WellAESIBOR 20210251E002.GPJ March 21, 20222020 2828 Asphalt - 3 inches (2 lifts) Gravel Base Course - 2 inches Fill Moist, dark brownto brownish gray, silty, fine SAND, some gravel; unsorted; faint organic odor (SM). Moist, dark brown to gray, silty, fine SAND, some gravel; unsorted; abundant organics; organic odor (SM). S-1 S-2 19 18 16 5 22 28 Bottom of exploration boring at 3 feet No groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~465 5 10 EB-9 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number 20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet 1 of 1 NAVD 88 WellAESIBOR 20210251E002.GPJ March 21, 20223434 5050 Asphalt - 3 inches (2 lifts) Fill Moist, dark brown to grayish brown, silty, fine SAND, to fine sandy, SILT, trace gravel; organics observed; organic odor (SM-ML). As above. S-1 S-2 6 6 5 7 13 19 Bottom of exploration boring at 3 feet No groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~464 5 10 EB-10 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number 20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet 1 of 1 NAVD 88 WellAESIBOR 20210251E002.GPJ March 21, 20221111 3232 Asphalt - 3 inches (2 lifts) Gravel Base Course - 3 inches Fill Moist, dark brown, silty, fine SAND, some gravel; abundant organics; organic odor; unsorted (SM). Moist, bluish gray, silty, fine SAND; massive (SM). S-1 S-2 13 5 4 8 14 12 Bottom of exploration boring at 3 feet No groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~466 5 10 EB-11 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number 20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet 1 of 1 NAVD 88 WellAESIBOR 20210251E002.GPJ March 21, 202299 2626 Topsoil - 6 inches Fill Cuttings are brown GRAVEL. Very gravelly drilling 0 to 4 feet. Moist, brown, silty, fine SAND; trace gravel; blowcount likely overstated due to oversized gravel; not representative (SM). Upper 6 inches: As above. Vashon Recessional Outwash Lower 12 inches: Moist, brown with occasional planes of oxidation, fine SAND, some silt, trace gravel; bedded with occasional thin interbeds of silty, fine SAND ranging to fine sandy, SILT (SP-SM). Becomes very moist to wet. Layer (.25 inches thick) of dark gray sand at tip. Pre-Olympia Glacial Till Moist, dark gray, very silty, fine SAND, some gravel; unsorted (SM) Drilling slows. Moist with wet coating from above water, brown with oxidation, silty, fine SAND, some gravel; unsorted (SM). S-1 S-2 S-3 S-4 S-5 17 18 10 7 8 13 8 12 12 12 16 17 27 31 30 Bottom of exploration boring at 21.5 feet Groundwater encountered 8 to 12 feet. Ground Surface Elevation (ft) Grab SampleSymbol 6 40 Datum Hammer Weight/Drop Sampler Type (ST): ~460 5 10 15 20 EB-1 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS JG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number 20210397E001 10/20/21,10/20/21 Logged by: Shelby Tube Sample 140# / 30 Geologic Drill Partners / Mini-Bobcat Exploration Boring Water Level at time of drilling (ATD) Hazen HS Pool Modernization M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet 1 of 1 NAVD 88 WellAESIBOR 20210397E001.GPJ November 5, 20212828 2121 2424 3333 61 APPENDIX C Shear Wave Velocity Results (WGS 2020) WASHINGTON 2019–2021 SCHOOL SEISMIC SAFETY PROJECT SITE CLASS ASSESSMENT See Washington Geological Survey Open File Report 2019-01 for more information. HAzEN HIGH SCHOOL Location of seismic array at the school campus. Liquefaction Very low RENTON SCHOOL DISTRICT, KING COUNTY, WA WHAT IS SITE CLASS? Site class estimates how local soils amplify earthquake- induced ground shaking, and is based on how fast seismic (shear) waves travel through the upper 30 m (100 ft) of the soil (Vs30). Site class has been approximated for the entire State of Washington, but these predictions aren’t always accurate where geology is complex. The site class measured for this project accounts for geologic complexity and is therefore more accurate. HOW DID WE MEASURE SITE CLASS? On October 22, 2020, a team from the Washington Geological Survey conducted a seismic survey at Hazen High School. We measured Vs30 by laying out 48 geophones (ground motion sensors) in a 94 m (308 ft) array. Then we conducted (1) an active survey in which a sledgehammer was struck against the ground to generate seismic waves; and (2) a passive survey where we measured ambient seismic noise. These surveys let us calculate Vs30 at the center of the array, which is then correlated to site class using the table below. It is generally accurate to assume the site class is the same under the array and the school. WHAT DID WE LEARN? □The school is built on soft rock or very dense soil, which would amplify ground shaking relative to rock. □Site class is within the predicted site class of C–D.WHAT SOILS ARE UNDER THE SCHOOL? The school is sitting on Pleistocene continental glacial drift consisting of well-sorted and fine-grained sandy units with interlayered coarser sand, gravel, and cobbles. GEOLOGIC HAzARDS AT THE SCHOOL Ground Shaking Violent MEASURED SITE CLASS Active Fault Proximity Within 5 miles of an active mapped fault Site class Description Vs30 (m/sec) Ground shaking amplification A Hard rock >1,500 Low B Rock 760–1,500 C Soft rock or very dense soil 360–760 D Stiff soil 180–360 E Soft soil <180 High C TECHNICAL OVERVIEW OF RESULTS QUESTIONS?Washington Department of Natural Resources—WA Geological Survey geology@dnr.wa.gov • 360.902.1450 • https://www.dnr.wa.gov/geology HAzEN HIGH SCHOOL—ICOS# 21350 This section provides a technical overview of the geophysical methods and results of the seismic site characterization. DISPERSION CURVE The term dispersion image refers to the image of phase velocity versus frequency of a record. Dispersion curve refers to the manually picked fundamental mode in a dispersion image. The multi-channel analysis of surface wave (MASW) dispersion images from the forward and reverse directions are poor quality so that the fundamental mode can be picked with some confidence. However, the MASW dispersion curves do not sample down to 30 m (100 ft), and there is noticeable interference from higher modes. The microtremor analysis method (MAM) dispersion image is decent quality, but does not sample the shallow layers. MAM and the forward and reverse MASW dispersion curves depict similar trends, therefore the three dispersion curves are combined into a single model. VELOCITY MODEL An initial model was generated using the 1/3 wavelength approximation and the combined dispersion curves. The initial model had an RMSE of 11.1 percent. The inversion was carried out for seven iterations and resulted in a final model with an RMSE of 4.5 percent. The final model is unconstrained in the top 1 m (3 ft), and below this shows rapidly increasing velocity to 10 m (33 ft), then a slight velocity reversal down to 17 m (56 ft), and then generally increasing velocity down to 30 m (100 ft). Our best Vs30 measurement is 376 m/sec, which places the site in the C site class near the C/D border. This is within the predicted site class of C-D. Final inverted velocity model with measured dispersion curve and modeled dispersion curve. The equation used to calculate the average shear wave velocity (Vs) for the upper 30 m is shown in the middle left of the figure. di = thickness of any layer between 0 and 30 m. Vsi = shear wave velocity in m/sec of the layer. WASHINGTON 2019–2021 SCHOOL SEISMIC SAFETY PROJECT SITE CLASS ASSESSMENT See Washington Geological Survey Open File Report 2019-01 for more information. LINdbERGH SENIOR HIGH SCHOOL Location of seismic array at the school campus. Liquefaction Very low RENTON SCHOOL dISTRICT, KING COUNTY, WA WHAT IS SITE CLASS? Site class estimates how local soils amplify earthquake- induced ground shaking, and is based on how fast seismic (shear) waves travel through the upper 30 m (100 ft) of the soil (Vs30). Site class has been approximated for the entire State of Washington, but these predictions aren’t always accurate where geology is complex. The site class measured for this project accounts for geologic complexity and is therefore more accurate. HOW dId WE MEASURE SITE CLASS? On October 22, 2020, a team from the Washington Geological Survey conducted a seismic survey at Lindbergh Senior High School. We measured Vs30 by laying out 48 geophones (ground motion sensors) in a 94 m (308 ft) array. Then we conducted (1) an active survey in which a sledgehammer was struck against the ground to generate seismic waves; and (2) a passive survey where we measured ambient seismic noise. These surveys let us calculate Vs30 at the center of the array, which is then correlated to site class using the table below. It is generally accurate to assume the site class is the same under the array and the school. WHAT dId WE LEARN? □The school is built on soft rock or very dense soil, which would amplify ground shaking relative to rock. □Site class is the same as the predicted site class of C.WHAT SOILS ARE UNdER THE SCHOOL? The school is sitting on Pleistocene continental glacial till, comprising a compact and unsorted mixture of sand, silt, clay, and gravel. GEOLOGIC HAZARdS AT THE SCHOOL Ground Shaking Violent MEASURED SITE CLASS Site class Description Vs30 (m/sec) Ground shaking amplification A Hard rock >1,500 Low B Rock 760–1,500 C Soft rock or very dense soil 360–760 D Stiff soil 180–360 E Soft soil <180 High C TECHNICAL OVERVIEW OF RESULTS QUESTIONS?Washington Department of Natural Resources—WA Geological Survey geology@dnr.wa.gov • 360.902.1450 • https://www.dnr.wa.gov/geology LINdbERGH SENIOR HIGH SCHOOL—ICOS# 21365 This section provides a technical overview of the geophysical methods and results of the seismic site characterization. dISPERSION CURVE The term dispersion image refers to the image of phase velocity versus frequency of a record. Dispersion curve refers to the manually picked fundamental mode in a dispersion image. The multi-channel analysis of surface wave (MASW) dispersion images from the forward and reverse directions are decent quality so that the fundamental mode can be picked with confidence. However, the MASW dispersion curves do not adequately sample down to 30 m (100 ft). The microtremor analysis method (MAM) dispersion image is also decent quality but does not sample the shallow layers. Overall, the MASW and MAM dispersion curves correlate well, so the MASW (forward and reverse direction) and MAM dispersion curves are combined into a single model. VELOCITY MOdEL An initial model was generated using the 1/3 wavelength approximation and the combined dispersion curves. The initial model had an RMSE of 10.4 percent. The inversion was carried out for five iterations and resulted in a final model with an RMSE of 5.6 percent. The final model is unconstrained in the top 2 m (6 ft), and below this shows rapidly increasing velocity to 10 m (30 ft), then generally increasing velocity down to 30 m (100 ft). Our best Vs30 measurement is 397 m/sec, which places the site in the C site class. Although the upper 2 m are unconstrained, adjusting them does not change the site class. All initial and final models are in the C class, so the site can be confidently classified. This is the same as the predicted site class of C. Final inverted velocity model with measured dispersion curve and modeled dispersion curve. The equation used to calculate the average shear wave velocity (Vs) for the upper 30 m is shown in the upper right corner. di = thickness of any layer between 0 and 30 m. Vsi = shear wave velocity in m/sec of the layer. WASHINGTON 2019–2021 SCHOOL SEISMIC SAFETY PROJECT SITE CLASS ASSESSMENT See Washington Geological Survey Open File Report 2019-01 for more information. RENTON HIGH SCHOOL Location of seismic array at the school campus. Liquefaction Moderate to high RENTON SCHOOL DISTRICT, KING COUNTY, WA WHAT IS SITE CLASS? Site class estimates how local soils amplify earthquake- induced ground shaking, and is based on how fast seismic (shear) waves travel through the upper 30 m (100 ft) of the soil (Vs30). Site class has been approximated for the entire State of Washington, but these predictions aren’t always accurate where geology is complex. The site class measured for this project accounts for geologic complexity and is therefore more accurate. HOW DID WE MEASURE SITE CLASS? On October 15, 2020, a team from the Washington Geological Survey conducted a seismic survey at Renton High School. We measured Vs30 by laying out 48 geophones (ground motion sensors) in a 94 m (308 ft) array. Then we conducted (1) an active survey in which a sledgehammer was struck against the ground to generate seismic waves; and (2) a passive survey where we measured ambient seismic noise. These surveys let us calculate Vs30 at the center of the array, which is then correlated to site class using the table below. It is generally accurate to assume the site class is the same under the array and the school. WHAT DID WE LEARN? □The school is built on stiff soil, which would amplify ground shaking relative to rock. □Site class is within the predicted site class of D–E.WHAT SOILS ARE UNDER THE SCHOOL? The school is sitting on urban or industrial land modified by widespread or discontinuous artificial fill. GEOLOGIC HAZARDS AT THE SCHOOL Ground Shaking Violent MEASURED SITE CLASS D Site class Description Vs30 (m/sec) Ground shaking amplification A Hard rock >1,500 Low B Rock 760–1,500 C Soft rock or very dense soil 360–760 D Stiff soil 180–360 E Soft soil <180 High TECHNICAL OVERVIEW OF RESULTS QUESTIONS?Washington Department of Natural Resources—WA Geological Survey geology@dnr.wa.gov • 360.902.1450 • https://www.dnr.wa.gov/geology RENTON HIGH SCHOOL—ICOS# 21354 This section provides a technical overview of the geophysical methods and results of the seismic site characterization. DISPERSION CURVE The term dispersion image refers to the image of phase velocity versus frequency of a record. Dispersion curve refers to the manually picked fundamental mode in a dispersion image. The multi-channel analysis of surface wave (MASW) dispersion images from the forward and reverse directions are poor quality, but the fundamental mode can be picked with some confidence. However, the microtremor analysis method (MAM) dispersion image is excellent quality, so that the fundamental mode can be picked with high confidence. MAM and the forward and reverse MASW dispersion curves correlate well, depicting similar trends. Therefore the three dispersion curves are combined into a single model. VELOCITY MODEL An initial model was generated using the 1/3 wavelength approximation and the combined dispersion curves. The initial model had an RMSE of 12.9 percent. The inversion was carried out for ten iterations and resulted in a final model with an RMSE of 4.7 percent. The final model is unconstrained in the top 1 m (3 ft), and below this shows rapidly increasing velocity to 6 m (20 ft), then generally increasing velocity down to 30 m (100 ft). Our best Vs30 measurement is 272 m/sec, which places the site solidly in the D site class. This is within the predicted site class of D–E. Final inverted velocity model with measured dispersion curve and modeled dispersion curve. The equation used to calculate the average shear wave velocity (Vs) for the upper 30 m is shown in the upper right corner. di = thickness of any layer between 0 and 30 m. Vsi = shear wave velocity in m/sec of the layer.