Specifications Part 2 of 4.pdf

12-1

Earth Mechanics, Inc.

Geotechnical & Earthquake Engineering

12.0 APPENDIX E, GEOPHYSICAL SURVEY AND

BATHYMETRY MAP

Golder Associates Inc.

18300 NE Union Hill Road, Suite 200 Redmond, Washington 98052 Telephone: (425) 883 0777 Fax: (425) 882 5498

OFFICES ACROSS AFRICA, AUSTRALIA, EUROPE, NORTH AMERICA AND SOUTH AMERICA

021306rs1-EarthMech Rpt..doc

February 13, 2007 Our Ref: 063-1380

Earth Mechanics, Inc.

17660 Newhope Street, Suite E Fountain Valley, CA 92708

Attention: Hubert Law

RE: DRAFT REPORT OF THE RESULTS OF OFFSHORE SURVEY AT THE ANTIOCH

AND DUMBARTON BRIDGES, SAN FRANCISCO BAY, CALIFORNIA

Dear Mr. Law:

Enclosed is a draft copy of the report from the results of the marine survey performed by Golder Associates at the Antioch and Dumbarton Bridges. The investigation was conducted with multibeam bathymetry, sidescan sonar and subbottom/seismic reflection profiling. The interpreted results of the geophysical investigation are presented on a series of figures, drawings and maps included with the written document. We have also placed this information on an ftp site in PDF and DWG format.

After we receive your review comments we will make requested or recommended changes to the report and issue a final report.

If you have any questions regarding the draft report please contact me.

Sincerely, GOLDER ASSOCIATES INC.

DRAFT DRAFT

Richard E. Sylwester L.G, L.E.G. Richard Graham Principal Marine Geophysicist Senior Marine Geophysicist

RES/se

Enclosure

Redmond, Washington 98052 Telephone: (425) 883 0777 Fax: (425) 882 5498

OFFICES ACROSS AFRICA, AUSTRALIA, EUROPE, NORTH AMERICA AND SOUTH AMERICA

DRAFT REPORT

RESULTS OF THE OFFSHORE GEOPHYSICAL INVESTIGATION

DUMBARTON AND ANTIOCH BRIDGES

Submitted to:

Earth Mechanics Inc.

17660 Newhope Street, Suite Ec

Fountain Valley, California 92708

Submitted by:

Redmond, Washington 98052

February 13, 2007 063-1380.300

Draft February 13, 2007 -i‐ 063-1380.300

Golder Associates

TABLE OF CONTENTS

1.0 PROJECT OBJECTIVES

2.0 FIELD PROGRAM

2.1 Offshore Survey Instrumentation

2.1.1 Survey Vessel

2.1.2 Survey Area

2.1.3 Navigation

2.1.4 Bathymetry

2.1.5 Sidescan Sonar

2.1.6 Subbottom Profiling System

3.0 OFFSHORE SURVEY PROCEDURES

3.1 Operations

3.2 Survey Coverage

4.0 DATA PROCESSING AND ANALYSIS

4.1 Navigation

4.2 Bathymetry Data

4.3 Side Scan Sonar Data

4.4 Subbottom Reflection Data

5.0 DATA RESULTS

5.1 Dumbarton Bridge (Maps D1-D6)

5.1.1 Bathymetry Results

5.1.2 Sidescan Sonar Results

5.1.3 Subbottom Results

5.2 Antioch Bridge (Maps A1-A6)

5.2.1 Bathymetry Results

5.2.2 Sidescan Sonar Results

5.2.3 Subbottom Reflection Results

LIST OF TABLE

Table 1 Instrumentation and Specifications

February 13, 2007 -ii- 063-1380.300

LIST OF FIGURES

Figure 1 Site Map-Antioch and Dumbarton Bridges Figure 2 Swath Bathymetry, Sidescan Sonar and Subbottom Profiling Methods Figure 3 Example of Sidescan Sonar Data from Dumbarton Bridge Figure 4 Example of Sidescan Sonar Data from Antioch Bridge Figure 5 Example of Subbottom Data from Dumbarton Bridge Figure 6 Example of Subbottom Data from Antioch Bridge

LIST OF MAPS

D1 Trackline Map Dumbarton Bridge D2 Bathymetric Contours, Dumbarton Bridge D3 Bathymetric Shaded Relief Image, Dumbarton Bridge D4 Contours Overlain on Shaded Relief Image, Dumbarton Bridge D5 Dumbarton Sidescan Mosaic D6 Interpreted Profiles, Dumbarton Bridge

A1 Trackline Map Antioch Bridge A2 Bathymetric Contours, Antioch Bridge A3 Bathymetric Shaded Relief Image, Antioch Bridge A4 Contours Overlain on Shaded Relief Image, Antioch Bridge A5 Dumbarton Sidescan Mosaic A6 Interpreted Profiles, Antioch Bridge

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1.0 PROJECT OBJECTIVES

The California Department of Transportation (Caltrans) and the Bay Area Toll Authority (BATA), plan to undertake seismic evaluations of the Dumbarton and Antioch Bridges to withstand potential future earthquakes (Figure 1). Under this contract EMI are providing geotechnical engineering services necessary to support the retrofit designs and collaborate with Caltrans design engineers on the retrofit project.

To assist in the retrofit design program an offshore geophysical program was conducted at the two bridges by Golder Associates Inc. The specific objectives of geophysical program and the methods used to achieve these objectives included:

• Detailed Bathymetric Map Multibeam Bathymetric Survey

• Surficial Features on Seabed Sidescan Sonar

• Subsurface Stratigraphy Subbottom Profiling

This report discusses the field program, describes the methods of analysis and presents the interpreted results on a number of figures and maps located in the appendix (Figures 1-6, Maps D1-D6 and A1-A6)

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2.0 FIELD PROGRAM

The offshore geophysical investigation was a multiple component study that includes precision navigation, precision bathymetry, sidescan sonar, and seismic reflection or subbottom profiling (Figure 2). The following is a brief discussion of these methods.

2.1 Offshore Survey Instrumentation

2.1.1 Survey Vessel

The geophysical instruments were installed on the survey vessel R/V SeaCAT a 22 foot catamaran a specially designed vessel that allowed for the installation of acquisition electronics and processing systems and for simultaneous operations of all systems. The equipment installation took place at a local marina followed by calibration and dock side operational checks. A final operational check was made of all systems prior to initiation of the surveys.

2.1.2 Survey Area

The survey areas are located in the immediate vicinity of the Dumbarton and Antioch Bridges.

Geophysical data were acquired along the full alignment and around the piers of each bridge. A number of transects were run on either side of the bridges in addition to cross line transects that ran between the piers (A1, D1)

2.1.3 Navigation

A differential global positioning system (DGPS) was used to determine the vessel’s location in real-time, and to plot the vessel’s position along the pre-selected survey lines. The pre-plotted survey lines, and the actual survey lines traversed, were displayed in real time on a video monitor located on the bridge for use by the vessel operator. The navigation computer transmitted event marks to the geophysical recording instruments every 10 seconds in order to correlate the geophysical data with the survey vessel position during data analysis and mapping. These event marks were also logged with the geophysical digital data.

A Trimble Ag132 with Omnistar differential correctors was used for real time positioning of the vessel. All data were collected in NAD-83 California State Plane North zone #0402 with coordinates in US survey feet.

2.1.4 Bathymetry

Bathymetric data were collected using a state-of-the-art multibeam automated hydrographic system that collected data in a swath configuration. Output of the multibeam transducer was coupled with a motion sensor, heading sensor, DGPS positioning system, and velocimeter. The complete system produced accurate depth measurements (IHO standards) over a 120 degree swath. The motion sensor tracked the sonar beam and corrected for movement of the DGPS antenna. The DGPS antenna was mounted directly over the swath transducer thereby reducing offset induced errors. The velocity of sound in the water column was measured at selected depths using an acoustic velocimeter. This information was logged in the computer and used to correct the depths during processing of the bathymetric multibeam data.

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2.1.5 Sidescan Sonar

Acoustic images of the seafloor were acquired using a 100 KHz sidescan sonar system. The sidescan data were printed in real-time on a thermal graphic recorder and archived on a digital recorder and on a digital acquisition system. The graphic recorder and the digital acquisition system were interfaced with the navigation system that generated sequentially numbered event marks at 10-second intervals.

The sidescan sonar transducer was towed from the bow of the survey vessel which provided extremely quiet acoustic conditions and a stable tow configuration. The sidescan display was set for a full scale range of 600 feet (140 ms) which provided approximately 200% overlap coverage of data on adjacent transects.

2.1.6 Subbottom Profiling System

Subbottom data were acquired with a low frequency seismic reflection profiling system. The system achieved subsurface penetration of up to 260 feet below the seafloor in the medium to coarse-grained sediment and stiff clay. The subbottom reflection data, acquired three times each second, or for every two foot of travel along the transect, were displayed in real-time on a thermal graphic recorder and archived on a digital recorder and on a digital acquisition system. The digital acquisition systems and the graphic recorder were interfaced with the navigation computer which annotated event mark at 10 second intervals.

TABLE 1

Instrumentation and Specifications

System Manufacturer Parameters Differential GPS Trimble 4000 SSE L1 C/A code, 12 Channel, Omnistar différential corrections.

Seismic Energy Source Datasonic Bubble

Pulser 350/700 Hz, 24 joules

Seismic Array NWGS Hydrophone 15 element, high-resolution array Seismic Processor GeoAcoustic 5210A 100 db gain, TVG, BP filter Multibeam Echosounder Reson Model 8124 250 KHz, 1.5 degree Multibeam Acquisition HySweep Sidescan Sonar GeoAcoustic Model 100/400 KHz Seismic Digital Acquisition Sony Model 208 DAT 8 Channel, 12 bit DAS Digital Acquisition Chesapeake SonarWiz 12 bit, mosaic Digital Acquisition Chesapeake SonarWiz TVG, 12 bit logging for sidescan sonar Seismic Digital Acquisition Sony Model 208 DAT 8 Channel, 12 bit DAS Graphic Display Recorders EPC Model 1086-500 2-Channel, 12 bit display

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3.0 OFFSHORE SURVEY PROCEDURES

3.1 Operations

The navigation, hydrographic and seismic reflection systems (transducers, power supply, digital acquisition systems, graphic recorders,) were installed on the survey vessel at the marina located in close proximity to the Dumbarton Bridge. The subbottom acoustic source was mounted on the starboard side of the vessel and the hydrophone streamer was towed from the port side of the vessel.

The multibeam transducer was mounted in a well located in the center of the vessel and the sidescan sonar was towed from the bow. The power supplies, processing amplifier, digital acquisition systems, graphic recorders and navigation equipment were installed in the instrumentation lab located adjacent to the hydrographic/navigation system and the bridge.

A dock side operational test was performed on the systems followed by a brief sea trial to calibrate systems that could not be tested dockside (acoustic sources array, hydrophones). The navigation system and hydrographic system were tested and calibrated at this time.

Upon completion of successful operations test and calibration the survey began at the Dumbarton Bridge and then was followed by the Antioch Bridge survey.

3.2 Survey Coverage

A series of transects were run parallel to each bridge followed by transects that passed perpendicular to the bridges and between the piers (Maps A1, D1). For the Dumbarton bridge a total of twelve (12) transects were run parallel to the bridge and ten (10) transects were run perpendicular, between the piers. At the Antioch bridge nine (9) transects were run parallel to the bridge and ten (10) transects were run between the piers.

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4.0 DATA PROCESSING AND ANALYSIS

Preliminary analysis and archiving of geophysical data was done at the end of each survey day. This consisted of reviewing the trackline locations to verify the data coverage, QA/QC of the swath bathymetric, sidescan and subsurface reflection data, archiving field records, and downloading the digital data to digital media.

4.1 Navigation

A table of event numbers (10 second intervals), with their x, y coordinates was generated from the navigation data for each bridge. The event numbers, which correspond with the events printed on the paper copies of the geophysical data and the digital data, were then plotted on a trackline map (A1, D1). These maps were used for interpreting the geophysical data and correlating the geophysical data with the boring logs that had been obtained during previous studies for the bridge.

4.2 Bathymetry Data

The multibeam bathymetric data were edited and corrected for, ship roll, heave and pitch, and removal of anomalous depth values due to water column noise. The depth data at the Dumbarton Bridge were corrected to MLLW using NOAA predicted tides. The tide data were cubic splined (a curved interpolation technique) on even one minute increments. The depths were then converted from MLLW to NAVD 88 (corrections for MLLW to NGVD 29 were not available at this time). For the final report these data will be referenced to NGVD 29 which is approximately 5 feet greater. The depth data at the Antioch Bridge were corrected directly to NGVD 29 using the readings from the San Joaquin River gage (ANH).

The edited data were then imported into Questar Tangent and gridded using inverse distance weighted and contoured (Maps D2, A2). In addition, the software program was used to generate a shaded view image of the bathymetry data and to over lay this image on the contour map (Maps D3, D4, A3, and A4). The shaded view images highlight subtle changes in the seafloor that are often difficult to identify on the contour map.

4.3 Side Scan Sonar Data

Sidescan sonar produces an acoustic image of the seafloor that is analogous to an aerial photograph on land (Figures 2, 3 and 4). The plan view image can be used for characterizing surficial sediment (silt, sand, gravel) and detecting the presence of rock or other features such as cultural artifacts, that project above the seabed. Additionally, side scan sonar data often depicts scour zones and potential geohazards such as faults, submarine slides, or zones of subsidence.

Changes in the energy or strength of the acoustic backscatter from the seabed produces variations in the intensity of the data (darker or lighter) displayed on the graphic recorder or color monitor. Fine-grained sediments are represented by a lighter shading and coarse-grained sediment by darker shading on the image (Figures 3 and 4). Bedrock, large boulders or other features, such as sand waves or debris,, resting on the seafloor, that project upwards into the water column, produce a dark image (strong acoustic return or reflection) with a shadow (no acoustic return) which appears as a white area on the image. The bridge piers completely block the acoustic signal producing a dark reflection from the pier and a long shadow (white zone) immediately behind the pier (Figures 3 and 4).

February 13, 2007 -6- 063-1380.300

The sidescan sonar data were processed with Chesapeake SonarWiz software to generate a digital sidescan mosaic (integration of data from multiple, parallel transects, Map 11)) or a corrected image from a single transect (Map 6).

4.4 Subbottom Reflection Data

Interpreting subsurface stratigraphy, or geology, from subbottom data, uses the principal of seismic facies analysis. This method, although somewhat subjective, attempts to identify and group various reflection patterns (reflection free, uniform horizontal reflectors, discontinuous, chaotic reflectors, etc.) on the subbottom records. It is assumed that each pattern is characteristic of a particular type of sediment, geology or depositional environment. For example, a reflector pattern (geophysical facies) on the record comprised of continuous, thin layers suggests fine-grained sediment, such as clay, deposited in a low energy environment. The same pattern, but with a strong reflections (high amplitude) suggests a more compact, consolidated or stiff material. Sediments deposited in a high-energy environment usually produce very strong reflections (dark layers on the records) and the reflectors are often discontinuous. Areas of no subsurface penetration, with a dark reflection pattern, represent hard or dense material such as cobble or boulder layers or bedrock. There is often no distinct boundary between the interpreted seismic facies since stratigraphic are generally transitional in nature.

The next step is to relate the seismic facies (no internal reflections or thin layers, low reflection) to sediment type (fine-grained sediment, stiff clay, sand/gravel etc) or depositional environment (deep-water, shallow water, near shore high energy environment etc.). Information from borehole is of considerable importance for providing a final and less objective interpretation.

After identifying the seismic facies the next interpretation step is determining the depth to various reflectors or the thickness of geologic units. All reflection data (bathymetry, sidescan, subbottom seismic reflection) represents the two-way travel time, or time of flight, of an acoustic signal from the acoustic source to the point of reflection and back to the receiver. For instance, the bathymetric record displays the time for an acoustic signal to travel from the transducer to the seafloor and back to the transducer. If the velocity of sound in water is known the depth of water is found by multiplying the travel time by the velocity. On an echosounder, this is done electronically within the console and the paper record or the numerical display shows depths in feet or meters instead of milliseconds of time. The digitally acquired two-way travel time data stored on the navigation computer are converted using a simple computer program. Travel time is an absolute measurement and depth or thickness is a calculation whose accuracy depends on how well the velocity of sound is known within the medium in which it traveled.

The sediment thicknesses were determined by measuring the travel time on the seismic records for an acoustic pulse to travel from the seafloor to an underlying contact and back to the seafloor (two-way travel time in milliseconds). The two-wave travel time was multiplied by the velocity of a compressional wave in sediment to determine the thickness of a geologic unit, or depth to a reflector, in feet. A compressional velocity of 5,100 feet/second was used for this calculation.

Interpreted cross sections were then developed from the bathymetric and geophysical data for each bridge (Maps 7 and 11). The seafloor profile is generated from a section cut along the centerline of the bridges. The subsurface data are extrapolated from the geophysical subbottom data obtained on transects collected on either side of the bridge and the cross transects. In areas of insufficient data or poor data information from the borehole logs were used to fill in the information. The borehole logs were also used to provide geologic or lithologic classification.

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An example of a subbottom reflection record is presented on Figures 5 and 6. On these image colors are used to highlight the general zones of various interpreted seismic facies units. The geologic classification of the seismic facies is based on information from the soil profile provided by EMI.

The general acoustic characteristics of the seismic facies and their geologic interpretation, based on the Geology Profiles, are as follows:

• Young Bay Mud Low reflectivity, no internal bedding. Very difficult to detect on the subbottom data; low reflectivity areas often could be identified on the swath bathymetry and sidescan sonar images.

• Sand. Less continuous and lower amplitude reflectors; some diffractions and scattering of acoustic energy.

• Stiff Clay Horizontal reflectors, high amplitude reflections.

• Sand/Gravel Irregular, discontinuous, high-amplitude reflection, some diffractions.

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5.0 DATA RESULTS

5.1 Dumbarton Bridge (Maps D1-D6)

5.1.1 Bathymetry Results

The multibeam bathymetric data are presented on a contour map (Map D2), a shaded relief image (Map D3) and a map that overlays these two (Map D3).

The water depth varies from approximately + 2 feet along either end of the survey alignment to approximately -44 to -46 feet in the main channel (Map 2). The transition from shallow to deep-water is relatively rapid occurring over a horizontal distance of approximately 200 to 300 feet.

The most apparent geomorphic features on the contour map are small mounds that appear northeast of Piers 24 and 25 and southwest of Piers 20 to 23. These mounds have approximately 3 to 4 feet of relief and tend to be elongated in the NW-SE direction. The dimension of the long axis is approximately 150 feet and the short axis approximately 50 to 75 feet. On the shaded image map, which displays very subtle changes in relief, similar but smaller mounds can be observed northwest and southeast of all of the Piers. These mounds are assumed to be depositional features resulting from the hydrodynamics of current flow around the piers.

There are two semi-circular areas, that appear to be depressions (northeast corner of Pier 23, and adjacent to Pier 24) and several southwest-northeast oriented linear features (Piers 19, 20 and 21).

These are acoustic artifacts resulting from the lack of data possibly due to turbidity or entrapment of air in the water column around the piers, or turbidity immediately adjacent to the face of the transducer. It is difficult to see the affect of this data loss on the bathymetric contour map except in the two areas adjacent to the piers. The sidescan sonar data shows no evidence of depressions in this region therefore a fill-in program will be used to correct the contours in these two areas for the final report

5.1.2 Sidescan Sonar Results

An example of a sidescan sonar image from a transect located between the bridge and the small mounds south of the bridge clearly images the piers and the acoustic shadows produced by the piers (Figure 3, Map D6). Also shown on this acoustic image, between Piers 20-21, 21-22 and 22-23 are small, dark, linear features. These are interpreted to be miscellaneous debris, possibly pipes or cables lying on the seabed.

Because of errors in the navigation data that were archived with the digital sidescan data it was not possible to produce a complete mosaic for this bridge (the field records are clear images although uncorrected were unaffected). However, the corrected sidescan sonar image clearly shows details of the seafloor adjacent to the bridge and the entire area between all of the piers. Efforts are being made, using a new processing program to incorporate several of the other sidescan sonar record in order to produce a larger mosaic.

5.1.3

February 13, 2007 -9- 063-1380.300

Subbottom Results

The seismic/geologic profiles (Map D6) are a composite of information interpreted from seismic reflection data obtained on transects located adjacent to the bridge and subbottom data from several cross lines. The interpreted subsurface information is plotted on a seafloor profile generated from the bathymetric contours located along the centerline of the bridge. The soil and geologic classification is based on information presented on the EMI soil profile.

The Young Bay Mud is found predominantly on the shallow water shelf on either end of the transects.

This soil over lays a sand deposit interpreted to vary in thickness from approximately 20 to 60 feet with the thicker material located near the NE and SW end of the profile.

The sand deposit overlays a thick sequence of horizontally stratified material that in the boreholes is identified as stiff clay. The relatively high amplitude signals (dark reflection patterns) suggest that these are relatively rigid or stiff material.

The deepest reflector corresponds with a dense sand and gravel material identified in three of the boreholes (Pier 17, 20 and 23 boreholes). The contact between the top of this unit and the overlying clay is more pronounced on the southwest end of the profile (Figure 5). In this area (see between P- 19 and P-20, at 80ms depth) the horizontal reflectors transition to discontinuous, arcuate patterns suggesting an irregular surface.

5.2 Antioch Bridge (Maps A1-A6)

5.2.1 Bathymetry Results

The multibeam bathymetric data are presented on a contour map (Map A2), a shaded relief image (Map A3) and a map composed of these latter two (Map A4).

The water depth varies from approximately -12 feet at the northern end of the survey alignment to approximately -44 to -46 feet in the main channel. The dredged shipping channel is located between Piers 19 and 20, toward the northern end of the alignment

The most apparent geomorphic features on the contour map are the ridges that extend towards the west from each of the piers. These are interpreted to be small depositional ridges that develop as a result of the hydrodynamic of the current flow around the piers.

A second noticeable bathymetric pattern are the narrow linear features, oriented north-south, that parallel the bridge. These geomorphic features, which are very evident on the shaded relief maps, are interpreted to be sand waves (A3 and A4). The dark ridges are the crest of the sand wave and the reflection free areas (very light return) are the troughs

In addition, a zone indicative of potentially limited bathymetric data can be seen to the right of Pier 19 (north sides) and to the left of Pier 20 (south side). The contour map shows a small depression in these two areas. The sidescan sonar data, obtained on a transect that runs between these two piers, suggests that small depressions are present in these two areas.

5.2.2

February 13, 2007 -10- 063-1380.300

Sidescan Sonar Results

An example of sidescan sonar data obtained along the west side of the Antioch Bridge clearly images the piers and the acoustic shadows behind the piers (Figure 4). Also shown on this plan view image are the linear features that are evidence of sand waves

On the sidescan sonar mosaic the linear sand wave are the most pronounced feature. However, the piers and east-west ridges are very subtle. The shadows produced by the Piers, that are very evident when imaging from only one side (Figure 4), are filled-in by the mosaic process which looks at the piers from both sides and merges the two images. The east-west trending ridges are difficult to detect because they are imaged down their long axis (a small target) whereas the sand waves are imaged across their long axis.

5.2.3 Subbottom Reflection Results

The seismic/geologic profile (Map A6) is a composite of information interpreted from several seismic reflection profiles located adjacent to the bridge and several of the cross line transects. The subsurface interpretations were extrapolated to a profile of the seafloor made along the centerline of the bridge. The soil and geologic classification is based on information presented on the EMI soil profile

There was little evidence of Young Bay Mud in this area. The seafloor is predominantly mantled with a relatively thick sand deposit which, on the surface, has been formed into a series of sand waves. The shallow reflection horizons between the upper sand unit and underlying clay unit, located on the southern half of the profile (A-A’) were not as well defined in this area. In the lower clay unit (54 ms travel time) the horizontal bedding is well defined.

The strongest and most continuous reflection is from the top of the lower dense sand/gravel unit.

This reflector becomes increasingly deeper to the north. The gravel unit rests on a stiff clay unit that can be seen on the southern end of the profile at a depth of 80ms

Hydrographic Surveys in San Francisco Bay, CA.

Introduction:

CRA-NW was selected to perform a bathymetric survey on two bridges located in San Francisco, California. This survey was to determine the current bottom conditions at that time.

Methodology:

The bathymetry data was collected using a state-of-the-art multi beam automated hydrographic system. The Reson SeaBat 8124, also called a multi beam system, collects data in a swath configuration. This gives a higher resolution and larger data set compared to a single transducer echo sounder. This system consists of a single transducer multi beam array. Coupled with a motion sensor, heading sensor, DGPS positioning system, and velocimeter. The complete system produces accurate depth measurements (IHO standards) over a 120 degree swath. The motion sensor accurately tracks the sonar beam in addition it will also correct for the DGPS antenna movement that is mounted directly over the swath transducer thereby reducing offset induced errors. This data set was then reduced for heave, pitch, and roll along with a sound velocity and a tide table corrections. This data is then contoured and sunlit (3D) for further validity.

Project Limitations:

This survey was a straight forward hydrographic survey. There were no obstructions in the survey area other than the two bridges themselves (Dumbarton & Antioch). Weather was cool, some winds (5-20 mph), and no local boat wake noise. Data was collected along bridge azimuth for the swath data and then again normal to the first data set for the sub-bottom data acquisition.

Deliverables:

A contour chart of the depth data along with the x,y,z data set was sent to Golder Associates.

Field Activity:

1st Survey (Dumbarton Bridge)- Dec. 06 - 07, 2006- Mobilization to the project site.

Dec. 08 - 09, 2006- Began data acquisition.

Jan. 02 - 03, 2007- Begin data editing and processing.

Jan. 03, 2007- Sent XYZ ASCII data file via email.

Jan. 31, 2007- Report sent to client via mail/email.

2ne Survey (Antioch Bridge)- Dec. 06 - 07, 2006- Mobilization to the project site.

Dec. 10, 2006- Began data acquisition.

Jan. 02, 2007- Begin data editing and processing.

Jan. 03, 2007- Sent XYZ ASCII data file via email.

Jan. 31, 2007- Report sent to client via mail/email.

Personnel:

Senior Hydrographer- K. Craig Keener AK. RLS / ACSM of CRA-NW.

Junior Hydrographer- Alex Howden of CRA-CAN.

Equipment:

The following equipment or equivalent will be provided:

1. Reson 8124 swath sounding system with 1.5 degree, extended range, and side scan options.

2. HySweep acquisition software.

3. AML SVPlus velocimeter.

4. SeaTex MRU-5 motion sensor (heave, pitch, roll)

5. SG Brown Meridian Surveyor Gyro Compass or KVH 1000AC digital compass.

BATHYMETRY SURVEY

in

San Francisco Bay Area for

Condition Survey Report

CRA-NW

Date: January 31, 20126 Ballinger Way NE #117 Job# 06060

Seattle, Wa. 98155 File: R06060a_gai

425.673.2518 ph.

425.609.0031 fx.

6. Coastal Oceanographics HySweep logging system (‘windows’ based).

7. CRA-NW CatNav Navigation system (‘windows’ based).

8. CRA-NW CatBox binning/editing software (‘windows’ based).

9. Trimble Ag132 12 channel GPS receiver w/USCG or Omnistar correctors.

10. Optional: Endeco 1029 automated tide gauge.

11. 25' R/V Data Cat survey vessel with truck.

Horizontal Datum:

A Trimble Ag132 with OmniStar differential correctors was used for real time positioning of the vessel. All data was collected in NAD-83 California State Plane North zone #0402 with coor-dinates in US survey feet.

Vertical Datum:

The vertical datum was MLLW for Dumbarton and NGVD for Antioch.

Velocity Profile:

Available upon request.

Tide Data:

Available upon request.

Figure 1. Vdatum conversion

7.173 – 5.9496 = 1.2234 difference in meters between MLLW and NGVD vertical control

Therefore 1.2234 = 4.0138 feet of difference between the MLLW surface points and the new surface points translated into NGVD.

FIGURES

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FIGURE 3

EXAMPLE OF SIDESCAN SONAR DATA

FROM DUMBARTON BRIDGE

EMI/ANTIOCH & DUMBARTON GEOPHYS/CA

0631380300fig02.fh11 | Mod: 01/31/07 | AMP

West East P-18 P-19 P-20 P-21 P-22 P-23 P-24 P-25

Acoustic Shadow Behind Bridge Pier

Plan View Image Made From South Side of Bridge Looking North ft

Pier

Golder Associates0631380300fig03.fh11 | Mod: 01/31/07 | AMP

FIGURE 4

EXAMPLE OF SIDESCAN SONAR DATA

FROM ANTIOCH BRIDGE

EMI/ANTIOCH & DUMBARTON GEOPHYS/CA

South North P-9 P-11 P-12 P-14 P-15 P-16 P-19

Acoustic Shadow Behind Bridge Pier ft

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Sand Waves

Plan View Image Made Along West Side of Bridge Looking East

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13-1

Earth Mechanics, Inc.

Geotechnical & Earthquake Engineering

13.0 APPENDIX F, LABORATORY TEST RESULTS