3.3_-_Murray_Street_Bridge_Final_Retaining_Wall_FR-Pile_Supported.pdf

FINAL FOUNDATION REPORT FOR EARTH

RETAINING SYSTEMS

Murray Street Bridge

Seismic Retrofit and Barrier Replacement Retaining Wall No. 11, 17 & 18 Crawford File No. 2009-0272-3

Bridge No. 36C0108

Prepared by:

Crawford & Associates, Inc.

4701 Freeport Boulevard Sacramento, CA 95822

September 20, 2023

Prepared for:

TRC

10680 White Rock Road, Suite 100 Rancho Cordova, CA 95670-6061

Corporate Office: 4701 Freeport Boulevard | Sacramento, CA 95822 Modesto: 1405 8th Street | Modesto, CA 95354 Pleasanton: 6200 Stoneridge Mall Road, Suite 330 | Pleasanton, CA 94588 Seattle: 1448 NW Market Street, Suite 500 | Seattle, WA 98107 Ukiah: 100 North Pine Street | Ukiah, CA 95482| (707) 240-4400

September 20, 2023 Crawford File No. 2009-0272-3

Cameron Pinkerton, PE

TRC

10680 White Rock Road, Suite 100 Rancho Cordova, CA 95670-6061

Subject: FINAL FOUNDATION REPORT FOR EARTH RETAINING SYSTEM

Retaining Wall No. 11, 17, & 18 Murray Street Bridge Seismic Retrofit and Barrier Replacement City of Santa Cruz, California

Dear Mr. Pinkerton, Crawford & Associates, Inc. (Crawford) prepared this Final Foundation Report for Earth Retaining Systems (ERS) associated with the Murray Street Bridge Seismic Retrofit and Barrier Replacement Project in the City of Santa Cruz, California. Crawford prepared this report in accordance with our agreements between TRC and Crawford (previously Taber Consultants).

This report contains the results of our subsurface exploration and conclusions and recommendations for the design of the proposed Retaining Walls No. 11, 17 & 18 (RW-11, RW- 17, & RW-18). Foundation recommendations for the new bridge foundations, approach roadway, and Retaining Wall No. 9 are reported under a separate cover. This report updates and supersedes our Draft Foundation Report for ERS, dated October 12, 2021.

Thank you for the opportunity to be part of your design team. Should questions arise concerning foundation conditions at the site, please do not hesitate to call on us.

Sincerely, Crawford & Associates, Inc., Reviewed by:

Keiko Lewis, PE W. Eric Nichols, PE, CEG Senior Engineer Principal

FINAL FOUNDATION REPORT FOR ERS Crawford File: 2009-0272-3 Retaining Wall No. 11, 17 and 18 September 20, 2023 Murray Street Bridge Seismic Retrofit and Barrier Replacement City of Santa Cruz, California

TABLE OF CONTENTS

1 INTRODUCTION

1.1 PURPOSE

1.2 GEOTECHNICAL SERVICES

2 PROJECT DESCRIPTION

3 GEOTECHNICAL INVESTIGATION

3.1 1997 EXPLORATION

3.2 2013 EXPLORATION

3.3 2015 EXPLORATION

3.4 DRILLING AND SAMPLING – TABER CONSULTANTS

3.5 LOGGING

3.6 SAMPLER PENETRATION RESISTANCE (N-VALUE)

3.7 BOREHOLE ABANDONMENT

3.8 BORING LOCATIONS AND ELEVATIONS

4 LABORATORY TESTING PROGRAM

5 GEOTECHNICAL CONDITIONS

5.1 SITE GEOLOGY

5.2 SURFACE CONDITIONS

5.3 SUBSURFACE CONDITIONS

5.3.1 SEDIMENTARY ROCK (SANDSTONE)

5.3.2 LAGOON DEPOSITS

5.3.3 FILL/SURFICIAL NATIVE MATERIALS

6 GROUNDWATER

7 AS-BUILT FOUNDATION DATA

8 SCOUR DATA

9 CORROSION EVALUATION

10 SEISMIC DESIGN INFORMATION AND RECOMMENDATIONS

10.1 GROUND MOTION

10.1.1 RECOMMENDED SEISMIC DATA

10.2 OTHER SEISMIC HAZARDS

10.2.1 SURFACE FAULT RUPTURE

10.2.2 LIQUEFACTION POTENTIAL

10.2.3 SEISMICALLY INDUCED SETTLEMENT

10.2.4 SEISMIC SLOPE INSTABILITY

10.2.5 TSUNAMI

11 GEOTECHNICAL RECOMMENDATIONS

11.1 RETAINING WALL FOUNDATION DATA AND LOADING

11.2 RETAINING WALL DESIGN RECOMMENDATIONS

11.3 PILE DATA TABLE

11.4 24” CISS PILES

11.4.1 COMPRESSIVE (AXIAL) RESISTANCE

11.4.2 TENSION (UPLIFT) RESISTANCE

11.4.3 LATERAL RESISTANCE

11.4.4 PILE GROUP REDUCTION

11.4.5 NEGATIVE SKIN FRICTION

11.4.6 SETTLEMENT

11.5 LATERAL EARTH PRESSURES

11.5.1 STATIC LATERAL EARTH PRESSURES

11.5.2 SEISMIC LATERAL EARTH PRESSURES

11.5.3 SURCHARGE LOADS

12 NOTES FOR SPECIFICATIONS

12.1 GENERAL CONDITIONS

12.2 CONSTRUCTION SEQUENCE

12.3 EXISTING FACILITIES

12.4 DRIVEN PILES

12.4.1 CISS PILE INSTALLATION

12.4.2 PILE DRIVING CRITERIA

12.4.3 PILE DRIVING SEQUENCE

12.4.4 DRILLING TO ASSIST PILE DRIVING

12.5 VIBRATION AND NOISE MONITORING

13 NOTES FOR CONSTRUCTION

13.1 EXCAVATION AND SHORING

13.2 DEWATERING

13.3 SEA WALL

14 RISK MANAGEMENT

15 LIMITATIONS

LIST OF TABLES

Table 1: Proposed Retaining Wall 11 Information Table 2: Proposed Retaining Wall 17 Information Table 3: Proposed Retaining Wall 18 Information Table 4: Subsurface Exploration Summary Table 5: Retaining Wall No. 11 Approximate Rock Surface Encountered Table 6: Retaining Wall No. 17 and 18 Approximate Rock Surface Encountered Table 7: Summary of Groundwater Data Table 8: Correlated Shear Wave Velocity Table 9: Potentially Liquefiable Soil Zones/Layers Table 10: Soft and Very Soft Clay Zones/Layers Table 11: Estimated Rock Elevations Table 12: Retaining Wall Foundation Design Data Table 13: Retaining Wall Foundation Design Loads Table 14: Retaining Wall Foundation Design Loads Table 15: Retaining Wall Pile Data Table Table 16: Recommended EFW – Structure Backfill as Retained Fill Table 17: Surcharge Loads

APPENDIX I - FIGURES

Figure 1: Vicinity Map Figure 2: Location of Field Tests Figure 3: Geologic Map Figure 4: Fault Activity Map

APPENDIX II

Log of Test Borings (LOTB) – Retaining Walls 11, 17 and 18

APPENDIX III

Laboratory Test Results

APPENDIX IV

Liquefaction Analysis Idealized Geotechnical Parameters Foundation Design Calculations

1 INTRODUCTION

1.1 PURPOSE

Crawford & Associates, Inc. (Crawford) prepared this Final Foundation Report for the Earth Retaining Systems (ERS) associated with the Murray Street Bridge Seismic Retrofit and Barrier Replacement project located in City of Santa Cruz, California. Services for this project were completed in accordance with our agreements between TRC and Crawford (previously Taber Consultants) and agreement dated July 12, 2021 between Crawford and TRC. This report presents the results of our subsurface exploration and testing, engineering analysis, conclusions and recommendations for use in design and construction of the proposed Retaining Walls No.

11, 17, and 18 (RW-11, RW-17 and RW-18).

This report updates and supersedes our Draft Foundation Report for ERS, dated October 12, 2023. Information and comments on that study are incorporated herein, as appropriate.

Geotechnical design recommendations for proposed new bridge foundations, approach roadway, and Retaining Wall No. 9 (RW-9) are reported under separate covers.

1.2 GEOTECHNICAL SERVICES

To prepare this report, Crawford:

• Discussed the project with the design team from TRC;

• Reviewed in-house file data regarding this project/site that included:

• Preliminary Foundation Investigation – Seismic Retrofit, dated May 5, 1999 (Taber Consultants Job Number 1R2/396/66.5);

• Preliminary Design Report – Draft, dated November 19, 2010 (Taber Consultants Job Number 2009-0272-1);

• Foundation Report – Draft, dated January 13, 2016 (Taber Consultants Job Number 2009-0272-1);

• Reviewed published geologic, seismic, and tsunami maps and literature pertaining to the project site;

• Subcontracted StrongMotions, Inc. to complete a report of Site-Specific Seismic Response Spectrum of Free-Surface Horizontal Motion for Murray Avenue Bridge (Report Number: SMI-12-2010), dated August 30, 2010;

• Completed geotechnical test borings at the site between March 23 through 29, 2013 and February 9 through 13, 2015;

• Completed laboratory testing on soil/rock samples obtained during subsurface explorations;

• Reviewed the following final retaining wall plans (100% submittal) for Murray Street Bridge Seismic Retrofit and Barrier Replacement prepared by TRC, dated 4-21-23:

o Retaining Wall No. 11 Layout and Details;

o Retaining Wall No. 17 Layout and Details;

o Retaining Wall No. 18 Layout and Details;

o Retaining Wall Type A Details;

o Retaining Wall Type B Details;

o Retaining Wall Type C Details; and

• Performed geotechnical engineering evaluation and analysis.

Limitations of this study are discussed in the final section of this report.

2 PROJECT DESCRIPTION

The project site is located at Murray Street where it crosses Woods Lagoon in the City of Santa Cruz, California. The site coordinates at the center of the bridge are approximately latitude 36.9680° N and longitude 122.0031° W. The site location is shown on Figure 1 in Appendix I.

The elevations for the test borings completed in 1997 (B-1 through B-7) are based on as-built information from 1963. According to TRC, the current project datum for vertical control is the National Geodetic Vertical Datum of 1929 (NGVD 29), where NGVD 29 = 1997 – 3.0 feet (e.g., Elev. 5.6 ft 1997 = Elev. 26 ft NGVD 29). Unless otherwise noted, elevations presented in this report are with respect to NGVD 29.

The project involves retrofitting the existing structure, including: widening the bridge on both sides, adding piles for structure support, widening/lengthening of supports at all abutment and bent locations, and constructing a curtain wall at Bent-9. This report addresses the three following pile supported retaining walls: RW-11, RW-17, and RW-18. Roadway embankments and grading outside of the proposed pile supported retaining wall limits are reported under a separate cover. A description of RW-11, RW-17, and RW-18 as shown on the 100% Submittal Plans is as follows.

Retaining Wall No. 11 extends east from RW-9 and will be part of the new stair design at the west end of the bridge. The plans show a Type A retaining wall supported on two rows of 24-inch diameter Cast-In-Steel-Shell (CISS) piles. We summarize the proposed RW-11 details in Table 1.

Table 1: Proposed Retaining Wall 11 Information

RW

No.

Lay Out Line (ft)

M-Line

Segment Wall Type

Length1

(ft) Design Height

(ft)

Bottom of Pile

Footing Elevation

(ft)

Station (ft)

Offset (ft)

RW 11

10+00.00 (Begin Wall) 10+97.71 25.56 Right

1 A 18.0 10.0 18.5

2 A 12.0 14.0 15.5

10+60.00 (End Wall) 11+51.0 50.54 Right

3 A 12.0 14.0 12.5

4 A 18.0 14.0 6.0

1) Measured along Retaining Wall Lay Out Line. Total length of RW 11 measured along LOL = 60.0 ft.

Retaining Wall No. 17 and 18 are located east of Woods Lagoon and south of Murray Street.

The retaining walls are needed to allow for realignment of East Drive. For these retaining walls, the plans show Type A, B, and C retaining walls supported on 24-inch CISS piles. The Abutment 10 anchor pile located right of M-Line Station is shown immediately behind RW-17.

RW-18 is split/separated a distance of 6.0 ft at RW-18 LOL Sta. 10+36.00 to accommodate the existing 36-inch diameter sewer. The existing sewer main is proposed to be removed and supported on the north end of the bridge. We summarize the proposed RW-17 and RW-18 details in Table 2 and 3.

Table 2: Proposed Retaining Wall 17 Information

RW

No.

Lay Out Line (ft)

M-Line

Segment Wall Type

Length1

(ft) Design Height

(ft)

Bottom of Pile

Footing Elevation

(ft)

Station (ft)

Offset (ft)

RW 17

10+00.00 (Begin Wall) 16+93.99 26.5 Right

1 B 30.0 14.0 4.5

2 B 20.0 12.0 6.5

11+19.93 (End Wall) 18+05.20 36.8 Right

3 B 22.0 10.0 8.5

4 B 16.8 8.0 10.5

5 B 31.2 6.0 12.5

1) Measured along Retaining Wall Lay Out Line. Total length of RW 17 measured along LOL = 120.0 ft.

Table 3: Proposed Retaining Wall 18 Information

RW

No.

Lay Out Line (ft)

M-Line

Segment Wall Type

Length* (ft)

Design Height

(ft)

Bottom of Pile

Footing Elevation

(ft)

Station (ft)

Offset (ft)

RW 18

10+00.00 (Begin Wall) 16+86.6 45.46 Right

1 A 36.0 10.0 1.25

2 C 42.0 10.0 4.75

11+28.48 (End Wall) 18+11.68 61.29 Right

3 C 24.0 12.0 5.50

4 C 20.48 14.0 5.50 *Measured along Retaining Wall Lay Out Line. Total length of RW 18 measured along LOL = 142.0 ft.

3 GEOTECHNICAL INVESTIGATION

The following provides a generalized description of the drilling, sampling and logging methods and procedures used for the 1997, 2013 and 2015 field exploration and testing phases of this project completed by Taber Consultants. The boring locations are shown on Figure 2 in Appendix I. The Log of Test Borings (LOTB) for RW-11, RW-17 and RW-18 drawings in Appendix II provide more specific soil/rock descriptions, elevations, boring details and explanation of engineering geology descriptors and terms used to log the rock cores.

3.1 1997 EXPLORATION

A total of seven auger/rotary drilled and sampled borings (B-1 through B-7) were completed by Taber Consultants from June 1 to 11, 1997. The maximum depth below ground surface explored was 113±ft (Boring B-6; lowest elev. -127±ft). Three of the 1997 borings (B-5, B-6 and

B-7) were drilled from an overwater barge platform. The land-side borings (B-1 through R-97-

004) were typically drilled with continuous solid auger until initial groundwater was encountered and then advanced by mud-rotary method to final depth. All of the borings completed on the barge were drilled by mud-rotary method. A temporary steel casing was set through the barge deck and into the channel bottom as necessary in order to achieve an adequate ground seal for drill fluid recirculation during drilling.

3.2 2013 EXPLORATION

Between March 23 and 29, 2013, eight additional borings (A-13-008 through A-13-015) were drilled at the site to further characterize subsurface foundation conditions for the bridge and roadway approaches. One dynamic cone penetration boring (A-13-016) was also completed.

The exploratory test borings were drilled by Taber Drilling and advanced using solid auger and/or mud-rotary drilling methods through soil and rock. The underlying rock was also cored with an HQ (3.8-inch O.D.) diamond bit core barrel. The 2013 test borings were drilled with a track-mounted CME 55 drill rig.

3.3 2015 EXPLORATION

Between February 12 and 13, 2015, five borings (R-15-020, R-15-021, A-15-022, RW-15-023, R-15-024) were drilled at the site to obtain subsurface data for the proposed retaining walls (RW-11, RW-17 and RW-18). The borings were drilled by Taber Drilling and advanced using solid auger and/or mud-rotary drilling methods through soil and rock. Except for Boring A-15- 023, the 2015 borings were drilled with a trailer mounted CME 45 drill rig. Boring RW-15-023 was drilled with portable drilling equipment and sampled with a manually operated 35-pound hammer falling 22-inches (64 ft-lb hammer energy).

3.4 DRILLING AND SAMPLING – TABER CONSULTANTS

A summary of the subsurface exploration completed for the retaining wall studies is shown in Table 4.

Table 4: Subsurface Exploration Summary

Project Element Boring No. Completion

Date Drill Rig

Type Hammer

Type Hammer

Efficiency

Ground Surface

Elevation (ft)

Boring Depth

(ft)

RW-11

B-4 7-3-1997 - - - 32.5 47.5

R-13-010 3-26-2013 CME 55

Track Automatic 87 7.6 47.2

A-13-011 3-27-2013 CME 55

Track Automatic 87 30.7 25.1

RW-15-023 2-13-2015 CME 45

Trailer Automatic 104 15.1 30.5

RW-17

and

RW-18

B-3 7-2-1997 - - - 15.6 50.0

R-15-020 2-12-2015 CME 45

Trailer Automatic 104 10.8 43.8

Project Element Boring No. Completion

Date Drill Rig

Type Hammer

Type Hammer

Efficiency

Ground Surface

Elevation (ft)

Boring Depth

(ft)

RW-17

and

RW-18

R-15-021 2-12-2015 CME 45

Trailer Automatic 104 14.0 25.3

A-15-022 2-13-2015 CME 45

Trailer Automatic 104 16.6 15.2

R-15-024 2-13-2015 CME 45

Trailer Automatic 104 20.5 16.0

Soil and rock samples were recovered from all of the 1997 borings by means of a 2.0-inch outside diameter (O.D.) “Standard Penetration Test” (SPT) sampler driven into the ground with a manually operated (rope and cathead) and 140-pound safety hammer with 30-inch drop (350 ft-lb striking force). Drive samples were typically collected at approximate 5-foot intervals in the borings. Bulk samples of soil cuttings were also collected at selected depths from the borings.

Soil and decomposed rock samples for the 2013 borings were recovered by means of 2.0-inch O.D. SPT and/or 2.5-inch inside diameter (I.D.) split-spoon samplers advanced with standard 350 ft-lb striking force using an automatic trip hammer. The dynamic cone penetration boring (A- 13-016) was similarly advanced. Thin-walled, 3-in diameter Shelby tube samples were also taken in fine-grained soil layers for laboratory testing. The hammer used for the drive samples during the 2013 subsurface exploration is recorded to have a hammer energy efficiency (ERi) of 87% based on an energy calibration completed on April 9, 2012. Drive samples were typically collected at approximate 5-foot intervals in the borings. Bulk samples of soil cuttings were also collected at selected depths from the borings.

Soil and rock samples for the 2015 borings were recovered by means of 2.0-inch O.D. SPT and/or 2.5-inch inside diameter (I.D.) split-spoon samplers advanced with standard 350 ft-lb striking force using an automatic trip hammer. The hammer used for the drive samples during the 2015 subsurface exploration (excluding RW-15-023) is recorded to have a hammer energy efficiency (ERi) of 104% based on an energy calibration completed on November 18, 2014.

Drive samples were typically collected at approximate 5-foot intervals in the borings. Bulk samples of soil cuttings were also collected at selected depths from the borings.

3.5 LOGGING

The borings were logged and earth materials field-classified by an engineer/geologist as to consistency, color, texture and gradation on the bases of penetration resistance, examination of samples and observation of drill cuttings. Where rock cores were obtained, the percent recovery and Rock Quality Designation (RQD) were recorded for the recovered portions of rock.

Selected portions of recovered soil/rock samples from the driven samplers were retained in sealed containers for laboratory testing and reference. The Shelby tubes were sealed at each end of the tube with bee’s wax and capped to preserve moisture content. The Shelby tubes were kept vertical as collected in the field and transported to the laboratory in an upright position. Rock cores were retained in core boxes for reference. The bulk soil samples collected from auger cuttings were placed in plastic bags for laboratory testing and reference.

Groundwater observations were also made in the borings during and at completion of drilling operations.

3.6 SAMPLER PENETRATION RESISTANCE (N-VALUE)

The in-situ sampler penetration resistance (N-value) in blows per foot was recorded in the field to obtain an approximate measure of the dynamic resistance of the soil. The N-value was recorded as the number of hammer blows necessary to drive the sampler the final 12-inches of the 18-inch sample interval, unless refusal was met.

The SPT N-value adjusted to 60% hammer energy (N60) is routinely used to provide an index of the apparent density of cohesionless soils and sometimes (albeit less reliably) to estimate the consistency of cohesive soils. The energy-corrected N60 value normalized for effective overburden stress referred to as (N1)60 is typically used to correlate soil strength parameters and bearing characteristics.

For a non-standard sampler (i.e., non-SPT sampler), the in-situ N-value was corrected to an Equivalent SPT N-value using values published in Caltrans Geotechnical Manual (March 2021), then adjusted to provide an Equivalent N60 and/or Equivalent (N1)60 value that can be correlated to soil strength and bearing characteristics for use in geotechnical analysis.

The in-situ (uncorrected) N-values are shown on the Log of Test Borings (LOTB) drawings provided in Appendix II.

3.7 BOREHOLE ABANDONMENT

The test borings for the bridge and retaining walls were backfilled with cement grout at the completion of drilling. The borings were also surface sealed with asphalt-concrete cold patch where drilled within paved areas.

3.8 BORING LOCATIONS AND ELEVATIONS

The details and locations of test borings completed by Taber Consultants are shown on the Log of Test Borings (LOTB) drawings in Appendix II.

Taber Consultants personnel located the borings in the field relative to existing site features and subsequently to project stationing. The boring elevations for the 1997, 2013 and 2015 field studies were surveyed in the field by Taber personnel. Eric Hilmer, C.E.G., Glen Wade, P.G., and Amanda Kahn, G.I.T. were the field geologists for the respective 1997, 2013 and 2015 field studies.

4 LABORATORY TESTING PROGRAM

Laboratory tests were completed on selected representative samples obtained from the exploratory borings to aid in soil classification and evaluate the physical and engineering properties of the earth materials for use in geotechnical analysis required for the project such as liquefaction potential, shallow and deep foundations and corrosion potential, The following laboratory tests were performed on soil and/or rock samples obtained from the test explorations:

• Moisture Content - Dry Density (ASTM D2216 / D2937),

• Unconfined Compressive Strength (ASTM D2166),

• Particle Size Analysis of Soils (ASTM D422);

• Atterberg Limits (ASTM D4318);

• Consolidated Undrained Triaxial (ASTM D4767);

• Unconsolidated Undrained Triaxial (ASTM D4767);

• Sulfate/Chloride Content (CTM 417/422);

• pH and Minimum Resistivity (CTM 643); and

• Point Load Index (ASTM D5731).

Laboratory test results are shown on the LOTB drawings in Appendix II and/or provided in Appendix III.

5 GEOTECHNICAL CONDITIONS

5.1 SITE GEOLOGY

In the vicinity of the Murray Street Bridge, published1 geologic mapping shows three geologic units as follows:

• Basin deposits (Holocene);

• Lowest emergent coastal terrace deposits (Pleistocene); and

• Siltstone and Sandstone – Purisima Formation (Pliocene and upper Miocene).

The higher elevations at the margins of the lagoon are mapped as “Lowest emergent coastal terrace deposits” of Pleistocene-age. Materials of this geologic unit are described as semiconsolidated, generally well-sorted sand with a few thin, relatively continuous layers of gravel. Locally it includes many small areas of fluvial and colluvial silt, sand and gravel.

Underlying this unit is siltstone and sandstone of the Pliocene and upper Miocene-age Purisima Formation. This geologic unit is described as very thick bedded yellowish-gray tuffaceous and diatomaceous siltstone containing thick interbeds of bluish-gray, semifriable, fine-grained andesitic sandstone.

The “Basin deposits” of Holocene-age are shown overlaying the Purisima Formation within the lagoon and along the lower reaches of the slopes bordering the lagoon. These deposits are described as unconsolidated, plastic, silty clay and clay rich in organic material. Locally this unit includes interbedded thin layers of silt and silty sand.

No active fault traces are shown on published mapping to cross the site. Site seismicity and information on local faults and seismic sources is presented in Section 10.3.1. A Geologic Map is shown as Figure 3 in Appendix I.

1 Brabb, Earl E., Geologic Map of Santa Cruz County, California, United States Geological Survey (USGS), Miscellaneous Investigation Series, Map I-1905, Scale 1:62,500, 1989.

5.2 SURFACE CONDITIONS

The existing 35±feet wide by 540±feet long structure is aligned east-west and consists of nine 60-foot spans of reinforced concrete deck on precast, prestressed concrete I-girders. The substructure is comprised of two-column bents and open-style seat abutments. The structure was damaged in the 1989 Loma Prieta earthquake. Bent-2 sustained some transverse lateral displacement and as much as 2-inches of settlement. Subsequent repair work included strengthening displaced columns and excavating to visually observe pile conditions at Bents-2, - 3 and -4. Bent-6 was extended on the south side of the bridge. It is not known if damage to the railroad bridge also occurred in 1989.

Upstream (north) of the bridge, Woods Lagoon is aligned northeast-southwest; downstream (south) of the bridge, Woods Lagoon is aligned north-south. The bridge is located just downstream (south) of the confluence of a southerly flowing tributary stream that enters into Woods Lagoon from its west bank. A Santa Cruz County Regional Transportation Commission (SCCRTC) railroad bridge that also crosses over Woods Lagoon is located 20-35±feet east of the Murray Street Bridge.

Woods Lagoon is the location of the Santa Cruz Small Craft Harbor. Construction of the bridge and the harbor included placement of artificial fill along the margins of the lagoon and dredging of a boat channel below the bridge. A previous structure known as the East Cliff Drive Bridge that crossed over Woods Lagoon was also demolished/removed when the existing bridge and harbor improvements were completed.

An existing 30-inch diameter sewer force main crosses below the lagoon on the south side of the bridge. Overhead utility lines are also present along Murray Street in close proximity to the existing bridge.

5.3 SUBSURFACE CONDITIONS

Three generalized units of earth materials are identified from the test borings: underlying sedimentary rock, lagoon deposits, and fill/surficial native materials. The lagoon deposits can be further subdivided into sand, bay mud and most recent channel deposits (from bank erosion and silting of dredge channel). Fill materials include bridge approach embankments and area fills placed on both sides of the lagoon as part of harbor improvements.

The following provides a generalized description of the earth materials encountered in the borings Taber Consultants completed from the bridge foundation elements of this project. The LOTB drawings in Appendix II provide more specific soil/rock descriptions, elevations, boring details and explanation of engineering geology descriptors and terms used to log the rock cores.

5.3.1 SEDIMENTARY ROCK (SANDSTONE)

As encountered in the test borings, the underlying rock unit consists of variably weathered sedimentary rock (sandstone) that is generally described as thickly to massively bedded, decomposed and intensely to moderately weathered, very soft to moderately soft and moderately to slightly fractured. From west to east along the retaining wall alignments, the top of the underlying sedimentary rock as encountered in the borings completed for the retaining walls is shown in Table 5 and 6.

Table 5: Retaining Wall No. 11 Approximate Rock Surface Encountered

Boring Number

Year Completed

M-Line Top of Boring Approximate Rock Surface Encounter

Station (ft)

Offset (ft)

Elevation (feet, NGVD29)

Depth

(ft) Elevation

(ft, NGVD29)

A-13-011 2013 10+79.1 7.6 Left 30.7 8.0 22.7

B-4 1997 11+25.6 20.2 Left 29.5 16.0 13.5

A-15-023 2015 11+59.7 8.8 Right 15.1 25.1 -10.0 A-13-010 2013 11+90.8 34.4 Right 7.6 40.0 -32.4

Notes: The locations/depths/elevations shown in the table are approximate.

Table 6: Retaining Wall No. 17 and 18 Approximate Rock Surface Encountered

Boring Number

Year Completed

M-Line Top of Boring Approximate Rock Surface Encounter

Station (feet)

Offset (feet)

Elevation (feet, NGVD29)

Depth (feet)

Elevation (feet, NGVD29)

A-15-020 2015 16+80.7 38.5 Right 10.8 32.5 -21.7

B-3 1997 16+99.1 16.2 Right 12.6 28.0 -15.4

A-15-021 2015 17+21.2 34.0 Right 14.0 18.5 -4.5 A-15-022 2015 17+59.5 28.7 Right 16.6 13.0 3.6 A-15-024 2015 18+09.2 47.1 Right 20.5 9.0 11.5

The upper portions of the underlying rock unit were penetrated with light-weight drilling equipment using tungsten-carbide tipped drill bits. Some cemented zones were highly resistant to this drilling method. Where attempted, SPT samplers typically achieved only partial penetration of the rock unit. In the borings RW-13-010 and A-13-011 where the rock was cored with a diamond drill bit, the recovery typically varied from 54 to 100% and Rock Quality Designation varied from 46 to 96%.

Point Load Index test results on very intensely to intensely weathered rock core samples from the borings RW-13-010 and A-13-011 typically indicate weak rock with correlated uniaxial compressive strengths that range from 0 to 400 pounds/square inch (psi). It was noted that these samples were soft and broke apart with light pressure. Factors accounting for the variability in Point Load strength include rock composition, fracturing, grain size and weathering characteristics. The Point Load Index test results are included in Appendix III.

5.3.2 LAGOON DEPOSITS

The low areas in the rock surface (consistent with incised channels) are filled with natural lagoon deposits comprised of a sequence of mostly loose to medium dense (locally dense) silty sand/sandy silt with local woody and organic material and local gravel lenses overlain by typically very soft organic silty clay (“bay mud”) with shells.

At the west bank and tributary channel area (Borings B-1, -2, -4, -10, -15 and -16), lagoon deposits encountered in these borings vary in thickness and generally consist of 6±feet (A-13-

015) to 31±feet (B-2) of materials interpreted as “bay mud” underlain by sedimentary rock (sandstone) expect in Boring B-2 where the “bay mud” is underlain by about 30±feet of materials generally described as loose and very loose (locally dense) silty sand. Lagoon deposits are essentially absent in Boring B-1/Bent-4 and in Boring B-4/Abutment-1.

In the main Woods Lagoon channel (Borings B-5, -6 and -7), the uppermost 5-8±feet of soil, interpreted as recent channel deposits, is described as loose-very loose silty sand and very soft sandy silt and silt. Lagoon deposits underlying these soils vary in thickness and generally consist of 34±feet (B-7) to 47±feet (B-5) of materials interpreted as “bay mud” underlain by about 4±feet (B-7), 35±feet (B-5) and 37±feet (B-6) of materials generally described as loose to medium dense (locally very loose, compact and dense) clayey/silty sand.

At the east bank (Boring B-3, A-13-008, A-13-009), lagoon deposits encountered in the borings vary in thickness and generally consist of 10±feet (B-3), 45±feet (A-13-008) and 63±feet (A-13-

009) of materials interpreted as “bay mud” underlain by sedimentary rock (sandstone).

Laboratory test results on fined-grained soil samples from this unit classify as silt (ML) with Liquid Limit from 21 to 29 and low plasticity (PI ≤ 5) to non-plastic (NP); lean clay (CL) with Liquid Limit from 27 to 55 and Plasticity Index ranging from 13 to 33; and fat clay (CH) with Liquid Limit from 50 to 69 and Plasticity Index ranging from 25 to 40. The water content of nearly all tested samples exceeds the Liquid Limit, consistent with salt water deposition and flocculent soil structure.

The granular soils and low plasticity silt layers of this unit are in the range of texture and consistency potentially susceptible to liquefaction; “bay mud” materials may be “sensitive”, i.e.

they may suffer substantial loss of shear strength if/as disrupted (conversely, their in-place undisturbed strength may exceed that exhibited in field and laboratory testing performed for this study). Liquefaction potential of these soils is presented in Section 10.3.2.

5.3.3 FILL/SURFICIAL NATIVE MATERIALS

At the west and east banks, materials interpreted as fill and surficial native materials as encountered in the borings completed for the bridge are generally described as loose to slightly compact clayey/silty sand and soft (locally stiff) clayey silt/silty clay with local/scattered wood, peat and other debris. Such materials were encountered from the ground surface (or below nominal asphalt pavement section) to depths of 6±feet to 18±feet. The uppermost 3±feet to 13±feet of this unit appear to be mostly fill and may be in-part naturally occurring material eroded from adjacent terraces. These materials overly the lagoon deposits except in Borings B- 1 and B-4 where they directly overly the sedimentary rock (sandstone).

6 GROUNDWATER

The groundwater conditions encountered in the borings completed for retaining walls are presented in Table 7. The water surface in Woods Lagoon varies due to tidal influence.

Table 7: Summary of Groundwater Data

Boring Number

Ground Surface

Elevation (ft, NGVD29)

Depth to Groundwater

(ft)

Groundwater Elevations

(ft) Date

Measured

B-3 12.6 13.2 -0.6 07/02/1997 B-4 29.5 19.0 10.5 07/03/1997

A-13-010 7.6 6.5 1.1 03/26/2013 A-13-011 30.7 4.3 23.7 03/27/2013 A-13-012 31.6 4.0 27.6 03/27/2013

A-13-012A 31.6 Not Measured/Dynamic Cone Penetration Test Boring 03/27/2013

A-15-017B 31.8 10.7 21.1 02/10/2015 A-15-018B 48.3 23.6 24.7 02/11/2015 A-15-019 31.1 15.7 15.4 02/11/2015 A-15-020 10.8 7.8 3.0 02/12/2015 A-15-021 14.0 8.7 5.3 02/12/2015 A-15-022 16.6 9.0 7.6 02/13/2015

7 AS-BUILT FOUNDATION DATA

No as-built retaining wall foundation plans were available to review for this project at the time of this report was prepared.

8 SCOUR DATA

Scour is not indicated to be a consideration for retaining wall design.

9 CORROSION EVALUATION

The project is located in a marine environment and within a tidal channel (chloride concentration in seawater is approximately 19,000 mg/l) that is considered corrosive and the design of reinforced concrete and steel foundation elements should consider potential exposure to corrosive salt water and marine atmosphere.

10 SEISMIC DESIGN INFORMATION AND RECOMMENDATIONS

10.1 GROUND MOTION

Due to the presence/thickness of soft, compressible and potentially liquefiable soil layers identified at this site, a site-specific seismic analysis was completed for this project by

StrongMotions, Inc. (Sharon, Massachusetts), report titled “Site-Specific Seismic Response of Free-Surface Horizontal Motion for Murray Avenue Bridge, Report Number: SMI-12-2010” dated August 20, 2010.

StrongMotions Inc. used latitude 36.967998° and longitude -122.002316° for the site coordinates and an envelope correlated shear wave velocity (VS30) from firm rock to soft rock site conditions in the upper 100 feet of the soil profile equal to 760 meters per second (about 2,500 feet per second) and 474 meters per second (about 1,554 feet per second) respectively.

These value corresponds to a “rock” with 760 m/s < Vs < 1500 m/s (Soil Profile Type B) and a “very dense soil and soft rock” with 360 m/s < Vs < 760 m/s (Soil Profile Type C) for the upper 100 feet of the soil/rock profile and is considered appropriately conservative for use in bridge design at this site.

The VS30 value was determined for this site based on the subsurface data obtained from the test borings and correlations with SPT blow count N-values corrected for hammer efficiency using the equations outlined by Caltrans2. The correlated VS30 values estimated from the test boring logs are shown in Table 8.

Table 8: Correlated Shear Wave Velocity

Boring Designation

Support Location

Top of Boring

Elevation

(NGVD29,

feet)

Bottom of Boring

Elevation

(NGVD29,

feet)

Total Boring Depth (feet)

Correlated Shear Wave Velocity in Upper 100 feet*

VS30

(m/sec)

VS30

(ft/sec)

B-4 Abut-1 29.5 -16.8 46.3 390 1282 B-2

Bents-2 to -9

6.8 -88.5 95.3 104 342 B-1 8.0 -37.3 45.3 409 1342 B-7 2.6 -83.4 86.0 139 457 B-6 -0.5 -126.5 126.0 64 210 B-5 2.5 -113.9 116.4 59 192 B-3 Abut-10 12.6 -37.7 50.3 252 826

1) We include specific test boring data for the above borings in our separate 2023 Final Foundation Report for the bridge structure.

2) The depth to “soft” bedrock (sandstone) varies from 10 ft for Boring B-1 to 87 feet for Boring B-5.

The report by StrongMotions, Inc. identified the two controlling sources for this site as the Monterey Bay-Tularcitos (Monterey Bay section) and the San Andreas Fault zone (Santa Cruz Mountains section). The Monterey Bay-Tularcitos (Monterey Bay section) has a maximum magnitude of 7.3 and is located approximately 11.8 km (7.3± miles) southwest of the site. The San Andreas Fault zone (Santa Cruz Mountains section) has a maximum magnitude of 7.9 and is located approximately 17.2 km (10.6± miles) northeast of the site.

10.1.1 RECOMMENDED SEISMIC DATA

Based on the results of the site-specific analysis completed by StrongMotions, Inc., we recommend that structure design be based on the following Caltrans SDC parameters:

2 California Department of Transportation, Methodology for Developing Design Response Spectrum for Use in

Seismic Design Recommendations, Appendix A, November 2012.

• Soil Profile Type F;

• Maximum Moment Magnitude (Mmax): 7.9;

• Peak Ground Acceleration (PGA): 0.60g; and

• Controlling Spectra: Pseudo-acceleration and deformation response spectrum values of free-surface horizontal motions for the bridge for 5% of critical damping as recommended by StrongMotions, Inc. and presented in Table 9 on page 24 of their report (see Appendix VII of our 2023 Final Foundation Report for the bridge structure).

10.2 OTHER SEISMIC HAZARDS

10.2.1 SURFACE FAULT RUPTURE

No active fault traces are shown on published mapping to cross the site and the site is not within or adjacent to an Alquist–Priolo Earthquake Fault Zone for fault rupture hazard. The nearest mapped fault is the Ben Lomond Fault, is located approximately 2± miles to the west of the site.

This fault is considered not active within the Holocene by the California Geologic Survey and is not included in the faults shown on the Caltrans “Seismic Hazard Map”. No evidence of surface fault rupture was observed from our geologic reconnaissance at the bridge site. On these bases, the potential for surface fault rupture within the project limits is considered low. We show nearby faults on Figure 4 in Appendix I.

10.2.2 LIQUEFACTION POTENTIAL

Liquefaction is a secondary effect associated with seismic loading that can occur when saturated, relatively loose sand and specific soft, fine-grained saturated soils are subject to ground shaking strong enough to create soil particle separation that results from increased pore pressure. This separation and subsequent pore pressure dissipation can lead to decreased soil shear strength and settlement. Liquefaction is known to occur in soils ranging from low plasticity silts to gravels. However, soils most susceptible to liquefaction are clean sands to silty sands and non-plastic silts.

Liquefaction susceptibility of a soil deposit is a function of the soil grain size, relative density, percent fines, plasticity of the fines, degree of saturation, age of deposit, and earthquake ground motion. According to Caltrans guidelines, liquefaction potential is evaluated using the “Simplified procedure” to a depth of 70 ft in the soil profile below the channel bottom. Caltrans guidelines cite Bray and Scancio (2006) criteria to determine liquefaction susceptibility of fine-grained soils when the Plasticity Index (PI) £ 12 or the [water content (wc) / liquid limit (LL)] > 0.85. Boulanger and Idriss (2006) recommend considering a soil to have clay-like behavior (i.e., not susceptible to liquefaction) when the PI ³ 7. Predominately fine-grained (cohesive) soils such as clay and elastic silts would be considered subject to cyclic softening with a potential for reduction in shear strength rather than “classic” cyclically induced liquefaction associated with loose, saturated granular soils.

To evaluate the potential for soil liquefaction to occur at the site, Crawford used the simplified procedure outlined by Youd et al. (2001)3 and guidelines/modifications consistent with

3 Youd, T. L., et al, Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF

Workshops on Evaluation of Liquefaction Resistance of Soils, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 127, No. 10, October 2001, pp. 817-833.

liquefaction evaluation outlined in the Caltrans Geotechnical Manual (Liquefaction Evaluation Module, January 2020), the 1997 and 2013 boring data and laboratory test results, design groundwater at elev. 5.0 ft, a site-to-fault distance of 7.3 miles, Maximum Moment Magnitude (Mmax) of 7.9, and a Peak Ground Acceleration (PGA) of 0.60g. The seismic/fault parameters used in our analysis are based on the site-specific response analysis completed by Strong Motions, Inc. Refer to Appendix IV that includes the results of our liquefaction triggering analysis.

Based on the foregoing and our analysis of the 1997, 2013, and 2015 boring data, potentially liquefiable soils are present at this site. In general, we identify the potentially critical liquefiable soil zones (Factor of Safety < 1.0) in Table 9.

Table 9: Potentially Liquefiable Soil Zones/Layers

Boring

ID

Nearest Support

Potentially Liquefiable Soil Zones/Layers Liquefaction

Factor of Safety

Estimated Seismic-induced

Settlement (in)

Estimated Downdrag

Load (kip/pile)

Elevation (feet, NGVD29)

Layer Thickness

(feet) B-4 RW 11 None NA NA NA NA

A-15-020 RW 17

and 18 5.0 to -6.0 11.0 0.21 to 0.35 2.0 10

B-3 RW 17

and 18

5.0 to -5.0 -10.0 to -15.0

10.0 5.0

0.15 to 0.34

0.12 5.0 10

A-15-021 RW 17

and 18 3.5 to -4.5 8.0 0.33 2.0 10

Notes: The elevations shown in the table are approximate.

NA = Not Applicable.

Downdrag loads calculated for 24-inch CISS at Retaining Wall 17 and 18.

Soft and very soft clays (bay mud) in several test borings are not considered to liquefy but are prone to excessive movement/displacement (cyclic softening) under loading and provide little lateral support for piles. Approximate soft to very soft clay zones are identified in the borings as follows:

Table 10: Soft and Very Soft Clay Zones/Layers

Boring ID Nearest Support Elevation (feet, NGVD29) Layer Thickness (feet)

B-4 RW 11 None NA

A-15-023 RW 11 14.0 to -10.0 24.0

A-15-020 RW 17 and 18 -6.0 to -20.0 14.0 Notes: The elevations shown in the table are approximate.

NA = Not Applicable.

10.2.3 SEISMICALLY INDUCED SETTLEMENT

The potential for seismically induced settlement is considered high. Calculated settlement from the boring data indicate high variability across the site and high variable magnitudes of settlement.

During a seismic event, ground shaking can cause densification of granular soils that can result in settlement of the ground surface. For retaining wall foundation design, we consider the potentially liquefiable soil layers identified in Table 9 to be subjected to reduction to residual shear strength values and seismically induced (vertical) settlement under conditions of strong ground shaking form a design earthquake event.

Based on our analysis, potential post-liquefaction ground settlement across the length of Retaining Wall 17 and 18 ranges from 2-inches to as much as 5.0-inches (Boring B-3).

Appendix IV includes our calculation results for seismically induced ground settlement.

The methods outlined by Idriss and Boulanger (2008)4 were used to estimate post-liquefaction settlement. The method follows the approach developed by Ishihara and Yoshimine (1992) that relates volumetric strain, SPT (N1)60cs [i.e., (N1)60 values corrected for fines content], and the factor of safety against liquefaction (FSL) to estimate the post-liquefaction settlement of a liquefied layer.

Seismically induced settlement can cause drag loads/negative skin friction forces on deep foundation.

10.2.4 SEISMIC SLOPE INSTABILITY

Seismic slope instability is presented/discussed in our Final Foundation Report.

10.2.5 TSUNAMI

The west coast of California is subject to tsunami hazard. A tsunami is a large sea wave or series of waves generated by the sudden displacement in the sea floor that can be produced by an earthquake, submarine landslide, volcanic activity, or other event that causes large-scale disturbance of the sea floor.

Woods Lagoon and the Santa Cruz Small Craft Harbor are located within a mapped tsunami inundation zone. The likely source for Tsunami generation at the project site is an earthquake (distant source). In March 2011, the Santa Cruz Harbor sustained damage from tsunami wave surges triggered by the March 11, 2011 magnitude 9. Tōhoku Earthquake that occurred in the north-western Pacific Ocean located about 50 miles from the east coast of Japan. While that event caused damage to boats and docks within the Santa Cruz Small Craft Harbor, no damage was reported to have occurred to the existing Murray Street Bridge.

Based on the foregoing, there is a potential for tsunami and inundation hazard at the project site. Potential hazard from a tsunami to the existing bridge could include debris impact to the structure and possible erosion/scour due to temporary increase flow rate through the channel.

4 Idriss, I. M. and Boulanger, R. W., "Soil Liquefaction During Earthquakes," Earthquake Engineering Research

Institute, pages 140-142 and 152-158, 2008.

Should there be important design considerations with respect to tsunami hazard for this project/site, additional study would be required.

11 GEOTECHNICAL RECOMMENDATIONS

Soil conditions at the project site are considered to be adequately stable and suitable for construction of the proposed retaining wall structures. It is recommended to achieve support within the underlying rock for the new retaining wall foundation elements. We did not find evidence for major geologic hazards, such as landslides, subsidence, severe erosion, compressible or expansive soils, or naturally occurring asbestos. Our evaluation identifies the presence of soil layers that are in the range of soil texture and consistency considered susceptible to liquefaction during a design earthquake event. Therefore, downdrag (negative skin friction) to new pile foundations is anticipated during design earthquake load conditions.

In consideration of the presence of groundwater and generally weak, unstable soils, conditions are considered most suitable for the use of driven foundation types. Due to the great variability of the underlying rock surface and constricted working area, steel pipe piling is recommended.

Such piles are expected to penetrate into the rock and develop compressive resistance in side friction and point bearing. The foundation recommendations in this report are in accordance with the AASHTO LRFD Bridge Design Specifications (8th Edition) with Caltrans Amendments.

The subsurface data suggest that the underlying (i.e., buried) rock surface is highly variable.

Implied overall slopes on this buried surface are as steep as 1.2:1 (horizontal:vertical distance);

locally. In addition to variation along the retaining wall alignments, the rock surface also slopes variably across the roadway width. Based on test boring data, the estimated rock elevation at individual support locations is shown in Table 11.

Table 11: Estimated Rock Elevations

Location Pile Type

Cutoff Elev.

(feet)

Estimated Rock Elev.

(feet) RW 11 Segment 1 24” CISS 18.75 20 to 16 RW 11 Segment 2 24” CISS 15.75 16 to 14 RW 11 Segment 3 24” CISS 12.75 14 to 8 RW 11 Segment 4 24” CISS 6.25 8 to -7 RW 17 Segment 1 24” CISS 4.75 -8 to -20 RW 17 Segment 2 24” CISS 6.75 -3 to -8 RW 17 Segment 3 24” CISS 8.75 3 to -3 RW 17 Segment 4 24” CISS 10.75 6 to 3 RW 17 Segment 5 24” CISS 12.75 11 to 6 RW 18 Segment 1 24” CISS 1.50 -5 to -18 RW 18 Segment 2 24” CISS 5.00 4 to -5 RW 18 Segment 3 24” CISS 5.75 11 to 4 RW 18 Segment 4 24” CISS 5.75 4 to 12

Note: The estimated rock elevations shown in this table may vary significantly from the actual rock elevations. All elevations shown are NGVD29 datum.

The estimated rock elevations shown in Table 11 may vary significantly from the actual rock elevations/contours. A simplified soil/rock profile was used for pile foundation design. The specified tip elevation should be adjusted (up/down) depending on confirmation of the actual rock surface at each retaining wall segment.

The proximity of structures/facilities located in the project vicinity, particularly the existing bridges, existing 30-inch diameter sewer force main and nearby residences/businesses, will require consideration with respect to ground vibration due to pile driving operations. Evaluation of vibration induced settlement is difficult to accurately predict. Section 12.6 provides recommendations for monitoring before, during and after construction. Ground vibration due to driving piles should be assessed by the maximum peak particle velocity (ppv). Guidelines developed by the U.S. Department of Transportation indicate that vibration levels between 0.5-

1.0 inch per second is the threshold at which there is a risk of architectural damage to normal dwellings and that most construction vibration limits are within the range of 1.0-2.0 inches per second.

11.1 RETAINING WALL FOUNDATION DATA AND LOADING

Foundation Design Data and Pile Foundation Design Loads for 24-inch CISS pile foundations provided by TRC are presented in Table 12 and 13.

Table 12: Retaining Wall Foundation Design Data

Support Location

Design Method

Design Height

(ft) Pile Type

Max.

Finished

Grade Elev.

(ft)

Min.

Finished

Grade Elev.

(ft)

Cut-off Elev.

(ft)

Bottom of Footing

Elev.

(ft)

Pile Cap Size

(ft) Permissible

Settlement Number of Piles

B L

RW 11

Segment 1 LRFD H=10 CISS NPS 24x0.5 30.5 26.0 18.75 18.50 10.0 18.00 1” 6

RW 11

Segment 2 LRFD H=14 CISS NPS 24x0.5 26.0 23.0 15.75 15.50 10.0 12.00 1” 4

RW 11

Segment 3 LRFD H=14 CISS NPS 24x0.5 23.0 18.0 12.75 12.50 10.0 12.00 1” 4

RW 11

Segment 4 LRFD H=14 CISS NPS 24x0.5 18.0 11.0 6.25 6.00 10.0 18.00 1” 6

RW 17

Segment 1 LRFD H=14 CISS NPS 24x0.5 12.0 9.0 4.75 4.50 10.0 30.00 1” 10

RW 17

Segment 2 LRFD H=12 CISS NPS 24x0.5 13.5 12.0 6.75 6.50 10.0 20.00 1” 6

RW 17

Segment 3 LRFD H=10 CISS NPS 24x0.5 16.0 13.5 8.75 8.50 10.0 22.00 1” 8

RW 17

Segment 4 LRFD H=8 CISS NPS 24x0.5 17.5 16.0 10.75 10.50 10.0 16.77 1” 6

RW 17

Segment 5 LRFD H=6 CISS NPS 24x0.5 20.5 17.5 12.75 12.50 10.0 31.16 1” 8

RW 18

Segment 1 LRFD H=10 CISS NPS 24x0.5 10.0 9.0 1.50 1.25 10.0 36.00 1” 10

RW 18

Segment 2 LRFD H=10 CISS NPS 24x0.5 10.5 9.5 5.00 4.75 10.0 42.00 1” 10

RW 18

Segment 3 LRFD H=12 CISS NPS 24x0.5 10.5 10.0 5.75 5.50 10.0 24.00 1” 6

RW 18

Segment 4 LRFD H=14 CISS NPS 24x0.5 11 10.0 5.75 5.50 10.0 20.48 1” 6

Notes: 1) Based on Caltrans current design practice, the total permissible settlement is one inch for multi-span structures with continuous spans or multi-column bents, one inch for single span structures with diaphragm abutments, and two inches for single span structures with seat abutments. Different permissible settlement under service loads may be allowed if a structural analysis verifies that required level of serviceability is met.

2) Number of piles show is per footing step or segment as shown on plans.

Table 13: Retaining Wall Foundation Design Loads

Support

Service – I Limit State (kips)

Strength Limit State (Controlling Group, kips)

Extreme Event Limit State (Controlling Group, kips)

Total Load Perm.

Load Compression Tension Compression Tension

Per Support

Max Per Pile

Per Support

Per Support

Max Per Pile

Per Support

Max Per Pile

Per Support

Max Per Pile

Max Perm.

Per Pile Per

Support Max Pile

RW 11 Segment 1 328 85 293 447 103 N/A 0 293 106 49 N/A 0

RW 11 Segment 2 273 117 250 370 147 N/A -3 250 133 63 N/A -4

RW 11 Segment 3 273 117 250 370 147 N/A -3 250 133 63 N/A -4

RW 11 Segment 4 407 1115 373 551 145 N/A -3 373 132 62 N/A -4

RW 17 Segment 1 499 74…