CA.ERFO.KLAMATH NF.18N31(1).Upper West Branch Bridge.Geotech Rpt FINAL.November 2021.Drilled Shafts.pdf

UPPER WEST BRANCH BRIDGE

KLAMATH NATIONAL FOREST

SISKIYOU COUNTY, CA

CA ERFO 18N31(1)

FINAL Geotechnical Report

Prepared by Federal Highway Administration

Central Federal Lands Highway Division

Geotechnical Services Branch November 2021 ii

SIGNATURE SHEET

Report prepared by: ___________________________________________________________

Devin T. Dixon, P.E., Geotechnical Engineer

Report reviewed by: ____________________________________________________________

James M. Arthurs, P.E., Ph.D., Geotechnical Engineer

Approved for distribution by: ____________________________________________________

Marilyn D. Dodson, P.E., Lead Geotechnical Engineer

Distribution

Electronic:

N:\CA\erfo18n31(1)\Geotech\7_FinalDocs K:\TechServices\Geotech\1. Geotech Project Reports Project Management Project Development, Lead Designer Bridge

Page | i

TABLE OF CONTENTS

SECTION ONE - INTRODUCTION

1.1 BACKGROUND AND LOCATION

1.2 SCOPE AND PURPOSE

SECTION TWO - GEOLOGY AND SEISMICITY

2.1 REGIONAL GEOLOGY

2.2 SITE GEOLOGY

2.3 REGIONAL SEISMICITY

2.4 SEISMIC DESIGN PARAMETERS

2.5 GEOLOGIC HAZARDS

SECTION THREE - SUBSURFACE INVESTIGATION

3.1 SUBSURFACE EXPLORATION PROGRAM

3.2 LABORATORY TESTING PROGRAM

3.3 SUMMARY OF SITE CONDITIONS

3.3.1 General Topography

3.3.2 Surface Reconnaissance

3.3.3 Subsurface Conditions

3.3.4 Groundwater

SECTION FOUR - ANALYSIS & RECOMMENDATIONS

4.1 FOUNDATIONS

4.1.1 Bridge Foundation Selection

4.1.2 Site Characterization

4.1.3 Drilled Shaft Axial Resistance

4.1.4 Group Effects on Axial Resistance

4.1.5 Lateral Loads on Deep Foundations

4.1.6 Settlement

4.1.7 Recommended Shaft Lengths

4.1.8 Field Testing

4.1.9 Scour Potential and Erosion

4.2 ABUTMENT & WINGWALL DESIGN

4.3 PERMANENT EARTHWORKS

4.3.1 Embankment Construction

4.3.2 Shrink/Swell Recommendations

4.4 CONSTRUCTION CONSIDERATIONS

4.5 SPECIFICATIONS

4.6 DISCLAIMER/LIMITATIONS CLAUSE

SECTION FIVE - REFERENCES

Page | ii

TABLES

TABLE 2.1 Summary of Nearby Seismic Source Faults TABLE 2.2 Summary of Seismic Parameters Corrected for Site Class C TABLE 3.1 Summary of Field Exploration Program TABLE 3.2 Summaries of Laboratory Index Test Results TABLE 3.3 Summaries of Laboratory Corrosivity Results TABLE 3.1 Summary of Uniaxial Compressive Strength Results TABLE 4.1 Proposed Bridge Foundation Location TABLE 4.2 LPILE Input Parameters TABLE 4.3 Shaft Lengths Required for Axial and Lateral Loading TABLE 4.4 Lateral Earth Pressures for Bridge Abutments & Wingwalls

PLATES

PLATE 1 Project Vicinity Map PLATE 2 Geology Map PLATE 3 Geology Map Legend PLATE 4 Upper West Branch Bridge Geotechnical Boring Locations PLATE 5 Areas More Likely to Contain Naturally Occurring Asbestos: Klamath N.F.

APPENDICES

APPENDIX A Field Exploration Program APPENDIX B Laboratory Test Results APPENDIX C Photographs APPENDIX D Excavation Characteristics of Rock & Rippability Charts APPENDIX E Select Geotechnical-Related Existing Bridge Sheets

Page | 1

Upper West Branch Bridge, CA ERFO 18N31(1) November 2021

SECTION ONE - Introduction

1.1 BACKGROUND AND LOCATION

This report presents the results of the geotechnical engineering study and provides recommendations for the replacement of the Upper West Branch Bridge in Siskiyou County, California. The project proposes to replace the existing Upper West Branch Bridge, which is located on Forest Route 18N31 within the Klamath National Forest. A project vicinity map is presented on Plate 1 of this report.

The Upper West Branch Bridge was severely damaged by fire during the 2020 season. The Forest Service has since closed the bridge, yet damaged bridge components and debris remain.

The former Upper West Branch Bridge was constructed as a single lane bridge in 1966 and designed to H-15 design vehicle loading. The superstructure consisted of steel pony trusses with longitudinal timber decking and timber railing. The substructure consisted of vertical concrete abutment walls on spread footings supported on steel piles founded on rock. No concrete wingwalls were indicated per plans. Full bridge plans and an inspection report from 2019 were available from the Forest Service. Select geotechnical-related existing bridge plan sheets are included in Appendix E.

The Upper West Branch Bridge will be replaced to meet current HL-93 design vehicle loading.

The proposed replacement structure type is assumed to be precast, prestressed 33 inch deep concrete box girders with asphalt wearing surface. The replacement bridge will be single-span.

Cellulose nanomaterials are anticipated to be used for the deck concrete per guidance from the Forest Service. The potential for scour also exists at the bridge location and deep foundations bearing on suitable materials below such susceptible soils would provide protection against this problem. Deep foundations are proposed since spread footers likely cannot be founded on competent soils or rock at a reasonable cost. Considerations related to the abutments for the Upper West Branch Bridge are presented in Section 4 of this report.

1.2 SCOPE AND PURPOSE

The scope of work included a geotechnical investigation, analysis, and recommendations for bridge foundations for use in design and construction. This involved several tasks including field reconnaissance, subsurface sampling, laboratory testing, interpretation and correlation of field measurements, and geotechnical engineering analysis. Specifically, this investigation was conducted to determine the soil profile at the bridge location and develop recommendations concerning bridge foundations, retaining structures, geologic hazards, and construction considerations.

Page | 2

We understand that a hydraulics report has been prepared under separate cover by the CFLHD Hydraulics Engineer. The hydraulics report includes discussion of flood impacts, such as bridge scour and water surface elevations.

Page | 3

SECTION TWO - Geology and Seismicity

2.1 REGIONAL GEOLOGY

The project is located within the Klamath Mountains Section of the Pacific Border Province. This province is part of the Pacific Mountain System physiographic region. The Pacific Border Province is a long region that runs along the western margin of the United States. This province is characterized by two distinct types of topography: lowlands and mountains (NPS, 2020). Features and landscapes within this province are characterized by a mixture of land and ocean sediments, highly variable geology, and an active plate boundary along the eastern edge of the Pacific Ring of Fire.

Quaternary and Tertiary rocks and deposits that exist within the region include landslide and glacial deposits such as outwash and moraines. Cretaceous aged units primarily include partly to completely serpentinized ultramafic rocks. Jurassic aged units include the Galice Formation, which consists of slate, metagraywacke, & some massive greenstone, as well as dioritic rocks, which consist of tonalite to diorite with some gabbro. Triassic aged and older units include those within the Western Paleozoic and Triassic Belt, which include an assemblage of diverse rocks types including metasedimentary and metavolcanic rocks, gabbro, diabase, serpentinite, and schist/greenschist (Wagner & Saucedo, 1987).

2.2 SITE GEOLOGY

Although not mapped, the soil conditions at the site are assumed to be alluvium based on the stream bed deposits. The project site is mapped as underlain by gabbro, dioritic rocks, and Galice Formation geology. Landslide deposits are also mapped in the vicinity of the sites. These observations are consistent with the borings as will be discussed in Section 3 of this report. The deposits and landforms are a result of both plate tectonics and volcanic activity, and the terrain can be described as mountainous and rugged. A geology map of the project area and corresponding map legend are presented in Plates 2 & 3.

2.3 REGIONAL SEISMICITY

Seven seismic hazard faults are located within 50 miles of the project. These faults are summarized in Table 2.1. The Surpur Creek Fault, Unnamed Fault South of Crescent City, Lost Man Fault, Bald Mountain-Big Lagoon Fault Zone, and Grogan Fault are located west and southwest of the project sites and the Whaleshead Fault Zone and Chetco River Fault are located northwest of the project sites. Known slip rates are less than 0.008 inches per year (USGS, 2020a). Based on the distance to these faults, surface rupture at the bridge sites is not anticipated.

Page | 4

Table 2.1 - Summary of Nearby Seismic Source Faults

FAULT OR

FAULT ZONE

DISTANCE

FROM

CENTER OF

PROJECT

SLIP-RATE

CATEGORY

DIP

DIRECTION

AVERAGE

STRIKE

FAULT

LENGTH

TIME OF MOST

RECENT

DEFORMATION

(miles) (inch/year) (miles) (years) Surpur Creek Fault, (Class A) No. 148

36.2 Unspecified Unspecified Unspecified 26.7 <1,600,000

Unnamed Fault South of Crescent City (offshore), (Class A) No. 431

39.5 Unspecified Unspecified Unspecified Not listed <1,600,000

Lost Man Fault, (Class A) No. 147

44.6 <0.00787 Unspecified Unspecified Not listed <1,600,000

Chetco River Fault, (Class A) No. 898

41.4 <0.00787 W N5°W 5.0 <130,000

Bald Mountain-Big Lagoon Fault Zone, (Class A) No. 787

44.7 <0.00787 E N27°W 59.0 <130,000

Grogan Fault, (Class A)

No. 11

45.0 <0.00787 65°-90° E, W N23°W 95.7 <1,600,000

Whaleshead Fault Zone, (Class A) No. 897

46.8 <0.00787 Unspecified N12°W 26.7 <130,000

2.4 SEISMIC DESIGN PARAMETERS

Recommended seismic response parameters for the Upper West Branch Bridge project site design are based on the American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications, 8th Edition, 2017, and represents horizontal peak ground acceleration (PGA) with 7 percent probability of exceedance in 75 years (approximate 1,000-year return period). The 1,000-year return period uniform hazard spectrum for the Upper West Branch Bridge project site, located at 41.93045°N latitude and 123.47825°W longitude, was obtained in accordance with the AASHTO ground motion maps.

Based on subsurface conditions encountered during drilling and the USGS Vs30 online map viewer, the onsite soils can be assumed to be reasonably dense. Therefore, the site is classified as Class C according to the site class definitions specified in Table 3.10.3.1-1 of AASHTO. The recommended spectral acceleration coefficient values for probabilistic design are summarized in Table 2.2.

Page | 5

Table 2.2 - Summary of Seismic Parameters Corrected for Site Class C Horizontal Peak Ground Acceleration, (PGA) 0.257 g

Horizontal Response Spectral Acceleration at Period of 0.2 sec, (Ss) 0.603 g Horizontal Response Spectral Acceleration at Period of 1.0 sec, (S1) 0.267 g

Site Factor at Zero-Period of Acceleration Spectrum, (Fpga) 1.2 Site Factor at Short-Period Range of Acceleration Spectrum, (Fa) 1.2 Site Factor at Long-Period Range of Acceleration Spectrum, (Fv) 1.5

Factored Horizontal Peak Ground Acceleration, (As) 0.294 g Factored Horizontal Response Spectral Acceleration at Period of 0.2 sec, (SDs) 0.698 g Factored Horizontal Response Spectral Acceleration at Period of 1.0 sec, (SD1) 0.409 g

Seismic Zone Zone 3

Based on the long acceleration coefficient SD1 value of 0.409, the project site is assigned to seismic hazard “Zone 3” in accordance with Table 3.10.6-1 of AASHTO. Seismic hazard zones reflect the variation in seismic risk in different regions needing different requirements for design as depicted in Table 4.7.4.3.1-1 of AASHTO.

2.5 GEOLOGIC HAZARDS

Potential geologic hazards at the bridge site include those related to earthquakes, mass movements, and mineral hazards. Earthquakes, as discussed in the previous section, could pose a threat to the Upper West Branch Bridge. Northern California and the project sites are located in an area of moderate to high potential for damaging earthquakes, although it is impossible to accurately predict the timing or location of future earthquakes. Liquefaction potential is relatively minimal since the site soils are relatively dense and unsaturated. Seismic hazards can be mitigated by appropriate design analysis as specified in AASHTO.

Mass movements are also common in California due to major wildfires, heavy rains, and the fines content of the soil. These rock and soil movements include seismically triggered landslides, debris flows, mud flows, and rock falls. The project is located in terrain susceptible to mass movement and these events could impact the bridge site. No specific investigation was conducted to evaluate slope stability in the project area. Mitigation of landslides is outside the scope of this emergency repair project.

Minerals-related hazards, such as asbestos, mercury, and radon, are present in northern California.

Serpentinite and ultramafic bedrock often contain naturally occurring asbestos (NOA), but not always. The Klamath National Forest has mapped areas more likely to contain NOA as shown in Plate 5. Asbestos materials were not identified during routine description and engineering classification of the site materials. No microscopy or other detailed testing was performed and, thus, a contingency plan for managing NOA encountered during construction should be considered. CFLHD does not take responsibility for development, implementation, or enforcement of any sort of management or abatement plan for NOA.

Page | 6

SECTION THREE - Subsurface Investigation

3.1 SUBSURFACE EXPLORATION PROGRAM

A subsurface investigation targeting the bridge site was performed by a Central Federal Lands Highway Division (CFLHD) of the Federal Highway Administration (FHWA) geotechnical engineer on June 10 through 11, 2021. The geotechnical subsurface exploration program consisted of drilling a total of two borings ranging from depths of approximately 32 and 37 feet deep. One boring was drilled near each bridge abutment. Hollow-stem augers were used to drill through the lower density overburden soils and NQ diamond core drilling was used to drill through denser soils and completely weathered rock and boulders. Standard penetration testing (SPT) and sample collection was performed at 5-foot intervals for each boring when possible. Core samples of boulders and completely weathered rock were also collected. Subsurface conditions were logged and representative samples were collected and transported to the CFLHD Materials Laboratory in Lakewood, CO, for physical property testing. Logs of the explorations and boring locations are presented in Appendix A and Plate 4, respectively. Photographs related to this exploration can be found in Appendix C. A summary of the field exploration is provided in Table 3.1.

Table 3.1 - Summary of Field Exploration Program

EXPLORATION

DESIGNATION LOCATION

APPROXIMATE

GROUND

ELEVATION (ft.)

APPROXIMATE

TERMINATION

DEPTH (ft.)

APPROXIMATE

DEPTH TO

GROUNDWATER

(ft.)

BH21-03 Abutment 1;

STA 2+30, 2 ft. RT 2,174.0 36.5 Not encountered.

BH21-04 Abutment 2;

STA 3+34, 10 ft. RT 2,175.0 31.5 23.0

Note: The exploration locations were estimated relative to existing features. Ground elevations were acquired from CFL survey data. Exploration designations BH21-01, BH21-02, BH21-05, and BH21-06 were used for the CA ERFO 17N11(1), Upper Doolittle & Mill Creek Bridges, project.

3.2 LABORATORY TESTING PROGRAM

Soil samples recovered from the borings by SPT were tested in the laboratory to support the field classifications and to provide an estimate of the engineering characteristics and mechanical properties of the soil. Laboratory tests included moisture content (AASHTO T255), sieve analysis (AASHTO T 11 and T27), classification (AASHTO M145), Atterberg limits (AASHTO T89 and T90), resistivity (AASHTO T 288), and soil pH (AASHTO T 289). When the necessary tests were completed, samples were classified using the Unified Soil Classification System (USCS) and AASHTO soil classification system. Results of the testing are summarized below in Table 3.2 and are presented in Appendix B.

Page | 7

Table 3.2 - Summaries of Laboratory Index Test Results

BORING

NUMBER

SAMPLE

DEPTH

PERCENT

GRAVEL

PERCENT

SAND

PERCENT

PASSING

#200

LIQUID

LIMIT

PLASTIC

LIMIT

USCS

CLASS.

AASHTO

CLASS.

(feet)

BH21-03 5 - 6.5 35 51 14 19 16 SM A-1-a(0)

BH21-03 10 - 15 32 55 13 18 16 SM A-1-b(0)

BH21-04 5 - 6.5 30 44 26 29 19 SC A-2-4(0)

BH21-04 10 - 15 37 47 16 21 17 SC-SM A-1-b(0) BH21-04 25 - 30 38 50 12 21 18 SM A-1-a(0)

Soil test results indicated a range of material types including silty sand, clayey sand, and silty, clayey sand classifying as A-1-a to A-2-4 by AASHTO and SM, SC, and SC-SM by USCS.

Corrosivity and chemistry testing of select samples were sent to an outside laboratory for testing and are summarized in Table 3.3.

Table 3.3 - Summaries of Laboratory Corrosivity Results

BORING

NUMBER

SAMPLE

DEPTH

RESISTIVITY PH

SULFATE ION

CONTENT

CHLORIDE ION

CONTENT

(feet) (ohm-cm) (ppm) (ppm)

BH21-03 10 - 15 - - 240 2

- Tests not completed.

Unconfined compressive strength (UCS) of boulder material was conducted on intact samples of boulder core recovered from the borings to characterize the highly variable subsurface drilling conditions. Results of the UCS testing are presented in Table 3.4.

Table 3.4 - Summary of Uniaxial Compressive Strength Results

BORING NUMBER SAMPLE DEPTH RQD1 LENGTH / DIAMETER2 UCS

(feet) (%) (psi)

BH21-03 18 25 2.4 25,140

1Rock Quality Designation for core run from which sample was taken in boulder, not bedrock surface.

2Values less than 2.0 do not meet the requirements of ASTM D 7012. Not included in analysis if encountered.

Page | 8

3.3 SUMMARY OF SITE CONDITIONS

This section presents the results of the surface reconnaissance and subsurface exploration.

3.3.1 General Topography

The general topography of the project sites is characterized by the steep and rugged Klamath Mountains that encompass northwestern California and southwestern Oregon. Boulders were observed of at least 6-foot diameter on the ground surface. Portions of boulders were buried;

therefore, the actual sizes may be greater than what was observed. Burnt, dead, standing trees typical of Douglas Fir intermingled with strands of old growth and scattered ponderosa pine, sugar pine, and incense cedar are abundant at the project site. Signs of revegetation are noticeable in the surrounding grass and shrubs. West Branch Indian Creek flows east, crosses Forest Route 18N31(1), and converges with Indian Creek approximately 0.5 miles downstream of the Upper West Branch Bridge project site.

3.3.2 Surface Reconnaissance

Superstructure timber elements were incinerated by the fires; however, the steel truss members of the Upper West Branch Bridge, although damaged beyond reuse, remain in place. Concrete abutments also remain and appeared to be in good condition. Gabion/MSE-type wingwalls with gabion-type channel protection and riprap at the north bridge abutment, built sometime in the 1990s according to the Forest Service, endured through the fires. The channel itself appeared to have migrated toward the south abutment over time and signs of erosion were observed at both corners of the south abutment. Scour did not appear to influence the north abutment, however, and the north abutment footing was exposed approximately 15 feet below the top of the abutment wall.

The forested area around the bridge site is severely burned. The significant loss of native vegetation has exposed the soil to erosion and increased water runoff. Regrowth of grass and small bushes has begun to take place; however, many exposed areas remain. Increased sediment transport was observed and is likely to continue until vegetation is well reestablished. Due to the weakened surface conditions and the steepness of the surrounding slopes, sediments, debris, loose rocks and boulders, and tree parts have the potential to slide downslope towards West Branch Indian Creek.

In general, however, any movements related to the slopes adjacent to the project sites appear to be surficial and slow moving.

The approaches leading to the bridge site are unpaved roads consisting of mainly reworked onsite gravel-like material. Alluvial soils and sediments encompass the bridge site. Large, rounded, boulders ranging in size from approximately 1.5 feet to 6 feet in diameter line the banks and were observed in the channels of West Branch Indian Creek. These boulders could have been placed around the previous bridge as scour protection and may have been locally sourced during the original construction. Rock outcroppings were not observed in the vicinity of the bridge location.

Page | 9

3.3.3 Subsurface Conditions

The subsurface conditions at the north abutment of the Upper West Branch Bridge were investigated by drilling boring BH21-03. Hollow stem auger drilling was used from approximately 0 to 16 feet below the ground surface and rock coring was used from approximately 16 feet below the ground surface to the termination depth of 36.5 feet. The ground surface surrounding the boring location consisted of silty sand and gravel alluvial soils. The boring encountered dense to very dense silty sand with gravel to the termination depth. This material was described as apparent decomposed metamorphic rock of the Galice Formation. Boulders were encountered within this soil matrix from approximately 16.5 to 36.5 feet. The boulders were observed to be up to approximately 3 feet in diameter or larger. Metamorphic textures such as foliation and schistosity were observed, however, the material could be easily crumbled by hand. Neither groundwater nor bedrock were encountered to the depths explored.

The subsurface conditions at the south abutment of the Upper West Branch Bridge were investigated by drilling boring BH21-04. Hollow stem auger drilling was used to the termination depth. The ground surface surrounding the boring location consisted of silty sand and gravel alluvial soils. The boring encountered dense clayey sand with gravel to a depth of approximately 11 feet. Rock fragments were encountered within this soil layer around 6 feet. This material was underlain by dense to very dense silty, clayey sand to a depth of approximately 20 feet. The material then transitioned to dense silty sand with gravel to the termination depth of 31.5 feet. This material was described as apparent decomposed metamorphic rock of the Galice Formation.

Groundwater was encountered at approximately 23 feet and bedrock was not encountered to the depths explored.

Boring logs created from an April 1966 investigation conducted by Clair A. Hill & Associates are included in Appendix E. The subsurface conditions presented on these logs have dissimilarities when compared to the June 2021 boring logs provided in Appendix A and the associated descriptions discussed above. Schist, for example, is shown in the 1966 boring logs and a distinct weathered schist zone was not identified in the 2021 investigation. Galice Formation-type geology, which includes schist and greenschist, was, however, encountered during the 2021 investigation and is discussed in this report. Another dissimilarity is the presence of stiff and hard clay in the 1966 boring logs, whereas clay was not encountered in the 2021 investigation. This may be because the 1966 investigation was conducted closer to the stream channel where clay materials are more likely to exist. The differences between these two sets of boring logs show highly variable conditions and a wide range of materials that could present significant challenges to construction.

Construction considerations related to these subsurface considerations will be discussed further in Section 4.4.

Page | 10

3.3.4 Groundwater

Groundwater was encountered during drilling in boring BH21-04 at approximately 23 feet below the ground surface. Groundwater was not encountered in boring BH21-03. However, fluctuations in the groundwater level due to seasonal and climatic effects are expected and will likely follow water levels in the adjacent creek.

Page | 11

SECTION FOUR - Analysis & Recommendations

This section presents analysis and recommendations for the bridge foundations, abutment wingwalls, permanent earthworks, and construction considerations for the design and construction of the Upper West Branch Bridge project. Based on discussions with the project team and the severe damage to all bridge structure components, the bridges will be replaced. Generalized subsurface profiles were developed based on field reconnaissance, surficial visual evaluation, and subsurface investigations.

4.1 FOUNDATIONS

The existing single span bridge will be replaced with a simple single-span structure. The existing bridge elements are mostly still in place except for the superstructure timber elements. Based on the 95 percent design plans, the proposed abutment centerline station and cap elevation are shown in Table 4.1.

Table 4.1 - Proposed Bridge Foundation Location

FOUNDATION APPROXIMATE STATION TOP OF SHAFT ELEVATION*

Abutment 1 2+41.00 2,168.72 FT Abutment 2 3+31.00 2,170.52 FT

*As presented on the 95% design plans.

4.1.1 Bridge Foundation Selection

A drilled shaft foundation system is proposed for the new abutments due to the high axial and lateral loads. Spread footers were considered but determined impractical due to additional materials to extend the bridge span beyond lateral scour potential, time, and cost that would be required for construction. A driven pile foundation was also considered but determined impractical due to the presence of cobbles and boulders that could cause pile damage during driving, as well as the limited space available and accessibility to the site being difficult for standard pile driving equipment.

A drilled shaft foundation is feasible from a geotechnical perspective. Drilled shafts are able to provide a small footprint, support large foundation loads, and provide lateral resistance at a shallower elevation than driven piles. Based solely on hydraulic recommendations and assumptions stated in the Final Hydraulics Report (September 2021), scour potential as measured from the thalweg was determined to be present at the bridge abutments. Based on available data, it was determined by the combined team of Bridge, Hydraulics, and Geotechnical Engineers that drilled shafts would provide the best foundation system for this bridge.

Page | 12

The following final bridge load factored for the strength limit state was provided by the CFL bridge engineer in early October 2021:

Both abutments = 250 kips (per shaft; ×3-24 inch shafts per abutment)

4.1.2 Site Characterization

The subsurface profile was assumed to be entirely sand for analysis purposes. Although gravel, silt, boulders, rock fragments, and completely weathered rock materials were encountered in the designated boreholes, the subsurface materials, in general, were of a sand-like nature and composition. Groundwater was also assumed to be at the channel thalweg elevation of 2,155.4 feet.

4.1.3 Drilled Shaft Axial Resistance

The drilled shaft axial resistance analysis was performed for 24, 30, and 36-inch diameter shafts at the abutments using the beta method for cohesionless soils presented in section 10.8.3.5.2b of AASHTO. The abutment foundations will obtain their resistance through side friction and tip resistance. The factored resistance for the strength limit state was calculated by applying 0.55 and

0.50 resistance factors for side and tip resistance, respectively.

4.1.4 Group Effects on Axial Resistance

The resistance of a shaft group to the applied axial loads is not necessarily the sum of the axial resistance of individual shafts within the group. The zone of influence from an individual shaft in a shaft group may intersect with other shafts, depending on the shaft spacing. Historically, the efficiency of groups of drilled shafts has not been a concern as long as the center-to-center spacing between shafts is greater than three times the shaft diameter (3D) to avoid interference between adjacent shafts, assuming a single row shaft group configuration. An efficiency factor (η) should be applied for spacing less than 3D as shown in Table 10.8.3.6.3-1.

Besides the effect of overlapping zones of influence, effects of construction on ground conditions in and around the group can be significant. Excavated deep foundation elements in cohesionless soils tend to decrease the effective stress of the surrounding soils. Poorly controlled shaft construction methods can result in soil loosening during drilling and adversely reduce the lateral stress around other shafts within the group. Casing driven in advance of excavation may increase the relative density and effective stress of the surrounding soil and prevents caving of overburden material.

4.1.5 Lateral Loads on Deep Foundations

Lateral load analysis was performed by the bridge engineer using the software program LPILE developed by Ensoft, Inc. This program analyzes a single pile or shaft considering deflection as a

Page | 13 function of design loads, foundation construction, and subsurface conditions. Table 4.2 provides LPILE input parameters for the foundation soils based on available subsurface information and presumptive engineering correlations. We recommend that lateral support above the scour elevation defined in the CFLHD Hydraulics Report be neglected due to potential loss of material during the design flood event. It is also recommended that lateral support within five feet of the final road grade be neglected due to the potential loss of support from frost penetration or other shallow ground disturbance.

TABLE 4.2 - LPILE Parameters

APPROXIMATE

ELEVATION

(ft)

DEPTH BELOW

TOP OF SHAFT

(ft)

P-Y

MODEL

EFFECTIVE

UNIT WEIGHT,

ɣ’ (pcf)

FRICTION

ANGLE, Փ

(deg)

HORIZONTAL

SUBGRADE

MODULUS, Ks

(pci)

UPPER WEST BRANCH BRIDGE

2,169 to 2,161 (Abutment 1) 2,171 to 2,160 (Abutment 2)

0 to 8 (Abutment 1)

0 to 11 (Abutment 2)

Sand (Reese)

127.0 38 90

2,161 to 2,156 (Abutment 1) 2,160 to 2,156 (Abutment 2)

8 to 13 (Abutment 1)

11 to 15 (Abutment 2)

Sand (Reese)

127.0 38 225

2,156 to 2,138 (Abutment 1) 2,156 to 2,144 (Abutment 2)

13 to 31 (Abutment 1)

15 to 27 (Abutment 2)

Sand (Reese)

64.6 38 125

Material properties provided are for single shafts and do not account for the reduced lateral resistance of shafts in a group. P-multipliers are a function of the number of rows of shafts and center-to-center shaft spacing in the direction of loading. P-multipliers are required even for a single row of shafts if the center-to-center spacing is less than 5 shaft diameters. P-multipliers are specified in Table 10.7.2.4-1 in AASHTO. When this analysis method is used, the resistances at the strength limit state as represented by the P-y curves should not be factored since they already represent the nominal conditions.

4.1.6 Settlement

A resistance factor of 1.0 for the service limit state is recommended to assess the ability of the foundation to meet the specified deflection criteria. Elastic settlements will occur immediately and be essentially complete at the end of construction and are estimated to be less than one inch at all locations based on the loads provided. Differential settlements are not anticipated. Shaft group settlement is not anticipated.

Page | 14

4.1.7 Recommended Shaft Lengths

The final lengths of the drilled shafts are based on both axial and lateral loading. Table 4.3 below shows the required shaft lengths needed for both axial and lateral capacities. This is based on the selected shaft diameter of 24 inches. The axial capacities needed to meet loading requirements were determined to control the design shaft tip elevations for the Upper West Branch Bridge.

Table 4.3 - Shaft Lengths Required for Axial and Lateral Loading

STRUCTURE

ELEMENT

REQUIRED SHAFT LENGTH

FOR AXIAL CAPACITY

(feet)

REQUIRED SHAFT LENGTH

FOR LATERAL CAPACITY

ESTIMATED TIP

ELEVATION

Abutment 1 35 32 2,133 Abutment 2 45 40 2,125

4.1.8 Field Testing

Steel crosshole sonic logging tubes (1.5-inch diameter steel tubes) should be installed in all drilled shafts prior to concrete placement for integrity testing. The recommended number of access tubes and tube spacing are dependent on the selected shaft diameter, typically one access tube per 12-inches of shaft diameter, with a minimum of three access tubes per shaft. The crosshole sonic logging tests should be conducted in accordance with ASTM D-6760 and FP-14 for quality assurance/quality control of the drilled shafts.

4.1.9 Scour Potential and Erosion

Contraction scour and local abutment scour depths were estimated by the hydraulics engineer.

Section 4.4.3 in the Final Hydraulic Report details the scour depth estimates.

Provision of scour countermeasures and bank protection can be used to mitigate scour effects and reduce maintenance. For additional scour and countermeasure information please refer to the previously mentioned Final Hydraulic Report dated September 2021.

4.2 ABUTMENT & WINGWALL DESIGN

Abutments and wingwalls should be designed to resist lateral earth pressures and other applicable lateral loads in accordance with AASHTO. Lateral earth pressure is influenced by the strength of the abutment backfill, the presence or absence of water, and the ability of the abutment or wall to move in response to lateral loads. Other loads, such as live loads, construction loads, and soil compaction loads should also be considered in the design.

Unbalanced water behind an abutment or wall adds significant lateral pressure and should be avoided by using free draining gravity outlets for water. Abutment and wingwall backfill should consist of structural backfill as specified in Section 704.04 of FP-14.

Page | 15

The coefficient of at-rest earth pressure should be used for design if the abutment is so restrained that it cannot be expected to rotate (deflect at the top) 0.002 times the wall height. Where deflection of the abutment can be expected, a coefficient of active earth pressure should be used for wall design. Active and at-rest lateral earth pressures of native materials and properly placed and compacted structural backfill above the water table are presented in Table 4.4. The values are unfactored loads and assume that the surface of the soil slope behind the wall is horizontal.

Table 4.4 - Lateral Earth Pressures for Bridge Abutments & Wingwalls

BACKFILL TYPE

ASSUMED

BACKFILL

PROPERTIES

CASE

UNFACTORED

EQUIVALENT

FLUID DENSITY

(PCF)

NOMINAL

FRICTION

FACTOR

Structural Backfill c = 0 psf φ = 34 deg.

γ = 125 pcf

Active 35 0.67

At-Rest 55 0.67

Native Soil c = 0 psf φ = 38 deg γ = 127 pcf

Active 30 0.78

At-Rest 49 0.78

4.3 PERMANENT EARTHWORKS

4.3.1 Embankment Construction

Embankment construction will be necessary with regards to the concrete wingwalls. Construct permanent long-term embankments with a maximum slope ratio of 1V:2H to maintain slope stability and promote slope vegetation.

4.3.2 Shrink/Swell Recommendations

On-site soils expected to be encountered within the project limits generally consist of silty and clayey sands with varying amounts of gravel. It is estimated that these soils will have a 10 percent shrink percentage, corresponding to a shrink/swell factor of 0.90. The recommended shrink/swell factor is based on a combination of standard tabled values for common materials in the FLH Technical Guidance Manual (2006) and experience with other CFLHD projects in similar materials.

4.4 CONSTRUCTION CONSIDERATIONS

Roadway Excavation: Excavate using equipment capable of removing the material while preventing material from escaping outside the construction limits.

Based on the subsurface investigation and surface geologic mapping, the rock encountered, primarily boulder material of the Galice Formation, is expected to be rippable in the areas

Page | 16 surrounding the abutments of the Upper West Branch Bridge; however, final determination of rock rippability is the responsibility of the contractor. Shear wave velocity of the geologic layers was not evaluated by geophysical methods. However, based on Table D.1 in Appendix D, the boulders encountered can be presumed to be within the extremely hard rock description. Additional information regarding the excavation characteristics of rock and rippability charts can also be found in Appendix D.

Evidence of definitive in-place bedrock was not encountered from the subsurface investigation detailed in this report. However, appropriate construction equipment should be mobilized to the site based on the rock information detailed above. The handling of boulders of at least 6 feet in diameter will be required for excavations in the project area. The contractor is responsible for the safety of excavations, blasting, and shoring design.

Drilled Shafts: The contractor will be required to submit a drilled shaft construction plan as required in Section 565.04 of the FP-14 which includes the outlining of proposed methods to maintain borehole stability, manage the excavation of boulders, concrete placement, and dewatering.

Galice Formation-type boulders were encountered at boring BH21-03. Be prepared for cobbles and boulders ranging in size from approximately 12 to 60 inches and larger.

It is anticipated that groundwater will be encountered at the foundation excavations. The likelihood of flowing sands could also present a challenge for the driller as the mixture of fine sand and water could infiltrate the drilling equipment. The contractor should be prepared for wet construction methods as groundwater can infiltrate even when temporary casing is used.

Existing bridge foundation elements, including vertical concrete abutment walls on spread footings supported on steel piles and the existing MSE/gabion wall and revet mattress near abutment 1, are to remain in place. The MSE/gabion wall is supporting embankment material at abutment 1 and existing plans for the wall do not exist. Therefore, it is recommended to core through these elements and case the drilled shaft full depth before proceeding with shaft installation. Monitoring of the MSE/gabion wall is expected to be performed by the contractor during shaft drilling. An action plan should be established by the contractor if displacement of the wall is observed.

Corrosivity: Based on guidelines outlined in subsection 704.08(b) of FP-14, a pH below 5 or above 10, a resistivity below 3,000 ohm-cm, and sulfate and chloride concentrations above 200 and 100 parts per million, respectively, are representative of an aggressive soil environment. The sample tested at boring BH21-03 from 10-15 feet resulted in a sulfate content of 240 ppm. This test result is not within the guidelines defined in subsection 704.08(b) of FP-14 and represents a moderate potential for sulfate attack to concrete exposed to on-site soils. All concrete that will be in contact with the on-site soils should be formulated with a sulfate resistant cement.

Page | 17

Dewatering: Dewatering may be needed due to water infiltration from the river. Perform dewatering according to Section 208.07 of the FP-14.

Slope Instability: Slopes could become unstable during construction operations due to precipitation, flooding events, or heavy loading on soft subgrade soils. Precautions should be taken if movement or cracking is observed. Seepage is a contributor to slope instability and similar dewatering and stabilization methods could be used to suspend slope movement. The contractor is responsible for temporary working platforms including those needed for cranes and shaft drilling rigs.

Hard Layers: Hard layers, such as boulders, were encountered during the geotechnical investigation. The Contractor should be prepared with appropriate equipment based on the local geology as discussed in Sections 2.1 and 2.2, and Appendix D (Rippability).

4.5 SPECIFICATIONS

Special provisions were provided prior to the 95% design milestone to be consistent with geotechnical recommendations stated above and were incorporated into the special contract requirements (SCR) to amend the FHWA Standard Specification for Construction of Roads and Bridges on Federal Highway Projects; known as FP-14.

4.6 DISCLAIMER/LIMITATIONS CLAUSE

The recommendations in this report are based on the data obtained from exploratory borings, field review, and laboratory test results. The results of these explorations and tests represent conditions at the specific locations indicated. Subsurface variations across the site are likely and may not become evident until excavation is performed. The Analysis and Recommendations sections in this report include interpretations and recommendations developed by the Government in the process of preparing the design. These interpretations are not intended as a substitute for the personal investigation, independent interpretation, and judgment of the Contractor.

Page | 18

SECTION FIVE - References

American Association of State Highway and Transportation Officials (AASHTO), 2017, LFRD Bridge Design Specifications, 8th Edition.

Brown, Dan A., Turner, John P., and Castelli, Raymond J., 2010, “Drilled Shafts: Construction Procedures and LRFD Design Methods,” NHI Course No. 132014, Geotechnical Engineering Circular No. 10, Report No. FHWA NHI-10-016, dated May.

Federal Highway Administration (FHWA), 2007, Geotechnical Technical Guidance Manual, dated May.

Federal Highway Administration (FHWA), 2008, Federal Lands Highway Project Development and Design Manual (PDDM), dated March.

Federal Highway Administration (FHWA), 2014, Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects FP-14.

Federal Highway Administration (FHWA), 2017, Soil Description and Identification Guidelines, dated December.

Federal Highway Administration (FHWA), 2017, Rock Characterization Guidelines, dated December.

Federal Highway Administration (FHWA), 2021, “CA ERFO 18N31(1) Upper West Branch Bridge Final Hydraulics Report,” dated September.

Hawthorne Cat, 2018, “Caterpillar Performance Handbook,” Edition 48, dated June.

Isenhower, William M., Wang, Shin-Tower, and Vasquez, Gonzalo L., 2016, “Technical Manual for LPile 2016 (Using Data Format Version 9),” Ensoft, Inc., dated January.

National Park Service (NPS), 2020, “Series: Physiographic Provinces, Pacific Border Province,” updated May 7, <https://www.nps.gov/articles/pacificborderprovince.htm>.

State of California (CA.gov), 2019, “Geologic Hazards,”

< https://www.conservation.ca.gov/cgs/geohazards>, Accessed March 3, 2021.

State of California (CA.gov), 2020, Caltrans ARS Online (v3.0.2), <https://arsonline.dot.ca.gov/index.php?>, Accessed September 16, 2021.

The University of Texas at Austin Jackson School of Geosciences (Texas Geosciences), 2021, “Some Useful Numbers on the Engineering Properties of Materials (Geologic and Otherwise),” GEOL 615, <https://www.jsg.utexas.edu/tyzhu/files/Some-Useful- Numbers.pdf>, Accessed February 18.

U.S. Department of Agriculture (USDA), 2012, “National Engineering Handbook (NEH), Part 631 Geology,” Chapter 4: Engineering Classification of Rock Materials, dated January.

Page | 19

U.S. Geological Survey (USGS), 2020(a), “Quaternary Fault and Fold Database of the United States,” Interactive fault map & database search, USGS Earthquake Hazards Program, <https://www.usgs.gov/natural-hazards/earthquake-hazards/faults?qt-science_support_page_related_con=4#qt-science_support_page_related_con>.

U.S. Geological Survey (USGS), 2020(b), “Vs30 Map Viewer,” online map, USGS Earthquake Hazards Program, <https://earthquake.usgs.gov/data/vs30/>.

U.S. Geologic Survey (USGS), 2020(c), “U.S. Seismic Design Maps,” USGS Earthquake Hazards Program, <http://earthquake.usgs.gov/designmaps/us/application.php> & <https://earthquake.usgs.gov/ws/designmaps/aashto-2009.json?latitude=34&longitude=- 118&siteClass=C&title=Example>.

Wagner, D.L., and Saucedo, G.J., 1987, “Geologic Map of the Weed Quadrangle, California”:

California Division of Mines and Geology, Regional Geologic Map 4A, scale 1:250,000.

Weaver, J.M., (1975), “Geologic Factors Significant in the Assessment of Rippability,” The Civil Engineer in South Africa (Die siviele ilngenieur in Suid-Afrika), Volume 17, Issue 12, pgs. 313-316.

PLATES

PROJECT VICINITY MAP,

GEOLOGY MAP & LEGEND,

GEOTECHNICAL BORING LOCATIONS MAP, AND

AREAS MORE LIKELY TO CONTAIN NATURALLY

OCCURRING ASBESTOS

STATE PROJECT

CENTRAL FEDERAL LANDS HIGHWAY DIVISION

FEDERAL HIGHWAY ADMINISTRATION

U.S. DEPARTMENT OF TRANSPORTATION

NOT TO SCALE

PLATE

PROJECT VICINITY MAP

CA

UPPER WEST BRANCH BRIDGE

CA ERFO KLAMATH NF 18N31(1)

Upper West Branch Bridge

Eureka

SAN

FRANCISCO

LOS

ANGELES

San

Diego

Sacramento

OREGON

N

EV

A D

A

ARIZONA

MEXICO

Redding

KEY MAP OF CALIFORNIA

INTERSTATE

INTERSTATE

INTERSTATE

INTERSTATE

INTERSTATE

INTERSTATE

INTERSTATE

(41.930451º, -123.478250º)

Wagner, D.L., and Saucedo G.l., 1987, "Geologic Map of the Weed Quadrangle, California":

Claifornia Divisoud of Mines and Geology, Regional Geologic Map 4A, scale 1:250,000.

STATE

CA

NOTTO SCALE

PROJECT

CA ERFO KLAMATH NF 18N31(1)

UPPER WEST BRANCH BRIDGE

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

CENTRAL FEDERAL LANDS HIGHWAY DIVISION

GEOLOGY MAP

PLATE

u i5 N z

Oo u�

C, sl

JOSE-l'Hl�E Ol'IIIOllTE.

(lnd1tdcsother rocks of opbtol111cuffini1})

KLAMATH MOUNT Al 'S PROVINCE

D D

J\LLU\'IUM �- .. ---""""""'

o., ... _,. .. ,.

GJ GL.>.Cb;�?-k'IJ,,E.

(lo<l•koJlo<Mll--)

LAr-DSLID( DEl'OSll'S C-•., .,_ •ha< pstabol<. ,1.,._�<)

11:1\TIAI\Y fA01\lrtl\O!J5) (jl\A\'fl � ...... -.� .,._i,...., ..... ,-...

B 11,1,1111 m11.\tAllOi' h...tk1•/l;Ja.,1,.,_.,..i....i"°""·

GJ

IIOtl.,._1.-00K r-ORMJ\TIOS

-.... �--.... ·--� ... -.i..i. • ....i�,-,c.�,.

-·- """'')-,-1...u)....i�

WESTERN PALEOZOIC AND TRIASSIC BELT (M�P-£)

Ana,�mblag� I',( ll,\-tr!.c (O<.'l ry�. M�tly M�w:ic,:ilthoLgh l'alteuo1c fossil� h!11'e btcr, found 1n rhen 11nd b,\ w,h nf limKlm1e �hn11.n ao;; M�I', unJ�.,. tnh:h111deo:1 a, fol lo..,� nfl NOKTH fOK .... IERRANEuflr\.11'1 Cl972)- Dilm.,,,ibrro.lupl11oh1e-.crp,:11• tin,le • .,:iM,ro, diaOO<e, m�fic vobm1c rock�, chtn ;md lime1tor11::

Wl!S"I t:.KN JUKA:,:,11.,.; UELT hfl llAYFORK TEltN.A\IE of l""'in (1'17!)-!l�)forli 1nclr,..Mr,(\r-;i1t', nrgrllilc.

chcn-arilltl1c on:,.:cl•

OALICE FORMATION

Sllllc. mcta1n�11,ae-l.e, some nu�?>1�e Ut:elbtor.e ri:1 RATTI F',NAKF C'RFF.K TFRRANF. «' lr',lin (1'7?) D1,rupted. mildly !'l'IC!Amorphooed u$Cffll;,lage ef -0pllioli1ic rock<; se�minit�. gabbro, m.afic �oJ.::unc rock5, ctlngk:nncrale. SiH'llhlonc. ard hm,::,1,.me

VOLCANIC ROCKS

Pillow la�a, dikes. bre<:<:11�

GABBRO, DIORITE, AND RELATED ROCKS.

ULTRAMAFIC ROCKS

funia.11) 10 romplclcly scrpcn1i1:iitU pcnWtitc; loi:..illy include, m11fic: rock1

Llthol,;,gie,$ Qf lhe l>d1 an dcnou:d as fo1kiw5:

ms - me1:uedimenury roch. ltrgillitt, r,hyllile. conglorner:atc, brere1•. rlrrt. ,;omr volcaniclasticrocks.

mv - metavolcamc rocks, m:1.fic to mtcE"mcd1ate flows, tufl5. Jf«ClU rn..-.-volcaniclastOC:se.dimcnls,milloedmdav<>l.,micandrn.,[a.edirr..:nt:..I')' (,i,d,;5, SC� - amphit>alitc WKl gn:cn.chi�I.

ch -chc,-1 q� -co!1glomcrarc,nd icdllllCntary brcccin.

ls hrnestonc and mart>l� gb . gabbro, diabase and related r-o,.h, um . pcliclolitc, serpcmi�ilc and mcll!Sapclllinilc.

bo - blll-,1\i<t ( ♦ -blu,es..,hist blods)

Jom

ULTRAMAflC

CABBR.OIC ROCKS

PI.UTONIC ROCKS

GRANITIC ROCKS

Cn1ni1c1<>grnm,dinrile

DIOR.ITIC ROCKS

Tom1li1e !,o di,rite;i'IOme ,abbn:i.

FASTFRN IC LA MATH Hl-<J r

GJ

POTEM FORNATION

Arsll11� and tuff11Ctt>W ..,.,do;tcne

..,. Ot\GL[Y ANDE.SITE

ARVISON rOR!v-lATION Yl1ltan1Cb!t1C 1111d p)rGCIIISIIC: rod6, n,1nor ande<ilie nu,., CONDREY MOUr-.'TAIN SCHIST

Cinphllic sch1'>1, grcc11.;ch1S1, some blue,;ch1�1, il&e on«rla111

MODrN FORMATION An.daitit 11obnda,11C. ud pYrn::.lut� mck.._ r::7 PITFORMATIO\I � O:t.rl. shale. silbtJne, meumk:tnic ro:ks, 111inor l1mQlon; (im:lud� Ur1Kk Slu1li,: •1111 lh,"-sc:lku3 Li�Co;mel-

Mz�I----------------� OOLLIIIDKKA GROUP (Oekkasand NMJH Form.at ions. UildtfTcrentiatcd); Andcsuc, mu1btooe, arid tutl

STUART FORK FORMA.TIO�

l'hylllt IC quanznc "1th bh.ocllist 1ml McCLOl.lD LIMESTONE p,.

CENTRAL META MORfHIC BELT (Dcro11i111 or older) ru

HAll<O FORMATION l"yf1Xhl5tii,: ro:h kentophyrc, minor xdimcntllf)' ,ocb

DRAODON FORMATION

Graywacke, �1,ak. an<! minor conglllmfft'ltt

KENNETT FORMATION

Silkwu.:. Slalc, rlyvlilis: 1urr, h = �,,-,1.,1�,..., Li,nc,tone.

COPLEY GREENSTONE

GAZELLE: FORMATION

SandstQne. shalt, cllert. conglomerate. hmtslone, and green11one. Pan d 1hi� u11i1 may be rtll:'l.tn�.

MOFFE.T CREEK FORMATION

Shcarod unchlOlle and sh11I<: (mebnge1)

ARRA MS MICA SCHIST ___________ r:::"7 (Grt11N:RIUgcfunnatioon). �

DUZEL FORl,tATION Phylli,,:, graywad,:c,cben, silts1<J•••· q .. art:t.,te. �m<5\0lle, and m:uhle [lnch.rlcs 1he follo,..,.ng 11ni1sof P-0t1cr& mh� ( 19TT ): Lanw;tone of Du lei Roel, Ouzel Phyllitc. Schu.Jmei-cr Gulch ..equcncc, Sis"'-'! G11kh Gra)"wad.e. Grecn,.;;l,5t of Skoal.um Gulch Parts d the Ouzcl Fonnauon have be.at, c<>•r•l�,od ..,;,1,, th� Cuu ... l Menmorph;e Wit b)I C,.,hman (!!)80)]

SALMON HORNBLENDE SCKIST

MAFI C VOLCANIC KOCK.S AND DIABASE. tOvl

GABBROIC AND DIOR.JTIC R.OCKS. (lndudes minor pJro�""itel --�::...Ji-• TRINlTI' PERIDOTITE. l'anillll) !oerpcrmrnza:t paiclooite. (Op)

IOgh)

Wagner, D.L., and Saucedo G.J., 1987, "Geologic Map of the Weed Quadrangle, California":

California Divisoud of Mines and Geology, Regional Geologic Map 4A, Scale 1 :250,000

STATE

CA

PROJECT

CA ERFO KLAMATH NF 18N31(1)

UPPER WEST BRANCH BRIDGE

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

CENTRAL FEDERAL LANDS HIGHWAY DIVISION

GEOLOGY MAP

LEGEND

PLATE

NOT TO SCALE

Boring Locations

Boring Location Latitude

BH21-03 North Abutment 41.9305866

BH21-04 South Abutment 41.9303367

Longitude

-123.4782277

-123.4783018

Google Maps, 2021. Upper West Branch Bridge. Google Maps [online]. Accessed 14 April 2021.

Elevation

2,174

2,175

Boring locations are approximate. Surface elevations acquired from CFL survey data.

STATE

CA

PROJECT

CA ERFO KLAMATH NF 18N31(1J

UPPER WEST BRANCH BRIDGE

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

CENTRAL FEDERAL LANDS HIGHWAY DIVISION

PLATE

UPPER WEST BRANCH BRIDGE

GEOTECHNICAL BORING

LOCATIONS

Areas :tv1ore likelv to Contain aturally Occurrin,g Asbestos

D..!.TA '.S0

LEGEND

.� b.{mre ' •BJ,' ID c,o:n:t:mi N:;,mrafil,y Oocuriing .'isbesto,;

Kllmsm N:.tionru Fonst

.�\,"e Rnm.'d.ty

1Qi

Mile.s .,, � "

11�:i.nl� · ¥1,;::cti ol}wn::d d1n:d!J, lrm1 l_7.5G!j Mmccil.

Doti S,;""'' {MRDS};;a. l�/1 . no.,...�- _ '"""' -mt tiib1o,al,rcm1 l!ifiL�A ��� ""'I"'""' l,ml,u<I. GIS J..i,« i,- � '"i f.;,,1hd",>U,:, : uooq:c•f f(m.11111.; h=" A:ut ·iit;.t �:.-a:a:, � -.au .� 1 �c:n1irr.1c, - '111:i'la US£:i$ . . · -El11JFal,l(rih!: -a::u, ':I 1-.i::: rinf::it

DL'lCL!\l…