APPENDIX B – GEOTECHNICAL EVALUATION MEMORANDUM

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TABLE OF CONTENTS

Section Page 1.0 Introduction ............................................................................................................................... 1 

1.1  Purpose and Scope of Works ......................................................................................... 1 1.2  Proposed Conceptual Alternatives ................................................................................. 1 

1.2.1  Concept #1 - At-Grade Sepulveda Boulevard Fixed Guideway Bus Rapid Transit (BRT) ................................................................................................................. 1 1.2.2  Concept #2 - At-Grade Freeway Managed Lanes ............................................. 2 1.2.3  Concept #3 - Highway Viaduct Managed Lanes .............................................. 2 1.2.4  Concept #4 - Tolled Highway Tunnel .............................................................. 2 1.2.5  Concept #5 - Fixed Guideway Light Rail Transit Tunnel ................................ 2 1.2.6  Concept #6 - Highway/Private Shuttle Tunnel ................................................. 3 

2.0 Data Collection and Literature Review ................................................................................... 10 3.0 Regional Geology ................................................................................................................... 11 

3.1  Physiography ................................................................................................................ 11 3.2  Structure ....................................................................................................................... 12 3.3  Stratigraphy .................................................................................................................. 12 3.4  Groundwater ................................................................................................................. 13 

4.0 Faulting and Seismicity........................................................................................................... 19 4.1  Faulting ........................................................................................................................ 19 

4.1.1  San Fernando Fault ......................................................................................... 19 4.1.2  Mission Hills Fault .......................................................................................... 19 4.1.3  Northridge Hills Fault ..................................................................................... 19 4.1.4  Verdugo Fault ................................................................................................. 20 4.1.5  Santa Monica Fault ......................................................................................... 20 4.1.6  Hollywood Fault ............................................................................................. 21 4.1.7  West Beverly Hills Lineament ........................................................................ 21 4.1.8  Benedict Canyon Fault .................................................................................... 21 4.1.9  Newport-Inglewood Structural Zone (NISZ) .................................................. 22 4.1.10  Other Faults ..................................................................................................... 22 

4.2  Seismicity ..................................................................................................................... 22 5.0 Geologic and Seismic Hazards ............................................................................................... 27 

5.1  Geologic Hazards ......................................................................................................... 27 5.1.1  Landslides ....................................................................................................... 27 5.1.2  Oil Field Related Hazard ................................................................................ 27 5.1.3  Hazardous Material ......................................................................................... 28 5.1.4  Rock Topple .................................................................................................... 28 5.1.5  Expansive Soils ............................................................................................... 29 5.1.6  Collapsible Soils ............................................................................................. 29 5.1.7  Flooding and Scour ......................................................................................... 29 

5.2  Seismic Hazards ........................................................................................................... 30 5.2.1  Liquefaction .................................................................................................... 30 5.2.2  Lateral Spreading ............................................................................................ 30 5.2.3  Seismic Settlement .......................................................................................... 31 

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5.2.4  Potential for Ground Shaking ......................................................................... 31 5.2.5  Fault Related Ground Rupture ........................................................................ 31 5.2.6  Ground Lurching ............................................................................................. 32 5.2.7  Earthquake Induced Landslides ...................................................................... 32 5.2.8  Seismically Induced Inundation ...................................................................... 33 5.2.9  Tsunamis ......................................................................................................... 33 

6.0 Geotechnical Evaluations ........................................................................................................ 35 6.1  Fault Rupture Considerations ....................................................................................... 35 6.2  Liquefaction Potential Considerations ......................................................................... 35 6.3  Strong Ground Motion Considerations ........................................................................ 36 6.4  Slope Stability Considerations ..................................................................................... 36 6.5  Foundation Type Considerations ................................................................................. 36 

6.5.1  Aerial Structures ............................................................................................. 36 6.5.2  Earth Retaining Structures .............................................................................. 37 6.5.3  At-Grade Stations and Appurtenant Structures ............................................... 38 

6.6  Hazardous Material Considerations ............................................................................. 38 6.7  Tunneling Considerations ............................................................................................ 38 

6.7.1  Geologic Formations ....................................................................................... 39 6.7.2  Geologic Structure .......................................................................................... 39 6.7.3  Groundwater ................................................................................................... 39 6.7.4  Caving Soil...................................................................................................... 40 6.7.5  Ground Settlement .......................................................................................... 40 6.7.6  Naturally Occurring Gas ................................................................................. 40 

6.8  Other Considerations .................................................................................................... 40 7.0 Discussions and Conclusions .................................................................................................. 42 8.0 Limitations .............................................................................................................................. 45 9.0 References ............................................................................................................................... 46 

LIST OF FIGURES Figure 1-1- Concept #1 Figure 1-2– Concept #2 ............................................................................ 4 Figure 1-3 – Concept #3 ................................................................................................................. 6 Figure 1-4– Concept #4Figure 1-5 – Concept #5 ........................................................................... 7 Figure 1-6 – Concept #6 ................................................................................................................. 9 Figure 3-1 – Regional Physiographic Map ................................................................................... 15 Figure 3-2 – Regional Geologic Map ........................................................................................... 16 Figure 3-3a – CGS Groundwater Map .......................................................................................... 17 Figure 3-4b – CGS Groundwater Map.......................................................................................... 18 Figure 4-1a – Regional Geologic/Geotechnical Hazard Map ....................................................... 25 Figure 4-2b – Regional Geologic/Geotechnical Hazard Map ....................................................... 26 Figure 5-1 – Landslide Inventory Map ......................................................................................... 34 

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1.0 INTRODUCTION

1.1 Purpose and Scope of Works

The Sepulveda Pass Corridor Systems Planning Study area extends approximately twenty seven miles from the San Fernando Valley in Sylmar near the I-405 and I-5 interchange, southerly across the Santa Monica Mountains through the Sepulveda Pass to Culver City and Inglewood in the Los Angeles Basin to the I-405 and 105 freeway interchange near Los Angeles International Airport (LAX). The project concepts are shown on Figures 1-1 to 1-6. The purpose of this geotechnical memorandum is to assist the planning team to analyze and assess the geologic and geotechnical conditions associated with each conceptual alternative. Our scope of work included the following tasks:

Reviewing available pertinent geological and geotechnical reports in our database; Evaluating potential geologic and seismic hazards along the subject corridor; Preparing this geotechnical memorandum to summarize the findings of our evaluation of

each concept by physiographic regions due to the diverse geologic conditions associated with each of the regions within the study area. These regions are the San Fernando Valley, Sepulveda Pass (Santa Monica Mountains) and the Los Angeles Basin (West Los Angeles).

1.2 Proposed Conceptual Alternatives

The Sepulveda Pass Corridor Systems Planning Study is being conducted for the purpose of identifying the most cost-effective transportation investment using a range of conceptual highway and/or transit transportation improvements. Six (6) conceptual alternatives were developed in an effort to determine a high-level transportation plan along the study area. The alternative Systems planning concepts and methods include but are not limited to fixed rail, bus rapid transit service, highway improvements and toll lanes/tollways, grade separated tunnel and/or elevated guideway along I-405 or parallel facilities, and multi-modal grade separated transit and express toll road facility. These six concepts are discussed in the following subsections.

1.2.1 Concept #1 - At-Grade Sepulveda Boulevard Fixed Guideway Bus Rapid Transit (BRT)

The first conceptual option is called the At-Grade Sepulveda Boulevard Bus Rapid Transit (BRT) and the associated alignment would span from the San Fernando Valley to Los Angeles International Airport (LAX). The BRT would travel southeast from the San Fernando Metrolink Station in Sylmar along San Fernando Boulevard to Van Nuys Boulevard. The BRT would then turn south along Van Nuys Boulevard to Burbank Boulevard. The route continues west along Burbank Boulevard until it enters the I-405 heading south. The BRT will then travel along the I-405 freeway shoulder during peak hours with buses eventually exiting at Getty Center Drive where it connects with Sepulveda Boulevard heading south. The BRT remains on Sepulveda Boulevard with priority treatment until it reaches the southern terminus at Century/Aviation Station of the Metro Crenshaw/LAX Transit Corridor. Concept #1 improvements would be limited to some pavement design and minor roadway spot widening. See Figure 1-1 for the concept map.

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1.2.2 Concept #2 - At-Grade Freeway Managed Lanes

The second conceptual alternative involves a Managed Lanes (ML) corridor along the I-405 freeway between Rinaldi Street in San Fernando Valley and Los Angeles International Airport. The managed lanes would incorporate High Occupancy Toll (HOT) lanes along I-405. In areas both north and south of the Santa Monica Mountains, two HOT lanes would be used, while only one HOT lane would be available through the Sepulveda Pass.

A BRT would provide service along the ML corridor between San Fernando Valley and West LA. The BRT would maintain three routes originating from three different locations in San Fernando Valley (Sylmar, Chatsworth, and North Hollywood) with a transfer point at the Sepulveda Orange Line Station.

All three routes will utilize the ML corridor to connect between San Fernando Valley and West Los Angeles. Creating the additional lane space would require re-striping and some spot widening along the freeway as well as some direct access ramps at La Grange Avenue and the Howard Hughes Center. The subsequent proposed improvements involved with Concept #2 include spot widening along I-405 with potential for widening along BRT arterial streets as well as proposed direct access ramp related structures and improvements. Concept #2 is shown in Figure 1-2.

1.2.3 Concept #3 - Highway Viaduct Managed Lanes

The third conceptual alternative would incorporate a proposed elevated viaduct above the I-405 median between the US-101 freeway to the north and the I-10 freeway to the south with some potential for widening and direct access ramp improvements. The viaduct would provide two HOT lanes in each direction allowing for the existing HOV lanes to become dedicated lanes for BRT service. The BRT service would extend between Sylmar/San Fernando Metrolink Station to the north and the Sepulveda Expo Line Station to the south. Concept #3 is shown on a map in Figure 1-3.

Similar to Concept #2, the portions north and south of the viaduct would act as ML corridors with two HOT lanes. At the transition points with the viaduct, the ML routes would drop the second HOT lane and transition into the single-HOV (converted to HOT) lane.

1.2.4 Concept #4 - Tolled Highway Tunnel

A four-lane toll tunnel is proposed as part of the fourth conceptual alternative. The tunnel is proposed to be loosely aligned with the I-405 freeway through Santa Monica Mountains between Magnolia Boulevard at the north portal and either Santa Monica Boulevard or Venice Boulevard at the south portal (Figure 1-4). The tunnel would provide service to buses and private automobiles, with service for carpools requiring a toll. The associated improvements would include a bored tunnel section along with trench sections and potential fly-over structures for direct access from major freeways and arterials.

1.2.5 Concept #5 - Fixed Guideway Light Rail Transit Tunnel

This conceptual alternative employs a Light Rail Transit (LRT) that will span from the San

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Fernando Valley to LAX (Figure 1-5). The majority of the alignment would remain at-grade with the exception of a tunnel segment extending between Ventura Boulevard and Van Nuys Boulevard at the north portal and Strathmore Place and Westwood Plaza at the south portal. The tunnel would be a transit-only tunnel that would loosely parallel the I-405. The non-tunnel segments will generally extend along an at-grade median-running right of way along arterials including San Fernando Boulevard, Van Nuys Boulevard, Westwood Boulevard, Overland Avenue, and Sepulveda Boulevard.

The associated improvements with the fixed light rail concept include a bored tunnel through the Sepulveda Pass and associated portal structures and trench sections. Other improvements include a new at-grade track alignment and any new station structures or platforms associated with the LRT.

1.2.6 Concept #6 - Highway/Private Shuttle Tunnel

Concept #6 consists of two separate tunnel alignments, a new highway and private shuttle rail alignment. Each alignment will have its own tunnel that cuts through the Sepulveda Pass. Both the toll highway tunnel and transit tunnel would loosely parallel the I-405 with the transit tunnel aligned further east. The alignments are shown on Figure 1-6. The highway tunnel would extend between Roscoe Boulevard to the north and Century Boulevard to the south. The transit rail alignment will extend between Van Nuys Metrolink Station and Century/Aviation Station. The highway tunnel will maintain direct access points at both the portals as well as near major freeway junctions including the 101 freeway, I-10, and highway 90. The private shuttle tunnel will have in-line stations at Wilshire Boulevard and at the junction with the Orange Line in San Fernando Valley.

The major improvements associated with Concept #6 include the two tunnels which include both bored sections as well as trench and cut and cover segments. Other improvements include associated portal structures and new stations.