Coast Corridor

Draft Program EIS/EIR 3.11 Geology, Soils, and Minerals

3.11-1

3.11 GEOLOGY, SOILS, AND MINERALS

This section describes the existing geologic setting and soil conditions in the study 

area as well as any potential impacts that would occur with either the No Build or 

Build Alternative. The section evaluates existing fault lines, seismic hazards, 

landslide susceptibility, and liquefaction susceptibility. The analysis also discloses 

locations of oil and gas fields, mineral resource sites, and bedrock conditions that 

are relevant for any potential excavation activities.

3.11.1 REGULATORY REQUIREMENTS

There are no federal statutes or regulatory provisions related to geology and soils 

considerations on non-federal lands. However, a number of state and local 

regulations apply to geologic hazards and engineering best practices. 

State

Alquist-Priolo Earthquake Zoning Act (Public Resources Code § 

2621 et seq.): 

The Alquist-Priolo Earthquake Zoning Act regulates development and construction 

in designated corridors along active faults (earthquake fault zones) where there is 

elevated risk of surface fault rupture. Earthquake fault zone maps are prepared by 

the State Geologist to indicate areas with potential surface fault rupture hazards. 

Before a project can be permitted or developed, cities and counties must conduct a 

site-specific geologic investigation to determine if the project would cross an active 

fault. The Alquist-Priolo Act prohibits the location of most types of structures for 

human occupancy across the active traces of faults in earthquake fault zones. 

Seismic Hazards Mapping Act (Public Resources Code § 2690-

2699.6): 

The Seismic Hazard Mapping Act was adopted in 1990 following the Loma Prieta 

earthquake to reduce threats to public health and safety and to minimize property 

damage caused by earthquakes. The act directed the California Department of 

Conservation to identify and map areas prone to the earthquake hazards of 

liquefaction, earthquake-induced landslides, and amplified ground shaking. The act 

further required most new development projects for human occupancy with 

designated zones to undergo site-specific geotechnical investigations to identify 

potential seismic hazards and formulate/implement mitigation measures. 
Coast Corridor

3.11 Geology, Soils, and Minerals Draft Program EIS/EIR

3.11-2

Surface Mining and Reclamation Act (Public Resources Code § 2710 

et seq.)

The Surface Mining and Reclamation Act established a program to regulate surface 

mining activities to assure that adverse environmental impacts are minimized and 

mined lands are reclaimed to a usable condition. The law sets uniform 

requirements for areas that are known to contain mineral deposits important to 

meet the future needs of the area. 

Local

Monterey County General Plan

The Monterey County General Plan Safety Element contains policies for seismic and 

geologic hazards. The overall goal of these policies is to minimize the potential for 

loss of life and property resulting from geologic and seismic hazards. The policies 

include enforcement of state policies, site-specific geologic studies as it relates to 

new development, land use designations, and required involvement of a California 

licensed civil engineer or landscape architect when necessary.

San Luis Obispo County General Plan

The San Luis Obispo County General Plan Safety Element contains policies for 

seismic and geologic hazards. The overall goal of these policies is to minimize the 

potential for loss of life and property resulting from geologic and seismic hazards. 

The General Plan includes policies, standards, and a corresponding implementation 

program that relates to fault rupture hazards, groundshaking, liquefaction and 

seismic settlement, slope instability and landslides, and coastal bluff erosion.

3.11.2 METHODS OF EVALUATION

To assess potential impacts related to geology, soils, and minerals, aerial mapping 

was used to obtain information for the existing Coast Corridor rail alignment and the 

proposed physical improvement areas. Proposed physical improvements were 

mostly evaluated as having high, medium, or low potential geologic impacts based 

on the number of geologic constraints identified. 

Active faults, ground shaking, liquefaction, slope stability, and soil type are 

evaluated in the analysis. The data used for the aerial mapping incorporated the 

permanent and temporary footprints for each proposed physical improvement and 

the existing alignment to determine the findings. Table 3.11-1 summarizes 
Coast Corridor

Draft Program EIS/EIR 3.11 Geology, Soils, and Minerals

3.11-3

potential geological and soils-related effects. Table 3.11-2 summarizes specific 

geologic and soils related issues for each of the proposed physical improvements. 

The permanent and temporary footprint areas are defined as follows:

 Impact Type Definitions: 

 Permanent: Areas where affected resources will not be restored back to their 

original conditions (i.e. new track locations). 

 Temporary: Areas that will be disturbed during construction and then 

returned to their original conditions post construction (i.e. staging areas, 

ingress/egress).

 Track/Signal Upgrades:

 Existing railroad right of way (upgrades will be constructed via existing tracks 

– No Impacts are assumed) 

 Sidings: 

 Permanent = Existing railroad right of way 

 Temporary = 50 feet on either side of existing right of way

 Curve Realignments: 

 Permanent =100 foot wide corridor

 Temporary = 200 feet on either side of 100 foot corridor for a total width of 

500ft

 Second Mainline: 

 Permanent = Existing railroad right of way

 Temporary = 100ft on either side of existing railroad right of way

 Stations

 Soledad Station: 1.9 Acres – permanent impact area is based on conceptual 

station plans from the Soledad Downtown Specific Plan (2012).

 King City Station: 3.4 Acres – permanent impact area is based on conceptual 

station plans from the King City First Street Corridor Master Plan (2013).

Faults

The permanent and temporary impact footprints were measured to identify any 

Alquist-Priolo and Quaternary faults that cross the existing alignment as well as the 

areas with proposed physical improvements. The data was measured in the amount 

of feet of the proposed improvements that are within a fault zone; the results are 

expressed as a percentage within Table 3.11-2. 
Coast Corridor

3.11 Geology, Soils, and Minerals Draft Program EIS/EIR

3.11-4

Ground Shaking

The permanent and temporary impact footprints were measured to show the level 

of ground motion that may affect the areas with proposed physical improvements. 

The data was categorized has low, medium, and high horizontal ground 

accelerations using California potential shaking ranges. Low is classified as 0.0 –

0.83g, medium is 0.83 – 1.66g, and high is 1.66 – 2.50g. 

Liquefaction

The permanent and temporary footprints of proposed physical improvements were 

measured to show the relative susceptibility for liquefaction (accounting for the age 

and type of soil/sediment, relative density of the mater, and the depth of the water 

table). The data was ranked to show whether the area was very low, low, 

moderate, high, and very high susceptibility to liquefaction. 

Slope Stability

The permanent and temporary footprints of proposed physical improvements were 

measured to show areas that may be susceptible to landsliding. The data was 

ranked to show whether the area was very low, low, moderate, high, and very high 

susceptibility to liquefaction.

Shrink-Swell Potential

The permanent and temporary footprints of proposed physical improvements were 

measured to show areas of soils that would be considered expansive by the Uniform 

Building Code (1994). The data was ranked as low, moderate, or high susceptibility 

to shrink-swell.

Corrosive Soils

The permanent and temporary footprints of proposed physical improvements were 

measured to show areas of soils that are considered corrosive to uncoated steel and 

concrete. The data was ranked as low, moderate, or high susceptibility to corrosion.

Soil Erosion

The permanent and temporary footprints of the proposed physical improvements 

were reviewed in light of existing slope and vegetation coverage to determine 

whether construction activities would have high, medium, or little/low potential to 

result in soil erosion. 
Coast Corridor

Draft Program EIS/EIR 3.11 Geology, Soils, and Minerals

3.11-5

Mineral Resources

The presence of important mineral resources, such as oil/gas fields and geothermal 

wells are evaluated in the analysis. The aerial mapping data incorporated the 

permanent and temporary footprints for each proposed physical improvement and 

the existing alignment relative to known oil and gas fields. The number of such 

fields crossed by the proposed improvements is noted. 

3.11.3 AFFECTED ENVIRONMENT

Geologic Setting

California’s central coast has a dynamic and varied landscape made up of coastal 

mountain ranges, gently sloping hills, and valley flats. Overtime, tectonic plate 

activity and instances of high-pressure and heat (metamorphism) changed the 

composition and structure of underlying materials. As a result, Monterey and San 

Luis Obispo Counties are geologically complex and seismically active. 

The Coast Corridor is situated in the Coastal Ranges Geomorphic Province with the 

Pacific Ocean to the west and the Great Valley Geomorphic Province to the east, 

with the distant Sierra Nevada Mountain Range Geomorphic Province further east.

1

 

The California coastal mountain ranges were formed by vertical uplift as the Pacific 

tectonic plate and the North American tectonic plate converged and compressed. 

Over tens of millions of years, these mountain ranges eroded and deposited 

nutrient-rich soil on the California central valley flats. The earth’s climate changed

over time, shifting between glacial maximums and interglacial periods, and resulted

in sea level fluctuations. When the seas advanced, marine layers were deposited

and formed the rich soils found in the Salinas Valley, which continue today to lend 

themselves to intensive agricultural uses. 

In the northern portion of the study area within Monterey County, most of the 

underlying geologic units are quaternary alluvium and marine deposits from the 

Pliocene to Holocene epoch, between the present time and 1.6 million years ago 

(mya). The quaternary alluvium deposits are generally young and made up of 

unconsolidated sand, silt, and clay-bearing material. 2

 

1

California Geological Survey, 2006

2

County of Monterey, 2006, pp. 4.4-1-2, 25
Coast Corridor

3.11 Geology, Soils, and Minerals Draft Program EIS/EIR

3.11-6

San Luis Obispo County is primarily underlain with quaternary alluvium and marine 

deposits and Franciscan Complex. The underlying Franciscan Complex formed when 

subsurface soils underwent high-pressure and heat as the Pacific and North 

American plates interacted. These geological deposits are much older than 

quaternary alluvium; they were formed between the Jurassic to Cretaceous epochs 

(between 65 and 200 mya).

Seismic Hazards

Faults

Tectonic plate activity in Central California has resulted in a variety of active fault 

zones. A fault is a fracture on the earth’s surface where two blocks of the earth’s 

crust slide past each other. In most of California, large faults form in response to 

stress caused by relative displacement between the North American and Pacific 

tectonic plates. Over time, the displacement stresses build up enough strain that 

the two blocks slip past each other to alleviate the tension, causing an earthquake. 

Surface rupture occurs when the ground surface is broken due to fault movement 

during an earthquake. 

Several faults are located within the Coast Corridor rail alignment, as shown in 

Figure 3.11-1 and Figure 3.11-2. 

3

The California Geological Survey and the United States Geological Survey (USGS) 

classify active faults if they have ruptured in the last 11,000 years (or within the 

Holocene epoch). All other faults are considered inactive.

4

The Rinconada quaternary fault is the most prevalent active fault within the Coast 

Corridor alignment. The Rinconada fault zone is a strike-slip fault that is part of the 

San Andreas Fault system and extends west of King City southeast for approximately 

74 miles to Santa Margarita.5 The Rinconada fault is parallel to the Coast Corridor 

throughout most of Monterey County. Near Paso Robles, the existing rail alignment 

travels turns towards the southwest direction and traverses the fault line through 

Templeton, Atascadero, and Santa Margarita. According to the Monterey County 

General Plan EIR, the Rinconada fault has a low-rated slip potential and is not 

expected to produce large earthquakes. No major earthquake has occurred along 

this fault within the past 100 years. 

 

3

This graphic depicts only terrestrial portions of the illustrated fault lines within Monterey County.

4

County of Monterey, 2006, p. 4.4-. 

5

Rosenberg and Bryant, 2003
Coast Corridor

Draft Program EIS/EIR 3.11 Geology, Soils, and Minerals

3.11-7

Small portions of the Cambria and Oceanic faults traverse the existing rail alignment 

near the City of San Luis Obispo. The Cambria fault trends northwest and is 

approximately 39 miles long. The Oceanic Fault Zone trends north-northwest for 62 

miles.6 

Ground Shaking

Ground or seismic shaking is the motion of the earth’s surface resulting from an 

earthquake generated by a sudden slip at a fault line. An earthquake with moderate 

to high magnitude can generate considerable ground shaking. The degree of 

shaking is dependent on the magnitude of the earthquake, distance to the 

epicenter, duration of strong ground motion, and local geological conditions (soil 

type, topography, etc). The most common damage from ground shaking is 

structural damage to buildings. 

Both Monterey County and San Luis Obispo Counties are located in a seismically 

active region subject to earthquakes and potentially strong ground shaking from 

nearby faults and generally unconsolidated alluvial areas. The most recent large 

earthquake in the region was the 2003 San Simeon earthquake, which registered a 

magnitude of 6.5. This event resulted in two fatalities from a building collapse in 

downtown Paso Robles. The 1989 Loma Prieta earthquake resulted in moderate to 

light ground shaking in the northern Salinas Valley. Although most of Monterey and 

San Luis Obispo Counties are subject to strong ground shaking, the vast majority of 

the existing Coast Corridor alignment and proposed improvements have a low 

potential for ground shaking, as further discussed below. One portion of Section #1 

of the existing alignment within Monterey County, south of Salinas, has moderate 

ground shaking potential. 

Liquefaction 

Liquefaction is the process in which water-saturated sediment temporarily loses 

strength and acts as a fluid. During liquefaction, the soil undergoes temporary loss 

of strength causing the soil to behave as a fluid for short periods of time. To be 

susceptible to liquefaction, a soil is typically cohesionless, with a grain size 

distribution of a specified range (generally sand and silt), loose to medium dense, 

below the groundwater table, and subjected to a sufficient magnitude and duration 

of ground shaking. Liquefaction-related damage could include loss of support 

beneath foundations and other rail improvements. Figure 3.11-3 and Figure 3.11-4

summarizes liquefaction potential of the Coast Corridor. 

 

6

County of San Luis Obispo, 1999,pp. 57-60
Coast Corridor

3.11 Geology, Soils, and Minerals Draft Program EIS/EIR

3.11-8

According to the Monterey County General Plan EIR, ground shaking that causes 

liquefaction is most prevalent in alluvial basins in Monterey County. The portions of 

Coast Corridor within Monterey County are most subject to liquefaction near the 

Salinas River and floodplain. 

In San Luis Obispo County, areas that are underlain by young, poorly consolidated, 

saturated granular alluvial sediments are most susceptible to liquefaction. Areas 

adjacent to rivers and creeks are also considered vulnerable. Liquefaction potential 

along the Coast Corridor ranges from very low to very high, but most of the existing 

alignment and proposed improvements have moderate potential. 

Slope Stability

Slope failure can occur as either rapid movement of large masses of soil (landslide) 

or slow, continuous (creep). The primary factors influencing the stability of a slope 

are the nature of the underlying soil or bedrock, the geometry of the slope (height 

and steepness), rainfall, and the presence of previous landslide deposits. Landslides 

typically occur in areas of steep slopes where underlying earth materials are 

relatively weak and particularly where high rainfall occurs and/or high groundwater 

levels are present. Water can act as a lubricant to decrease resisting forces. Ground 

shaking due to earthquakes can also cause landslides. The Coast Corridor alignment 

is located along largely flat areas where landslide hazard risk is generally low, with 

the exception of several high-risk area as discussed below. 

Soils

Shrink-Swell Potential

Expansive soils can undergo significant volume change (shrink or swell) due to 

variations in moisture content. Earth materials susceptible to these volumetric 

changes include soils and rock formations containing clays. Changes in soil moisture 

content can result for rainfall, irrigation, utility leakage, surface drainage, perched 

groundwater, drought, or other factors. 

During shrink-swell cycles, the volume of the soil changes and can cause damage to 

infrastructure. Expansive soils vary in severity along the existing Coast Corridor 

alignment and where there are proposed physical improvements. In Monterey 

County, expansive soils are most severe in the northern portions of the existing 

alignment. Most of the proposed physical improvements have low or moderate 

amounts of expansive soil. 
Coast Corridor

Draft Program EIS/EIR 3.11 Geology, Soils, and Minerals

3.11-9

In San Luis Obispo County, the shrink-swell potential for soils is much lower than in 

Monterey County. Along the existing Coast Corridor alignment, the presence of 

expansive soils is mostly moderate to low. 

Corrosive Soils

A corrosive substance is one that will destroy or irreversibly damage another surface 

or substance with which it comes into contact. Corrosive soils are a potential hazard 

to concrete and metal foundations, utilities, and other buried or ground-level

improvements. 

Soil Erosion

Soil erosion is a natural process that can be caused by wind, water, waves, or 

corrosion. Erosion can lead to soil loss, degraded water quality, and other effects. 

In agricultural areas of the Salinas Valley, erosion is common when flooding is 

prevalent. As a result, sediment is picked up and deposited in another location. 

Wind is another common source of erosion in the Salinas Valley, especially in areas 

with sandy deposits.7 Most of the existing Coast Corridor alignment has soil prone 

to moderate erosion. 

Mineral Resources

Geological resources in California include oil and gas fields, geothermal fields, and a 

wide range of mineral resources. Given the value of these resources, CEQA requires 

consideration of whether a project would eliminate or otherwise reduce access to 

such resources. According to the Monterey County General Plan EIR, there are oil 

wells scattered throughout Monterey County, but the vast majority are clustered in 

the San Ardo oil and gas field, the sixth largest oil field in the state of California. The 

existing Coast Corridor rail alignment passes through a portion of the San Ardo field. 

3.11.4 ENVIRONMENTAL CONSEQUENCES

No Build Alternative

The No Build Alternative represents the continuation of existing operations and 

physical components, and assumes the perpetuation of existing freight and 

passenger service. The only proposed physical improvement would be the 

implementation of PTC along the corridor, including modification to signaling and 

 

7

County of Monterey, 2006,pp. 4.4-21-23
Coast Corridor

3.11 Geology, Soils, and Minerals Draft Program EIS/EIR

3.11-10

communications equipment. These PTC related changes are not expected to incur 

heightened risk associated with geology or soils-related effects. As such, existing

passenger and freight operations (along with potential additional freight operations)

would continue to be susceptible to the geologic hazards present within the study 

area. 

Build Alternative

The Build Alternative would construct physical improvements in areas with high 

geological impact potential. Table 3.11-1 summarizes potential geological and soilsrelated effects. Table 3.11-2 summarizes specific geologic and soils related issues 

for each of the proposed physical improvements.

Table 3.11-1 Types of Potential Impacts from Geologic and Soil Conditions

Geologic Condition Potential Impact

Ground Shaking/Liquefaction Ground shaking and liquefaction effects from an earthquake could pose safety 

hazards to workers and public from possible derailment, collapse of 

infrastructure, or damage to facilities. 

Active Fault Crossing Active fault crossings could pose potential risk to workers and public due to 

interruption of service or derailment due to surface rupture along faults. 

Slope Stability Landslide potential could pose potential risk to workers and public due to failure 

of natural and/or construction cut slopes or retention structures.

Soil Conditions Expansive soil, corrosive soil, and soil erosion could damage infrastructure and

cause premature deterioration of underground structures.

Oil & Gas Fields Potential migration of oil & gas fields could release toxic gases into subsurface 

materials. 

Mineral Resources Potential project costs and delays due to potential impacts on existing mineral 

resource areas and facilities, including remediation. 

Source: Circlepoint, 2014.
Coast Corridor

Draft Program EIS/EIR 3.11 Geology, Soils, and Minerals

3.11-11

Table 3.11-2 Summary of Potential Geologic and Soil Impacts

Build 

Alternative 

Components

Active 

Fault 

Crossing 

(% of 

length)

Ground 

Shaking 

Potential 

(H/M/L)

Liquefaction 

Potential 

(H/M/L)

Landslide 

Potential/ 

Slope 

Stability

(H/M/L)

Soil ShrinkSwell 

Potential 

(H/M/L)

Soil Corrosivity 

Potential

(H/M/L)

Soil 

Erosion 

Hazard 

Potential

(H/M/L)

Oil & Gas 

Fields

(# 

crossed)

Steel Concrete

Salinas 

Powered 

Switch

0% Low High Low Moderate High Low Low 0

Upgrades to 

Existing 

Alignment 

Section #1 

0% Low/

Moderate

High Low High (56%)

Moderate 

(12%)

Low (32%)

High Low Very Low 0

Spence Siding 

Extension

0% Low Moderate Low Moderate/ 

High

High Low Low 0

Upgrades to 

Existing 

Alignment 

Section #2 

0% Low Moderate Moderate High (28%)

Moderate 

(28%)

Low (37%)

N/A (5%) 

High Low/ 

Moderate

High (8%)

Moderate 

(2%)

Low (90%)

0

Gonzales 

Powered 

Switch

0% Low Moderate Moderate Moderate High Low Low 0
Coast Corridor

3.11 Geology, Soils, and Minerals Draft Program EIS/EIR

3.11-12

Build 

Alternative 

Components

Active 

Fault 

Crossing 

(% of 

length)

Ground 

Shaking 

Potential 

(H/M/L)

Liquefaction 

Potential 

(H/M/L)

Landslide 

Potential/ 

Slope 

Stability

(H/M/L)

Soil ShrinkSwell 

Potential 

(H/M/L)

Soil Corrosivity 

Potential

(H/M/L)

Soil 

Erosion 

Hazard 

Potential

(H/M/L)

Oil & Gas 

Fields

(# 

crossed)

Steel Concrete

Soledad 

Powered 

Switch

0% Low Moderate Low High High Low Low 0

Soledad New 

Passenger 

Station

0% Low Moderate Low High High Low Low 0

Harlem/Metz 

Curve 

Realignments

0% Low High Moderate Low High Low Low/ 

Moderate

0

Chalone Creek 

New Siding 

0% Low High Moderate Low/ 

Moderate

High Low Low 0

Upgrades to 

Existing 

Alignment 

Section #3

0% Low High Moderate High (36%)

Moderate 

(22%)

Low (32%)

N/A (11%)

High Low High (11%)

Moderate 

(23%)

Low (66%)

0

Coburn Curve 

Realignments

0% Low High Moderate Moderate/ 

High

High Low Low 0

King City Siding 

Extension

0% Low Moderate Low Moderate High Low Low 0
Coast Corridor

Draft Program EIS/EIR 3.11 Geology, Soils, and Minerals

3.11-13

Build 

Alternative 

Components

Active 

Fault 

Crossing 

(% of 

length)

Ground 

Shaking 

Potential 

(H/M/L)

Liquefaction 

Potential 

(H/M/L)

Landslide 

Potential/ 

Slope 

Stability

(H/M/L)

Soil ShrinkSwell 

Potential 

(H/M/L)

Soil Corrosivity 

Potential

(H/M/L)

Soil 

Erosion 

Hazard 

Potential

(H/M/L)

Oil & Gas 

Fields

(# 

crossed)

Steel Concrete

King City New 

Passenger 

Station

0% Low Moderate Low Moderate High Low Low

King City 

Powered 

Switch

0% Low Moderate Low Moderate High Low Low

Upgrades to 

Existing 

Alignment 

Section #4

0% Low Moderate Low Moderate 

(44%)

Low (31%)

N/A (26%)

High Low High (26%)

Moderate 

(4%)

Low (71%)

0

MP 165 Curve 

Realignment

0% Low Moderate Low High High Low/ 

Moderate

Low/ 

Moderate

0

San Lucas New 

Siding 

0% Low Moderate Low Low/High High Moderate Low/ 

Moderate

0
Coast Corridor

3.11 Geology, Soils, and Minerals Draft Program EIS/EIR

3.11-14

Build 

Alternative 

Components

Active 

Fault 

Crossing 

(% of 

length)

Ground 

Shaking 

Potential 

(H/M/L)

Liquefaction 

Potential 

(H/M/L)

Landslide 

Potential/ 

Slope 

Stability

(H/M/L)

Soil ShrinkSwell 

Potential 

(H/M/L)

Soil Corrosivity 

Potential

(H/M/L)

Soil 

Erosion 

Hazard 

Potential

(H/M/L)

Oil & Gas 

Fields

(# 

crossed)

Steel Concrete

Upgrades to 

Existing 

Alignment 

Section #5

0% Low High High High (13%)

Moderate 

(51%)

Low (32%)

N/A (4%)

High Low Very High 

(6%)

High (11%)

Moderate 

(5%)

Low (78%)

2

MP 172 Track 

Realignment

0% Low Moderate Low Moderate High Low/ 

Moderate

Low/ 

Moderate

0

San Ardo

Powered 

Switch

0% Low Moderate Low Moderate High Low Low 0

Getty/Bradley 

Curve 

Realignments

0% Low Moderate High Low/ 

Moderate

High Low Low/ 

Moderate

0

Bradley Siding 

Extension

0% Low High Moderate High High Low/ 

Moderate

Low 0

Bradley 

Powered 

Switch

0% Low High Moderate High High Low/ 

Moderate

Low 0
Coast Corridor

Draft Program EIS/EIR 3.11 Geology, Soils, and Minerals

3.11-15

Build 

Alternative 

Components

Active 

Fault 

Crossing 

(% of 

length)

Ground 

Shaking 

Potential 

(H/M/L)

Liquefaction 

Potential 

(H/M/L)

Landslide 

Potential/ 

Slope 

Stability

(H/M/L)

Soil ShrinkSwell 

Potential 

(H/M/L)

Soil Corrosivity 

Potential

(H/M/L)

Soil 

Erosion 

Hazard 

Potential

(H/M/L)

Oil & Gas 

Fields

(# 

crossed)

Steel Concrete

Upgrades to 

Existing 

Alignment 

Section #6

0% Low High Low High (14%)

Low (96%)

High Low Low 0

Upgrades to 

Existing 

Alignment 

Section #7

0% Low Moderate 

(95%)

Very High (5%)

Low Low Moderate Low Low 0

McKay/ 

Wellsona 

Curve 

Realignments

0% Low Moderate/Very 

High

Low Low Moderate Low/ 

Moderate

Low/ 

Moderate

0

McKay East 

Powered 

Switches

0% Low Moderate Low Low Moderate Low Low 0

Wellsona New 

Siding

0% Low Moderate/ 

Very High

Low Low Moderate Low Low/ 

Moderate

0

Upgrades to 

Existing 

Alignment 

Section #8

0.21% Low Very Low (47%)

Moderate 

(23%)

Very High 

(30%)

Low Moderate 

(41%)

Low (59%)

Moderate

/High

Low/ 

Moderate

Low/ 

Moderate

0
Coast Corridor

3.11 Geology, Soils, and Minerals Draft Program EIS/EIR

3.11-16

Build 

Alternative 

Components

Active 

Fault 

Crossing 

(% of 

length)

Ground 

Shaking 

Potential 

(H/M/L)

Liquefaction 

Potential 

(H/M/L)

Landslide 

Potential/ 

Slope 

Stability

(H/M/L)

Soil ShrinkSwell 

Potential 

(H/M/L)

Soil Corrosivity 

Potential

(H/M/L)

Soil 

Erosion 

Hazard 

Potential

(H/M/L)

Oil & Gas 

Fields

(# 

crossed)

Steel Concrete

Wellsona/ 

Paso Robles 

Curve 

Realignments

0% Low Moderate Low Low Moderate

/ High

Low/ 

Moderate

Low 0

Templeton 

Siding

Extension

2.02% Low Moderate/ 

High

Low Low/ 

Moderate

Moderate

/High

Low Low 0

Templeton/ 

Henry Curve 

Realignments

0% Low Moderate Low Low Moderate Low/ 

Moderate

Moderate 1

Upgrades to 

Existing 

Alignment

Section #9

0.84% Low Very Low (27%)

Moderate 

(72%)

Very High (1%)

Low (68%)

Moderate 

(16%)

High (16%)

High (6%)

Moderate 

(38%)

Low (56%)

Moderate Low Low 0

Henry/Santa 

Margarita 

Curve 

Realignment

18.31% Low Very Low/ 

Moderate

Low Low/ 

Moderate

Moderate Low/ 

Moderate

Low 0

Santa 

Margarita

Powered 

Switch

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Coast Corridor

Draft Program EIS/EIR 3.11 Geology, Soils, and Minerals

3.11-17

Build 

Alternative 

Components

Active 

Fault 

Crossing 

(% of 

length)

Ground 

Shaking 

Potential 

(H/M/L)

Liquefaction 

Potential 

(H/M/L)

Landslide 

Potential/ 

Slope 

Stability

(H/M/L)

Soil ShrinkSwell 

Potential 

(H/M/L)

Soil Corrosivity 

Potential

(H/M/L)

Soil 

Erosion 

Hazard 

Potential

(H/M/L)

Oil & Gas 

Fields

(# 

crossed)

Steel Concrete

Cuesta Second 

Main Track

0% Low Very Low/ 

Moderate

Low/High Low/ 

Moderate

Moderate

/ High

Moderate/ 

High

Moderate/

High

0

Upgrades to 

Existing 

Alignment 

Section #10

0.58% Low Very Low (83%)

Moderate 

(17%)

Low (15%)

High (80%)

Very High 

(4%)

High (30%)

Moderate 

(62%)

Low (8%)

High Low/ 

Moderate

Low/ 

Moderate

0

Source: ICF, 2013
Coast Corridor

3.11 Geology, Soils, and Minerals Draft Program EIS/EIR

3.11-18

Seismic Hazards 

As shown in Table 3.11-2, geologic conditions in the study area generally present 

low to moderate constraints on development. Overall, the study area has a low 

potential for ground shaking as few active faults cross the existing and proposed 

alignment areas; however, about 18 percent of the proposed Henry/Santa 

Margarita curve realignment area traverses the Rinconada Fault. As a result, the 

improvement would require special designs to minimize potential damage to the 

tracks and other infrastructure as a result of potential surface fault rupture. That 

said, the Rinconada fault has a low-rated slip potential and is not expected to 

produce large earthquakes, as discussed in Subsection 3.11.3.

Liquefaction potential is generally moderate to high for most of the study area. The 

Coburn curve realignment, Harlem/Metz curve realignment, Bradley siding 

extension, and the new siding at Chalone Creek are most notable in Monterey 

County with high liquefaction potential. Similarly, the proposed McKay/Wellsona 

curve realignment, Templeton siding extension, and new siding at Wellsona are 

proposed in areas of high liquefaction potential in San Luis Obispo County. 

Portions of the existing alignment and proposed physical improvements within 

Monterey County have mostly low potential for landslides due to generally flat 

topography, as shown in Figure 3.11-5. However, several portions of the alignment 

run immediately adjacent to or near relatively steep slopes. Such areas include the 

Harlem/Metz and Coburn curve realignments, Chalone Creek new siding, and 

upgrades to existing alignment #3. These components thus have moderate 

potential for landslides. Further south, the Getty/Bradley curve realignments and

the Bradley siding extension have moderate to high potential for landslides. In San 

Luis Obispo County, the existing railroad alignment is within an area of generally low 

landslide potential.

Overall, the proposed physical improvements with the most noteworthy geologic 

risks are the Getty/Bradley curve realignments, Harlem Metz curve realignments, 

Bradley siding extension, and the new siding at Chalone Creek, which face moderate 

to high risks for both liquefaction and landslide potential. 

Soils

As shown in Table 3.11-2, soil conditions in the study area generally present

moderate constraints on development. Most of the proposed improvements within 

Monterey County have moderate to high shrink-swell potential. Particularly, the 

Spence siding extension, Coburn curve realignment, MP 165 curve realignment, 

Bradley siding, San Lucas siding, and the proposed Soledad station have several 
Coast Corridor

Draft Program EIS/EIR 3.11 Geology, Soils, and Minerals

3.11-19

acres of high potential shrink-swell soil potential. In San Luis Obispo County, shrinkswell soil potential in improvement areas and existing areas is generally low to 

moderate.

Most of the soils in areas of the proposed physical improvements in Monterey 

County are highly corrosive to steel and low to concrete with low potential for soil 

erosion. Most of the soils in San Luis Obispo County are moderately corrosive to 

steel and concrete with low to moderate soil erosion potential.

Mineral Resources

The proposed Templeton/Henry curve realignment would cross over one oil and gas 

field that is no longer in use. There are no geothermal wells within any of the 

proposed improvement areas.

3.11.5 AVOIDANCE, MINIMIZATION, AND MITIGATION 

STRATEGIES

The individual improvements comprising the Build Alternative should be designed to 

minimize impacts related to geology and soils along the Corridor. The following 

strategies have been identified at this preliminary stage to avoid, minimize, and/or 

mitigate any potentially significant impacts.

Ground Shaking

Ground shaking hazards cannot be mitigated completely and thus can be 

unpredictable. The following minimization strategies should be implemented to 

reduce potential adverse effects from ground shaking in areas where substantial risk 

is present:

MIN-GEO-1. Infrastructure can be designed to withstand strong ground motion. 

Designs typically include additional ductility in the structure. The design needed to 

reduce ground shaking would be determined upon for structures during subsequent 

stages of development, when detailed design plans are created.

MIN-GEO-2. Liquefaction potential can be reduced through site-specific methods 

such as soil densification or structural design.

Fault Crossings

MIN-GEO-3. Techniques to monitor track alignment as routine maintenance and the 

installation of ground motion warning systems could be used to reduce the effects 

of fault crossings.
Coast Corridor

3.11 Geology, Soils, and Minerals Draft Program EIS/EIR

3.11-20

Slope Stability/Landslides

A-GEO-4. Geotechnical studies during subsequent site-specific evaluation would 

assist in determining the potential for failure of natural and constructed slopes and 

identifying temporary and permanent slope reinforcement and protection measures 

where appropriate.

Soil Hazards 

A-GEO-5. As one or more components of the Build Alternative are selected for 

further design, a site-specific subsurface evaluation shall be performed by a 

qualified geologist to evaluate the extent of soils susceptible to shrink-swell present 

along the alignment. Where expansive soil conditions are found and would be 

detrimental to proposed improvements, measures recommended by the geologist 

would be implemented in project design. 

MIN-GEO-6. A subsurface evaluation would be performed prior to design and 

construction to evaluate the potential for corrosive soil and identify 

recommendations to minimize or avoid any potential effects related to the presence 

of such soils (including but not limited to corrosion of rails or ties).

Hazards Related to Oil and Gas Fields

Hazards related to potential migration of hazardous gases due to the presence of oil 

fields, gas fields, or other subsurface sources can be mitigated by following strict 

federal and state Occupational Safety & Health Administration (OSHA/CalOSHA) 

regulatory requirements for excavations, and consultation with the California 

Department of Conservation (Division of Oil and Gas) and the California Department 

of Toxic and Substances Control regarding known areas of concern. Mitigation

strategies would include 

A-GEO-7. Use safe and explosion-proof equipment during construction and testing 

for gases regularly. 

A-GEO-8. Active monitoring systems and alarms would be required in underground 

construction areas and facilities where subsurface gases are present. 

Mineral Resources

A-GEO-9. Important mineral sites will be identified as early as possible during

detailed project-level reviews and avoided where possible.
Coast Corridor

Draft Program EIS/EIR 3.11 Geology, Soils, and Minerals

3.11-21

3.11.6 SUBSEQUENT ANALYSIS

Prior to implementing specific elements of the Build Alternative, component-specific 

geology, soils and minerals evaluations should be conducted. These evaluations 

would be used to determine if additional mitigations strategies from those 

discussed above in Subsection 3.11.5 would be applicable. 
Coast Corridor Improvements EIR/EIS

3.11-1

Figure Active Fault Zones in Monterey County

Source: Monterey County, 2004

Exhibit 4.4.1

Regional Faults

00982.07 (06-08)

Proposed Rail Alignment Existing Rail Alignment
Coast Corridor Improvements EIR/EIS

3.11-2

Figure Active Fault Zones in San Luis Obispo County

Source: USGS, 2013

Existing Rail Alignment
Coast Corridor Improvements EIR/EIS

3.11-3

Figure Monterey County Liquefaction Potential

Source: Monterey County, 2004

Existing Rail Alignment

Legend
Wellsona/Paso Robles

McKay/Wellsona

McKay/Wellsona

McKay/Wellsona

Wellsona Siding

H

EA-8

H

H

EA-7

EA-6 H

EA-7

San

Luis

Obispo County

Monterey County

El Paso de

Robles (Paso

Robles)

San

Miguel

£¤101

£¤101

Coast Corridor Improvements EIR/EIS

c

a

b

San Luis Obispo Liquefaction Potential Figure 3.11-4a

Legend

Project Components

Existing Alignment

Sidings

Realignments

Liquefaction Potential

Unknown

Very Low

Low

Moderate

Very High

Source: ICF International, 2013

±

±

0 1 2

Miles

1:75,000

Page 4a
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Henry/Santa Margarita Templeton/Henry

Henry/Santa Margarita

Henry/Santa Margarita

Henry/Santa Margarita

Templeton Siding

Second Main Line

H

EA-10

EA-9 H

H

EA-9

EA-8 H

Atascadero

El Paso de

Robles (Paso

Robles)

Templeton

UV46

£¤101

£¤101

Coast Corridor Improvements EIR/EIS

c

a

b

San Luis Obispo Liquefaction Potential Figure 3.11-4b

Legend

Project Components

Existing Alignment

Sidings

Realignments

Liquefaction Potential

Unknown

Very Low

Low

Moderate

Very High

Source: ICF International, 2013

±

±

0 1 2

Miles

1:75,000

Page 4b
This page intentionally left blank.
Henry/Santa Margarita

Second Main Line

EA-10 H

H

EA-10

EA-9 H

Arroyo

Grande

San Luis

Obispo

UV1

UV227

£¤101

£¤101

Coast Corridor Improvements EIR/EIS

c

a

b

San Luis Obispo Liquefaction Potential Figure 3.11-4c

Legend

Project Components

Existing Alignment

Sidings

Realignments

Liquefaction Potential

Unknown

Very Low

Low

Moderate

Very High

Source: ICF International, 2013

±

±

0 1 2

Miles

1:75,000

Page 4c
This page intentionally left blank.
3.11-5

Figure Monterey County Landslide Potential

Source: Monterey County, 2004

Coast Corridor Improvements EIR/EIS

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M o n t er ey B a y

S a n B e nit o Co un t y

S a n B e nit o Co un t y

S a n t a C ru z Cou n t y

Fr es n o Co unt y

S a n L ui s Ob i s p o C o un ty

King s Co u nt y

S a nt a C l a ra C o un t y

San C lemente

R eservoir

Bi g S u r R i ver

Los Padres

Hunter L iggett

National

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M i litary R eservation

S a n L ui s Ob i s p o C o un ty

C amp

R oberts

M i l . R es.

Carmel R i ver

Ca rmel R i ver

T horne R d

Elm Ave

C entral A ve

Jolon R d

San L uca

R

s

d

Lockw ood Jolon

Peach T ree R d

Jolon R d

Oasis R d

R d Lo ck w ood S an Lucas R d

S arge nts R d

In terl ak e R d

V ineyard C anyon R d

India n V al ley R d

C holam e R d

Slack s C anyon R d

S argents R d

Bitterw ater R d

Spreck les R d

A rroy o S e co R d

Foothill R d

R iver R d

Old Stage R d

Alisal R d

Old Stage R d

San Juan G rade R d

Espinosa R d

Blanco R d

D avis R d

N ashua R d

E lkhorn R d

D olan R d

H all Rd

San Juan R d

C armel V alley R d

C astr ovi lle B l vd

M ig uel

S a n

Canyon Rd

N S outh R d

17 M ile D r

Laurel es G rade

Corral D e T ierra R d

S an B en anc i o R d

C armel V al ley Rd

R i v e r R d

Paraiso R d

S an Juan R d

R eservation R d

Oasis R d

A r or yo Seco

A r r oy o Seco

N a c imi ento R i ver

San A ntoni o R i v er

Sa linas R i ver

Sa l inas R iver

Salinas R iver

Espinosa

Lake

Moro

Cojo

Sl ough

Elkhorn

Sl ough

Los

P adres

R eservoir

L ittl e Sur R i ver

P ancho R i co C reek

A lisal Creek

Laguna Seca

B ig Sandy Creek

San L orenzo Creek

Sa n L orenzo C reek

Johnson Creek

Lake

Antonio

San

M onterey Del MonteForest

(PebbleBeach)

Las Gaz as

Creek R eservoi r

Bradley

C h a lone C reek

Stonewa ll Creek

N acimiento

Lak e D r

S al inas

M arina

S easide

M onterey

K i ng C ity

Soledad

Pacifi c G rove

G reenfi eld

G onzal es

Del R ey Oak s Carmel-by-the-Sea

Sand

City

Pajaro

Aromas

Elkhorn

Chualar

Boronda

San Ardo

Spreckels

San Lucas

Prunedale

Las Lomas

Castroville

Moss Landing

Carmel

V alley V illage

-.

G11

-.

G19

-.

G12

-.

G15

-.

G18

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G14

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G17

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G16

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£[101

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G20

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G13

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Data Sources: County of Monterey - GIS Department, URS Corporation, US Geological Survey (USGS),

US Census Bureau, University of California Santa Barbara (UCSB), HAZUS-MH MR2, Lewis I. Rosenberg

(2001, Relative earthquake-induced landslide susceptibility of Monterey County, California. Data produced

for 21st Century General Plan Update, Monterey County, 2001)

El Estero

L ake

Del

Monte

L ake

R es er vation R d

W Bl anco R d

Forest L ak e

Pr escott A ve

Beach R d

C armel Av e

M onte Av e

For est A ve

Sunset Dr

17 M i l e D r

Lighthouse A v e

Del

H i lby A ve

Broadway A ve

Fremont B l vd

Ocean

R io R d Jun i pero A v e

Sceni c R d

Av e

M unras A ve

Pacif ic S t

Aguaj ito R d

David A ve

S k yli ne D r

Ocean V iew Bl vd

8th A ve

W Fr ank l in S t

8th S t

Imj in

2n

R d

d A ve

M a r i na

M uni ci pa l

Ai r port

C ity of S easide N ot

C onsider ed i n P l an

Del M onte

Bl vd

R eindol lar A ve

12th S t

Av e 4th

Seal R oc k Cr eek

L aguna

Del R ey

P eni nsul a

M onterey

Ai r port

C armel V alley R d

M ar V ista Pl ay

T

a

iog a

M o n t er ey B a y

S a l i n a s R iv er

M udhen L ak e

N S outh R d

C ar lt o n R ey Bl v d

C a nyo n del

-.

G17

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M etz R d

East S t

Front

Fort R omi e R d

S al ina s R iver

Arroyo S eco

C r eek Stonewal l

San V i cente R d

C am phora G lori a R

C a

d

m phora

R d

Br yant C any on R d

Nestles R d

M or isol i R d

M ission R d

W est St

Palm A ve M ai n

Arroyo S eco

R d

T err aza

G abi lan

-.

G17 ·}þ

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£[101

T horne R d

El C amino R eal

Elm A ve

C entr al A ve

M etz

W alnut Av e

Es pinosa R d

Elm A ve

2nd S t

3rd S t

C ypr ess A ve

St 14th

Pine A v e

Oak A ve

Appl e A ve 4th S t C herry A ve

12th S t

Es pinosa R d

E spinosa R d

C halone Crk

Sal i na s R iver

R d

-.

G15

-.

G16

·}þ

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3rd S t S pr eck els R d

Bitterwater R d

B roadway S t

C entr al A ve

C anal S t

Jolon R d

M etz R d

Pettitt R d

P ine Cany on R d

Lonoak R d

S an A ntoni o R d

D ivisio n

K i ng

Pearl St

1st S t

San Lorenz o Cr eek

Sal ina s R iv er

K ing C ity

Municipal

Airport

-.

G15

£[101

-.

G13

-.

G14

1 inch equals 4 miles

0 1 2 4 6 8

Miles

1 inch equals 1.5 miles

0 0.75 1.5 2.25 3

Miles

339.0

27 degree rotation for all views

S D avis R d

S M ain S t

N M ain S t

Boronda

W i l li ams R d

Al isal R d

E A l isal S t

Spr eck els B l vd

E B l anco R d

W Bl anco R d

W M ark et S t

E M ark et S t

W L aurel D r

W A l isal S t

C astrov il l e R d

E A l vin D r

E L aurel D r Constituti on B l vd

N atividad R d

Sal inas

Municipal

Airport

N D av is R d

Abbott S t

M onterey S al inas H wy

N S anborn R d

A lis al C reek

G abi lan Creek

Carr

L ake

E Boronda

R d

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R d

Nativ ida d Creek

San Juan G rade R d

R ogge R d

H ark ins R d

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£[101

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R i ver R d

Old S tage R d

5th S t

G onzal es R iv er R d

Alta S t S A lta S t

Johnson C anyon R d

G loria R d

10th S t

C enter S t

Johnson Creek

Sal ina s R iver

Shor

R

t

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Gonzales Salinas

Soledad

King City Greenfield

County Map Scale

City Inset Map Scale

T:\ M onter ey_C ounty \ R H M P\ deli v era bl es\ E 9_L andsl ide.mxd

Legend

Hydrology (Perennial and Intermittent)

River, Creek or Tributary

Lake or Pond

Artifical Path, Canal/Ditch or Connector

Basemap

Hillshades created from USGS 1" (county-wide)

and 1/3" (city insets) National Elevation Dataset.

Census Designated Place !

Jurisdictional Boundaries

City Limits, Monterey County

Military Reservation

National Forest

County Boundary

Circulation

Active Railroad (Union Pacific)

Local Roads (City Insets Only)

State Highway

US Highway

Major Roads

County Highway

Carmel-by-the-Sea

Del Rey Oaks

Marina

Monterey

Pacific Grove

Sand City

Seaside

Figure E-9. Landslide Hazard Areas

Monterey County, California

Multi-Jurisdictional Hazard Mitigation Plan

Earthquake-Induced Landslide

Susceptibility

Low

Moderate

High

Legend

Jurisdictional Boundaries

City Limits, Monterey County

Military Reservation

National Forest

County Boundary

Circulation

Active Railroad (Union Pacific)

Local Roads (City Insets Only)

State Highway

US Highway

Major Roads

County Highway

Earthquake-Induced

Landslide

Susceptibility

Low

Moderate

High

Existing Rail Alignment
Coast Corridor

3.11 Geology, Soils, and Minerals Draft Program EIS/EIR

3.11-28

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