preliminary geotechnical investigation interstate 5 … · 2011-02-11 · interstate 5 south...

PRELIMINARY GEOTECHNICAL INVESTIGATION

INTERSTATE 5 SOUTH CORRIDOR STUDY CHULA VISTA, CALIFORNIA

PREPARED FOR: AECOM

7807 Convoy Court, Suite 200 San Diego, California 92111

PREPARED BY: Ninyo & Moore

Geotechnical and Environmental Sciences Consultants 5710 Ruffin Road

San Diego, California 92123

March 19, 2010 Project No. 106585002

I‐5 South Multimodal Corridor Study

Appendix G Preliminary Geotechnical Investigation: I‐5 South Multimodal Corridor Study (March 19, 2010)

Interstate 5 South Corridor Study March 19, 2010 Chula Vista, California Project No. 106585002

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TABLE OF CONTENTS Page

EXECUTIVE SUMMARY .............................................................................................................1

1. INTRODUCTION ....................................................................................................................3 1.1. Purpose .........................................................................................................................3 1.2. Methodology.................................................................................................................3

2. PROJECT DESCRIPTION ......................................................................................................4 2.1. Freeway Improvements ................................................................................................4 2.2. Transit Improvements...................................................................................................5 2.3. Freight Rail Improvements ...........................................................................................5 2.4. Surface Streets ..............................................................................................................5 2.5. Non-Motorized Improvements .....................................................................................5

3. PROJECT AREA DESCRIPTION...........................................................................................6

4. GEOMORPHOLOGY AND TOPOGRAPHY ........................................................................6

5. GEOLOGY...............................................................................................................................6 5.1. Regional Geology .........................................................................................................7 5.2. Site Geology .................................................................................................................7

5.2.1. Artificial Fill .......................................................................................................8 5.2.2. Young Alluvial Flood-Plain Deposits.................................................................8 5.2.3. Old Paralic Deposits............................................................................................8

5.3. Surface Waters..............................................................................................................9 5.4. Groundwater .................................................................................................................9 5.5. Faulting and Seismicity ..............................................................................................10

5.5.1. Strong Ground Motion ......................................................................................10 5.5.2. Ground Surface Rupture ...................................................................................11 5.5.3. Liquefaction ......................................................................................................11 5.5.4. Seismically Induced Settlement of Dry Soils....................................................12 5.5.5. Lateral Spreading ..............................................................................................12

5.6. Tsunamis.....................................................................................................................12 5.7. Landsliding .................................................................................................................13 5.8. Flood Hazards.............................................................................................................13 5.9. Scour ...........................................................................................................................13 5.10. Expansive Soils...........................................................................................................14 5.11. Corrosive Soils............................................................................................................14 5.12. Agricultural Soils........................................................................................................14

6. CONCLUSIONS ....................................................................................................................15

7. LIMITATIONS.......................................................................................................................16

8. REFERENCES .......................................................................................................................18


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Tables Table 1 – Principal Active Faults ...................................................................................................11 Table 2 – Soil Series Characteristics..............................................................................................15

Figures Figure 1 – Project Area Location Map Figure 2A – Project Area and Potential Improvements - Northern Portion Figure 2B – Project Area and Potential Improvements - Southern Portion Figure 3 – Geologic Map Figure 4 – Fault Location Map Figure 5 – Caltrans Peak Ground Acceleration Map Figure 6 – Tsunami Inundation Map


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EXECUTIVE SUMMARY

This report presents the results of a Preliminary Geotechnical Investigation (hereafter geotechni-cal evaluation) conducted for AECOM on behalf of San Diego Association of Governments (SANDAG) for properties associated with the Interstate 5 (I-5) South Corridor project in the City of Chula Vista in the County of San Diego, California. The goal of the I-5 South Corridor project is to evaluate existing freeway and rail facilities along a segment of the I-5 corridor and develop multi-modal conceptual alternatives. The alternatives will address future regional and local travel demands for the freeway corridor, planned development of public transit facilities (bus and light rail transit) and freight rail, and provisions for pedestrians and bicyclists. The purpose of this geotechnical evaluation was to document areas of potential geotechnical concern, which may repre-sent a constraint to the project through the need for further investigation, and/or which may impact the project cost, scope and schedule.

The areas surrounding the proposed improvements are mostly developed for residential, recrea-tional, and commercial purposes. The Chula Vista Salts flats exist near the southwestern portion of the study area. The undeveloped Sweetwater Marsh National Wildlife Refuge exists near the northwestern portion of the study area. On-site elevations range from approximately sea level (along the western border where the rivers outlet to the bay) to approximately 50 feet above mean sea level (MSL) along the marine terraces in the southern-central portion of the project area, near Palomar and Anita Streets.

Based on the research conducted for this evaluation potential geotechnical constraints are present in the project area that may impact the project cost, scope, and schedule. These potential geo-logic and geotechnical constraints include:

• Per the most recent published geologic mapping by the State of California, surface and near-surface soils at the project include artificial fills, young alluvial flood-plain deposits, and old paralic deposits. Previously these soils were mapped as Quaternary slopewash, alluvium, unnamed marine sandstone, and units of the Bay Point Formation. Although not mapped, fill materials associated with the construction of the existing paved roadways and other devel-opment are also anticipated at the project. Documentation regarding placement of fill materials may not be available depending on the location at the site. Potential geotechnical constraints related to soils at the project are:

Soft Ground – Alluvial areas and areas with undocumented fills may contain soft ground or loose soils.

Expansive Soils – Expansive soils may be present in the project site.

Corrosive Soils – Corrosive soils may be present in the project site.

• The closest known active faults are southerly extensions of the Rose Canyon Fault Zone. These extensions are present in San Diego Bay less than 1 mile west of the project area. Po-tential geotechnical constraints related to soils and seismicity at the project are:


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Ground Shaking – The project has a moderate to high potential for strong ground mo-tions due to a seismic event on a nearby fault.

Liquefaction – Loose fill and alluvial soils below the groundwater table may be subject to liquefaction during a seismic event on a nearby fault. Furthermore, those portions of the project area within the City of San Diego have been designated by the City as being sus-ceptible to liquefaction

Dynamic Settlement – Loose fill and alluvial soils above the groundwater table may be subject to dynamic settlement during a seismic event on a nearby fault.

Lateral Spread – Embankments adjacent to channels, streams, and valleys may be sub-ject to lateral spreading during a seismic event on a nearby fault.

Tsunamis – Based on tsunami inundation maps prepared by the California Geological Survey (2009) northerly portions of the project area have the potential to be inundated by tsunamis.

• Shallow groundwater may be expected to occur throughout the project area. This is particu-larly the case beneath those portions of the project which are in or adjacent to alluvial valleys and marshlands. These include areas near the Sweetwater River, Telegraph Canyon, Otay River, and San Diego Bay.

• Based on the landslide hazards map (Tan, 1995), the project is in areas with the designations 1 and 2, which are classified as being least susceptible to marginally susceptible to landsliding.

• Due to the elevation of the project and its proximity to Telegraph Canyon, and the Sweet-water and Otay Rivers significant flooding of portions of the project may occur.

• Scour of channels during storm events may be expected to occur in the lowland areas of the project. These include areas near the Sweetwater River, Telegraph Canyon, Otay River, and San Diego Bay.


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1. INTRODUCTION

This geotechnical evaluation for the Interstate 5 (I-5) South Corridor project was conducted by

Ninyo & Moore for AECOM on behalf of the San Diego Association of Governments

(SANDAG), in accordance with Task Order No. 29 06-03. The goal of the I-5 South Corridor

project is to evaluate existing freeway and rail facilities along a segment of the I-5 corridor and

develop multi-modal conceptual alternatives. The alternatives will address future regional and

local travel demands for the freeway corridor, planned development of public transit facilities

(bus and light rail transit) and freight rail, and provisions for pedestrians and bicyclists. The I-5

corridor segment generally includes properties bounded by the old freight line to the west of

the I-5 (generally paralleling Bay Boulevard) to the trolley rail line on the east side of I-5, from

the State Route 54 (SR-54)/I-5 interchange in its northern portion to the Main Street/I-5 inter-

change in its southern portion (Figure 1). Although the potential improvements would be

limited to the City of Chula Vista the project study area lies within the cities of Chula Vista,

National City, and San Diego, in the County of San Diego, California. The geotechnical

evaluation involved an analysis of geologic and geotechnical conditions lying within the con-

ceptual alternatives (herein referred to as “the project area”).

1.1. Purpose

The purpose of this evaluation was to document areas of potential geologic or geotechnical

concern, which may represent a constraint to the project through the need for further investi-

gation, and/or which may impact the project cost, scope and schedule. Subsurface exploration

and laboratory testing were not included in the scope of this reconnaissance-level evaluation.

1.2. Methodology

Our evaluation is based on geologic reconnaissance, review of published geologic maps and

data reports, aerial photographs, in-house data, and the assessment of the potential geologic

hazards in the project area. Documents pertaining to our evaluation are listed in the Refer-

ences section of this report. Per the Task Order our scope of work specifically consisted of

the tasks listed below.


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• Review of pertinent, available geologic and geotechnical literature including:

Topographic maps Fault hazard maps Geologic maps and publications Aerial photographs Groundwater maps and data reports. Geotechnical data reports

• Drive-by field reconnaissance to document conditions of potential geologic and geo-technical concern within the project area.

• Compilation and analysis of the data obtained from our background reviews and site reconnaissance.

• Preparation of this report documenting the findings of our evaluation and providing opinions and recommendations regarding possible geologic and soil impacts at the site.

2. PROJECT DESCRIPTION

Three alternatives (described below), as well as a No Build Alternative, are being considered for

the study.

The proposed project is intended to evaluate a series of possible transportation improvements

along the I-5 corridor through the City of Chula Vista. The overall goal is to identify specific im-

provements to be included in the 2050 Regional Transportation Plan (RTP), being prepared by

the San Diego Association of Area Governments (SANDAG). The primary focus of the project is

on improvements related to the existing freeway and transit systems. Improvements to the exist-

ing rail system are also considered as a way to promote freight rail operations. Additionally,

improvements to specific surface streets within the I-5 corridor are considered including street

widening, sidewalks and bike lanes. A general description of each of the major transportation

improvements being considered is provided below and illustrated in Figures 2A and 2B.

2.1. Freeway Improvements

Freeway improvements being considered include adding two high occupancy vehicle (HOV)

lanes, interchange improvements (e.g., additional turn lanes, auxiliary lanes and modified


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ramp metering) and a “braided” ramp system, which would interconnect interchanges to

minimize the impact on cars getting on and off at the existing closely space interchanges. The

possibility of moving the centerline of the freeway to the west to reduce encroachment from

freeway and rail improvements into the existing development to east is also considered.

2.2. Transit Improvements

Transit improvements being considered include enhancements to existing bus and trolley ser-

vice. The addition of two new forms of transit (Bus Rapid Transit (BRT) or Arterial Rapid

Transit (ART) is also considered. Location of BRT transit stations within the freeway median

are also being considered in conjunction with BRT service. Improvements to trolley service

include adding an express trolley during the morning and afternoon peak commute hours, de-

creased headway intervals, and additional parking at trolley stations. Grade separation is also

being considered at major intersections to reduce trolley conflicts with surface street traffic.

2.3. Freight Rail Improvements

Improvements being considered for rail operations would be focused on constructing a third

track along the entire length or portions of the study area to allow freight operations to occur

independent of trolley operations. This third track would also be used by the express trolley

being considered as part of the transit improvements. In addition, several at-grade bypass

tracks for freight trains are being considered.

2.4. Surface Streets

Improvements are being considered for H Street between I-5 and Broadway, including wid-

ening the street from four to six lanes along with a raised median, a Class I bike path, and a

16-foot parkway. Additional lanes would also be considered at the I-5 interchange.

2.5. Non-Motorized Improvements

Non-motorized improvements include additional and/or enhanced sidewalks, as well as im-

proved bike lanes/paths.


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3. PROJECT AREA DESCRIPTION

The project study area is located in the western parts of National City and Chula Vista and the

southern part of San Diego, California, along the I-5 corridor from SR-54 to Main Street including

existing rail corridors east and west of I-5 (Figure 1). The site is bounded to the north by the

Sweetwater River and to the south by the Otay River. Drainage is generally westward toward the

San Diego Bay through the above-referenced rivers. The project area is currently utilized as the I-5

highway and railroad corridor supporting freight trains, light rail transit, and the San Diego Trolley,

(Figure 2). The proposed improvements generally will occur along the already existing freeway

and rail corridor. In latitude and longitude the northern extent of the site is at approximately

32.6508 and -117.1042, respectively, and the southern extent of the site is at approximately

32.5923 and -117.0883, respectively.

4. GEOMORPHOLOGY AND TOPOGRAPHY

The project area encompasses marine terraces and river valleys bordering the southeastern por-

tion of the San Diego Bay. Project elevations range from up to approximately 50 feet MSL on the

highest marine terrace to sea level along the western border of the site. The highest elevations

occur within the southern-central portion of the site on the oldest marine terrace near Palomar

and Anita Streets. This terrace has a few minor drainage channels cutting down to the west. Ele-

vations in the northern-center portion of the site range from approximately 10 to 30 feet above

MSL. The northern, center, and southernmost portions of the site lie in the Sweetwater River,

Telegraph Canyon, and Otay River drainage channels and marshlands, respectively with the low-

est elevations of approximately 10 feet MSL or below.

5. GEOLOGY

The following sections present our findings relative to regional and site geology, geologic haz-

ards (e.g., landslides or expansive soils), groundwater, faulting and seismicity.


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5.1. Regional Geology

The project study area is situated in the western (coastal) portion of the Peninsular Ranges

geomorphic province of southern California. The Peninsular Ranges province is one of

11 geomorphic provinces recognized in California. Each province displays unique, defining

features based on geology, faults, topographic relief and climate (California Geological Sur-

vey, 2002). The Peninsular Ranges encompass an area that roughly extends from the

Transverse Ranges and the Los Angeles Basin, south to the Mexican border, and beyond an-

other approximately 800 miles to the tip of Baja California (Norris and Webb, 1990; Harden,

1998). The geomorphic province varies in width from approximately 30 to 100 miles, most of

which is characterized by northwest trending mountain ranges separated by subparallel fault

zones. In general, the Peninsular Ranges are underlain by Jurassic-age metavolcanic and meta-

sedimentary rocks and by Cretaceous-age igneous rocks of the southern California batholith.

Geologic cover over the basement rocks in the westernmost portion of the province in San

Diego County generally consists of Upper Cretaceous-, Tertiary-, and Quaternary-age sedi-

mentary rocks. Structurally, the Peninsular Ranges are traversed by several major active faults.

The Peninsular Ranges Province is traversed by a group of sub-parallel faults and fault

zones trending roughly northwest. Several of these faults are considered active. The Elsi-

nore, San Jacinto, and San Andreas faults are active fault systems located northeast of the

project area and the Rose Canyon, Coronado Bank, San Diego Trough, and San Clemente

faults are active faults located west of the project area. Major tectonic activity associated

with these and other faults within this regional tectonic framework is generally right-lateral

strike-slip movement. These faults, as well as other faults in the region, have the potential

for generating strong ground motions in the project area. Further discussion of faulting rela-

tive to the site is provided in the Faulting and Seismicity section of this report.

5.2. Site Geology

Per the most recent published geologic mapping by the State of California (Kennedy and Tan,

2008) and our geologic reconnaissance, surface and near-surface soils at the project include ar-

tificial fills, young alluvial flood-plain deposits, and old paralic deposits. Previously these soils


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were mapped as Quaternary slopewash, alluvium, unnamed marine sandstone, and units of the

Bay Point Formation (Kennedy and Tan, 1977). Although not mapped, fill materials associated

with the construction of the existing paved roadways and other development are also antici-

pated at the project. Documentation regarding placement of fill materials may not be available

depending on the location at the site. Figure 3 is a geologic map of the area. The following

unit descriptions are based on our field observations and literature review.

5.2.1. Artificial Fill

Artificial fill soils are mapped as underlying the project site along the northwestern and

southwestern edges and make up the majority of the platform west of the railroad tracks

between G and J Streets. Other areas of man-made fill are present in the study area as-

sociated with past construction activities (e.g., grading, development).

5.2.2. Young Alluvial Flood-Plain Deposits

Holocene- and late-Pleistocene-age alluvial flood-plain deposits are mapped as underly-

ing the river valleys that cross the project site and outlet to the San Diego Bay. These

deposits are described as permeable flood-plain deposits of sandy, silty, or clay-bearing

alluvium. Marine terraces were cut by the Sweetwater River, Telegraph Canyon, and

Otay River to create alluvial valleys at the northern, center, and southern portions of the

project site, respectively, composed mostly of sediments derived from old paralic depos-

its (described below).

5.2.3. Old Paralic Deposits

Pleistocene-age old paralic deposits (Qop and Qop6) are mapped underlying the areas

of higher elevations in the project site, separating the three above-mentioned river val-

leys. These deposits are described as reddish-brown, interfingered strandline, beach,

estuarine, and colluvial deposits composed of moderately permeable siltstone, sand-

stone, and conglomerate. They occur as marine terrace deposits that were laid down

by shore and nearshore processes during the Pleistocene epoch at sea levels that were

higher than today.


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5.3. Surface Waters

Review of the National City and Imperial Beach USGS topographic maps indicates that

three major drainages, namely the Sweetwater River, Telegraph Canyon, and Otay River, are

located in the northern, center, and southernmost portions of the project area, respectively.

The drainages originate from areas east of the project area, and run east-west through the

project area. At least one other unnamed, intermittent stream also runs east-west through the

northern portion of the project area (USGS, 1996).

5.4. Groundwater

Sources provided by the California Department of Water Resources (DWR) and the Califor-

nia State Water Resources Control Board (SWRCB) were reviewed for information pertaining

to groundwater quality and occurrence in the vicinity of the project. According to the SWRCB

Water Quality Control Plan for the San Diego Basin, the northern portion of the project lo-

cated north of Telegraph Canyon, near L Street, is located within the Lower Sweetwater

Hydrologic Area within the Sweetwater Hydrologic Unit. A portion of this hydrologic area, the

area closest to Telegraph Canyon approximately bounded by H and L Streets, is located the

Telegraph Hydrologic Subarea of the Lower Sweetwater Hydrologic Area within the Sweet-

water Hydrologic Unit. The southern portion of the project, south of Telegraph Canyon is

located within the Otay Valley Hydrologic Area in the Otay Hydrologic Unit.

Two DWR wells are located in the project area near the southernmost boundary reporting

groundwater levels less than 10 feet below ground surface (bgs), (DWR, 2009). Information

on the SWRCB GeoTracker website reported for properties with wells located at the east

side of the project area near F and H Streets report depths to groundwater between 10 and

30 feet bgs, (SWRCB, 2009). Based on the topography of the site and proximity to Tele-

graph Canyon, and the Sweetwater and Otay Rivers, groundwater beneath the project is

presumed to flow generally in a westerly direction (groundwater flow typically follows sur-

face topography). Depths to groundwater in the Otay Hydrologic Unit are generally 25 feet

or less (DWR, 1967). Depth to groundwater may be shallower at the western portions of the

project in the river valleys and marshland.


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5.5. Faulting and Seismicity

As shown on Figure 4, there are several active faults in the region of the project and there-

fore, the project area is considered to be seismically active. As shown on Figure 3, no known

faults cross the project area. The closest known active faults are southerly extensions of the

Rose Canyon Fault Zone (RCFZ) in San Diego Bay that are less than 1 mile west of the pro-

ject area. The RCFZ is capable of generating an earthquake magnitude of 7.0 (Caltrans,

2007) to 7.2 (California Geological Survey [CGS], 2003).

In general, hazards associated with seismic activity include strong ground motion, ground

surface rupture, liquefaction, dynamic settlement, lateral spread, and tsunamis. These haz-

ards are discussed in the following sections.

5.5.1. Strong Ground Motion

Per the California Seismic Hazard Map (Caltrans, 2007), which is based on Maximum

Credible Earthquakes, the project site is in a zone that has the potential for a peak

ground acceleration of up to 0.5g (50 percent of gravity).

The 2007 CBC recommends that the design of structures be based on the peak horizon-

tal ground acceleration (PGA) having a 2 percent probability of exceedance in 50 years

which is defined as the Maximum Considered Earthquake (MCE). Based on a Probabil-

istic Earthquake Hazard Analysis computer program by Blake (Blake, 2001), the

calculated peak ground acceleration for the Maximum Considered Earthquake

(PGAMCE) at the site, defined as having a 2 percent probability of exceedance in

50 years, with a statistical return period of approximately 2,475 years, is 0.52g. The cal-

culated peak ground acceleration for the Design Earthquake (PGADE), defined as two-

thirds of PGAMCE is 0.34g. The requirements of the governing jurisdictions and applica-

ble building codes should be considered in the design of structures.

Table 1 below lists principal known active faults that may affect the subject site, the

maximum moment magnitude (Mmax) and the fault types as published for the CGS by


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Cao et al. (2003). The approximate fault to site distance was calculated by the computer

program FRISKSP (Blake, 2001), except for the RCFZ.

Table 1 – Principal Active Faults

Fault Approximate

Distance miles (km)1

Maximum Moment Magnitude

(Mmax)1

Fault Type2

Rose Canyon <1 (1.6) 7.2 B Coronado Bank 14 (23) 7.6 B Newport-Inglewood (Offshore) 40 (64) 7.3 B Elsinore (Julian Segment) 43 (69) 7.1 A Earthquake Valley 47 (76) 6.5 B Elsinore (Coyote Mountain Segment) 48 (77) 6.8 A Elsinore (Temecula Segment) 50 (80) 6.8 A Notes: 1 Cao, et al., 2003. 2 CBC, 2001; Cao, et al., 2003.

5.5.2. Ground Surface Rupture

Ground surface rupture due to active faulting is not considered likely in the project area

due to the absence of any known active faults underlying the site. However, lurching or

cracking of the ground surface as a result of nearby seismic events is possible.

5.5.3. Liquefaction

Liquefaction of cohesionless soils can be caused by strong vibratory motion due to

earthquakes. Research and historical data indicate that loose granular soils and non-

plastic silts that are saturated by a relatively shallow groundwater table are susceptible

to liquefaction. Based on the potentially loose nature of the materials underlying parts

of the transportation corridor and the shallow groundwater table, the potential for lique-

faction should be considered high. As a result of liquefaction, proposed structures may

be subject to liquefaction-induced settlement. The amount of soil settlement during a

strong seismic event depends on the thickness of the liquefiable layers and the density

and/or consistency of the soils.


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5.5.4. Seismically Induced Settlement of Dry Soils

Relatively dry soils (e.g., soils above the groundwater table) with low density or softer

consistency tend to undergo a degree of compaction during a seismic event. Earthquake

shaking often induces significant cyclic shear strain in a soil mass, which responds to

the vibration by undergoing volumetric changes. Volumetric changes in dry soils take

place primarily through changes in the void ratio (usually contraction in loose or nor-

mally consolidated soft soils, and dilation in dense or overconsolidated stiff soils) and

secondarily through particle reorientation. Such volumetric changes are generally non-

recoverable. Based on the nature of the on-site soils, the potential for seismically in-

duced settlement of dry soils is generally considered high.

5.5.5. Lateral Spreading

Lateral spreading of the ground surface during an earthquake usually takes place along

weak shear zones that have formed within a liquefiable soil layer. Lateral spreading has

generally been observed to take place in the direction of a free-face (i.e., retaining wall,

slope, channel, etc.) but has also been observed to a lesser extent on ground surfaces

with gentle slopes. An empirical model developed by Bartlett and Youd (1995, re-

vised 1999) is typically used to predict the amount of horizontal ground displacement

within a site. For sites located in proximity to a free-face, the amount of lateral ground

displacement is strongly correlated with the distance of the site from the free-face.

Other factors such as earthquake magnitude, distance from the earthquake epicenter,

thickness of the liquefiable layers, and the fines content and particle sizes of the liquefi-

able layers will also affect the amount of settlement or lateral ground displacement.

Based on the anticipated thickness of potentially liquefiable soil layers underlying the pro-

ject, the potential for seismically induced lateral spreading is generally considered high.

5.6. Tsunamis

Tsunamis are long seismic sea waves (long compared to ocean depth) generated by sudden

movements of the sea floor caused by submarine earthquakes, landslides, or volcanic activity.


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Based on tsunami inundation maps prepared by the California Geological Survey (2009) north-

erly portions of the project area have the potential to be inundated due tsunamis (Figure 6).

5.7. Landsliding

Based on our review of published geologic literature, aerial photographs, site reconnais-

sance, and our subsurface evaluations, no landslides or related features underlie or are

adjacent the project and the potential for landslides is considered low.

According to the Landslide Hazards Map (Tan, 1995) the project site is in areas with the

designations 1 and 2. Areas with the designation 1 are classified as being least susceptible to

landsliding. Areas with the designation 2 are classified as being marginally susceptible to

landsliding. The majority of the project is in areas with the designation 2. The portions of the

project at the westernmost boundary fall within areas with the designation 1.

5.8. Flood Hazards

Based on review of Federal Emergency Management Agency (FEMA) Flood Insurance Rate

Maps (FIRM), posted on the County of San Diego, San Diego Geographic Information

Source (SanGIS) website (2004), the northern and southern portions of the project near the

Sweetwater and Otay Rivers, respectively, are within a Zone A-floodway and Zone A-100

year floodplain. The central portion of the project near Telegraph Canyon is within a Zone

X-500 year floodplain. Accordingly, there is a potential flood hazard relative to the project.

5.9. Scour

We anticipate that structures such as the bridge supports will be prone to scour during storm

events where such structures are located in active channel areas. The design of foundation ele-

ments for such structures will be sensitive to the scour depth evaluated for each specific location.


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5.10. Expansive Soils

Expansive soils generally result from specific clay minerals that have the capacity to shrink or

swell in response to changes in moisture content. Shrinking or swelling of foundation soils can

lead to damage to foundations and engineered structures, including tilting and cracking. Loose or

compressible soils may be found at the project, especially in undeveloped areas with deposits

of alluvium and developed areas with undocumented and/or uncompacted fill. Compressible

soils can be susceptible to settlement when additional loads are placed on them.

5.11. Corrosive Soils

Caltrans corrosion (2003) criteria define as soils with more than 500 parts per million (ppm)

chlorides, more than 0.2 percent sulfates, or a pH less than 5.5. Based on the proximity of

the project to San Diego Bay the presence of corrosive soils should be anticipated. However,

soil corrosivity testing will need to be performed to determine if and where corrosive soils

are present in the project site.

5.12. Agricultural Soils

Based on the Soil Survey for the San Diego Area (Bowman, 1973) and the United States

Department of Agriculture (2009), 12 different soil series have been noted within the project

area. These include: Carlsbad gravelly loamy sand, Huerhuero loam, Huerhuero-Urban land

complex, Made land, Olivenhain cobbly loam, Riverwash, Salinas clay loam, Tidal flats, Tu-

junga sand, and Visalia gravelly sandy loam. The soil types and their characteristics are

summarized in Table 2. Soils designated as the Huerhuero loam (map symbol HrC) and the

Huerhuero-Urban land complex (HuC) are dominant in the study area. The HrC and HuC

develop on calcareous alluvium derived from sedimentary rock. As noted in Table 2, some

of the agricultural soils have moderate to high potential for erosion. Also, as noted in the

Hazardous Waste Initial Site Assessment prepared for the project (Ninyo and Moore, 2010)

agricultural fields have a Medium Risk with regards to potential environmental concern.


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Table 2 – Soil Series Characteristics

Soil Series and Map Symbol Use Erosion

Potential Carlsbad gravelly loamy sand (CbB) Truck crops, citrus, flowers, range Slight

Huerhuero loam (HrC) Range, irrigated truck crops, tomatoes, flowers, housing developments Slight to moderate

Huerhuero loam (HrC2) Truck crops, tomatoes, flowers, range, housing developments Slight to moderate

Huerhuero loam (HrE2) Range Moderate to high Huerhuero-Urban land complex (HuC) Homesites -

Made land (Md) Building sites - Olivenhain cobbly loam (OhE)

Range, watershed, small housing developments, cit-rus Moderate to high

Riverwash (Rm) Source of sand and gravel - Salinas clay loam (SbA) Citrus, truck crops, tomatoes, flowers, small pasture lots Slight Tidal flats Wildlife habitat - Tujunga sand (TuB) Range, golf courses, avocados, flowers, truck crops Slight Visalia gravelly sandy loam (VbB)

Avocados, citrus, tomatoes, truck crops, flowers, walnuts, range Slight

6. CONCLUSIONS

Based on the research conducted for this evaluation potential geotechnical constraints are present

in the project area that may impact the project cost, scope, and schedule. These potential geo-

logic and geotechnical constraints include:

• Per the most recent published geologic mapping by the State of California, surface and near-surface soils at the project include artificial fills, young alluvial flood-plain deposits, and old paralic deposits. Previously these soils were mapped as Quaternary slopewash, alluvium, unnamed marine sandstone, and units of the Bay Point Formation. Although not mapped, fill materials associated with the construction of the existing paved roadways and other devel-opment are also anticipated at the project. Documentation regarding placement of fill materials may not be available depending on the location at the site. Potential geotechnical constraints related to soils at the project are:

Soft Ground – Alluvial areas and areas with undocumented fills may contain soft ground or loose soils.

Expansive Soils – Expansive soils may be present in the project site.

Corrosive Soils – Corrosive soils may be present in the project site.


106585002 R.doc 16

• The closest known active faults are southerly extensions of the Rose Canyon Fault Zone. These extensions are present in San Diego Bay less than 1 mile west of the project area. Po-tential geotechnical constraints related to soils and seismicity at the project are:

Ground Shaking – The project has a moderate to high potential for strong ground mo-tions due to a seismic event on a nearby fault.

Liquefaction – Loose fill and alluvial soils below the groundwater table may be subject to liquefaction during a seismic event on a nearby fault. Furthermore, those portions of the project area within the City of San Diego have been designated by the City as being sus-ceptible to liquefaction

Dynamic Settlement – Loose fill and alluvial soils above the groundwater table may be subject to dynamic settlement during a seismic event on a nearby fault.

Lateral Spread – Embankments adjacent to channels, streams, and valleys may be sub-ject to lateral spreading during a seismic event on a nearby fault.

Tsunamis – Based on tsunami inundation maps prepared by the California Geological Survey (2009) northerly portions of the project area have the potential to be inundated by tsunamis.

• Shallow groundwater may be expected to occur throughout the project area. This is particu-larly the case beneath those portions of the project which are in or adjacent to alluvial valleys and marshlands. These include areas near the Sweetwater River, Telegraph Canyon, Otay River, and San Diego Bay.

• Based on the landslide hazards map (Tan, 1995), the project is in areas with the designations 1 and 2, which are classified as being least susceptible to marginally susceptible to landsliding.

• Due to the elevation of the project and its proximity to Telegraph Canyon, and the Sweet-water and Otay Rivers significant flooding of portions of the project may occur.

• Scour of channels during storm events may be expected to occur in the lowland areas of the project. These include areas near the Sweetwater River, Telegraph Canyon, Otay River, and San Diego Bay.

7. LIMITATIONS

The field evaluation and geotechnical analyses presented in this report have been conducted in

accordance with current engineering practice and the standard of care exercised by reputable

geotechnical consultants performing similar tasks in this area. No warranty, implied or ex-


106585002 R.doc 17

pressed, is made regarding the conclusions, recommendations, and professional opinions ex-

pressed in this report. Variations may exist and conditions not observed or described in this

report may be encountered. Our preliminary conclusions and recommendations area based on an

analysis of the observed conditions and the referenced background information.

The purpose of this study was to evaluate geologic and geotechnical conditions within the project

site and to provide a geotechnical reconnaissance report to assist in the preparation of environ-

mental impact documents for the project. A comprehensive geotechnical evaluation, including

subsurface exploration and laboratory testing, should be performed prior to design and construc-

tion of structural improvements.


106585002 R.doc 18

8. REFERENCES

AECOM, 2009, Draft Issue Statement, I-5 South Multimodal Corridor Study, Chula Vista, Califor-nia: dated April.

Bartlett, S. F. and Youd, T. L., 1995, Revised 1999, Empirical Prediction of Liquefaction-Induced Lat-eral Spread, J. of Geotechnical Engineering, ASCE, Vol. 121, No. 4: dated April, 316-329.

Blake, T.F., 2001, FRISKSP (Version 4.00) A Computer Program for the Probabilistic Estimation of Peak Acceleration and Uniform Hazard Spectra Using 3-D Faults as Earthquake Sources.

Boore, D.M., Joyner, W.B., and Fumal, T.E., 1997, Equations for Estimating Horizontal Re-sponse Spectra and Peak Acceleration from Western North American Earthquakes: A Summary of Recent Work, Seismological Research Letters, Vol. 68, No. 1, pp. 128-153.

Bowman, R.H. 1973. Soil Survey of San Diego Area, California. United States Department of Agriculture. Soil Conservation Service, Washington, DC.

California Building Standards Commission, 2001, California Building Code, Title 24, Part 2, Volumes 1 and 2.

California Department of Transportation (Caltrans), 2003, Corrosion Guidelines (Version 1.0), Divi-sion of Engineering and Testing Services, Corrosion Technology Branch: dated September.

California Department of Transportation (Caltrans), 2007, California Seismic Hazard Map (Revised).

California Department of Water Resources, 1967, Groundwater Occurrence and Quality: San Diego Region, California, Bulletin 106-2.

California Department of Water Resources, 2009, Water Data Library Website: TUwdl.water.ca.gov/gw/map/index.cfmUT: accessed in October.

California Division of Mines and Geology, 1963, Mines and Mineral Resources of San Diego County, California, County Report 3.

California Environmental Quality Act (CEQA), 2009, Title 14. California Code of Regulations http://ceres.ca.gov/topic/env_law/ceqa/guidelines/.

California Geological Survey, 1963, Geology and Mineral Resources of San Diego County, California.

California Geological Survey, 1996, Open File Report 96-04, Update of Mineral Land Classification: Aggregate Materials in the Western San Diego County Production - Consumption Region.

California Geological Survey, 1998, Maps of Known Active Fault Near-Source Zones in Califor-nia and Adjacent Portions of Nevada: dated February.

California Geological Survey, 2002, California Geomorphic Provinces, Note 36.

California Geological Survey, 2009, Tsunamis Inundation Map.


106585002 R.doc 19

Cao, T., Bryant, W.A., Rowshandel, B., Branum, D., and Willis, C.J., 2003, The Revised 2002 California Probabilistic Seismic Hazards Maps: California Geological Survey: dated June.

County of San Diego, 2004, San Diego Geographic Information Source (SanGIS) website: http://www.sangis.org/SangisInteractive/viewer/viewer.asp.

County of San Diego, 1958, Topographic Survey, Sheet 154-1743, Scale 1”=200’.

County of San Diego, 1972, Orthotopographic Survey, Sheet 154-1743, Scale 1’=200’.

County of San Diego, 1973, Orthotopographic Survey, Sheet 154-1737, Scale 1”=200’.

County of San Diego, 1973, Orthotopographic Survey, Sheet 154-1743, Scale 1”=200’.

County of San Diego, 1976, Orthotopographic Survey, Sheet, 166-1737, Scale 1”=200’.

County of San Diego, 1976, Orthotopographic Survey, Sheet 170-1737, Scale 1”=200”.

County of San Diego, 1976, Orthotopographic Survey, Sheet 174-1737, Scale 1”-200’.

County of San Diego, 1979, Orthotopographic Survey, Sheet 154-1737, Scale 1”=200”.

Harden, D.R., 1998, California Geology: Prentice Hall, Inc.

Jennings, C.W., 1994, Fault Activity Map of California and Adjacent Areas: California Geologi-cal Survey, California Geologic Data Map Series, Map No. 6, Scale 1:750,000.

Kennedy, M.P. and Tan, S.S., 1977, Geology of National City, Imperial Beach, and Otay Mesa Quadrangles, Southern San Diego Metropolitan Area, California: California Department of Conservation, Division of Mines and Geology, Map Sheet 29, Scale 1:24,000.

Kennedy, M.P. and Tan S.S., 2008, Geologic Map of the San Diego 30' X 60' Quadrangle, California: California Geological Survey, Scale 1:100,000.

Microsoft Bing Maps, 2009, http://www.bing.com/maps/.

Ninyo & Moore, In-house proprietary information.

Ninyo & Moore, 2005, Draft Hazardous Materials Technical Study, Chula Vista Bayfront Master Plan, Chula Vista, California: dated April 29.

Ninyo & Moore, 2010, Hazardous Waste Initial Site Assessment Interstate 5 South Corridor Study, Chula Vista, California: dated March 19.

Norris, R. M. and Webb, R. W., 1990, Geology of California, Second Edition: John Wiley & Sons, Inc.

Regional Water Quality Control Board, 1994, Water Quality Control Plan for the San Diego Basin: dated September 8, amended through February 8, 2006.

State Water Resources Control Board (SWRCB), 2009, GeoTracker online database, TUwww.geotracker.swrcb.ca.gov UT: accessed in September.


106585002 R.doc 20

Tan, S.S., 1995, Landslide Hazards in the Southern Part of the San Diego Metropolitan Area, San Diego County, California.

United States Department of Agriculture, 2009, Web Soil Survey, http://websoilsurvey.nrcs.usda.gov/app/websoilsurvey.aspx.

United States Federal Emergency Management Agency (FEMA), 1997, Flood Insurance Rate Map (FIRM), Map Number 06073C1945 F: effective date June 19.




United States Geological Survey, 1967, National City Quadrangle, California, San Diego County, 7.5-Minute Series (Topographic): Scale 1:24,000.

United States Geological Survey, 1996, Imperial Beach Quadrangle, California, San Diego County, 7.5-Minute Series (Topographic): Scale 1:24,000.

AERIAL PHOTOGRAPHS Source Date Flight Numbers Scale USDA 3-31-53 AXN-3M 42 and 90 1:20,000 USDA 5-2-53 AXN-14M 108, 109, and 110 1:20,000

Pacific Ocean

San DiegoBay

NOTE: ALL DIRECTIONS, DIMENSIONS AND LOCATIONS ARE APPROXIMATE

0 0.75 1.5 MILES

APPROXIMATE SCALE

LEGEND

I-5 PROJECT AREA

INTERSTATE-5 SOUTH CORRIDOR STUDYCHULA VISTA, CALIFORNIA

PROJECT AREA LOCATION MAP FIGURE

1PROJECT NO. DATE

106585002 3/10

SOURCE: BASE - USGS, FAO, NPS, EPA, ESRI, DeLorme, TANA, other suppliers

Wed

nesd

ay, J

anua

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MATCH LINE TO FIGURE 2B

H ST

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AY

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03RD AV

NATIONAL CITY BL

N 04TH AV

J ST

04TH AV

C ST

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N 02ND AV



PROJECT AREA AND POTENTIAL IMPROVEMENTS FIGURE

2APROJECT NO. DATE

106585002 3/10

SOURCE: IMPROVEMENTS - HELIX ENVIRONMENTAL, 2010; AERIAL IMAGERY - MICROSOFT BING MAPS, 2010

Wed

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LEGEND

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I-5 CENTERLINE SHIFT

NEW LIGHT RIAL LINE EAST OF I-5

NEW FREIGHT RAIL LINE

WIDENING/RESTRIPING

INCREASED BUS SERVICE

BRAIDED RAMP

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ACCESS IMPROVEMENT

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PROJECT AREA AND POTENTIAL IMPROVEMENTS FIGURE

2BPROJECT NO. DATE

106585002 3/10

SOURCE: IMPROVEMENTS - HELIX ENVIRONMENTAL, 2010; AERIAL IMAGERY - MICROSOFT BING MAPS, 2010

Wed

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NEW FREIGHT RAIL LINE

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NOTE: ALL DIRECTIONS, DIMENSIONS AND LOCATIONS ARE APPROXIMATE 0 3,500 7,000 FEET

APPROXIMATE SCALE


GEOLOGIC MAP FIGURE

3PROJECT NO. DATE

106585002 3/10

SOURCE: KENNEDY, M.P., AND TAN, S.S., 2008, GEOLOGIC MAP OF THE SAN DIEGO 30’ X 60’ QUADRANGLE, CALIFORNIA.

I-5 PROJECT AREA

YOUNG ALLUVIAL FLOOD-PLAIN DEPOSITS (HOLOCENE AND LATE PLEISTOCENE)OLD ALLUVIAL FLOOD-PLAIN DEPOSITS, UNDIVIDED (LATE TO MIDDLE PLEISTOCENE)

MARINE BEACH DEPOSITS (LATE HOLOCENE)

UNDIVIDED MARINE DEPOSITS IN OFFSHORE REGION (LATE HOLOCENE)

ARTIFICIAL FILL (LATE HOLOCENE)

SAN DIEGO FORMATION (EARLY PLEISTOCENE AND LATE PLIOCENE) - MARINE SANDSTONE

OLD PARALIC DEPOSITS, (LATE TO MIDDLE PLEISTOCENE) - UNIT 6VERY OLD PARALIC DEPOSITS, UNDIVIDED (MIDDLE TO EARLY PLEISTOCENE)

OLD PARALIC DEPOSITS, UNDIVIDED (LATE TO MIDDLE PLEISTOCENE)

OFFSHORE MAP SYMBOLS

af

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STRIKE AND DIP OF BEDS

INCLINED4

FAULT - SOLID WHERE ACCURATELY LOCATED; DASHED WHERE APPROXIMATELY LOCATED; DOTTED WHERE CONCEALED

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SAN JOSECUCAMONGA

MALIBU COASTSANTA MONICA

SANCAYETANO

SANTASUSANASIMI-

SANTAROSA

NORTHRIDGE

CHARNOCK

SAWPITCANYON

SUPERSTITION HILLS

NEVADA

CALIFORNIA

RO

SE

CA

NY

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San Bernardino County

Kern County

Riverside CountySan Diego County Imperial County

Los Angeles County

Ventura County

Orange County

Riverside County

San

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Los Angeles C

ounty

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Pomona

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Long Beach

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Los Angeles

Victorville

SanClemente

PalmSprings

Big Bear CityThousandOaks San

Bernardino

LakeArrowhead

Twentynine Palms

Baker

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S a l t o n S e a

NOTES: ALL DIRECTIONS, DIMENSIONS AND LOCATIONS ARE APPROXIMATE

LEGEND

HOLOCENE ACTIVE

CALIFORNIA FAULT ACTIVITY

HISTORICALLY ACTIVE

LATE QUATERNARY (POTENTIALLY ACTIVE)


FAULT LOCATION MAP FIGURE

4PROJECT NO. DATE

106585002 3/10

SOURCE: FAULTS - CA DEPT OF CONSERVATION, 2000; BASE - ESRI, 2008

Wed

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QUATERNARY (POTENTIALLY ACTIVE)

CALIFORNIA

0 30 60 MILES

APPROXIMATE SCALE

SITE