RFI_Att_3_-_Geotechnical_Design_and_Foundation_Report_Redacted.pdf

Air Combat Command Beale US Air Force Base 9th Civil Engineer Squadron Contract: FA468617C0003 Wheatland Gate Bridges Bridges #221 and #222

Submitted to:

Air Combat Command Beale US Air Force Base 9th Civil Engineer Squadron

May 2017

GEOTECHNICAL DESIGN

AND FOUNDATION REPORT

May 25, 2017

AIR COMBAT COMMAND

BEALE US AIR FORCE BASE

9TH CIVIL ENGINEER SQUADRON

CONTRACT: FA468617C0003 WHEATLAND GATE BRIDGES BRIDGES #221 AND #222

Submitted to:

Air Combat Command Beale US Air Force Base 9th Civil Engineer Squadron

TABLE OF CONTENTS

GEOTECHNICAL DESIGN AND FOUNDATION REPORT PAGE

EXECUTIVE SUMMARY

1.0 INTRODUCTION

2.0 SCOPE OF SERVICES

3.0 PROJECT DESCRIPTION

3.1 Background and Site Description

3.2 Existing Structures

3.3 Proposed Improvements and Structures

4.0 FIELD INVESTIGATION AND TESTING PROGRAM

5.0 LABORATORY TESTING PROGRAM

6.0 SITE GEOLOGY AND SUBSURFACE CONDITIONS

6.1 Topography

6.2 Regional Geology

6.3 Existing Roadway Pavement Sections

6.4 Soil Conditions

6.4.1 Embankment Fill

6.4.2 Alluvium

6.5 Groundwater

6.6 Geologic Hazards

6.6.1 Landslides

6.6.2 Embankment Failures

6.6.3 Ground Subsidence

6.6.4 Expansive Soils

6.6.5 Collapsible Soils

6.6.6 Fault Rupture

6.6.7 Liquefaction

6.6.8 Lateral Spreading

6.6.9 Unsaturated Seismic Settlement

6.6.10 Slope Stability

7.0 SCOUR EVALUATION

8.0 CORROSION SCREENING

9.0 SEISMIC RECOMMENDATIONS

10.0 AS-BUILT FOUNDATION DATA

11.0 FOUNDATION RECOMMENDATIONS

11.1 Deep Foundations

11.2 Special Considerations for Driven Piles

11.3 Pile Acceptance Criteria

11.4 Retaining Walls/Wingwalls

12.0 GRADING AND EARTHWORK RECOMMENDATIONS

12.1 General

12.2 Soil and Excavation Characteristics

12.3 Materials for Fill

12.4 Groundwater, Wet Soils

12.5 Grading

TABLE OF CONTENTS (Continued)

13.0 PAVEMENT RECOMMENDATIONS

14.0 CLOSURE

14.1 Foundation and Improvement Plan Review

14.2 Testing and Observation Services

14.3 Limitations and Uniformity of Conditions

15.0 REFERENCES

FIGURES

Figure 1, Vicinity Map Figure 2, Site Plan/Geologic Map Figure 3, Geologic Cross-Section A-A’ Figure 4, Geologic Cross-Section B-B’ Figures 5 and 6, Recommended Design Response Spectra

APPENDIX A

FIELD INVESTIGATION

Table A1, Summary of Borings Figure A1, Key to Logs Figures A2 through A11, Boring Logs (B1 through B4)

APPENDIX B

LABORATORY TESTING

Table B1, Soil Corrosion Test Summary Table B2, Summary of R-Value Test Results Table B3, Expansion Index Test Results Figure B1, Summary of Laboratory Results Figure B2, Atterberg Limits Figure B3, Grain Size Distribution Figure B4, Moisture-Density Relationship Figures B5 through B9, Unconfined Compressive Strength Figure B10, Triaxial Shear Strength – UU Test (Staged)

APPENDIX C

LOG OF TEST BORINGS

Log of Test Boring Sheets

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GEOTECHNICAL DESIGN AND FOUNDATION REPORT

EXECUTIVE SUMMARY

This report presents the results of our geotechnical investigation for the proposed Wheatland Gate Bridges Replacement design-build project located in the southern portion of Beale Air Force Base (AFB) east of Yuba City/Marysville in Yuba County, California. The project consists of replacing Bridge FAC #221 and Bridge FAC #222 with precast, prestressed, single-span concrete structures. In our opinion, no adverse geotechnical conditions are present that would preclude proposed improvements as planned, provided the recommendations of this report are incorporated into the design and construction of the project.

Subsurface conditions at the bridge locations (below the pavement structural section) generally consists of embankment fill over alluvium. Embankment fill extends from below the roadway pavement section to depths of between approximately 10 to 13 feet. Embankment fill primarily consists of loose to medium dense clayey gravel and clayey sand and medium stiff to stiff lean clay with varying sand and gravel. Underlying alluvium consists of interbedded clayey sand and lean clay with varying sand and gravel content to the maximum depth explored of approximately 61.5 feet. Upper alluvial soils (to depths of approximately 18 to 23 feet) are generally reddish brown and soft to stiff / very loose to medium dense. Below this depth the alluvium is generally very stiff to hard / dense to very dense.

Scour evaluations by others indicates total scour depths at the support locations of approximately seven feet from finished grade at Bridge FAC #221 and between approximately four and five feet at Bridge

FAC #222.

Based on our observations and analyses, the potential for landslides, embankment failures, ground subsidence, collapsible soils, fault rupture, liquefaction, lateral spreading, and seismic settlement to impact the proposed bridges are considered low. The tested soils exhibit low expansion potential.

Based on the laboratory test results, site soils are classified as non-corrosive according to Caltrans’ Corrosion Guidelines. Proposed improvements in contact with the ground should be designed and constructed in accordance with Caltrans’ Standard Specifications and good construction practices.

Based on the subsurface conditions encountered in our borings, the replacement bridges may be supported on driven steel HP 14x89 H-piles approximately 37 to 47 feet long. Foundation design is based on American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance

Factor Design (LRFD) Bridge Design Specifications (BDS) with Caltrans Amendments methodology.

Static or dynamic pile load testing to evaluate driven pile axial capacity is not considered necessary.

Driven pile acceptance criteria should be based on the criteria set forth in Section 49-2.01A(4)(c) of Caltrans’ 2015 Standard Specifications.

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Excavated soils generated from cut operations at the bridge locations are generally suitable for use as embankment and structure fill. Existing pavement section materials hot mix asphalt (HMA) may be incorporated into engineered fill provided it is pulverized or broken down to at least 3 inches or smaller.

Due to the generally fine-grained nature of the native soils and average in-situ moisture contents above optimum (up to 10-15% or more above), we anticipate that exposed subgrade and excavation bottoms will likely be (at least locally) wet and unstable, regardless of the time of year. In addition, soils below existing pavements are generally wet when exposed.

The existing pavement section appears to be performing well based on a cursory review of the existing pavement conditions (no significant cracking or other distress observed). New flexible pavement may consist of 0.5 feet of HMA over 1.25 feet of Class 2 Aggregate Base (AB) based on Caltrans design standards as specified by Chapter 4 of the UFC 3-250-01, Unified Facilities Criteria (UFC), Pavement

Design for Roads and Parking Areas.

1.0 INTRODUCTION

This report presents the results of our geotechnical investigation for the proposed Wheatland Gate Bridges Replacement project located in the southern portion of Beale AFB east of Yuba City/Marysville in Yuba County, California. The approximate site location is depicted on the Vicinity Map, Figure 1. The approximate exploratory boring locations are shown on the Site Plan, Figure 2.

The purpose of our geotechnical services was to evaluate the subsurface conditions along the project alignment and provide design-level geotechnical recommendations for replacement of Bridge FAC #221 and Bridge FAC #222.

2.0 SCOPE OF SERVICES

To prepare this report, we:

Reviewed published geologic maps, aerial photographs, and other available literature pertaining to the site to aid in evaluating geotechnical, geologic, and seismic conditions at the site. A list of referenced materials is provided in Section 15 of this report.

Provided information on and subcontractor personnel using the Entry Access Listing (EAL) procedure for required security background checks.

Attended a kickoff meeting at the site on March 31, 2017 with representatives of the designer ( ), , and the Air Force. Performed a site reconnaissance to review project limits, determine exploration equipment access and mark out exploratory boring and test pit locations for subsequent utility clearance.

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Notified subscribing utility companies via Underground Service Alert (USA) a minimum of two business days (as required by law) prior to performing exploratory borings at the site. Beale AFB personnel reviewed the proposed boring locations and marked out any potential utility or underground structure conflicts.

Retained the services of a California C57-licensed drilling contractor to perform exploratory borings.

Paid required fees and obtained a subsurface exploration permits from the Yuba County Environmental Health Department (YCEHD).

Performed four exploratory borings (B1 through B4) along the project alignment. One boring was performed near each proposed abutment location for both bridges. Boring depths ranged from approximately 31.5 to 61.5 feet.

Obtained representative disturbed and undisturbed soil samples from the exploratory borings using 3-inch outside diameter (OD) and 2-inch OD (Standard Penetration Test) split spoon samplers.

Bulk samples were also collected.

Logged the borings in general accordance with the Caltrans 2010 Soil and Rock, Logging, Classification, and Presentation Manual. Boring logs are included in Appendix A.

Upon completion, backfilled the borings with neat cement grout per YCEHD/USACE requirements.

Performed laboratory tests to evaluate pertinent geotechnical parameters. Laboratory test results are presented in Appendix B.

Prepared Log of Test Boring (LOTB) sheets in general accordance with the Caltrans 2010 Soil and Rock Logging, Classification, and Presentation Manual. The LOTBs are presented in Appendix C.

Prepared this report summarizing our findings, conclusions, and recommendations regarding the geotechnical aspects of project improvements as presently proposed.

3.0 PROJECT DESCRIPTION

3.1 Background and Site Description

The project will replace two existing timber bridges (Bridge FAC #221, north, and Bridge FAC #222, south) on South Beale Road in the southern portion of Beale AFB. The bridges are located approximately 1 mile south of Gavin Mandry Drive near the wastewater treatment plant and are approximately 1,300 feet apart. The Wheatland Gate access to Beale AFB is approximately 0.2 miles south of Bridge FAC #222. Existing South Beale Road in the vicinity of the two bridges is situated on an embankment fill approximately 10 feet high and consists of two travel lanes (one in each direction) with narrow shoulders and guardrails near the edge of pavement. Except for the elevated roadway embankment and railroad embankment to the east, terrain in the vicinity of the bridges is essentially flat and level with surface drainage to the west.

Elevations provided in this report are based on the North American Vertical Datum of 1988

(NAVD 88).

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3.2 Existing Structures

The existing multi-span bridges are approximately 60 to 75 feet long and of timber construction. Both bridges cross ephemeral creeks or drainage channels. Original design plans and as-built foundation information for the bridges show timber structures supported by reinforced concrete spread foundations at all support locations. The bridges consists of two travel lanes (one each in the south and north direction) with no sidewalks or shoulders. Existing bridge foundations are unknown.

3.3 Proposed Improvements and Structures

The proposed bridge replacements will consist of two, 12-foot wide travel lanes and 4-foot shoulders. We understand that the bridges will be replaced on approximately the same alignment as the existing structures.

The profile will be raised slightly to accommodate roadway and bridge deck drainage. New roadway pavement will consist of hot mix asphalt (HMA) designed in accordance with Caltrans design standards (per UFC 3-201-01 and UFC 3-250-01).

The proposed bridges will consist of new single-span, precast, prestressed concrete box T-beam bridges with cast-in-place diphragm-type abutments supported on driven steel H-piles. Bridge FAC #221 will be 87 feet long and 35.25 feet wide. Bridge FAC #222 will be 76.5 feet long and 35.25 feet wide. The bridges will be designed in accordance with Caltrans design standards.

4.0 FIELD INVESTIGATION AND TESTING PROGRAM

Our field investigation program was performed on April 3 and 4, 2017, and consisted of a site reconnaissance and drilling four exploratory borings (B1 through B4) at the approximate locations shown on Figure 2. Table 4 summarizes the details of our exploratory borings.

TABLE 4

SUMMARY OF BORINGS

Boring

ID

Bridge Structure

Approximate Boring Location Boring Depth (feet)

Drilling Equipment Station No.

Offset from Centerline

(feet)

Approx.

Elevation

(feet NAVD88)

B1 Bridge FAC #222 102+69 0’ 99.2 61.5 CME-55, 4-inch-diameter solid-flight auger, automatic hammer

B2 Bridge FAC #222 103+63 0’ 99.2 31.5 Simco 2400, 4-inch-diameter solid-flight auger, rope-and-cathead hammer

B3 Bridge FAC #221 202+53 1’ Rt. 99.3 31.5 Simco 2400, 4-inch-diameter solid-flight auger, rope-and-cathead hammer

B4 Bridge FAC #221 203+67 1.5’ Rt. 99.5 61.5 CME-55, 4-inch-diameter solid- flight auger, automatic hammer

Soil samples were collected in the borings at approximate two- to five-foot intervals to the total depths explored. Sampling was accomplished using a 140-pound, automatic or rope-and-cathead hammer with a 30-inch drop. Samples were obtained with 3-inch, outside-diameter (OD)

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(California Modified) or 2-inch OD Standard Penetration Test (SPT) split spoon samplers. The California Modified sampler was equipped with 6-inch-long by 2.5-inch-diameter brass/stainless sample tubes. The SPT sampler had a uniform inside diameter that did not allow for sample liners.

The number of blows required to drive the sampler (blow counts) the last 12 inches of the 18-inch sample drive (or portion thereof) are reported on the boring logs (Appendix A) and LOTB sheets included in Appendix C.

5.0 LABORATORY TESTING PROGRAM

We performed laboratory tests in general conformance with California Test Methods (CTM) and generally accepted test methods of the American Society for Testing and Materials (ASTM). We performed the following tests:

In-Place Dry Density and Moisture Content: ASTM D2937 (CTM 226)

Grain Size Distribution/Percent Passing No. 200 Sieve: ASTM D422

Atterberg Limits: ASTM D4318

Unconfined Compressive Strength: ASTM D2166

Moisture-Density Relationship: ASTM D1557 pH and Resistivity: CTM 643

Sulfate Content: CTM 417

Chloride Content: CTM 422

Resistance-Value: ASTM D2844 (CTM 301)

Expansion Index: ASTM D4829

Sand Equivalent: ASTM D2419

Laboratory test results are presented in Appendix B.

6.0 SITE GEOLOGY AND SUBSURFACE CONDITIONS

6.1 Topography

With the exception of the roadway and railroad fill embankments, the project alignment is generally flat and level with a ground surface elevation near elevation 90 feet. At the bridges, the fill embankments rise approximately 10 feet above adjacent grade with side slopes of approximately 2H:1V (horizontal to vertical) and channel thalwegs at about elevation 82 to 85 feet. The site configuration is shown on Figure 2. Site topography and proposed improvements are shown on the LOTBs in Appendix C.

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6.2 Regional Geology

The site is near the approximate margin of the Great Valley and Sierra Nevada geomorphic provinces. The Great Valley (Sacramento and San Joaquin Valleys) of California is a long, sediment-filled structural depression or down-warped trough, with the axis of the trough beneath the west side of the valley. In general, the southern portion of the Sacramento Valley is underlain by Quaternary continental deposits (alluvial deposits) and late Tertiary age marine and continental sedimentary rocks. The Sierra Nevada is a tilted fault block nearly 400 miles long with a high, rugged, multiple-scarp east face contrasting with the gentle western slope that disappears under the sediments of the Great Valley. The site is in a region where both the Sierran bedrock and overlying Great Valley sedimentary deposits are exposed.

Based on the Geologic Map of the Chico Quadrangle, California, California Geological Survey (CGS, 1992), the bridges and existing embankment fills are predominantly underlain by Pleistocene-aged alluvial materials (Modesto Formation, map symbol Qm). South of the bridges is mapped as Riverbank Formation (map symbol Qr), also Pleistocene-aged alluvial materials. North of the bridges geologic mapping shows Laguna Formation (map symbol Pl), an older alluvial formation. Approximate lateral extents of surficial site geology are presented on the Site Plan/Geologic Map, Figure 2.

6.3 Existing Roadway Pavement Sections

At each boring location the existing pavement section consisted of approximately six inches of HMA (seven inches in Boring B2) directly underlain by embankment fill (clayey gravel with sand). No AB layer was observed in our borings. The existing pavement section appears to be performing well based on a cursory review of the existing pavement conditions (no significant cracking or other distress observed). We do not know when the roadway was last repaved.

6.4 Soil Conditions

Subsurface conditions at the bridge locations (below the pavement structural section) generally consists of embankment fill over alluvium. The soil descriptions provided below include the USCS symbol where applicable. Soil conditions described herein are generalized. The exploratory boring logs included in Appendix A and the LOTBs in Appendix C detail soil type, color, moisture, consistency, and USCS classification of the soils encountered at specific locations and elevations.

6.4.1 Embankment Fill

In each exploratory boring, we encountered embankment fill extending from below the roadway pavement section to depths of between approximately 10 to 13 feet. The embankment fill and the underlying alluvial deposits were very similar in material type and consistency and were generally indistinguishable.

Embankment fill primarily consists of reddish brown loose to medium dense clayey gravel (GC) and clayey sand (SC) and medium stiff to stiff lean clay (CL) with varying sand and gravel.

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6.4.2 Alluvium

Alluvium at the bridge locations consists of interbedded clayey sand (SC) and lean clay (CL) with varying sand and gravel content to the maximum depth explored of approximately 61.5 feet. Upper alluvial soils (to depths of approximately 18 to 23 feet) are generally reddish brown and soft to stiff / very loose to medium dense. Below this depth the alluvium is generally very stiff to hard / dense to very dense.

6.5 Groundwater

We encountered groundwater in our borings at depths between approximately 12½ and 18 feet on April 3 and 4, 2017. These depths are generally coincident with the observed surface water elevation in the adjacent ephemeral drainages at the time.

Fluctuations of groundwater levels may occur due to variations in precipitation, temperature, and other factors. Depth to groundwater can also vary significantly due to localized pumping, irrigation practices, and seasonal fluctuations. Therefore, it is possible that future groundwater may be higher or lower than the levels observed during our investigation.

6.6 Geologic Hazards

6.6.1 Landslides

No landslides were observed during our site investigation, and none are known to exist at a location that would impact the proposed project.

6.6.2 Embankment Failures

No embankment failures were observed during our site investigation. The existing 2H:1V embankment side slopes appear to be performing well without overt indicators of instability.

6.6.3 Ground Subsidence

Ground subsidence occurs where underlying loose materials undergo a densification process.

Subsidence can result from the extraction of mineral resources and/or groundwater, as well as rapid settlement induced by seismic activity. Based on the subsurface conditions at the site, the potential for ground subsidence is considered low.

6.6.4 Expansive Soils

Based on the results of our field exploration and laboratory testing (Appendix B), near surface soils are generally considered to have low potential expansion.

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6.6.5 Collapsible Soils

Collapsible soils are typically characterized as unsaturated soils that undergo volumetric compression upon saturation without an increase in external loads. Collapsible soils are generally porous with a low dry density. We did not observe low-density, porous, or honeycomb structure soils at the site.

Therefore, the potential for collapsible soils to impact the proposed improvements is considered low.

6.6.6 Fault Rupture

The project site does not lie within or adjacent to an Alquist-Priolo Earthquake Fault Zone. In addition, the site is not located on any known “active” earthquake fault trace. Therefore, we consider the potential for ground rupture due to onsite active faulting to be low.

6.6.7 Liquefaction

Liquefaction is a phenomenon in which saturated cohesionless soils are subject to a temporary loss of shear strength due to pore pressure buildup under the cyclic shear stresses associated with intense earthquakes. Primary factors that trigger liquefaction are: moderate to strong ground shaking (seismic source), relatively clean, loose granular soils (primarily poorly graded sands and silty sands), and saturated soil conditions (shallow groundwater). Due to the increasing overburden pressure with depth, liquefaction of granular soils is generally limited to the upper 50 feet of a soil profile.

Based on the general subsurface conditions encountered at the site and the anticipated seismic conditions, we consider the potential for liquefaction to be low, and mitigation and/or special design measures with respect to liquefaction are not necessary.

6.6.8 Lateral Spreading

Due to the low potential for liquefaction and the geometry of subsurface conditions at the site, seismic-induced lateral spreading is not considered a hazard at the site.

6.6.9 Unsaturated Seismic Settlement

In addition to liquefaction of loose, saturated sandy soil, strong seismic shaking can induce settlement of unsaturated, loose sandy soil. Based on the subsurface conditions encountered at the site, it is our opinion that the potential for significant settlement (greater than 1 inch) of unsaturated soils due to seismic shaking is low.

6.6.10 Slope Stability

We did not observe localized slumping, deep-seated slope failures, debris slides/flows, significant channel bank failures, or conditions indicative of active landslides, such as headscarps or toe bulges during our investigation. The embankment fill slopes at the site appear to be performing well without evidence of global instability.

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Permanent cut and fill slopes should be constructed no steeper than 2H:1V (horizontal to vertical). To mitigate potential erosion, slopes should be vegetated as soon as possible and surface drainage should be directed away from the tops of slopes. Assuming that fill materials meet the requirements of this report, 2H:1V fill slopes should have a sufficient factor of safety against deep seated failures under static and seismic loading.

7.0 SCOUR EVALUATION

Scour information provided by is shown in Table 7. Existing fill and alluvial soils observed at the bridge sites are not considered scour-resistant.

TABLE 7

SCOUR DATA TABLE

Bridge Structure

Support No.

Long Term (Degradation and

Contraction) Scour Depth

(ft)

Short Term (Local) Scour

Depth (ft)

Total Scour Depth

(ft)

Scour Elevation (Short Term and

Long Term) (ft)

Bridge FAC #221

Abutment 1 0.2 6.7 6.9 86.6

Abutment 2 0.2 6.3 6.5 86.8

Bridge FAC #222

Abutment 1 0.6 4.7 5.3 88.2

Abutment 2 0.2 3.6 3.8 89.7

8.0 CORROSION SCREENING

According to Caltrans’ Corrosion Guidelines (Version 2.1, January 2015), soils are considered corrosive to foundation elements if one or more of the following conditions exist: chloride concentration is 500 parts per million (ppm) or greater, or sulfate concentration is 2,000 ppm or greater, or the pH is

5.5 or less. Resistivity serves as an indicator parameter for the possible presence of soluble salts and is not included as a parameter to define a corrosive area for structures. A minimum resistivity value for soil and/or water less than 1,000 ohm-centimeters may indicate the presence of high quantities of soluble salts and a higher propensity for corrosion.

We performed pH, resistivity, chloride content, and soluble-sulfate content tests in accordance with CTM Nos. 643, 417, and 422 on four representative soil samples to generally evaluate the soil corrosion potential. Test results are summarized in Table 8 and Appendix B and should be considered for design.

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TABLE 8

SOIL CORROSION TEST SUMMARY

Sample ID (Boring No./

Sample Depth)

Minimum Resistivity

(ohm-centimeters) pH

Chloride Content (ppm)

Sulfate Content (ppm)

B1 / 15.5 1,200 6.9 77 220 B2 / 25.0 920 6.9 104 20 B3 / 30.0 1,000 7.0 84 10 B4 / 15.5 1,700 6.9 56 170

Based on the laboratory test results, site soils are classified as non-corrosive according to Caltrans’ Corrosion Guidelines. Proposed improvements in contact with the ground should be designed and constructed in accordance with Caltrans’ Standard Specifications and good construction practices.

does not practice corrosion engineering. If corrosion sensitive improvements are planned, we recommend further evaluations by a corrosion engineer.

9.0 SEISMIC RECOMMENDATIONS

We developed preliminary design response spectra for the proposed replacement bridge structures in accordance with Caltrans’ 2012 Methodology for Developing Design Response Spectrum for Use in

Seismic Design Recommendations. The bridges are not located within a deep sedimentary basin per Caltrans ARS Online. Using published correlations, a shear wave velocity in the top 30 meters (100 feet), Vs30 was estimated for the soil profiles at the bridge sites. Table 9a summarizes the site-specific information used:

TABLE 9a

SITE INFORMATION FOR SEISMIC ANALYSIS

Site Name Latitude (ºN) Longitude (ºW) Caltrans Soil Profile Type VS30 (m/sec)

Bridge FAC #221 39.088334 -121.42142 D 278

Bridge FAC #222 39.085094 -121.423457 D 282

Note:

The sites are not located within sedimentary basin as mapped/defined by Caltrans’ Seismic Design Criteria (Appendix B);

therefore, Basin Factors are not applicable.

Based on Caltrans’ web-based ARS Online application (V2.3.07, accessed April 19, 2017) and associated reports, the controlling faults for potential earthquake ground motions at the sites are summarized in Tables 9b and 9c.

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TABLE 9b

FAULT INFORMATION – BRIDGE FAC #221

Fault Name

Foothills Fault System – northern reach section (Spenceville Fault)

Foothills Fault System – north central reach section (DeWitt Fault)

Foothills Fault System – northern reach section (Swain Ravine Fault

Zone)

Fault ID# 81 423 71 MMax 6.5 6.3 6.5

Fault Type N N N Fault Dip 50° 50° 50°

Dip Direction West West West Top of Rupture 0 km 0 km 0 km

Bottom of Rupture 10 km 10 km 10 km Distance to Site (RRUP) 8.5 km 21.0 km 29.5 km

Depth to rock with Shear Wave Velocity of

1 km/sec (Z1.0) n/a* n/a* n/a*

Depth to rock with Shear Wave Velocity of

2.5 km/sec (Z2.5) n/a* n/a* n/a*

*Note: The site is not located within sedimentary basin as mapped/defined by Caltrans’ Seismic Design Criteria (Appendix B);

TABLE 9c

FAULT INFORMATION – BRIDGE FAC #222

Fault Name

Foothills Fault System – northern reach section (Spenceville Fault)

Foothills Fault System – north central reach section (DeWitt Fault)

Foothills Fault System – north central reach section (Hwy 49 Fault)

Fault ID# 81 423 424 MMax 6.5 6.3 6.2

Fault Type N N N Fault Dip 50° 50° 50°

Dip Direction West West West Top of Rupture 0 km 0 km 0 km

Bottom of Rupture 10 km 10 km 10 km Distance to Site (RRUP) 8.7 km 20.9 km 22.6 km

Depth to rock with Shear Wave Velocity of

1 km/sec (Z1.0) n/a* n/a* n/a*

Depth to rock with Shear Wave Velocity of

2.5 km/sec (Z2.5) n/a* n/a* n/a*

*Note: The site is not located within sedimentary basin as mapped/defined by Caltrans’ Seismic Design Criteria (Appendix B);

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Both the deterministic and probabilistic response spectra of the site were estimated using Caltrans’ Deterministic Response Spectrum and Probabilistic Response Spectrum spreadsheets and the USGS

Beta - Unified Hazard Tool and the Caltrans ARS Online web tools. The design response spectrum is the upper envelope of the spectral values of deterministic response spectrum and the probabilistic response spectrum. For these bridges, the design response spectrum is controlled by the Foothills Fault northern reach section (Spenceville fault) deterministic analysis (with the near fault factor applied) for periods of 0 to 2 seconds and the Caltrans ARS Online Probabilistic Model for periods of 3 to 5 seconds. The design response spectra are shown on the Recommended Design Response Spectrum, Figures 5 and 6. The peak ground accelerations generated by the design spectrum are 0.34g for Bridge FAC #221 and 0.33g for Bridge FAC #222, respectively.

10.0 AS-BUILT FOUNDATION DATA

Original design plans for the bridges (Typical Bridge Plan, Typical Bridge Sections, and Bridges No. 3 &

No. 4 Profiles, January 1952) indicate the bridges are supported by reinforced concrete seat-type abutments with reinforced concrete spread footings at all support locations. Bottom of footing elevations are based on an assumed roadway elevation of 100.0 feet and are shown on the plans at the approximate elevations (to the nearest ½ foot) in Tables 10a and 10b.

TABLE 10a

DESIGN BOTTOM OF FOOTING ELEVATIONS – EXISTING BRIDGE FAC #221

Support Location Approximate Bottom of Footing Elevation

(feet)

Abutment 1 84½

Pier 2 82½

Pier 3 78½

Pier 4 78½

Pier 5 82½

Abutment 6 84½

TABLE 10b

DESIGN BOTTOM OF FOOTING ELEVATIONS – EXISTING BRIDGE FAC #222

Support Location Approximate Bottom of Footing Elevation

(feet)

Abutment 1 88½

Piers 2 through 4 84

Abutment 5 88½

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11.0 FOUNDATION RECOMMENDATIONS

Based on the subsurface conditions encountered in our borings and our discussions with the project team, the replacement bridges may be supported on driven steel H-Piles. Piles will derive axial capacity from a combination of skin friction and end bearing. Based on the soil conditions encountered during our investigation, use of spread footings is not recommended due to the potential for significant settlement.

Scour considerations also precludes the use of shallow foundations at abutment locations.

Foundation design presented in this report is based on American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design

Specifications (BDS) with Caltrans Amendments methodology. The new bridges have diaphragm abutments; therefore lateral loading design is to be performed by the structural engineer, if necessary.

11.1 Deep Foundations

Based on the subsurface conditions and design loading, foundations at the abutment locations should consist of HP 14x89 driven steel H-piles. H-piles should be able to penetrate the dense and cemented soil layers to provide axial support for the proposed bridge. Due to the presence of hard/very dense and cemented soil layers, difficult driving conditions may be encountered prior to reaching the specified tip elevations.

Foundation design information in accordance with Caltrans’ procedures and our recommendations are presented in Tables 11.1a through 11.1d.

TABLE 11.1a

DESIGN LOADS FROM THE STRUCTURAL DESIGNER1

Foundation Factored Design Loads

Support No.

Service-I Limit State (kips)

Strength/Construction Limit State (Controlling Group, kips)

Extreme Event Limit State (Controlling Group, kips)

Total Load Per Support

Permanent Loads Per Support

Compression Tension Compression Tension

Per Support

Max.

Per Pile

Per Support

Max.

Per Pile

Per Support

Max.

Per Pile

Per Support

Max.

Per Pile

Bridge FAC #221

Abut 1 980 700 1,470 210 0 0 N/A N/A N/A N/A

Abut 2 980 700 1,470 210 0 0 N/A N/A N/A N/A

Bridge FAC #222

Abut 1 840 600 1,260 210 0 0 N/A N/A N/A N/A

Abut 2 840 600 1,260 210 0 0 N/A N/A N/A N/A

Notes:

1. Information provided by .

- 14 - May 25, 2017

TABLE 11.1b

FOUNDATION RECOMMENDATIONS

Support Pile

Type

Cut-off Elevation

(feet)

Service-I Limit State Load per

Support (kips)

Total Permissible

Support Settlement

(inches)

Required Factored Nominal Resistance (kips) Design Tip

Elevations (feet)1, 2, 3

Specified Tip

Elevation (feet)2

Nominal Driving

Resistance (kips)

Strength/Construction Extreme Event

Total Permanent Comp.

(φ=0.7)

Tension (φ =0.7)

Comp.

(φ =1.0)

Tension (φ =1.0)

Bridge FAC #221

Abut 1 HP 14x89 86.9 980 700 1 210 0 0 0 38 (a-I) 38 350

Abut 2 HP 14x89 86.9 980 700 1 210 0 0 0 38 (a-I) 38 350

Bridge FAC #222

Abut 1 HP 14x89 88.4 840 600 1 210 0 0 0 50 (a-I) 50 350

Abut 2 HP 14x89 89.9 840 600 1 210 0 0 0 50 (a-I) 50 350

Notes:

1. Design tip elevations are controlled by: (a-I) Compression (Strength Limit).

2. The specified tip elevation shall not be raised above the design tip elevations for lateral capacity.

3. Design tip elevation for lateral capacity is determined by the structural engineer.

TABLE 11.1c

PILE DATA TABLE

Location Pile

Type

Nominal Resistance (kips)

Design Tip Elevation (ft)1, 2

Specified Tip Elevation (ft)2

Required Nominal Driving Resistance (kips)

Compression Tension

Bridge FAC #221

Abut 1 HP 14x89 300 0 38 (a-I) 38 350

Abut 2 HP 14x89 300 0 38 (a-I) 38 350

Bridge FAC #222

Abut 1 HP 14x89 300 0 50 (a-I) 50 350

Abut 2 HP 14x89 300 0 50 (a-I) 50 350

Notes:

1. Design tip elevations are controlled by: (a) Compression.

2. Design tip elevation for lateral capacity is determined by the structural engineer. The specified tip elevation shall not be raised above the design tip elevations for lateral capacity.

Settlement of piles under service loads is expected to be approximately ½-inch or less. Settlement should be essentially complete shortly after completion of the bridge superstructure.

Based on the current Caltrans guidelines (Memo to Designers 3-1, June 2014, LRFD version), the design tip elevations for lateral capacity are evaluated and determined by the structural designer. The specified pile length should not be less than the critical length for which greater lengths do not result in

- 15 - May 25, 2017 a significant reduction in lateral deflection at the pile top. Tables 11.1d and 11.1e summarize our recommended soil parameters for lateral analysis using the software LPILE by Ensoft. We recommend that group effects be accounted for in analysis by using the recommendations of California

Amendments to AASHTO LRFD Bridge Design Specifications Table and Figure 10.7.2.4-1.

TABLE 11.1d

RECOMMENDED SOIL PARAMETERS FOR LPILE ANALYSIS – BRIDGE FAC #221

Soil Layer

LPILE Soil Model

Approximate Elevation Effective Unit

Weight (pcf)

Friction Angle

Undrained Cohesion c (psf) Top Bottom

1 Sand (Reese) 85 76 63 30 --

2 Sand (Reese) 76 71 68 38 --

3 Stiff Clay with Free Water (Reese) 71 66 68 -- 3000

4 Sand (Reese) 66 57 68 38 --

5 Stiff Clay with Free Water (Reese) 57 38 68 2500 --

Notes:

pcf = pounds per cubic foot psf = pounds per square foot

TABLE 11.1E

RECOMMENDED SOIL PARAMETERS FOR LPILE ANALYSIS – BRIDGE FAC #222

Soil Layer

LPILE Soil Model

Approximate Elevation Effective Unit

Weight (pcf)

Friction Angle

Undrained Cohesion c (psf) Top Bottom

1 Stiff Clay with Free Water (Reese) 88 81 63 -- 1200

2 Sand (Reese) 81 71 78 36 --

3 Stiff Clay with Free Water (Reese) 71 46 78 -- 5000

4 Sand (Reese) 46 38 78 38 -- Notes:

pcf = pounds per cubic foot psf = pounds per square foot

11.2 Special Considerations for Driven Piles

Due to the presence of hard/very dense and cemented soil layers at depth, difficult driving conditions may be encountered prior to reaching the specified tip elevations. The contractor should have all equipment available onsite to install the piles to the design tip elevation. For this project, jetting or vibrating of piles is not an allowable method of pile installation.

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11.3 Pile Acceptance Criteria

The contractor should prepare and submit a complete Driving System Submittal per Caltrans’ 2015 Standard Specifications Section 49-2.01A(3)(b) prior to construction.

Static or dynamic pile load testing to evaluate driven pile axial capacity is not considered necessary.

Driven pile acceptance criteria should be based on the criteria set forth in Section 49-2.01A(4)(c) of Caltrans’ 2015 Standard Specifications. The piles must be driven to at least nominal driving resistance and specified tip elevations shown on project plans. Specifically, within the last foot of pile driving, a formula correlating the installation hammer blows and manufacturer’s hammer energy rating to the nominal driving resistance is required for driven pile field acceptance.

Piles that demonstrate “refusal” as much as 3 feet above specified tip elevation may be accepted without review/consultation. Acceptance of piles meeting formula bearing at levels higher than this should be made only on the basis of specific review by . Driving “refusal” can be defined as piles obtaining two times formula bearing blow counts for the last foot, or three times formula bearing blow counts for the last three inches (prorated).

Piles that do not attain the required nominal driving resistance at the specified tip may be considered acceptable with formula bearing on redrive after a minimum 24-hour “set period.” A longer set period may result in additional set-up by the pile. If there is more than one “soft” pile, then will designate which pile(s) is/are to be redriven. Do not use a cold hammer for redriving.

If the nominal driving resistance is attained for the pile designated to be redriven, the remaining piles in that footing are considered satisfactory and further driving will not be required. If redriving the designated pile demonstrates that the nominal driving resistance has not been attained, redrive all “soft” piles in the footing until the nominal driving resistance is attained.

11.4 Retaining Walls/Wingwalls

The project designer should evaluate the conditions of retaining structures (restrained or non-restrained) and use the appropriate design parameters. Walls allowed to rotate more than 0.001H (where H equals the retained height of the wall) at the top of the wall are considered non-restrained. Non-restrained walls having a level backfill surface should be designed for an active soil pressure equivalent to the pressure exerted by a fluid density of 40 pounds per cubic foot (pcf). Restrained walls should be designed for an at-rest equivalent fluid pressure of 60 pcf. For retaining walls subject to vehicular loads within a horizontal distance equal to two-thirds the wall height, a surcharge equivalent of 2 feet of fill soil (unit weight of 125 pcf) should be added. For a seismic case analysis, an incremental seismic pressure of 10 pcf should be applied to the wall. The incremental seismic pressure should be combined with the active lateral earth pressure. We recommend use of a conventional triangular distribution for the incremental seismic pressure.

- 17 - May 25, 2017

Walls should have a back-drainage system similar to Caltrans’ Standard Plan BO-3, Bridge Detail 3-1 or an approved geocomposite chimney type drain material. The back-drainage system should provide positive drainage to daylight and be maintained such that it does not clog with debris and allow a buildup of hydrostatic pressure.

12.0 GRADING AND EARTHWORK RECOMMENDATIONS

12.1 General

Conclusions and recommendations presented herein are based on our review of the referenced literature, analysis of data obtained from our field exploration program, laboratory testing program, and our understanding of proposed improvements at this time.

Proposed bottom of pile cap elevations appear to be similar to bottom of footing elevations for the existing bridges. We do not expect significant overexcavation to be required for removal of the existing abutments.

We should review the project plans as they develop further, provide engineering consultation as needed during final design, and perform geotechnical observation and testing services during construction.

12.2 Soil and Excavation Characteristics

In our opinion, grading and excavations at the bridge sites may be accomplished with standard to moderate effort using heavy-duty grading/excavation equipment.

Temporary excavation slopes entered by workers must meet Cal/OSHA requirements as appropriate.

Excavation sloping, benching, the use of trench shields, and the placement of excavation spoils should conform to the latest applicable Cal/OSHA standards. The contractor should have a Cal/OSHA-approved “competent person” onsite during excavation to evaluate excavation conditions and to make appropriate recommendations where necessary. It is the contractor’s responsibility to provide sufficient and safe excavation support as well as protecting nearby utilities, structures, and other improvements, which may be damaged by earth movements.

The excavation support recommendations provided by Cal/OSHA are generally geared towards protecting human life and not necessarily towards preventing damage to nearby structures or surface improvements.

The contractor is responsible for using the proper shoring systems or sloping to prevent damage to any structure or improvements near underground excavations.

Permanent fill and cut slopes adjacent to the roadway should be constructed at 2H:1V (horizontal to vertical) or flatter.

- 18 - May 25, 2017

To reduce erosion potential, erosion control features should be installed as soon as possible and surface drainage should be directed away from the tops of slopes.

12.3 Materials for Fill

Excavated soils generated from cut operations at the bridge locations are suitable for use as embankment fill and structure backfill provided they do not contain deleterious matter, organic material, rock, or cementations larger than 3 inches in maximum dimension. Existing pavement section materials (HMA) may be incorporated into engineered fill provided it is pulverized or broken down to at least 3 inches or smaller.

Import fill material, if required, should be similar to or better than native soils with a minimum R-Value of 29, be free of organic material and construction debris, and not contain rock larger than 3 inches in greatest dimension. Backfill soil placed behind walls and wing walls (structure backfill) should be primarily granular in nature, have an Expansion Index of less than 50, and a Plasticity Index of 15 or less.

We expect that the majority of the excavated materials should meet these criteria.

Environmental characteristics and corrosion potential of import soil materials should also be considered.

Proposed import material should be sampled, tested, and approved by prior to its transportation to the site. Approval of import material may take up to one week if laboratory testing is required.

12.4 Groundwater, Wet Soils

If grading commences in winter or spring, or during/after periods of precipitation, excavated and in-place soils will likely be wet. Earthwork contractors should be aware of moisture sensitivity of clayey and fine-grained soils and potential compaction/workability difficulties. Grading and earthwork operations in these conditions will likely be difficult with low productivity. Often, a period of at least one month of warm and dry weather is necessary to allow the site to dry sufficiently so that heavy grading equipment can operate effectively. We highly recommend performing grading and earthwork during the summer or fall seasons, when favorable weather is more likely.

Based on laboratory testing, optimum moisture content of embankment fill soil is approximately six percent. Due to the fine-grained nature of some of these soils and average in-situ moisture contents above optimum (up to 10-15% or more above), we anticipate that exposed subgrade and excavation bottoms will likely be (at least locally) wet and unstable, regardless of the time of year. In addition, soils below existing pavements are generally wet when exposed. Mitigation alternatives may include aerating/drying the exposed soils (assuming favorable weather conditions), over-excavating 12 to 18 inches and placing geotextile fabric/geogrid covered with aggregate, or chemical treatment (e.g. lime treatment). We can provide specific recommendations during construction based on conditions encountered.

- 19 - May 25, 2017

We anticipate that there will be seepage into pile cap excavations if water is present in the creeks. Sloping excavation bottoms to periodically spaced sumps with high capacity pumps will likely be sufficient for managing seepage. In this case, a 1- to 2-foot-thick layer of freely draining gravel or crushed rock wrapped in an approved geotextile fabric, such as Mirafi 500X, on the excavation bottom would enable groundwater to flow toward the sump as well as provide a working surface.

12.5 Grading

Grading and earthwork operations should be continuously observed and all fills tested for recommended compaction and moisture content by a representative of our firm.

References to relative compaction and optimum moisture content in this report are based on the American Society for Testing and Materials (ASTM) D1557 Test Procedure, latest edition.

Prior to commencing grading, a pre-construction meeting with representatives of Beale AFB, civil engineer, grading contractor, and should be held at the site. Site preparation, soil handling and/or the grading plans should be discussed.

Site preparation should begin with removal of existing surface and subsurface structures not designated to remain. Existing pavement materials need not be off-hauled provided they are processed/pulverized to meet the requirements provided in Section 12.3 of this report. Trees, bushes, surface vegetation, topsoil, and deleterious material should be removed and exported from the site or used in non-structural fill areas.

We anticipate stripping depths on the order or 2 to 6 inches will be required to effectively remove surface vegetation.

Existing embankment slopes and other areas to receive fill or new pavement should be cleared of vegetation and other unsuitable surface materials and excavated to remove saturated/unstable soil to expose firm, undisturbed materials.

Excavations or depressions resulting from site clearing operations, or other existing excavations or depressions, should be restored with engineered fill in accordance with the recommendations of this report.

Areas left at grade, areas to receive fill, and the bottoms of over-excavated areas should be scarified at least 12 inches, uniformly moisture conditioned to at or above optimum moisture content, and compacted to at least 90% relative compaction. Scarification and re-compaction operations should be performed in the presence of a representative to evaluate the performance of the subgrade under compaction equipment loading.

- 20 - May 25, 2017

Engineered fill material should be compacted in horizontal lifts not exceeding 8 inches (loose thickness) and brought to final subgrade elevations. Each lift should be moisture-conditioned at or above optimum and compacted to at least 90% relative compaction. For structure backfill, each lift should be moisture-conditioned to at least 2% over optimum and compacted to at least 92% relative compaction.

Fill placed in existing embankment slopes should be keyed at least two feet deep at the toe of the slope and fully benched into the slope at two-foot intervals as the fill is placed.

The top 6 inches of final pavement subgrade should be moisture-conditioned at or above optimum moisture content and compacted to a minimum of 95% relative compaction. Final pavement subgrade should be finished to a smooth, unyielding surface. We recommend proof-rolling the subgrade with a loaded water truck (or similar equipment with high contact pressure) to verify stability of subgrade.

Underground utility trenches (if any) should be backfilled with properly compacted material. Pipe bedding, shading, and trench backfill should conform to the requirements of the appropriate utility authority. Soil excavated from trenches should be adequate for use as general backfill above shading provided it does not contain deleterious matter, vegetation or rock/cementations larger than 3 inches in maximum dimension. Trench backfill should be placed in loose lifts not exceeding 8 inches. Lifts should be compacted to a minimum of 90% relative compaction at or above optimum moisture content.

Compaction should be performed by mechanical means only; jetting of trench backfill is not recommended.

13.0 PAVEMENT RECOMMENDATIONS

Subgrade soils predominantly consist of silty/clayey sand and gravel and sandy and gravelly lean clays with low to medium plasticity. Subgrade soil R-Value test results were 29 and 65, which indicate relatively good pavement support characteristics. has provided a design Traffic Index of 10.0 for this roadway.

Based on the results of our investigation, existing pavement sections along the alignment generally consist of approximately 6 inches of HMA over embankment fill. The existing pavement section appears to be performing well based on a cursory review of the existing pavement conditions (no significant cracking or other distress observed). We do not know when the roadway was last repaved.

We performed laboratory Resistance Value (R-Value) testing on two near surface soil samples to evaluate pavement support characteristics. R-Value test results are summarized in Table 13a. We note that the R-Value test result from Boring B4 was 65, indicating (at least locally) pavement support conditions better than aggregate subbase (R-Values between 40 and 60) but not quite reaching those of AB (R-Value of 78). Local variations in clay, sand, and gravel content likely contribute to the variation noted in the two R-Value test results. To account for subgrade variability, we recommend an R-Value of 29 be used for project design.

- 21 - May 25, 2017

TABLE 13a

SUMMARY OF R-VALUE TEST RESULTS

Sample ID Sample Description R-Value

B2-Bulk Clayey GRAVEL with Sand (GC) 29 B4-Bulk Clayey GRAVEL with Sand (GC) 65

We understand Traffic Index (TI) of 10.0 is to be used for design. Table 13b provides the design pavement structural section based on the design TI…