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4.5 Geology and Soils
4.5 GEOLOGY AND SOilS
This section of the MEIR describes existing geology, soils, and seismic conditions on the MEIR Study
Area and analyzes the potential physical environmental effects related to seismic hazards and erosion.
The MEIR evaluated the environmental impacts related to geology and soils based upon information
from a variety of sources including, the City of South San Francisco General Plan, the East of 101 Area
Plan, the 2006FMPU, as well as previously published information from the u.S. Geological Survey and
the California Geological Survey [(CGS), formerly California Division of mines and Geology (CDMG)].
Full bibliographic entries for all reference materials are provided in Section 4.5.4 (References) of this
section.
No comment letters related to geology and soils were received in response to the December 9, 2005
Revised Notice of Preparation (NOP) circulated for the project. In addition, no comments were received
at the public scoping meeting held January 17, 2006. The NOP and comment letters are included in
Appendix A of this MEIR.
4.5.1
Existing Conditions
Regional Geology
The geology of the San Francisco Bay Area includes three geologic provinces: The Salinian block, the
Franciscan complex, and the Great Valley sequence (Figure 4.5-1 [Regional Geology and Faults]). The
Salinian block is west of the San Andreas Fault. It is composed primarily of granitic plutonic rocks, which
are similar to those found in the Sierra Nevada and are believed to be rocks of the Sierra Nevada
batholith that have been displaced along the San Andreas Fault. East of the San Andreas Fault, and
bounded on the west by the Hayward Fault, is the Mesozoic Franciscan complex. Franciscan rocks
represent pieces of former oceanic crust that have accreted to North America by subduction and
collision. These rocks are primarily deep marine sandstone and shale. Chert, marble, serpentinite, and
limestone are also found in the assemblage. The rocks of the Franciscan complex are prone to landslides.
East of the Hayward Fault is the Great Valley Sequence. In the San Francisco Bay area, this sequence is
mainly composed of Cretaceous and Tertiary marine sedimentary rocks. Like the Franciscan assemblage,
the rocks of the Great Valley Sequence are also prone to landsliding.
Local Geology/Soil Types and Characteristics
The MEIR Study Area is on the west shore of San Francisco Bay on reclaimed bay lands and adjacent
uplands at the eastern base of San Bruno Mountain. Elevations range from 182 feet above mean sea level
(MSL) at the top of San Bruno Hill to approximately 0 feet MSL at the low-lying areas in the northeast
portion of the MEIR Study Area (USGS 1956). The lower portion of the MEIR Study Area was
reclaimed from the waters of the San Francisco Bay in the mid to late 1960's by using well compacted
materials derived primarily from excavations consisting of the Bedrock belonging to the Franciscan
complex, alluvial material and Bay Mud lie directly beneath the reclaimed fill material. In this area, the
Genentech Corporate Facilities Master EIR
4.5-1
Cenozoic Cover
Franciscan Complex
Great Valley Sequence
Salinian Block
Geologic Faults
FIGURE 4.5-1
Regional Geology and Faults
4.5 Geology and Soils
Franciscan complex consists primarily of sandstone and shale. The Bedrock Alluvial units consisting of
medium stiff to hard, green, gray-green, and brown sandy and silty clay and medium dense to dense silt,
silty sand, and sand unconformably overlie the bedrock surface. Borings at several building sites have
shown that shearing has obscured bedding relations in the sandstone, and much of the shale has been
sheared to gouge-like materials. Figure 4.5-2 (Local Geology and Stratigraphy) further illustrate the
geology and soil structure associated with the MEIR Study Area.
Seism icity
The City of South San Francisco is located in one of the most seismically active regions in the United
States, with approximately thirty known faults in the Bay Area capable of generating earthquakes; eleven
of these faults are located within 40 miles of South San Francisco. The San Andres Fault system, the
general boundary between the northward moving Pacific Plate (west of the fault) and the southward
moving North American Plate (east of the fault) is the dominate fault of the region and the entire state of
California. The fault system movement is distributed across a complex system of generally strike-slip,
right lateral parallel and subparallel faults including, but not limited to, the regional San Andreas, San
Gregorio, Hayward, Rogers Creek and Calaveras Faults. As shown in Figure 4.5-1 Regional Geology and
Faults, the Peninsula Segment of the San Andreas at approximately 7 kilometers (km) to the southwest,
and the Seal Cove Segment of the San Gregorio Fault, at approximately 14 km to the west-southwest, are
the two closest to the MEIR Study Area. It should also be noted that branches of the Hillside Fault have
been mapped a very short distance southwest of the MEIR Study Area; however, there is no evidence
that this fault has been active within the geologically recent time.
Based on criteria established by the California Geological Survey (CGS), faults may be categorized as
active, potentially active, or inactive. Active faults, such as the San Andreas and San Gregorio, are those
that show evidence of displacement within the last 11,000 years (historically active faults are those that
have shown evidence of displacement during the last 200 years); potentially active faults are those that
show evidence of displacement during the last 1.6 million years. Faults showing no evidence of
displacement within the last 1.6 million years, such as the Hillside Fault, are considered inactive for most
purposes.
Historic and Future Seismicity
The severity of an earthquake generally is expressed in two ways-magnitude and intensity. The energy
released, measured on the Moment Magnitude (MW) scale, represents the "size" of an earthquake. The
Richter Magnitude (M) scale has been replaced in most modern building codes by the MW scale because
the MW scale provides more useful information to design engineers. The intensity of an earthquake is
measured by the Modified Mercalli Intensity (MMI) scale, which emphasizes the current seismic
environment at a particular site and measures groundshaking severity according to damage done to
structures, changes in the earth surface, and personal accounts. Historically, seismicity for the Bay region
is associated with the strike-slip faults of the San Andreas Fault System. Fourteen earthquakes of a
moment magnitude (MW) 6.0 or greater have occurred in the Bay Area in historic times. Earthquakes of
this magnitude pose significant groundshaking hazards to the MEIR Study Area.
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4.5-3
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FIGURE 4.5-2
Local Geology and Stratigraphy
Source:
ErR Study Area
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4.5 Geology and Soils
Of the many seismic events, there have been four significant quakes:
. On October 21, 1868, there was a quake that registered as an ML6.8 on the Richter Local
Magnitude scale. This quake occurred on the southern Hayward Fault. Heavy damage was
sustained in towns along the Hayward Fault in the eastern Bay Area, as well as in San Francisco
and San Jose. Reported damage extended from Gilroy and Santa Cruz in the south to Santa Rosa
in the north.
. On March 31,1898, the San Francisco Bay region was shaken by another earthquake that appeared
to be centered near Mare Island in San Pablo Bay. This earthquake caused disturbances in the Bay
that were reported as a "tidal wave."
. On April 18, 1906, the Great San Francisco Earthquake of 1906 occurred with a moment
magnitude (MW) of 7.9. The epicenter was off the Pacific coast of the San Francisco Peninsula
(formerly estimated to be near Olema), and was arguably the most destructive earthquake to have
occurred in Northern California in historical times. It ruptured the San Andreas Fault from San
Juan Bautista to Cape Mendocino. Damage was widespread in Northern California and injury and
loss of life was particularly severe. Groundshaking and f1te caused the deaths of more than 3,000
people and injured approximately 225,000. Damage from shaking was most severe in areas of
saturated or loose, young soils. Liquefaction was reported throughout the Bay Area.
. On October 17,1989, the MW 6.9 Loma Prieta earthquake occurred on the southern Santa Cruz
segment of the San Andreas Fault. The cities of Los Gatos, Watsonville, and Santa Cruz were hard
hit with damage, as were San Francisco and Oakland. Shaking was felt throughout the Bay Area.
Damage to major transportation facilities included the collapse of the 1-880 Cypress structure (with
the loss of several dozen lives), liquefaction and settlement damage to Port facilities in Oakland,
and the runway apron at Oakland International Airport, and temporary closure of the Oakland-Bay
Bridge. As in the 1906 earthquake, the worst damage from shaking occurred at structures on
unconsolidated or saturated soils.
Table 4.5-1 (potential Activity on Major Active Bay Area Faults) contains the estimated maXllnum
parameters for earthquakes on known major Bay Area faults that have the potential to affect the
proposed project area. In addition, Figure 4.5-3 (Bay Area Earthquake Probability) shows the percent
chance that Bay Area faults will generate an MW of 6.7 or larger earthquake between the years 2003 and
2032. The two active faults with the highest potential to effect the MEIR Study Area, the San Andreas
and Hayward, have 21 percent and 27 percent chances, respectively, to produce such a quake by 2032.
All together, the Bay area has a 62 percent chance of producing one or more such quakes by 2032, each
of which would affect the MEIR Study Area.
San Andreas 7.9 1906 24 +/- 5 0
San Gregorio 7.7 Holocene 7 +/- 3 7
Hayward 7.1 1868 (currently creeping) 9 +/- 2 14
Calaveras 7.5 Holocene (part in 1851) 15 +/- 3 25
Rodgers Creek 7.1 Holocene 9 +/- 2 34
SOURCE: Working Group on California Earthquake Probabilities (1999); Working Group on Northern California Earthquake Potential (1996).
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4.5-5
Chapter 4 Environmental Analysis
Seismic Hazards
Groundshaking
The major cause of structural damage from earthquakes is groundshaking. The intensity of ground
motion expected at a particular site depends on the magnitude of the earthquake, the distance of the site
to the epicenter and the geology of the area between the epicenter and the site. Greater movement can
be expected at sites on poorly consolidated materials, such as alluvium, or compressible materials such as
Bay Mud or un-engineered fill. Sites in close proximity to the causative fault, or seismic events of
extraordinary magnitude may also cause damage from groundshaking. The Association of Bay Area
Governments (ABAG) has produced earthquake intensity maps that indicate the scenario earthquake
listed for the entire San Andreas Fault (1906-sized earthquake) would produce a "Violent" shaking at the
site, wile the Peninsula Segments of the San Andreas, or the San Gregorio Fault, would produce a "Very
Strong" shaking intensity at the site. Table 4.5-2 presents the earthquake magnitudes, distance to various
faults from the site and the anticipated shaking intensity as a result of the scenario earthquakes potentially
affecting the site.
Entire San Andreas (1906)
San Andreas (Peninsula Segment)
San Gregorio (North)
Hayward (North & South)
SOURCE: Association of Bay Area Governments, 2003
7
7
14
24
7.9
7.2
7.3
7.3
IX- Violent
VIII-Very Strong
VIII-Very Strong
VII-Strong
Liquefaction
Soil liquefaction is a phenomenon in which saturated (submerged) cohesionless soils can be subject to a
temporary loss of strength due to buildup of excess pore pressure, and reduction of soil effective stress
during cyclic loading, such as those produced by earthquakes. In the process, the soil acquires mobility
sufficient to permit both the horizontal and vertical movements, if not confined. Soils most susceptible
to liquefaction are loose, clean saturated, uniformly-graded fine sands. Silty sands and clayey sands may
also be susceptible to liquefaction during strong groundshaking, although to a lesser extent. Loose to
medium dense sand layers can also be subjected to seismic compaction if they are above the water table.
In addition to the necessary soil conditions, the ground acceleration and duration of the earthquake must
be of a sufficient level to initiate liquefaction. Based upon the 2001 ABAG Liquefaction Hazard Map, the
MEIR Study Area has a high potential for liquefaction, specifically in the northeastern areas of the site
that consist of fill material overlying Bay Mud.
4.5-6
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4.5 Geology and Soils
Seismically Induced Settlement
Settlement occurs in areas prone to different rates of ground surface sinking and densification
(differential compaction), and are underlain by sediments that differ laterally in composition or degree of
existing compaction. Differential settlement can damage structures, pipelines and other subsurface
entities.
Strong groundshaking can cause soil settlement by vibrating sediment particles into more tightly
compacted configurations, thereby reducing pore space. Unconsolidated, loosely packed alluvial deposits
and sand are especially susceptible to this phenomenon. Poorly compacted artificial fills may experience
seismically induced settlement.
Subsidence and Expansive and Collapsible Soils
Subsidence involves a sudden sinking or gradual settling and compaction of soil and other surface
material with little or no horizontal motion.
Expansive soils have a significant amount of clay particles that can give up water (shrink) or take on
water (swell). The change in volume exerts stress on buildings and other loads placed on these soils. The
occurrence of these soils is often associated with geologic units having marginal stability. Expansive soils
can be dispersed widely, found in hillside areas as well as low-lying areas in alluvial basins. Soils testing to
identify expansive characteristics and appropriate mitigation measures are required routinely by grading
and building codes.
Collapsible soils undergo a rearrangement of their grains, and a loss of cementation, resulting in
substantial and rapid settlement under relatively low loads. Collapsible soils occur predominantly at the
base of mountain ranges where Holocene-age alluvial fan and wash sediments have been deposited
during rapid run-off events. Soils prone to collapse are commonly associated with man-made fill, wind-
lain sands and silts, and alluvial fan and mudflow sediments deposited during flash floods. During an
earthquake, even slight settlement of fill materials can lead to a differentially settled structure and
significant repair costs. Differential settlement of structures can occur when heavily irrigated landscape
areas are near a building foundation. Examples of common problems associated with collapsible soils
include tilting floors, cracking or separation in structures, sagging floors, and nonfunctional windows and
doors.
Due to the presence of significant amounts of artificial fill materials placed over soft Bay Mud, as well as
the shallow water table (borings have indicated that the water table may be as shallow as 6 feet, with the
potential of groundwater at near zero elevation at mean sea level), the potential for subsidence and/or
expansive and collapsible soils is considered high for the MEIR Study Area.
Landsliding
Landslides are the downward sliding of a mass of earth and rock. Landsliding is a geological
phenomenon that includes a wide range of ground movements, such as rock falls, deep failure of slopes,
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4.5-9
Chapter 4 Environmental Analysis
and shallow debris flows. Although gravity acting on an over-steepened slope is the primary cause of
landsliding, there are other contributing factors, such as (1) erosion by rivers, glaciers, or ocean waves;
(2) rock and soil slopes that are weakened through saturation by snowmelt or heavy rains; (3) volcanic
eruptions that produce loose ash deposits, heavy rain, and/or debris flows; (4) vibrations from
machinery, traffic, blasting, and even thunder; and (5) excess weight from accumulation of rain or snow,
stockpiling of rock or ore from waste piles, or from man-made structures. The strong ground motions
that occur during earthquakes are capable of inducing landslides, generally where unstable soil conditions
already exist. As illustrated by Figure 4.5-4 (Slope), portions of the MEIR Study Area have slopes greater
than 15 percent that are underlain by weak bedrock. These areas will have a greater susceptibility to the
risks associated with landsliding.
Soil Erosion
Soil erosion is the process by which soil particles are removed from a land surface by wind, water, or
gravity. Most natural erosion occurs at slow rates; however, the rate of erosion increases when land is
cleared or altered and left in a disturbed condition. Erosion can occur as a result of, and can be
accelerated by, site preparation activities associated with development. Vegetation removal in previously
landscaped areas could reduce soil cohesion, as well as the buffer provided by vegetation from wind,
water, and surface disturbance, which could render the exposed soils more susceptible to erosive forces.
Additionally, excavation or grading may result in erosion during construction activities, irrespective of
whether hardscape previously existed at the construction site, because bare soils would be exposed and
could be eroded by wind or water. The effects of erosion are intensified with an increase in slope (as
water moves faster, it gains momentum to carry more debris), and the narrowing of runoff channels
(which increases the velocity of water). Surface improvements, such as paved roads and buildings,
decrease the potential for erosion. Once covered, soil is no longer exposed to the elements. The MEIR
Study Area currently is heavily developed with various buildings, hard pack and paved parking lots and
landscaping over fill material and exposed bedrock.
4.5.2
Regulatory Framework
Federal
National Pollutant Discharge Elimination System (NPDES) Phase I (General
Construction Activity Stormwater Permit)
As discussed in further detail in Section 4.13 (Utilities), a Stormwater Pollution Prevention Plan (SWPPP)
prepared in compliance with an NPDES Permit describes the MEIR Study Area, erosion and sediment
controls, runoff water quality monitoring, means of waste disposal, implementation of approved local
plans, control of post-construction sediment and erosion control measures and maintenance
responsibilities, and non stormwater management controls. Dischargers are required to inspect
construction sites before and after storms to identify stormwater discharge from construction activity,
and to identify and implement controls where necessary.
4.5-10
Genentech Corporate Facilities Master EIR
Chapter 4 Environmental Analysis
State
California Building Code
The Uniform Building Code (UBC) is published by the International Conference of Building Officials. It
forms the basis of approximately half of the state building codes in the United States, including
California's, and has been adopted by the state legislature together with Additions, Amendments, and
Repeals to address the specific building conditions and structural requirements in California. California
Code of Regulations (CCR), Title 24, Part 2, the California Building Code (CBC), provides minimum
standards for building design. Local codes are permitted to be more restrictive than Title 24, but are
required to be no less restrictive. Chapter 16 of the CBC addresses General Design Requirements,
including but not limited to, regulations governing seismically resistant construction (Chapter 16,
Division IV) and construction to protect people and property from hazards associated with excavation
cave-ins and falling debris or construction materials. Chapters 18 and A33 address site demolition,
excavations, foundations, retaining walls and grading, including, but not limited to, requirements for
seismically resistant design, foundation investigations, stable cut and fill slopes, and drainage and erosion
control. In addition, construction activities are subject to occupational safety standards for excavation,
shoring, and trenching as specified in Cal-OSHA regulations (CCR, Title 8).
In addition to providing standards for building design, the CBC defines and ranks different regions
within the state based upon their seismic hazard potential. There are four different seismic regions:
Seismic Zones 1 through 4, with Seismic Zone 1 having the least potential for seismic hazards, and
Seismic Zone 4 having the greatest potential for seismic hazards. The MEIR Study Area is in Seismic
Zone 4, as is about 45 percent of California. Accordingly, any future development would be required to
comply with all design standards applicable to Seismic Zone 4, the most stringent in the state.
Seismic Hazards Mapping Act
The Seismic Hazards Mapping Act became effective in 1991 to identify and map seismic hazard zones for
the purpose of assisting cities and counties in preparing the safety elements of their general plans and to
encourage land use management policies and regulations that reduce seismic hazards. The intent of this
Act is to protect the public from the effects of strong groundshaking, liquefaction, landslides, ground
failure, or other hazards caused by earthquakes. In addition, CGS's Special Publication 117, Guidelines
for Evaluating and Mitigating Seismic Hazards in California, provides guidance for the evaluation and
mitigation of earthquake-related hazards for projects in designated zones of required investigations.
Loca I
The California Building Code Vol. 1 and 2, 2001 Edition, including the California Building Standards,
2001 Edition, published by the International Conference of Building Officials, and as modified by the
amendments, additions and deletions set forth in the South San Francisco Municipal Code (SSFMC), has
been adopted as the building code of the City of South San Francisco. All building guidelines used for
the proposed project will be dictated by the City of South San Francisco Building Code.
4.5-12
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4.5 Geology and Soils
Further, in 1994 the City of South San Francisco developed the East of 101 Plan with the overall goal of
recognizing the unique character of the East of 101 Area and to guide and regulate development in a
manner which protects and enhances the area's physical, economic and natural resources, while also
encouraging appropriate development in the area. As such, the East of 101 Plan Chapter 10,
Geotechnical Safety Element, has set forth specific guidelines with respect to site treatment and building
design and the unique geological hazards of the area. The East of 101 Geotechnical Safety Element
policies are as follows:
Policy GEO-l The City shall assess the need for geotechnical investigations on a project-by project basis
on sites in areas of fill shown of Figure 17, and shall require such investigations where
needed.
Policy GEO-2 Where fill remains under a proposed structure, project developers shall design and
construct appropriate foundations.
Policy GE03 Given the extensive use of the area for industrial and waste disposal purposes,
investigation both by drilling and by examination of historic aerial photographs shall be
conducted by project developers to determine if landfills exist under the project site prior
to cons truction.
Policy GEO-4 Project developers shall design developments on landfills and dump sites to deal safely
with gas produced by the decomposition of the buried garbage. Inorganic soil capping
over landfills shall be thick enough that excavation for repair of existing utilities or
installation of additional utilities does not penetrate to buried garbage.
Policy GEO-5 If hazardous fill, such as garbage organics, is encountered it shall be appropriately
disposed by a project developer during construction. This material shall not be used for
either structural fill or grading fill. However, other uses may be possible, such as
landscaping around vegetation if the fill has a high organic content. If no acceptable use is
found on-site, the hazardous fill should be properly disposed off-site.
Policy GEO-6 Where a landfill or dump occurs under a proposed structure, project developers shall
design and construct appropriate foundations.
Policy GEO-7 New slopes greater then 5 feet in height, either cut in native soils or rock, or created by
placing fill material, shall be designed by a geotechnical engineer and should have an
appropriate factor of safety under seismic loading. If additional load is to be placed at the
top of the slope, or if extending a level area at the toe of the slope requires removal of
part of the slope, the proposed configuration shall be checked for an adequate factor of
safety by a geotechnical engineer.
Policy GEO-8 The surface of fill slopes shall be compacted during construction to reduce the likelihood
of surficial sloughing. The surface of cut or fill slopes shall also be protected from erosion
due to precipitation or runoff by introducing a vegetative cover on the slope or by other
means. Runoff from paved or other parts of the slope shall be directed away from the
slope.
Policy GEO-9 Steep hillside areas in excess of 30 percent grade shall be retained in their natural state.
Development of hillside sites should follow existing contours to the greatest extent
possible and grading should be kept to a minimum.
Genentech Corporate Facilities Master EIR
4.5-13
Chapter 4 Environmental Analysis
Policy GEO-10 In fill areas mapped on Figure 17, a geotechnical investigation to determine the true
nature of the subsurface materials and the possible effects of liquefaction shall be
conducted by the project developer before development.
Policy GEO-11 Development shall be required to mitigate the risk associated with liquefaction.
Policy GEO-12 Structural design of buildings and infrastructure shall be conducted according to the
Uniform Building Code and appropriate local codes of practice which specify
procedures and details to reduce the effects of ground shaking on structures.
Policy GEO-13 Development within the preliminary boundary of the Coyote Point hazard area, as
depicted on Figure 15, shall be reviewed by a geotechnical engineer. Fault trenching may
be required on individual development sites where feasible and determined necessary by
the engineer. No structure for human occupancy shall occur within 50 feet of identified
active faults, unless a geotechnical investigation and report determine that no active
branches of that fault underlie the surface
Policy GEO-l refers to Figure 17 of the East of 101 Area Plan, and Policy GEO-13 refers to Figure 15
of the East of 101 Area Plan; these figures are depicted in this MEIR as Figure 4.5-5 (Figure 17 of East
of 101 Area Plan) and Figure 4.5-6 (Figure 15 of East of 101 Area Plan) respectively.
Additionally, the 1999 South San Francisco General Plan Health and Safety Element contains policies
designed to minimize the risks associated with development in areas of seismic hazards. As such, the
South San Francisco General Plan, Health and Safety Element, has set forth specific guidelines with
respect to site treatment and building design and the unique geological hazards of the area. The South
San Francisco General Plan, Health and Safety Element, policies are as follows:
Implementing Policy 8.1-1-1 Do not permit special occupancy buildings, such as hospitals, schools and
other structures that are important to protecting health and safety in the
community, in areas identified in Figure 8-2.
Implementing Policy 8.1-1-2 Steep hillside areas in excess of 30 percent grade should be retained in
their natural state. Development of hillside sites should follow existing
contours to the greatest extent possible. Grading should be kept to a
rrunlmum.
Implementing Policies 8.1-1-1 and 8.1-1-2 refer to Figure 8-2 (General Plan Policies for Seismically
Sensitive Lands), of the South San Francisco General Plan, Health and Safety Element; this figure is
depicted in this MEIR as Figure 4.5-7 (General Plan Policies for Seismically Sensitive Lands).
4.5-14
Genentech Corporate Facilities Master EIR
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Chapter 4 Environmental Analysis
4.5.3
Project Impacts and Mitigation
Analytic Method
Widely available industry sources were examined to document regional and local geology (see
Section 4.5. 4 References). Information regarding regional geology and seismically induced hazards was
taken from various sources of the CGS and the United States Geological Survey (USGS). Project-specific
geologic information, soil characteristics, and liquefaction potential were obtained from the various
geotechnical investigations prepared between 2004 and 2005 for individual building projects occurring on
the MEIR Study Area. Estimated maximum earthquake magnitudes resulting from potential seismic
activity on various active faults in the area were obtained from previous environmental documentation
prepared for projects in the general vicinity. Where potential geological hazards are identified on the
MEIR Study Area, such hazards are expected to affect any potential development.
Thresholds of Significance
The following thresholds of significance are based on Appendix G of the 2006 CEQA Guidelines. For
purposes of this MEIR, implementation of the proposed project could result in potentially significant
impacts from geology and soils if the proposed project would result in any of the following:
. Expose people or structures to potential substantial adverse effects, including the risk of loss,
injury or death involving:
Rupture of a known earthquake fault, as delineated on the most recent Alquist-Priolo
Earthquake Faulting Zoning Map issued by the State Geologist for the area or based on other
substantial evidence of a known fault.
Strong seismic ground shaking.
Seismic-related ground failure, including liquefaction and landslides.
. Result in substantial soil erosion or the loss of topsoil.
. Be located on a geologic unit or soil that is unstable, or that would become unstable as a result of
the project, and potentially result in on-or off-site landslide, lateral spreading, subsidence,
liquefaction or collapse.
. Be located on expansive soil, as defined in Table 18-1-B of the Uniform Building Code (1994),
creating substantial risks to life or property.
. Have soils incapable of adequately supporting the use of septic tanks or alternate waste water
disposal systems where sewers are not available for the disposal of waste water.
4.5-18
Genentech Corporate Facilities Master EIR
4.5 Geology and Soils
Impacts and Mitigation Measures
Threshold
Expose people or structures to potential substantial adverse effects, including the
risk of loss, injury, or death involving
· Rupture of a known earthquake fault, as delineated on the most recent Alquist-
Priolo Earthquake Fault Zoning Map issued by the State Geologist for the area or
based on other substantial evidence of a known fault
· Strong seismic ground shaking
· Seismic-related ground failure, including liquefaction
· Landslides
Impact 4.5-1
Implementation of the proposed project would not expose people and/or
structures to potentially substantial adverse effects resulting from rupture
of a known earthquake fault, strong seismic groundshaking, seismic-
related ground failure (i.e., liquefaction), or landsliding. Implementation of
project requirements, PR 4.5-1(a) through PR 4.5-1 (d) would ensure the
impact would remain less than significant.
As described above, the project site is not located within an Earthquake Fault Zone as defined by the
Alquist-Priolo Earthquake Fault Zoning Act of 1994, and no known active or potentially active faults traverse
the Genentech Campus. Because ground rupture generally only occurs at the location of a fault, and no
active faults are known to traverse the MEIR Study Area, the MEIR Study Area would not be subject to
a substantial risk of fault (ground surface) ruptures. However, if evidence of an active or potentially
active fault is discovered during preparation of a site-specific geotechnical report, as required by the East
of 101 Plan, Policy Geo-13, and incorporated in the MEIR as PR 4.5-1, the report shall address the
potential hazard and provide design recommendations that shall be incorporated into the project.
Further, Genentech will retain a certified Licensed Geotechnical Engineer to prepare site-specific
geotechnical studies, as required by PR 4.5-1 (a), which will ensure that new development on the MEIR
Study Area provides an acceptable level of protection against seismic-related hazards according to
current geotechnical engineering and City standards. This impact would, therefore, be considered less
than significant.
As part of the construction permitting process, the City requires completed geotechnical reports to
identify potentially unsuitable soil conditions including liquefaction, subsidence, and collapse. The
evaluations must be conducted by registered soil professionals, and measures to mitigate for
inappropriate soil conditions must be applied, depending on the soil conditions. The design of
foundations and buildings must conform to the analysis and implementation criteria described in the
CBC, Chapters 16, 18, and A33 as described above in Subsection 4.5.2 Regulatory Framework.
Adherence to the City's codes and policies, including those outlined the East of 101 Area Plan would
ensure the maximum practicable protection available for users of the project.
Several portions of the MEIR Study Area have relatively steep slopes, and general construction activities
such as excavation and grading can create new slopes. Improper loading of fill materials, or excessive
irrigation practices may also induce slope instability or landsliding. The East of 101 Plan Geotechnical
4.5-19
Genentech Corporate Facilities Master EIR
Chapter 4 Environmental Analysis
Safety Element Policies GEO-7 through GEO-9, and incorporated in this MEIR as PR 4.5-1 (a) through
PR 4.5-1 (d), are designed specifically to mitigate the impacts associated with landsliding and unstable
slope conditions. Adherence to the City's codes and policies, including those incorporated as PR 4.5-1 (b)
through PR 4.5-1 (d), would ensure the maximum practicable protection available for users of the project
and minimize the risks associated with landsliding.
PR 4.5-1 (a)
PR 4.5-1 (b)
PR 4.5-1 (c)
PR 4.5-1 (d)
Development within the preliminary boundary 0] the Cqyote Point hazard area, as depicted on
Fzgure 150] the East 0] 101 Area Plan and referred to as Fzgure 4.5-6 in this MEIR, shall
be reviewed ~ a geotechnical engineer. Fault trenching mqy be required on individual
development sites where feasible and determined necessary ~ the engineer. No structure for
human occupanry shall occur within 50 feet 0] identified active faults, unless a geotechnical
investzgation and report determine that no active branches 0] that fault underlie the suiface.
New slopes greater then 5 feet in hezght, either cut in native soils or rock, or created ~ placing
Jill materia~ shall be deszgned ~ a geotechnical engineer and should have an appropriate factor 0]
sqfery under seismic loading. If additional load is to be placed at the top 0] the slope, or if
extending a level area at the toe 0] the slope requires removal 0] part 0] the slope, the proposed
conJiguration shall be checked for an adequate factor 0] sqfery ~ a geotechnical engineer, based on
applicable codes and professional standards,.
The suiface 0] Jill slopes shall be compacted during construction to reduce the likelihood 0]
suificial sloughing. The suiface 0] cut or Jill slopes shall also be protected from erosion due to
precipitation or runoff ~ introducing a vegetative cover on the slope or ~ other means. Runoff
from paved or other parts 0] the slope shall be directed awqy from the slope.
Steep hillside areas in excess 0] 30 percent grade shall be retained in their natural state.
Development 0] hillside sites should follow existing contours to the greatest extent possible and
grading should be kept to a minimum.
Continued compliance with the CBC as well as the applicable provisions of the Seismic Hazards Mapping
Act and following the identified Project Requirements, would ensure that this impact remains less than
significant. No mitigation is required.
Threshold
Result in substantial soil erosion or the loss of topsoil
Impact 4.5-2
The construction and operation of the proposed project would not result in
substantial soil erosion or the loss of topsoil. This is considered a less-than-
significant impact.
Erosion can occur as a result of, and can be accelerated by, site preparation activities associated with
development. Vegetation removal in landscaped (pervious) areas could reduce soil cohesion, as well as
the buffer provided by vegetation from wind, water, and surface disturbance, which could render the
exposed soils more susceptible to erosive forces. Additionally, excavation or grading for any proposed
subterranean building or parking structures may also result in erosion during construction activities,
irrespective of whether hardscape previously existed at the construction site, as bare soils would be
exposed and could be eroded by wind or water. Earth-disturbing activities associated with construction
4.5-20
Genentech Corporate Facilities Master EIR
4.5 Geology and Soils
would be temporary and erosion effects would depend largely on the areas excavated, the quantity of
excavation, and the length of time soils are subject to conditions that would be affected by erosion
processes. In addition, all construction activities would comply with Chapter 18 of the CBC, which
regulates excavation activities and the construction of foundations and retaining walls, and Chapter 33 of
the CBC, which regulates grading activities, including drainage and erosion control. As stated in
Section 4.3 (Air Quality), Genentech would continue to implement dust control measures consistent with
BAAQMD Rules regarding fugitive dust, which would stabilize soils and prevent erosion through the
reduction of dust generation by up to 85 percent. Additionally, as stated in Section 4.13 (Utilities),
Genentech would continue to comply with the NPDES general permit for construction activities,
pursuant to which, as part of an erosion control plan, construction site erosion and sedimentation
control BMPs would be implemented and would include such measures as silt fences, watering for dust
control, straw bale check dams, hydro s eeding, and other measures. Further, Genentech would be
required to comply with all applicable provisions of the San Mateo Countywide Stormwater Pollution
Program (STOPPP), and will require runoff management programs that would include BMPs to control
erosion and sedimentation. Therefore, substantial erosion is unlikely to occur on an operational basis,
and this impact would be considered to be less than significant. No mitigation is required.
Threshold
Be located on a geologic unit or soil that is unstable, or that would become unstable
as a result of the project, and potentially result in on- or off-site landslide, lateral
spreading, subsidence, liquefaction or collapse
Impact 4.5-3
The proposed project would not expose people or structures to on-site or
off-site landslides, lateral spreading, ground subsidence, liquefaction, or
collapse. Implementation of project requirements PR 4.5-2( a) and 4.5-2 (b)
would ensure this impact remains less than significant.
The Lower Campus of the proposed project is composed of fill soils which were placed over wetlands
and Bay Mud during the last century. Using unsuitable soils, such as improperly compacted fill material,
would have the potential to create future liquefaction, subsidence, or collapse problems leading to
building settlement and/ or utility line disruption. When weak soils are re-engineered specifically for
stability prior to use, these potential effects can be reduced or eliminated. An acceptable degree of soil
stability would be achieved for expansive, liquefaction-prone, and compressible soils by the required
incorporation of soil treatment programs (replacement, grouting, compaction, drainage control, etc.) in
the excavation and construction plans to address site-specific soil conditions. A site-specific evaluation of
soil conditions is required by the East of 101 Plan Geotechnical Safety Element Policies GEO-l through
2, and incorporated as PR 4.5-2(a) and PR 4.5-2(b), and must contain recommendations for ground
preparation and earthwork specific to the site, that become an integral part of the construction design.
PR 4.5-2(a)
The City shall assess the need for geotechnical investigations on a prqject-~ prqject basis on sites
in areas of Jill as depicted on the East of 101 Area Plan, Fzgure 1 7 and referred to as Fzgure
4.5-7 in this MEIR, and shall require such investzgations where needed.
PR 4.5-2(b)
Where Jill remains under a proposed structure, prqject developers shall design and construct
appropriate foundations.
Genentech Corporate Facilities Master EIR
4.5-21
Chapter 4 Environmental Analysis
As part of the construction perrmtt1ng process, the City requires completed geotechnical reports to
identify potentially unsuitable soil conditions including liquefaction, subsidence, and collapse. The
evaluations must be conducted by registered soil professionals, and measures to eliminate inappropriate
soil conditions must be applied, depending on the soil conditions. The design of pilings support must
conform to the analysis and implementation criteria described in the CBC, Chapters 16, 18, and A33.
Adherence to the City's codes and policies and following the identified Project Requirements would
ensure the maximum practicable protection available for users of the project and would result in a less-
than-significant impact. No mitigation is required.
Threshold
Be located on expansive soil, as defined in Table 18-1-B of the Uniform Building Code
(1994), creating substantial risks to life or property
Impact 4.5-4
Implementation of the proposed project would not result in construction of
facilities on expansive soils, and would not create a substantial risk to
people and structures. This is considered a less-than-significant impact.
As stated Subsection 4.5.1 (Existing Conditions), bedrock belonging to the Franciscan complex, alluvial
material and Bay Mud are all found on the MEIR Study Area. Soil expansion potential, therefore, varies
across the MEIR Study Area and can affect structures constructed on such soils, as water uptake after
rainfall could cause soils to expand and damage building foundations, which may compromise the
stability of the structures that underlie the affected foundations. However, all construction on the MEIR
Study Area would be required to comply with applicable provisions of Chapter 23 of the CBC or Zone 4
of the UBC, and would be subject to structural peer review. Compliance with applicable regulations
would ensure that impacts related to expansive soils are less than significant by identifying site-specific
soils characteristics and constraints and designing structures and foundations to address such constraints.
Such recommendations could include design features, such as expansion joints in structures, mounting
foundations on concrete piles, or replacing existing soils on a project site with stable fill material, and
would either result in a structure that could withstand soils expansion or a building pad substrate that
would not be subject to expansiveness. Identification of expansive soils before construction and
implementation of appropriate design measures would ensure that foundations and structures would
provide an adequate level of protection according to current seismic and geotechnical engineering
practice to provide adequate safety levels, as defined in the CBC, UBC, and the East of 101 Plan
Geotechnical Safety Element, and as subjected to structural peer review. Therefore, no substantial risk to
people or structures with respect to expansive soils would result. This impact would, therefore, be
considered less than significant, and no mitigation is required.
4.5-22
Genentech Corporate Facilities Master EIR
4.5 Geology and Soils
Threshold
Have soils incapable of adequately supporting the use of septic tanks or alternative
wastewater disposal systems where sewers are not available for the disposal of
wastewater
Impact 4.5-5
The project would not have soils incapable of adequately supporting the
use of septic tanks or alternative wastewater disposal systems. There would
be no impact associated with this effect.
Sewage and wastewater generated within the City is collected through the City's sewer system and is
disposed of and treated at the South San Francisco/San Bruno Water Quality Control Plant (wQCP).
The sanitary sewer system has an interconnecting network of gravity sewers, force mains, and nine pump
stations, which function together to bring wastewater from individual homes and businesses to the
WQCP. Existing infrastructure is located throughout the Genentech Campus, and any new development
would connect to or expand the existing wastewater lines. Because no septic tanks or alternative
wastewater systems are proposed, there are no effects associated with soils incapable of adequately
supporting these systems and no additional analysis is required in this MEIR. There would be no impact
associated with this effect.
4.5.4
References
Bay Area Geotechnical Group, 2004. Geotechnical Engineering Investigation Proposed Genentech Building 33,
DNA W c!y, South San Francisco, California, January.
-Supplemental Geotechnical Engineering Investigation Proposed Area 3 Fill Facility-Building 51 Western Corner of
Katifman Court at Forbes Boulevard Genentech's Lower Campus South San Francisco, California, March.
Department of Conservation. Division of Mines and Geology. 1994. Fault Activity Map of California and
Acfjacent Areas.
I<leinfelder, 2005. Geotechnical Investigation and Seismic Response Spectra for the Proposed Central Boiler Plant
Prqject at Genentech in South San Francisco, California.
South San Francisco. City of. 1994. East ofl0l Area Plan, July. Prepared by Brady and Associates
South San Francisco. City of. 1999. City of South San Francisco General Plan, 13 October. Prepared by Dyett
and Bhatia.
URS. 2003. Final Program Environmental Impact Report-Expansion of Ferry Transit Service in the San Francisco
Bc!y Area, June.
Working Group on California Earthquake Probabilities. n.d. Earthquake Probabilities in the San Francisco Bc!y
Region: 2000 to 2030-A Summary of Findings.
Genentech Corporate Facilities Master EIR
4.5-23