Attachment 4 - 2021-12-22 McChord Geotech Bridge Foundation Report.pdf

Geotechnical Bridge Foundation Report McChord Field Bridges/Design J84004and J84018 at JBLM, WA

Contract W912DW-18-D-1011 Task Order W912DW19F2166 Design Pkg. No. CE0668

December 22, 2021

Geotechnical Bridge Foundation Report McChord Field Bridges/Design J84004and J84018 at JBLM, WA

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Mark Stanley, P.E., G.E., DGE (CA 49746)

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Contents

1 Introduction

1.1 Project Description

1.2 Scope of Services

2 Data Review and Field Exploration

2.1 Review of Existing Data

2.2 Project Subsurface Explorations

2.2.1 Exploration Preparation

2.2.2 Explorations

2.3 Pilot Infiltration Test

2.4 Laboratory Testing

3 Geologic Setting

3.1 Regional Geology

3.2 Regional Seismicity

4 Site Conditions

4.1 Site Condition

4.1.1 Barnes Boulevard Crossing

4.1.2 Perimeter Road Crossing

4.1.3 Planned Utility/Pedestrian Bridge

4.2 Site Geology

4.3 Subsurface Conditions

4.4 Groundwater

4.5 Infiltration Rate

4.6 Corrosion Testing

5 Conclusions

5.1 Seismicity and Geologic Hazards

5.1.1 Seismicity

5.1.2 Soil Liquefaction

5.1.3 Dynamic Densification

5.1.4 Other Geological Hazards

5.2 Foundation Support

5.2.1 Vehicle Bridges

5.2.2 Utility Bridge

5.3 Pavement Design Considerations

5.4 Estimated Settlement Behavior – Barnes Boulevard Site

6 Foundation Recommendations

6.1 Pile Foundation Recommendations

6.1.1 Lateral Resistance

6.1.2 Driven CFST Pile Axial Resistance

6.1.3 Lateral Earth Pressures

6.2 Shallow Foundations

6.2.1 Allowable Bearing Pressure

6.2.2 Passive Resistance

6.2.3 Retaining Wall Global Stability

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6.3 Pole Foundations

6.4 Construction Considerations

6.4.1 Earthwork

6.4.2 Temporary Excavations

6.4.3 CFST Pile Driving Considerations

6.4.4 Pavement Construction Considerations

6.4.5 Realignment of Buried Utilities – Barnes Boulevard Site

7 Limitations

8 References and Referenced Documents

Tables

Table 1 Summary of 2015 Explorations Table 2 Summary of 2019 Explorations Table 3 Active Fault Locations Table 4 Seismic Design Parameters Table 5. Soil Parameters for Lateral Pile Resistance - Perimeter Road Table 6. Soil Parameters for Lateral Pile Resistance - Perimeter Road Table 7. Summary of Lateral Pile Analysis – Barnes Boulevard 36-inch Diameter CFST Fixed

Condition Table 8. Summary of Lateral Pile Analysis – Perimeter Road, 36-inch Diameter CFST Fixed

Condition Table 9. Barnes Boulevard, APILE Soil Parameters for Axial Pile Resistance Table 10. Perimeter Road, APILE Soil Parameters for Axial Pile Resistance Table 11. Summary of Wall Pressures

Figures

Figure 1. Vicinity Map Figure 2. Borehole Location Map Figure 3. HDR Exploration Plan Barnes Boulevard Bridge Replacement J84004 Figure 4. Barnes Boulevard Geologic Profile A-A’ Barnes Boulevard Bridge Replacement J84004 Figure 5. HDR Exploration Plan Perimeter Road Bridge Replacement J84018 Figure 6. Perimeter Road Geologic Profile B-B’ Perimeter Road Bridge Replacement J84018 Figure 7. Barnes Boulevard Driven 36-inch Diameter CFST-Pile Factored Axial Resistance

(Compression) Figure 8. Perimeter Drive Driven 36-inch Diameter CFST-Pile Factored Axial Resistance

(Compression)

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Appendices

Appendix A. Figures

Appendix B. USACE Geotechnical Investigations Data

Appendix C. HDR Boring Logs

Appendix D. Laboratory Testing

Appendix E. Seismic Parameter Development

Appendix F. LPILE Analysis Results

Appendix G. Pilot Infiltration Test Results

Appendix H. Wall Footing Computations iv | December 22, 2021

Acronyms

1 American Association of Highway and Transportation Officials ASTM American Society for Testing and Materials AT Level 1 Antiterrorism Level 1 bgs below ground surface CBR California Bearing Ratio CFST Concrete Filled Steel Tube CIDH Cast-in-Drilled-Hole deg degrees Fa Seismic Site Coefficient for short period range Fpga Seismic Site Coefficient for peak ground acceleration Fv Seismic Site Coefficient for peak long period range FHWA Federal Highway Administration ft feet GPS Global Positioning System H:V Horizontal:Vertical JBLM Joint Base Lewis-McChord Krazan Krazan & Associates, Inc.

LFRD Load Resistance Factor Design mg/kg Units of concentration in milligrams per kilogram MLC Military load classifications mph miles per hour Mw magnitude NAVD88 North American Vertical Datum of 1988 ohm-cm Unit of electric resistivity OPSEC Operation Security OSHA Occupational Safety and Health Administration pcf pounds per cubic foot PGA peak ground acceleration PIT Pilot infiltration test PSE Puget Sound Energy psf pounds per square foot psi per square inch SDS Seismic short period coefficient SD1 Seismic long period coefficient Sl Mapped Spectral Acceleration Coefficient at Period 1.0 seconds SPT Standard penetration Test Ss Mapped Spectral Acceleration Coefficient at Period 0.2 seconds SWMMWW Stormwater Management Manual for Western Washington USACE U.S. Army Corps of Engineers WSDE Washington State Department of Ecology WSDOT Washington State Department of Transportation

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1 Introduction This report presents the geotechnical investigation results and provides geotechnical recommendations to support the design of the Barnes Boulevard and Perimeter Road Bridge Replacement Project located at Joint Base Lewis-McChord (JBLM), southeast of Lakewood, Washington. The geotechnical investigations were performed and this report prepared in general conformance with the Washington State Department of Transportation (WSDOT) requirements for bridge design. This report was first published in February 2020 and has been updated to provide recommendations for the design of bridge approach fill retaining structures, recommendations for driven pipe pile option, and update pavement design recommendations.

1.1 Project Description

The U.S. Army Corps of Engineers (USACE) Seattle District contracted with HDR to perform engineering services at JBLM including design for replacement of two earthen embankments penetrated by corrugated metal arch culverts (culvert bridges) that cross Clover Creek (Figure 1; all figures located in Appendix A), and construction of a utility/pedestrian bridge west of Barnes Boulevard. JBLM is bounded by Interstate 5 on the west, 112th St E to the north, and Perimeter Road to the east and south. Clover Creek crosses the base in a general east-west direction. The culvert bridges at both locations are to be replaced with single span, cast-in-place reinforced concrete bridges.

The roadway grade will be raised to provide a minimum 3-foot freeboard above the 100-year creek flow and may require raising the road grade to 4.5 feet. Both replacement bridges will be constructed for a design speed of 35 miles per hour (mph). The bridges will be designed to accommodate military load classifications (MLC) for a HL-03/MLC 120 one-way or MLC 100 two-way (wheel or tracked), whichever is the most restrictive.

The bridges will be constructed in one stage and require closure of adjacent roadways during construction.

The three crossings are identified as the Barnes Boulevard crossing (JBLM ID J84004), the Perimeter Road crossing (JBLM ID J84018), and a planned utility/pedestrian bridge parallel with the Barnes Boulevard crossing. The project also includes a repair of the C Street Bridge (JBLM ID J84011) which does not include foundation modifications and is not addressed in this report. The pedestrian/utility bridge is to be designed by the selected contractor and currently anticipated to be supported by shallow foundations.

The Barnes Boulevard crossing is located on the west side of the base and incorporates three arch culverts immediately north of the intersection of Barnes Boulevard and Levitow Road (Figure 2). The replacement bridge will be approximately 61 feet long with new approach fills up to approximately 4-1/2 feet thick. The bridge will provide three, 12-foot lanes, 3-foot shoulders, a curb, and 5-foot sidewalk for each outside lane. During bridge construction, affected surrounding utilities will need to be relocated and minor retaining structures may be required to support approach fills. Utilities that may need relocating include two gas lines, communications conduit, and stormwater outfalls.

During construction of the bridge, overhead and underground electrical and steam systems may be temporarily interrupted. The roadway sections adjacent to the bridge must maintain the existing lane configuration on Barnes Boulevard.

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Perimeter Road crossing (J84018) incorporates two corrugated metal arch culverts (Figure 3). Perimeter Road is a security road that circles JBLM and crosses Clover Creek west of the terminus of 130th Street Court South. The replacement bridge will be approximately 61 feet long and accommodate two, 10.5-foot lanes and two, 5-foot shoulders. The roadway section adjacent to the culvert overpass will maintain the existing roadway prism. Vehicle access gates will be removed and re-installed unless future projects require gate adjustments. No utility relocation impacts are assumed for the Perimeter Road site.

The new utility bridge will be a will carry relocated base telecommunications, telephone and fiber optic lines, high pressure gas supply line, intermediate gas main, and local electrical power for street lighting. The utility bridge will include a 3-foot wide walk walkway for maintenance access.

1.2 Scope of Services

This report has been prepared in accordance with Task Order F2067, dated October 18, 2017 and included:

• A site visit to observe existing surface conditions in the general site areas

• Compiling and reviewing available existing geotechnical data for the project areas

• Preparing for and undertaking a subsurface exploration and laboratory testing program to supplement existing geotechnical data

• Summary of geologic and geotechnical conditions based on existing data

• Discussion of appropriate foundation types, including advantages and disadvantages of each

• Preliminary recommendations for foundation types (bridges and light poles)

• Analysis of expected settlement behavior

• Construction considerations for the selected pile type for support of the planned bridges

• Preparing report to present the data review results, discussion of geotechnical considerations, and preliminary foundation recommendations

2 Data Review and Field Exploration

2.1 Review of Existing Data

USACE provided HDR with geotechnical data obtained from the site vicinity including handwritten boring logs and results of geotechnical laboratory particle size analysis testing for four boings advanced as part of the USACE Seattle District McChord Bridge Repairs 65 percent Design Submittal (USACE 2015). The exploration program is summarized in Table 1 and the locations of the exploratory borings are shown on Figure 2. The boring logs are provided in Appendix B.

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Table 1 Summary of 2015 Explorations Boring ID Depth (foot) Location Exploration Type

BH-14-04-01 75 Barnes Boulevard culvert, south abutment Hollow Stem Auger

BH-14-04-02 75 Barnes Boulevard culvert, north abutment Hollow Stem Auger

BH-14-18-1 70 Perimeter Road culvert, northwest abutment

Hollow Stem Auger

BH-14-18-2 70 Perimeter Road culvert, southeast abutment

Hollow Stem Auger

USACE also provided as-built design drawings for the Levitow Bridge, which crosses Clover Creek approximately 270 feet east of Barnes Boulevard (Figure 1). Exploration boring logs are included in the as-built drawings and consist of three test pits/power augers excavated to a depth of approximately 9 feet and one test pit through which a hollow stem auger boring was advanced to a depth of 28.5 feet. Samples were obtained by driving a 3-inch sampler 12 inches with a 300-pound drop hammer. The approximate locations of the 1997 explorations are shown on Figure 2.

2.2 Project Subsurface Explorations

2.2.1 Exploration Preparation

HDR developed exploration and health and safety work plans prior to mobilizing to the project site. The exploration work plan included the location, depth of explorations, and drilling method type.

As required by the JBLM Public Works Department, a dig permit was obtained for all proposed explorations. Additionally, as required by JBLM, security clearance approvals and access badges were obtained from the base. In addition to security clearance approvals, all HDR and subcontractor personnel were required to complete online Operation Security (OPSEC) Awareness and Antiterrorism Level 1 (AT Level 1) trainings.

Training certifications were submitted prior to performing work at JBLM.

2.2.2 Explorations

A total of four sonic drill borings, one located on each side of the two proposed road crossings, were advanced to a depth of approximately 125 feet, observed, and logged.

Samples were collected at selected intervals for laboratory testing to confirm field classifications.

The boring locations, shown on Figure 3 and Figure 5, were determined using a handheld global positioning system (GPS) device. The sonic drill boring logs are included in Appendix C with details of the exploration program provided below.

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Table 2 Summary of 2019 Explorations Boring ID Depth (foot) Location Exploration Type

SB-01 125 Barnes Boulevard culvert, south abutment Sonic

SB-02 120 Barnes Boulevard culvert, north abutment Sonic

SB-03 125 Perimeter Road culvert, northwest abutment Sonic

SB-04 125 Perimeter Road culvert, southeast abutment Sonic

Drilling Method The sonic drill borings were performed by Gregory Drilling of North Bend, Washington.

The borings were advanced using a track-mounted Terrasonic 150 Compact Crawler drill rig using a sonic drilling method that advances a core barrel attached to the sonic drill head.

Sonic is an advanced form of drilling that employs the use of high-frequency, resonant energy generated inside the sonic head to advance a core barrel or casing into subsurface formations. During drilling, the resonant energy is transferred down the drill string to the bit face at various sonic frequencies. Simultaneously rotating the drill string evenly distributes the energy and impact at the bit face. The core barrel is advanced first followed by the outer casing. The outer casing supports the bore hole as the core barrel is retrieved. Sonic drilling is suited to difficult drilling conditions such as at JBLM where the underlying dense glacial till makes drilling and recovery difficult for traditional drilling methods.

Sampling The subsurface soils were continuously sampled in the sonic core. Drive samples were taken in the borings at 5-foot intervals to a depth of 20 feet and then at 10-foot intervals thereafter. The sampling interval was adjusted as necessary in the field based on the material encountered during drilling. The soil sampler used to obtained subsurface soil samples was a 1.375-inch inside diameter Standard Penetration Test (SPT) split barrel sampler without liners in general accordance with American Society for Testing and Materials (ASTM) D1586.

The SPT sampler was driven into the subsurface material using an automatic trip 140-pound hammer with a 30-inch free fall in general accordance with ASTM D1586.

After the sampler was driven, it was removed from the borehole and the exploration was advanced to the next sample interval.

The sonic core barrel was advanced through and below the sampled interval and retrieved samples were logged. Disturbed soils samples also were obtained from intermediate depths between push samples from core bags extruded from the core barrel.

Although the sonic drill method is more suited to difficult drilling conditions, drive sampling proved difficult due to the variable sand and gravel content of the subsurface formation. Groundwater heave (loosening of the soils as water rises in the open borehole) frequently occurred after extraction of the core barrel. Heaved material was

December 22, 2021 | 5 sampled with the SPT sampler with zero or low driving resistance and poor recovery.

Advancing the core through the sample zones allowed retrieval and visual logging of the disturbed soil in the sampled zone.

2.3 Pilot Infiltration Test

In accordance with State of Washington Stormwater Center requirements a small scale pilot infiltration test (PIT) was conducted southwest of the Barnes Boulevard culvert crossing in accordance with the guidance provided by Washington State Department of Ecology (WSDE) Stormwater Management Manual for Western Washington (SWMMWW; WSDE 2014). The PIT consisted of a falling head test performed in an excavated test pit 3 feet by 4 feet by 3 feet deep. After the test pit was excavated, the bottom 12 inches was filled with water and left to stand for a period of 6 hours in accordance with WSDE requirements. After the prescribed saturation period, the rate of drop in the water surface was measured using a data logger and pressure transducer.

After completion of the falling head test, the test pit was over-excavated to a depth of 4 feet to determine if the test water was mounded on a shallow restrictive layer or if it had continued to flow deeper into the subsurface. PIT test results are discussed in Section 4.

2.4 Laboratory Testing

Selected soil samples obtained from Borings SB-01 through SB-04 were delivered to Krazan & Associates, Inc. (Krazan) in Tacoma, Washington for geotechnical laboratory testing. Krazan is a USACE-certified geotechnical laboratory. Additionally, a few select samples obtained were delivered to the HDR Southern California Soils Laboratory in Claremont, California for corrosion testing. Testing was performed on select samples retrieved from the borings to assist in soil classification and determine strength parameters and index values. Field soil descriptions were compared to the laboratory test results and the description updated per laboratory test results in accordance with ASTM D2487. Boring logs and laboratory test reports are provided in Appendix C and Appendix D, respectively.

The following laboratory testing was performed on boring samples collected:

• Sieve analysis (ASTM D136 and C117)

• Hydrometer analysis (ASTM D422 and C117)

• Atterberg limits (ASTM D4318)

• Organic content (ASTM 2974)

• Moisture content and density (ASTM D7263b)

• Corrosion testing o Saturated Electrical Resistivity (ASTM G-187) o pH (ASTM G-51) o Chemical analysis for major anions and cations (ASTM 6919, ASTM 4327 and

AWWA 4110B)

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The laboratory test results are presented on the boring logs at the appropriate sample depths.

3 Geologic Setting

3.1 Regional Geology

The project site is located in the Puget Sound region south of the City of Tacoma in the Puget Lowland geomorphic province of Washington. The Puget Lowland is an elongated structural and topographic basin located between the Cascade Range and Olympic Mountains on the eastern and western boundaries, respectively. The regional landscape was formed by glacial scouring and deposition and tectonic folding and faulting.

Geologic formations in the Puget Lowland range in age from Eocene to recent Holocene.

The surficial geology of the region is primarily comprised of quaternary glacial deposit, characterized by a variable loose to compact sand and pebble to cobble gravel. These glacial deposits are more than 1,800 feet thick in the southern section of the Puget Lowland. Bedrock underlying the region ranges in age from Eocene to Miocene and consists of marine-deposited sedimentary and volcanic rocks.

The geologic conditions at the site vicinity have been documented in a report by Noble (1990) based on his review of regional water wells. At this site, glacial units consist of Vashon Drift underlain in turn by the Discovery nonglacial unit and the Narrows Glacial Unit. Other glacial units occur at greater depths down to Elevation -362 feet. The Vashon Draft occurred 20,000 to 13,000 before present (Blunt 1987). The Discovery nonglacial unit has a suggested age of 28,000 to 20,000 before present. The base of the unit range from Elevation 100 to 200 feet in western Peirce County. The Narrows glacial unit in a drift unit below the Discovery nonglacial unit. Noble estimated the base of the Vashon drift at Elevation 201 feet, Discovery nonglacial unit at Elevation 181 feet underlain by the Narrows glacial unit at Elevation 130 feet. Elevations are in North American Vertical Datum of 1988 (NAVD88).

3.2 Regional Seismicity

Active faults that extend through the Puget Lowland have produced three, large (magnitude [Mw] 6.0 or greater) earthquakes within the last 50 years that have damaged infrastructure. The most recent seismic event being the Nisqually Earthquake (Mw 6.8) in 2001. The faults producing these earthquakes are part of a system of crustal faults east of the Cascadia Subduction zone. Local faults within this area include the Tacoma and Seattle faults. The major fault in this system is the Seattle fault which extends for at least 40 miles within central Puget Sound.

Table 3 summarizes the approximate distances between the site and the three closest mapped active faults based on the 2014 update to the United States National Seismic Hazard Maps online Fault Parameter database (U.S. Geological Survey 2014).

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Table 3 Active Fault Locations

Fault (segments)

Approximate Distance from Site (miles)

Direction from Site

Maximum Moment

Magnitude

Tacoma Fault Zone 16.2 North 6.9

Seattle Fault Zone-middle 30.0 North 7.2

Southern Whidbey Island Fault-middle 45.2 North 7.4

Earthquakes on these or other active faults (including unmapped faults) could cause strong ground shaking at the site. Earthquake intensities vary throughout the Puget Lowland depending on the magnitude of the earthquake, the distance of the site from the causative fault, the type of materials underlying the site, and other factors.

4 Site Conditions

4.1 Site Condition

The project site is located in the northern area of JBLM along the western and eastern boundary of the McChord airfield. Clover Creek is a perennial stream that flows westerly through JBLM and empties into Lake Steilacoom. Clover Creek currently follows a southwesterly and westerly alignment as it passes across the JBLM site. Review of historical topographic maps indicates Clover Creek has been at its present alignment since the mid-1940s. Clover Creek is a graded trapezoidal channel with a top width ranging from 60 to 75 feet and depth of approximately 11 feet.

The creek has not always been located along its present alignment. Review of available historic U.S. Geological Survey Tacoma South topographic quadrangles shows that:

• The site has been in its current configuration since the early 1960s when the present runway and appurtenant facilities were developed. The original airfield was located along the western portion of the site north of Barnes Boulevard. The runway development included placing Clover Creek into a culvert under the runway following the pre-development alignment.

• Between 1945 and the early 1960s prior to development of the runway the site remained relatively unchanged and Clover Creek was located in its present alignment.

• Comparison of available topographic maps from 1900 and 1945 show that Clover Creek followed a more northern alignment prior to 1945 and connected to Smith Lake, which limits were mapped as seasonal. It appears that at some period between 1900 and 1945, Clover Creek was realigned southward, Smith Lake was drained, and the western limit reclaimed (filled). An estimate of the original creek channel location is shown in Figure 1.

• Barnes Boulevard has been the primary creek crossing since before 1900 and at or near its original alignment. The alignment was shifted southeast of the Barnes

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Boulevard crossing. The Perimeter Road crossing appears to have been located within the limits of Smith Lake.

4.1.1 Barnes Boulevard Crossing

The existing Barnes Boulevard crossing is located along the western boundary of the airfield. The culvert is a corrugated, steel-plate, arch-pipe creek crossing where each of the three pipes has a 13-foot span and 8–foot rise. The culvert lengths are approximately 80 feet each. Recent inspections found the metal pipes are heavily corroded and easily punctured with a chipping hammer. A concrete sidewalk is located on the west section of the crossing. The Barnes Boulevard crossing is north of a signalized roadway intersection with periods of high traffic volume.

There are buried and overhead utilities including communication cables, gas lines, and overhead electric lines. Buried utilities consist of:

• JBLM telecommunications lines

• CenturyLink (now Lumen) telephone and fiber optic lines

• A Puget Sound Energy (PSE) 8-inch-diameter high pressure gas supply line

• A PSE 2-inch-diameter intermediate gas main

• A high-pressure steam line and condensate return line

• Local electrical power for street lighting

Primary overhead electric lines run along the western boundary of the crossing. A main stormwater pipe parallels Barnes Boulevard south of the crossing and discharges into Clover Creek through a stormwater outfall structure.

4.1.2 Perimeter Road Crossing

The existing Perimeter Road crossing is located along the eastern boundary of the airfield near 130th Street Court South. The embankment crossing is penetrated by three corrugated metal arch culverts. Recent inspection determined that the culvert pipes have reached their service life and are heavily corroded. The crossing is gated with restricted vehicle access. A perimeter security fence is located east of the crossing. There are no utilities within the crossing. Additionally, there is a steel grate on the upstream culvert opening that blocks access to the airfield from Clover Creek.

4.1.3 Planned Utility/Pedestrian Bridge

The utility/pedestrian bridge will be located west of the existing Barnes Boulevard crossing along the western boundary of the airfield. The bridge design will be consistent with the Barnes Boulevard crossing related to freeboard and ability to span the ordinary high-water elevation. The bridge will carry the buried utilities listed above. The structure will include a walkway for maintenance and pedestrian access.

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4.2 Site Geology

The northern section of JBLM is made up of glacial recessional outwash (Qgo). JBLM is located on a glacial drift plain overlain by Steilacoom gravel (Qgosg), which is comprised of pebbles with boulders (Schuster et al. 2015). The glacial deposits at the project site are described by Schuster et al. (2015) as Pleistocene-age.

Buchanan-Banks and Collins (1994) mapped depth to bedrock at least 1,800 feet below the airfield. The underlying bedrock is comprised of sedimentary deposits described as Tertiary-age based on existing bedrock outcrops within the Puget Lowland.

4.3 Subsurface Conditions

Consistent with the available geologic information, the past subsurface explorations primarily encountered glacial till that was relatively consistent across the JBLM project site. In general; the subsurface stratigraphy at both sites consisted of alternating layers of gravels and fine to coarse grained sands. The distinct change in maximum grain sizes between these layers typically coincides with periods of high and low drainage flows.

Coarse grained material angularity and shape were observed as generally subangular to subrounded and elongated. The explorations were advanced from current crossing grade. Soils encountered in the borings generally consisted of an overlying layer of topsoil, with thicknesses ranging between 1 and 2 feet. Underlying the surficial topsoil, explorations encountered medium dense to very dense coarse grained materials (sand and gravel) with a trace of cobbles to a depth of 125 feet, the total depth explored.

Cobbles were encountered in trace amounts through the entire exploration depth and typically ranged between 3.5 and 5 inches in greatest dimension. There are some isolated occurrences of cobbles between 6 and 7 inches at concentrations between 5 and 15 percent. The granular layers typically contained between 5 and 10 percent clayey fines. With the exception of exploration SB-03 at the Perimeter Road crossing, layers of relatively clean gravels were encountered at a depth of about 60 feet. The interpreted subsurface profiles for the Barnes Boulevard and Perimeter Road are provided as reference (Figure 4 and Figure 6, respectively). The upper 30 feet of the coarse grained materials appear to be weathered glacial till that transition to a more competent till to a depth of 85 to 90 feet where the till transitions to glacial outwash. The approximate location of these transitions is shown on the log of borings presented in Appendix C. The borings may not have penetrated into the underlying Narrows glacial unit.

Clay layers were encountered at the Perimeter Road site between depth ranges of about 15 to 35 feet and again at 100 to 115 feet. The shallower clay layer generally consisted of medium stiff to stiff sandy clay to medium dense clayey sand and gravel. The deeper clay layers are comprised of hard sandy clay with medium to high plasticity. The shallow silt and clay layers were likely deposited within a predecessor to Smith Lake. An organic silt with sand layer with an organic content up to 37 percent was identified in the upper 4 feet of the Smith Lake deposits. The granular soils that overlie the shallow clay layers likely are fill that was placed to reclaim Smith Lake.

While drilling, the logger noted instances of no to low blow counts and no sample recovery. Upon review of borings, these instances are related to materials sampled below groundwater where sands heave (flow) into the open borehole. Indications of

10 | December 22, 2021 heaved sands also are believed to occur where a sudden decrease in resistance was noticed while driving the SPT sampler. An example of this would be a decrease in the number of blow counts to drive the last half foot interval of the SPT sampler. Heaved sands were classified as very wet and reported little to no recovery when sampled with the SPT sampler. Heaved sands obtained from core bags contained fine granular soils with little to no cobbles. The occurrence of heaving sands also was noted in the 2015 borings drilled by USACE. The occurrence of heaved sands is primarily located in the Discovery nonglacial unit, a water bearing unit with reduced fines that is more susceptible to base heave and borehole collapse. The relatively low SPT N-values in the heaving sands are not necessarily an indicator of the strength of the soil or its resistance to pile driving.

A hydrocarbon odor was noted in a 4-inch-thick layer in Boring SB-03 at a depth of about 13 feet which roughly corresponds to the zone of groundwater fluctuation. Review of historical explorations performed for the design of the Levitow Bridge in the mid-1990s (located southeast of the Barnes Boulevard crossing) also noted a petroleum odor at a similar depth (8 to 14 feet below ground surface) and an oil sheen within the test pit. The source of the petroleum is unknown and may be related to a past fuel discharge to groundwater. It should be noted that no other indication of contamination was noted by the drillers when advancing the boring. If soils with similar odors are encountered during construction additional sampling and testing may be warranted.

4.4 Groundwater

Groundwater levels were measured in the available historical borings and recent HDR sonic drill borings. Groundwater levels in the sonic borings were determined by examining the moisture conditions of soil samples obtained during drilling. Light rain occurred during the field investigation and there was no notable flow within the creek channel. Groundwater was estimated to occur between a depth of 20 and 25 feet below the ground surface (bgs) at Barnes Boulevard (between elevation 254 to 259 feet) and at a depth of 12 bgs at Perimeter Road (approximately elevation 279 feet). Although artesian conditions were not encountered, it is unknown if the Discovery nonglacial unit is under pressure which may have influenced the measured depth of groundwater.

Groundwater level fluctuations can occur from seasonal changes, variations in rainfall, flow within the river, and other factors. As such, groundwater levels at the time of field investigations may be different than those encountered during construction. Also the borings were not left open for sufficient time to allow groundwater levels to equilibrate.

During most of the year, groundwater likely would coincide with the water level in the creek. Groundwater levels could fluctuate locally in the vicinity of the creek as creek flows increased with a corresponding rise in water level. HDR has conducted a study of the channel hydraulics (HDR 2018) which includes stream flow elevations developed by Federal Emergency Management Agency. A storm event that has a 1 percent annual probability results in a water surface elevation of 287.1 feet immediately upstream of Barnes Boulevard and 285.9 feet upstream of Perimeter Road. A storm event that has a 10 percent annual probability results in a water surface elevation of 276.9 feet immediately upstream of Barnes Boulevard and 283.9 feet upstream of Perimeter Road.

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4.5 Infiltration Rate

Results of the small scale surficial soil PIT (0 to 3 feet bgs) at Barnes Boulevard are presented in Appendix G. The surficial soils underlying the PIT location was comprised of poorly-graded gravels with sand. Additionally, the gravels contained subrounded cobbles of up to 3.5 inches. The test pit drained rapidly and completely drained the minimum 12 inches of head in a period of 50 minutes. Over-excavation of the test pit indicated the test water was not mounded on a shallow impermeable layer and has continued to flow deeper into the subsurface. An infiltration rate of 13 inches per hour was calculated using the falling head test results presented in Appendix F.

4.6 Corrosion Testing

One soil sample from each bridge site was sent to HDR’s Claremont California corrosion testing laboratory. Sample SB-01-G4 taken at a depth of 18 feet from Boring SB-01 at the Barnes Boulevard site and Sample SB-03-G4 taken at a depth of 12 feet from Boring SB-03 at the Perimeter Road site. The test report is included at the end of Appendix D.

Sample SB-01-G4 was classified as a poorly graded gravel with sand with less than 10 percent fines. The testing found the sample had a saturated electrical conductivity of 20,000 ohm-cm and pH of 7.1. Chloride and sulfate anions were found at a concentration of 1.3 and 56 mg/kg, respectively. Bicarbonate and fluoride anions were found at a concentration of 98 and 69 mg/kg, respectively. Sodium and calcium anions were found at a concentration of 32 and 35 mg/kg, respectively.

Sample SB-03-G4 was classified as an organic soil with sand. The testing found the sample had a saturated conductivity of 3,520 ohm-cm and a pH of 4.9. Chloride and sulfate anions were found at a concentration of not detected and 594 mg/kg, respectively. Bicarbonate and fluoride anions were found at a concentration of 52 and 38 mg/kg, respectively. Sodium and calcium anions were found at a concentration of 29 and 66 mg/kg, respectively.

Two soils samples were tested for pH by Krazan. Sample SB-01-S1 (Borings SB-01 at the Barnes Boulevard site) at a depth of 6 feet had a pH of 4.8 and organic content of

12.9 percent. Sample SB-03-G2 (Borings SB-03 at the Perimeter Road site) at a depth of 8 feet had a pH of 6.1 and organic content of 17.1 percent.

Based on the pH test results being greater than 5.5, these sites would be classified as non-marine corrosive according to the most recent revision to WSDOT Bridge Design Manual Section 6.7 Corrosion of Steel Foundations and Buried Structures (WSDOT 2020a). The chloride and sulfate concentrations are below the classification threshold.

5 Conclusions The sites are geotechnically suitable for supporting the planned single span bridges.

Presented below are preliminary geotechnical considerations and conclusions for selection and design of foundation support for the proposed McChord Field Bridges Project with geotechnical recommendations provided in Section 6.

12 | December 22, 2021

5.1 Seismicity and Geologic Hazards

5.1.1 Seismicity

The site is located in a seismically active region of Washington. Significant earthquakes in the Puget Sound region have been associated with movements along well-defined fault zones. Earthquakes occurring along any of the surrounding faults have the potential to produce strong ground shaking at the site.

It is understood that the American Association of Highway and Transportation Officials (AASHTO) Load Resistance Factor Design (LFRD) Bridge Design Specifications 8th edition will be used for seismic design (2017). WSDOT’s Bridge Engineering Toolbox (BEToolbox) software was used to determine the seismic parameters for each bridge location (WSDOT 2019a). The software references the AASHTO LRFD Bridge Design Specifications to obtain the peak ground acceleration (PGA) and short (Ss) and long period (Sl) spectral acceleration coefficients for the bridge project sites. Seismic parameters were obtained for a 7 percent probability of exceedance in 75 years hazard level (equal to a return period of approximately 1,000 years). Subsurface explorations at both bridge locations describe the underlying soil as medium to very dense native soils.

As such, the overall soil profile was characterized as a Site Class C. The seismic design parameters selected for each bridge are summarized in Table 4. The utility bridge should be designed using the seismic parameters provided for the Barnes Boulevard site.

Table 4 Seismic Design Parameters

Seismic Parameter Barnes Boulevard Bridge

(J84004) Perimeter Road Bridge

(J84018)

PGA 0.407g 0.406g

Ss 0.920g 0.916g

S1 0.269g 0.268g

Site Class C C

Fpga 1.200 1.200

Fa 1.200 1.200

Fv 1.500 1.500

SDS 1.104g 1.100g

SD1 0.403g 0.402g

Seismic Design Category C C

Seismic parameter outputs from BEToolbox are provided in Appendix E.

5.1.2 Soil Liquefaction

Soil liquefaction is a phenomenon in which saturated (submerged), cohesionless soil experiences a temporary loss of strength due to buildup of excess pore water pressure during cyclic loading induced by an earthquake. The soils most susceptible to liquefaction are loose, clean, saturated, poorly (uniformly) graded sand, and non- to low-plasticity silt or silty sand. Denser soils are more resistant to seismic liquefaction than

December 22, 2021 | 13 looser soils. Soils with significant fines content are more resistant to seismic liquefaction than clean sands.

Soils encountered in the recent and historical explorations generally consist of granular materials with minor clay and sand content. The potential for soil liquefaction to occur at this site is low. Furthermore, the Washington Geological Survey maps the McChord airfield area to have a low potential of liquefaction (Palmer et al. 2004).

5.1.3 Dynamic Densification

During an earthquake, unsaturated granular soils (above the groundwater table) can experience dynamic densification due to reorientation and compaction of the soil particles. Soils generally susceptible to dynamic densification are relatively clean, loose to medium dense, cohesionless soils. Subsurface soils encountered in the recent and historical explorations do not appear to be susceptible to dynamic densification. Based on the subsurface conditions encountered at both culvert locations, the potential for seismically-induced settlement in soils above the groundwater table is considered low.

5.1.4 Other Geological Hazards

Hazards such as lurching, or fault rupture are considered unlikely at both culvert locations because of subsurface soil conditions and distance to known active faults.

5.2 Foundation Support

5.2.1 Vehicle Bridges

The proposed replacement bridges at both culvert locations are single span and supported on two abutments for each bridge. During the planning phase, the foundation support for both bridges was assumed to be deep foundations consisting of steel H-piles.

As an alternative, Cast-in-Drilled-Hole (CIDH) or Concrete Filled Steel Tube (CFST) piles were considered. CIDH terminology refers to drilled shaft construction methods and CFST terminology refers to driven pile construction methods, according to WSDOT standards. The current and past explorations found that the site is underlain by dense to very dense sandy gravel and gravelly sand with cobbles up to 5 inches on average with isolated layers containing cobbles up to 7 inches in largest dimension. Advancement of H-piles or pipe piles by driving will be difficult without incurring damage to the pile tip or top of pile due to hard driving conditions. Additionally, it is possible for boulders larger than 12 inches in diameter to be encountered within the anticipated length of the deep foundations based on the geologic characteristics of the glacial till, regardless of the observation that boulders were not encountered during the subsurface exploration.

Due to driving conditions and the relatively high groundwater condition, support of the bridge foundations H-piles were discounted from further evaluation.

The Levitow Road Bridge as-built drawings indicate the bridge foundations are supported by CFST piles although it is not known how the casing was advanced.

Initially, HDR evaluated the use of CFST pile installation through rotary or oscillator drilling methods. However, in 2020, WSDOT revised the bridge foundation design recommendations for reduction of the side friction resistance component to account for

14 | December 22, 2021 potential over drilling of the holes. Using the WSDOT-recommended side friction factor limitation for rotary or oscillator pile installation methods resulted in excessively deep piles. Driven CFST piles result in shorter piles as compared to CFST piles that are installed using rotary or oscillator installation methods but may require pre-drilling of holes slightly smaller than the steel pipe outer diameter to facilitate driving. Due to the granular formation, the drilled holes for driving CFST will require support using water-based slurry per WSDOT standards.

Preliminary estimates of the lateral and axial pile resistances for a 36-inch-diameter and 100-foot-long driven CFST pile are presented in Section 6.

5.2.2 Utility Bridge

Borings and subsurface conditions at the utility/pedestrian bridge were not performed or evaluated in detail. However, conditions are assumed to be similar to conditions at the Barnes Boulevard Bridge with medium dense to dense gravel with sand located in the top 10 feet of the surface. The material is suitable for the use of spread footings to support the proposed single span bridge.

5.3 Pavement Design Considerations

The bridge approaches may be raised as much as 4.5 feet to provide sufficient clearance between the stream and bridge deck. The potential borrow source of the approach fills has not been determined. Pavement design is conducted in accordance with the requirements of United Facilities Criteria 3-250-01, Pavement Design for Roads and Parking Areas (2016). Federal Highway Administration (FHWA) provides a range of California Bearing Ratio (CBR) values by soil classification in Geotechnical Aspects of Pavement Design (NHI-05-037). Typical range of CBR for clayey gravel ranges from 20 to 40 and for poorly graded gravel the range is from 35 to 60. CBR testing was performed as part of a 2013 investigation for the JBLM Access Corridor Bridge (Krazan 2013) on a sample of sand with gravel and produced a CBR of 25. A design CBR of 25 is reasonable for design and should be confirmed once the borrow source is identified for the approach fills.

5.4 Estimated Settlement Behavior – Barnes Boulevard

Site The planned increase in grade at the Barnes Boulevard site by placement of up to approximately 4-1/2 feet of fill will result in settlement of the existing near-surface soils. It is estimated up to 1 inch of settlement will occur where the fill is thickest and two thirds of this amount at the fill edges.

Most, if not all, of this settlement will be elastic in nature and occur during and immediately after fill placement. Of concern is the potential adverse effect the settlement may have on the existing buried gas and steam lines. These buried utilities should be considered sensitive to differential settlement during fill placement and at the edge of the planned fill adjacent to the abutments for the utility/pedestrian bridge. Recommendations to mitigate this potential are presented in Section 6.4.5 of this report.

December 22, 2021 | 15

6 Foundation Recommendations

6.1 Pile Foundation Recommendations

JBLM bridge design follows the recommended practices in the WSDOT Geotechnical Design Manual (WSDOT 2019b). Lateral and axial analysis for driven CFST piles has been conducted in accordance with WSDOT LRFD requirements and is presented in this section. A minimum 36-inch-diameter is recommended based on the presence of cobbles in the foundation materials that may preclude advancement of smaller diameter piles. Boring SB-03 was considered the most critical boring for the Perimeter Road bridge based on the thickness of the old Smith Lake clay deposits and was the basis for these analyses. The footing bottom was assumed to coincide with the channel bottom.

SB-01 was the deepest of the two boring advanced at Barnes Boulevard Bridge and was the basis for these analyses.

Subsurface soil strength properties were developed following correlations contained in the WSDOT geotechnical manuals and are summarized in the following sections.

6.1.1 Lateral Resistance

The lateral pile resistance and stiffness were calculated using the computer program LPILE Plus Version 6.0 (Ensoft 2018a) for single piles. Site stratigraphy and selected soil properties were input into the model to generate soil resistance curves (p-y curves).

Table 5 shows the soil input parameters used for the lateral pile analysis performed using LPILE for the 36-inch CFST piles.

The lateral pile analysis assumes an uncracked pile section and design concrete strength (f’c) of 4,000 pounds per square inch (psi) for pinned and fixed head conditions.

Lateral forces were calculated based on assigned top deflections of ¼-, ½-, and 1-inch.

Table 5. Soil Parameters for Lateral Pile Resistance - Perimeter Road

Layer Bottom Depth

(ft) Soil Type LPILE Soil

Model

Elevation

(NAVD88)

(ft)

Eff. Unit Weight

(pcf)

Internal Friction Angle (deg)

Cohesion (psf)

1 Poorly Graded Sand with Gravel

Sand (Reese)

270 62.6 30 -

3 Lean Clay with Sand Stiff clay w/o free water (Reese)

268 62.6 - 500

14 Well Graded Gravel with Sand

Sand (Reese)

257 62.6 30 -

18 Poorly Graded Sand with Gravel

Sand (Reese)

253 62.6 35 -

21 Poorly Graded Gravel

Sand (Reese)

250 62.6 40 -

16 | December 22, 2021

Layer Bottom Depth

(ft) Soil Type LPILE Soil

Model

Elevation

(NAVD88)

(ft)

Eff. Unit Weight

(pcf)

Internal Friction Angle (deg)

Cohesion (psf)

24 Fat Clay Stiff clay w/o free water (Reese)

247 62.6 - 1,000

36 Poorly Graded Sand with Gravel (high gravel content)

Sand (Reese)

235 62.6 40 -

54 Poorly Graded Sand with Gravel

(Very Dense)

Sand (Reese)

202 62.6 45 -

69 Poorly Graded Sand with Gravel

(Very Dense)

Sand (Reese)

202 62.6 45 -

74 Stiff clay w/o free water (Reese)

Stiff clay w/o free water (Reese)

197 62.6 - 1,000

86 Sand (Reese) Sand (Reese)

185 62.6 45

93 Stiff clay w/o free water (Reese)

Stiff clay w/o free water (Reese)

178 62.6 - 2,000

111 Sand (Reese) Sand (Reese)

160 62.6 45 ft=feet; pcf=pounds per cubic foot; deg=degree; psf=pounds per square foot 1 Contribution to lateral resistance neglected due to top of pile beginning at 12 foot below ground surface.

2 Groundwater depth is 12 foot below ground surface.

Table 6. Soil Parameters for Lateral Pile Resistance - Perimeter Road

Layer Bottom Depth

(ft) Soil Type LPILE Soil

Model

Elevation

(NAVD88)

(ft)

Eff. Unit Weight

(pcf)

Internal Friction Angle (deg)

Cohesion (psf)

1 Poorly Graded Sand with Gravel

Sand (Reese)

270 62.6 30 -

3 Lean Clay with Sand Stiff clay w/o free water (Reese)

268 62.6 - 500

14 Well Graded Gravel with Sand

Sand (Reese)

257 62.6 30 -

18 Poorly Graded Sand with Gravel

Sand (Reese)

253 62.6 35 -

21 Poorly Graded Gravel

Sand (Reese)

250 62.6 40 -

December 22, 2021 | 17

Layer Bottom Depth

(ft) Soil Type LPILE Soil

Model

Elevation

(NAVD88)

(ft)

Eff. Unit Weight

(pcf)

Internal Friction Angle (deg)

Cohesion (psf)

24 Fat Clay Stiff clay w/o free water (Reese)

247 62.6 - 1,000

36 Poorly Graded Sand with Gravel (high gravel content)

Sand (Reese)

227 62.6 40 -

69 Poorly Graded Sand with Gravel

(Very Dense)

Sand (Reese)

202 62.6 45 -

74 Stiff clay w/o free water (Reese)

Stiff clay w/o free water (Reese)

197 62.6 - 1,000

86 Sand (Reese) Sand (Reese)

185 62.6 45

93 Stiff clay w/o free water (Reese)

Stiff clay w/o free water (Reese)

178 62.6 - 2,000

111 Sand (Reese) Sand (Reese)

160 62.6 45 ft=feet; pcf=pounds per cubic foot; deg=degree; psf=pounds per square foot 1 Contribution to lateral resistance neglected due top of pile beginning at 12 foot below ground surface.

2 Groundwater depth is 12 foot below ground surface.

Plots of deflection, shear, and moment for both pinned and fixed pile head conditions for each pile type are provided in Appendix F and the results summarized in Table 7 and Table 8.

Pile spacing should be a minimum of 3 diameters to avoid group effects. Design of piles spaced closer than 3 pile diameters will need to take into account reduction in lateral resistance and stiffness per WSDOT foundation design standards through the use of p-multipliers.

The structural engineer also performed lateral pile stability analysis using Ensoft’s Group software, which utilizes the same p-y curves that are recommended herein for LPILE.

The minimum pile tip elevations to achieve lateral stability were determined by the structural engineer using Group and are reported on the bridge plans.

Table 7. Summary of Lateral Pile Analysis – Barnes Boulevard 36-inch Diameter CFST Fixed Condition

Deflection (inches) 0.25 0.5 1.0 Maximum Shear (Kips) 118 183 298

Maximum Moment, Kip-ft (Depth of Maximum Moment, ft)

-1,058 (0)

-1,817 (0)

-3,200 (0)

18 | December 22, 2021

Table 8. Summary of Lateral Pile Analysis – Perimeter Road, 36-inch Diameter CFST Fixed Condition

Deflection (inches) 0.25 0.5 1.0…