AC Transit East Bay Bus Rapid Transit Projectin Alameda County
Final Environmental Impact Statement/Environmental Impact ReportPursuant to
National Environmental Policy Act of 1969, 102 (42 U.S.C. 4332); Federal Transit Laws (49 U.S.C. 5301(e), 5323(b) and 5324(b)); National Historic Preservation Act of 1966, 106 (16 U.S.C. 470f); 40 CFR Parts 1500-1508; 23 CFR Part 771; Executive Order 12898
(Environmental Justice); and California Environmental Quality Act, PRC 21000 et seq.; and the State of California CEQA Guidelines, California Administrative Code, 15000 et seq.
by the U.S. Department of Transportation/Federal Transit Administrationand the Alameda Contra Costa Transit District
Geologic AssessmentAddendum
December 2010
DRAFT
GEOLOGIC ASSESSMENT ADDENDUM
AC TRANSIT EAST BAY BRT EIS/R ALAMEDA COUNTY, CALIFORNIA
Prepared for:
KIMLEY-HORN AND ASSOCIATES, INC.
Submitted by:
AGS, INC.
DECEMBER 2010
AGS, Inc., 5 Freelon Street, San Francisco, CA 94107
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KI0807 Geologic Assessment Addendum 2010.doc
This addendum presents the results of a review of the Geologic Assessment conducted
for the AC Transit East Bay BRT project in 2005. Some of the main points from the
Geologic Assessment are as follows:
The project corridor is located in a seismically active region, which has been subjected to several strong earthquakes during historic time; however, no active faults are known to cross the project corridor. The Hayward Fault lies between 0.4 and 4.3 miles (0.64 and 7.0 kilometers) northeast of the project corridor, closest at both the northern and southern ends, and dominates the seismic hazard due to its proximity. The other major active faults, which could cause significant shaking of the project area, are the San Andreas, Concord, Calaveras, Rodgers Creek, and San Gregorio Faults.
The Mmax is the largest earthquake that a given fault is calculated to be capable
of generating and the controlling Mmax that could affect the project area would be a magnitude 7.1 event occurring along the Hayward-Rodgers Creek Fault at approximately 0.64 kilometers from the project corridor. The duration of strong shaking from this earthquake would be approximately 15 to 25 seconds with a predominant period of approximately 0.25 to 0.35 seconds at the ground surface. Correlations between distance from a causative fault and mean values of the peak bedrock accelerations and the effects of local soil conditions on peak ground accelerations result in mean peak ground surface accelerations within the project area ranging from 0.50 to 0.60 g for the controlling Mmax event on the Hayward Fault.
Reported groundwater levels along the project corridor ranged from depths of 4
to 30 feet below the ground surface, with an average depth of about 8 to 11 feet below the ground surface. The project corridor area south of Lake Merritt and the portion of East 14th Street (International Boulevard) at 13th Avenue, which is underlain by artificial fill, is considered to have a high susceptibility to liquefaction. All other portions of the project corridor are considered to have low to moderate susceptibility to liquefaction due to the density of granular subsurface materials or the presence of stiff cohesive soils. The consequences of liquefaction could include seismically-induced settlements, additional lateral loads on piles/piers, downdrag forces on pile/pier foundations, localized lateral deformation of fills, and flotation (buoyancy) of underground structures (i.e., tanks, pipelines and manholes) underlain by the potentially liquefiable soils.
Because the project corridor is located in a relatively flat area, the seismically-
induced landslide potential is considered to be relatively low.
The majority of the uppermost materials along the project corridor predominantly consist of clay and silt mixtures with some sand. Localized clayey soils within the
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KI0807 Geologic Assessment Addendum 2010.doc
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project corridor area are likely to be moderately expansive. Expansive soils may cause differential settlement, cracking, and deterioration of roadway pavements.
Available data indicates that the majority of soils along the project corridor are
suitable for support of light structures; however, uncontrolled fill material and bay mud are not suitable for support of foundations.
The Geologic Assessment was conducted based on reference material available at
that time. Additional, more current, material may be available now; however, this is
not anticipated to change the information presented in the report. Therefore, no
revisions to the Geologic Assessment are warranted at this time.
DRAFT
GEOLOGIC ASSESSMENT FINAL REPORT
AC TRANSIT EAST BAY BRT EIS/R ALAMEDA COUNTY, CALIFORNIA
Prepared for:
KIMLEY-HORN AND ASSOCIATES, INC.
Submitted by:
AGS, INC.
SEPTEMBER 2006
AGS, Inc., 5 Freelon Street, San Francisco, CA 94107
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AGSTABLE OF CONTENTS
SUBJECT PAGE
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1.0 INTRODUCTION .......... .............. ............................................................................ 1
2.0 EXISTING CONDITIONS ............ ............................................................................ 4
2.1 SURFACE CONDITIONS AND TOPOGRAPHY .............................................. 4
2.1.1 BERKELEY SEGMENT ..................................................................... 5
2.1.2 NORTHERN TELEGRAPH SEGMENT ............................................. 5
2.1.3 SOUTHERN TELEGRAPH SEGMENT ............................................. 6
2.1.4 DOWNTOWN OAKLAND SEGMENT ............................................... 6
2.1.5 LAKE MERRITT SEGMENT .............................................................. 6
2.1.6 NORTHERN INTERNATIONAL BOULEVARD SEGMENT ............... 6
2.1.7 SOUTHERN INTERNATIONAL BOULEVARD SEGMENT ............... 7
2.1.8 BAYFAIR EXTENSION SEGMENT ................................................... 7
2.2 AREAL GEOLOGY .............. ............................................................................ 7
2.2.1 CRETACEOUS AND JURASSIC PERIOD FRANCISCAN
COMPLEX AND ASSOCIATED ROCKS ............................................. 8
2.2.2 QUARTERNARY PERIOD DEPOSITS .............................................. 8
2.2.2.1 ALAMEDA FORMATION .................................................. 9
2.2.2.2 OLDER BAY MUD .......................................................... 10
2.2.2.3 MERRITT SAND MEMBER OF THE
SAN ANTONIO UNIT ....................................................... 10
2.2.2.4 YOUNGER BAY MUD ...................................................... 11
2.2.2.5 TEMESCAL UNIT ............................................................. 11
2.2.2.6 ARTIFICIAL FILL .............................................................. 12
2.3 SUBSURFACE SOIL CONDITIONS .............................................................. 12
2.3.1 BERKELEY - SEGMENT .................................................................... 13
2.3.2 NORTHERN TELEGRAPH SEGMENT .............................................. 14
2.3.3 SOUTHERN TELEGRAPH SEGMENT .............................................. 16
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2.3.4 DOWNTOWN OAKLAND SEGMENT ................................................ 17
2.3.5 LAKE MERITT SEGMENT ................................................................. 18
2.3.6 NORTHERN I NTERNATIONAL BOULEVARD SEGMENT ............... 19
2.3.7 SOUTHERN INTERNATIONAL BOULEVARD SEGMENT ................ 20
2.3.8 BAYFAIR EXTENSION SUMMIT........................................................ 21
2.4 GROUNDWATER .............. .......................................................................... 22
2.5 FAULTS AND SEISMICITY . .......................................................................... 23
2.5.1 MAXIMUM CAPABLE EARTHQUAKE ............................................ 25
2.5.2 SEISMIC HAZARDS........................................................................ 26
2.5.2.1 FAULT RUPTURE............................................................ 26
2.5.2.2 GROUND SHAKING ........................................................ 26
2.5.2.3 LIQUEFACTION ............................................................... 26
2.5.2.4 SEISMICALLY INDUCED LANDSLIDES ......................... 27
2.6 OTHER GEOLOGIC HAZARDS..................................................................... 27
2.6.1 EXPANSIVE SOILS......................................................................... 27
2.6.2 SETTLEMENT...... .......................................................................... 28
2.6.3 FOUNDATION CONDITIONS ......................................................... 30
3.0 CLOSURE .............. .............. .......................................................................... 31
4.0 REFERENCES CITED . .............. .......................................................................... 32
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TABLES
TABLE 1 HISTORICAL EARTHQUAKES ........................................ 24
TABLE 2 FAULT SEISMICITY ......................................................... 25
PLATES
PLATE 1 PROJECT CORRIDOR MAP
