Loading...
24-100477-5 - Pacific Hwy Non-Motorized Corridor, Final Geotech Report-02-01-24 GEOTECHNICAL REPORT Pacific Highway Non-Motorized Corridor 16th Avenue S (S308th St to S288th St) Federal Way, Washington HWA Project No. 2019-151-21 Prepared for KPFF, Inc. January 12, 2021 Geotechnical Engineering Pavement Engineering Geoenvironmental Hydrogeology Inspection & Testing 21312 30th Dr. SE, STE. 110, Bothell, WA 98021 | 425.774.0106 | hwageo.com January 12, 2021 HWA Project No. 2019-151-21 KPFF, Inc. 1601 Fifth Avenue, Suite 1600 Seattle, Washington 98101 Attention: Steve Battle, P.E. Subject: Geotechnical Report Pacific Highway Non-Motorized Corridor 16th Avenue S (S 308th St to S 288th St) Federal Way, Washington Dear Steve; As requested, HWA GeoSciences Inc. (HWA) has performed geotechnical engineering evaluations for the proposed improvements along the Pacific Highway Non-Motorized Corridor along the 16th Avenue S alignment between S 308th Street and S 288th Street in Federal Way, Washington. This report includes the results of our field explorations, laboratory testing, and our geotechnical engineering analysis and recommendations completed to date. This report will be finalized upon receipt of your review comments. We appreciate the opportunity to provide geotechnical engineering services for this project. If you have any questions regarding this report or require additional information or services, please contact the undersigned at your convenience. Sincerely, HWA GeoSciences Inc. Michael S. Place, P.E. Senior Geotechnical Engineer Enclosure: Geotechnical Report January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report ii HWA GEOSCIENCES INC. TABLE OF CONTENTS 1. INTRODUCTION..............................................................................................................1 1.1 GENERAL .......................................................................................................1 1.2 PROJECT UNDERSTANDING ............................................................................1 1.3 SURFACE CONDITIONS ...................................................................................1 2. FIELD INVESTIGATION AND LABORATORY TESTING ......................................................2 2.1 GEOTECHNICAL SUBSURFACE EXPLORATIONS ..............................................2 2.2 LABORATORY TESTING .................................................................................2 3. SITE CONDITIONS ..........................................................................................................3 3.1 GENERAL GEOLOGIC CONDITIONS ................................................................3 3.2 SUBSURFACE SOIL CONDITIONS ....................................................................3 3.3 GROUND WATER CONDITIONS ......................................................................4 4. CONCLUSIONS AND RECOMMENDATIONS ......................................................................4 4.1 GENERAL .......................................................................................................4 4.2 SEISMIC CONSIDERATIONS ............................................................................5 4.2.1 Seismic Design Parameters ...........................................................5 4.2.2 Soil Liquefaction ...........................................................................6 4.3 LUMINAIRE FOUNDATIONS ............................................................................6 4.4 PILE FOUNDATIONS .......................................................................................6 4.4.1 Pin Piles .........................................................................................6 4.4.2 Drilled Piles ...................................................................................7 4.4.3 Pile Construction Monitoring ........................................................9 4.5 RETAINING WALL STRUCTURES ....................................................................9 4.5.1 Wall Design Recommendations ....................................................9 4.5.2 Wall Subgrade Preparation ............................................................10 4.5.3 Cantilevered Soldier Pile Walls ....................................................11 4.6 STORMWATER MANAGEMENT .......................................................................13 4.7 PAVEMENT DESIGN .......................................................................................14 4.8 GENERAL EARTHWORK .................................................................................14 4.8.1 Dewatering ....................................................................................14 4.8.2 Structural Fill .................................................................................14 4.8.3 Compaction ...................................................................................14 4.8.4 Wet Weather Earthwork ................................................................15 4.8.5 Temporary Excavations .................................................................15 5. CONDITIONS AND LIMITATIONS .....................................................................................16 6. REFERENCES .................................................................................................................18 January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report iii HWA GEOSCIENCES INC. FIGURES (Following Text) Figure 1 Site Vicinity Map Figures 2A-2D Site and Exploration Plans Figure 3 Surcharge Loading Appendix A: Logs of HWA Explorations Figure A-1 Legend of Terms and Symbols Used on Exploration Logs Figure A-2 to A-7 Logs of Hand Holes HAB-1 through HAB-6 Figure A-8 to A-12 Logs of Borings BH-1 through BH-5 Appendix B: Laboratory Test Results Figure B-1 Summary of Material Properties From Hand Auger Borings Figure B-2 Grain Size Distributions From Hand Auger Borings Figure B-3 Summary of Material Properties From Machine Borings Figures B-4 to B-5 Grain Size Distributions From Machine Borings Figure B-6 Atterberg Limits From Machine Borings GEOTECHNICAL REPORT PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTON 1. INTRODUCTION 1.1 GENERAL This report summarizes the results of the geotechnical engineering study performed by HWA GeoSciences Inc. (HWA) for the proposed improvements along the Pacific Highway Non- Motorized Corridor along the 16th Avenue S alignment between S 308th Street and S 288th Street in Federal Way, Washington. Figure 1, Site Vicinity Map, and Figure 2, Site and Exploration Plan, show the approximate location of the project alignment along the non-motorized corridor. Our field work included drilling five (5) machine-drilled borings and advancing six (6) hand augers along the corridor. Appropriate laboratory tests were conducted on selected soil samples to determine relevant engineering properties of the subsurface soils. Engineering analyses were conducted to develop recommendations for signal pole foundations, luminaire foundations, boardwalk foundations and asphalt concrete surfacing for the trail. 1.2 PROJECT UNDERSTANDING It is our understanding that the City of Federal Way plans to make improvements to a non- motorized shared-use path along the Pacific Highway South Corridor from S 308th Street to S 288th Street. The project encompasses design for a path/trail that for portions of the alignment will follow parallel to Pacific Highway S and for portions of the alignment will be located within the partially unopened right-of-way for 16th Avenue S. The segments of trail located off roadway will include pedestrian-scale illumination for safety. 1.3 SURFACE CONDITIONS The project alignment slopes gently downward from S 288th Street for a distance of about 2,000 feet before rising gently over a distance of about 500 feet to the intersection of S Dash Point Road and 16th Avenue S. The remainder of the project alignment is relatively flat. The 2,500-foot segment goes through an undeveloped area with trees and shrubs on both sides and residential and business developments beyond the trees and shrubs. The remainder of the project alignment south of the intersection of S Dash Point Road and 16th Avenue S is developed with either concrete or hot-mix asphalt sidewalk. Development along this portion of the project alignment consists of roadway, commercial properties, single-family residential properties, and schools. January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 2 HWA GEOSCIENCES INC. 2. FIELD INVESTIGATION AND LABORATORY TESTING 2.1 GEOTECHNICAL SUBSURFACE EXPLORATIONS Our geotechnical exploration program included surface reconnaissance of the alignment and drilling five (5) machine-drilled borings, designated BH-1 through BH-5, along the portion of the project alignment between S 288th Street and the intersection of S Dash Point Road and 16th Avenue S. Six (6) hand auger borings, designated HAB-1 through HAB-6, were advanced along the portion of the project alignment between the intersection of S Dash Point Road and 16th Avenue S and S 308th Street. Boring locations were determined based on the extent of the project alignment and are indicated on the Site and Exploration Plan, Figure 2. Borings BH-1 through BH-5 were drilled by Geologic Drill Partners, Inc. of Bellevue, Washington, under subcontract to HWA. Hand auger borings HAB-1 through HAB-6 were advanced using a hand auger by two (2) HWA geotechnical engineers, who also performed the DCP tests. Logs for the borings are presented in Appendix A of this report. In borings BH-1 through BH-5, Standard Penetration Test (SPT) sampling was performed at selected intervals and the SPT resistance (“N-value”) of the soil was logged. This resistance, or N-value, provides an indication of relative density of granular soils and the relative consistency of cohesive soils. In hand auger borings HAB-1 through HAB-6, a Dynamic Cone Penetrometer (DCP) test was performed in each boring. The DCP test data collected was used to develop a correlation with the N-value of the soil at each boring location. A geotechnical engineer from HWA logged the explorations and recorded pertinent information, including sample depths, stratigraphy, soil engineering characteristics, and ground water occurrence. Soil samples obtained from the explorations were classified in the field and representative portions were placed in plastic bags. These soil samples were then taken to our Bothell, Washington, laboratory for further examination and testing. The stratigraphic contacts shown on the exploration logs represent the approximate boundaries between soil types; actual transitions may be gradual or vary slightly in location. The soil and ground water conditions depicted are only for the specific date and location reported and, therefore, are not necessarily representative of other locations and times. 2.2 LABORATORY TESTING Laboratory tests were conducted at HWA’s Bothell, Washington laboratory, on selected samples retrieved from the borings to determine relevant index and engineering properties of the soils encountered at the site. The tests included visual classifications, natural moisture content, Atterberg Limits and grain size distribution. The tests were conducted in general accordance with appropriate American Society of Testing and Materials (ASTM) standards. The test results and a discussion of laboratory test methodology are presented in Appendix B, and/or displayed on the exploration logs in Appendix A, as appropriate. January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 3 HWA GEOSCIENCES INC. 3. SITE CONDITIONS 3.1 GENERAL GEOLOGIC CONDITIONS The project alignment is located within the Puget Lowland. The Puget Lowland has repeatedly been occupied by a portion of the continental glaciers that developed during the ice ages of the Quaternary period. During at least four periods, portions of the ice sheet advanced south from British Columbia into the lowlands of Western Washington. The southern extent of these glacial advances was near Olympia, Washington. Each major advance included numerous local advances and retreats, and each advance and retreat resulted in its own sequence of erosion and deposition of glacial lacustrine, outwash, till, and drift deposits. Between and following these glacial advances, sediments from the Olympic and Cascade Mountains accumulated in the Puget Lowland. According to the Geologic Map of King County, Washington (Booth et al, 2007), the project alignment is underlain by Pleistocene Vashon drift consisting of glacial till. Glacial till generally consists of a mixture of clay, silt, sand, and gravel deposited by an overriding glacier and as such is heavily over-consolidated. 3.2 SUBSURFACE SOIL CONDITIONS The soils encountered in our explorations consist of topsoil, fill material, native silts, glacial till, and advance outwash. Further descriptions of soils encountered in our explorations are presented below in order of deposition, beginning with the most recently deposited. The exploration logs in Appendix A provide more detail of subsurface conditions observed at specific locations and depths. • Topsoil: Topsoil was encountered in the explorations outside of paved areas. This material was dark brown and consisted of silty sand with abundant rootlets. When present, the topsoil was approximately 3 to 6 inches thick. • Fill: Fill was encountered in borings BH-1, and BH-3 through BH-5. This material was olive-gray and consisted predominantly of silty sand with gravel. The fill was approximately 9 feet thick in BH-1 and between 4 and 7 feet thick in BH-3 through BH-5. In BH-3 the fill was approximately 3 feet thick, while in BH-1, it was approximately 7 feet thick. The fill likely was placed during construction of the roadways sidewalks and utility lines. • Native Silts: Native silts were encountered in boring BH-4 and may be lacustrine, glaciolacustrine, or ice contact deposits. These soils were generally medium stiff in the upper section and become hard at depth. These types of soil often have sandy lenses of soil within them. Silts are generally poor conduits for water flow, however sandier lenses within them can be water bearing and allow for water migration. • Glacial Till: Glacial till was encountered in borings BH-1 through BH-3 below the fill soils. The glacial till soils consisted of very dense, rust-mottled olive-gray to olive- January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 4 HWA GEOSCIENCES INC. brown, silty sand with gravel and poorly graded sand with silt and gravel. Glacial till is material which was deposited below the base of the glacial ice sheet. It consists of an unsorted mixture of clay, silt, sand and gravel, which is very dense, having been consolidated by the weight of greater than 2,000 feet of ice. It is also known to contain scattered cobbles and boulders, known as glacial erratics. Till is relatively impermeable and generally not suitable for onsite infiltration. Generally, the till forms an impervious layer below which surface water cannot penetrate. Where sand overlies the till, water is often perched on top of the till. • Advance Outwash: Advance outwash was encountered in explorations BH-5 and HAB- 2 and is often found below glacial till soils. Advance outwash is material deposited by glacial meltwaters that are then overridden by advancing glaciers. They typically consist of silts, sands, and gravels with lower overall silt contents than glacial till soils. Advance outwash often allows for the movement of groundwater and can often facilitate infiltration if groundwater is not present. 3.3 GROUND WATER CONDITIONS Ground water seepage was observed in borings BH-2 through BH-5 and HAB-2. In borings BH-2 through BH-5, the seepage was observed at depths ranging from approximately 4 and 11 feet below ground surface (bgs). In HAB-2, the seepage was observed at a depth of approximately 2 feet bgs. No ground water seepage was observed in BH-1, HAB-1, and HAB-3 through HAB-6 at the time of our explorations; however, hand auger borings HAB-1 and HAB-3 through HAB-6 were terminated at depths of about 1½ to 4 feet due to refusal in coarse grained soils. Prospective contractors should be prepared to encounter and manage seasonally varying perched ground water on top of the very dense glacial till deposits. Increases in the volume of perched ground water should be expected wherever excavations bisect existing utility trenches. Existing utility trench backfill is expected to be significantly more permeable than the native glacial till deposits. Therefore, we expect that perched ground water will collect and flow along the alignment of existing utility trenches. 4. CONCLUSIONS AND RECOMMENDATIONS 4.1 GENERAL The subsurface soils encountered during our explorations generally consist of glacially consolidated soils overlain by fill. The glacial soils are generally sufficient to support the proposed improvements with implementation of some mitigation measures where loose fill and weathered soils are encountered. It is our understanding that some small retaining walls may be constructed where needed along portions of the project alignment. The subgrade soil conditions in the vicinity of these walls will January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 5 HWA GEOSCIENCES INC. provide adequate support for the walls with some over excavation and replacement of loose near- surface material. We understand that construction of boardwalks is being considered along two sections of the alignment, one over the ravine near Redondo Way S and another on the north end of the alignment near S 288th Street. Furthermore, we understand that pedestrian-scale luminaire structures are being considered throughout the proposed alignment. The subgrade soils along the alignment will provide adequate lateral bearing capacity to allow the use of WSDOT Standard Plans for the associated foundations at all proposed locations. 4.2 SEISMIC CONSIDERATIONS 4.2.1 Seismic Design Parameters Earthquake loading for the applicable proposed improvements was developed in accordance with Section 3.4 of the AASHTO Guide Specifications for LRFD Bridge Design, 2nd Edition, 2011 and the Washington State Department of Transportation (WSDOT) amendments to the AASHTO Guide Specifications provided in the Bridge Design Manual (LRFD) (WSDOT, 2019). For seismic analysis, the Site Class is required to be established and is determined based on the average soil properties in the upper 100 feet below the ground surface. Based on our explorations and understanding of site geology, it is our opinion that the proposed improvements are underlain by soils consistent with Site Class C. Therefore, Site Class C should be used with AASHTO seismic evaluations for this project. Table 1 presents recommended seismic coefficients for use with the General Procedure described in AASHTO (2011), which is based upon a design event with a 7 percent probability of exceedance in 75 years (equal to a return period of 1,033 years). The seismic design category for this project site is C. Table 1: Seismic Coefficients for Evaluation Using AASHTO Guide Specifications calculated by USGS Seismic Hazard Map (Site Class C) Period (sec) Mapped Spectral Response Acceleration (g) Site Coefficients Design Spectral Response Acceleration (g) 0.0 PGA 0.411 FPGA 1.200 As 0.493 0.2 Ss 0.935 Fa 1.200 SDS 1.122 1.0 S1 0.269 Fv 1.500 SD1 0.404 Notes: Parameters are for Latitude 47.336210° and Longitude -122.31229° PGA = Peak ground acceleration FPGA = PGA site coefficient AS = Design acceleration coefficient (peak ground acceleration adjusted for Site Class effects) Ss = Short period (0.2 second) Mapped Spectral Acceleration S1 = 1.0 second period Mapped Spectral Acceleration SDS = Spectral Response adjusted for site class effects for short period = Fa • Ss SD1 = Spectral Response adjusted for site class effects for 1-second period = Fv • S1 Fa = Short Period Site Coefficients Fv = Long Period Site Coefficients January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 6 HWA GEOSCIENCES INC. 4.2.2 Soil Liquefaction Liquefaction is a temporary loss of soil shear strength due to earthquake shaking. Loose, saturated cohesionless soils are susceptible to earthquake-induced liquefaction; however, recent experience and research has shown that certain silts and low-plasticity clays are also susceptible. Primary factors controlling the development of liquefaction include the intensity and duration of strong ground motions, the characteristics of subsurface soils, in-situ stress conditions and the depth to ground water. Based on our explorations, absence of ground water in soils that would otherwise be susceptible to seismic induced liquefaction soils and shallow glacially consolidated soils indicate that liquefaction is not a design consideration for the project alignment. 4.3 LUMINAIRE FOUNDATIONS Corridor improvements will include pedestrian-scale lighting along segments of trail off roadway for safety. We anticipate that the luminaire foundations will be designed in accordance with WSDOT Standard Plans. Based on the shallow soils encountered during our explorations, we expect that luminaire foundations can be designed for an allowable lateral bearing pressure of 1,000 pounds per square foot (psf) in areas north of S Dash Point Road, and 2,000 psf in areas south of S Dash Point Road. 4.4 PILE FOUNDATIONS To allow for construction of the trail construction some pile supported boardwalks may need to be considered. Near Redando Way S a steep slope ravine exists that is susceptible to scour and erosion. Additionally, the proposed portion of the pathway approaching S 288th Street construction of a pile supported boardwalk could be used in place of a large retaining wall structure. Using a retaining wall would place an increased load on the surface of the slope which could lead to slope instability. Conversely, piles would place the loads deeper into the soil and even offer lateral resistance to surficial movements of the soil slope. Piles may consist of either driven pin piles or drilled shaft foundations, however, pin pile foundations are generally more cost effective and will likely be easier to install in areas with more challenging access conditions. 4.4.1 Pin Piles Pin piles are small-diameter steel pipe piles driven by heavy pneumatic or hydraulic hammers. Typically, concrete caps or support beams are placed on top of the newly installed pin piles to support the structure. A structural engineer should design the pile foundation, grade beam and slab system. We recommend using 3-inch, 4-inch or 6-inch diameter galvanized steel piles that are driven to refusal to a depth of at least 10 feet below ground surface and be embedded a minimum of 5 feet into stiff/dense native soils using a heavy pneumatic or hydraulic hammer. Pin piles installed in accordance with our recommendations should provide adequate capacities to support the boardwalk and will reduce loads on the surface of the slope and add some lateral support to the January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 7 HWA GEOSCIENCES INC. site slopes. Small diameter pin piles are not typically considered to provide lateral capacity, but if lateral capacities are needed, they could be achieved driving battered piles. If 6-inch diameter pin piles are utilized, lateral capacities may be achievable and lateral capacities may be calculated using the L-Pile parameters listed in Section 4.4.2 of this report. Settlements on pin piles driven to refusal are generally less than one inch of total settlement during their lifespan. Pin piles should be driven to refusal based on criteria determined using a WEAP analysis. Refusal criteria is depended on the size of the pile being installed and the type of hammer being used and is typically given in seconds per inch of movement. We anticipate that the piling contractor that is selected for this project will utilize a hydraulic hammer to drive the pin piles proposed for the foundation system for the subject structure. The acceptance criteria for the piles should be determined once the pile diameter and the hammer size is determined. Typically 3-inch, 4-inch and 6-inch pin piles driven to refusal, as described above, can provide ultimate capacities of 10 kips, 16 kips and 28 kips respectively. A factor of safety of at least 2 should be used in the design of the pin piles. A pile load test should be conducted on a sacrificial pile to determine actual capacity. however, the pile load test can be omitted provided a factor of safety of 3 is used in the design of the pin piles. If pin pile load tests are conducted at least on pin pile load test per area where pin piles are to be installed (i.e. one within the section near S 288th Street and one by the ravine near Redando Way S). Piles installed in accordance with the specified refusal criteria should provide an ultimate uplift capacity of 0.4 kips, 0.6 kips, and 1 kip for 3-inch, 4-inch and 6-inch pin piles respectively, provided only one pile section is installed or the sections are welded together if more than one section is needed (note typical pin-pile sections come in lengths of about 21 feet). We estimate that the specified refusal criteria will be reached at a depth of approximately 15 to 25 feet below base of the existing ground surface based on conditions observed during our field investigation. Actual pile depths may vary depending upon subsurface topography and the consistency of the dense native soils. 4.4.2 Drilled Piles If drilled piles are to be utilized, they should consist of an augured shaft having typical diameters of approximately 12 to 36 inches. They are drilled to a design depth and filled with reinforced concrete. Design parameters related to drilled pier foundations have been prepared based on the field explorations, further observation of the selected bulk samples in the laboratory, published references, and engineering judgment. In general, the design parameters were developed from the observed material type and the SPT data collected. Piles should be designed in in accordance with skin friction and end bearing pressures provided in Tables 2 and 3 below. January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 8 HWA GEOSCIENCES INC. Table 2: Drilled Pier Design Parameters (0-1,500 feet South of S 288th St) Soil Unit Depth Ultimate Skin Friction Ultimate End Bearing Fill Soil 0-10 feet 200 psf - Weathered Native 10-20 feet 1,000 psf 10 ksf Till 20-30 feet 2,000 psf 20 ksf Notes: psf = pounds per square foot ksf = kips per square foot Table 3: Drilled Pier Design Parameters (Near Ravine by Redondo Road S) Soil Unit Depth Ultimate Skin Friction Ultimate End Bearing Stiff Silts 0-18 feet 400 psf 5 ksf Till 18-30 feet 2,000 psf 20 ksf Ultimate uplift capacities of piles can be assumed to be equal to ½ of the calculated ultimate skin friction value of the pile plus the weight of the pile materials. Pier calculations should incorporate a factor of safety of 3.0 for end bearing capacity and 2.0 for skin friction. HWA recommends neglecting any capacity derived from the upper 2 feet of material overlying the site. Allowable lateral pressures will be dependent on the pile dimensions and materials to be used. To calculate lateral capacities of the piles the following L-pile parameters should be utilized. Table 4: L-Pile Parameters Drilled Pier Design Parameters (0-1,500 feet South of S 288th St) Soil Unit Depth Soil Effective Unit Weight Soil Friction Angle Soil Modulus (k) Sand (Reese) 0-10 feet 110 pcf 26 degrees 20 pci Sand (Reese) 10-20 feet 125 pcf 32 degrees 90 pci Sand (Reese) 20-30 feet 135 pcf 38 degrees 250 pci Notes: pcf = pounds per cubic foot pci = pounds per cubic inch Table 5: Drilled Pier L-Pile Parameters (Near Ravine by Redondo Road S) L-Pile Soil Type Depth Soil Effective Unit Weight Soil Friction Angle Soil Modulus (k) Sand (Reese) 0-18 feet 110 pcf 27 degrees 25 pci Sand (Reese) 18-30 feet 135 pcf 38 degrees 250 pci HWA recommends that the drilling contractor review the field exploration logs of this report before starting excavations for the drilled piles. If groundwater or sloughing soils are encountered, it should be expected that the advancement of casing and placement of concrete January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 9 HWA GEOSCIENCES INC. will be more difficult and special measures will be required. A representative of the Geotechnical Engineer should be on site to observe and document the installation of the deep foundation system. When the drilling processes are completed for the pile, the reinforcing steel and the concrete should be placed immediately after the final cleanout pass is conducted on the base. The tremie method of concrete placement should be adopted when placing concrete below the groundwater table to prevent segregation of the concrete materials. If concrete is placed by the free-fall method into a dry excavation, it should be placed to avoid contact with the excavation sidewalls to prevent segregation. During simultaneous concrete placement and casing removal operations, sufficient concrete should be maintained inside the casing to offset the hydrostatic head of the ground water outside the casing and minimize the intrusion of soil into the concrete. Concrete placed in the pile excavations should have a slump in the range of 7 to 9 inches to reduce the potential for the formation of voids as the temporary pier casing is extracted. The concrete mix should be designed to attain the required 28-day design strength when placed at this slump. 4.4.3 Pile Construction Monitoring Full time observation of the pile installation, by a person with knowledge of the geotechnical aspects of the project, is recommended to determine if bearing soil and proper embedment depths have been reached. The contractor should submit their procedures for pile installation to the Geotechnical Engineer for approval prior to the start of construction. 4.5 RETAINING WALL STRUCTURES Retaining walls along the site’s alignment are to consist of either Cast-in-Place (CIP) walls or Structural Earth Walls (SEW). Most of these walls are anticipated to be no taller than 4 feet. Walls taller than 4 feet will need to be engineered in accordance with the design recommendations provided in this report. 4.5.1 Wall Design Recommendations Most of the site retaining walls will consist of Structural Earth Walls (SEW) that are less than 4 feet tall. If SEWs are to exceed 4 feet they will need to be engineered and will likely require grid reinforcement. SEWs consist of a proprietary wall system that the wall supplier will need to design for internal stability. HWA understands that CIP concrete walls may be utilized along some portions of the alignment. These walls are planned in areas where higher structural loads will need to be resisted or inadequate distance exists to allow for grid reinforcement of the walls. Walls should be imbedded a minimum of 2 feet below surface grades for walls over 4 feet in height or 1 foot for walls 4 feet or less. However, if the lower side of the wall is on a slope, the base of the wall must be at an elevation that provides at least 5 feet of soil laterally from the edge January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 10 HWA GEOSCIENCES INC. of the footing to the surface exposure of the slope. For example, if the wall is on a 2Horizontal:1Vertical slope, a footing would need to extend down at least 2½ feet below surface grades to allow for a 5-foot distance from the edge of footing to the surface exposure of the slope. The walls should be designed in accordance with the AASHTO LRFD Bridge Design Specifications (AASHTO, 2020) and Section 6-13.3(2)A of the 2020 WSDOT Standard Specifications. We recommend the walls be designed using the parameters presented in Tables 6 and 7 depending on location. For the Extreme Event Limit State, the wall shall be designed for a horizontal seismic acceleration coefficient kh of one-half the peak ground acceleration or 0.247g and a vertical seismic acceleration coefficient kv of 0.0g (assuming the wall is free to move during a seismic event). Resistance factors of 0.65 and 1.0 should be used for static (non- seismic) and seismic conditions, respectively. Table 6: Recommended Wall Design Parameters North of S Dash Point Road Soil Properties Wall Backfill* Retained Soil* Foundation Soil Unit Weight (pcf) 135 135 125 Friction Angle (deg) 34 34 30 Cohesion (psf) 0 0 0 * Assumes the use of Gravel Borrow, as specified in Section 9-03.14(1) of WSDOT Standard Specifications. However, if geogrid reinforcing is to be used CSBC should be utilized instead of gravel borrow. Table 7: Recommended Wall Design Parameters South of S Dash Point Road Soil Properties Wall Backfill* Retained Soil* Foundation Soil Unit Weight (pcf) 135 135 130 Friction Angle (deg) 34 34 36 Cohesion (psf) 0 0 0 * Assumes the use of Gravel Borrow, as specified in Section 9-03.14(1) of WSDOT Standard Specifications. However, if geogrid reinforcing is to be used CSBC should be utilized instead of gravel borrow. 4.5.2 Wall Subgrade Preparation Subgrade preparation is important to limit differential settlement of the walls and maintain global stability. All organic material should be removed from beneath the entire footprint of the walls prior to placing material. Loose or soft soil, as determined by HWA, should be removed and replaced with “Structural Backfill” or be suitably compacted. All areas on which the walls will bear should be graded level perpendicular to the wall face and compacted in accordance with Section 2-03.3(14)D of the WSDOT Standard Specifications (WSDOT, 2020), except the relative compaction should be tested using the ASTM D 1557 (Modified Proctor) method. January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 11 HWA GEOSCIENCES INC. We recommend an HWA geotechnical engineer, or their representative, be present during construction to verify the assumptions made for the foundations of the walls are met. The depth and extent of excavation will be directed by the geotechnical engineer on site. We recommend the bottom of the retaining walls be placed on a 1-foot-thick leveling pad consisting of Crushed Surfacing Base Course (CSBC) meeting the requirements of Section 9- 03.9(3) of the WSDOT Standard Specifications (WSDOT, 2020) and compacted to 95 percent of Modified Proctor maximum dry density, as determined by ASTM D 1557. This leveling pad should be graded to establish the proper wall batter. If very soft soil conditions are encountered below the base of a proposed foundation an additional 12 inches of over-excavation may be necessary (a total of 2 feet below the base of the wall). If firm soils are encountered to this depth additional CSBC should be place and compacted in the over-excavated area. However, if soft soils continue to depths greater than 2 feet and complete removal of soft soil is not reasonable, then the bottom 12 inches of over-excavated area should be backfilled with 2-4 inch quarry spalls, railroad ballast, or other approved materials to stabilize the soil. This material should be compacted or tamped in place and a layer of separations fabric (such as Mirafi® 140N or equivalent) should be placed above it followed by 12 inches of CSBC compacted to 95 of Modified Proctor (ASTM D1557). Wall foundations founded in this manner can be designed using an allowable bearing pressure of 2,000 psf. A 6-inch-diameter perforated drainpipe should be installed behind the base of the walls such that it will collect and convey all ground water from behind the walls. The drainpipe should be sloped to drain and routed to an appropriate discharge location. 4.5.3 Cantilevered Soldier Pile Walls Soldier pile walls consist of steel beams that are concreted into drilled vertical holes located along the wall alignment, typically 8 feet on center. Timber lagging is typically installed behind the flanges of the steel beams to retain the soil located between the soldier piles. Geotechnical design recommendations for each of these components of the soldier pile system are presented in the following sections. Soldier Piles We recommend that soldier pile walls be designed in accordance with the equivalent fluid pressures provided in Tables 8 and 9. Table 8: Equivalent Fluid Pressure for Soldier Pile Walls (0-1500 feet S of S 288th St) Soil Unit Depth Active Passive Fill Soil 0-10 feet 42 pcf 290 pcf Weathered Native 10-20 feet 39 pcf 400 pcf Till 20-30 feet 32 pcf 550 pcf January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 12 HWA GEOSCIENCES INC. Table 9: Equivalent Fluid Pressure for Soldier Pile Walls (Near Ravine by Redondo Road S) Soil Unit Depth Active Passive Fill and Stiff Native Soil 0-18 feet 40 pcf 300 pcf Till 18-30 feet 32 pcf 550 pcf If soldier piles are to be used, based on the expected cut heights of up to 10 feet on the site, HWA anticipates that any soldier pile wall design will not include tiebacks. If it is later determined that tiebacks are necessary, HWA should be notified to provide additional recommendations. The earth pressures presented in Tables 8 and 9 represent the estimated loads that will be applied to the wall system for various wall heights and assume a fully-drained conditions (no hydrostatic pressure is allowed to build up) above the base of the excavation. Active earth pressures should be assumed to act along the entire length of the exposed height of wall and passive pressures should be assumed to act on areas equivalent to twice the width of the grouted soldier pile column below the exposed height of the wall. The earth pressures presented in Table 8 and 9 do not include the external loads such as neighboring footings or traffic surcharges. For loads exerted by existing footings or other loads that currently exist on the site, see Figure 3 for recommendations on surcharge loading on the wall. Other surcharge loads, such as cranes, construction equipment or construction staging areas, should be considered by HWA on a case-by-case basis. In Tables 8 and 9, no seismic pressures have been included; if the wall system is to be permanent, seismic pressures will need to be accounted for. We recommend that the embedded portion of the soldier piles be at least 2 feet in diameter and extend a minimum distance of 5 feet into bearing soil to resist “kick-out.” Bearing soils are anticipated to be around 5 to 10 feet deep near S 288th Street and within the upper 5 feet near the ravine by Redando Road S. The axial capacity of the soldier piles must resist the downward component of the anchor loads and other vertical loads, as appropriate. We recommend soldier piles be designed using end bearing values equivalent to those provided in Section 4.4.2 (Tables 2 and 3). The allowable end bearing values should be applied to the base area of the drilled hole into which the soldier pile is concreted. These allowable end bearing values assume that the shaft bottom is cleaned out immediately prior to concrete placement. Due to the relatively high ground water and the presence of loose and soft soils, casing, drilling mud, and other means of stabilizing the drilled hole may be required during solider pile installation to prevent cave-ins, sloughing, and bottom blow-in. Lagging We recommend that the temporary timber lagging be sized using the procedures outlined in the Federal Highway Administration’s Geotechnical Engineering Circular No. 4. The site soils are best described as competent soils. Table 10 presents recommend timber lagging thicknesses as a January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 13 HWA GEOSCIENCES INC. function of soldier pile clear span and depth. Shotcrete lagging can be used as an alternative to timber lagging, depending upon the contractor’s preference. Table 10: Recommended Lagging Thickness for Spans Between Piles at Depth of 0-30 feet Width of span Between Piles (feet) 5 6 7 8 9 10 Thickness of Lagging (inches) 2 3 3 3 4 4 Lagging should be installed promptly after excavation, especially in areas where groundwater is present or where clean sand and gravel soils are present and caving soils conditions are likely. The workmanship associated with lagging installation is important for maintaining the integrity of the excavation. The space behind the lagging should be filled with soil as soon as practicable. The voids behind the lagging should be backfilled immediately or within a single shift, depending on the selected method of backfill. Filter and drainage materials will be required to prevent fines migration through the gaps between laggings. Placement of backfill will help reduce the risk of voids developing behind the wall and damage to existing improvements located behind the wall. CDF is a suitable option for the use of backfill behind the walls. CDF will reduce the volume of voids present behind the wall. Based on our experience, the voids between each CDF lift are sufficient for preventing the buildup of hydrostatic pressure behind the wall. Other types of lagging or backfill may be considered but should be approved by HWA prior to construction. If soldier pile walls will be permanent, then the material used in their construction should be resistant degradation and corrosion. 4.6 STORMWATER MANAGEMENT The increased stormwater associated with the proposed project will necessitate upgraded stormwater management facilities. As part of our scope of services, HWA performed an evaluation of the subsurface soil conditions to determine the site’s suitability for infiltration. The first step in this process was to observe wet season ground water conditions and the subsurface soil materials. Most of the alignment is predominantly underlain by glacial till deposits. These soils are very dense and possess high fines contents, as a result they are not generally good for infiltration. More permeable advance outwash soils were found near the intersection of S Dash Point Road and 16th Avenue S but ground water was observed to be as shallow as 2 feet below the existing ground surface in this area at the time of our investigation. Infiltration rates within till soil are generally on the order of less than 0.1 of an inch per hour and use of infiltration is not generally recommended when groundwater highs are less than 5 feet below the base of an infiltration system. As such, based on the observations made during our investigation onsite, infiltration is likely infeasible on this site. January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 14 HWA GEOSCIENCES INC. 4.7 PAVEMENT DESIGN Estimated loading for the proposed trail was not provided the HWA and pavement sections are anticipated to be provided by others. However, based on the observed near surface conditions along the alignment, provided the subgrades are compacted to a firm and unyielding condition HWA recommends that a California Bearing Ratio (CBR) value of 10 percent be utilized in design. This is based on at least 2 feet of soil under the pavement consisting of the sandy soils observed during our investigation. If other soils are noted during construction alterations to the CBR value may be necessary. 4.8 GENERAL EARTHWORK 4.8.1 Dewatering Ground water was encountered in borings BH-1, BH-2 and HAB-1 at the time of our explorations and not in HAB-2 through HAB-4 at depths as shallow as 2 feet. Much of the shallow groundwater encountered was likely is perched water and may be seasonal in nature. Dewatering will be the responsibility of the contractor, but groundwater flows are not anticipated to require a complex dewatering plan and are anticipated to be manageable by use of sumps and pumps during construction. Potential issues related to the presence of ground water could be mitigated by performing construction work in the drier summer months when water levels are anticipated to be lower. 4.8.2 Structural Fill Most of the site soils have a high fines content and are expected to be highly moisture sensitive. The native silts are not recommended for reuse, but the glacial till and outwash soil may be used as structural fill, provided they can be suitably moisture conditioned to achieve the required compaction. If imported structural fill is used, we recommend that it consist of clean, free- draining, granular soils free from organic matter or other deleterious materials. The structural fill material should be less than 4 inches in maximum particle dimension, with less than 7 percent fines (portion passing the U. S. Standard No. 200 sieve), as specified for “Gravel Borrow” in Section 9-03.14(1) of the WSDOT Standard Specifications (WSDOT, 2020). The fine-grained portion of structural fill soils should be non-plastic. 4.8.3 Compaction Structural fill soils should be moisture conditioned and compacted to the requirements specified in Section 2-03.3(14)C, Method C, of the WSDOT Standard Specifications (WSDOT, 2020); except the standard of compaction achieved shall not be less than 95% of the maximum dry density (MDD) determined for the fill material by test method ASTM D1557 (Modified Proctor). Subgrade compaction in roadbed areas should conform to the requirements of Section 2-06.3(1) of the WSDOT Standard Specifications (WSDOT, 2020). January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 15 HWA GEOSCIENCES INC. Achievement of proper density of a compacted fill depends on the size and type of compaction equipment, the number of passes, thickness of the layer being compacted, and soil moisture- density properties. In areas where limited space restricts the use of heavy equipment, smaller equipment can be used, but the soil must be placed in thin enough layers to achieve the required relative compaction. Generally, loosely compacted soils result from poor construction technique and/or improper moisture content. Soils with high fines contents are particularly susceptible to becoming too wet, and coarse-grained materials easily become too dry, for proper compaction. 4.8.4 Wet Weather Earthwork General recommendations relative to earthwork performed in wet weather or in wet conditions are presented below. These recommendations should be incorporated into the contract specifications. • Earthwork should be performed in small areas to minimize exposure to wet weather. Excavation of unsuitable and/or softened soil should be followed promptly by placement and compaction of clean structural fill. The size and type of construction equipment used may need to be limited to prevent soil disturbance. Under some circumstances, it may be necessary to excavate soils with a backhoe to minimize subgrade disturbance caused by equipment traffic. • For wet weather conditions, the allowable fines content of the structural fill should be reduced to no more than 5 percent by weight of the portion of the fill material passing the ¾-inch sieve. The fines should be non-plastic. It should be noted this is an additional restriction on the structural fill materials specified. • The ground surface within the construction area should be graded to promote surface water run-off and to prevent ponding. • Within the construction area, the ground surface should be sealed on completion of each shift by a smooth drum vibratory roller, or equivalent, and under no circumstances should soil be left uncompacted and exposed to moisture infiltration. • Bales of straw and/or geotextile silt fences should be strategically located to control erosion and the movement of soil. 4.8.5 Temporary Excavations Maintenance of safe working conditions, including temporary excavation stability, is the responsibility of the contractor. In accordance with Part N of Washington Administrative Code (WAC) 296-155, latest revisions, all temporary cuts in excess of 4 feet in height must be either sloped or shored prior to entry by personnel. The existing near surface fill soils are generally classified as Type C soils per WAC 296-155. Where shoring is not used, temporary cuts in Type C soils should be sloped no steeper than 1½H:1V (horizontal:vertical). Where glacial till soils are encountered, the cut slopes can be increased. Glacial till soils are generally classified as January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 16 HWA GEOSCIENCES INC. Type A soils per WAC 296-155. Where shoring is not used, temporary cuts in Type A soils should be sloped no steeper than 3/4H:1V (horizontal:vertical). 5. CONDITIONS AND LIMITATIONS We have prepared this report for the City of Federal Way and KPFF, Inc. for use in design of this project. This report should be provided in its entirety to prospective contractors for bidding and estimating purposes; however, the conclusions and interpretations presented in this report should not be construed as our warranty of the subsurface conditions. Experience has shown that soil and ground water conditions can vary significantly over small distances. Inconsistent conditions can occur between explorations and may not be detected by a geotechnical study. If, during future site operations, subsurface conditions are encountered which vary appreciably from those described herein, HWA should be notified for review of the recommendations of this report, and revision of such if necessary. We recommend HWA be retained to review the plans and specifications to verify that our recommendations have been interpreted and implemented as intended. Sufficient geotechnical monitoring, testing, and consultation should be provided during construction to confirm the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should conditions revealed during construction differ from those anticipated, and to verify that the geotechnical aspects of construction comply with the contract plans and specifications. Within the limitations of scope, schedule and budget, HWA attempted to execute these services in accordance with generally accepted professional principles and practices in the fields of geotechnical engineering and engineering geology in the area at the time the report was prepared. No warranty, express or implied, is made. The scope of our work did not include environmental assessments or evaluations regarding the presence or absence of hazardous substances in the soil or ground water at this site. HWA does not practice or consult in the field of safety engineering. We do not direct the contractor’s operations, and cannot be responsible for the safety of personnel other than our own on the site. As such, the safety of others is the responsibility of the contractor(s). The contractor(s) should notify the owner if it is considered that any of the recommended actions presented herein are unsafe.  January 12, 2021 HWA Project No. 2019-151-21 Geotechnical Report 18 HWA GEOSCIENCES INC. 6. REFERENCES American Associate of State Highway and Transportation Officials (AASHTO), 2011, Guide Specifications for LRFD Seismic Bridge Design, 2nd Edition, Washington D.C. AASHTO, 2020, LRFD Bridge Design Specifications, 9th Edition, Washington D.C. Booth, D.B., Troost, K.A., and Wisher, A.P., 2007. Geologic Map of King County. GeoMapNW, University of Washington. WSDOT, 2019, Bridge Design Manual (LRFD), M 23-50.19, July 2019. WSDOT, 2020, Standard Specifications for Road, Bridge, and Municipal Construction, Washington State Department of Transportation. © 2020 Microsoft Corporation © 2020 DigitalGlobe ©CNES (2020) Distribution Airbus DS © 2020 HERE BFM 2019-151-21 SITE AND VICINITY MAP PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTON 0 500'1000'1500'2000' SCALE: 1" = 1000' VICINITY MAP SITE MAP 0 1000'2000'3000'4000' SCALE: 1" = 2000' SITE ZN 1 DRAWN BY: PROJECT # S:\2019 PROJECTS\2019-151-21 FEDERAL WAY, NON MOTORIZED PATH\CAD\2019-151-21 PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR.DWG <1> Plotted: 4/7/2020 1:20 PM CHECK BY: FIGURE NO.: DBE/MWBE AREA OF WORK © 2020 Microsoft Corporation © 2020 DigitalGlobe ©CNES (2020) Distribution Airbus DS © 2020 Microsoft Corporation © 2020 DigitalGlobe ©CNES (2020) Distribution Airbus DS SITE & EXPLORATION PLAN 2019-151-21 BASE MAP PROVIDED BY: BING AND SURVEYOR 0 60 120 180 240 SCALE: 1" = 120' PACIFIC HIGHWAY S. Scale: 1" = 120'-0" EXPLORATION LEGEND HAB1 AUGER BORING DESIGNATION AND APPROX. LOCATION (HWA GEOSCIENCES, INC.)S. 308TH ST.ZN BFM FIGURE NO.: PROJECT NO.: DRAWN BY: CHECK BY: S:\2019 PROJECTS\2019-151-21 FEDERAL WAY, NON MOTORIZED PATH\CAD\2019-151-21 PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR.DWG <2A> Plotted: 5/12/2020 1:39 PM 2A DBE/MWBE HAB6 PACIFIC H I G H W A Y S . PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTON MATCHLINE 2B16TH AVE S.S. 304TH ST. © 2020 Microsoft Corporation © 2020 DigitalGlobe ©CNES (2020) Distribution Airbus DS BASE MAP PROVIDED BY: BING AND SURVEYOR 0 60 120 180 240 SCALE: 1" = 120' PACIFIC HIGHWAY S. Scale: 1" = 120'-0" EXPLORATION LEGEND HAB1 AUGER BORING DESIGNATION AND APPROX. LOCATION (HWA GEOSCIENCES, INC.) ZN BFMSITE & EXPLORATION PLAN 2019-151-21 FIGURE NO.: PROJECT NO.: DRAWN BY: CHECK BY: S:\2019 PROJECTS\2019-151-21 FEDERAL WAY, NON MOTORIZED PATH\CAD\2019-151-21 PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR.DWG <2B> Plotted: 5/12/2020 1:39 PM 2B DBE/MWBE PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTONMATCHLINE 2AMATCHLINE 2CPACIFIC HIGHWAY S. HAB5 HAB4 HAB3 © 2020 Microsoft Corporation © 2020 DigitalGlobe ©CNES (2020) Distribution Airbus DS SITE & EXPLORATION PLAN 2019-151-21 BASE MAP PROVIDED BY: BING AND SURVEYOR 0 60 120 180 240 SCALE: 1" = 120' PACIFIC HIGHWAY S. Scale: 1" = 120'-0" EXPLORATION LEGEND HAB1 AUGER BORING DESIGNATION AND APPROX. LOCATION (HWA GEOSCIENCES, INC.) ZN BFM FIGURE NO.: PROJECT NO.: DRAWN BY: CHECK BY: S:\2019 PROJECTS\2019-151-21 FEDERAL WAY, NON MOTORIZED PATH\CAD\2019-151-21 PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR.DWG <2C> Plotted: 5/12/2020 1:41 PM 2C DBE/MWBES. DASH POINT RD.PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTONMATCHLINE 2BMATCHLINE 2DPACIFIC HIGHWAY S. BH-5 BH-4 HAB1 BH-3 BH-1 BORING DESIGNATION AND APPROX. LOCATION (HWA GEOSCIENCES, INC.) HAB2 © 2020 Microsoft Corporation © 2020 DigitalGlobe ©CNES (2020) Distribution Airbus DS SITE & EXPLORATION PLAN 2019-151-21 BASE MAP PROVIDED BY: BING AND SURVEYOR 0 60 120 180 240 SCALE: 1" = 120' PACIFIC HIGHWAY S. Scale: 1" = 120'-0" EXPLORATION LEGEND ZN BFM FIGURE NO.: PROJECT NO.: DRAWN BY: CHECK BY: S:\2019 PROJECTS\2019-151-21 FEDERAL WAY, NON MOTORIZED PATH\CAD\2019-151-21 PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR.DWG <2D> Plotted: 5/12/2020 1:40 PM 2D DBE/MWBE PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTONMATCHLINE 2CPACIFIC HIGHWAY S.S. 288TH ST.BH-2 BH-1 BH-1 BORING DESIGNATION AND APPROX. LOCATION (HWA GEOSCIENCES, INC.) FIGURE NO. PROJECT NO. APPENDIX A HWA EXPLORATION LOGS HWA EXPLORATIONS HWA GeoSciences Inc. (HWA) conducted six (6) hand auger borings and five (5) machine drilled borings in support of the design of the proposed non-motorized path in Federal Way, Washington. The machine drilled borings (BH-1 through BH-5) were conducted by Geologic Drill Partners, Inc. of Bellevue, Washington, on January 13, 2020 using a limited access Mini Bobcat Drill Rig equipped for hollow stem auger drilling and a cathead hammer. The six hand auger borings (HAB-1 through HAB-6) were conducted by an HWA geotechnical engineer and geologist and were advanced using a hand auger. Standard Penetration Test (SPT) sampling was performed using a 2-inch outside diameter split- spoon sampler driven by a 140-pound manual rope and cathead hammer in borings BH-1 and BH-2. During the SPT, samples were obtained by driving the sampler 18 inches into the soil with the hammer free-falling 30 inches. The numbers of blows required for each 6 inches of penetration were recorded. The Standard Penetration Resistance (“N-value”) of the soil is calculated as the number of blows required for the final 12 inches of penetration. This resistance, or N-value, provides an indication of relative density of granular soils and the relative consistency of cohesive soils; both indicators of soil strength and foundation bearing capacity. In the hand auger boring dynamic cone penetrometer (DCP) tests were conducted on the soils to assess the soil relative densities/consistencies. DCP testing is conducted by driving a thin pipe with an tapered end cap on it that is driven down using a weight. Measurements are taken on the amount of advancement per blow. This information can then be used to assess the soils relative density/consistency. The locations of the boreholes were determined approximately in the field using GPS coordinates and are shown on the Site and Exploration Plan, Figure 2. A geotechnical engineer from HWA logged each exploration and recorded all pertinent information. Soil samples obtained from the boreholes were classified in the field and representative portions were sealed in plastic bags. These soil samples were then returned to our Bothell, Washington, laboratory for further examination and testing. Pertinent information including soil sample depths, stratigraphy, soil engineering characteristics, and ground water occurrence was recorded. The stratigraphic contacts shown on the individual exploration logs represent the approximate boundaries between soil types; actual transitions may be more gradual. The soil and ground water conditions depicted are only for the specific date and locations reported and, therefore, are not necessarily representative of other locations and times. A legend of the terms and symbols used on the exploration logs is presented in Figure A-1. Summary logs of the borehole explorations are presented in Figures A-2 and A-12. A-1 PACIFIC HIGHWAY NON- MOTORIZED CORRIDOR FEDERAL WAY, WASHINGTON 2019-151-21 SYMBOLS USED ON EXPLORATION LOGS LEGEND OF TERMS AND Clean Gravel (little or no fines) More than 50% of Coarse Fraction Retained on No. 4 Sieve Gravel with SM SC ML MH CH OH RELATIVE DENSITY OR CONSISTENCY VERSUS SPT N-VALUE Very Loose Loose Medium Dense Very Dense Dense N (blows/ft) 0 to 4 4 to 10 10 to 30 30 to 50 over 50 Approximate Relative Density(%) 0 - 15 15 - 35 35 - 65 65 - 85 85 - 100 COHESIVE SOILS Consistency Very Soft Soft Medium Stiff Stiff Very Stiff Hard N (blows/ft) 0 to 2 2 to 4 4 to 8 8 to 15 15 to 30 over 30 Approximate Undrained Shear Strength (psf) <250 250 - No. 4 Sieve Sand with Fines (appreciable amount of fines) amount of fines) More than 50% Retained on No. 200 Sieve Size Sand and Sandy Soils Clean Sand (little or no fines) 50% or More of Coarse Fraction Passing Fine Grained Soils Silt and Clay Liquid Limit Less than 50% 50% or More Passing No. 200 Sieve Size Silt and Clay Liquid Limit 50% or More 500 500 - 1000 1000 - 2000 2000 - 4000 >4000 DensityDensity USCS SOIL CLASSIFICATION SYSTEM Coarse Grained Soils Gravel and Gravelly Soils Highly Organic Soils GROUP DESCRIPTIONS Well-graded GRAVEL Poorly-graded GRAVEL Silty GRAVEL Clayey GRAVEL Well-graded SAND Poorly-graded SAND Silty SAND Clayey SAND SILT Lean CLAY Organic SILT/Organic CLAY Elastic SILT Fat CLAY Organic SILT/Organic CLAY PEAT MAJOR DIVISIONS GW SP CL OL PT GP GM GC SW COHESIONLESS SOILS Fines (appreciable FIGURE: LEGEND 2020-081.GPJ 12/31/20 PROJECT NO.: Coarse sand Medium sand SIZE RANGE Larger than 12 in Smaller than No. 200 (0.074mm) Gravel time of drilling) Groundwater Level (measured in well or AL CBR CN Atterberg Limits: LL = Liquid Limit California Bearing Ratio Consolidation Resilient Modulus Photoionization Device Reading Pocket Penetrometer Specific Gravity Triaxial Compression Torvane 3 in to 12 in 3 in to No 4 (4.5mm) No. 4 (4.5 mm) to No. 200 (0.074 mm) COMPONENT DRY Absence of moisture, dusty, dry to the touch. MOIST Damp but no visible water. WET Visible free water, usually soil is below water table. Boulders Cobbles Coarse gravel Fine gravel Sand MOISTURE CONTENT COMPONENT PROPORTIONS Fine sand Silt and Clay 5 - 12% PROPORTION RANGE DESCRIPTIVE TERMS Clean Slightly (Clayey, Silty, Sandy) 30 - 50% Components are arranged in order of increasing quantities. Very (Clayey, Silty, Sandy, Gravelly) 12 - 30%Clayey, Silty, Sandy, Gravelly open hole after water level stabilized) Groundwater Level (measured at 3 in to 3/4 in 3/4 in to No 4 (4.5mm) No. 4 (4.5 mm) to No. 10 (2.0 mm) No. 10 (2.0 mm) to No. 40 (0.42 mm) No. 40 (0.42 mm) to No. 200 (0.074 mm) PL = Plastic Limit DD DS GS K MD MR PID PP SG TC TV Dry Density (pcf) Direct Shear Grain Size Distribution Permeability Approx. Shear Strength (tsf) Percent Fines%F Moisture/Density Relationship (Proctor) Approx. Compressive Strength (tsf) Unconfined CompressionUC (140 lb. hammer with 30 in. drop) Shelby Tube Small Bag Sample Large Bag (Bulk) Sample Core Run Non-standard Penetration Test 2.0" OD Split Spoon (SPT) NOTES: Soil classifications presented on exploration logs are based on visual and laboratory observation. Density/consistency, color, modifier (if any) GROUP NAME, additions to group name (if any), moisture content. Proportion, gradation, and angularity of constituents, additional comments. (GEOLOGIC INTERPRETATION) Please refer to the discussion in the report text as well as the exploration logs for a more complete description of subsurface conditions. Soil descriptions are presented in the following general order: < 5% 3-1/4" OD Split Spoon with Brass Rings (3.0" OD split spoon) TEST SYMBOLS SAMPLE TYPE SYMBOLS GROUNDWATER SYMBOLS COMPONENT DEFINITIONS Loose to medium dense, dark olive-brown, silty SAND, moist. Abundant rootlets. (TOPSOIL) Medium dense to very dense, dark olive-brown, silty GRAVEL with sand, moist. (WEATHERED GLACIAL TILL) Hand auger terminated at about 1-1/2 feet due to refusal. No ground water seepage encountered during exploration. Hand auger abandoned with excavated material. SM GM S-1 Natural Water Content Liquid Limit HAND HOLE: A-2 HAB-1 PAGE: 1 of 1SYMBOLUSCS SOIL CLASSGROUNDWATERWater Content (%)PEN. RESISTANCEOTHER TESTS(140 lb. weight, 30" drop) 0 20 40 60 80 100 Standard Penetration Test Plastic Limit(blows/6 inches)DESCRIPTION SAMPLE TYPESAMPLE NUMBERand therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DRILLING COMPANY: HWA GeoSciences Inc. SAMPLING METHOD: Grab LOCATION: See Figure 2 DRILLING METHOD: Hand Auger with DCP DATE STARTED: 3/18/2020 LOGGED BY: Z. Ngoma DATE COMPLETED: 3/18/2020 SURFACE ELEVATION: CASING ELEVATION feet feet HANDHOL 2019-151-21.GPJ 5/7/20 PROJECT NO.:2019-151-21 PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR FIGURE: 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTONDEPTH (feet)DEPTH (feet)0 1 2 3 4 5 0 1 2 3 4 5 >> >> >> >>>> Loose to medium dense, dark brown, silty SAND, moist. Abundant rootlets. (TOPSOIL) Medium dense to very dense, dark gray, silty SAND with gravel, moist. Gravel was angular. Pieces of asphalt concrete. Abundant organics. (FILL) Seep noted at 2 feet below ground surface (bgs). Dense to very dense, rust-mottled, olive-gray, silty SAND with gravel, moist. (GLACIAL TILL) Hand auger terminated at about 3 feet due to refusal. Ground water seepage encountered at about 2 feet during exploration. Hand auger abandoned with excavated material. SM SM SM S-1 S-2 Natural Water Content Liquid Limit HAND HOLE: A-3 HAB-2 PAGE: 1 of 1SYMBOLUSCS SOIL CLASSGROUNDWATERWater Content (%)PEN. RESISTANCEOTHER TESTS(140 lb. weight, 30" drop) 0 20 40 60 80 100 Standard Penetration Test Plastic Limit(blows/6 inches)DESCRIPTION SAMPLE TYPESAMPLE NUMBERand therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DRILLING COMPANY: HWA GeoSciences Inc. SAMPLING METHOD: Grab LOCATION: See Figure 2 DRILLING METHOD: Hand Auger with DCP DATE STARTED: 3/18/2020 LOGGED BY: Z. Ngoma DATE COMPLETED: 3/18/2020 SURFACE ELEVATION: CASING ELEVATION feet feet HANDHOL 2019-151-21.GPJ 5/7/20 PROJECT NO.:2019-151-21 PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR FIGURE: 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTONDEPTH (feet)DEPTH (feet)0 1 2 3 4 5 0 1 2 3 4 5 >>>> >> >>>>>>>>>>>>>>>> Loose to medium dense, dark gray-brown, silty SAND, moist. Abundant rootlets. (TOPSOIL) Medium dense, dark olive-gray, silty SAND with gravel, moist. Abundant organics. (FILL) Medium dense to dense, brown, poorly graded, clean SAND, moist. Hand auger terminated at about 4 feet. No ground water seepage encountered during exploration. Hand auger abandoned with excavated material. SM SM SP S-1 S-2 Natural Water Content Liquid Limit HAND HOLE: A-4 HAB-3 PAGE: 1 of 1SYMBOLUSCS SOIL CLASSGROUNDWATERWater Content (%)PEN. RESISTANCEOTHER TESTS(140 lb. weight, 30" drop) 0 20 40 60 80 100 Standard Penetration Test Plastic Limit(blows/6 inches)DESCRIPTION SAMPLE TYPESAMPLE NUMBERand therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DRILLING COMPANY: HWA GeoSciences Inc. SAMPLING METHOD: Grab LOCATION: See Figure 2 DRILLING METHOD: Hand Auger with DCP DATE STARTED: 3/18/2020 LOGGED BY: Z. Ngoma DATE COMPLETED: 3/18/2020 SURFACE ELEVATION: CASING ELEVATION feet feet HANDHOL 2019-151-21.GPJ 5/7/20 PROJECT NO.:2019-151-21 PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR FIGURE: 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTONDEPTH (feet)DEPTH (feet)0 1 2 3 4 5 0 1 2 3 4 5 Loose to medium dense, dark brown, silty SAND, moist. Abundant rootlets. (TOPSOIL) Medium dense to dense, olive-gray, silty SAND with gravel, moist. (WEATHERED GLACIAL TILL) Hand auger terminated at about 1-1/2 feet due to refusal. No ground water seepage encountered during exploration. Hand auger abandoned with excavated material. SM SM S-1 Natural Water Content Liquid Limit HAND HOLE: A-5 HAB-4 PAGE: 1 of 1SYMBOLUSCS SOIL CLASSGROUNDWATERWater Content (%)PEN. RESISTANCEOTHER TESTS(140 lb. weight, 30" drop) 0 20 40 60 80 100 Standard Penetration Test Plastic Limit(blows/6 inches)DESCRIPTION SAMPLE TYPESAMPLE NUMBERand therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DRILLING COMPANY: HWA GeoSciences Inc. SAMPLING METHOD: Grab LOCATION: See Figure 2 DRILLING METHOD: Hand Auger with DCP DATE STARTED: 3/18/2020 LOGGED BY: Z. Ngoma DATE COMPLETED: 3/18/2020 SURFACE ELEVATION: CASING ELEVATION feet feet HANDHOL 2019-151-21.GPJ 5/7/20 PROJECT NO.:2019-151-21 PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR FIGURE: 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTONDEPTH (feet)DEPTH (feet)0 1 2 3 4 5 0 1 2 3 4 5 Loose to medium dense, olive-brown, silty SAND, moist. Trace gravel. Abundant rootlets. (TOPSOIL) Medium dense, olive-gray, silty SAND with gravel, moist. (WEATHERED GLACIAL TILL) Hand auger terminated at about 1-1/2 feet due to refusal. No ground water seepage encountered during exploration. Hand auger abandoned with excavated material. SM SM S-1 Natural Water Content Liquid Limit HAND HOLE: A-6 HAB-5 PAGE: 1 of 1SYMBOLUSCS SOIL CLASSGROUNDWATERWater Content (%)PEN. RESISTANCEOTHER TESTS(140 lb. weight, 30" drop) 0 20 40 60 80 100 Standard Penetration Test Plastic Limit(blows/6 inches)DESCRIPTION SAMPLE TYPESAMPLE NUMBERand therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DRILLING COMPANY: HWA GeoSciences Inc. SAMPLING METHOD: Grab LOCATION: See Figure 2 DRILLING METHOD: Hand Auger with DCP DATE STARTED: 3/18/2020 LOGGED BY: Z. Ngoma DATE COMPLETED: 3/18/2020 SURFACE ELEVATION: CASING ELEVATION feet feet HANDHOL 2019-151-21.GPJ 5/7/20 PROJECT NO.:2019-151-21 PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR FIGURE: 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTONDEPTH (feet)DEPTH (feet)0 1 2 3 4 5 0 1 2 3 4 5 >> Loose to medium dense, dark brown, slightly silty, SAND, moist. Trace gravel. Abundant rootlets. (FILL) Medium dense, olive-brown, silty SAND with gravel, moist. Medium dense to very dense, olive-gray, poorly graded SAND with silt, moist. Trace gravel. Hand auger terminated at about 1-1/2 feet due to refusal. No ground water seepage encountered during exploration. Hand auger abandoned with excavated material. SM SM SP SM S-1 S-2 Natural Water Content Liquid Limit HAND HOLE: A-7 HAB-6 PAGE: 1 of 1SYMBOLUSCS SOIL CLASSGROUNDWATERWater Content (%)PEN. RESISTANCEOTHER TESTS(140 lb. weight, 30" drop) 0 20 40 60 80 100 Standard Penetration Test Plastic Limit(blows/6 inches)DESCRIPTION SAMPLE TYPESAMPLE NUMBERand therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DRILLING COMPANY: HWA GeoSciences Inc. SAMPLING METHOD: Grab LOCATION: See Figure 2 DRILLING METHOD: Hand Auger with DCP DATE STARTED: 3/18/2020 LOGGED BY: Z. Ngoma DATE COMPLETED: 3/18/2020 SURFACE ELEVATION: CASING ELEVATION feet feet HANDHOL 2019-151-21.GPJ 5/7/20 PROJECT NO.:2019-151-21 PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR FIGURE: 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTONDEPTH (feet)DEPTH (feet)0 1 2 3 4 5 0 1 2 3 4 5 >>>> GS S-1 S-2 S-3 S-4 S-5 S-6 S-7 Asphalt concrete surface. 4 inches of Crushed Surfacing Base Course (CSBC). Loose, rust-mottled, olive-gray, silty SAND with gravel, moist. (FILL) Becomes yellow-brown with broken pieces of red brick and burned wood. Medium dense, rust-mottled, olive-gray, silty SAND with gravel, moist. (WEATHERED GLACIAL TILL) Dense, olive-gray, silty SAND with gravel, moist. (GLACIAL TILL) Becomes very dense. Borehole terminated at about 20-1/4 feet below ground surface (bgs). No ground water seepage observed during exploration. Borehole abandoned with 3/8-inch bentonite chips. 10-22-13 3-2-2 2-2-4 3-2-2 5-10-12 12-13-20 50/3" SM SM SM BORING-DSM 2019-151-21.GPJ 5/7/20 FIGURE:PROJECT NO.:2019-151-21 FEDERAL WAY, WASHINGTON 16TH AVE S (S 308TH ST TO S 288TH ST) PACIFIC HIGHWAY NON-MOTORIZED CORRIDORDEPTH(feet)0 5 10 15 20 25 410 405 400 395 390ELEVATION(feet)BH-1 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL0 10 20 30 40 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBERNatural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION OTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot A-8 Standard Penetration Test DATE COMPLETED: 3/27/2020 DRILLING COMPANY: Geologic Drill Partners DRILLING METHOD: Mini Bobcat Drill Rig, 2.25" ID HSA LOCATION: See Figure 2 DATE STARTED: 3/27/2020 SAMPLING METHOD: SPT w/ Cathead LOGGED BY: Z. Ngoma >> SURFACE ELEVATION: 414.0 feet GSS-1 S-2 S-3 S-4 S-5 Medium dense, rust-mottled, olive-gray, silty SAND with trace gravel, moist. (WEATHERED GLACIAL TILL) Dense, olive-gray, silty SAND with gravel, wet. Water-bearing sand lenses present. (GLACIAL TILL) Becomes very dense and moist. Water-bearing sand lenses absent. Refusal at 16-1/2 feet. Borehole terminated at about 16-1/2 feet below ground surface (bgs). Ground water seepage observed at about 5 feet bgs during exploration. Borehole abandoned with 3/8-inch bentonite chips. 4-7-11 7-17-28 25-19-19 7-17-15 33-31-50/5" SM SM BORING-DSM 2019-151-21.GPJ 5/7/20 FIGURE:PROJECT NO.:2019-151-21 FEDERAL WAY, WASHINGTON 16TH AVE S (S 308TH ST TO S 288TH ST) PACIFIC HIGHWAY NON-MOTORIZED CORRIDORDEPTH(feet)0 5 10 15 20 25 410 405 400 395 390ELEVATION(feet)BH-2 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL0 10 20 30 40 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBERNatural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION OTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot A-9 Standard Penetration Test DATE COMPLETED: 3/27/2020 DRILLING COMPANY: Geologic Drill Partners DRILLING METHOD: Mini Bobcat Drill Rig, 2.25" ID HSA LOCATION: See Figure 2 DATE STARTED: 3/27/2020 SAMPLING METHOD: SPT w/ Cathead LOGGED BY: Z. Ngoma >> SURFACE ELEVATION: 413.0 feet S-1 S-2 S-3 S-4 S-5 Dark brown, silty SAND, moist. Rootlets and other organics present. (TOPSOIL) Medium dense, rust-mottled, olive-gray, silty SAND, moist. Pieces of tree root and other organics present. (FILL) Becomes loose with minor organics present. Dense, rust-mottled, olive-gray, silty SAND with gravel, wet. Sand lenses present. (GLACIAL TILL) Becomes very dense and moist. Wet sand lenses no longer present. Refusal at about 16-1/2 feet. Borehole terminated at about 16-1/2 feet below ground surface (bgs). Ground water seepage observed at about 7-1/2 feet bgs during exploration. Borehole abandoned with 3/8-inch bentonite chips. 3-4-6 7-3-6 20-23-20 9-17-20 15-40-31 SM SM SM BORING-DSM 2019-151-21.GPJ 5/7/20 FIGURE:PROJECT NO.:2019-151-21 FEDERAL WAY, WASHINGTON 16TH AVE S (S 308TH ST TO S 288TH ST) PACIFIC HIGHWAY NON-MOTORIZED CORRIDORDEPTH(feet)0 5 10 15 20 25 425 420 415 410 405ELEVATION(feet)BH-3 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL0 10 20 30 40 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBERNatural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION OTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot A-10 Standard Penetration Test DATE COMPLETED: 3/26/2020 DRILLING COMPANY: Geologic Drill Partners DRILLING METHOD: Mini Bobcat Drill Rig, 2.25" ID HSA LOCATION: See Figure 2 DATE STARTED: 3/26/2020 SAMPLING METHOD: SPT w/ Cathead LOGGED BY: Z. Ngoma >> SURFACE ELEVATION: 427.0 feet GS AL GS S-1 S-2 S-3 S-4 S-5 S-6 Very loose, dark brown, silty SAND, moist. Rootlets and other organics present. (TOPSOIL) Dense, rust-mottled, olive-gray, silty SAND with gravel, moist. Blow counts likely exaggerated due to large pieces of gravel near the surface. (FILL) Loose, yellow-brown, poorly-graded SAND with silt, moist. Decomposed wood fragments. Medium stiff, olive-gray, SILT with Sand, moist. (NATIVE) Stiff, olive-gray, lean CLAY with sand, moist. Medium stiff, rust-mottled, olive-gray, SILT, wet. becomes moist Hard, gray, sandy SILT, moist. (GLACIAL TILL) Borehole terminated at about 21-1/2 feet below ground surface (bgs). Ground water seepage observed at about 11 feet bgs during exploration. Borehole abandoned with 3/8-inch bentonite chips. 12-18-16 5-3-2 6-3-4 2-3-8 5-4-3 8-24-41 SM SM SP SM ML CL ML ML BORING-DSM 2019-151-21.GPJ 5/7/20 FIGURE:PROJECT NO.:2019-151-21 FEDERAL WAY, WASHINGTON 16TH AVE S (S 308TH ST TO S 288TH ST) PACIFIC HIGHWAY NON-MOTORIZED CORRIDORDEPTH(feet)0 5 10 15 20 25 385 380 375 370 365ELEVATION(feet)BH-4 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL0 10 20 30 40 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBERNatural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION OTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot A-11 Standard Penetration Test DATE COMPLETED: 3/26/2020 DRILLING COMPANY: Geologic Drill Partners DRILLING METHOD: Mini Bobcat Drill Rig, 2.25" ID HSA LOCATION: See Figure 2 DATE STARTED: 3/26/2020 SAMPLING METHOD: SPT w/ Cathead LOGGED BY: Z. Ngoma >> SURFACE ELEVATION: 386.0 feet GS S-1 S-2 S-3 S-4 S-5 S-6 Very loose, dark brown, silty SAND, moist. Rootlets and other organics present. (TOPSOIL) Medium dense, olive-gray, silty SAND with gravel, moist. (FILL) Very dense, poorly-graded SAND with silt, wet. (ADVANCE OUTWASH) Becomes olive-brown and silt content decreases. Silt content increases. Becomes dense, olive-gray, and wet in the upper 6 inches of the sample. Becomes very dense and moist. Borehole terminated at about 21 feet below ground surface (bgs). Ground water seepage observed at about 4 feet bgs during exploration. Borehole abandoned with 3/8-inch bentonite chips. 34-14-12 14-18-40 28-24-31 17-40-44 15-22-28 28-50/6" SM SM SM SP SM SM BORING-DSM 2019-151-21.GPJ 5/7/20 FIGURE:PROJECT NO.:2019-151-21 FEDERAL WAY, WASHINGTON 16TH AVE S (S 308TH ST TO S 288TH ST) PACIFIC HIGHWAY NON-MOTORIZED CORRIDORDEPTH(feet)0 5 10 15 20 25 420 415 410 405 400ELEVATION(feet)BH-5 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL0 10 20 30 40 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBERNatural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION OTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot A-12 Standard Penetration Test DATE COMPLETED: 3/26/2020 DRILLING COMPANY: Geologic Drill Partners DRILLING METHOD: Mini Bobcat Drill Rig, 2.25" ID HSA LOCATION: See Figure 2 DATE STARTED: 3/26/2020 SAMPLING METHOD: SPT w/ Cathead LOGGED BY: Z. Ngoma >> >> >> >> SURFACE ELEVATION: 424.0 feet APPENDIX B LABORATORY TEST RESULTS LABORATORY INVESTIGATION Representative soil samples obtained from the explorations were placed in plastic bags to prevent loss of moisture and transported to our Bothell, Washington, laboratory for further examination and testing. Laboratory tests were conducted on selected soil samples to characterize relevant engineering and index properties of the site soils. The laboratory testing program was performed in general accordance with appropriate ASTM Standards, as outlined below. MOISTURE CONTENT OF SOIL: The moisture content of selected soil samples (percent by dry mass) was determined in general accordance with ASTM D 2216. The results are shown at the sampled intervals on the appropriate summary logs in Appendix A and in the material summary sheets in Appendix B (B-1 and B-3). PARTICLE SIZE ANALYSIS OF SOILS: Selected granular samples were tested to determine the particle size distribution of material in accordance with ASTM D 6913 (wash sieve or wash sieve and hydrometer methods). The results are summarized on the attached Particle-Size Distribution reports (Figures B-2, B- 4 and B-5, Appendix B), which also provide information regarding the classification of the samples and the moisture content at the time of testing. LIQUID LIMIT, PLASTIC LIMIT, AND PLASTICITY INDEX OF SOILS (ATTERBERG LIMITS): Selected sample was tested using method ASTM D 4318, multi-point method. The results are reported on the attached Liquid Limit, Plastic Limit, and Plasticity Index reports found in Figure B-6. HAB-1,S-1 1.0 1.1 8.6 44.0 43.0 13.1 GM Dark olive-brown, silty GRAVEL with sand HAB-3,S-2 2.5 2.6 7.8 9.7 86.9 3.4 SP Olive-brown, poorly graded SAND HAB-5,S-1 0.8 0.9 13.3 32.6 43.6 23.8 SM Light olive-brown, silty SAND with gravel(feet)TOP DEPTHSAMPLE DESCRIPTION Notes:ASTM SOILMOISTURECONTENT (%)ORGANIC% FINESSPECIFIC GRAVITYEXPLORATIONDESIGNATION1. This table summarizes information presented elsewhere in the report and should be used in conjunction with the report test, other graphs and tables, and the exploration logs. 2. The soil classifications in this table are based on ASTM D2487 and D2488 as applicable. MATERIAL PROPERTIES B-1 PAGE: 1 of 1 SUMMARY OF LIMITS (%) ATTERBERG BOTTOM DEPTHCONTENT (%)% SAND% GRAVELPIPLLL CLASSIFICATION(feet)2019-151-21PROJECT NO.: INDEX MATSUM 2 2019-151-21.GPJ 3/25/20 FIGURE: 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 43.0 86.9 43.6 (GM) Dark olive-brown, silty GRAVEL with sand (SP) Olive-brown, poorly graded SAND (SM) Light olive-brown, silty SAND with gravel #20 Fine Coarse DEPTH (ft)SYMBOL Gravel % Sand % Fines % 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES #10 SAND 10 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 S-1 S-2 S-1 9 8 13 50 SAMPLE B-2 0.00050.005 CLAY #100 0.5 50 Medium Fine 13.1 3.4 23.7 3/8" 5 Coarse #60#40 PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D422 HAB-1 HAB-3 HAB-5 SILT 3/4" GRAVEL % MC LL PL PI 90 GRAIN SIZE IN MILLIMETERS 0.05 5/8" 70 44.0 9.7 32.6 HAB-1,1 HAB-3,2.5 HAB-5,0.75 2019-151-21PROJECT NO.: HWAGRSZ 2019-151-21.GPJ 3/25/20 FIGURE: PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTON BH-1,S-3 5.0 6.5 13.6 SM Olive-brown, silty SAND with gravel BH-1,S-5 10.0 11.5 11.2 SM Olive-brown, silty SAND with gravel BH-1,S-6 15.0 16.5 9.9 32.2 48.7 19.1 SM Light olive-brown, silty SAND with gravel BH-2,S-1 2.5 4.0 11.4 25.0 44.9 30.1 SM Olive-brown, silty SAND with gravel BH-2,S-4 10.0 11.5 10.3 SM Light olive-brown, silty SAND with gravel BH-3,S-2 5.0 6.5 11.2 SM Light olive-brown, silty SAND with gravel BH-3,S-4 10.0 11.5 13.9 SM Light olive-brown, silty SAND with gravel BH-4,S-1 2.5 4.0 6.0 35.2 55.2 9.7 SP-SM Olive-brown, poorly graded SAND with silt and gravel BH-4,S-2 5.0 6.5 18.3 SM Olive-brown, silty SAND with gravel BH-4,S-4 10.0 11.5 24.8 28 16 12 11.8 44.6 43.6 SC Light olive-brown, clayey SAND BH-4,S-5 15.0 16.5 36.0 CL Dark grayish-brown, lean CLAY BH-5,S-2 5.0 6.5 7.7 34.5 55.9 9.5 SW-SM Olive-brown, well-graded SAND with silt and gravel BH-5,S-4 10.0 11.5 7.2 SM Olive-brown, silty SAND with gravel BH-5,S-5 15.0 16.5 7.1 SM Olive-brown, silty SAND with gravel(feet)TOP DEPTHSAMPLE DESCRIPTION Notes:ASTM SOILMOISTURECONTENT (%)ORGANIC% FINESSPECIFIC GRAVITYEXPLORATIONDESIGNATION1. This table summarizes information presented elsewhere in the report and should be used in conjunction with the report test, other graphs and tables, and the exploration logs. 2. The soil classifications in this table are based on ASTM D2487 and D2488 as applicable. MATERIAL PROPERTIES B-3 PAGE: 1 of 1 SUMMARY OF LIMITS (%) ATTERBERG BOTTOM DEPTHCONTENT (%)% SAND% GRAVELPIPLLL CLASSIFICATION(feet)2019-151-21PROJECT NO.: INDEX MATSUM 2 2019-151-21.GPJ 4/14/20 FIGURE: PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-6 S-1 S-1 15.0 - 16.5 2.5 - 4.0 2.5 - 4.0 #10 48.7 44.9 55.2 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-4 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 32.2 25.0 35.2 Sand % (SM) Light olive-brown, silty SAND with gravel (SM) Olive-brown, silty SAND with gravel (SP-SM) Olive-brown, poorly graded SAND with silt and gravel Fines % 0.00050.005 CLAY BH-1 BH-2 BH-4 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 10 11 6 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 19.1 30.1 9.7 2019-151-21PROJECT NO.: HWAGRSZ 2019-151-21.GPJ 4/14/20 FIGURE: PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-4 S-2 10.0 - 11.5 5.0 - 6.5 28 #10 44.6 55.9 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-5 12 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 11.8 34.5 Sand % (SC) Light olive-brown, clayey SAND (SW-SM) Olive-brown, well-graded SAND with silt and gravel Fines % 0.00050.005 CLAY BH-4 BH-5 16 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 25 8 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 43.6 9.5 2019-151-21PROJECT NO.: HWAGRSZ 2019-151-21.GPJ 4/14/20 FIGURE: PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTON 0 10 20 30 40 50 60 0 20 40 60 80 100 % MC LL CL-ML MH SAMPLEPLASTICITY INDEX (PI)SYMBOL PL PI S-4 10.0 - 11.5 1625 LIQUID LIMIT, PLASTIC LIMIT AND PLASTICITY INDEX OF SOILS METHOD ASTM D4318 43.6 CL (SC) Light olive-brown, clayey SAND CLASSIFICATION % Fines LIQUID LIMIT (LL) BH-4 ML 28 DEPTH (ft) 12 CH B-62019-151-21PROJECT NO.: HWAATTB 2019-151-21.GPJ 4/14/20 FIGURE: PACIFIC HIGHWAY NON-MOTORIZED CORRIDOR 16TH AVE S (S 308TH ST TO S 288TH ST) FEDERAL WAY, WASHINGTON 1 Sean C. Battle From:Michael Place <MPlace@hwageo.com> Sent:Tuesday, January 19, 2021 2:08 PM To:Bruce Erickson; Sean C. Battle Cc:Jolyn Gillie; Vasiliy Babko Subject:RE: Pacific Highway Non-Motorized Corridor, Final Geotechnical Report Bruce, Per our phone conversation the lateral pressures in the 8 and 9 are ultimate and do not include factors of safety. Allowable foundation bearing pressures in the report are based on predicted settlement but if you need to assume the factor of safety on them you can assume a factor of safety of 3.0. For the internal friction coefficient you may assume 0.5 and for active pressures behind walls 40 pcf may be used. Let me know if you have any more questions. Regards, Michael Place, P.E. Senior Geotechnical Engineer 21312 30th Drive SE, Suite 110 Bothell, WA 98021 Office: 425.774.0106 ext. 239 Cell: 425.977.5063 www.hwageo.com ELECTRONIC FILE TRANSFER Note that these electronic files (and those throughout the email thread) are provided as a courtesy only. HWA GeoSciences Inc. (HWA) in no way guarantees the accuracy or completeness of the digital data contained within these files. Furthermore, HWA assumes no liability for any errors or omissions in the digital data herein. Anyone using the information contained herein should always consult the hard copy drawings or reports for the most current information available. The use of this electronic information is restricted to the original site and project for which it was prepared. NOTICE OF CONFIDENTIALITY This email thread (including any attachments) contains confidential information intended for a specific purpose, and is protected by law. If you are not the intended recipient, you should delete this message and any disclosure. Copying or distribution of this message or the taking of any action based upon said email is prohibited. From: Bruce Erickson <Bruce.Erickson@kpff.com> Sent: Tuesday, January 19, 2021 12:26 PM To: Michael Place <MPlace@hwageo.com>; Sean C. Battle <Sean.Battle@kpff.com> Cc: Jolyn Gillie <jgillie@hwageo.com>; Vasiliy Babko <vbabko@hwageo.com> Subject: RE: Pacific Highway Non-Motorized Corridor, Final Geotechnical Report Michael, I’m finally responding to your final geotechnical report for Pacific Highway. For the most part it seems to have what we will need, but I do have a couple questions: · Where pressures are described as being “allowable”, such as the allowable bearing pressure for walls described on Page 11, does that mean it includes a factor of safety? Or, is it a nominal bearing strength to which a resistance factor should be applied per AASHTO for use in LRFD design? 2 · For the cast-in-place concrete retaining wall/vehicle barrier we intend to use toward the north end of the site, what active pressure and interface friction coefficient should we use to determine required proportions for sliding stability? Thanks. Bruce Erickson, PE, SE, ENV SP Associate O 206.622.5822 D 206.926.0546 bruce.erickson@kpff.com From: Michael Place <MPlace@hwageo.com> Sent: Tuesday, January 12, 2021 12:24 PM To: Sean C. Battle <Sean.Battle@kpff.com> Cc: Bruce Erickson <Bruce.Erickson@kpff.com>; Jolyn Gillie <jgillie@hwageo.com>; Vasiliy Babko <vbabko@hwageo.com> Subject: Pacific Highway Non-Motorized Corridor, Final Geotechnical Report Sean, Please find the attached final report for the Pacific Highway Non-Motorized Corridor project in Federal Way. Please let me know if you have any questions or if you need anything else. Regards, Michael Place, P.E. Senior Geotechnical Engineer 21312 30th Drive SE, Suite 110 Bothell, WA 98021 Office: 425.774.0106 ext. 239 Cell: 425.977.5063 www.hwageo.com ELECTRONIC FILE TRANSFER Note that these electronic files (and those throughout the email thread) are provided as a courtesy only. HWA GeoSciences Inc. (HWA) in no way guarantees the accuracy or completeness of the digital data contained within these files. Furthermore, HWA assumes no liability for any errors or omissions in the digital data herein. Anyone using the information contained herein should always consult the hard copy drawings or reports for the most current information available. The use of this electronic information is restricted to the original site and project for which it was prepared. NOTICE OF CONFIDENTIALITY This email thread (including any attachments) contains confidential information intended for a specific purpose, and is protected by law. If you are not the intended recipient, you should delete this message and any disclosure. Copying or distribution of this message or the taking of any action based upon said email is prohibited.