APPENDIX F-J 

Preliminary Geotechnical Evaluation 

PRELIMINARY GEOTECHNICAL EVALUATION 

DESERTXPRESS RAIL LINE 

VICTORVILLE, CALIFORNIA 

TO LAS VEGAS, NEVADA 

PREPARED FOR: 

CIRCLEPOINT

135 Main Street, Suite 1600 

San Francisco, California 94105 

PREPARED BY: 

Ninyo & Moore 

Geotechnical and Environmental Sciences Consultants 

475 Goddard, Suite 200 

Irvine, California 92618 

May 1, 2007 

Project No. 206725001 

F-J-1
May 1, 2007 

Project No. 206725001 

Mr. Scott Steinwert 

CIRCLEPOINT

135 Main Street, Suite 1600 

San Francisco, California 94105 

Subject: Preliminary Geotechnical Evaluation 

DesertXpress Rail Line 

 Victorville, California to Las Vegas, Nevada 

Dear Mr. Steinwert: 

Transmitted herein are the results of our preliminary geotechnical evaluation for the proposed 

DesertXpress rail line from Victorville, California, to Las Vegas, Nevada. This study included 

evaluation of the geologic and geotechnical conditions along potential rail alignments within the 

project study area. We understand that the results of this study will be utilized in project planning 

and project feasibility evaluations. 

We appreciate the opportunity to be of service. 

Respectfully submitted, 

NINYO & MOORE 

Michael E. Rogers, C.E.G. 

Senior Project Geologist 

Scott M. Johnson, C.E.G. 

Principal Geologist 

Jalal Vakili, Ph.D., P.E. 

Principal Engineer 

MER/SMJ/JV/djt/sc 

Distribution: (4) Addressee 

F-J-2
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TABLE OF CONTENTS 

Page

1. INTRODUCTION ....................................................................................................................1

2. REGULATORY ENVIRONMENT AND METHODS OF EVALUATION..........................1 

2.1. Regulatory Requirements .............................................................................................1 

2.2. Methods of Evaluation of Impacts................................................................................3 

2.2.1. Study Methods ....................................................................................................3 

2.2.2. Proposed Improvement Alternatives...................................................................3 

2.2.2.1. Segment 1, Alternatives A and B: Victorville to Lenwood, California 

(Figure 2).................................................................................................4

2.2.2.2. Segment 2, Alternatives A and B: Lenwood to Yermo, California (Figure 3) .......................................................................................................5 

2.2.2.3. Segment 3, Alternatives A and B: Yermo to Mountain Pass, California 

(Figure 4).................................................................................................5 

2.2.2.4. Segment 4, Alternatives A and B: Mountain Pass to near the State Line 

(Figure 5).................................................................................................6

2.2.2.5. Segment 5, Alternatives A and B: State Line to Sloan, Nevada (Figure 

6) .............................................................................................................6 

2.2.2.6. Segment 6, Alternatives A, B, C, and D: Sloan to Las Vegas, Nevada 

(Figure 7).................................................................................................6

2.2.2.7. Segment 7, Alternatives A, B and C: Las Vegas, Nevada (Figure 7).....7 

3. AFFECTED ENVIRONMENT................................................................................................7 

3.1. Regional Environment Description ..............................................................................7 

3.2. Regional Geology .......................................................................................................10 

3.3. Resources by Segment................................................................................................11 

3.3.1. Segment 1, Alternative A (Victorville to Lenwood, California) ......................12

3.3.2. Segment 1, Alternative B (Victorville to Lenwood, California).......................13

3.3.3. Segment 2, Alternative A (Lenwood to Yermo, California).............................15 

3.3.4. Segment 2, Alternative B (Barstow to Yermo, California)...............................17 

3.3.5. Segment 3, Alternatives A and B (Yermo to Mountain Pass, California) ........19 

3.3.6. Segment 4, Alternative A (Mountain Pass to State Line) .................................24 

3.3.7. Segment 4, Alternative B (Mountain Pass to State Line) .................................25 

3.3.8. Segment 5, Alternatives A and B (State Line to Sloan, Nevada) .....................26 

3.3.9. Segment 6, Alternatives A and B (Sloan to Las Vegas, Nevada).....................29 

3.3.10. Segment 6, Alternatives C and D (Sloan to Las Vegas, Nevada).....................30 

3.3.11. Segment 7, Alternatives A and B (City of Las Vegas, Nevada).......................32

3.3.12. Segment 7, Alternative C (City of Las Vegas, Nevada) ...................................34 

3.3.13. Groundwater and Surface Water.......................................................................35 

3.4. Regional Active and Potentially Active Faults...........................................................38 

3.4.1. San Andreas Fault Zone....................................................................................41 

3.4.2. Garlock Fault.....................................................................................................41 

3.4.3. Eastern California/Mojave Shear Zone.............................................................41 

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3.5. Active and Potentially Active Faults Crossing Segments of the Alignment..............42 

3.5.1. Helendale-South Lockhart Fault (active and potentially active portions) ........45

3.5.2. Lenwood-Lockhart-Old Woman Springs Fault ................................................45 

3.5.3. Mt. General Fault ..............................................................................................45 

3.5.4. Gravel Hills-Harper Lake Fault ........................................................................45 

3.5.5. Calico-Hidalgo Fault.........................................................................................46 

3.5.6. Manix Fault .......................................................................................................46 

3.5.7. Unnamed (Cronese Valley) Fault......................................................................46 

3.5.8. Baker Fault........................................................................................................47 

3.5.9. Stateline Fault ...................................................................................................47 

3.5.10. Faults in Las Vegas Valley ...............................................................................47 

4. ENVIRONMENTAL CONSEQUENCES .............................................................................47 

4.1. Regional Effects – Operational Period .......................................................................47 

4.1.1. Surface Fault Rupture .......................................................................................48 

4.1.2. Ground Shaking ................................................................................................49 

4.1.3. Liquefaction ......................................................................................................51 

4.1.4. Dam Inundation.................................................................................................52 

4.2. Regional Effects – Construction Period .....................................................................53 

4.2.1. Settlement (Natural Soils and Undocumented Fill) ..........................................53 

4.2.2. Corrosive Soils..................................................................................................54 

4.2.3. Expansive Soils .................................................................................................54 

4.2.4. Landslides .........................................................................................................55 

4.2.5. Caliche/Hard Rock Excavation.........................................................................56 

4.2.6. Ground Fissures ................................................................................................57 

4.2.7. Shallow Groundwater .......................................................................................57 

4.3. Regional Effects by Segment......................................................................................58 

4.3.1. Segment 1 (Victorville to Lenwood, California) ..............................................58 

4.3.1.1. Operational Period Segment 1, Alternative A.......................................58 

4.3.1.2. Operational Period Segment 1, Alternative B.......................................59 

4.3.1.3. Construction Period Segment 1, Alternative A.....................................60 

4.3.1.4. Construction Period Segment 1, Alternative B.....................................63 

4.3.2. Segment 2 (Lenwood to Yermo, California).....................................................65 

4.3.2.1. Operational Period Segment 2, Alternative A.......................................65 

4.3.2.2. Operational Period Segment 2, Alternative B.......................................66 

4.3.2.3. Construction Period Segment 2, Alternative A.....................................67 

4.3.2.4. Construction Period Segment 2, Alternative B.....................................69 

4.3.3. Segment 3 (Yermo to Mountain Pass, California)............................................71 

4.3.3.1. Operational Period Segment 3, Alternatives A and B...........................71 

4.3.3.2. Construction Period Segment 3, Alternatives A and B.........................73 

4.3.4. Segment 4 (Mountain Pass to State Line).........................................................75 

4.3.4.1. Operational Period Segment 4, Alternative A.......................................75 

4.3.4.2. Operational Period Segment 4, Alternative B.......................................77 

4.3.4.3. Construction Period Segment 4, Alternative A.....................................78 

4.3.4.4. Construction Period Segment 4, Alternative B.....................................80 

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4.3.5. Segment 5 (State Line to Sloan, Nevada) .........................................................82 

4.3.5.1. Operational Period Segment 5, Alternatives A and B...........................82 

4.3.5.2. Construction Period Segment 5, Alternatives A and B.........................84 

4.3.6. Segment 6 (Sloan to Las Vegas, Nevada).........................................................86 

4.3.6.1. Operational Period Segment 6, Alternatives A and B...........................86 

4.3.6.2. Construction Period Segment 6, Alternatives A and B.........................87 

4.3.6.3. Operational Period Segment 6, Alternatives C and D...........................90 

4.3.6.4. Construction Period Segment 6, Alternatives C and D.........................91 

4.3.7. Segment 7 (City of Las Vegas, Nevada)...........................................................93 

4.3.7.1. Operational Period Segment 7, Alternatives A and B...........................93 

4.3.7.2. Construction Period Segment 7, Alternatives A and B.........................94 

4.3.7.3. Operational Period Segment 7, Alternative C.......................................97 

4.3.7.4. Construction Period Segment 7, Alternative C.....................................98 

5. RELATIVE EFFECTS OF ENVIRONMENTAL CONSEQUENCES...............................100

6. MITIGATION MEASURES................................................................................................102 

6.1. Operational Mitigation Measures .............................................................................102 

6.1.1. Surface Fault Rupture .....................................................................................102 

6.1.2. Ground Shaking ..............................................................................................104 

6.1.3. Liquefaction ....................................................................................................104 

6.1.4. Dam Inundation...............................................................................................105 

6.2. Construction Mitigation Measures ...........................................................................106 

6.2.1. Settlement (Natural Soils and Undocumented Fill) ........................................106 

6.2.2. Corrosive Soils................................................................................................106 

6.2.3. Expansive Soils ...............................................................................................107 

6.2.4. Landslides .......................................................................................................108 

6.2.5. Caliche/Hard Rock Excavations .....................................................................109 

6.2.6. Ground Fissures ..............................................................................................109 

6.2.7. Shallow Groundwater .....................................................................................110 

7. LIMITATIONS.....................................................................................................................111

8. SELECTED REFERENCES ................................................................................................112 

Tables

Table 1 – Range of Annual Rainfall Totals at Selected Alignment Locations ...................................9 

Table 2 – Geologic Units Segment 1, Alternative A........................................................................13 

Table 3 – Geologic Units Segment 1, Alternative B........................................................................14 

Table 4 – Geologic Units Segment 2, Alternative A........................................................................17 

Table 5 – Geologic Units Segment 2, Alternative B........................................................................18 

Table 6 – Geologic Units Segment 3, Alternatives A and B............................................................23 

Table 7 – Geologic Units Segment 4, Alternative A........................................................................25 

Table 8 – Geologic Units Segment 4, Alternative B .......................................................................26 

Table 9 – Geologic Units Segment 5, Alternatives A and B............................................................28 

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Table 10 – Geologic Units Segment 6, Alternatives A and B..........................................................30 

Table 11 – Geologic Units Segment 6, Alternatives C and D ........................................................31 

Table 12 – Geologic Units Segment 7, Alternatives A and B..........................................................30 

Table 13 – Geologic Units Segment 7, Alternative C......................................................................30 

Table 14 – Depth to Groundwater in Caltrans Borings for I-15 Construction.................................37 

Table 15 – Principal Regional Active and Potentially Active Faults...............................................39 

Table 16 – Active and Potentially Active Faults Crossing Segments of the Alignment ..................44 

Table 17 – Estimated Peak Horizontal Ground Accelerations Anticipated Along Segments of 

 the Alignment...............................................................................................................50

Table 18 – Relative Effects of Environmental Consequences .....................................................101 

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Figures

Figure 1 – Site Location Map 

Figure 2 – Segment 1 Vicinity Map 

Figure 3 – Segment 2 Vicinity Map 

Figure 4 – Segment 3 Vicinity Map 

Figure 5 – Segment 4 Vicinity Map 

Figure 6 – Segment 5 Vicinity Map 

Figure 7 – Segments 6 and 7 Vicinity Map 

Figure 8 – Regional Geologic Map (San Bernardino Sheet) 

Figure 9 – Regional Geologic Map (Trona Sheet) 

Figure 10 – Regional Geologic Map (Kingman Sheet) 

Figure 11 – Regional Geologic Map (Clark County) 

Figure 12 – Regional California Fault Map 

Figure 13 – Las Vegas Valley Fault and Earth Fissures Map 

Figure 14 – Estimated Peak Horizontal Ground Acceleration Map 

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1. INTRODUCTION

In accordance with your request, Ninyo & Moore has performed a preliminary geologic evaluation for the proposed DesertXpress rail line from Victorville, California, to Las Vegas, Nevada. 

The purpose of the study was to evaluate geologic and geotechnical conditions for proposed new 

rail line alignments within the project study area. The study area was limited to the vicinity of the 

planned new alignment, consisting of an approximately 200-mile-long route from a planned new 

station in Victorville, California, that generally follows the corridor of Interstate 15 (I-15) to a 

planned new station in Las Vegas, Nevada (Figure 1). The conceptual alignment consists of 

seven segments. This report presents our preliminary findings and conclusions pertaining to the 

geotechnical aspects of the proposed alignments for the DesertXpress. 

Ninyo & Moore’s scope of services has included the following items: 

x Review of pertinent, readily available geotechnical literature including geologic maps, regional fault maps, seismic data, stereoscopic aerial photographs, and geotechnical and 

geologic reports by others. Documents reviewed for our evaluation are listed in the Selected 

References. 

x Review of as-built highway plans and geotechnical support documents for the construction 

of I-15 obtained from the California Department of Transportation (CalTrans). 

x Review of preliminary conceptual alignment drawings for the proposed DesertXpress by 

Korve Engineering. 

x Compilation and analysis of the data obtained, with particular emphasis on potential geologic and geotechnical hazards, such as faulting and seismicity. 

x Preparation of this report to present our findings and conclusions, particularly regarding possible geotechnical constraints and possible mitigative measures. 

2. REGULATORY ENVIRONMENT AND METHODS OF EVALUATION 

2.1. Regulatory Requirements 

Various building codes, municipal laws and legislative regulations present guidelines for design parameters and construction activities related to geotechnical aspects of the proposed 

DesertXpress rail system. Various public agencies would have regulatory authority over both 

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construction and operational activities related to geotechnical aspects of the proposed rail 

system. During the construction period of the proposed rail system, certain agencies would 

have authority over the design review, permitting and inspection of various constructionrelated activities. Some of these agencies would have a long-term role in the regulation of 

geotechnical conditions of the rail line during the operational period. 

During the design and permitting of the proposed rail system, regulatory agencies would 

have authority to review design plans and consultant reports for conformance with geotechnical-related issues of applicable guidelines, codes and legislative acts. Some regulatory 

agencies may seek third party review of project plans/reports, and design interaction with 

these parties and the agencies may be anticipated. 

During the construction of the proposed rail system, public agencies would have authority to 

inspect various geotechnical aspects and safety aspects of the construction such as excavations for both shallow and deep foundations of the rail system and associated structures, 

excavations for areas to receive fill, tunneling excavations and subsurface drainage improvements. 

These agencies would include, but are not limited to the following: 

x Incorporated cities whose limits include the proposed rail alternatives including Victorville and Barstow, California, and Las Vegas, Nevada. 

x Counties of San Bernardino, California and Clark, Nevada. 

x The California Geological Survey (CGS). 

x Cal-OSHA.

x California Department of Transportation (CalTrans). 

x Nevada Department of Transportation (NDOT). 

x Nevada Bureau of Mines and Geology (NBMG). 

x U.S. Department of Interior, Bureau of Land Management (BLM). 

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During the operational period of the proposed rail system, some of these regulatory agencies 

may have authority over operational activities related to geotechnical issues. For example, if 

a potential geotechnical hazard affected the operation of the rail system, certain agencies 

may have authority over the inspection/testing of the system, or maintenance/repair of the 

system. 

2.2. Methods of Evaluation of Impacts 

2.2.1. Study Methods 

To evaluate potential geologic and seismic hazards considered for the proposed new rail 

alignments within the project study area, review of readily available geologic and seismic literature, maps and information, and conceptual plans of the proposed project was 

performed. The study area was limited to the vicinity of the proposed new alignment alternatives described below. Field reconnaissance, subsurface exploration, and laboratory 

testing of materials were not included in the scope of this evaluation.

Geotechnical considerations associated with potential geologic and seismic hazards 

have been evaluated from a review of available published geotechnical literature pertinent to the proposed project. These include, but are not limited to: aerial photographs; 

geologic, seismic and topographic maps, data, and other publications by the California 

Division of Mines and Geology (CDMG), CGS, United States Geological Survey 

(USGS), NBMG; the safety elements of the general plan for the County of San Bernardino; and available geotechnical reports and as-built highway plans from CalTrans 

pertinent to the project. 

2.2.2. Proposed Improvement Alternatives 

The proposed rail line improvements consist of an intra-regional rail transportation system, which will connect the populous Southern California region with tourism and 

business activities in Las Vegas. We understand that for the majority of its length, the 

rail line will be constructed at grade and that elevated structures will be needed at various roadways, drainage channels, and other crossings. A planned crossing of the Mojave 

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River west of Barstow will entail construction of a bridge. We further understand that 

some tunneling structures may be utilized in the Mountain Pass segment of the Alignment. 

The Alignment has been divided into seven segments as shown on Figure 1: Segment 1 

– Victorville to Lenwood, California; Segment 2 – Lenwood to Yermo, California; Segment 3 – Yermo to Mountain Pass, California; Segment 4 – Mountain Pass to the 

California state line; Segment 5 – the Nevada state line to Sloan, Nevada; Segment 6 – 

Sloan to Las Vegas, Nevada; and Segment 7 – City of Las Vegas. There are two alternative routes within Segments 1 through 5 of the Alignment that are being considered for 

the rail line; Segment 6 has four alternative routes; and Segment 7 has three alternative 

routes. The routes generally follow existing transportation routes, primarily highways 

and railways, with the exception of proposed alignments in the Hodge/Lenwood area 

southwest of Barstow (Segment 1, Alternative B), the proposed Mojave River crossing 

in the Lenwood/Barstow area, and the proposed Mountain Pass/Clark Range tunneling 

alignment (Segment 4, Alternative B). The alternative routes that are being considered 

are described below. 

Due to the close proximity on the median and northwest sides of I-15, respectively, Alternatives A and B of Segment 3 have been evaluated as one Alignment. Similarly, 

Alternatives A and B of Segment 5 have been evaluated as one; Alternatives A and B of 

Segment 6 have been evaluated as one; Alternatives C and D of Segment 6, which 

closely parallel each other, have been evaluated as one; and Alternatives A and B of 

Segment 7 have been evaluated as one. 

2.2.2.1. Segment 1, Alternatives A and B: Victorville to Lenwood, California 

(Figure 2) 

x Segment 1 begins in Victorville and ends in Lenwood on the west side of the 

city of Barstow. Separate alternatives A and B diverge in different directions 

from the planned Victorville station. 

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x Alternative A is currently planned along the existing Burlington Northern 

Santa Fe (BNSF) rail line that roughly follows the National Trails Highway 

(Route 66) north from Victorville. This alternative turns northeasterly at 

Helendale and ends in Lenwood on the west side of Barstow. 

x Alternative B follows the west side of I-15 northeast from the Victorville station. Near the crossing with Hodge Road, this alternative turns north across a 

sparsely developed desert area to Lenwood. 

x Alternatives A and B of Segment 1 meet at a common point in Lenwood, 

wherein Segment 2 begins. 

2.2.2.2. Segment 2, Alternatives A and B: Lenwood to Yermo, California 

(Figure 3) 

x Segment 2 begins in Lenwood and travels northeast across largely undeveloped land on the south bank of the Mojave River to a planned bridge crossing 

of the river. On the north side of the river, the Alignment turns eastward utilizing an abandoned BNSF right-of-way into the central Barstow area. East of the 

BNSF right-of-way, Segment 2 continues east across partially developed land 

and then converges to the north side of I-15 east of Barstow. East of Barstow, 

near Fort Irwin Road, the Segment separates into Alternatives A and B. 

x Alternative A diverges approximately 1⁄2 to 3⁄4 mile north from I-15 and travels 

parallel to the highway, crossing several roads, until re-converging with I-15 

east of Yermo. 

x Alternative B is planned to parallel the north side of I-15. 

x Alternatives A and B of Segment 2 meet at a common point east of Yermo, 

wherein Segment 3 begins. 

2.2.2.3. Segment 3, Alternatives A and B: Yermo to Mountain Pass, California (Figure 4) 

x Segment 3, the longest segment of the route at about 90 miles, is planned to 

parallel I-15. The segment begins east of Yermo and travels northeast through 

the Mojave River Valley, Cronese Valley, Soda Mountains, Soda Dry Lake, 

Baker, Halloran Springs, Halloran Summit, and Shadow Valley and ends at 

Mountain Pass in the Clark Mountain/Mescal Range. 

x Alternative A is planned to align along the median of I-15. 

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x Alternative B is planned to align along the northwest side of I-15. 

2.2.2.4. Segment 4, Alternatives A and B: Mountain Pass to near the State 

Line (Figure 5) 

x Segment 4 begins roughly at the summit of the Mountain Pass area and ends 

about 1⁄2 mile southwest of the California/Nevada state line. 

x Alternative A continues along the median of I-15 from the endpoint of Segment 3 and descends east from Mountain Pass. A wide, curving turn toward the 

northeast is planned to diverge from the I-15 median on the descent in the 

Wheaton Wash area. The Alignment re-converges with the median of I-15 and 

travels north/northeast into the Ivanpah Valley to near the state line. 

x Alternative B diverges north from I-15 near the summit of Mountain Pass and 

is planned to descend northward through the Clark Mountain Range utilizing 

two proposed tunnels. This alternative then descends into the Ivanpah Valley 

and meets with Alternative B at the endpoint of Segment 4.

2.2.2.5. Segment 5, Alternatives A and B: State Line to Sloan, Nevada (Figure 6) 

x Segment 5 is planned to parallel I-15 and begins southwest of the California/Nevada state line. The Alignment travels north/northeast in the Ivanpah 

Valley through Primm, Nevada, the Roach Dry Lake area, and Jean and ends 

near Sloan at the south end of the Las Vegas Valley. 

x Alternative A is planned to align along the median of I-15. 

x Alternative B is planned to align along the northwest or southeast side of I-15. 

2.2.2.6. Segment 6, Alternatives A, B, C, and D: Sloan to Las Vegas, Nevada 

(Figure 7) 

x Segment 6 begins in Sloan and travels north into the Las Vegas Valley and the 

city of Las Vegas. Four alternative routes, A, B, C, and D, are proposed as 

various alignments for this segment of the project. 

x Alternative A follows the median of I-15 from Sloan approximately to the intersection with Tropicana Avenue in Las Vegas. 

x Alternative B parallels the west side of I-15 from Sloan approximately to the 

intersection with Tropicana Avenue in Las Vegas. 

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x Alternative C diverges from I-15 at Sloan Road near the south end of Segment 6 and travels northwest. This alternative roughly follows an existing 

Union Pacific Railroad (UPRR) rail line and approximately 3 miles to the west 

of I-15, meets with and parallels this existing line. At a point to the south of 

Blue Diamond Boulevard, the alternative converges back toward I-15 utilizing 

the existing UPRR alignment and ends just south of the intersection with Flamingo Avenue. A maintenance facility is proposed on this alternative north of 

Blue Diamond Boulevard. 

x Alternative D is a branch of Alternative C that utilizes a different portion of the 

UPRR right-of-way. 

2.2.2.7. Segment 7, Alternatives A, B and C: Las Vegas, Nevada (Figure 7) 

x Segment 7 begins in the City of Las Vegas and travels north into across the Las 

Vegas Valley to the proposed Las Vegas Station. Three alternative routes, A, B 

and C are proposed as various alignments for this last segment of the project. 

x Alternative A follows the median of I-15 approximately from the intersection 

with Tropicana Avenue to the station in Las Vegas. 

x Alternative B parallels the west side of I-15 approximately from the intersection with Tropicana Avenue to the station in Las Vegas. 

x Alternative C follows an existing Union Pacific Railroad (UPRR) rail line located to the west of I-15 approximately from the intersection with Tropicana 

Avenue to the station in Las Vegas. 

3. AFFECTED ENVIRONMENT 

3.1. Regional Environment Description 

The study area consists of an approximately 200-mile-long alignment (hereinafter referred to 

as the “Alignment”) extending from the southern edge of the Mojave Desert in Victorville, 

California, northeast across the desert to Las Vegas, Nevada (Figure 1). The Alignment generally follows the I-15 transportation corridor. The Alignment begins at the northern edge of 

the urbanized Victorville area and passes through the cities of Barstow and Baker in 

San Bernardino County, California, and through the cities of Primm and Las Vegas in Clark 

County, Nevada. Outside of these cities, the Alignment generally crosses sparsely developed 

rural desert areas. 

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The proposed Alignment alternatives generally utilize the I-15 highway corridor except for: 

1) proposed alternatives northwest of I-15 between Victorville and Barstow, 2) a proposed 

tunneling alternative in the Clark Mountain Range north and west of I-15 in the Mountain 

Pass Area, and 3) proposed alternatives west of I-15 in the City of Las Vegas. 

The physical geography within the Alignment study area varies from low-lying valleys to 

higher elevation mountainous areas. Much of the Alignment region lies between elevations 

of about 2,000 and 4,000 feet above mean sea level (MSL). The lowest elevation point on 

the Alignment is at approximate elevation 920 feet MSL in Baker, California. The highest 

point on the Alignment is at the summit of the Mountain Pass area at an approximate elevation of 4,600 feet MSL. 

The Alignment begins at about elevation 3,000 feet MSL in Victorville and descends to Barstow to an elevation of about 2,100 feet MSL. From Barstow to Baker, the Alignment 

descends along the Mojave River Valley, Cronese Valley, Soda Mountains, and Soda Dry 

Lake to Baker at an elevation of about 920 feet MSL. From Baker, the Alignment ascends 

the Halloran Springs Valley and Halloran Summit at an elevation of about 4,100 feet MSL. 

Between Halloran Summit and Mountain Pass, the Alignment descends into Shadow Valley 

to an elevation of approximately 3,750 feet MSL. At Mountain Pass, the highest point on the 

Alignment, elevations close to 4,600 feet above MSL are attained. From Mountain Pass, the 

Alignment descends to the Ivanpah Valley to an approximate elevation of 2,600 feet MSL. 

The Alignment reaches elevations of approximately 2,600 to 2,800 feet MSL along the 

Ivanpah Valley between Primm and Sloan, Nevada, and then descends into the Las Vegas 

Valley to an approximate elevation of 2,000 feet MSL at the proposed Las Vegas station locations. 

The Mojave River, which is the major drainage crossing the region, originates in the 

San Bernardino Mountains and flows for about 100 miles northeast and through the southwest region of the Alignment study area. The Mojave River ends in Soda Lake near Baker, 

California. Much of the time flow in the Mojave River is underground, except where shallow bedrock causes the water to surface or during periods of high rainfall (County of San 

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Bernardino, 2005d). In general, the groundwater table in the region is generally deep, typically on the order of a few hundred feet, although some exceptions do occur (County of San 

Bernardino, 2005d). A crossing of the Mojave River west of Barstow is planned for the 

Alignment. 

Surface conditions over much of the Alignment consist of open desert terrain comprising extensive soil and rock exposures. Numerous ephemeral (seasonal) streams and relatively 

shallow drainages traverse the Alignment. Many of these streams and drainages are dry and 

typically have relatively limited duration water flow during the rainy season in response to 

precipitation. The ground surface along the Alignment generally contains sparse desert vegetation, which typically consists of cactus, shrubs, and native grasses. Annual precipitation 

amounts vary across the Alignment region. Based on rainfall data for selected locations 

along the Alignment obtained from San Bernardino and Clark Counties, annual precipitation 

varies in the following ranges at the locations indicated on the following Table 1: 

Table 1 – Range of Annual Rainfall Totals at Selected Alignment Locations 

Alignment 

Segment & 

Alternative

Rainfall Station 

Location

Rainfall Record 

Years

Range Of Annual

Rainfall Totals

(Inches)

1a And B Victorville 1939 To 2006 1.23 To 15.98 

2a Barstow 1960 To 2006 1.11 To 11.27 

2a, 2b, 3a, And 3b Yermo 1961 To 2006 0.36 To 8.03 

3a And 3b Baker 1956 To 2006 0.40 To 7.52 

4a And 4b Mountain Pass 1954 To 2006 2.29 To 14.32 

5a And 5b Jean 1990 To 2006 0.16 To 8.38 

6a, 6b, 6c, And 6d Las Vegas (South) 1989 To 2006 0.44 To 9.10 

6a, 6b, 6c, And 6d Las Vegas (North) 1989 To 2006 0.64 To 7.09 

7a, 7b, And 7c Las Vegas (North) 1989 To 2006 0.64 To 7.09 

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3.2. Regional Geology 

The Alignment is located within two geomorphic regions characterized by the morphology 

of the landforms, the general type and age of the geologic materials, and by the tectonicstructural features of the geology in the region. The California portion of the Alignment is 

within the Mojave Desert Geomorphic Province, and the Nevada portion of the Alignment is 

within the Basin and Range Geomorphic Province. These provinces have a transitional 

physiographic change, although generally the state line is a commonly used boundary. 

Both regions are characterized by mountain ranges and hills of moderate relief that are partially buried and separated by broad alluviated basins. The Basin and Range province 

includes a large part of the southwestern United States in which elongate mountain ranges 

are separated by broad, nearly flat valleys (Norris and Webb, 1990). In contrast, valleys in 

the Mojave Desert province are proportionally broader and mountains are more widely 

spaced and the mountains generally do not stand as high above their surroundings. Mountain 

ranges in the Mojave Desert province show less consistency in orientation than those of the 

Basin and Range province (Norris and Webb, 1990). 

The mountain ranges and hills of the Alignment region are comprised primarily of Mesozoic 

era (65 to 245 million years old) granitic and volcanic rocks and Paleozoic era (245 to 

570 million years old) metamorphic rocks. These rocks generally include Mesozoic era 

granite, quartz monzonite, and porphyritic volcanic rocks and Paleozoic era gneiss and limestone. Some Tertiary age (2 to 65 million years old) surface exposures of non-marine 

volcanic and sedimentary rocks are mapped along the Alignment in Segment 2 east of Barstow, in Segment 3 in the Soda Mountains, and in Segment 5 in the Jean Hills area. 

Valleys, drainage areas, and alluvial fans along the flanks of mountains and valleys within 

the Alignment are underlain at depth by the basement rocks described above but have been 

filled by Quaternary age (last 2 million years) alluvium and other sediments. The Quaternary 

deposits are generally subdivided into two stratigraphic units according to relative age: 

younger Holocene deposits (last 11,000 years) and older Pleistocene (11,000 to 2 million 

years ago) age deposits. Holocene deposits typically consisting of relatively young, poorly 

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consolidated or unconsolidated silt, sand, and gravel are anticipated to be present in washes, 

valley bottoms, lake beds, and include river sands and Aeolian (wind-blown) sands. Pleistocene age alluvial deposits generally consist of gravel, sand, silt, and clay that is moderately 

to well consolidated and often slightly cemented. These materials include older alluvial fan 

deposits, continental terrace deposits, and older lacustrine (lake) or playa deposits. 

The majority of the Alignment extends across alluviated areas in the Mojave River Valley, 

Cronese Valley, the Baker/Halloran Springs Valley, Shadow Valley, Ivanpah Valley, and the 

Las Vegas Valley. Within these areas, much of the Alignment is underlain by Quaternary alluvial sediments, with the exception of local outcrops and exposures of rock units. Geologic 

maps reviewed indicate that some segments of the Alignment are underlain by shallow rock 

formations that may be encountered at the ground surface. Regional geologic maps showing 

the geology and the Alignment routes are shown on Figures 8, 9, 10, and 11. The surficial 

geology of each segment of the Alignment is described in more detail in the following sections.

3.3. Resources by Segment 

The following sections describe the geology along the Alignment within each proposed alternative segment of the route. Each section contains a table listing the geologic unit type 

and the age and description of geologic units mapped within that segment of the Alignment. 

The various symbols listed for the geologic units and descriptions of the units are inclusive 

of the various geologic maps and references reviewed. Geologic information was obtained 

from published geologic maps and references and is supplemented by information from Caltrans geotechnical borings for investigations for crossing structures along I-15 reported on 

Log of Test Borings (LOTB) sheets from CalTrans As-Built plans for I-15. The Caltrans boring locations are limited to crossing structures located along I-15. A discussion of the 

surficial geologic setting of each segment interpreted from the published maps and Caltrans 

LOTB sheets is included in the section along with the table. 

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The presence of artificial fill soils is anticipated at various locations along the Alignment. 

Fill associated with mining activities, private properties, roadway construction, utility trench 

backfill, retaining wall backfill, and general grading of right-of-way areas for I-15 should be 

anticipated. The presence of these fill soils is anticipated but was not specifically evaluated 

as part of the scope of this study. Fill soils are included in our description of the surficial geology of the Alignment where indicated on published geologic maps. 

3.3.1. Segment 1, Alternative A (Victorville to Lenwood, California) 

Alternative A begins below the southeast flank of Quartzite Mountain at the proposed 

Victorville station on the southeast side of Bell Mountain Wash. This route travels west 

across Bell Mountain Wash and across the southern flank of Quartzite Mountain to the 

east bank of the Mojave River. The segment then travels north and northeast along the 

east/southeast bank of the river meeting the beginning of Segment 2 about 21⁄2 miles 

southwest of Lenwood. The segment crosses the inferred, concealed trace of a potentially active portion of the Helendale-South Lockhart fault northeast of the community 

of Helendale. 

Geologic maps indicate that this segment is underlain primarily by alluvial deposits that 

are present along the banks of the Mojave River. The alluvial deposits include younger 

Holocene river sediments (Qrs, Qw) and valley sediments (Q, Qa) and older Pleistocene 

valley and fan sediments (Qo, Qoa, Qod), marl (Qoc) and alluvial fanglomerate deposits 

(Qof). Some areas of Holocene Aeolian (wind-blown) sands (Qs) are mapped near the 

north end of Segment 1. 

The geologic maps indicate that Alternative A is underlain at depth by older Mesozoic 

age igneous quartz monzonite (granitic) rocks (KJqm, qm), metamorphic rocks comprised of gneiss (gg), and metavolcanic porphyritic rock (Mzv, lp; a rock comprising 

large mineral crystals in a fine-grained groundmass). These rocks underlie the alluvial 

deposits along this segment and are mapped at the surface along a portion of the southern end of this alternative segment and in outcrops along the east side of the Mojave 

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River. A table listing the geologic unit, geologic age, and description of the unit is presented below. A geologic map of Segment 1, Alternative A, showing the geology and 

the Alignment route is shown on Figure 8. 

Table 2 – Geologic Units Segment 1, Alternative A 

Geologic Unit (Symbol[s]) Geologic Age Description

Aeolian Deposits (Qs) Holocene Wind-Blown Sand 

Younger Alluvial Valley 

Sediments (Q, Qa) Holocene Unconsolidated, Poorly Sorted Alluvial Silt, Sand And Gravel Sediments. 

Younger Alluvial River/ 

Wash Deposits (Qw, Qrs) Holocene Alluvial Wash Deposits; Mojave River Sand. 

Older Alluvial Valley And 

Fan Sediments

(Qo, Qoa, Qod) 

Pleistocene

Weakly Consolidated Dissected Alluvial 

Gravel, Sand, And Silt Derived Mainly 

From 

Granitic And Metamorphic Rocks Of San

Gabriel And San Bernardino Mountains. 

Older Alluvial 

Fanglomerate (Qof) Pleistocene

Cobble Fanglomerate And Gravel Derived

From Metavolcanic Rocks. 

Older Alluvial Valley 

Sediments (Qoc) Pleistocene Marl (Clay). 

Quartz Monzonite 

(Kjqm, Qm) 

Cretaceous - 

Late Jurassic Intrusive Igneous (Granitic) Rock. 

Metavolcanic Rocks 

(Mzv, Lp) Mesozoic

Porphyritic Volcanic And Metavolcanic 

Rocks. Includes Sidewinder Volcanic 

Series Of Bowen, 1954, And Oro Grande 

Of Hershey, 1902. 

Granite Gneiss (Gg) Paleozoic Metamorphosed Granitic Rock Or Similar

Composition Volcanic Rock. 

3.3.2. Segment 1, Alternative B (Victorville to Lenwood, California) 

Alternative B begins below the southeast flank of Quartzite Mountain at the proposed 

Victorville station on the southeast side of Bell Mountain Wash. This route travels 

northeast across Bell Mountain Wash and along the eastern flank of Quartzite Mountain 

into Sidewinder Valley. North of Sidewinder Valley, this alternative crosses the trace of 

the active Helendale-South Lockhart fault, indicated by an abrupt change in the mapped 

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alluvial units. The segment then travels north and meets with Alternative A on the southeast bank of the Mojave River at the end of Segment 1. 

The geologic maps indicate that Alternative B is underlain by both alluvial sediments 

and older Mesozoic age granitic, volcanic, and metavolcanic rocks. The alluvial deposits include younger Holocene wash sediments (Qw) and valley sediments (Q, Qa); and 

older Pleistocene valley and fan sediments (Qo, Qoa, Qod), and alluvial fanglomerate 

deposits (Qof). Exposed within portions of this segment and underlying the alluvial 

sediments at a relatively shallow depth are granitic quartz monzonite, hornblende diorite-gabbro and granite (KJqm, qm, gqm, hd), and porphyritic metavolcanic rock 

(Mzv, lp, pf). 

Caltrans LOTB sheets from investigations for I-15 crossing structures indicate that borings located along this segment at Stoddard Wells Road, Cement Company 

Undercrossing, Bell Mountain Wash, Wild Wash, and Hodge Road encountered alluvial 

sands and gravel of varying density. Weathered granitic rock was encountered in borings at Wild Wash Bridge at depths ranging from 10 to 19 feet below ground surface 

(bgs) and at a depth of 28 feet bgs in a boring located at Bell Mountain Wash Bridge. 

A table listing the geologic unit, geologic age, and description of the unit is presented 

below. A geologic map of Segment 1, Alternative B, showing the geology and the 

Alignment route is shown on Figure 8. 

Table 3 – Geologic Units Segment 1, Alternative B 

Geologic Unit (Symbol[s]) Geologic Age Description

Younger Alluvial Valley 

Sediments (Q, Qa) Holocene Unconsolidated, Poorly Sorted Alluvial Silt, Sand, And Gravel Sediments. 

Younger Alluvial Wash 

Deposits (Qw) Holocene Alluvial Wash Deposits. 

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Older Alluvial Valley And 

Fan Sediments 

(Qo, Qoa, Qod) 

Pleistocene

Weakly Consolidated Dissected Alluvial 

Gravel, Sand, And Silt Derived Mainly From 

Granitic And Metamorphic Rocks Of San 

Gabriel And San Bernardino Mountains. 

Older Alluvial Fanglomerate 

(Qof) Pleistocene Cobble Fanglomerate And Gravel Derived From Metavolcanic Rocks. 

Quartz Monzonite 

(Kjqm, Qm, Gqm, Hd) 

Cretaceous - 

Late Jurassic 

Intrusive Igneous (Granitic) Rock, Quartz 

Monzonite, Hornblende Diorite-Gabbro, 

And Granite. 

Metavolcanic Rocks 

(Mzv, Lp, Pf) Mesozoic 

Porphyritic Volcanic And Metavolcanic 

Rocks. Includes Sidewinder Volcanic 

Series Of Bowen, 1954, And Oro Grande 

Of Hershey, 1902. 

3.3.3. Segment 2, Alternative A (Lenwood to Yermo, California) 

Alternative A begins on the southeast bank of the Mojave River about 21⁄2 miles southwest of the community of Lenwood southwest of Barstow. This segment travels 

northeast across the broad southeast river bank toward the Mojave River and crosses the 

river north of Lenwood on a planned new bridge. The segment crosses the active zone 

of the Lenwood-Lockhart-Old Woman Springs fault north of Lenwood. Fault maps indicate that this fault has experienced creep near the community of Lenwood in historic 

time. On the north side of the Mojave River, this segment turns east and travels along 

the north river bank and wash areas of the Mojave River through the City of Barstow. 

On the north side of the river, the segment crosses the concealed trace of the active 

Mt. General fault and crosses the concealed trace of a potentially active portion of the 

Gravel Hills-Harper Lake fault. On the east side of Barstow, the segment continues 

eastward along the north side of the Mojave River valley as the river bends toward the 

south/southeast. The segment crosses a small drainage valley between Barstow and 

Yermo and ends on the southeast flank of the Calico Mountains east of Yermo. 

The geologic units that underlie this segment of the Alignment can be divided into three 

areas: 1) Mojave River sediments along the southeast and north banks of the river, 2) an 

exposure of sedimentary and volcanic rocks east of Barstow, and 3) valley alluvium 

sediments in the small drainage valley west of Yermo. 

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The geologic maps indicate that the southeast bank of the Mojave River at the beginning of Alternative A and a small area of the north river bank at the planned bridge 

crossing is underlain by deposits of Aeolian sands (Qs). On the north side of the Mojave 

River, this segment is underlain by both river sands (Qrs, Qw) and alluvial valley deposits (Q, Qa) and is underlain at depth by older Mesozoic age granitic rocks (Jhd, qm, hd) 

and Paleozoic age metamorphic gneiss (wg) that are exposed within portions of this 

segment and underlying the alluvial sediments at a relatively shallow depth. East of the 

Mojave River, the segment crosses an area of older alluvial valley sediments (Qof, Qoc, 

QT) that are present in the small drainage valley. 

The exposure of Tertiary age rock (Mc, Mi, Tt, Tat, Tls, Td, Ts, Tsl) that this segment 

crosses east of Barstow is mapped as a formation of volcanic and sedimentary rocks and 

is described in Table 4. In the small drainage valley east of this rock exposure, the segment crosses alluvial deposits consisting of young fan and valley sediments (Q, Qa), 

and a mapped clay unit deposited from a playa or small lake bed (Qc, Ql). Northeast of 

Yermo, the end of this segment is underlain by older alluvium (Qo, Qoa) and fan gravel 

(Qf) on the southeast flank of the Calico Mountains. This older alluvium and fan gravel 

mantles the formational Tertiary volcanic and sedimentary rock that comprises the Calico Mountains. 

Caltrans LOTB sheets from investigations for I-15 crossing structures indicate that two 

borings located along this segment at Hiker Ditch Bridge, located at the interchange of 

I-15 and Old Highway 58, encountered sandy to clayey gravel, gravelly sand, and silt to 

depths ranging from 27 to 34 feet bgs. Sandy claystone to clayey siltstone was encountered in these borings between 27 and 58 feet bgs, and highly weathered rhyodacite rock 

(intrusive volcanic rock) was encountered at depths below 53 feet. 

A table listing the geologic unit, geologic age, and description of the unit is presented 

below. A geologic map of Segment 2, Alternative A, showing the geology and the 

Alignment route is shown on Figure 8. 

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Table 4 – Geologic Units Segment 2, Alternative A 

Geologic Unit (Symbol[s]) Geologic Age Description

Aeolian Deposits (Qs) Holocene Wind-Blown Sand. 

Younger Alluvial River/ 

Wash Sediments (Qrs, Qw) Holocene

Alluvial Wash Sediments And River 

Sand;

Mojave River Sand. 

Younger Alluvial Valley/ 

Fan Sediments (Q, Qa) Holocene Unconsolidated, Poorly Sorted Alluvial 

Silt, Sand, And Gravel Sediments. 

Younger Alluvial Valley 

Sediments (Ql, Qc) Holocene Lake Deposits, Clay Of Small Playas. 

Younger Alluvial Fan 

Sediments (Qf) Holocene Fan Gravel. 

Older Alluvial Sediments 

(Qo, Qoa) Pleistocene

Dissected Alluvial Fan Material Composed

Of Gravel, Sand, And Some Boulders. 

Older Alluvial Valley 

Sediments (Qof, Qoc, Qt) Pleistocene

Fanglomerate And Gravel (Qof); Clay 

And

Marl (Qoc); Continental Deposits Of 

Gravel, Sand, Silt And Clay (Qt). 

Volcanic And Sedimentary 

Rocks (Mc, Mi, Tt, Tat, Tls, 

Td, Ts, Tsl) 

Tertiary 

Miocene Continental Deposits And 

Intrusive Rocks; Tuff Breccia; Dacite

Breccia; Limestone, Shale And Tuff; 

Dacite;

Interbedded Shale And Sandstone. 

Granitic Rocks (Jhd, Qm, Hd) Cretaceous - 

Late Jurassic 

Intrusive Igneous (Granitic) Hornblende 

Diorite-Gabbro Rock; Quartz Monzonite. 

Metavolcanic Rocks 

(Mzv, Ql, Ap) Mesozoic Porphyritic Volcanic And Metavolcanic 

Rocks, Andesite To Latite Porphyry. 

Granitic Gneiss (Wg) Paleozoic Waterman Gneiss Of Bowen, 1954: 

Metamorphosed Quartz Diorite Gneiss. 

3.3.4. Segment 2, Alternative B (Barstow to Yermo, California) 

Alternative B is a branch of Alternative A that begins on the west side of the small 

drainage valley east of Barstow. This alternative segment travels parallel to Alternative 

A and approximately 3⁄4 mile to the south, crossing a small drainage valley area before 

re-connecting with Alternative A at the end of Segment 2 east of Yermo. 

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The geologic maps indicate that the beginning of this segment is underlain by a formation of volcanic and sedimentary rocks (Mc, Mi, Tt, Tat, Tls, Td, Ts, Tsl) described 

below in Table 5. East of the rock formation area in the small drainage valley, this segment is underlain by young valley sediments (Q, Qa). The segment crosses the east 

finger of the mapped clay unit (Ql, Qc) that also underlies Alternative A. Northeast of 

Yermo, Alternative B is underlain by older fan gravel (Qf) on the southeast flank of the 

Calico Mountains. The older fan gravel unit mantles the formational Tertiary volcanic 

and sedimentary rock that comprises the Calico Mountains. 

Caltrans LOTB sheets from investigations for I-15 crossing structures indicate that borings located along this segment at Calico Road Undercrossing (Ghost Town Road), 

Calico Road, First Street, Yermo Ditch Bridge, and East Yermo Overcrossing encountered alluvial sands and gravel of varying density, and some interbedded clay. Bedrock 

was not encountered in borings along this segment to depths explored ranging from 

34 to 60 feet. 

A table listing the geologic unit, geologic age, and description of the unit is presented 

below. A geologic map of Segment 2, Alternative B, showing the geology and the 

Alignment route is shown on Figure 8. 

Table 5 – Geologic Units Segment 2, Alternative B 

Geologic Unit (Symbol[s]) Geologic Age Description

Younger Alluvial Valley/ 

Fan Sediments (Q, Qa) Holocene Unconsolidated, Poorly Sorted Alluvial Silt, Sand And Gravel Sediments. 

Younger Alluvial Valley 

Sediments (Ql, Qc) Holocene Lake Deposits, Clay of Small Playas. 

Younger Alluvial Fan 

Sediments (Qf) Holocene Fan Gravel. 

Volcanic And Sedimentary 

Rocks (Mc, Mi, Tt, Tat, 

Tab, Tls) 

Tertiary 

Miocene Continental Deposits And 

Intrusive Rocks; Tuff Breccia; Andesite

Breccia; Dacite Breccia; Limestone, Shale

And Tuff.

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3.3.5. Segment 3, Alternatives A and B (Yermo to Mountain Pass, California) 

Alternatives A and B of Segment 3 are in close proximity to each other, on the median 

and northwest sides of I-15, respectively, and they have been evaluated as one alignment for purposes of describing general geologic conditions along that segment. 

Segment 3 begins on the southeast flank of the Calico Mountains, east of Yermo, and 

travels northeast through the alluviated Mojave River Valley, Manix lake beds, older alluviated areas between the Mojave River Valley and Cronese Valley, the alluviated 

Cronese Valley, Soda Mountains, alluviated Soda Dry Lake and Halloran Springs area, 

Halloran Summit, Shadow Valley, and Mountain Pass area. Segment 3 crosses the concealed trace of the active Calico-Hidalgo fault near the beginning east of Yermo. 

Between Yermo and Manix, the segment crosses the west/southwestern end of the active 

Manix fault. 

The geologic maps indicate that the beginning part Segment 3 in the Mojave River Valley southwest of Manix is underlain primarily by younger alluvial valley and fan 

sediments (Q, Qa, Qal, Qf), and partially by older fanglomerate and gravel alluvium in 

local outcrops (Qof, QT). Northeast of Manix, the Alignment is underlain by Manix 

Lake Beds sand and silt sediments (Qms, Qol), by younger river sand (Qrs, Qw) from 

tributary channels of the Mojave River, and by an area of older alluvium. Further northeast, the Alignment continues through the Mojave River Valley and is underlain by 

younger valley alluvial sediments (Qal) and lacustrine (lake) deposits (Ql). 

At the northeast end of the Mojave River Valley, the Alignment crosses areas shown on 

the geologic maps to be underlain by older Pliocene-Pleistocene sediments of varying 

composition (Qc, QP). The Alignment turns east traveling along the south side of the 

Cronese Mountains. In this portion of Segment 3, the geologic maps show that the 

Alignment is primarily underlain by younger alluvial sediments (Qal) and partially by 

exposures of Tertiary-Mesozoic age granitic rocks (gr, gr-m, TKq). These granitic rocks 

are also mapped on the south side of the Cronese Valley and underlie the segment at 

depth in this area beneath alluviated areas. The predominant unit mapped along this 

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segment in the Cronese Valley is younger alluvium (Qal). The geologic maps indicate 

that a concealed, potentially active, unnamed fault is located skew to the Alignment in 

the Cronese Valley. 

In the Soda Mountains area between the Cronese Valley and Baker, geologic maps indicate that the Alignment is underlain by younger valley and alluvial fan deposits (Qal), 

older Pliocene-Pleistocene sediments of varying composition (Qc, QP), and by Tertiary 

age volcanic and sedimentary rocks (Tv, Tc). Along this portion of Segment 3, exposures of Tertiary-Mesozoic age granitic rocks (gr, TKq) are mapped on the southeast 

side of the Alignment. The geologic maps indicate that the Alignment crosses the potentially active Baker fault on the east side of the Soda Mountains approximately 6 miles 

southwest of Baker. In Baker, the geologic maps indicate the Alignment is underlain by 

younger lacustrine Soda Lake Bed sediments (Ql). 

Caltrans LOTB sheets from investigations for I-15 crossing structures indicate that borings located along Segment 3 between Yermo and Baker generally encountered alluvial 

and other soil deposits predominantly consisting of sands and gravel of varying density, 

and some interbedded clay and silt; some dune sands were also encountered. Dense 

sandstone and hard, calcareous mudstone was encountered in a boring at Afton Road 

Overcrossing at a depth of 7 feet bgs. Granitic rock was encountered in two borings at 

Basin Road Overcrossing at depths of 11 feet and 25 feet bgs. 

Northeast of Baker, the Alignment travels adjacent to Halloran Wash and ascends a 

broad, sloping alluvial fan that flanks the southwest side of the Halloran Summit. Between Baker and Halloran Springs, the Alignment is underlain by younger valley and 

alluvial fan deposits (Qal). The Halloran Summit area is shown on the geologic maps to 

be comprised of a large body of Tertiary-Mesozoic age granitic rock (gr, TKq) that is 

overlain by younger Pleistocene age volcanic basalt flows (Qpv, Qeb). The granitic rock 

body is intruded into an older, Precambrian metamorphic rock unit comprised of gneiss 

(epȯ, pȯg) that is mapped on the west side of the Halloran Summit. The geologic maps 

indicate that the Alignment is underlain by the gneissic rock and younger alluvium 

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(Qal) on the west side of the summit. Younger alluvium is mapped within the 

I-15/Alignment corridor pass through the Halloran Summit but is underlain at a relatively shallow depth by the granitic and/or volcanic rock. The inactive Halloran fault is 

mapped in this corridor pass parallel to I-15. 

Caltrans LOTB sheets from investigations for I-15 crossing structures indicate that borings located along Segment 3 between Baker and Halloran Summit generally 

encountered alluvial and other soil deposits predominantly consisting of sands and 

gravel of varying density, and some interbedded clay and silt. Basalt and volcanic breccia was encountered in borings at Dale Ditch at depths ranging from 5 to 20 feet bgs. 

Granitic rock was encountered in several borings at Kali Ditch Bridge at depths ranging 

from 5 to 23 feet bgs. 

In Shadow Valley between Halloran Summit and Mountain Pass, younger valley and fan 

alluvium (Qal) underlies much of the Alignment. A small exposure of Paleozoic age 

dolomite (IP/ls, Dȯg, Dȯgb1) is mapped on the southwest side of Shadow Valley, and 

younger lacustrine deposits (Ql) from the Valley Wells lake bed are mapped on the valley bottom. Ascending from Shadow Valley up to Mountain Pass, the Alignment crosses 

Pliocene-Pleistocene non-marine sediments (Qc, Qoa) that are mapped along the base of 

the Mescal Range and Clark Mountain Range that comprise the Mountain Pass area. 

Caltrans LOTB sheets from investigations for I-15 crossing structures indicate that borings located along Segment 3 in the Shadow Valley area generally encountered alluvial 

and other soil deposits predominantly consisting of sands and gravel of varying density, 

and some interbedded clay and silt. Underlying the alluvium in Shadow Valley in the 

vicinity of Valley Wells, Caltrans borings encountered a sedimentary rock formation 

comprised of interbedded sandstone, conglomerate, siltstone, and claystone. This formation was encountered at Hot Wash Bridge at approximate depths ranging from 42 to 

61 feet bgs, at West Valley Wells Ditch Bridge at approximate depths ranging from 78 to 

83 feet bgs, at Valley Wells Ditch Bridge at approximate depths ranging from 10 to 

53 feet bgs, at Windmill Station Ditch Bridge at approximate depths ranging from 15 to 

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22 feet bgs, and at Wells Ditch Bridge at approximate depths ranging from 4 to 

12 feet bgs. A Caltrans boring at Cima Road Overcrossing in the Valley Wells area encountered travertine (limestone) at a depth of approximately 7 feet bgs. 

The Mountain Pass area in Segment 3 is comprised of a block of Precambrian age metamorphic rocks (epȯ, pȯg, pȯgr, pȯga, pȯgc, pȯgb) comprised chiefly of injection 

gneiss, granite gneiss, and granite augen gneiss (Olson, 1951). This rock is bounded on 

the east by alluvium of the Ivanpah Valley and is separated from Mesozoic and Paleozoic age metasedimentary and metavolcanic rocks (IP/ls, CM, Dȯg, Dȯgu, Ds, Dsi) to 

the west by the inactive Clark Mountain fault. Inactive faults crossed by the Alignment 

in the Mountain Pass area, as shown on the geologic maps, include the Mesquite Thrust 

fault, Clark Mountain fault, Middle fault, and North fault. 

The geologic maps indicate that in the Mountain Pass area, the Alignment is mostly underlain by younger alluvium (Qal) and older alluvial fan deposits (Qc, Qoa) that are 

present in the I-15 corridor through the pass. The maps indicate that rock units also underlie the Alignment at the surface in some areas. These rock units underlie the 

Alignment at a relatively shallow depth through the pass. West of the Clark Mountain 

fault, the Alignment is underlain at depth by Paleozoic age dolomite and limestone with 

thin interbedded shale and sandstone (IP/ls, CM, Dȯg, Dȯgu, Ds, Dsi). East of the 

Clark Mountain fault at the end of Segment 3, the maps indicate that the Alignment is 

underlain by the metamorphic gneiss unit (epȯ, pȯg, pȯgr, pȯga, pȯgc, pȯgb).

Caltrans LOTB sheets from investigations for I-15 crossing structures indicate that borings located along Segment 3 in the Mountain Pass area generally encountered alluvial 

and other soil deposits predominantly consisting of sands and gravel of varying density. 

Metamorphosed volcanic rock (meta-dacite and meta-basalt), gneiss, and schist were 

encountered in borings at Bailey Road Overcrossing at depths ranging from 7 to 

8 feet bgs. Metamorphic igneous rock (gneiss) was encountered in two borings at Cenda 

Ditch Bridge at depths ranging from 3 to 8 feet bgs. 

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A table listing the geologic unit, geologic age, and description of the unit is presented 

below. Geologic maps of Segment 3, Alternatives A and B, showing the geology and the 

Alignment routes are shown on Figures 8, 9 and 10. 

Table 6 – Geologic Units Segment 3, Alternatives A and B 

Geologic Unit (Symbol[s]) Geologic Age Description

Younger Alluvial Valley and 

Fan Sediments (Q, Qa, Qal) Holocene

Unconsolidated Valley Alluvial Deposits 

of Silt, Sand, and Gravel; Alluvial Fan 

Deposits.

Younger Alluvial River/ 

Wash Sediments (Qw, Qrs) Holocene Alluvial Wash Sediments and River Sand. 

Younger Alluvial Fan 

Sediments (Qf) Holocene Fan Gravel. 

Younger Lacustrine Deposits 

(Ql) Holocene

Lake And Playa Sediments Including 

Clay, Silt, and Fine Sand; Soda Lake 

Bed Sediments. 

Older Alluvial Valley 

Sediments (Qof, Qt) Pleistocene

Fanglomerate And Gravel (Qof); 

Continental Deposits of Gravel, Sand, 

Silt, and Clay (Qt). 

Older Lacustrine Deposits 

(Qms, Qol) Pleistocene Manix Lake Bed Sediments, Including Silt and Fine Sand.

Volcanic Rocks (Qpv, Qeb) Pleistocene Undifferentiated Volcanic Basalt Flows. 

Older Alluvial Deposits 

(Qc, Qp, Qo, Qoa, Qt) 

Pleistocene

And PlioPleistocene

Dissected Alluvial Gravel, Sand, And 

Silt; Continental Terrace Deposits of 

Gravel, Sand, Silt, and Clay. 

Volcanic And Sedimentary 

Rocks (Tv, Tc) Tertiary Undivided Continental Sedimentary Rocks and Volcanic Rhyolite Flows. 

Granitic Rocks (Gr, Tkq) Tertiary/ 

Mesozoic

Intrusive Igneous Rock; Includes 

Teutonia Quartz Monzonite of Hewett, 

1956. 

Granitic and Metamorphic 

Rock (Gr-M) Mesozoic Granitic And Metamorphic Rock. 

Marine Sedimentary and 

Metasedimentary Rocks (Cm) 

Paleozoic - 

Mississippian

Limestone And Dolomite; Includes 

Monte Cristo Limestone of Hewett, 1956. 

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Table 6 – Geologic Units Segment 3, Alternatives A and B 

Geologic Unit (Symbol[s]) Geologic Age Description

Marine Sedimentary and 

Metasedimentary Rocks 

(Ds, Dsv, Dsi) 

Paleozoic - 

Devonian

Sultan Limestone of Hewett, 1956, 

Including Valentine Limestone And 

Ironside Dolomite Members. 

Marine Sedimentary and 

Metasedimentary Rocks 

(Ip/Ls, Dɽg, Dɽgu, Dɽgb1) 

Paleozoic – 

Cambrian And 

Devonian

Dolomite and Limestone With Thin 

Interbedded Shale and Sandstone; 

Goodsprings Dolomite and Carbonate 

Rocks Including Breccia of Hewett, 

1956. 

Metamorphic Rocks 

(Epɽ, Pɽg, Pɽga, Pɽgc,

Pɽgb)

Precambrian 

Undifferentiated Injection Gneiss, Schist, 

Granitic Gneiss, Granite Augen Gneiss 

Complex. 

Granitic Rocks (Pɽgr) Precambrian 

Undivided Syenite, Shonkite, Granite 

Stocks, And Dikes, Including Carbonate 

Veins and Irregular Bodies In Mountain 

Pass Area. 

3.3.6. Segment 4, Alternative A (Mountain Pass to State Line) 

Alternative A begins in the Mountain Pass area at the end of Segment 3 and descends 

east along the I-15 corridor adjacent to Wheaton Wash, and then northeast into the Ivanpah Valley. The segment crosses Ivanpah Dry Lake and ends just west of the Nevada 

state line in Ivanpah Valley. 

The geologic maps indicate that the beginning part of Alternative A in the Mountain 

Pass area is underlain by Precambrian age metamorphic rocks (epȯ, pȯg) comprised 

chiefly of injection gneisses and granitic gneisses and is also underlain by valley alluvium (Qal) and shallow wash alluvium from Wheaton Wash (Qal). In the Ivanpah 

Valley, the Alignment is underlain by younger valley alluvium (Qal) and lake deposits 

from Ivanpah Dry Lake (Ql). 

Caltrans LOTB sheets from investigations for I-15 crossing structures indicate that borings located along Alternative A between the Mountain Pass area and the Nevada state 

line generally encountered alluvial and other soil deposits predominantly consisting of 

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sands and gravel of varying density. Metamorphic gneiss and schist were encountered in 

borings at Wheaton Springs Wash Bridge at depths ranging from 6 to 29 feet bgs. 

A table listing the geologic unit, geologic age, and description of the unit is presented 

below. A geologic map of Segment 4, Alternative A, showing the geology and the 

Alignment route is shown on Figure 10. 

Table 7 – Geologic Units Segment 4, Alternative A 

Geologic Unit (Symbol[s]) Geologic Age Description 

Younger Alluvial Deposits 

(Qal) Holocene

Unconsolidated Valley Alluvial Deposits

of Silt, Sand And Gravel; Alluvial 

Stream/Wash Deposits. 

Younger Lacustrine Deposits 

(Ql) Holocene

Lake And Playa Sediments Including 

Clay, Silt and Fine Sand; Ivanpah Lake 

Bed Sediments. 

Metamorphic Rocks 

(Epɽ, Pɽg) Precambrian 

Undifferentiated Injection Gneiss, 

Schist, Granitic Gneiss, Granite Augen 

Gneiss Complex. 

3.3.7. Segment 4, Alternative B (Mountain Pass to State Line) 

Alternative B begins in the Mountain Pass area at the end of Segment 3 along I-15 and 

diverges north from the I-15 corridor across the east side of the Clark Mountain Range. 

Two tunnels in the mountain range are currently proposed for this segment. North of the 

proposed tunnels, approximately 2 miles north of I-15, this segment turns east/northeast 

and descends along the northeast flank alluvial fan of the Clark Mountains and into the 

Ivanpah Valley, re-connecting with the I-15 corridor at the end of the Segment 4 just 

west of the Nevada state line. 

The geologic maps indicate that the beginning part of this segment in the Mountain Pass 

area is underlain by Precambrian age metamorphic rocks comprised chiefly of injection 

gneisses and granitic gneisses (epȯ, pȯg). The maps show that this area consists of 

former mining prospects, but no mines are located on the maps in this area. Significant 

mining activities in the Mountain Pass District are located west and southwest of this 

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segment. The maps indicate that tunneling through this area along the planned alignment will pass through the metamorphic gneiss unit and will cross the inactive North 

fault in the Clark Mountains. 

On the northeast flank of the Clark Mountains, this segment descends over younger alluvial fan deposits (Qal) which are underlain at a relatively shallow depth by the 

metamorphic rocks. In the Ivanpah Valley, the segment is underlain by younger valley 

alluvium (Qal), lake deposits from Ivanpah Dry Lake (Ql), and a rocky outcrop of 

metamorphic gneiss (epȯ, pȯg) protruding through the valley alluvium. A table listing 

the geologic unit, geologic age, and description of the unit is presented below. A geologic map of Segment 4, Alternative B, showing the geology and the Alignment route is 

shown on Figure 10. 

Table 8 – Geologic Units Segment 4, Alternative B 

Geologic Unit (Symbol[s]) Geologic Age Description

Younger Alluvial Deposits 

(Qal) Holocene

Unconsolidated Valley Alluvial Deposits 

of Silt, Sand, and Gravel; Alluvial Fan 

Deposits.

Younger Lacustrine Deposits 

(Ql) Holocene

Lake and Playa Sediments, Including 

Clay, Silt, and Fine Sand; Ivanpah Lake 

Bed Sediments. 

Metamorphic Rocks 

(Epɽ, Pɽg) Precambrian 

Undifferentiated Injection Gneiss, Schist, 

Granitic Gneiss, Granite Augen Gneiss 

Complex. 

3.3.8. Segment 5, Alternatives A and B (State Line to Sloan, Nevada) 

Alternatives A and B of Segment 5 are in close proximity to each other, on the median 

and east or west sides of I-15, respectively, and they have been evaluated as one alignment for purposes of describing general geologic conditions along that segment. 

Segment 5 begins just south of the California/Nevada state line in the Ivanpah Valley 

and travels north/northeast along the I-15 corridor through the Ivanpah Valley. The 

segment crosses the trace of the potentially active Stateline fault, mapped on the California side, and parallel to the state line. North of Primm, Nevada, this segment passes 

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along the west side of Roach Dry Lake. At the north end of the Ivanpah Valley north of 

Jean, the Alignment passes through the Jean Hills between the Bird Spring and McCullough Ranges and enters the south end of the Las Vegas Valley at the end of Segment 5 

near the community of Sloan, Nevada. 

Geologic maps indicate that the portion of Segment 5 in the Ivanpah Valley between the 

state line and Jean Hills is underlain by younger alluvial deposits that are present in the 

valley. The alluvial deposits include younger Holocene wash sediments and alluvial fan 

deposits (Qa, Qal, Qay, Qay2, Qay3) and older early-Holocene to late-Pleistocene alluvial fan deposits (Qay1). Playa fringe deposits (Qpf) are mapped along the west side of 

Roach Lake in close proximity to the Alignment. Some areas of fill soil and other disturbed areas (Qx) are mapped along this segment of the Alignment, specifically at the 

highway onramp/off-ramp areas. An outcrop of Paleozoic-age dolomite (Dȯg, MzPzs) 

is mapped on the west side of the Alignment between Primm and Jean. 

In the Jean Hills and northeast of the Jean Hills along Segment 5, the geologic maps 

show that the Alignment is underlain by younger alluvium, older alluvium and rock 

formations. Younger Holocene alluvial sediments comprised of wash and alluvial fan 

deposits underlie portions of this area (Qa, Qal, Qay, Qay2, Qay3), and some areas are 

underlain by older, Pleistocene age alluvial fan deposits (Qay1, Qai). These older sediments are described on the geologic maps as moderately to strongly consolidated. 

Ancient Pleistocene to late-Miocene age alluvium (Qao, QTa) comprised primarily of 

gravel is also mapped in portions of this area. Rock formations that underlie this portion 

of Segment 5 include Tertiary age sedimentary rocks (Tao) comprised of fluvial gravel 

with minor sandstone and mudstone, Tertiary age volcanic rocks ranging in composition 

from basalt to rhyolite (Tv, Tsf), and a Paleozoic to Mesozoic era formation (Pbs, 

PPMb, MzPzs) of limestone and dolomite with interbedded shale, sandstone, and conglomerate. 

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A table listing the geologic unit, geologic age, and description of the unit is presented 

below. A geologic map of Segment 5, Alternatives A and B, showing the geology and 

the Alignment routes is shown on Figure 11. 

Table 9 – Geologic Units Segment 5, Alternatives A and B 

Geologic Unit (Symbol[s]) Geologic Age Description

Disturbed And Modified 

Areas (Qx) Holocene

Areas of Anthropogenic Disturbance, 

Artificial Fill, Commercial Development

Areas, and the I-15 Corridor. 

Undivided Young Alluvial 

Deposits (Qa, Qal, Qay) Holocene Undivided Alluvial Fan and Wash Deposits of Gravel, Sand, and Minor Silt. 

Playa Fringe Deposits (Qpf) Holocene Deposits Of Silt, Sand, and Gravel Along

The Perimeter Of Playa Surfaces. 

Youngest Active Alluvium 

(Qay3) Late-Holocene Active Wash and Alluvial Fan Deposits of Gravel, Sand, and Minor Silt. 

Young Active Alluvium 

(Qay2) Holocene

Alluvial Fan and Wash Deposits of 

Gravel, Sand, and Minor Silt of 

Intermittently Active Alluvial Surfaces. 

Oldest Young Alluvium 

(Qay1) Early-Holocene 

Alluvial Fan and Wash Deposits of 

Gravel, Sand, and Minor Silt of 

Inactive Alluvial Surfaces. 

Intermediate Alluvium (Qai) Pleistocene

Deposits Of Relict, Inactive Alluvial 

Fans,

Moderately To Strongly Consolidated. 

Older Alluvial Deposits 

(Qao, Qta) 

Pleistocene To 

Late-Miocene

Dissected Alluvial Fan Deposits, 

Primarily Gravel With Some Sand 

and Silt. 

Sedimentary Rocks (Tao) Tertiary Fluvial Gravel Beds With Minor 

Sandstone and Mudstone. 

Volcanic Rocks (Tv, Tsf) Tertiary Volcanic Rocks Ranging In Composition

From Basalt To Rhyolite. 

Marine Sedimentary And 

Metasedimentary Rocks 

(Pbs, Ppmb, Mzpzs) 

Mesozoic To 

Paleozoic

(Carboniferous)

Dolomite and Limestone with 

Interbedded Shale, Sandstone, and 

Conglomerate; Bird Spring Formation. 

Marine Sedimentary And 

Metasedimentary Rocks 

(Dɽg, Mzpzs) 

Paleozoic – 

Cambrian And 

Devonian

Dolomite and Limestone with 

Interbedded Shale, Sandstone, and 

Conglomerate; Goodsprings Dolomite 

and Carbonate Rocks Of Hewett, 1956. 

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3.3.9. Segment 6, Alternatives A and B (Sloan to Las Vegas, Nevada) 

Alternatives A and B of Segment 6 are in close proximity to each other, on the median 

and west side of I-15, respectively, and they have been evaluated as one alignment for 

purposes of describing general geologic conditions along this segment. Alternatives A 

and B of Segment 6 begin near the community of Sloan, Nevada, at the south end of the 

Las Vegas Valley and travel north along the I-15 corridor across the valley into the City 

of Las Vegas. 

Geologic maps indicate that a limestone formation (Mmc, Mm) mantled by younger alluvium underlies the southern end of Segment 6 at the south end of the Las Vegas 

Valley. The majority of Segment 6 in the Las Vegas Valley is underlain by alluvial deposits that are present in the valley. The alluvial deposits include younger Holocene 

wash sediments and alluvial fan deposits (Qa, Qal, Qs), older Holocene/Pleistocene alluvial fan deposits (Qai, Qoa) that are typically moderately to well consolidated to 

cemented in places, and older Pliocene consolidated sediments (QTs) that are typically 

moderately to well consolidated to strongly cemented. 

A common characteristic of alluvial soils in the Las Vegas Valley and surrounding region is the post-depositional development of calcium carbonate cemented layers. These 

petrocalcic layers are commonly referred to as caliche and consist of alluvial sediments 

that have been cemented by calcium carbonate and can have varying degrees of cementation. The development of caliche is a function of time and older soils tend to have 

more caliche development. The geologic maps indicate that younger Holocene alluvial 

wash and fan deposits (Qa) in this segment may be cemented in places by petrocalcic 

carbonate. Older Pleistocene alluvium (Qoa) may contain a petrocalcic carbonate horizon approximately 6 feet thick near the surface. And older Plio-Pleistocene consolidated 

sediments in this segment are described as having moderately to well consolidated to 

strongly cemented layers of petrocalcic carbonate, and surface exposures are capped in 

places by a resistant petrocalcic crust. 

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A table listing the type of geologic unit, geologic age, and description of the unit is presented below. A geologic map of Segment 6, Alternatives A and B, showing the geology 

and the Alignment routes is shown on Figure 11. 

Table 10 – Geologic Units Segment 6, Alternatives A and B

Geologic Unit (Symbol[s]) Geologic Age Description

Younger Alluvial Deposits 

(Qa, Qal, Qs) Holocene 

Active Wash, Alluvial Fan and Sheet 

Wash Deposits of Gravel, Sand, and 

Minor Silt; Unconsolidated to Locally 

Calcic-Cemented. 

Intermediate Alluvial Deposits 

(Qai)

Holocene- Pleistocene

Deposits of Sand and Gravel on Relict, 

Inactive Alluvial Fans; Slightly to 

Moderately Consolidated. 

Older Alluvial Deposits (Qoa) Pleistocene

Pebble and Small Cobble Gravel with 

Pebbly Sand; Moderately to Well 

Consolidated to Locally Cemented; 

Caliche Horizon Approximately 6 Feet 

Thick Occurs at or Near Surface. 

Consolidated Sediments (Qts) Pliocene To 

Pleistocene

Fine Sand Interbedded With Silt, Pebbly 

Sand, and Gravel; Moderately to Well 

Consolidated to Strongly Cemented. 

Common Caliche Layers and Resistant 

Caliche Surface Crust. 

Marine Sedimentary And 

Meta-Sedimentary Rocks 

(Mmc, Mm) 

Mesozoic To 

Paleozoic 

(Carboniferous) 

Monte Cristo Limestone (Mm). 

3.3.10. Segment 6, Alternatives C and D (Sloan to Las Vegas, Nevada) 

Alternatives C and D of Segment 6 are in close proximity to each other following the 

alignment of a UPRR rail line, and they have been evaluated as one alignment for purposes of describing general geologic conditions along this segment. Alternatives C 

and D of Segment 6 begin along I-15 near the community of Sloan, Nevada, at the south 

end of the Las Vegas Valley and diverge northwest from the I-15 corridor utilizing an 

existing UPRR rail line alignment for travel across the Las Vegas Valley and into the 

city of Las Vegas. 

At the beginning of Alternatives C and D, at the southern end of the Las Vegas Valley, 

geologic maps indicate that formations of limestone with interbedded shale, sandstone, 

and conglomerate (Ds, Pbs, PPMb) underlie the Alignment in a hilly area west of I-15. 

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This rock formation is mantled by younger alluvium (Qal). After passing though this 

hilly area, the Alignment turns toward the northeast and descends into the Las Vegas 

Valley. The majority of Alternatives C and D in the Las Vegas Valley are underlain by 

alluvial deposits. 

The alluvial deposits include younger Holocene wash sediments and alluvial fan deposits (Qa, Qal, Qs), older Holocene/Pleistocene alluvial fan deposits (Qai, Qoa) that are 

typically moderately to well consolidated to cemented in places, older Pleistocene 

gravel deposits (Qog) that are consolidated to strongly cemented, and older Pliocene 

consolidated sediments (QTs) that are typically moderately to well consolidated to 

strongly cemented. 

The geologic maps indicate that younger alluvial wash and fan deposits (Qa) in this 

segment may be cemented in places by petrocalcic carbonate. Older alluvium (Qoa) 

may contain a petrocalcic carbonate horizon approximately 6 feet thick near the surface. 

Older gravel deposits (Qog) are described as being capped by a petrocalcic horizon 

greater than approximately 10 feet thick. Older Plio-Pleistocene consolidated sediments 

(QTs) in this segment are described as having moderately to well consolidated to 

strongly cemented layers of petrocalcic carbonate, and surface exposures are capped in 

places by a resistant petrocalcic crust. 

A table listing the type of geologic unit, geologic age, and description of the unit is presented below. A geologic map of Segment 6, Alternatives C and D showing the geology 

and the Alignment routes is shown on Figure 11. 

Table 11 – Geologic Units Segment 6, Alternatives C and D

Geologic Unit (Symbol[s]) Geologic Age Description 

Younger Alluvial Deposits 

(Qa, Qal, Qs) Late-Holocene 

Active Wash, Alluvial Fan and Sheet 

Wash Deposits Of Gravel, Sand, and 

Minor Silt; Unconsolidated to Locally 

Calcic-Cemented.

Intermediate Alluvial Deposits Pleistocene Deposits Of Sand and Gravel on Relict,

Inactive Alluvial Fans; Slightly to 

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Table 11 – Geologic Units Segment 6, Alternatives C and D

Geologic Unit (Symbol[s]) Geologic Age Description 

(Qai) Moderately Consolidated.

Older Alluvial Deposits (Qoa) Pleistocene

Pebble and Small Cobble Gravel with 

Pebbly Sand; Moderately to Well 

Consolidated to Locally Cemented; 

Caliche Horizon Approximately 6 Feet 

Thick Occurs at or Near Surface. 

Older Alluvial (Gravel) Deposits

(Qog)

Pleistocene

Alluvial Fan Clast-Supported Gravel 

Deposits; Consolidated to Strongly 

Cemented; Capped by a MatrixSupported Caliche Horizon Greater 

than Approximately 10 Feet Thick. 

Consolidated Sediments (Qts) Pliocene To 

Pleistocene

Fine Sand Interbedded with Silt, Pebbly

Sand, and Gravel; Moderately to Well 

Consolidated to Strongly Cemented. 

Common Caliche Layers and Resistant 

Caliche Surface Crust. 

Marine Sedimentary And 

Metasedimentary Rocks 

(Pbs, Ppmb) 

Mesozoic To 

Paleozoic

(Carboniferous)

Dolomite and Limestone with 

Interbedded Shale, Sandstone and 

Conglomerate; Bird Spring Formation. 

Marine Sedimentary And 

Metasedimentary Rocks (Ds) 

Paleozoic -

Devonian Sultan Limestone (Hewett, 1956). 

3.3.11. Segment 7, Alternatives A and B (City of Las Vegas, Nevada) 

Alternatives A and B of Segment 7 are in close proximity to each other, on the median 

and west side of I-15, respectively, and they have been evaluated as one alignment for 

purposes of describing general geologic conditions along this segment. Alternatives A 

and B of Segment 7 begin in the City of Las Vegas and travel north along the I-15 corridor across the Las Vegas Valley. This last segment of the Alignment ends at a planned 

new station in Las Vegas. 

Geologic maps indicate that Segment 7 in the Las Vegas Valley is underlain by alluvial 

deposits. The alluvial deposits include younger Holocene wash sediments and alluvial 

fan deposits (Qa, Qal, Qs), older Holocene/Pleistocene alluvial fan deposits (Qai, Qoa) 

that are typically moderately to well consolidated to cemented in places, and older Plio206725001 R Prelim Geo.doc F-J-39 32
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cene consolidated sediments (QTs) that are typically moderately to well consolidated to 

strongly cemented. 

A common characteristic of alluvial soils in the Las Vegas Valley and surrounding region is the post-depositional development of calcium carbonate cemented layers. These 

petrocalcic layers are commonly referred to as caliche and consist of alluvial sediments 

that have been cemented by calcium carbonate and can have varying degrees of cementation. The development of caliche is a function of time and older soils tend to have 

more caliche development. The geologic maps indicate that younger Holocene alluvial 

wash and fan deposits (Qa) in this segment may be cemented in places by petrocalcic 

carbonate. Older Pleistocene alluvium (Qoa) may contain a petrocalcic carbonate horizon approximately 6 feet thick near the surface. And older Plio-Pleistocene consolidated 

sediments in this segment are described as having moderately to well consolidated to 

strongly cemented layers of petrocalcic carbonate, and surface exposures are capped in 

places by a resistant petrocalcic crust. 

A table listing the type of geologic unit, geologic age, and description of the unit is presented below. A geologic map of Segment 7, Alternatives A and B, showing the geology 

and the Alignment routes is shown on Figure 11. 

Table 12 – Geologic Units Segment 7, Alternatives A and B

Geologic unit (symbol[s]) Geologic age Description 

Younger Alluvial Deposits 

(Qa, Qal, Qs) Holocene

Active Wash, Alluvial Fan and Sheet 

Wash Deposits of Gravel, Sand, And 

Minor Silt; Unconsolidated to Locally 

Calcic-Cemented.

Intermediate Alluvial Deposits

(Qai)

HolocenePleistocene

Deposits of Sand and Gravel on Relict, 

Inactive Alluvial Fans; Slightly to 

Moderately Consolidated. 

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Table 12 – Geologic Units Segment 7, Alternatives A and B

Geologic unit (symbol[s]) Geologic age Description 

Older Alluvial Deposits (Qoa) Pleistocene

Pebble and Small Cobble Gravel with 

Pebbly Sand; Moderately to Well 

Consolidated to Locally Cemented; 

Caliche Horizon Approximately 6 Feet 

Thick Occurs at or Near Surface. 

Consolidated Sediments (Qts) Pliocene To 

Pleistocene

Fine Sand Interbedded with Silt, Pebbly 

Sand, and Gravel; Moderately to Well 

Consolidated to Strongly Cemented. 

Common Caliche Layers And Resistant 

Caliche Surface Crust. 

3.3.12. Segment 7, Alternative C (City of Las Vegas, Nevada) 

Alternative C of Segment 7 follows the alignment of an existing UPRR rail line, beginning at about the intersection of Tropicana Avenue, and travels across the Las Vegas 

Valley. This last segment of the Alignment ends at a planned new station in the City of 

Las Vegas. 

Geologic maps indicate that Segment 7 in the Las Vegas Valley is underlain by alluvial 

deposits. The alluvial deposits include younger Holocene wash sediments and alluvial 

fan deposits (Qa, Qal, Qs), older Holocene/Pleistocene alluvial fan deposits (Qai, Qoa) 

that are typically moderately to well consolidated to cemented in places, older Pleistocene gravel deposits (Qog) that are consolidated to strongly cemented, and older 

Pliocene consolidated sediments (QTs) that are typically moderately to well consolidated to strongly cemented. 

The geologic maps indicate that younger alluvial wash and fan deposits (Qa) in this 

segment may be cemented in places by petrocalcic carbonate. Older alluvium (Qoa) 

may contain a petrocalcic carbonate horizon approximately 6 feet thick near the surface. 

Older gravel deposits (Qog) are described as being capped by a petrocalcic horizon 

greater than approximately 10 feet thick. Older Plio-Pleistocene consolidated sediments 

(QTs) in this segment are described as having moderately to well consolidated to 

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strongly cemented layers of petrocalcic carbonate, and surface exposures are capped in 

places by a resistant petrocalcic crust. 

A table listing the type of geologic unit, geologic age, and description of the unit is presented below. A geologic map of Segment 7, Alternative C showing the geology and the 

Alignment route is shown on Figure 11. 

Table 13 – Geologic Units Segment 7, Alternative C

Geologic Unit (Symbol[s]) Geologic Age Description 

Younger Alluvial Deposits 

(Qa, Qal, Qs) Late-Holocene 

Active Wash, Alluvial Fan and Sheet 

Wash Deposits of Gravel, Sand, And 

Minor Silt; Unconsolidated to Locally 

Calcic-Cemented.

Intermediate Alluvial Deposits 

(Qai) Pleistocene

Deposits of Sand and Gravel on Relict, 

Inactive Alluvial Fans; Slightly to 

Moderately Consolidated. 

Older Alluvial Deposits (Qoa) Pleistocene

Pebble and Small Cobble Gravel with 

Pebbly Sand; Moderately to Well 

Consolidated to Locally Cemented; 

Caliche Horizon Approximately 6 Feet 

Thick Occurs at or Near Surface. 

Older Alluvial (Gravel) Deposits

(Qog)

Pleistocene

Alluvial Fan Clast-Supported Gravel 

Deposits; Consolidated to Strongly 

Cemented; Capped by a MatrixSupported Caliche Horizon Greater 

than Approximately 10 Feet Thick. 

Consolidated Sediments (Qts) Pliocene To 

Pleistocene

Fine Sand Interbedded with Silt, Pebbly

Sand, and Gravel; Moderately to Well 

Consolidated to Strongly Cemented. 

Common Caliche Layers and Resistant 

Caliche Surface Crust. 

3.3.13. Groundwater and Surface Water 

Groundwater information along the Alignment is limited, and preliminary information 

regarding the depth to groundwater at selected locations was obtained from published 

geologic maps, the County of San Bernardino and Caltrans LOTB sheets. Based on varied topographic and geologic conditions along the Alignment, groundwater depths are 

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anticipated to be variable along different segments of the Alignment. Shallow groundwater conditions may be anticipated beneath the Mojave River and beneath active 

washes and streams along the Alignment. The depths to groundwater may be influenced 

by seasonal variations, precipitation, irrigation, soil/rock types, groundwater pumping, 

and other factors and are subject to fluctuations. Shallow perched conditions may be 

present in places. Further study, including site exploration, should be performed to 

evaluate the presence of groundwater, seepage, and/or perched groundwater, and the potential impacts on design and construction of project improvements. 

The County of San Bernardino has indicated some areas within the Alignment study 

area with potential for shallow groundwater. These areas include: 

x Areas along the Mojave River (Segments 1A, 2A, 2B, 3A and 3B); 

x Areas adjacent to some faults that form groundwater barriers (which can cause 

groundwater to rise), such as areas southwest of the Calico fault near Barstow 

(Segments 2A and 2B) and southwest of the Lockhart fault west of Barstow; 

x The Mojave River Wash area south of the intersection of I-15 and Basin Road 

(Segments 3A and 3B); and 

x The area between Baker and north toward Silver Lake (north of Segments 3A and 

3B).

Groundwater contour maps of the Las Vegas Valley from 1979 groundwater data were 

reviewed as part of our study; the map coverage begins in the southern part of the valley 

and includes the north portions of Segment 6 and Segment 7. The maps indicate that 

groundwater in the southern part of the valley underlying Segment 6 is deeper than 

100 feet below the surface. The maps indicate that groundwater becomes shallower toward the northeast. Along Alternatives A and B of Segment 6 (along I-15), the 

groundwater reaches a depth of 100 feet below the surface near the intersection with 

Russell Road. Along Alternatives C and D of Segment 6 (following the UPRR alignment), the groundwater reaches a depth of 100 feet below the surface near the 

intersection with Tropicana Avenue. North of these locations, the maps show that 

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groundwater becomes shallower toward the northeast and is approximately 20 bgs along 

Segment 7 and at the planned station locations at the north end of the Alignment. 

Caltrans LOTB sheets from investigations for I-15 crossing structures contain information on groundwater encountered in borings along the Alignment. A table listing the 

crossing structure location, ground surface elevation, and depth to groundwater in selected borings at that location is presented below. 

Table 14 – Depth To Groundwater In Caltrans Borings For I-15 Construction 

Alignment 

Segment 

and Alternative 

(Geographic Location) 

Caltrans 

Crossing

Structure 

Location 

Boring 

Number

(Date) 

Ground 

Surface

Elevation 

(Feet) 

Depth

To

Groundwater

(Feet) 

2a (Barstow) Hiker Ditch 

Bridge 

B-1 

(October 12, 1994) 1,996 50

3a And B (Soda 

Mountains) 

Marl Ditch 

Bridge 

B-2 

(February 2, 1957) 1,451 11

3a And B (Soda 

Mountains) 

Turtle Ditch 

Bridge 

B-1 

(February 1, 1957) 1,328 21

3a And B (Soda 

Mountains) 

Banner Ditch 

Bridge 

B-1 

(January 31, 1957) 1,111 10

3a And B (Soda Lake) Sheep Ditch 

Bridge 

B-1 

(January 31, 1957) 1,067 3

3a And B (Soda Lake) Mobi Ditch 

Bridge 

B-1 

(October 22, 1956) 920 6

3a And B (Soda Lake) West Baker 

Overcrossing 

Various 

(March 25, 1959) 

921 

(Average) 26

3a And B (Baker) Mojave River 

(Baker) Bridge 

Various 

(March 1959) 

921 

(Average) 23 To 24 

3a And B (Baker) Baker Inn Ditch B-1 

(August 20, 1959) 944 30

3a And B (Halloran 

Springs) Halloran Wash Bridge B-5 (October 27, 1956) 2,506 19

3a And B (Valley Wells) Hot Wash Bridge B-1 

(October 26, 1956) 3,711 13

3a And B (Valley Wells) West Valley Wells 

Ditch Bridge 

Various 

(January/February

1999) 

3,700 

(Average) 55 To 74 

3a And B (Valley Wells) Valley Wells Ditch 

Bridge 

Various 

(February/March 

3,682 

(Average) 31 To 75 

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Table 14 – Depth To Groundwater In Caltrans Borings For I-15 Construction 

Alignment 

Segment 

and Alternative 

(Geographic Location) 

Caltrans 

Crossing

Structure 

Location 

Boring 

Number

(Date) 

Ground 

Surface

Elevation 

(Feet) 

Depth

To

Groundwater

(Feet) 

1999) 

3a And B (Valley Wells) Windmill Station 

Ditch Bridge 

Various 

(January 1999) 

3,697 

(Average) 63 To 72 

3a And B (Valley Wells) Wells Ditch Bridge 

Various 

(February/March 

1999) 

3,697 

(Average) 26 To 34 

Surface flow within streams and washes along the Alignment is ephemeral and typically 

limited to during or shortly after intense periods of rain. Some of the dry stream beds 

are susceptible to flash flooding. During periods of heavy rain, water may pool in dry 

lake beds and in scattered areas in the alluvial flood plains and washes. 

3.4. Regional Active and Potentially Active Faults 

The Alignment is situated within a seismically active region of southern California and Nevada, and numerous active and potentially active faults have been mapped within or adjacent 

to the study area. As defined by the California Geological Survey (CGS), an active fault is 

one that has had surface displacement within Holocene time (roughly the last 11,000 years). 

Potentially active faults are those which show evidence of surface displacement during Quaternary time (roughly the last 1.6 million years) but for which evidence of Holocene 

movement has not been established. 

An inactive fault is one that has not shown evidence of surface displacement during Quaternary time (roughly the last 1.6 million years.) Faults generally develop due to tectonic forces 

resulting in stresses and strains to earth materials. Over geologic time, the seismic environment of a geomorphic region can change due to regional tectonic changes, consequently 

changing the dynamics of tectonic forces on the rocks. Inactive faults are remnants of former 

tectonic activity in the rock formation and are present in formations within the Alignment in 

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areas that are not considered to be seismically active. There are numerous inactive fault 

traces that have been mapped crossing the alternative routes within the Alignment. Since 

these types of faults are not considered to have potential for rupture, they are not discussed 

in the seismic section of this report, but are discussed in the site geology sections of this report as appropriate. 

The approximate locations of the principal faults in the region and their geographic relationship to the Alignment are shown on the Regional California Fault Map, Figure 12. 

Information regarding faults in Nevada is more limited than California. Figure 13 shows 

faults and earth fissures that have been mapped in the Las Vegas Valley. Table 15 lists 

nearby principal faults, the maximum moment magnitude (Mmax), the fault type, the slip rate, 

the fault source type, and significant historic earthquakes that have occurred on the faults. 

The following subsections discuss the principal fault zones within the Alignment region that 

have had a dominant role in forming the present seismic environment. 

Table 15 – Principal Regional Active and Potentially Active Faults 

Fault

Maximum

Moment

Magnitude

(Mmax ) 1

Fault

Type1

Slip Rate

(mm/yr) 1

Source

Type1

Historic

Earthquakes2

Blackwater 7.1 SS 0.6 B -

Burnt Mountain 6.5 SS 0.6 B M7.3 Landers, 6/28/92 

Calico-Hidalgo 7.3 SS 0.6 B M5.3 Calico, 4/18/97 

Camp Rock 7.5 SS 1.0 - M7.3 Landers, 6/28/92 

Clamshell – Sawpit 6.5 R 0.5 B M5.8 Sierra Madre, 

6/28/91 

Cleghorn 6.5 SS 3.0 B -

Cucamonga 6.9 R 5.0 B -

Death Valley (South) 7.1 SS 4.0 - -

Elsinore (Chino-Central Avenue) 6.7 SS 1.0 B -

Elsinore (Glen Ivy) 6.8 SS 5.0 A M6, 5/15/1910 

Eureka Peak 6.4 SS 0.6 B M7.3 Landers, 6/28/92 

Garlock (East) 7.5 SS 7.0 B -

Garlock (West) 7.3 SS 6.0 B -

Gravel Hills–Harper Lake 7.1 SS 0.6 B -

Helendale-South Lockhart 7.3 SS 0.6 B -

Homestead Valley 7.0 SS 0.5 - M7.3 Landers, 6/28/92 

Johnson Valley (Northern) 6.7 SS 0.6 B M7.3 Landers, 6/28/92 

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Table 15 – Principal Regional Active and Potentially Active Faults 

Fault

Maximum

Moment

Magnitude

(Mmax ) 1

Fault

Type1

Slip Rate

(mm/yr) 1

Source

Type1

Historic

Earthquakes2

Kickapoo (Landers) 7.3 SS 0.6 B -

Lavic Lake 6.8 SS 0.8 - M7.1 Hector Mine, 

10/16/99 

Lenwood-Lockhart-Old Woman 

Springs 7.5 SS 0.6 B -

Little Lake 6.9 SS 0.7 B -

Lockhart 7.5 SS 0.8 - -

Manix 7.0 SS 0.1 - M6.5 Manix, 4/10/47 

Mt. General N/A SS N/A - -

North Frontal Fault Zone (West) 7.2 R 1.0 B -

North Frontal Fault Zone (East) 6.7 R 0.5 B -

Owl Lake 6.5 SS 2.0 B -

Panamint Valley 7.4 N 2.5 B -

Pinto Mountain 7.2 SS 2.5 B -

Pisgah-Bullion Mt.-Mesquite Lake 7.3 SS 0.6 B -

Puente Hills Blind Thrust 7.1 R 0.7 -

Raymond 6.5 RO 1.5 B -

San Andreas (Mojave) 7.4 SS 30 A M8 Fort Tejon, 1/9/1857

San Andreas (San Bernardino) 7.5 SS 24 A -

San Andreas (Coachella) 7.2 SS 25 A -

San Andreas (Cholame) 7.3 SS 34 A -

San Gabriel 7.2 SS 1.0 B -

San Jacinto (San Bernardino) 6.7 SS 12 A M6.3 Loma Linda, 

7/22/1923 

San Jacinto (San Jacinto Valley) 6.9 SS 12 A M6.8 San Jacinto, 

4/21/1918 

San Jacinto (Anza) 7.2 SS 12 A -

San Jose 6.4 RO 0.5 B M4.7 Upland, 6/28/88

M5.4 Upland, 2/28/90 

Sierra Madre 7.2 R 2.0 B -

South Emerson-Copper Mountain 7.0 SS 0.6 B M7.3 Landers, 6/28/92 

Tank Canyon 6.4 N 1.0 B -

Upper Elysian Park Blind Thrust 6.4 R 1.3 B -

Verdugo 6.9 R 0.5 B -

Whittier (Elsinore Fault Zone) 6.8 RO 2.5 A M5, 5/15/1910 

Notes:

DS – Dip Slip 

N-T – Normal-Thrust 

R – Reverse 

RO – Reverse-Oblique 

SS – Strike Slip 

References: 1

Blake, T.F., 2001b. 

2

SCEC, 2007; Co. of San Bernardino, 2005d 

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3.4.1. San Andreas Fault Zone 

The San Andreas fault zone has long been recognized as the dominant seismotectonic 

feature in California. Two of California’s three largest historic earthquakes, the 1906 

San Francisco earthquake and the 1857 Forth Tejon earthquake, occurred along the 

San Andreas fault. The fault is a right lateral strike-slip fault which is capable of producing earthquakes in excess of Mmax 7.5. It is inferred that the segment of the 

San Andreas Fault zone closest to the site is currently locked and accumulating substantial amounts of strain in response to the stresses generated by the relative movement 

between the Pacific and North American plates. The available geologic and seismicity 

data indicate that this strain is released during infrequent major earthquakes (Mmax 7 to 

8+ events) rather than by more frequent smaller magnitude earthquakes. The 

San Andreas Fault is located approximately 21.3 miles southwest of the southwest end 

of the Alignment. 

3.4.2. Garlock Fault 

The Garlock fault is a prominent fault in southern California and crosses the northern 

part of the Mojave Desert province. The east end of the fault is approximately 20 miles 

north-northwest of Segment 3. Although this fault has not produced large earthquakes 

historically, geomorphic and stratigraphic evidence indicates that it has done so in the 

past. A total of about 30 to 40 miles of left-lateral strike slip has been documented 

across this fault. The Garlock fault is considered capable of generating about a Mmax 7.5 

earthquake. 

3.4.3. Eastern California/Mojave Shear Zone

The Eastern California/Mojave Shear Zone (ECMSZ) is an approximate 50-mile-wide 

zone of tectonic deformation that crosses the central Mojave Desert and is characterized 

by northwest trending, right lateral, strike-slip faults roughly centered around Barstow. 

The ECMSZ is estimated to accommodate between 9 and 23 percent of the relative motion between the Pacific and North American tectonic plates (Southern California 

Earthquake Data Center [SCEC], 2007). The ECMSZ crosses the Alignment between 

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about Helendale and Manix, California. The ECMSZ is comprised of several northwest 

trending, right lateral, strike-slip faults that include the Blackwater, Bullion, Calico, 

Emerson, Helendale, Landers, Lockhart, Lenwood, Camp Rock, Harper, Harper Lake, 

Homestead Valley, Johnson Valley, Kickapoo (Landers), Lavic Lake, Mesquite Lake, 

and West Calico faults. 

Several moderate to large earthquakes have ruptured faults within this region, including 

the Mmax 7.3 Landers earthquake of June 28, 1992, and the Mmax 7.1 Hector Mine earthquake of October 16, 1999. The Landers earthquake produced an approximate 53-milelong surface rupture that averaged approximately 10 to 13 feet of slip and occurred 

along portions of the Johnson Valley, Landers, Homestead Valley, Emerson, and Camp 

Rock faults (County of San Bernardino, 2005d). These surface rupture areas occurred 

south of the Alignment study area. 

On March 18, 1997, a Mmax 5.3 earthquake occurred along the Calico fault approximately 12 miles east-northeast of Barstow. This earthquake was the last aftershock of 

the Landers earthquake of 1992 to reach Mmax 5. Although there was no surface rupture 

attributed to this earthquake, the Calico fault had exhibited some triggered slip during 

the 1992 Landers event (County of San Bernardino, 2005d). 

3.5. Active and Potentially Active Faults Crossing Segments of the Alignment 

Five active faults are mapped crossing the alternative routes of the Alignment. With the exception of the northeast trending Manix fault, these active faults are associated with the 

ECMSZ and comprise northwest trending strike-slip faults that cross alternative segments of 

the Alignment. Five potentially active faults are mapped crossing the alternative routes of 

the Alignment. Two of these potentially active faults are associated with the ECMSZ, while 

the other three faults are located northeast of, and are not associated with the ECMSZ. The 

approximate locations of these faults and their geographic relationship to the Alignment are 

shown on the Figure 12. 

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Three active faults that cross the Alignment, the Helendale-South Lockhart fault, the 

Mt. General fault, and the Calico-Hidalgo fault, have been designated by the State of California as Earthquake Fault Zones under the Alquist-Priolo Special Studies Zone Act of 1972 

(Hart, E.W., and Bryant, W.A., 1997). Development within Earthquake Fault Zones will 

need further evaluation to address the potential for fault rupture. The location of the boundaries of the Earthquake Fault Zone is based on the presence of well-defined, active fault 

traces. Zone boundaries are typically 500 to 660 feet away from the fault traces and are positioned to accommodate imprecise locations of the faults and the possible existence of active 

branches. Table 16 lists information about the active and potentially active faults crossing 

the Alignment including: the recency of activity; the Alignment segment(s) affected by the 

faults; the Mmax; the fault type; the slip rate; the degree of exposure of the fault; the proximity to a State Earthquake Fault Zone; and significant historic earthquakes that have 

occurred on these faults. 

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Table 16 – Active and Potentially Active Faults Crossing Segments of the Alignment 

Fault Activity (Recency) 1

Affected 

Segment 

Crossing 

the Fault 

Maximum

Moment

Magnitude

(Mmax ) 2

Fault

Type2

Slip

Rate 

(mm/yr) 2

Mapped

Fault

Exposure

Segment 

Crosses

Earthquake 

Fault Zone 

Historic

Earthquakes* 

Helendale-South Lockhart Potentially Active (late-Quaternary) 1A 7.3 SS 0.6 Concealed by alluvium No** NDHelendale-South Lockhart Active (Holocene) 1B 7.3 SS 0.6 Surface Yes NDLenwood-Lockhart-Old Woman Springs 

Active 

(Historic)

2A 7.5 SS 0.6 Surface/ concealed No** ND

Mt. General Active (Holocene) 2A ND SS ND Surface Yes NDGravel Hills–Harper Lake Potentially Active (late-Quaternary) 2A 7.1 SS 0.6 Concealed by alluvium No** NDCalico-Hidalgo Active (Holocene) 3A & B 7.3 SS 0.6 Concealed by alluvium Yes M 5.3 Calico, 4/18/97 Manix Active (Holocene) 3A & B 7.0 SS 0.1 Surface/ concealed No** M 6.5 Manix, 4/10/47 Unnamed (Cronese Valley) Potentially Active (early-Quaternary) 3A & B ND SS ND Concealed by alluvium No NDBaker Potentially Active (early-Quaternary) 3A & B ND SS3 ND Surface/ concealed No NDStateline Potentially Active (early-Quaternary) 5A & B ND SS ND Concealed by alluvium No NDmm/yr – millimeters per year SS – Strike Slip ND – No data available *County of San Bernardino General Plan, 2005 **Other portions of fault not underlying segment mapped as State of California Earthquake Fault Zone 1Jennings, C.W., 1994. 2Blake, T.F., 2001b. 3 probable interpretation (SCEC, 2007). 

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3.5.1. Helendale-South Lockhart Fault (active and potentially active portions) 

The active Helendale fault is a right-lateral, strike-slip fault about 56 miles in length and 

may form a roughly continuous fault system with the active South Lockhart fault located northwest of the study area (County of San Bernardino, 2005d). These faults 

could rupture together during an earthquake and are considered capable of producing a 

Mmax 7.3 earthquake. Alternative segments of the Alignment cross a portion of the 

Helendale-South Lockhart fault that is mapped as active, and cross a portion of the fault 

mapped as potentially active (Figure 12). 

3.5.2. Lenwood-Lockhart-Old Woman Springs Fault 

The active Lenwood and Lockhart faults are prominent right-lateral, strike-slip faults 

that may form a continuous system crossing the Alignment study area in the community 

of Lenwood southwest of Barstow (County of San Bernardino, 2005d). The Lenwood 

fault extends for a length of about 47 miles and is reported to have experienced some 

triggered slip, or creep, in the community of Lenwood in 1992 due to the Landers 

earthquake (County of San Bernardino, 2005d). The Lockhart fault extends for a length 

of about 44 miles northwest of the communities of Lenwood and Barstow. These faults 

are considered capable of producing a Mmax 7.5 earthquake. 

3.5.3. Mt. General Fault 

The active Mt. General fault is a right-lateral, strike-slip fault approximately 13 miles in 

length and is considered to have ruptured in the Holocene period along the middle section of the fault (SCEC, 2007). This fault is designated by the state as an Earthquake 

Fault Zone. 

3.5.4. Gravel Hills-Harper Lake Fault 

The potentially active Gravel Hills-Harper Lake fault is a fragmented fault with a total 

length of approximately 43 miles. The slip rate of this right-lateral, strike-slip fault is 

estimated to be approximately 0.6 mm/yr, and the fault is considered capable of produc206725001 R Prelim Geo.doc F-J-52 45
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ing a Mmax 7.1 earthquake. Active portions of the Gravel Hills-Harper Lake fault are located to the northwest of the Alignment study area. 

3.5.5. Calico-Hidalgo Fault 

The active Calico-Hidalgo fault zone, source of the 1997 Calico Earthquake (Mmax 5.3),

is a right-lateral, strike-slip fault approximately 34 miles in length. The slip rate along 

this fault is estimated to be approximately 0.6 millimeters per year (mm/yr) and the 

fault is estimated to be capable of producing a Mmax 7.3 earthquake. The Calico – Hidalgo fault exhibited triggered slip during the 1992 Landers earthquake. This fault zone 

could rupture simultaneously with the West Calico and Hidalgo faults to the south 

(County of San Bernardino, 2005d). 

3.5.6. Manix Fault 

The active Manix fault is a left-lateral, strike slip fault that is located on the southeast 

side of and is sub-parallel to I-15 in the community of Manix between Barstow and 

Baker, California. The fault is roughly broken into thirds, with a total length of about 22 

miles. Fault maps (Jennings, 1994) indicate that the west/southwest end of the Manix 

fault that crosses the Alignment is active. The State of California Earthquake Fault Zone 

for this fault is approximately 41⁄2 miles long and is located on a segment of the fault located approximately 1.3 miles southwest of the Alignment in Manix. On April 10, 1947, 

a Mmax 6.5 earthquake occurred on the Manix fault. The length of the surface rupture 

was about 3 miles, and the maximum slip was about 5 centimeters (County of San Bernardino, 2005d). The rupture was located on the zoned segment of the fault. The Manix 

fault is considered capable of producing a Mmax 7.0 earthquake. 

3.5.7. Unnamed (Cronese Valley) Fault 

A concealed, potentially active fault is mapped in the Cronese Valley (Jennings, 1994), 

as shown on Figure 12. This fault is unnamed, and information about this fault is not 

provided on the available State references reviewed. 

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3.5.8. Baker Fault 

Information regarding the potentially active Baker fault is limited. The information 

about the Baker fault was obtained from the SCEC. According to the SCEC, the fault 

type is uncertain but is probably a right-lateral, strike-slip fault of approximately 

28 miles length. It may have ruptured in late-Quaternary time at its southern end. 

3.5.9. Stateline Fault

The Stateline fault is mapped as a concealed, potentially active fault (Jennings, 1994). 

Information about this fault is limited on the available State references reviewed. 

3.5.10. Faults in Las Vegas Valley 

Faults in the Las Vegas Valley are indicated as active on the geologic maps reviewed, 

but the activity is attributed to subsidence, not tectonic activity. 

There is some controversy among Nevada geologists as to the origin of these faults, 

which are sometimes referred to as “compaction faults,” in the Las Vegas Valley. Differing proposed origins for these faults include: 

x Differential consolidation or compaction over time of the thick alluvial and lakebed 

sediments in the Las Vegas Valley. 

x Tectonic factors associated with faults that may extend into the basement bedrock 

beneath the valley’s sediment. 

x A combination of differential consolidation and tectonic factors. 

A fault map of Segments 6 and 7 showing faults and earth fissures and the Alternative 

routes of these Segments is shown on Figure 13. 

4. ENVIRONMENTAL CONSEQUENCES 

4.1. Regional Effects – Operational Period 

Environmental consequences of the affected environment that pertain to geotechnical issues 

during the operational period of the rail system include potential seismic and geologic haz206725001 R Prelim Geo.doc F-J-54 47
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ards. Seismic and geologic hazards that might potentially affect improvements within the 

Alignment during long-term operations include surface rupture due to faulting, ground shaking, liquefaction, and dam inundation. These potential geologic and seismic hazards 

associated with the operational period of the project are further discussed in the following 

sections. Mitigation measures for these potential seismic and geologic hazards are presented 

in Section 6. 

4.1.1. Surface Fault Rupture 

Surface fault rupture is the offset or rupturing of the ground surface by relative displacement across a fault during an earthquake. Evaluation of the potential hazard of 

surface fault rupture is based on the concepts of recency and recurrence of faulting 

along existing faults. In general, the more recent the faulting the greater the probability 

for future faulting (Allen, 1975). Stated another way, faults of known historic activity 

during the last 200 years, as a class, have a greater probability for future activity than 

faults classified as Holocene age (last 11,000 years) and a much greater probability of 

future activity than faults classified as Quaternary age (last 1.6 million years). However, 

it should be kept in mind that certain faults have recurrent activity measured in tens or 

hundreds of years whereas other faults may be inactive for thousands of years before 

being reactivated. The magnitude, sense, and nature of fault rupture also vary for different faults or even along different strands of the same fault. Even so, future faulting 

generally is expected to recur along pre-existing faults (Bonilla, 1970). The development of a new fault or reactivation of a long-inactive fault is relatively uncommon and 

generally need not be a design consideration in project development. 

The greatest probability for surface fault rupture within the Alignment is along active 

faults (Holocene-age), particularly along active faults designated as Earthquake Fault 

(Alquist-Priolo) Zones. Active faults crossing the Alignment include the HelendaleSouth Lockhart, Lenwood-Lockhart-Old Woman Springs, Mt. General, Calico-Hidalgo, 

and the Manix faults. The approximate location of these faults and their geographic relationship to the Alignment are shown on Figure 12. Faults in the Las Vegas Valley are 

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indicated as active on the geologic maps reviewed, but the activity is attributed to subsidence, and not tectonic activity, and the potential for surface rupture due to an 

earthquake is considered low. 

During an earthquake on one of the active faults crossing the Alignment, potential surface rupture of the fault would manifest in relative displacement of ground across the 

fault surface. Typically, since the active faults crossing the Alignment are strike-slip 

faults, the displacement would be anticipated in a horizontal direction, but some vertical 

component of offset may occur. 

Damage could occur to the proposed rail alignments and associated structures due to 

fault rupture if those elements are constructed across the fault rupture surface. Damages 

may include offset/damage to at-grade rail alignments at portions of the Alignment 

crossing the fault rupture; damage to structural elements of the rail line such as aerial 

guideways or bridges that are placed across the fault rupture; or damage to facilities 

built across the fault rupture. 

4.1.2. Ground Shaking 

Ground shaking is the response of the surface to the passing of earthquake wave fronts 

radiating from the focus of the earthquake. The period of shaking corresponds with the 

passage of the seismic wave through the site. Earthquake events, which could significantly affect the Alignment, would be strong ground shaking following an earthquake 

along one of the regional active or potentially active faults within or near the Alignment. Disregarding local variations in ground conditions, the intensity of shaking at 

different locations within the Alignment can generally be expected to decrease with distance away from an earthquake source. 

Ground shaking could cause detrimental damage to project improvements if the appropriate design for the anticipated level of shaking is not considered. Damages due to 

ground shaking could include misaligned rail lines and other structural elements, and 

cracks in concrete foundations, walls and structures such as bridges and guideways. 

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In order to evaluate the level of ground shaking that might be anticipated within the 

Alignment, the Caltrans method of estimating peak horizontal ground accelerations 

from the region’s principal seismic sources was reviewed. Figure 14 shows the estimated peak horizontal ground accelerations within the limits of the Alignment, based on 

Caltrans California Seismic Hazard Map (Mualchin, L., 1996b). The map indicates that 

the Alignment is located in an area where peak horizontal accelerations ranging from 

0.1g to 0.6g would be considered during design. Peak horizontal ground accelerations 

estimated on Figure 14 are summarized by segment in Table 17 below. 

Table 17 – Estimated Peak Horizontal Ground Accelerations Anticipated Along 

Segments of the Alignment 

Estimated Peak Horizontal Ground 

Accelerations (%G) Segment Portion 1

Segment 1 0.4 To 0.6 G 

Segment 2 0.5 To 0.6 G 

Segment 3 

(Beginning Of Segment Southwest Of Manix) 0.5 To 0.6 G 

Segment 3 

(Approximately Between Manix And Baker) 0.3 To 0.5 G 

Segment 3 

(Approximately Northeast Of Baker) 0.2 To 0.3 G 

Segment 4 

(In Mountain Pass Area Southwest Of Ivanpah 

Valley)

0.3 To 0.4 G 

Segment 4 

(Ivanpah Valley) 

0.4 To 0.6 G 

Segment 5 

(Ivanpah Valley) 

0.2 To 0.6 G 

Segment 5 

(Approximately North Of Ivanpah Valley) 0.1 To 0.2 G 

Segment 6 

(Las Vegas Valley) 0.1 To 0.2 G 2

Segment 7 

(City Of Las Vegas) 0.1 To 0.2 G 2

Notes:

1

 (Mualchin, 1996a) 

2

 (United States Geological Survey [Usgs], 2002rev)

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4.1.3. Liquefaction

Liquefaction is a phenomenon in which soil loses its shear strength for short periods of 

time during an earthquake. Ground shaking of sufficient duration can result in the loss 

of grain-to-grain contact, due to a rapid increase in pore water pressure, 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. 

The State of California Seismic Hazards Mapping Program produces maps identifying 

areas of the state susceptible to liquefaction but has not yet produced maps in the relatively less populated desert areas within the study area. The county of San Bernardino 

has identified some areas within the Alignment study area with potential for liquefaction 

based on where alluvial soils exist with shallow groundwater. These areas include: 

x Areas along the Mojave River; 

x Areas adjacent to certain faults that form groundwater barriers (which can cause 

groundwater to rise), such as areas southwest of the Calico fault near Barstow and 

southwest of the Lockhart fault west of Barstow; 

x The Mojave River Wash area south of the intersection of I-15 and Basin Road; and 

x The area between Baker and north toward Silver Lake. 

In the Nevada portion of the Alignment, our evaluation has indicated that the majority 

of the proposed segments are underlain by a relatively deep groundwater table. Areas of 

relatively shallow groundwater may exist along the Alignment, particularly in the Roach 

Lake area and the Las Vegas Valley near the north end of the Alignment, and these areas 

may have potential for liquefaction. A groundwater contour map of the Las Vegas Valley 

studied for our evaluation indicates that Segment 6 of the Alignment is underlain by a 

groundwater table that becomes shallower toward the northeast. This map indicates that 

the groundwater may be as deep as 400 feet below the surface near the south end of 

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Segment 6, and may be as shallow as 20 feet near the north end of Segment 6 and along 

Segment 7. 

Liquefaction could cause damage to the proposed rail improvements without appropriate consideration during design. The potential damaging effects of liquefaction include 

differential settlement, loss of ground support for foundations and other rail improvements, ground cracking, heaving and cracking of structure slabs due to sand boiling,

buckling of deep foundations due to liquefaction-induced ground settlement, and lateral 

spreading along embankments and natural slopes along drainages. 

4.1.4. Dam Inundation 

The county of San Bernardino has identified some areas within the Alignment study 

area with potential for inundation due to dam failure. County mapping data indicate the 

inundation would potentially occur from Lake Arrowhead and Silverado Lake in the 

San Bernardino Mountains south of the Alignment project area. The data indicate that 

inundation from these lakes would occur along the Mojave River in the Alignment project area between Victorville and Baker, which is the drainage course of the river. Since 

the potential inundation would occur along the Mojave River, portions of the following 

segments would be affected according to the map: 

x Segment 1, Alternative A. 

x Segment 2, Alternative A. 

x Portions of Segment 3, Alternatives A and B, located near the Cronese Valley and 

Soda Lake. 

California dams are monitored by various governmental agencies (such as the State of 

California Division of Safety of Dams and the U.S. Army Corps of Engineers) to guard 

against the threat of dam failure. Current design and construction practices, and ongoing 

programs of review, modification, seismic retrofitting or total reconstruction of existing 

dams are intended to see that dams are capable of withstanding the maximum credible 

earthquake (MCE) for the site. In addition, it is anticipated that the County of San Ber206725001 R Prelim Geo.doc F-J-59 52
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nardino has made provisions for flood control measures in areas of the Mojave River 

upstream of the Alignment to accommodate the anticipated inundation. 

Due to regulatory monitoring of dams and the probable flood control measures that are 

in place, the impact of inundation due to dam failure is not considered a significant constraint to the project. The effect of inundation would be temporary, and may necessitate 

minor maintenance in the affected segments to make the rail system operational. 

4.2. Regional Effects – Construction Period 

Environmental consequences of the affected environment that pertain to potential geologic 

hazards during the construction period of the rail system include settlement, corrosive soils, 

expansive soils, landslides, caliche/hard rock excavation, ground fissures, and shallow 

groundwater. Although the potential seismic hazards discussed in Section 4.1 are considered 

long-term consequences to the operational period of the rail system, those seismic hazards 

may affect the rail system during the construction period. These potential geologic hazards 

associated with the construction period of the project are further discussed in the following 

sections. Mitigation measures for these potential environmental consequences are presented 

in Section 6. 

4.2.1. Settlement (Natural Soils and Undocumented Fill) 

Much of the study area is mantled by young alluvial soils, which are generally poorly 

consolidated, reflecting a history without substantial loading. The older alluvial deposits 

present in the Alignment are generally relatively dense or weakly cemented and less 

compressible than the young alluvial soils. However, older alluvial deposits may include potentially collapsible layers above the groundwater table. Collapsible soils are 

distinguished by their potential to undergo a significant decrease in volume upon an increase in moisture content, even without an increase in external loads. 

Portions of the Alignment study area contain existing fill soils associated with roadway 

construction, railway construction, property and structure development, utilities, and 

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other factors. The degree of compaction, material types, and underlying ground conditions of existing fill soils in the study area is unknown. Undocumented or poorly 

compacted fill may be present in these areas. In addition, the Alignment transitions between highly variable materials ranging from loose soils to hard rock, and the potential 

for differential ground movement can exist at these transitions. 

Compressible natural soils and undocumented fills pose the risk of adverse settlement 

under static loads imposed by new embankment fills, shallow foundations for proposed 

rail system and associated structures. Differential settlement of soils can cause damage 

to project improvements including concrete structures and foundations, railway alignment, retaining walls, associated station and maintenance structures and pavements. 

Since the project will involve construction of new railway embankments, stations and 

maintenance facilities and other at-grade structures that will be loaded upon the existing 

soils, potential settlement and/or collapsible soils should be a consideration in design 

and construction of project improvements. Potential settlement of these surficial soils is 

generally not a constraint for construction of deep foundations, tunnels and other deep 

structures.

4.2.2. Corrosive Soils 

Potentially corrosive soils may be present along the alternative segments proposed for 

the Alignment. Corrosive soils, especially in areas of shallow groundwater that may be 

present in portions of the study area, can present a corrosion hazard to concrete and 

metal foundations, utilities, and other buried improvements. Areas of corrosive groundwater or soil could cause of premature deterioration of underground structures. 

4.2.3. Expansive Soils 

Potentially expansive soils may be present along the alternative segments proposed for 

the Alignment. Expansive soils are characterized by their ability to 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 

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clays. Changes in soil moisture content can result from rainfall, irrigation, utility leakage, surface drainage, perched groundwater, drought, or other factors. 

Volumetric change of expansive soil may cause excessive cracking and heaving of 

structures with shallow foundations, tunnel walls, concrete slabs-on-grade, or pavements supported on these materials. The relative potential impact of expansive soils is 

low for deep foundations such as for bridges and aerial guideways, since volumetric 

changes of expansive soils diminish with overburden depth. 

4.2.4. Landslides

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. Ground shaking due to earthquakes can also cause landslides to develop or trigger landslides that are incipient. Landslides can consist of rock falls, 

shallow slumps, flows and erosional failures, or deeper-seated rotational and block failures. Shallow failures are typically caused by high incident rainfall or concentrated 

surface runoff conditions that weaken surficial materials. Rotational and block-type 

slides form deeper within the ground, typically within rock formations, and are generally related to discontinuities in the rock that manifest into a sliding surface. Rainfall 

and other water infiltration into the ground can exacerbate and trigger these deeper sliding conditions. 

Our review of referenced geologic reports does not indicate the presence of previous 

landslide deposits along the proposed Alignment alternatives. Due to the relatively flatlying nature of the majority of the Alignment, landslide hazards should not be a significant constraint to the project in those areas of gentle slopes. Due to low average annual 

precipitation levels in the Alignment study area, the hazard of shallow type slope failures described above is considered low and not anticipated to significantly impact the 

project, with the exception of areas of moderately steep to steep terrain. Portions of the 

Alignment located in areas of moderate to steep terrain (especially the Mountain Pass 

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Segment 4, Alternative B) may have potential landslide hazards, and the stability of 

slopes in these areas should be further evaluated prior to design of project improvements. 

Review of geologic maps and other references indicate that surface soils along the 

Alignment are primarily comprised of sands with variable amounts of gravel, and some 

fine-grained silt and clay soils. Sandy soils typically have low cohesion, and have a 

relatively high potential for erosion from surface runoff when exposed in cut slopes or 

utilized near the face of fill embankments. These materials are also more susceptible to 

shallow slumps and other surficial slope failures when saturated by rain or heavy irrigation.

Slope areas within the project study area, including constructed cut slopes, fill slopes, 

natural slopes and rail embankments could potentially be affected by landsliding or 

surficial slope failures. Slopes may have potential for surficial slope failures during 

rainfall. Slopes cut in bedrock may be subject to rock fall, rock slides, or other rock 

slope failures where discontinuities, such as joints and fractures, or weathered rock are 

encountered. Landslides and surficial slope failures, if not mitigated, can cause damage 

to slopes, embankments, the rail alignment, foundations and other structures that are 

upon or impacted by the landslide. A landslide could potentially bury the rail Alignment, rendering it non-operational until the landslide debris is removed. 

4.2.5. Caliche/Hard Rock Excavation 

Based on our evaluation of geologic references and previous professional experience, 

we anticipate that the Quaternary alluvium in the desert of southern Nevada contains 

scattered layers of cemented soils (caliche) along portions of the Alignment. Caliche 

layers contain calcareous cementation which can be moderately hard, hard, and very 

hard and may range in thickness from a few inches to several feet. These soils may be 

resistant to excavation, and may pose an impact on construction techniques for both 

shallow and deep improvements for the rail system in the Las Vegas Valley. 

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Based on our review of geologic maps of the Alignment study area, portions of the 

Alignment are underlain by crystalline bedrock, and other rock types that may be hard. 

Depending on the depth of excavation into these materials, moderate to difficult excavation may be encountered. 

4.2.6. Ground Fissures 

Geologic maps of the Las Vegas Valley showing the locations of mapped ground fissures were reviewed, and the maps do not indicate known ground fissures fields within 

the Alignment study area. However, ground fissures may be present in areas not previously identified. Ground fissures, caused by differential stress resulting from regional 

and local subsidence associated with withdrawal of groundwater may occur near faults 

in the Las Vegas Valley. Differential movement associated with ground fissures could 

cause detrimental damage to surface project improvements such as rail alignment, shallow foundations, pavements, as well as the proposed Las Vegas maintenance facility 

and station. 

4.2.7. Shallow Groundwater 

Shallow groundwater has been identified in some segments of the Alignment. Due to 

the potentially shallow groundwater levels reported along segments of the Alignment, 

wet or saturated soil conditions may be encountered in excavations during construction. 

Groundwater in excavations can cause instability of the excavations, and present a constraint to the construction of foundations. Excavations extending below the groundwater 

table for deep foundations in areas with anticipated shallow groundwater, such as the 

Mojave River bridge and aerial guideways in Las Vegas, may need to be cased/shored 

and/or dewatered below the groundwater to maintain stability of the excavations and 

provide access for construction. Areas of shallow excavation and construction would be 

less affected by shallow groundwater. 

Shallow groundwater can also impact ground stability, and foundation design of proposed improvements, as well as the methods and costs of construction. If not adequately 

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monitored by the contractor, dewatering of excavations could induce consolidation of 

the underlying soils, which could cause differential settlement of existing structures and 

improvements located near the excavation. The amount of consolidation due to dewatering would depend on many factors, including the areal extent and depth of dewatering, 

soil type, soil density, and the methods used by the dewatering contractor. Excavations 

for the underground structures will need to be performed with care to reduce the potential for lateral deflection of excavation sidewalls and/or shoring, which could also cause 

differential movement of structures located near the excavation. 

4.3. Regional Effects by Segment 

The potential seismic and geologic hazards described in the previous sections that might affect improvements during the operational period and the construction period for each of the 

alternative alignment segments is presented below. The relative impact of the potential seismic and geologic hazards are summarized in Table 18 in Section 5. Mitigation measures for 

these potential seismic and geologic hazards are presented in Section 6. 

4.3.1. Segment 1 (Victorville to Lenwood, California) 

4.3.1.1. Operational Period Segment 1, Alternative A 

Surface Fault Rupture 

Segment 1, Alternative A, crosses the inferred, concealed trace of a potentially active portion of the Helendale-South Lockhart fault, and the relative potential impact 

of surface fault rupture in this segment, presented in Table 18, is considered moderate. Since surface fault rupture could cause detrimental damage to project 

improvements as described in Section 4.1.1., a detailed evaluation, as described in 

Section 6.1.1., could be performed to further evaluate the fault-rupture hazard. 

Mitigation measures to reduce the potential for fault-rupture hazard are presented in 

Section 6.1.1. 

Ground Shaking 

Due to the proximity to nearby active faults, the potential for strong ground motions to occur along Segment 1, Alternative A, is significant, and the relative 

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potential impact of ground shaking in this segment, presented in Table 18, is considered high. Based on the information provided on Figure 14, peak horizontal 

ground accelerations on the order of 0.4g to 0.6g could be anticipated along this 

segment. Since this level of ground shaking can cause detrimental damage to project improvements as described in Section 4.1.2., the potential for relatively high 

seismic accelerations will need to be evaluated in the design of the proposed improvements, as described in Section 6.1.2. Mitigation measures to reduce the 

potential ground shaking hazard are presented in Section 6.1.2. 

Liquefaction

Segment 1, Alternative A, travels along the bank of the Mojave River in an area of 

reported shallow groundwater, and by soils that have a potential for liquefaction. 

Due to these factors, the relative potential impact of liquefaction in this segment, 

presented in Table 18, is considered high. Liquefaction could cause significant 

damage to the proposed rail improvements, as discussed in Section 4.1.3. Accordingly, the liquefaction potential of the soils should be evaluated during the design 

phase of the project, as described in Section 6.1.3. Mitigation of the potential liquefaction hazard can be achieved through measures described in Section 6.1.3. 

Dam Inundation 

The potential for dam inundation to affect Segment 1, Alternative A has been identified by the County of San Bernardino. Since this segment is adjacent to the 

projected inundation course, the relative potential impact of dam inundation in this 

segment, presented in Table 18, is considered moderate. Due to the regulatory 

monitoring of dams and typical flood control measures that may exist, it is anticipated that the inundation effect would not be significant. The effects of dam 

inundation on the rail line, and the Victorville station and maintenance facility 

would be expected to be temporary, and may necessitate minor maintenance to 

make the rail system operational. 

4.3.1.2. Operational Period Segment 1, Alternative B 

Surface Rupture 

Segment 1, Alternative B, crosses the trace of the active Helendale-South Lockhart 

fault, zoned by the State of California as an Earthquake Fault Zone, and the relative 

potential impact of surface fault rupture in this segment, presented in Table 18, is 

considered high. Since surface fault rupture could cause detrimental damage to project improvements as described in Section 4.1.1., a more detailed evaluation, as 

described in Section 6.1.1., could be performed to further evaluate the fault-rupture 

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hazard. Mitigation of the potential fault-rupture hazard can be achieved through 

measures described in Section 6.1.1. 

Ground Shaking 

Based on the information provided on Figure 14, peak horizontal ground accelerations on the order of 0.4g to 0.6g could be anticipated along this segment. The 

ground shaking hazard for this alternative is the same as for Segment 1, Alternative A. Mitigation measures to reduce the potential ground shaking hazard are 

presented in Section 6.1.2. 

Liquefaction

Portions of Segment 1, Alternative B, may be underlain by soils that have a potential for liquefaction. Although shallow groundwater was not indicated in this 

segment in the information reviewed, areas of potentially shallow groundwater may 

exist. Due to these factors, Segment 1, Alternative B is considered to have a moderate liquefaction potential. Liquefaction could cause significant damage to the 

proposed rail improvements as discussed in Section 4.1.3. Accordingly, the liquefaction potential of the soils should be evaluated during the design phase of the 

project, as described in Section 6.1.3. Mitigation of the potential liquefaction hazard can be achieved through measures described in Section 6.1.3. 

Dam Inundation 

The southwest end of this segment near the location of the proposed Victorville station and maintenance facility is adjacent to the projected inundation course. The 

relative potential impact of dam inundation in this segment, presented in Table 18, 

is considered low, and is only anticipated to affect this end of the segment. Due to 

the regulatory monitoring of dams and typical flood control measures that may exist, it is anticipated that the inundation effect would not be significant. The effect 

would be temporary, and may necessitate minor maintenance to make the rail system operational. 

4.3.1.3. Construction Period Segment 1, Alternative A 

Settlement (Natural Soils and Undocumented Fills) 

As indicated on geologic maps reviewed, the surficial geology of Segment 1, Alternative A, is highly variable and includes Mesozoic and older crystalline basement 

rock and metavolcanic rock interfingered with younger and older alluvial deposits. 

The alluvium may contain compressible layers. Areas of previous development ex206725001 R Prelim Geo.doc F-J-67 60
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ist along this segment, and undocumented fill soils may exist. Due to the potential 

presence of compressible alluvium and undocumented fill along this segment, a potential for settlement under load of proposed new improvements exists, and the 

relative potential impact of settlement of these soils in this segment, presented in 

Table 18, is considered moderate. 

As discussed is Section 4.2.1., differential settlement of soils can cause damage to 

project improvements including concrete structures and foundations, railway 

alignment, retaining walls, associated station and maintenance structures and 

pavements. Prior to design and construction, a geotechnical evaluation should be 

performed as described in Section 6.2.1., to evaluate the potential settlement hazard. Mitigation of the potential settlement hazard can be achieved through measures 

described in Section 6.2.1. 

Corrosive Soils 

Potentially corrosive soils may be present along Segment 1, Alternative A. Corrosive soils, especially in areas of shallow groundwater that are reported in portions 

of Segment 1, Alternative A, can present a corrosion hazard to concrete and metal 

foundations, utilities, and other buried improvements. A more detailed evaluation, 

as described in Section 6.2.2., should be performed during the design phase of the 

project to evaluate the impacts and risks associated with the potential corrosive soil 

hazard. Mitigation of the potential corrosive soil hazard can be achieved through 

measures described in Section 6.2.2. 

Expansive Soils 

Potentially expansive soils may be present along Segment 1, Alternative A. The 

relative potential impact of expansive soils in this segment, presented in Table 18, 

is considered high due to clay units mapped in this segment. Expansive soils can 

undergo volumetric changes in response to moisture changes and could cause detrimental damage to improvements. Accordingly, a more detailed evaluation, as 

described in Section 6.2.3., should be performed during the design phase of the project to evaluate the impacts and risks associated with the potential expansive soil 

hazard. Mitigation of the potential expansive soil hazard can be achieved through 

measures described in Section 6.2.3.

Landslides

Much of Segment 1, Alternative A travels across areas of relatively gentle topography and the relative potential impact of landslides and surficial slope failures in this 

segment, presented in Table 18, is considered low. Stability analysis of slope areas 

within the segment, including constructed cut and fill slopes, rail embankments, 

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and natural slopes should be evaluated during the design phase of the project, as 

described in Section 6.2.4. Mitigation of the potential hazard of landslides and 

surficial slope failures can be achieved through measures described in Section 6.2.4. 

Caliche/Hard Rock Excavation 

Caliche layers have not been identified in Segment 1, Alternative A on the geologic 

references reviewed for the study area. Accordingly, the potential for excavation 

difficulties due to caliche is not anticipated to have a significant impact on Segment 1, Alternative A. 

Portions of Segment 1, Alternative A are underlain by crystalline bedrock, and 

other rock types that may be hard. Depending on the depth of excavation into these 

materials, moderate to difficult excavation may be encountered. The relative potential impact of excavation difficulties in this segment, presented in Table 18, is 

considered moderate. A more detailed evaluation, as described in Section 6.2.5., 

should be performed during the design phase of the project to evaluate the impacts 

associated with potential excavation difficulties. Mitigation of potential excavation 

difficulties can be achieved through measures described in Section 6.2.5.

Ground Fissures 

Ground fissures have not been identified in Segment 1, Alternative A on the geologic references reviewed for the study area. Accordingly, the potential ground 

fissure hazard, as discussed in Section 4.2.6., is not anticipated to have a significant 

impact on this segment.

Shallow Groundwater 

Shallow groundwater may be anticipated along portions of Segment 1, Alternative A, since this segment travels along the bank of the Mojave River in an area 

with reported shallow groundwater. Due to this potential for shallow groundwater, 

the relative potential impact of shallow groundwater in this segment, presented in 

Table 18, is considered high. As discussed in Section 4.2.7., shallow groundwater 

can impact excavations for deep foundations, below ground structures, and can impact ground stability, and foundation design of proposed improvements, as well as 

the methods and costs of construction. Prior to design and construction, a geotechnical engineering evaluation, as described in Section 6.2.7., should be undertaken 

to assess the groundwater conditions along the Alignment so that earthwork and 

foundation systems can be appropriately designed and constructed. Mitigation of 

the potential shallow groundwater hazard can be achieved through measures described in Section 6.2.7. 

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4.3.1.4. Construction Period Segment 1, Alternative B 

Settlement (Natural Soils and Undocumented Fills) 

The surficial geology of Segment 1, Alternative B, is highly variable and includes 

Mesozoic and older crystalline basement rock and metavolcanic rock interfingered 

with younger and older alluvial deposits. The alluvium may contain compressible 

layers. Areas of previous development exist along this segment, and undocumented 

fill soils may exist. Due to the potential presence of compressible alluvium and undocumented fill along this segment, a potential for settlement under load of 

proposed new improvements exists, and the relative potential impact of settlement 

of these soils in this segment, presented in Table 18, is considered moderate. Prior 

to design and construction, a geotechnical evaluation should be performed as described in Section 6.2.1., to evaluate the potential settlement hazard. Mitigation of 

the potential settlement hazard can be achieved through measures described in Section 6.2.1. 

Corrosive Soils 

The corrosive soils hazard for this segment is the same as for Segment 1, Alternative A. A more detailed evaluation, as described in Section 6.2.2., should be 

performed during the design phase of the project to evaluate the impacts and risks 

associated with the potential corrosive soil hazard. Mitigation of the potential corrosive soil hazard can be achieved through measures described in Section 6.2.2. 

Expansive Soils 

Potentially expansive soils may be present along Segment 1, Alternative B. The 

relative potential impact of expansive soils in this segment, presented in Table 18, 

is considered moderate. Accordingly, a more detailed evaluation, as described in 

Section 6.2.3., should be performed during the design phase of the project to evaluate the impacts and risks associated with the potential expansive soil hazard. 

Mitigation of the potential expansive soil hazard can be achieved through measures 

described in Section 6.2.3. 

Landslides

Much of Segment 1, Alternative B travels across areas of relatively gentle to moderate topography, and across previously undeveloped areas, and the relative 

potential impact of landslides and surficial slope failures in this segment, presented 

in Table 18, is considered moderate. In areas of moderate to steep topography, a 

higher potential for landslides and surficial slope failures exists. Landslides can 

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cause damage to the rail alignment, deep foundations and other structures that are 

upon or impacted by a landslide, as discussed in Section 4.2.4. Stability analysis of 

slope areas within the segment, including constructed cut and fill slopes, rail embankments, and natural slopes should be evaluated during the design phase of the 

project, as described in Section 6.2.4. Mitigation of the potential hazard of landslides and surficial slope failures can be achieved through measures described in 

Section 6.2.4. 

Caliche/Hard Rock Excavation 

The relative potential impact of excavation difficulties in this segment is the same 

as for Segment 1, Alternative A, and, as presented in Table 18, is considered moderate. Accordingly, a more detailed evaluation, as described in Section 6.2.5., 

should be performed during the design phase of the project to evaluate the impacts 

associated with potential excavation difficulties. Mitigation of potential excavation 

difficulties can be achieved through measures described in Section 6.2.5.

Ground Fissures 

Ground fissures have not been identified in Segment 1, Alternative B on the geologic references reviewed for the study area. Accordingly, the potential ground 

fissure hazard, as discussed in Section 4.2.6., is not anticipated to have a significant 

impact on this segment.

Shallow Groundwater 

Although shallow groundwater was not indicated in Segment 1, Alternative B in information reviewed, areas of potentially shallow groundwater may exist. The 

relative potential impact of shallow groundwater in this segment, presented in Table 18, is considered low. As discussed in Section 4.2.7., shallow groundwater can 

impact excavations for deep foundations and below ground structures, such as for 

the proposed aerial guideways in this segment, and can impact ground stability, and 

foundation design of proposed improvements, as well as the methods and costs of 

construction. Prior to design and construction, a geotechnical engineering evaluation as described in Section 6.2.7., should be undertaken to assess the groundwater 

conditions along the Alignment so that earthwork and foundation systems can be 

appropriately designed and constructed. Mitigation of the potential shallow 

groundwater hazard can be achieved through measures described in Section 6.2.7. 

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4.3.2. Segment 2 (Lenwood to Yermo, California) 

4.3.2.1. Operational Period Segment 2, Alternative A 

Surface Fault Rupture 

Segment 2, Alternative A, crosses the active zone of the Lockhart-Lenwood fault 

north of Lenwood. The Lenwood fault to the southeast of this segment is zoned by 

the State of California as an Earthquake Fault Zone. Segment 2, Alternative A, 

crosses the concealed trace of the active Mt. General fault, zoned by the State of 

California as an Earthquake Fault Zone. Segment 2, Alternative A, crosses the concealed trace of a potentially active portion of the Gravel Hills-Harper Lake fault. 

Due to the proximity of these active faults crossing the proposed Alignment, the 

relative potential impact of surface fault rupture in this segment, presented in Table 18, is considered high. Since surface fault rupture could cause detrimental 

damage to project improvements, as described in Section 4.1.1, a more detailed 

evaluation, as described in Section 6.1.1, should be performed during the design 

phase of the project to evaluate the impacts and risks associated with the potential 

fault-rupture hazard. Mitigation measures to reduce the potential fault-rupture hazard are presented in Section 6.1.1. 

Ground Shaking 

Due to the proximity to nearby active faults, the potential for strong ground motions to occur along Segment 2, Alternative A, is significant, and the relative 

potential impact of ground shaking in this segment, presented in Table 18, is considered high. Based on the information provided on Figure 14, peak horizontal 

ground accelerations on the order of 0.5g to 0.6g could be anticipated along this 

segment. Since this level of ground shaking can cause detrimental damage to project improvements, as described in Section 4.1.2, the potential for relatively high 

seismic accelerations will need to be evaluated in the design of the proposed improvements, as described in Section 6.1.2. Mitigation of the potential ground 

shaking hazard can be achieved through measures described in Section 6.1.2. 

Liquefaction

Segment 2, Alternative A, is located in the Mojave River Valley, crosses the Mojave 

River, and travels along the banks of the river in an area with reported shallow 

groundwater and by soils that have a potential for liquefaction. Due to these factors, 

the relative potential impact of liquefaction in this segment, presented in Table 18, 

is considered high. Liquefaction could cause significant damage to the proposed 

rail improvements, as discussed in Section 4.1.3. Accordingly, the liquefaction potential of the soils should be evaluated during the design phase of the project, as 

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described in Section 6.1.3. Mitigation of the potential liquefaction hazard can be 

achieved through measures described in Section 6.1.3. 

Dam Inundation 

Segment 2, Alternative A travels adjacent to the Mojave River, which is the projected course of inundation flow due to dam failure. Since this segment is adjacent 

to the projected inundation course, the relative potential impact of dam inundation 

in this segment, presented in Table 18, is considered moderate. Due to the regulatory monitoring of dams and typical flood control measures that may exist, it is 

anticipated that the inundation effect would not be significant. If inundation were to 

occur, the effect would be temporary, and may necessitate minor maintenance to 

make the rail system operational. 

4.3.2.2. Operational Period Segment 2, Alternative B 

Surface Fault Rupture 

Based on geologic and seismic maps reviewed, no active faults cross the Alignment 

in Segment 2, Alternative B. Accordingly, the potential surface fault rupture hazard 

discussed in section 4.1.1. is not anticipated to have a significant impact on Segment 2, Alternative B. 

Ground Shaking 

Based on the information provided on Figure 14, peak horizontal ground accelerations on the order of 0.5g to 0.6g could be anticipated along this segment. The 

ground shaking hazard for this alternative is the same as for Segment 2, Alternative A. Mitigation measures to reduce the potential ground shaking hazard are 

presented in Section 6.1.2. 

Liquefaction

Segment 2, Alternative B, is located in the Mojave River Valley in an area with reported shallow groundwater and by soils that have a potential for liquefaction. Due 

to these factors, the relative potential impact of liquefaction in this segment, presented in Table 18, is considered high. Liquefaction could cause significant damage 

to the proposed rail improvements, as discussed in Section 4.1.3. Accordingly, the 

liquefaction potential of the soils should be evaluated during the design phase of 

the project, as described in Section 6.1.3. Mitigation of the potential liquefaction 

hazard can be achieved through measures described in Section 6.1.3. 

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Dam Inundation 

The potential for dam inundation for this segment is the same as for Segment 2, Alternative A. Due to the regulatory monitoring of dams and typical flood control 

measures that may exist, it is anticipated that the inundation effect would not be 

significant. The effect would be temporary, and may necessitate minor maintenance 

to make the rail system operational. 

4.3.2.3. Construction Period Segment 2, Alternative A 

Settlement (Natural Soils and Undocumented Fills) 

As indicated on geologic maps reviewed, the surficial geology of Segment 2, Alternative A, is highly variable and includes Mesozoic and older crystalline basement 

rocks, metavolcanic rocks and Tertiary lithified volcanic and sedimentary rocks interfingered with younger and older alluvial deposits, including potentially 

compressible clays. The alluvium may contain compressible layers. Areas of previous development exist along this segment, and undocumented fill soils may exist. 

Due to the potential presence of compressible alluvium and undocumented fill 

along this segment, a potential for settlement under load of proposed new improvements exists, and the relative potential impact of settlement of these soils in 

this segment, presented in Table 18, is considered moderate. 

Compressible natural soils and undocumented fills pose the risk of adverse settlement under static loads imposed by new embankment fills, shallow foundations for 

proposed rail system and associated structures. As discussed is Section 4.1.8, differential settlement of soils can cause damage to project improvements including 

concrete structures and foundations, railway alignment, retaining walls, associated 

station and maintenance structures and pavements. Prior to design and construction, 

a geotechnical evaluation should be performed as described in Section 6.2.1, to 

evaluate the potential settlement hazard. Mitigation of the potential settlement hazard can be achieved through measures described in Section 6.2.1. 

Corrosive Soils 

Corrosive soils, especially in areas of shallow groundwater that are reported in portions of Segment 2, Alternative A, can present a corrosion hazard to concrete and 

metal foundations, utilities, and other buried improvements. A more detailed 

evaluation, as described in Section 6.2.2., should be performed during the design 

phase of the project to evaluate the impacts and risks associated with the potential 

corrosive soil hazard. Mitigation of the potential corrosive soil hazard can be 

achieved through measures described in Section 6.2.2. 

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Expansive Soils 

Potentially expansive soils may be present along Segment 2, Alternative A. The 

relative potential impact of expansive soils in this segment, presented in Table 18, 

is considered high due to clay units mapped in this segment. Expansive soils can 

undergo volumetric changes in response to moisture changes and could cause detrimental damage to improvements. Accordingly, a more detailed evaluation, as 

described in Section 6.2.3., should be performed during the design phase of the project to evaluate the impacts and risks associated with the potential expansive soil 

hazard. Mitigation of the potential expansive soil hazard can be achieved through 

measures described in Section 6.2.3. 

Landslides

Much of Segment 2, Alternative A travels across areas of relatively gentle to moderate topography, and the relative potential impact of landslides and surficial slope 

failures in this segment, presented in Table 18, is considered moderate. In areas of 

moderate to steep topography, a higher potential for landslides exists. Landslides 

can cause damage to the rail alignment, foundations and other structures that are 

upon or impacted by a landslide, as discussed in Section 4.2.4. Stability analysis of 

slope areas within the project study area, including proposed cut slopes, fill slopes 

and rail embankments should be evaluated during the design phase of the project, 

as described in Section 6.2.4. Mitigation of the potential hazard of landslides and 

surficial slope failures can be achieved through measures described in Section 6.2.4. 

Caliche/Hard Rock Excavation 

Caliche layers have not been identified in Segment 2, Alternative A on the geologic 

references reviewed for the study area. Accordingly, the potential for excavation 

difficulties due to caliche is not anticipated to affect Segment 2, Alternative A. 

Based on our review of geologic maps of the Alignment study area, portions of 

Segment 2, Alternative A are underlain by crystalline bedrock, and other rock types 

that may be hard. Depending on the depth of excavation into these materials, moderate to difficult excavation may be encountered. The relative potential impact of 

excavation difficulties in this segment, presented in Table 18, is considered moderate. A more detailed evaluation, as described in Section 6.2.5., should be performed 

during the design phase of the project to evaluate the impacts associated with potential excavation difficulties. Mitigation of potential excavation difficulties can be 

achieved through measures described in Section 6.2.5.

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Ground Fissures 

Ground fissures have not been identified in Segment 2, Alternative A on the geologic references reviewed for the study area. Accordingly, the potential ground 

fissure hazard discussed in section 4.2.6., is not anticipated to affect Segment 2, Alternative A.

Shallow Groundwater 

Shallow groundwater may be anticipated along portions of Segment 2, Alternative A, since this segment travels along the banks of the Mojave River in an area 

with reported shallow groundwater. Due to this potential for shallow groundwater, 

the relative potential impact of shallow groundwater in this segment, presented in 

Table 18, is considered high. As discussed in Section 4.2.7., shallow groundwater 

can impact excavations for deep foundations and below ground structures, such as 

for the proposed bridge across the Mojave River; and can impact ground stability, 

and foundation design of proposed improvements, as well as the methods and costs 

of construction. Prior to design and construction, a geotechnical engineering 

evaluation as described in Section 6.2.7., should be undertaken to assess the 

groundwater conditions along the Alignment so that earthwork and foundation systems can be appropriately designed and constructed. Mitigation of the potential 

shallow groundwater hazard can be achieved through measures described in Section 6.2.7.

4.3.2.4. Construction Period Segment 2, Alternative B 

Settlement (Natural Soils and Undocumented Fills) 

As indicated on geologic maps reviewed, the surficial geology of Segment 2, Alternative B, is highly variable and includes Mesozoic and older crystalline basement 

rocks, metavolcanic rocks and Tertiary lithified volcanic and sedimentary rocks interfingered with younger and older alluvial deposits. The alluvium may contain 

compressible layers, including potentially compressible clays. Areas of previous 

development exist along this segment, and undocumented fill soils may exist. Due 

to the potential presence of compressible alluvium and undocumented fill along this 

segment, a potential for settlement under load of proposed new improvements exists, and the relative potential impact of settlement of these soils in this segment, 

presented in Table 18, is considered moderate. 

Compressible natural soils and undocumented fills pose the risk of adverse settlement under static loads imposed by new embankment fills, shallow foundations for 

proposed rail system and associated structures. As discussed is Section 4.2.1., differential settlement of soils can cause damage to project improvements including 

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concrete structures and foundations, railway alignment, retaining walls, associated 

station and maintenance structures and pavements. Prior to design and construction, 

a geotechnical evaluation should be performed as described in Section 6.2.1, to 

evaluate the potential settlement hazard. Mitigation of the potential settlement hazard can be achieved through measures described in Section 6.2.1. 

Corrosive Soils 

The corrosive soils hazard for this segment is the same as for Segment 2, Alternative A. A more detailed evaluation, as described in Section 6.2.2., should be 

performed during the design phase of the project to evaluate the impacts and risks 

associated with the potential corrosive soil hazard. Mitigation of the potential corrosive soil hazard can be achieved through measures described in Section 6.2.2. 

Expansive Soils 

The expansive soils hazard for this segment is the same as for Segment 2, Alternative A. A more detailed evaluation, as described in Section 6.2.3., should be 

performed during the design phase of the project to evaluate the impacts and risks 

associated with the potential expansive soil hazard. Mitigation of the potential expansive soil hazard can be achieved through measures described in Section 6.2.3. 

Landslides

Much of Segment 2, Alternative B travels across areas of relatively gentle topography with the exception of a hilly area of moderate topography at the west end of the 

segment. Since the topography is gentle across much of this segment, the relative 

potential impact of landslides and surficial slope failures in this segment, presented 

in Table 18, is considered low. In areas of moderate to steep topography, a higher 

potential for landslides exists. Landslides can cause damage to the rail alignment, 

foundations and other structures that are upon or impacted by a landslide, as discussed in Section 4.2.4. Stability analysis of slope areas within the project study 

area, including proposed cut slopes, fill slopes, rail embankments, and natural 

slopes should be evaluated during the design phase of the project, as described in 

Section 6.2.4. Mitigation of the potential hazard of landslides and surficial slope 

failures can be achieved through measures described in Section 6.2.4. 

Caliche/Hard Rock Excavation 

Caliche layers have not been identified in Segment 2, Alternative B on the geologic 

references reviewed for the study area. Accordingly, the potential for excavation 

difficulties due to caliche is not anticipated to affect Segment 2, Alternative B. 

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Based on our review of geologic maps of the Alignment study area, portions of 

Segment 2, Alternative B are underlain by volcanic bedrock, and other rock types 

that may be hard. Depending on the depth of excavation into these materials, moderate to difficult excavation may be encountered. The relative potential impact of 

excavation difficulties in this segment, presented in Table 18, is considered moderate. A more detailed evaluation, as described in Section 6.2.5., should be performed 

during the design phase of the project to evaluate the impacts associated with potential excavation difficulties. Mitigation of potential excavation difficulties can be 

achieved through measures described in Section 6.2.5. 

Ground Fissures 

Ground fissures have not been identified in Segment 2, Alternative B on the geologic references reviewed for the study area. Accordingly, the potential ground 

fissure hazard discussed in Section 4.2.6., is not anticipated to affect Segment 2, Alternative B. 

Shallow Groundwater 

Shallow groundwater may be anticipated along portions of Segment 2, Alternative B, since this segment travels in the Mojave River valley in an area with 

reported shallow groundwater. Due to this potential for shallow groundwater, the 

relative potential impact of shallow groundwater in this segment, presented in Table 18, is considered high. As discussed in Section 4.2.7., shallow groundwater can 

impact excavations for deep foundations and below ground structures, such as for 

the proposed aerial guideways in this segment; and can impact ground stability, and 

foundation design of proposed improvements, as well as the methods and costs of 

construction. Prior to design and construction, a geotechnical engineering evaluation as described in Section 6.2.7., should be undertaken to assess the groundwater 

conditions along the Alignment so that earthwork and foundation systems can be 

appropriately designed and constructed. Mitigation of the potential shallow 

groundwater hazard can be achieved through measures described in Section 6.2.7.

4.3.3. Segment 3 (Yermo to Mountain Pass, California) 

4.3.3.1. Operational Period Segment 3, Alternatives A and B 

Surface Fault Rupture 

Segment 3, Alternatives A and B, cross the concealed trace of the active CalicoHidalgo fault, zoned by the State of California as an Earthquake Fault Zone. Segment 3, Alternatives A and B, cross an active portion of the Manix fault. Segment 3, 

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Alternatives A and B, cross an unnamed (Cronese Valley), concealed fault, and 

cross the potentially active Baker fault. Due to the proximity of these active and potentially active faults crossing the proposed Alignment, the relative potential impact 

of surface fault rupture in this segment, presented in Table 18, is considered high. 

Since surface fault rupture could cause detrimental damage to project improvements, as described in Section 4.1.1, a more detailed evaluation, as described in 

Section 6.1.1., should be performed during the design phase of the project to evaluate the impacts and risks associated with the potential fault-rupture hazard. 

Mitigation of the potential fault-rupture hazard such as locating improvements 

away from the fault trace and designing the improvements for rupture can be 

achieved through measures described in Section 6.1.1. 

Ground Shaking 

Due to the proximity to nearby active faults, the potential for strong ground motions to occur along Segment 3, Alternatives A and B, is significant, and the relative 

potential impact of ground shaking in this segment, presented in Table 18, is considered moderate to high. Based on the information provided on Figure 14, peak 

horizontal ground accelerations on the order of 0.5g to 0.6g could be anticipated 

along this segment southwest of Manix. Between Manix and Baker along Segment 3, peak horizontal ground accelerations on the order of 0.3g to 0.5g could be 

anticipated. Northeast of Baker, peak horizontal ground accelerations on the order 

of 0.2g to 0.3g could be anticipated along this segment. Since this level of ground 

shaking can cause detrimental damage to project improvements, as described in 

Section 4.1.2, the potential for relatively high seismic accelerations will need to be 

evaluated in the design of the proposed improvements, as described in Section 6.1.2. Mitigation of the potential ground shaking hazard can be achieved 

through measures described in Section 6.1.2. 

Liquefaction

Segment 3, Alternatives A and B, crosses the Mojave River Valley, Soda Lake, Valley Wells, and other areas with reported shallow groundwater and by soils that have 

a potential for liquefaction. Due to these factors, the relative potential impact of 

liquefaction in this segment, presented in Table 18, is considered moderate to high. 

Liquefaction could cause significant damage to the proposed rail improvements, as 

discussed in Section 4.1.3. Accordingly, the liquefaction potential of the soils 

should be evaluated during the design phase of the project, as described in Section 6.1.3. Mitigation of the potential liquefaction hazard can be achieved through 

measures described in Section 6.1.3. 

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Dam Inundation 

The potential for dam inundation to affect portions of Segment 3, Alternatives A 

and B has been identified by the County of San Bernardino, since this segment

travels near the Mojave River and across Soda Lake, the projected course of inundation flow due to dam failure. Since this segment is adjacent to the projected 

inundation course, the relative potential impact of dam inundation in this segment, 

presented in Table 18, is considered moderate. Due to the regulatory monitoring of 

dams and typical flood control measures that may exist, it is anticipated that the inundation effect would not be significant. The effect would be temporary, and may 

necessitate minor maintenance to make the rail system operational. 

4.3.3.2. Construction Period Segment 3, Alternatives A and B 

Settlement (Natural Soils and Undocumented Fills) 

As indicated on geologic maps reviewed, the surficial geology of Segment 3, Alternatives A and B, is highly variable and includes Mesozoic and older crystalline 

basement rocks, metavolcanic rocks and Tertiary lithified volcanic and sedimentary 

rocks interfingered with younger and older alluvial deposits. The alluvium may 

contain compressible layers, including potentially compressible clays. Areas of 

previous development exist along this segment, and undocumented fill soils may 

exist. Due to the potential presence of compressible alluvium and undocumented 

fill along this segment, a potential for settlement under load of proposed new improvements exists, and the relative potential impact of settlement of these soils in 

this segment, presented in Table 18, is considered moderate. 

Compressible natural soils and undocumented fills pose the risk of adverse settlement under static loads imposed by new embankment fills, shallow foundations for 

proposed rail system and associated structures. As discussed is Section 4.2.1., differential settlement of soils can cause damage to project improvements including 

concrete structures and foundations, railway alignment, retaining walls, associated 

station and maintenance structures and pavements. Prior to design and construction, 

a geotechnical evaluation should be performed as described in Section 6.2.1, to 

evaluate the potential settlement hazard. Mitigation of the potential settlement hazard can be achieved through measures described in Section 6.2.1. 

Corrosive Soils 

Potentially corrosive soils may be present along Segment 3, Alternatives A and B. 

Corrosive soils, especially in areas of shallow groundwater that are reported in portions of Segment 3, Alternatives A and B, can present a corrosion hazard to 

concrete and metal foundations, utilities, and other buried improvements. A more 

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detailed evaluation, as described in Section 6.2.2., should be performed during the 

design phase of the project to evaluate the impacts and risks associated with the potential corrosive soil hazard. Mitigation of the potential corrosive soil hazard can be 

achieved through measures described in Section 6.2.2. 

Expansive Soils 

Potentially expansive soils may be present along Segment 3, Alternatives A and B. 

The relative potential impact of expansive soils in this segment, presented in Table 18, is considered moderate. Expansive soils can undergo volumetric changes in 

response to moisture changes and could cause detrimental damage to improvements, as described in Section 4.2.3. Accordingly, a more detailed evaluation, as 

described in Section 6.2.3., should be performed during the design phase of the project to evaluate the impacts and risks associated with the potential expansive soil 

hazard. Mitigation of the potential expansive soil hazard can be achieved through 

measures described in Section 6.2.3.

Landslides

Much of Segment 3, Alternatives A and B travels across areas of relatively gentle to 

moderate topography, and the relative potential impact of landslides and surficial 

slope failures in this segment, presented in Table 18, is considered moderate. In areas of moderate to steep topography, a higher potential for landslides exists. 

Landslides can cause damage to the rail alignment, foundations and other structures 

that are upon or impacted by a landslide, as discussed in Section 4.2.4. Slope areas 

within the project study area, including constructed cut slopes, fill slopes and rail 

embankments could potentially be affected by surficial slope failures, as discussed 

in section 4.2.4. Accordingly, the potential for landslides and surficial slope failures 

to affect this segment of the project should be evaluated during the design phase of 

the project, as described in Section 6.2.4. Mitigation of the potential hazard of landslides and surficial slope failures can be achieved through measures described in 

Section 6.2.4.

Caliche/Hard Rock Excavation 

Caliche layers have not been identified in Segment 3, Alternatives A and B on the 

geologic references reviewed for the study area. Accordingly, the potential for excavation difficulties due to caliche is not anticipated to affect Segment 3, 

Alternatives A and B. 

Based on our review of geologic maps of the Alignment study area, portions of 

Segment 3, Alternatives A and B are underlain by crystalline and volcanic bedrock, 

and other rock types that may be hard. Depending on the depth of excavation into 

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these materials, moderate to difficult excavation may be encountered. The relative 

potential impact of excavation difficulties in this segment, presented in Table 18, is 

considered moderate. A more detailed evaluation, as described in Section 6.2.5., 

should be performed during the design phase of the project to evaluate the impacts 

associated with potential excavation difficulties. Mitigation of potential excavation 

difficulties can be achieved through measures described in Section 6.2.5. 

Ground Fissures 

Ground fissures have not been identified in Segment 3, Alternatives A and B on the 

geologic references reviewed for the study area. Accordingly, the potential ground 

fissure hazard discussed in section 4.2.6., is not anticipated to affect Segment 3, Alternatives A and B. 

Shallow Groundwater 

Shallow groundwater may be anticipated along portions of Segment 3, Alternatives A and B, since this segment crosses the Mojave River Valley, Soda Lake, 

Valley Wells, and other areas with reported shallow groundwater. Due to this potential for shallow groundwater, the relative potential impact of shallow groundwater 

in this segment, presented in Table 18, is considered high. As discussed in Section 4.2.7., shallow groundwater can impact excavations for deep foundations and 

below ground structures; and can impact ground stability, and foundation design of 

proposed improvements, as well as the methods and costs of construction. Prior to 

design and construction, a geotechnical engineering evaluation as described in Section 6.2.7., should be undertaken to assess the groundwater conditions along the 

Alignment so that earthwork and foundation systems can be appropriately designed 

and constructed. Mitigation of the potential shallow groundwater hazard can be 

achieved through measures described in Section 6.2.7. 

4.3.4. Segment 4 (Mountain Pass to State Line) 

4.3.4.1. Operational Period Segment 4, Alternative A 

Surface Fault Rupture 

Based on geologic and seismic maps reviewed, no active faults cross the Alignment 

in Segment 4, Alternative A. Accordingly, the potential surface fault rupture hazard 

discussed in section 4.1.1 is not anticipated to affect Segment 4, Alternative A. 

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Ground Shaking 

Due to the proximity to nearby active faults, the potential for strong ground motions to occur along Segment 4, Alternative A, is significant, and the relative 

potential impact of ground shaking in this segment, presented in Table 18, is considered moderate to high. Based on the information provided on Figure 14, peak 

horizontal ground accelerations on the order of 0.3g to 0.4g could be anticipated 

along this segment in the Mountain Pass area, while peak horizontal ground accelerations on the order of 0.4g to 0.6g could be anticipated in the Ivanpah Valley area 

of this segment. Since this level of ground shaking can cause detrimental damage to 

project improvements, as described in Section 4.1.2, the potential for relatively 

high seismic accelerations will need to be evaluated in the design of the proposed 

improvements, as described in Section 6.1.2. Mitigation of the potential ground 

shaking hazard can be achieved through measures described in Section 6.1.2. 

Liquefaction

Segment 4, Alternative A, travels along the Wheaton Wash area and across the 

Ivanpah Valley, and, although shallow groundwater was not indicated in these areas 

in information reviewed, potentially shallow groundwater may exist. Soils with a 

potential for liquefaction may exist in this segment, and the relative potential impact of liquefaction in this segment, presented in Table 18, is considered low. 

Liquefaction could cause significant damage to the proposed rail improvements, as 

discussed in Section 4.1.3. Accordingly, the liquefaction potential of the soils 

should be evaluated during the design phase of the project, as described in Section 6.1.3. Mitigation of the potential liquefaction hazard can be achieved through 

measures described in Section 6.1.3.

Dam Inundation 

Based on information reviewed, the potential for dam inundation to affect Segment 

4, Alternative A is remote since the potential inundation area associated with the 

Mojave River ends in Soda Lake in Segment 3. Accordingly, the potential dam inundation hazard discussed in Section 4.1.4. is not anticipated to affect Segment 4, 

Alternative A. 

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4.3.4.2. Operational Period Segment 4, Alternative B 

Surface Fault Rupture 

Based on geologic and seismic maps reviewed, no active faults cross the Alignment 

in Segment 4, Alternative B. Accordingly, the potential surface fault rupture hazard 

discussed in section 4.1.1. is not anticipated to affect Segment 4, Alternative A. 

Ground Shaking 

Due to the proximity to nearby active faults, the potential for strong ground motions to occur along Segment 4, Alternative B, is significant, and the relative 

potential impact of ground shaking in this segment, presented in Table 18, is considered moderate to high. Based on the information provided on Figure 14, peak 

horizontal ground accelerations on the order of 0.3g to 0.4g could be anticipated 

along this segment in the Mountain Pass area, while peak horizontal ground accelerations on the order of 0.4g to 0.6g could be anticipated in the Ivanpah Valley area 

of this segment. Since this level of ground shaking can cause detrimental damage to 

project improvements, as described in Section 4.1.2, the potential for relatively 

high seismic accelerations will need to be evaluated in the design of the proposed 

improvements, as described in Section 6.1.2. Mitigation of the potential ground 

shaking hazard can be achieved through measures described in Section 6.1.2. 

Liquefaction

Segment 4, Alternative B, crosses the Ivanpah Valley, and, although shallow 

groundwater was not indicated in this area in information reviewed, potentially 

shallow groundwater may exist. Soils with a potential for liquefaction may exist in 

this segment, and the relative potential impact of liquefaction in this segment, presented in Table 16, is considered low. Liquefaction could cause significant damage 

to the proposed rail improvements, as discussed in Section 4.1.3. Accordingly, the 

liquefaction potential of the soils should be evaluated during the design phase of 

the project, as described in Section 6.1.3. Mitigation of the potential liquefaction 

hazard can be achieved through measures described in Section 6.1.3. 

Dam Inundation 

Based on information reviewed, these is no potential for dam inundation to affect 

Segment 4, Alternative B since the potential inundation area associated with the 

Mojave River ends in Soda Lake in Segment 3. Accordingly, the potential dam inundation hazard discussed in section 4.1.4., is not anticipated to affect Segment 4, 

Alternative 8. 

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4.3.4.3. Construction Period Segment 4, Alternative A 

Settlement (Natural Soils and Undocumented Fills) 

As indicated on the geologic maps reviewed, the surficial geology of Segment Alternative A, is variable and includes Precambrian metamorphic basement 

rocks mantled with younger and older alluvial deposits. The alluvium may contain 

compressible layers. Areas of previous development exist along this segment, and 

undocumented fill soils may exist. Due to the potential presence of compressible alluvium and undocumented fill along this segment, a potential for settlement under 

load of proposed new improvements exists, and the relative potential impact of settlement of these soils in this segment, presented in Table 18, is considered 

moderate.

Compressible natural soils and undocumented fills pose the risk of adverse settlement under static loads imposed by new embankment fills, shallow foundations for 

proposed rail system and associated structures. As discussed is Section 4.2.1., differential settlement of soils can cause damage to project improvements including 

concrete structures and foundations, railway alignment, retaining walls, associated 

station and maintenance structures and pavements. Prior to design and construction, 

a geotechnical evaluation should be performed as described in Section 6.2.1., to 

evaluate the potential settlement hazard. Mitigation of the potential settlement hazard can be achieved through measures described in Section 6.2.1.

Corrosive Soils 

Potentially corrosive soils may be present along Segment 4, Alternative A. Corrosive soils, especially in areas of shallow groundwater that may exist in portions of 

Segment 4, Alternative A, can present a corrosion hazard to concrete and metal 

foundations, utilities, and other buried improvements. A more detailed evaluation, 

as described in Section 6.2.2., should be performed during the design phase of the 

project to evaluate the impacts and risks associated with the potential corrosive soil 

hazard. Mitigation of the potential corrosive soil hazard can be achieved through 

measures described in Section 6.2.2. 

Expansive Soils 

Potentially expansive soils may be present along Segment 4, Alternative A. The 

relative potential impact of expansive soils in this segment, presented in Table 18, 

is considered moderate. Expansive soils can undergo volumetric changes in response to moisture changes and could cause detrimental damage to improvements, 

as described in Section 4.2.3. Accordingly, a more detailed evaluation, as described 

in Section 6.2.3., should be performed during the design phase of the project to 

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evaluate the impacts and risks associated with the potential expansive soil hazard. 

Mitigation of the potential expansive soil hazard can be achieved through measures 

described in Section 6.2.3. 

Landslides

Portions of Segment 4, Alternative A travels across areas of relatively gentle to 

moderate topography, and the relative potential impact of landslides and surficial 

slope failures in this segment, presented in Table 18, is considered moderate. In areas of moderate to steep topography, a higher potential for landslides exists. 

Landslides can cause damage to the rail alignment, foundations and other structures 

that are upon or impacted by a landslide, as discussed in Section 4.2.4. Stability 

analysis of slope areas within the project study area, including natural slopes, and 

proposed cut slopes, fill slopes and rail embankments should be performed during 

the design phase of the project, as described in Section 6.2.4. Mitigation of the potential hazard of landslides and surficial slope failures can be achieved through 

measures described in Section 6.2.4. 

Caliche/Hard Rock Excavation 

Caliche layers have not been identified in Segment 4, Alternative A on the geologic 

references reviewed for the study area. Accordingly, the potential for excavation 

difficulties due to caliche is not anticipated to affect Segment 4, Alternative A. 

Based on our review of geologic maps of the Alignment study area, portions of 

Segment 4, Alternative A are underlain by crystalline bedrock. Depending on the 

depth of excavation into these materials, moderate to difficult excavation may be 

encountered. The relative potential impact of excavation difficulties in this segment, presented in Table 18, is considered moderate. A more detailed evaluation, as 

described in Section 6.2.5., should be performed during the design phase of the project to evaluate the impacts associated with potential excavation difficulties. 

Mitigation of potential excavation difficulties can be achieved through measures 

described in Section 6.2.5.

Ground Fissures 

Ground fissures have not been identified in Segment 4, Alternative A on the geologic references reviewed for the study area. Accordingly, the potential ground 

fissure hazard discussed in Section 4.2.6., is not anticipated to affect Segment 4, Alternative A. 

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Shallow Groundwater 

Although not reported in information reviewed, shallow groundwater may be anticipated along portions of Segment 4, Alternative A, and the relative potential 

impact of shallow groundwater in this segment, presented in Table 18, is considered 

low. As discussed in Section 4.2.7., shallow groundwater can impact excavations 

for deep foundations and below ground structures, and can impact ground stability, 

and foundation design of proposed improvements, as well as the methods and costs 

of construction. Prior to design and construction, a geotechnical engineering 

evaluation as described in Section 6.2.7., should be undertaken to assess the 

groundwater conditions along the Alignment so that earthwork and foundation systems can be appropriately designed and constructed. Mitigation of the potential 

shallow groundwater hazard can be achieved through measures described in Section 6.2.7. 

4.3.4.4. Construction Period Segment 4, Alternative B 

Settlement (Natural Soils and Undocumented Fills) 

As indicated on the geologic maps reviewed, the surficial geology of Segment 4, 

Alternative B, is variable and includes Precambrian metamorphic basement rocks 

mantled with younger and older alluvial deposits. The alluvium may contain compressible layers. Some areas of previous development exist along this segment, and 

undocumented fill soils may exist. Due to the potential presence of compressible alluvium and undocumented fill along this segment, a potential for settlement under 

load of proposed new improvements exists, and the relative potential impact of settlement of these soils in this segment, presented in Table 18, is considered 

moderate.

Compressible natural soils and undocumented fills pose the risk of adverse settlement under static loads imposed by new embankment fills, shallow foundations for 

proposed rail system and associated structures. As discussed is Section 4.2.1., differential settlement of soils can cause damage to project improvements including 

concrete structures and foundations, railway alignment, retaining walls, associated 

station and maintenance structures and pavements. Prior to design and construction, 

a geotechnical evaluation should be performed as described in Section 6.2.1., to 

evaluate the potential settlement hazard. Mitigation of the potential settlement hazard can be achieved through measures described in Section 6.2.1.

Corrosive Soils 

Potentially corrosive soils may be present along Segment 4, Alternative B. Corrosive soils, especially in areas of shallow groundwater that may exist in portions of 

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Segment 4, Alternative B, can present a corrosion hazard to concrete and metal 

foundations, utilities, and other buried improvements, including the tunnel structures. A more detailed evaluation, as described in Section 6.2.2., should be 

performed during the design phase of the project to evaluate the impacts and risks 

associated with the potential corrosive soil hazard. Mitigation of the potential corrosive soil hazard can be achieved through measures described in Section 6.2.2. 

Expansive Soils 

Potentially expansive soils may be present along Segment 4, Alternative B. The 

relative potential impact of expansive soils in this segment, presented in Table 18, 

is considered moderate. Expansive soils can undergo volumetric changes in response to moisture changes and could cause detrimental damage to improvements, 

including tunnel structures. Accordingly, a more detailed evaluation, as described in 

Section 6.2.3., should be performed during the design phase of the project to evaluate the impacts and risks associated with the potential expansive soil hazard. 

Mitigation of the potential expansive soil hazard can be achieved through measures 

described in Section 6.2.3. 

Landslides

Portions of Segment 4, Alternative B in the Clark Range cross areas of relatively

steep topography, and the relative potential impact of landslides and surficial slope 

failures in this segment, presented in Table 18, is considered high. Landslides can 

cause damage to the rail alignment, foundations, tunnels and other structures that 

are upon or impacted by a landslide, as discussed in Section 4.2.4. The stability of 

natural slopes adjacent to the Alignment and proposed cut slopes, fill slopes and 

rail embankments should be evaluated during the design phase of the project, as described in Section 6.2.4. Mitigation of the potential hazard of landslides and 

surficial slope failures can be achieved through measures described in Section 6.2.4.

Caliche/Hard Rock Excavation/Tunneling 

Caliche layers have not been identified in Segment 4, Alternative B on the geologic 

references reviewed for the study area. Accordingly, the potential for excavation 

difficulties due to caliche is not anticipated to affect Segment 4, Alternative B. 

Based on our review of geologic maps of the Alignment study area, portions of 

Segment 4, Alternative B are underlain by metamorphic gneiss bedrock. Depending 

on the depth of excavation into these materials, moderate to difficult excavation 

may be encountered. Tunneling through the east side of the Clark Mountain Range, 

through this metamorphic gneiss rock unit, is planned for Segment 4, Alternative B. 

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The maps indicated that the planned tunneling will pass through faulted rock. Information regarding conditions of this rock at the locations of the proposed 

tunneling was not available; some information from Caltrans borings nearby this 

area is available. The conditions of this area with regard to aspects of tunneling 

should be evaluated prior to design of the tunnels. 

The relative potential impact of excavation difficulties in this segment, presented in 

Table 18, is considered high, due to proposed tunneling. A more detailed evaluation, as described in Section 6.2.5., should be performed during the design phase of 

the project to evaluate the impacts associated with potential excavation difficulties. 

Mitigation of potential excavation difficulties can be achieved through measures 

described in Section 6.2.5.

Ground Fissures 

Ground fissures have not been identified in Segment 4, Alternative B on the geologic references reviewed for the study area. Accordingly, the potential ground 

fissure hazard discussed in Section 4.2.6., is not anticipated to affect Segment 4, Alternative B. 

Shallow Groundwater 

Although not reported in information reviewed, shallow groundwater may be anticipated along portions of Segment 4, Alternative B, and the relative potential 

impact of shallow groundwater in this segment, presented in Table 18, is considered 

high due to the proposed tunnels. As discussed in Section 4.2.7., shallow groundwater can impact excavations for deep foundations and below ground structures, 

tunnel excavation, as well as the methods and costs of construction. Prior to design 

and construction, a geotechnical engineering evaluation as described in Section 6.2.5., should be undertaken to assess the groundwater conditions along the 

Alignment so that tunneling excavation, foundation systems and earthwork can be 

appropriately designed and constructed. Mitigation of the potential shallow 

groundwater hazard can be achieved through measures described in Section 6.2.5. 

4.3.5. Segment 5 (State Line to Sloan, Nevada) 

4.3.5.1. Operational Period Segment 5, Alternatives A and B 

Surface Fault Rupture 

Based on geologic and seismic maps reviewed, no active faults cross the Alignment 

in Segment 5, Alternatives A and B. Accordingly, the potential surface rupture haz206725001 R Prelim Geo.doc F-J-89 82
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ard discussed in Section 4.1.1. is not anticipated to affect Segment 5, Alternatives A 

and B. 

Ground Shaking 

Due to the proximity to nearby active faults, the potential for strong ground motions to occur along Segment 5, Alternatives A and B, is significant, and the relative 

potential impact of ground shaking in this segment, presented in Table 18, is considered low to high, depending on location; the farther north in this segment 

reduces the relative impact of ground shaking. Based on the information provided 

on Figure 14, peak horizontal ground accelerations on the order of 0.2g to 0.6g 

could be anticipated along this segment in the Ivanpah Valley area, while peak 

horizontal ground accelerations on the order of 0.1g to 0.2g could be anticipated 

along this segment north of the Ivanpah Valley area of this segment. Since this level 

of ground shaking can cause detrimental damage to project improvements, as described in Section 4.1.2, the potential for relatively high seismic accelerations will 

need to be evaluated in the design of the proposed improvements, as described in 

Section 6.1.2. Mitigation of the potential ground shaking hazard can be achieved 

through measures described in Section 6.1.2. 

Liquefaction

Segment 5, Alternatives A and B, cross the Ivanpah Valley, and, although shallow 

groundwater was not indicated in this area in information reviewed, potentially 

shallow groundwater may exist. Soils with a potential for liquefaction may exist in 

this segment, and the relative potential impact of liquefaction in this segment, presented in Table 18, is considered low. Liquefaction could cause significant damage 

to the proposed rail improvements, as discussed in Section 4.1.3. Accordingly, the 

liquefaction potential of the soils should be evaluated during the design phase of 

the project, as described in Section 6.1.3. Mitigation of the potential liquefaction 

hazard can be achieved through measures described in Section 6.1.3. 

Dam Inundation 

Based on information reviewed, the potential for dam inundation to affect Segment 

5, Alternatives A and B is remote. Accordingly, the potential dam inundation hazard 

discussed in Section 4.1.4., is not anticipated to affect Segment 5, Alternatives A 

and B. 

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4.3.5.2. Construction Period Segment 5, Alternatives A and B 

Settlement (Natural Soils and Undocumented Fills) 

As indicated on geologic maps reviewed, the surficial geology of Segment 5, Alternatives A and B, is variable and predominantly includes younger and older alluvial 

deposits overlying Tertiary volcanic and sedimentary rocks and Paleozoic limestone/carbonate rocks. The alluvium may contain compressible layers. Areas of 

previous development exist along this segment, and undocumented fill soils may 

exist. Due to the potential presence of compressible alluvium and undocumented 

fill along this segment, a potential for settlement under load of proposed new improvements exists, and the relative potential impact of settlement of these soils in 

this segment, presented in Table 18, is considered moderate. 

Compressible natural soils and undocumented fills pose the risk of adverse settlement under static loads imposed by new embankment fills, shallow foundations for 

proposed rail system and associated structures. As discussed is Section 4.2.1., differential settlement of soils can cause damage to project improvements including 

concrete structures and foundations, railway alignment, retaining walls, associated 

station and maintenance structures and pavements. Prior to design and construction, 

a geotechnical evaluation should be performed as described in Section 6.2.1., to 

evaluate the potential settlement hazard. Mitigation of the potential settlement hazard can be achieved through measures described in Section 6.2.1. 

Landslides

Much of Segment 5, Alternatives A and B cross areas of relatively gentle to moderate topography, and the relative potential impact of landslides and surficial slope 

failures in this segment, presented in Table 18, is considered moderate. In areas of 

moderate to steep topography, a higher potential for landslides exists. Landslides 

can cause damage to the rail alignment, foundations and other structures that are 

upon or impacted by a landslide, as discussed in Section 4.2.4. Slope areas within 

the project study area, including proposed cut slopes, fill slopes and rail embankments could potentially be affected by surficial slope failures. Accordingly, the 

potential for landslides and surficial slope failures to affect this segment of the project should be evaluated during the design phase of the project, as described in 

Section 6.2.4. Mitigation of the potential hazard of landslides and surficial slope 

failures can be achieved through measures described in Section 6.2.4.

Corrosive Soils 

Potentially corrosive soils may be present along Segment 5, Alternatives A and B. 

Corrosive soils, especially in areas of shallow groundwater that may exist in por206725001 R Prelim Geo.doc F-J-91 84
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tions of Segment 5, Alternatives A and B, can present a corrosion hazard to concrete and metal foundations, utilities, and other buried improvements. A more 

detailed evaluation, as described in Section 6.2.2., should be performed during the 

design phase of the project to evaluate the impacts and risks associated with the potential corrosive soil hazard. Mitigation of the potential corrosive soil hazard can be 

achieved through measures described in Section 6.2.2. 

Expansive Soils 

Potentially expansive soils may be present along Segment 5, Alternatives A and B. 

The relative potential impact of expansive soils in this segment, presented in Table 18, is considered moderate. Expansive soils can undergo volumetric changes in 

response to moisture changes and could cause detrimental damage to improvements. Accordingly, a more detailed evaluation, as described in Section 6.2.3., 

should be performed during the design phase of the project to evaluate the impacts 

and risks associated with the potential expansive soil hazard. Mitigation of the potential expansive soil hazard can be achieved through measures described in 

Section 6.2.3. 

Ground Fissures 

Ground fissures have not been identified in Segment 5, Alternatives A and B on the 

geologic references reviewed for the study area. However, according to information 

reviewed, ground fissures may be present in this part of Nevada. The relative impact of potential ground fissure hazard in this segment, presented in Table 18, is 

considered moderate. Accordingly, a more detailed evaluation, as described in Section 6.2.6., should be performed during the design phase of the project to evaluate 

the impacts and risks associated with the potential ground fissure hazard. Mitigation of the potential expansive ground fissure hazard can be achieved through 

measures described in Section 6.2.6. 

Shallow Groundwater 

Although not reported in information reviewed, shallow groundwater may be anticipated along portions of Segment 5, Alternatives A and B, and the relative 

potential impact of shallow groundwater in this segment, presented in Table 18, is 

considered low. As discussed in Section 4.2.7., shallow groundwater can impact excavations for deep foundations and below ground structures; and can impact ground 

stability, and foundation design of proposed improvements, as well as the methods 

and costs of construction. Prior to design and construction, a geotechnical engineering evaluation as described in Section 6.2.7 should be undertaken to assess the 

groundwater conditions along the Alignment so that earthwork and foundation systems can be appropriately designed and constructed. Mitigation of the potential 

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shallow groundwater hazard can be achieved through measures described in Section 6.2.7.

Caliche/Hard Rock Excavation 

Caliche layers may be present in Segment 5, Alternatives A and B based on the 

geologic references reviewed for the study area, and the relative potential impact 

for excavation difficulties due to caliche in Segment 5, Alternatives A and B, presented in Table 18, is considered moderate. Caliche layers contain calcareous 

cementation which can be moderately hard, hard, and very hard and may range in 

thickness from a few inches to several feet. These soils may be resistant to excavation, and may pose an impact on construction techniques for both shallow and deep 

improvements for the rail system in the Las Vegas Valley and surrounding region. 

Based on our review of geologic maps of the Alignment study area, portions of 

Segment 5, Alternatives A and B are underlain by limestone and volcanic bedrock, 

and other rock types that may be hard. Depending on the depth of excavation into 

these materials, moderate to difficult excavation may be encountered. The relative 

potential impact of excavation difficulties in this segment, presented in Table 18, is 

considered moderate. A more detailed evaluation, as described in Section 6.2.5., 

should be performed during the design phase of the project to evaluate the impacts 

associated with potential excavation difficulties. Mitigation of potential excavation 

difficulties can be achieved through measures described in Section 6.2.5. 

4.3.6. Segment 6 (Sloan to Las Vegas, Nevada) 

4.3.6.1. Operational Period Segment 6, Alternatives A and B 

Surface Rupture 

Based on geologic and seismic maps reviewed, no active faults cross the Alignment 

in Segment 6, Alternatives A and B. Accordingly, the potential surface rupture hazard discussed in Section 4.1.1., is not anticipated to affect Segment 6, 

Alternatives A and B. 

Ground Shaking 

There is a potential for moderately strong ground motions to occur along Segment 6, Alternatives A and B, and the relative potential impact of ground shaking in 

this segment, presented in Table 18, is considered low. Based on the information 

provided on Figure 14, peak horizontal ground accelerations on the order of 0.1g to 

0.2g could be anticipated along this segment. The potential for relatively moderate 

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seismic accelerations will need to be evaluated in the design of the proposed improvements, as described in Section 6.1.2. Mitigation of the potential ground 

shaking hazard can be achieved through measures described in Section 6.1.2. 

Liquefaction

Since Segment 6, Alternatives A and B, travels across the Las Vegas Valley where 

the potential for shallow groundwater (at the north end of the segment) and soils 

with a potential for liquefaction exist, the relative potential impact of liquefaction 

in this segment, presented in Table 18, is considered moderate. Liquefaction could 

cause significant damage to the proposed rail improvements, as discussed in Section 4.1.3. Accordingly, the liquefaction potential of the soils should be evaluated 

during the design phase of the project, as described in Section 6.1.3. Mitigation of 

the potential liquefaction hazard can be achieved through measures described in 

Section 6.1.3.

Dam Inundation 

Based on information reviewed, the potential for dam inundation to affect Segment 6, Alternatives A and B is remote. Accordingly, the potential dam inundation 

hazard discussed in Section 4.1.4. is not anticipated to affect Segment 6, Alternatives A and B. 

4.3.6.2. Construction Period Segment 6, Alternatives A and B 

Settlement (Natural Soils and Undocumented Fills) 

As indicated on geologic maps reviewed, the surficial geology of Segment 6, Alternatives A and B, is variable and predominantly includes younger and older alluvial 

deposits. Some Paleozoic limestone/carbonate rocks are present at the south end of 

this segment. The alluvium may contain compressible layers. Areas of previous development exist along this segment, and undocumented fill soils may exist. Due to 

the potential presence of compressible alluvium and undocumented fill along this 

segment, a potential for settlement under load of proposed new improvements exists, and the relative potential impact of settlement of these soils in this segment, 

presented in Table 18, is considered moderate. 

Compressible natural soils and undocumented fills pose the risk of adverse settlement under static loads imposed by new embankment fills, shallow foundations for 

proposed rail system and associated structures. As discussed is Section 4.2.1., differential settlement of soils can cause damage to project improvements including 

concrete structures and foundations, railway alignment, retaining walls, associated 

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station and maintenance structures and pavements. Prior to design and construction, 

a geotechnical evaluation should be performed as described in Section 6.2.1, to 

evaluate the potential settlement hazard. Mitigation of the potential settlement hazard can be achieved through measures described in Section 6.2.1. 

Corrosive Soils 

Potentially corrosive soils may be present along Segment 6, Alternatives A and B. 

Corrosive soils, especially in areas of shallow groundwater that are reported in portions of Segment 6, Alternatives A and B, can present a corrosion hazard to 

concrete and metal foundations, utilities, and other buried improvements. A more 

detailed evaluation, as described in Section 6.2.2., should be performed during the 

design phase of the project to evaluate the impacts and risks associated with the potential corrosive soil hazard. Mitigation of the potential corrosive soil hazard can be 

achieved through measures described in Section 6.2.2. 

Expansive Soils 

Potentially expansive soils may be present along Segment 6, Alternatives A and B. 

The relative potential impact of expansive soils in this segment, presented in Table 18, is considered moderate. Expansive soils can undergo volumetric changes in 

response to moisture changes and could cause detrimental damage to improvements. Accordingly, a more detailed evaluation, as described in Section 6.2.3., 

should be performed during the design phase of the project to evaluate the impacts 

and risks associated with the potential expansive soil hazard. Mitigation of the potential expansive soil hazard can be achieved through measures described in 

Section 6.2.3.

Landslides

Much of Segment 6, Alternatives A and B travels across areas of relatively gentle 

topography in the Las Vegas Valley, and the relative potential impact of landslides 

and surficial slope failures in this segment, presented in Table 18, is considered 

moderate. In areas of moderate to steep topography, a higher potential for landslides exists. Landslides can cause damage to the rail alignment, foundations and 

other structures that are upon or impacted by a landslide, as discussed in Section 4.2.4. Slope areas within the project study area, including constructed cut 

slopes, fill slopes and rail embankments could potentially be affected by surficial 

slope failures. Accordingly, the potential for landslides and surficial slope failures 

to affect this segment of the project should be evaluated during the design phase of 

the project, as described in Section 6.2.4. Mitigation of the potential hazard of landslides and surficial slope failures can be achieved through measures described in 

Section 6.2.4.

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Caliche/Hard Rock Excavation 

Caliche layers may be present in Segment 6, Alternatives A and B in the Las Vegas 

Valley based on the geologic references reviewed for the study area, and the relative potential impact for excavation difficulties due to caliche in Segment 6, 

Alternatives A and B, presented in Table 18, is considered high. Caliche layers contain calcareous cementation which can be moderately hard, hard, and very hard and 

may range in thickness from a few inches to several feet. These soils may be resistant to excavation, and may pose an impact on construction techniques for both 

shallow and deep improvements for the rail system in the Las Vegas Valley. 

Additionally, the southern portions of Segment 6, Alternatives A and B are underlain by limestone bedrock that may be hard, based on our review of geologic maps 

of the Alignment study area. Depending on the depth of excavation into these materials, moderate to difficult excavation may be encountered. A more detailed 

evaluation, as described in Section 6.2.5., should be performed during the design 

phase of the project to evaluate the impacts associated with potential excavation 

difficulties. Mitigation of potential excavation difficulties can be achieved through 

measures described in Section 6.2.5. 

Ground Fissures 

Ground fissures have been mapped in portions of the Las Vegas Valley in the vicinity of Segment 6, Alternatives A and B on the geologic references reviewed for the 

study area. Accordingly, the relative impact of potential ground fissure hazard in 

this segment, presented in Table 18, is considered high. A more detailed evaluation, 

as described in Section 6.2.6., should be performed during the design phase of the 

project to evaluate the impacts and risks associated with the potential ground fissure hazard. Mitigation of the potential ground fissure hazard can be achieved 

through measures described in Section 6.2.6. 

Shallow Groundwater 

Shallow groundwater may be anticipated along northern portions of Segment 6, Alternatives A and B, and the relative potential impact of shallow groundwater in this 

segment, presented in Table 18, is considered moderate. As discussed in Section 4.2.7., shallow groundwater can impact excavations for deep foundations such 

as for aerial guideways; and can impact ground stability, and foundation design of 

proposed improvements, as well as the methods and costs of construction. Prior to 

design and construction, a geotechnical engineering evaluation as described in Section 6.2.7., should be undertaken to assess the groundwater conditions along the 

Alignment so that earthwork and foundation systems can be appropriately designed 

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and constructed. Mitigation of the potential shallow groundwater hazard can be 

achieved through measures described in Section 6.2.7. 

4.3.6.3. Operational Period Segment 6, Alternatives C and D 

Surface Fault Rupture 

Based on geologic and seismic maps reviewed, no active faults cross the Alignment 

in Segment 6, Alternatives C and D. Accordingly, the potential surface rupture hazard discussed in section 4.1.1. is not anticipated to affect Segment 6, Alternatives C 

and D. 

Ground Shaking 

There is a potential for moderately strong ground motions to occur along Segment 

6, Alternatives C and D, and the relative potential impact of ground shaking in this 

segment, presented in Table 18, is considered low. Based on the information provided on Figure 14, peak horizontal ground accelerations on the order of 0.1g to 

0.2g could be anticipated along this segment. Since this level of ground shaking can 

cause detrimental damage to project improvements, as described in Section 4.1.2., 

the potential for relatively moderate seismic accelerations will need to be evaluated 

in the design of the proposed improvements, as described in Section 6.1.2. Mitigation of the potential ground shaking hazard can be achieved through measures 

described in Section 6.1.2. 

Liquefaction

Since Segment 6, Alternatives C and D, travels across the Las Vegas Valley where 

the potential for shallow groundwater (at the north end of the segment) and soils 

with a potential for liquefaction exist, the relative potential impact of liquefaction 

in this segment, presented in Table 18, is considered moderate. Liquefaction could 

cause significant damage to the proposed rail improvements, as discussed in Section 4.1.3. Accordingly, the liquefaction potential of the soils should be evaluated 

during the design phase of the project, as described in Section 6.1.3. Mitigation of 

the potential liquefaction hazard can be achieved through measures described in 

Section 6.1.3. 

Dam Inundation 

Based on information reviewed, the potential for dam inundation to affect Segment 6, Alternatives C and D is remote. Accordingly, the potential dam inundation 

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hazard discussed in Section 4.1.4. is not anticipated to affect Segment 6, Alternatives A and B. 

4.3.6.4. Construction Period Segment 6, Alternatives C and D 

Settlement (Natural Soils and Undocumented Fills) 

As indicated on geologic maps reviewed, the surficial geology of Segment 6, Alternatives C and D, is variable and predominantly includes younger and older alluvial 

deposits. Some Paleozoic limestone/carbonate rocks are present at the south end of 

this segment. The alluvium may contain compressible layers. Areas of previous development exist along this segment, and undocumented fill soils may exist. Due to 

the potential presence of compressible alluvium and undocumented fill along this 

segment, a potential for settlement under load of proposed new improvements exists, and the relative potential impact of settlement of these soils in this segment, 

presented in Table 18, is considered moderate. 

Compressible natural soils and undocumented fills pose the risk of adverse settlement under static loads imposed by new embankment fills, shallow foundations for 

proposed rail system and associated structures. As discussed is Section 4.2.1., differential settlement of soils can cause damage to project improvements including 

concrete structures and foundations, railway alignment, retaining walls, associated 

station and maintenance structures and pavements. Prior to design and construction, 

a geotechnical evaluation should be performed as described in Section 6.2.1, to 

evaluate the potential settlement hazard. Mitigation of the potential settlement hazard can be achieved through measures described in Section 6.2.1. 

Corrosive Soils 

Potentially corrosive soils may be present along Segment 6, Alternatives C and D. 

Corrosive soils, especially in areas of shallow groundwater that are reported in portions of Segment 6, Alternatives C and D, can present a corrosion hazard to 

concrete and metal foundations, utilities, and other buried improvements. A more 

detailed evaluation, as described in Section 6.2.2., should be performed during the 

design phase of the project to evaluate the impacts and risks associated with the potential corrosive soil hazard. Mitigation of the potential corrosive soil hazard can be 

achieved through measures described in Section 6.2.2. 

Expansive Soils 

Potentially expansive soils may be present along Segment 6, Alternatives C and D. 

The relative potential impact of expansive soils in this segment, presented in Ta206725001 R Prelim Geo.doc F-J-98 91
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ble 18, is considered moderate. Expansive soils can undergo volumetric changes in 

response to moisture changes and could cause detrimental damage to improvements. Accordingly, a more detailed evaluation, as described in Section 6.2.3., 

should be performed during the design phase of the project to evaluate the impacts 

and risks associated with the potential expansive soil hazard. Mitigation of the potential expansive soil hazard can be achieved through measures described in 

Section 6.2.3. 

Landslides and Surficial Slope Failures 

Much of Segment 6, Alternatives C and D travels across areas of relatively gentle 

topography in the Las Vegas Valley, except for a hilly area at the south end of the 

segment, and the relative potential impact of landslides and surficial slope failures 

in this segment, presented in Table 18, is considered moderate. In areas of moderate 

to steep topography, a higher potential for landslides exists. Landslides can cause 

damage to the rail alignment, foundations and other structures that are upon or impacted by a landslide, as discussed in Section 4.2.4. Slope areas within the project 

study area, including proposed cut slopes, fill slopes and rail embankments should 

be evaluated during the design phase of the project, as described in Section 6.2.4. 

Mitigation of the potential hazard of landslides and surficial slope failures can be 

achieved through measures described in Section 6.2.4.

Caliche/Hard Rock Excavation 

Caliche layers may be present in Segment 6, Alternatives C and D in the Las Vegas 

Valley based on the geologic references reviewed for the study area, and the relative potential impact for excavation difficulties due to caliche in Segment 6, 

Alternatives C and D, presented in Table 18, is considered high. Caliche layers contain calcareous cementation which can be moderately hard, hard, and very hard and 

may range in thickness from a few inches to several feet. These soils may be resistant to excavation, and may pose an impact on construction techniques for both 

shallow and deep improvements for the rail system in the Las Vegas Valley. 

Additionally, the southern portions of Segment 6, Alternatives C and D are underlain by limestone bedrock that may be hard, based on our review of geologic maps 

of the Alignment study area. Depending on the depth of excavation into these materials, moderate to difficult excavation may be encountered. A more detailed 

evaluation, as described in Section 6.2.5., should be performed during the design 

phase of the project to evaluate the impacts associated with potential excavation 

difficulties. Mitigation of potential excavation difficulties can be achieved through 

measures described in Section 6.2.5. 

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Ground Fissures 

Ground fissures have been mapped in portions of the Las Vegas Valley in the vicinity of Segment 6, Alternatives C and D on the geologic references reviewed for the 

study area. Accordingly, the relative impact of potential ground fissure hazard in 

this segment, presented in Table 18, is considered high. A more detailed evaluation, 

as described in Section 6.2.6., should be performed during the design phase of the 

project to evaluate the impacts and risks associated with the potential ground fissure hazard. Mitigation of the potential ground fissure hazard can be achieved 

through measures described in Section 6.2.6. 

Shallow Groundwater 

Shallow groundwater may be anticipated along northern portions of Segment 6, Alternatives C and D, and the relative potential impact of shallow groundwater in this 

segment, presented in Table 18, is considered moderate. As discussed in Section 4.2.7., shallow groundwater can impact excavations for deep foundations, and 

other deep structures; and can impact ground stability, and foundation design of 

proposed improvements, as well as the methods and costs of construction. Prior to 

design and construction, a geotechnical engineering evaluation as described in Section 6.2.7., should be undertaken to assess the groundwater conditions along the 

Alignment so that earthwork and foundation systems can be appropriately designed 

and constructed. Mitigation of the potential shallow groundwater hazard can be 

achieved through measures described in Section 6.2.7. 

4.3.7. Segment 7 (City of Las Vegas, Nevada) 

4.3.7.1. Operational Period Segment 7, Alternatives A and B 

Surface Fault Rupture 

Based on geologic and seismic maps reviewed, no active faults cross the Alignment 

in Segment 7, Alternatives A and B. Accordingly, the potential surface fault rupture 

hazard discussed in Section 4.1.1 is not anticipated to affect Segment 7, Alternatives A and B. 

Ground Shaking 

There is a potential for moderately strong ground motions to occur along Segment 

7, Alternatives A and B, and the relative potential impact of ground shaking in this 

segment, presented in Table 18, is considered low. Based on the information provided on Figure 14, peak horizontal ground accelerations on the order of 0.1g to 

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0.2g could be anticipated along this segment. The potential for relatively moderate 

seismic accelerations will need to be evaluated in the design of the proposed improvements, as described in Section 6.1.2. Mitigation of the potential ground 

shaking hazard can be achieved through measures described in Section 6.1.2. 

Liquefaction

Since Segment 7, Alternatives A and B, travels across the Las Vegas Valley where 

the potential for shallow groundwater underlying the segment and soils with a potential for liquefaction exist, the relative potential impact of liquefaction in this 

segment, presented in Table 18, is considered moderate. Liquefaction could cause 

significant damage to the proposed rail improvements, as discussed in Section 4.1.3. Accordingly, the liquefaction potential of the soils should be evaluated 

during the design phase of the project, as described in Section 6.1.3. Mitigation of 

the potential liquefaction hazard can be achieved through measures described in 

Section 6.1.3. 

Dam Inundation 

Based on information reviewed, the potential for dam inundation to affect Segment 

7, Alternatives A and B is remote. Accordingly, the potential dam inundation hazard 

discussed in section 4.1.4., is not anticipated to affect Segment 7, Alternatives A 

and B. 

4.3.7.2. Construction Period Segment 7, Alternatives A and B 

Settlement (Natural Soils and Undocumented Fills) 

As indicated on geologic maps reviewed, the surficial geology of Segment 7, Alternatives A and B, is variable and predominantly includes younger and older alluvial 

deposits. The alluvium may contain compressible layers. Areas of previous development exist along this segment, and undocumented fill soils may exist. Due to the 

potential presence of compressible alluvium and undocumented fill along this segment, a potential for settlement under load of proposed new improvements exists, 

and the relative potential impact of settlement of these soils in this segment, presented in Table 18, is considered moderate. 

Compressible natural soils and undocumented fills pose the risk of adverse settlement under static loads imposed by new embankment fills, shallow foundations for 

proposed rail system and associated structures. As discussed is Section 4.2.1., differential settlement of soils can cause damage to project improvements including 

concrete structures and foundations, railway alignment, retaining walls, associated 

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station and maintenance structures and pavements. Prior to design and construction, 

a geotechnical evaluation should be performed as described in Section 6.2.1., to 

evaluate the potential settlement hazard. Mitigation of the potential settlement hazard can be achieved through measures described in Section 6.2.1. 

Corrosive Soils 

Potentially corrosive soils may be present along Segment 7, Alternatives A and B. 

Corrosive soils, especially in areas of shallow groundwater that are reported in portions of Segment 7, Alternatives A and B, can present a corrosion hazard to 

concrete and metal foundations, utilities, and other buried improvements. A more 

detailed evaluation, as described in Section 4.2.2., should be performed during the 

design phase of the project to evaluate the impacts and risks associated with the potential corrosive soil hazard. Mitigation of the potential corrosive soil hazard can be 

achieved through measures described in Section 6.2.2. 

Expansive Soils 

Potentially expansive soils may be present along Segment 7, Alternatives A and B. 

The relative potential impact of expansive soils in this segment, presented in Table 18, is considered moderate. Expansive soils can undergo volumetric changes in 

response to moisture changes and could cause detrimental damage to improvements. Accordingly, a more detailed evaluation, as described in Section 6.2.3., 

should be performed during the design phase of the project to evaluate the impacts 

and risks associated with the potential expansive soil hazard. Mitigation of the potential expansive soil hazard can be achieved through measures described in 

Section 6.2.3. 

Landslides

Segment 7, Alternatives A and B travel across areas of relatively gentle topography 

in the Las Vegas Valley, and the relative potential impact of landslides and surficial 

slope failures in this segment, presented in Table 18, is considered low. Stability 

analysis of proposed cut slopes, fill slopes and rail embankments should be performed during the design phase of the project, as described in Section 6.2.4. 

Mitigation of the potential hazard of landslides and surficial slope failures can be 

achieved through measures described in Section 6.2.4.

Caliche/Hard Rock Excavation 

Caliche layers may be present in Segment 7, Alternatives A and B in the Las Vegas 

Valley based on the geologic references reviewed for the study area, and the rela206725001 R Prelim Geo.doc F-J-102 95
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tive potential impact for excavation difficulties due to caliche in Segment 7, Alternatives A and B, presented in Table 18, is considered high. Caliche layers contain 

calcareous cementation which can be moderately hard, hard, and very hard and may 

range in thickness from a few inches to several feet. These soils may be resistant to 

excavation, and may pose an impact on construction techniques for both shallow 

and deep improvements for the rail system in the Las Vegas Valley. 

Depending on the depth of excavation into these materials, moderate to difficult 

excavation may be encountered. A more detailed evaluation, as described in Section 6.2.5., should be performed during the design phase of the project to evaluate 

the impacts associated with potential excavation difficulties. Mitigation of potential 

excavation difficulties can be achieved through measures described in Section 6.2.5. 

Ground Fissures 

Ground fissures have been mapped in portions of the Las Vegas Valley in the vicinity of Segment 7, Alternatives A and B on the geologic references reviewed for the 

study area. Accordingly, the relative impact of potential ground fissure hazard in 

this segment, presented in Table 18, is considered high. A more detailed evaluation, 

as described in Section 6.2.6., should be performed during the design phase of the 

project to evaluate the impacts and risks associated with the potential ground fissure hazard. Mitigation of the potential ground fissure hazard can be achieved 

through measures described in Section 6.2.6. 

Shallow Groundwater 

Shallow groundwater may be anticipated along Segment 7, Alternatives A and B, 

and the relative potential impact of shallow groundwater in this segment, presented 

in Table 18, is considered moderate. As discussed in Section 4.2.7., shallow 

groundwater can impact excavations for deep foundations such as for aerial guideways; and can impact ground stability, and foundation design of proposed 

improvements, as well as the methods and costs of construction. Prior to design and 

construction, a geotechnical engineering evaluation as described in Section 6.2.7., 

should be undertaken to assess the groundwater conditions along the Alignment so 

that earthwork and foundation systems can be appropriately designed and constructed. Mitigation of the potential shallow groundwater hazard can be achieved 

through measures described in Section 6.2.7. 

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4.3.7.3. Operational Period Segment 7, Alternative C 

Surface Fault Rupture 

Based on geologic and seismic maps reviewed, no active faults cross the Alignment 

in Segment 7, Alternative C. Accordingly, the potential surface rupture hazard discussed in Section 4.1.1. is not anticipated to affect Segment 7, Alternative C. 

Ground Shaking 

There is a potential for moderately strong ground motions to occur along Segment 7, Alternative C, and the relative potential impact of ground shaking in this 

segment, presented in Table 18, is considered low. Based on the information provided on Figure 14, peak horizontal ground accelerations on the order of 0.1g to 

0.2g could be anticipated along this segment. The potential for relatively moderate 

seismic accelerations will need to be evaluated in the design of the proposed improvements, as described in Section 6.1.2. Mitigation of the potential ground 

shaking hazard can be achieved through measures described in Section 6.1.2. 

Liquefaction

Since Segment 7, Alternative C, travels across the Las Vegas Valley where the potential for shallow groundwater (at the north end of the segment) and soils with a 

potential for liquefaction exist, the relative potential impact of liquefaction in this 

segment, presented in Table 18, is considered moderate. Liquefaction could cause 

significant damage to the proposed rail improvements, as discussed in Section 4.1.3. Accordingly, the liquefaction potential of the soils should be evaluated 

during the design phase of the project, as described in Section 6.1.3. Mitigation of 

the potential liquefaction hazard can be achieved through measures described in 

Section 6.1.3.

Dam Inundation 

Based on information reviewed, the potential for dam inundation to affect Segment 7, Alternative C is remote. Accordingly, the potential dam inundation hazard 

discussed in Section 4.1.4., is not anticipated to affect Segment 7, Alternative C. 

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4.3.7.4. Construction Period Segment 7, Alternative C 

Settlement (Natural Soils and Undocumented Fills) 

As indicated on geologic maps reviewed, the surficial geology of Segment 7, Alternative C is variable and predominantly includes younger and older alluvial 

deposits. The alluvium may contain compressible layers. Areas of previous development exist along this segment, and undocumented fill soils may exist. Due to the 

potential presence of compressible alluvium and undocumented fill along this segment, a potential for settlement under load of proposed new improvements exists, 

and the relative potential impact of settlement of these soils in this segment, presented in Table 18, is considered moderate. 

Compressible natural soils and undocumented fills pose the risk of adverse settlement under static loads imposed by new embankment fills, shallow foundations for 

proposed rail system and associated structures. As discussed is Section 4.2.1., differential settlement of soils can cause damage to project improvements including 

concrete structures and foundations, railway alignment, retaining walls, associated 

station and maintenance structures and pavements. Prior to design and construction, 

a geotechnical evaluation should be performed as described in Section 6.2.1, to 

evaluate the potential settlement hazard. Mitigation of the potential settlement hazard can be achieved through measures described in Section 6.2.1. 

Landslides and Surficial Slope Failures 

Much of Segment 7, Alternative C travels across areas of relatively gentle topography in the Las Vegas Valley, and the relative potential impact of landslides and 

surficial slope failures in this segment, presented in Table 18, is considered low. 

Stability analysis of slope areas within the project study area, including proposed 

cut slopes, fill slopes and rail embankments should be evaluated during the design 

phase of the project, as described in Section 6.2.4. Mitigation of the potential hazard of landslides and surficial slope failures can be achieved through measures 

described in Section 6.2.4.

Corrosive Soils 

Potentially corrosive soils may be present along Segment 7, Alternative C. Corrosive soils, especially in areas of shallow groundwater that are reported in portions 

of Segment 7, Alternative C, can present a corrosion hazard to concrete and metal 

foundations, utilities, and other buried improvements. A more detailed evaluation, 

as described in Section 6.2.2., should be performed during the design phase of the 

project to evaluate the impacts and risks associated with the potential corrosive soil 

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hazard. Mitigation of the potential corrosive soil hazard can be achieved through 

measures described in Section 6.2.2. 

Expansive Soils 

Potentially expansive soils may be present along Segment 7, Alternative C. The 

relative potential impact of expansive soils in this segment, presented in Table 18, 

is considered moderate. Expansive soils can undergo volumetric changes in response to moisture changes and could cause detrimental damage to improvements. 

Accordingly, a more detailed evaluation, as described in Section 6.2.3., should be 

performed during the design phase of the project to evaluate the impacts and risks 

associated with the potential expansive soil hazard. Mitigation of the potential expansive soil hazard can be achieved through measures described in Section 6.2.3. 

Caliche/Hard Rock Excavation 

Caliche layers may be present in Segment 7, Alternative C in the Las Vegas Valley 

based on the geologic references reviewed for the study area, and the relative potential impact for excavation difficulties due to caliche in Segment 7, Alternative C, 

presented in Table 18, is considered high. Caliche layers contain calcareous cementation which can be moderately hard, hard, and very hard and may range in 

thickness from a few inches to several feet. These soils may be resistant to excavation, and may pose an impact on construction techniques for both shallow and deep 

improvements for the rail system in the Las Vegas Valley. 

Depending on the depth of excavation into these materials, moderate to difficult 

excavation may be encountered. A more detailed evaluation, as described in Section 6.2.5., should be performed during the design phase of the project to evaluate 

the impacts associated with potential excavation difficulties. Mitigation of potential 

excavation difficulties can be achieved through measures described in Section 6.2.5. 

Ground Fissures 

Ground fissures have been mapped in portions of the Las Vegas Valley in the vicinity of Segment 7, Alternative C on the geologic references reviewed for the study 

area. Accordingly, the relative impact of potential ground fissure hazard in this 

segment, presented in Table 18, is considered high. A more detailed evaluation, as 

described in Section 6.2.6., should be performed during the design phase of the project to evaluate the impacts and risks associated with the potential ground fissure 

hazard. Mitigation of the potential ground fissure hazard can be achieved through 

measures described in Section 6.2.6. 

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Shallow Groundwater 

Shallow groundwater may be anticipated along northern portions of Segment 7, Alternative C, and the relative potential impact of shallow groundwater in this 

segment, presented in Table 18, is considered moderate. As discussed in Section 4.2.7., shallow groundwater can impact excavations for deep foundations, and 

other deep structures; and can impact ground stability, and foundation design of 

proposed improvements, as well as the methods and costs of construction. Prior to 

design and construction, a geotechnical engineering evaluation as described in Section 6.2.7 should be undertaken to assess the groundwater conditions along the 

Alignment so that earthwork and foundation systems can be appropriately designed 

and constructed. Mitigation of the potential shallow groundwater hazard can be 

achieved through measures described in Section 6.2.7.

5. RELATIVE EFFECTS OF ENVIRONMENTAL CONSEQUENCES 

The DesertXpress alternatives cross differing terrain and geologic environments that include a 

variety of potential seismic and geologic hazards. The following Table 18 summarizes the relative potential impacts for the alternative segments. A ratings system has been established in 

which the seismic and geologic consequences have been categorized by relative impact. A rating 

of 1 represents a relativity high potential impact, a rating of 2 represents a relatively moderate 

impact, and a rating of 3 represents a relatively low potential impact. 

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Table 18 – Relative Effects of Environmental Consequences 

Potential Geotechnical Consequence 

Surface Fault 

Rupture1

Ground 

Shaking2

Liquefaction3

Dam

Inundation4

Settlement/

(Natural & Fill 

Soils) 5

Corrosive Soils6

Expansive Soils7

Landslides8

Excavation9 Segment Alternative

Ground 

Fissures10

Shallow

Groundwater11

1A 2 1 1 2 2 2 1 3 2 3 1

1B 1 1 2 3 2 2 2 2 2 3 3

2A 1 1 1 2 2 2 1 2 2 3 1

2B 3 1 1 2 2 2 1 3 2 3 1

3A and B 

(southwest of Baker) 1 1 to 2 1 to 2 2 to 3 2 2 2 2 2 3 1 to 2 

3A and B 

(northeast of Baker) 3 2 1 to 2 3 2 2 2 2 2 3 1 to 3

4A 3 1 to 2 3 3 2 2 2 2 2 3 3

4B 3 1 to 2 3 3 2 2 2 1 1 3 3

5A and B 3 1 to 3 3 3 2 2 2 2 2 2 36A and B 3 3 2 3 2 2 2 3 1 1 26C and D 3 3 2 3 2 2 2 2 1 1 27A and B 3 3 2 3 2 2 2 3 1 1 2

7C 3 3 2 3 2 2 2 3 1 1 2

Notes:1 Rating 1 = Route crosses active fault or very close to an active fault; Rating 2 = Route crosses potentially active fault; Rating 3 = Route crosses inactive fault or does not cross any known fault. 2 Rating 1 = Estimated peak horizontal ground acceleration (PGA) of 0.4g to 0.6g; Rating 2 = Estimated PGA of 0.2g to 0.4g; Rating 3 = Estimated PGA of 0.1g to 0.2g. 3 Rating 1 = Areas of known, reported shallow groundwater and potentially liquefiable soils; Rating 2 = Areas of potentially shallow groundwater and potentially liquefiable soils; Rating 3 = Areas with no reported 

shallow groundwater and with potentially liquefiable soils. 4 Rating 1 = Areas of reported dam inundation; Rating 2 = Areas near reported potential dam inundation; Rating 3 = Areas with no reported potential for dam inundation. 5 Rating 1 = Areas of reported compressible/collapsible soils; Rating 2 = Areas with potential for compressible/collapsible soils; Rating 3 = Areas with no potential for compressible/collapsible soils. 6 Rating 1 = Areas of reported corrosive soils; Rating 2 = Areas with potential for corrosive soils; Rating 3 = Areas with no potential for corrosive soils. 7 Rating 1 = Areas of mapped clay units or known expansive soils; Rating 2 = Areas with potential for expansive soils; Rating 3 = Areas with no potential for expansive soils. 8 Rating 1 = Areas of known steep terrain with relatively higher potential landslide hazard; Rating 2 = Areas of potential landslide hazard; Rating 3 = Areas of little potential landslide hazard. 9 Rating 1 = Areas of reported hard rock or caliche with anticipated difficult excavation; Rating 2 = Areas of potentially difficult excavation; Rating 3 = Areas of no potential difficult excavations. 

10 Rating 1 = Areas of known, reported ground fissures in site vicinity; Rating 2 = Areas with potential for ground fissures; Rating 3 = Areas with no reported ground fissures. 11 Rating 1 = Areas of known, reported shallow groundwater; Rating 2 = Areas of potentially shallow groundwater; Rating 3 = Areas with no reported shallow groundwater.

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6. MITIGATION MEASURES 

A summary of mitigation measures for the potential environmental consequences related to geotechnical considerations for the proposed DesertXpress rail line is presented below. Additional 

evaluation of the potential geotechnical hazards and consequences discussed in this report could 

include geologic site reconnaissance, subsurface exploration and laboratory testing. Based on the 

findings from site evaluations, appropriate site specific recommendations and mitigation measures for the potential hazards and considerations can be provided.

6.1. Operational Mitigation Measures 

6.1.1. Surface Fault Rupture 

The regional effects and environmental consequences of potential surface fault rupture 

of active faults have been discussed in Section 4.1.1., and the consequences of surface 

fault rupture for each segment of the Alignment have been discussed in Section 4.3. To 

further evaluate the fault-rupture hazard along the proposed segments, surface reconnaissance and subsurface evaluation could be performed. Evaluation of fault-rupture 

hazard should be performed prior to design and construction so that, in the event a faultrupture hazard exists, mitigation techniques can be implemented. Mitigation measures 

for potential fault rupture hazard would typically include locating rail system features 

away from the fault, designing for an acceptable amount of movement, or implementing 

systems to maintain safety and allow for displacement that could be repaired to make 

the system operational. 

Surface reconnaissance to evaluate potential surface fault rupture would include visual 

observation of the earth units and geomorphology, and checking of geologic maps in 

order to map the estimated location and condition of faults relative to the Alignment. 

Ground features that may indicate the location of active faults may be concealed by 

natural soils, fill soils or manmade improvements, and surface reconnaissance may not 

be adequate to locate faults with potential for surface rupture. Consequently, subsurface 

exploration may be needed to evaluate fault locations and conditions. Subsurface 

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evaluation might include the excavation and detailed logging of exploratory trenches 

and/or borings, geophysical studies such as high resolution seismic reflection, seismic 

refraction, ground penetrating radar, gravity and/or magnetic profiling or other applicable methods. 

Public transportation systems throughout California and Nevada cross active faults. 

With the prevalence of active faulting in this seismically active region, the crossing of 

active faults is unavoidable. In this regard, mitigation of the surface fault hazard in 

some areas of the Alignment may not involve avoiding the fault, but would involve designing the system for the anticipated displacement, avoiding as much damage as 

possible while providing for the safety of passengers. 

Mitigation measures for potential fault-rupture hazard could include various techniques. 

Foundations for bridges and elevated guideways, shallow rail system foundations, and 

foundations for stations or other structures can be located away from the fault trace to 

avoid the fault. Locating rail improvements a sufficient distance from active faults 

would limit damage to the system as long as the fault ruptures along the identified surface and does not rupture a new surface. Locating these improvements away from the 

fault or designing for the anticipated displacement may minimize damage to the system 

and non-operational time. 

Measures could also be implemented to reduce the impact from surface rupture while 

the train is in operation. For instance, a monitoring system could be designed to monitor 

seismic activity in the region and provide advanced early warning of a seismic event. 

The monitoring system could be designed so that when strong ground shaking occurs 

beyond a pre-selected level, a signal could immediately be transmitted to the operating 

system to allow time for the train to stop. A system such as this could significantly reduce the length of time the train is in motion during a large seismic event, thus reducing 

the potential for derailment as a result of ground displacement caused by surface rupture.

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6.1.2. Ground Shaking 

The regional effects and environmental consequences of potential seismic ground shaking has been discussed in Section 4.1.2., and the consequences of ground shaking for 

each segment of the Alignment have been discussed in Section 4.3. Site-specific evaluation of the potential ground shaking hazard should be performed prior to design and 

construction so that appropriate structural design and mitigation techniques can be implemented. Site-specific geotechnical evaluations to assess the characteristics of the onsite soils with regard to ground shaking would include drilling of exploratory borings 

and laboratory testing of soils. Site-specific evaluation of the potential ground shaking 

hazard would also involve computer software evaluation to develop seismic design parameters for use by the project structural engineer. 

Mitigation of the potential impacts of seismic ground shaking can be achieved through 

project design, construction, and maintenance. During the final design phase, sitespecific geotechnical evaluations will be performed to obtain detailed subsurface soil 

and geological data, including the site-specific ground motion anticipated for the site. 

Structural elements of the rail system can then be designed to resist or accommodate 

appropriate site-specific ground motions and to conform to the current seismic design 

standards. In addition, implementation of an earthquake early warning system as described in the previous section could be used to reduce the potential impact of strong 

ground shaking. 

6.1.3. Liquefaction

The regional effects and environmental consequences of potential liquefaction have 

been discussed in Section 4.1.3., and the consequences of liquefaction for each segment 

of the Alignment have been discussed in Section 4.3. To further evaluate the potential 

liquefaction hazard along the proposed segment subsurface evaluation could be performed. Site-specific evaluation of the potential liquefaction hazard should be 

performed prior to design and construction so that, in the event a liquefaction hazard exists, appropriate structural design and mitigation techniques can be implemented. 

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Site-specific geotechnical evaluations to assess the liquefaction and dynamic settlement 

characteristics of the on-site soils would include drilling of exploratory borings, evaluation of groundwater depths, and laboratory testing of soils. 

Mitigation for liquefaction may include in-situ ground modification, removal of liquefiable layers and replacement with compacted fill, or support of piles at depths designed 

specifically for liquefaction. Pile foundations can be designed for liquefaction hazard by 

supporting the piles in dense soil or bedrock below the liquefiable zone or other appropriate methods as evaluated during the site-specific evaluation. Additional mitigation 

measures for liquefaction may include densification by installation of stone columns, 

vibration, deep dynamic compaction, and/or compaction grouting. 

6.1.4. Dam Inundation 

The regional effects and environmental consequences of potential dam inundation along 

the Mojave River have been discussed in Section 4.1.5., and the consequences of dam 

inundation for each segment of the Alignment have been discussed in Section 4.3. To 

further evaluate the potential for dam inundation to occur along the proposed segments, 

detailed hydrologic evaluation could be performed to assess the risks and potential effects of inundation to the Alignment. Evaluation of potential dam inundation hazard at 

site-specific locations could be performed prior to design and construction so that, in the 

event of dam inundation, measures could be in place to mitigate the effects. 

Measures to mitigate the potential dam inundation could include raising the elevation of 

the railway at needed locations to keep the tracks above the inundation level, and/or 

construction of levees or walls to prevent inundation from reaching the tracks. The inundation effects are anticipated to be temporary, and may necessitate minor 

maintenance in the affected segments to make the rail system operational. 

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6.2. Construction Mitigation Measures 

6.2.1. Settlement (Natural Soils and Undocumented Fill) 

The regional effects and environmental consequences of settlement (of both natural 

soils and undocumented fill) have been discussed in Section 4.2.1., and the consequences of settlement for each segment of the Alignment have been discussed in 

Section 4.3. To further evaluate the potential for settlement along the proposed segments, surface reconnaissance and subsurface evaluation could be performed. 

Evaluation of the potential settlement hazard should be performed prior to design and 

construction so that, in the event the hazard exists, mitigation techniques can be implemented. 

During the design phase of the project, site-specific geotechnical evaluations would be 

performed to assess the settlement potential of the on-site natural soils and undocumented fill. This would include drilling of exploratory borings and laboratory testing of 

soils, in addition to surface reconnaissance to evaluate site conditions. 

Examples of possible mitigation measures for soils with potential for settlement include 

removal of the compressible/collapsible soil layers and replacement with compacted 

fill; surcharging to induce settlement prior to construction of improvements; allowing 

for a settlement period after or during construction; and specialized foundation design 

including the use of deep foundation systems to support structures. A variety of in-situ 

soil improvement techniques are also available, such as dynamic compaction (heavy 

tamping) or compaction grouting. 

6.2.2. Corrosive Soils 

The regional effects and environmental consequences of potential corrosive soils have 

been discussed in Section 4.2.2., and the consequences of corrosive soils for each segment of the Alignment have been discussed in Section 4.3. To further evaluate the 

potential for corrosive soils along the proposed segments, subsurface evaluation including laboratory testing could be performed. Evaluation of the potential corrosive soils 

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hazard should be performed prior to design and construction so that, in the event the 

hazard exists, mitigation techniques can be implemented. 

Evaluation of the corrosive soil potential can be accomplished by testing and analysis of 

soils at design depths. The laboratory tests conducted on the soils prior to construction 

and improvement plan preparation should include corrosivity tests to evaluate the corrosivity of the subsurface soils. Review of these data by a corrosion engineer would result 

in corrosion protection measures suitable to the project elements. 

Mitigation of corrosive soil conditions may involve the use of concrete resistant to sulfate exposure. Corrosion protection for metals may be needed for underground 

structures in areas where corrosive groundwater or soil could potentially cause deterioration. Typical mitigation measures include epoxy and metallic protective coatings, the 

use of alternative (corrosion resistant) materials, and selection of the appropriate type of 

cement and water/cement ratio. Specific measures to mitigate the potential effects of 

corrosive soils will be developed in the design phase. 

6.2.3. Expansive Soils 

The regional effects and environmental consequences of potential expansive soils have 

been discussed in Section 4.2.3., and the consequences of expansive soils for each segment of the Alignment have been discussed in Section 4.3. To further evaluate the 

potential for expansive soils along the proposed segments, subsurface evaluation including laboratory testing could be performed. Evaluation of the potential expansive soils 

hazard should be performed prior to design and construction so that, in the event the 

hazard exists, mitigation techniques can be implemented. 

Site-specific, subsurface evaluation would be conducted during the design phase of the 

project to evaluate the extent of which expansive soils are present along the alternative 

segments. Where expansive soil conditions are found to occur and are considered detrimental to proposed improvements, mitigation measures can be implemented. 

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Mitigation measures for expansive soils would typically include techniques such as 

overexcavation and replacement with non-expansive soil, chemical treatment (e.g., lime 

or cement), moisture control, and/or specific structural design for expansive soil conditions will be developed during design of the segment. 

6.2.4. Landslides

The regional effects and environmental consequences of potential landslides and surficial slope failures have been discussed in Section 4.2.4., and the consequences of 

landslides and surficial slope failures for each segment of the Alignment have been discussed in Section 4.3. To further evaluate the potential for landslides and surficial slope 

failures along the proposed segments, surface reconnaissance and subsurface evaluation 

could be performed. Evaluation of the landslide and surficial slope failure hazard should 

be performed prior to design and construction so that, in the event the hazard exists, 

mitigation techniques can be implemented. 

Surface reconnaissance to evaluate potential for landslides and surficial slope failures 

would be performed in the design phase and would include visual observation of the 

earth units and geomorphology, and checking of geologic maps in order to evaluate the 

condition of slopes relative to the Alignment. Subsurface exploration may be needed to 

evaluate the potential of slopes for landslides and surficial slope failures. Subsurface 

evaluation might include the excavation and detailed logging of exploratory trenches, 

test pits and/or borings. Slope stability computer analyses may be performed to address 

the stability of slopes in the project area. 

Measures to mitigate potentially unstable slope conditions and mitigate the potential for 

landslides and surficial slope failures include: excavating potentially unstable material 

resulting in a flatter more stable slope configuration; construction of buttress and/or stabilization fills; construction of retaining walls; installation of rock bolts on the face of 

the slope, installation of protective wire mesh on the slope face, and/or the construction 

of debris impact walls at the toe of the slope to contain rock fall debris. 

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6.2.5. Caliche/Hard Rock Excavations 

The regional effects and environmental consequences of potential caliche/hard rock presenting excavation difficulties during construction have been discussed in 

Section 4.2.5., and the consequences of caliche/hard rock during construction for each 

segment of the Alignment have been discussed in Section 4.3. To further evaluate the 

potential for caliche/hard rock during construction along the proposed segments, surface 

reconnaissance and subsurface evaluation could be performed. Evaluation of the potential for caliche/hard excavation should be performed prior to design and construction so 

that, in the event the condition exists, mitigation techniques can be implemented. 

During the design phase of the project, site-specific geotechnical evaluations would be 

performed to assess the excavatibility of the earth units. This may include drilling of 

exploratory borings and/or test pits to evaluate ground conditions for excavation capability. 

Mitigation for caliche and other hard rock excavation may involve several techniques. 

Rock excavation may involve equipment such as a rock-saw, trencher, or heavy-duty 

Hoe-ram. Blasting may also be involved for very hard conditions. The use of blasting or 

breakers, if required, will produce temporary noise and dust hazards, which will need to 

be appropriately addressed during construction. 

6.2.6. Ground Fissures 

The regional effects and environmental consequences of potential ground fissures have 

been discussed in Section 4.2.6., and the consequences of ground fissures for each segment of the Alignment have been discussed in Section 4.3. To further evaluate the 

potential for ground fissures along the proposed segments, surface reconnaissance could 

be performed. Evaluation of the potential ground fissure hazard should be performed 

prior to design and construction so that, in the event the hazard exists, mitigation techniques can be implemented. 

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Surface reconnaissance to evaluate potential for ground fissures would be performed in 

the design phase and would include visual observation of the earth units, manmade features and geomorphology, and checking of geologic maps in order to evaluate the 

surface conditions relative to the Alignment. 

Where ground fissures are found to occur and are considered detrimental to proposed 

improvements, mitigation measures such as overexcavation of the soils and replacement 

with compacted fill, chemical or compaction grouting, or other in-situ soil improvement 

techniques could be performed. 

6.2.7. Shallow Groundwater 

The regional effects and environmental consequences of shallow groundwater have 

been discussed in Section 4.2.7., and the consequences of shallow groundwater for each 

segment of the Alignment have been discussed in Section 4.3. To further evaluate the 

potential for shallow groundwater along the proposed segments at locations where 

groundwater may affect construction, subsurface evaluation could be performed. 

Evaluation of the potential shallow groundwater hazard should be performed prior to 

design and construction so that, in the event the hazard exists, mitigation techniques can 

be implemented. 

Site-specific geotechnical evaluations to assess the groundwater characteristics would

include drilling of exploratory borings, evaluation of groundwater depths, and possible 

installation of groundwater monitoring wells, where needed. 

Measures to mitigate potential shallow groundwater conditions would include: shoring/casing of excavations below the groundwater table; pumping groundwater from 

excavations to keep levels below a specified depth; using dewatering wells to pump 

groundwater out of the ground and lower the groundwater table at specified locations; 

and, where needed, utilizing more advanced, and costly techniques to control groundwater such as the use of subsurface grout curtains or soil/cement walls. 

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Excavations for the underground structures will need to be performed with care to reduce the potential for lateral deflection of excavation sidewalls and/or shoring, which 

could also cause differential movement of structures located near the excavation. To reduce the potential for damage to improvements and structures resulting from dewatering 

operations, the ground surface and/or structures around the excavation could be monitored for movement with a variety of instrumentation. If, during the course of 

construction, the instrumentation detects ground movement that exceeds a pre-specified 

value, the work would stop and the contractor’s methods would be reviewed and appropriate changes would be made, if needed. Typical monitoring methods include 

installation of ground survey points around the outside of the excavation to monitor settlement and/or placing monitoring points on nearby structures to monitor performance 

of the structures. Additionally, inclinometers could be installed along the sides of the 

excavation to monitor lateral deflection of the sidewalls during excavation. 

7. LIMITATIONS

The geotechnical evaluation presented in this report has 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 other warranty, implied or expressed, is 

made regarding the conclusions, recommendations, and professional opinions expressed in this 

report. Our preliminary conclusions and recommendations are based on a review of readily 

available geotechnical background literature. Variations in the geotechnical conditions of the 

Alignment study area may exist and conditions not described in this report may be encountered. 

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

Alignment study area using readily available data and to provide a preliminary geotechnical report which can be utilized in the preparation of planning and environmental impact documents 

for the project. A more detailed geologic evaluation, including subsurface exploration and laboratory testing, should be performed prior to design and construction of the proposed transportation 

improvements. 

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Frankel, A., Mueller, C., Barnhard, T., Perkins, D., Leyendecker, E.V., Dickman, N., Hanson, S., 

and Hopper, M., 1997, Seismic Hazard Maps for California, Nevada and Western Arizona/Utah, Map A- Peak Horizontal Acceleration with a 10 Percent Probability of 

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Scale 1:24,000. 

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State Highway in San Bernardino County between Victorville and Barstow: Stoddard 

Wells Road Overcrossing, Drawings C-5224-1 through C-5224-4, C-52224-10 and 

C-5224-11; Cement Co. Undercrossing, Drawing C-4853-7; Bell Mountain Wash Bridge, 

Drawing C-4691-11. 

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Highway in San Bernardino County in Apple Valley at the Bell Mountain Wash Bridges: 

Bell Mountain Wash Bridge, Sheet 1 of 6. 

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State of California Business and Transportation Agency Department of Public Works Division of 

Highways, 1973, Project Plans for Construction on State Highway in San Bernardino 

County at Various Locations Between 7.5 Miles North of Mojave River Near Victorville 

and 2.6 Miles South of Townsend Street Overcrossing Near Barstow: Wild Wash Road 

Overcrossing, Drawing PR.NO.8, P-615031; Hodge Road Overcrossing, Drawings 

54566-1, PR.NO.7; Wild Wash Bridge (Widen), Drawing 54-500; Sidewinder Road 

Overcrossing, Drawing 54567-1, 54567-2, and 54567-7. 

State of California Department of Public Works, 1962, Division of Highways, Plans for Construction on State Highway in San Bernardino County Between 5.0 Miles West of Yermo 

and Field: Calico Road Overcrossing, Drawings C-54628-1 through C-54628-5; First 

Street Overcrossing, Drawing C-54629-5; Calico Road Undercrossing, Drawing 

C-54627-12; Yermo Ditch Bridge, Drawings C-54667-1 through C-54667-3, C-54667-5, 

C-54630-6; East Yermo Overcrossing, Drawing C-54631-8; Minneola Road Overcrossing, Drawing C-54632-1 through C-54632-5 and, C-54632-7; Coyote Lake Road 

Overcrossing, Drawing C-54633-7; Harvard Road Overcrossing, Drawing C-54634-7; 

Alvord Mountain Road Overcrossing, Drawing C-54635-7; West Manix Wash Bridge, 

Drawing C-54636-5; East Manix Bridge, Drawing C-54637-5; Mound Wash, Drawing 

C-54638-5; Flat Ditch, Drawing C-54639-6; Field Road Overcrossing, Drawing 

C-54640-7.

State of California Department of Public Works, 1963, Plans for Construction on State Highway 

in San Bernardino County Between Field and Cronese Valley: Sheet 1-2, 4-10, 12-14, 

17-19, 28, 35, 39,42, 114-119, 125-126, 137, 148, 149, 161-162, 174-175, 186, 188-190, 

201-202, 204-205, and 214 of 214. 

State of California Department of Public Works, 1963, Division of Highways, Plans for Construction on State Highway in San Bernardino county Between Cronese Valley and 2 

Miles East of Baker: Sheets 1, 11, 16, 18, 25-28, and 35 of 421; Dock Ditch Bridge, 

Drawings 54246-7, 54246-11, 54246-4, 54246-18, 54246-19, and 54246-21; Dock Ditch 

Bridge/Tono Ditch Bridge, Drawing 54246-10; Tono Ditch Bridge, Drawings 54247-1, 

54247-2, 54247-4, 54247-14, and 54247-15; Rasor Road Overcrossing, Drawings 

54391-1, 54391-3, 54391-4, and 54391-9; Marl Ditch Bridge, Sheets 1,2, and 9 of 13; 

Opah Ditch Bridge, Drawings 54251-1, 54251-2, 54251-14, and 54251-15; Turtle Ditch 

Bridge, Drawings 54252-1, 54252-2, 54252-12, and 54252-13; Soda Road Overcrossing, 

Drawings 54398-1, 54398-3, and 54398-9; Oat Ditch Bridge, Drawings 54270-1, 

54270-2, 54270-15, and 54270-16; Oat Ditch Bridge/ Tork Ditch Bridge, Drawing 

54270-10; Tork Ditch Bridge, Drawings 54271-1, 54271-2, 54271-13, and 54271-14; 

Case Ditch Bridge, Drawings 54273-1, 54273-2, 54273-9, 54273-13, and 54273-14; 

Sheep Ditch Bridge, Drawings 54274-1, 54274-2, 54274-14, and 54274-15; Banner Ditch 

Bridge/ Sheep Ditch Bridge/ Mobi Ditch Bridge, Drawing 54274-9; Mobi Ditch Bridge, 

Drawing 54277-1, 54277-2, 54277-14, and 54277-15; West Baker Overcrossing, Drawings 54609-1, 54609-3 through 54609-6, 54609-9, and 54609-10; Mojave River (Baker) 

Bridge, Drawing 54278-1, 54278-3, and 54278-15; Route 127/15 Separation, Drawings 

54610-1, 54610-3, and 54610-9; Baker Inn Ditch Bridge, Drawings 54279-1, 54279-2, 

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54279-10, 54279-14, and 54279-15; East Baker Overcrossing, Drawings 54611-1, 

54611-3, and 54611-9; Pano Ditch Bridge, Drawings 54281-1, 54281-3, 54281-15, 

54281-17, 54281-18, and 54281-26. 

State of California Department of Public Works, 1973, Division of Highways, Plan and Profile of 

State Highway in San Bernardino County, between 6 Miles West of Baker and Halloran 

Summit: “K” Line Plan and Cross Section; “L” Line Plan and Cross Section; Plan and 

Profile of Storm Ditches and Dikes. 

State of California Department of Public Works, 1960, Division of Highways, Plans for Construction on State Highway in San Bernardino County Between 1.5 Miles East of Baker 

and 1.0 Mile East of Cima Road: Sheets 1, 7, 12, 19, 20, 21, 24, 26, 28, 29,33-35, 45, 45, 

and 47 of 200; Berry Ditch Bridge, Drawing C-5553-3; Hack Wash Bridge, Drawing 

C-5553-8; Halloran Wash Bridge, Drawings C-5553-2, C-5553-14, and C-5553-41; Halloran Springs Overcrossing, Drawings SC-5835-1, SC-5835-2, and C-5835-11; Halloran 

Summit Overcrossing, Drawings SC-5836-1, SC-5836-2, and C-5836-11; Cima Road 

Overcrossing, Drawings SC-5837-1, SC-5837-2, and C-5877-11; Dale Ditch Bridge, 

Drawings C-5553-11, C-5553-15, and C-5553-42; Kali Ditch Bridge, Drawings 

C-5553-9, C-5553-16, and C-5553-43; West Valley Wells Ditch Bridge, Drawings 

C-5553-7, C-5553-17, and C-5553-44; Valley Wells Ditch Bridge, Drawings C-5553-6, 

and C-5553-18; Windmill Station Ditch Bridge, Drawings C-5553-5, C-5553-19, and 

C-5553-45; Wells Ditch Bridge, Drawings C-5553-10, C-5553-20, and C-5553-46; Hot 

Wash Bridge, Drawings C-5553-4, C-5553-21, and C-5553-47; Berry Ditch Bridge, 

Drawings C-5553-12, and C-5553-40; Hack Wash Bridge, Drawing C-5553-13. 

State of California Department of Transportation, 2003, Project Plans for Construction on State 

Highway in San Bernardino County from 8.2 km North of Halloran Summit Overcrossing to 0.1 kilometer South of Cima Road Overcrossing: Sheets 1, 4, 5, 8, 11 and 12 

of 261. 

State of California Department of Public Works, 1961, Division of Highways, Plans for Construction on State Highway in San Bernardino County Between Cima Road about 26 

Miles East of Baker and Nevada State Line: Sheets 1, 8, 11, 13-16, 18, 19, 21-26, 29, 35, 

37, and 38 of 205; Mescal Ditch Bridge, Drawings C-54303-1, C-54303-2, and 

C-54303-7; Clark Mountain Ditch Bridge, Drawings C-54304-1, C-54304-3, and 

C-54304-6; Mohawk Ditch Bridge, Drawings C-54618-1, C-54618-2, and C-54618-5; 

Micro Ditch Bridge, Drawings C-54619-1, C-54619-2, and C-54619-5; Bailey Road 

Overcrossing, Drawings C-54613-1, C-54613-2, and C-54613-9; Cenda Ditch Bridge, 

Drawings C-54620-1, C-54620-2, and C-54620-5; Wheaton Wash Bridge, Drawings 

C-54621-1, C-54621-2, and C-54621-5; Wheaton Springs Wash Bridge, Drawings 

C-54315-1, C-54315-2, and C-54315-5; Nipton Road Overcrossing, Drawings 

C-54612-1, C-54612-3, and C-54612-10; Ivanpah Ditch Bridge, Drawings C-54316-1, 

C-54316-2, and C-54316-5; Dry Lake Ditch Bridge, Drawings C-54317-1, C-54317-2, 

and C-54317-5; Yates Well Road Overcrossing, Drawings C-6930-1, C-6930-3, and 

C-6930-10.

206725001 R Prelim Geo.doc F-J-125 118
DesertXpress Rail Line May 1, 2007

Victorville, California to Las Vegas, Nevada Project No. 206725001 

State of California Department of Transportation, 1995, Earthquake Retrofit Project No. 591: 

Mojave River Bridge, General Plan; Mojave River Bridge, Abutment Retrofit Details; 

Mojave River Bridge, Hinge Retrofit Details No.2. 

State of California Department of Transportation, 1997, Project Plans for Construction on State 

Highway in San Bernardino County in Barstow at Mojave River Bridge: Sheets 1 and 

2 of 6. 

State of California Department of Transportation, 2000, Project Plans for Construction on State 

Highway in San Bernardino County near Barstow at Hiker Ditch Bridge: Hiker Ditch 

Bridge (Replace), Sheets 1,3,4,5, and 9 of 9. 

Sutch and Dirth, 2000, California Geology, pgs. 2-31 through 2-33. 

United States Department of Agriculture, 1985, Soil Survey of Las Vegas Valley Area of Nevada, 

Part of Clark County: Scale 1:24,000 on Sheets 1 through 16. 

United States Geological Survey, 1956 (Photorevised 1993), Victorville, California, Quadrangle 

Map, 7.5 Minute Series: Scale 1:24,000. 

United States Geological Survey, 1971 (Photorevised 1993), Barstow, California, Quadrangle 

Map, 7.5 Minute Series: Scale 1:24,000. 

United States Geologic Survey, 1991, Reconnaissance Photogeologic Map of Young Faults in the 

Las Vegas 1 Degree By 2 Degrees Quadrangle, Nevada, California, and Arizona: 

Scale 1: 250,000. 

United States Geological Survey, 1997 (2002rev), National Seismic Hazard Mapping Project, 

http://geohazards.cr.usgs.gov.eq. 

Wells, D.L., and Coppersmith, K.J., 1994, New Empirical Relationships Among Magnitude, 

Rupture Length, Rupture Area, and Surface Displacement: Bulletin of the Seismological 

Society of America, Volume 84, No. 4, pp. 974-1002, dated August. 

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DesertXpress Rail Line May 1, 2007

Victorville, California to Las Vegas, Nevada Project No. 206725001 

206725001 R Prelim Geo.doc F-J-127 120
DesertXpress Rail Line May 1, 2007

Victorville, California to Las Vegas, Nevada Project No. 206725001 

206725001 R Prelim Geo.doc F-J-128 121
DesertXpress Rail Line May 1, 2007

Victorville, California to Las Vegas, Nevada Project No. 206725001 

206725001 R Prelim Geo.doc F-J-129 122
F-J-130
F-J-131
SEGMENT 2

Alternative A

SEGMENT 2

Alternative B

FIGURE

3 PROJECT NO. DATE

5/07

0 5 10

APPROXIMATE SCALE IN MILES

NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.

VICINITY MAP

PROPOSED RAIL LINE

VICTORVILLE TO LAS VEGAS 206725001

SEGMENT 2

REFERENCE: AUTOMOBILE CLUB OF SOUTHERN CALIFORNIA, 2002.

F-J-132
SEGMENT 3

Alternatives A & B Cronese Valley

M O J A V E

V A L L E Y

R I V E R

Valley Wells

FIGURE

4

LEGEND

PROPOSED RAIL LINE

VICTORVILLE TO LAS VEGAS

PROJECT NO.

206725001

DATE

5/07

PROPOSED ALIGNMENTS

REFERENCE: AUTOMOBILE CLUB OF SOUTHERN CALIFORNIA, 12-2004.

NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.

SEGMENT 3

VICINITY MAP

0 5 10

APPROXIMATE SCALE IN MILES

F-J-133
SEGMENT 4

Alternative A

SEGMENT 4

Alternative B

FIGURE

5 PROJECT NO. DATE

5/07

0 5 10

APPROXIMATE SCALE IN MILES

NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.

VICINITY MAP

PROPOSED RAIL LINE

VICTORVILLE TO LAS VEGAS 206725001

SEGMENT 4

REFERENCE: AUTOMOBILE CLUB OF SOUTHERN CALIFORNIA, 2002.

F-J-134
F-J-135
SEGMENT 6

Alternatives C & D

SEGMENT 7

Alternatives A & B SEGMENT 7

Alternative C

SEGMENT 6

Alternatives A & B

SEGMENT 7

Alternatives A & B

SEGMENT 7

Alternative C

FIGURE

7 PROJECT NO. DATE

5/07

0 10

APPROXIMATE SCALE IN MILES

NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.

VICINITY MAP

PROPOSED RAIL LINE

VICTORVILLE TO LAS VEGAS 206725001

SEGMENT 6 & 7

REFERENCE: AUTOMOBILE CLUB OF SOUTHERN CALIFORNIA, 12-2004.

20

F-J-136
SEGMENT 1

Alternative A SEGMENT 1

Alternative B

SEGMENT 2

Alternative A

SEGMENT 2

Alternative B

SEGMENT 2

Alternative A SEGMENT 3

Alternatives A & B

Victorville

Station

FIGURE

8 PROJECT NO. DATE PROPOSED RAIL LINE VICTORVILLE TO LAS VEGAS

REGIONAL GEOLOGIC MAP

5/07 206725001 REFERENCE: JENNINGS, C.W., 1962, GEOLOGIC MAP OF CALIFORNIA, TRONA SHEET.

10

NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.

APPROXIMATE SCALE IN MILES

N

5

EXPLANATION

Alluvium

Wash deposits

Wind-blown sand

0

Older lake deposits

Continental deposits

Unnamed Miocene continental deposits

Mesozoic metavolcanic

Older Alluvium

Well dissected

Cretacious or Jurassic

alluvial fans

rocks

quartz monzonite

Jurassic hornblenddiorite and minor gabbro

Lake deposits

F-J-137
SEGMENT 3

Alternatives A & B

FIGURE

9

REGIONAL GEOLOGIC MAP

PROPOSED RAIL LINE

VICTORVILLE TO LAS VEGAS

PROJECT NO.

206725001

DATE

5/07

N

0 5

APPROXIMATE SCALE IN MILES

NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.

10

REFERENCE: JENNINGS, C.W., 1962, GEOLOGIC MAP OF CALIFORNIA, TRONA SHEET.

EXPLANATION

AlluviumQuaternary lake depositsPleistocene volcanicPleistocene nonmarinePlio-Pleistocene nonmarineTertiary volcanicTertiary nonmarineMesozoic graniticPaleozoic marine

F-J-138
SEGMENT 3

Alternatives A & B

SEGMENT 4

Alternative A 

SEGMENT 4

Alternative B

SEGMENT 5

Alternatives A & B

FIGURE

10 PROJECT NO. DATE PROPOSED RAIL LINE VICTORVILLE TO LAS VEGAS

REGIONAL GEOLOGIC MAP

5/07 206725001 REFERENCE: JENNINGS, C.W., 1962, GEOLOGIC MAP OF CALIFORNIA, KINGMAN SHEET.

10

NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.

APPROXIMATE SCALE IN MILES

N

5

EXPLANATION

AlluviumQuaternary lake depositsEarlier Precambrian metamorphic rocks

0

Volcanic rocksOlder alluvial depositsGranitic rocksMississippian Marine rocksMarine sedimentary and metasedimentaryrocks

F-J-139
SEGMENT 5

Alternatives A & B

SEGMENT 6

Alternatives C & D

SEGMENT 6

Alternatives A & B

SEGMENT 7

Alternatives A & B

SEGMENT 7 Alternative C

5/07

DATE

206725001

PROJECT NO. 11

FIGURE

PROPOSED RAIL LINE

VICTORVILLE TO LAS VEGAS

REGIONAL GEOLOGIC MAP

REFERENCE: LONGWELL, C.R., PAMPEYAN, E.H., AND BOWER, B., 1964,

10 NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.

APPROXIMATE SCALE IN MILES

5

N

0

Alluvium

Volcanic rocks

Bird Spring Formation

Goodsprings Dolomite

Monte Cristo Limestone

Sultan Limestone

EXPLANATION

GEOLOGIC MAP OF CLARK COUNTY, NEVADA.

F-J-140
F-J-141
F-J-142
F-J-143