Iv.D Geology

IV.D GEOLOGY

1. INTRODUCTION

This section identifies and evaluates geologic and soils conditions at the project site that could affect, or be affected by, implementation of the proposed project and recommends mitigation measures to avoid or lessen potential impacts. This section incorporates and summarizes information contained in a geotechnical investigation report prepared by R. T. Frankian & Associates Geotechnical Engineering and Engineering Geology, dated May 5, 2006. A copy of the report is provided in Appendix IV.D.

2. ENVIRONMENTAL SETTING a. Geology and Topography

The project site is located on the southeastern corner of Wilshire Boulevard and La Brea Avenue in the City of Los Angeles. Specifically, the approximately 3.4-acre project site comprises an entire city block and is bound by Wilshire Boulevard to the north, Sycamore Avenue to the east, 8th Street on the south, and La Brea Avenue to the west. Existing development on the site includes a three-story church (including a basement), a commercial strip center, a private alley, and paved parking areas.

The project site is located in a relatively flat area of the Los Angeles Basin. The terrain at the site slopes gently downward from north to south with a maximum difference in existing ground surface elevation of about 8 feet. No distinctive natural landforms are located around the project site.

The Santa Monica Mountain range and Santa Monica fault zone are located northwest of the project site. The Cucamonga fault zone is located 55 kilometers (34.18 miles) east of the project site. The La Brea Tar Pits are located to the west of the project site. b. Soils

According to the geotechnical investigation report prepared for the proposed project, five test borings were drilled on the site with a wash-boring drill rig. The borings were 5 inches in diameter and were carried to depth between 51 and 61 feet below present grade.

Structures and asphalt pavement covers nearly the entire site. No appreciable amounts of filled soils were found beneath the pavement. The naturally deposited soils consist of, for the most part, silty clay with variable amounts of silt. The soil is generally classified as stiff, although at some locations it is classified as firm or very firm. Each boring encountered layers of silty sand and clayey sand, which are generally

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dense and occasionally very dense. These sand layers were at depths ranging from near surface to the bottom of some borings. c. Groundwater

Groundwater was found in each of the five borings. The groundwater levels ranged from approximately 16 feet to 21 feet in depth.Recent readings in the monitoring wells were of similar levels. According to the State of California Division of Mines and Geology, the historic high groundwater level is at a depth of about 12 feet. d. Tectonics

The project site, as with all of Southern California, is located within a seismically active region. However, the project site is not within a currently designated Fault Rupture Hazard Zone. The closest fault to the project site is the Santa Monica fault and is located approximately 4.5 kilometers (km) (2.8 miles) northwest of the site.

The anticipated peak horizontal ground acceleration for the maximum probable earthquake presented in the Seismic Evaluation Report for the project area, California Division of Mines and Geology (CDMG) Open-File Report 98-17, is 0.46 g (acceleration due to gravity). The maximum probable earthquake as defined in the Los Angeles Uniform Building Code (LAUBC) is the maximum seismic event anticipated with a 10 percent probability of exceedance in 50 years. e. Liquefaction

Liquefaction is a form of earthquake-induced ground failure that occurs primarily in relatively shallow, loose, granular, water-saturated soils. Liquefaction is the sudden decrease in the cohesiveness of soils, which, in turn, creates a liquefaction of soils. Liquefaction potential has been found to be the greatest where the groundwater level and loose sands occur within a depth of about 50 feet or less. The potential for liquefaction decreases with increasing soil and sand grain size and clay and gravel content, but increases as the ground acceleration and duration of shaking increase.

The project site is not in a liquefaction area as designated by the State of California Seismic Hazard Zones Map, Hollywood Quadrangle, dated March 25, 1999. The site is not in an earthquake fault zone, as shown on the State of California Special Studies Zones Map, Hollywood Quadrangle, Revised Official Map, dated July 1, 1986.

Although the historic high groundwater level is at a depth of only about 12 feet (Open-File Report 98-17, Division of Mines and Geology), the firm to stiff clay soils and the dense to very dense sands create a low

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to very low potential for soil liquefaction at the site. The soils generally contain silt and occasionally contain gravel. They have high blow counts for the obtained soil samples.

The project site is not listed near or on a liquefaction zone based on the California Geologic Survey (CGS) hazards maps.1

3. REGULATORY FRAMEWORK a. Federal Regulations

Flood Insurance Rate Maps are prepared by the Federal Insurance Administration of the Department of Housing and Urban Development (HUD) after a risk study for a community has been completed and the risk premium rates have been established. The maps indicate the risk premium zones applicable in the community and when those rates are effective. They are used in making flood plain determinations and to determine if a proposed action is located in the base or critical action flood plain, as appropriate.

Because, collectively, the project is over 1 acre in size, a General Permit for Discharges of Storm Water Associated with Construction Activity is required by the Los Angeles Regional Water Quality Control Board (LARWQCB), as part of the National Pollution Discharge Elimination System (NPDES), to control erosion and pollution during construction of the project. The permit requires the project applicant to prepare and submit a Storm Water Pollution Prevention Plan (SWPPP) to be administered throughout project construction. The SWPPP must list Best Management Practices (BMPs) that the discharger (project applicant) will use to protect stormwater runoff. b. State and Regional Regulations

Under the Seismic Hazards Mapping Act, the CGS provides maps of seismic hazard zones to local governments for planning purposes. These maps are intended to protect the public from the risks involved with strong ground shaking, liquefaction, landslides and other hazards related to earthquakes. CGS also provides guidelines to evaluate and mitigate hazards for projects within seismic hazard zones.

The Alquist-Priolo Earthquake Fault Zoning Act (PRC Section 2621.5) provides policies and criteria to assist cities, counties, and state agencies in the development of structures for human occupancy across the trace of active faults. Maps associated with this act show the seismic hazard zones throughout California.

1 Seismic Hazards Zonation Program, “California Geological Survey”, http://gmw.consrv.ca.gov/shmp/ (2007).

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The South Coast Air Quality Management District’s Rule 403 – Fugitive Dust requires projects to comply with specific actions to prevent, reduce, or mitigate fugitive dust emissions during excavation, demolition, and other construction activities.

The project applicant must comply with the California Building Code (CBC) (CCR Title 24, Part 2), which provides guidelines for building design to protect occupants from seismic hazards. c. Local Regulations

The City of Los Angeles also regulates building design through the LAUBC. The LAUBC provides requirements for construction, grading, excavations, use of fill and foundation work, including type of materials, design and procedures, which are intended to limit the probability of occurrence and the severity of consequences from geological hazards.

4. ENVIRONMENTAL IMPACT ANALYSIS a. Significance Criteria

The following thresholds for determining the significance of impacts related to geologic hazard conditions are contained in the L.A. California Environmental Quality Act (CEQA) Thresholds Guide, which was adopted by the City Council in 2006. Impacts related to geologic hazards are considered significant if the proposed project would

 Cause or accelerate geologic hazards, which would result in substantial damage to structures or infrastructure, or expose people to substantial risk of injury.

Impacts related to sedimentation and erosion are considered significant if the proposed project would

 Constitute a geologic hazard to other properties by causing or accelerating instability from erosion; or

 Accelerate natural processes of wind and water erosion and sedimentation, resulting in sediment runoff or deposition that would not be contained or controlled on site.

Impacts related to landform alteration are considered significant if the proposed project would

 Have one or more distinct and prominent geologic or topographic features destroyed, permanently covered, or materially and adversely modified. Such features may include, but are not limited to, hilltops, ridges, hill slopes, canyons, ravines, rock outcrops, water bodies, streambeds, and wetlands.

Los Angeles Department of City Planning IV.D-4 Wilshire and La Brea Project Draft EIR Impact Sciences, Inc. (906-01) August 2008 IV.D Geology b. Project Impacts

The Wilshire and La Brea Project would provide a total of 562 new residential units and approximately 45,000 square feet of retail. The residential mix would include 138 studio units, 315 one-bedroom units, and 109 two-bedroom units. The retail component would include 37,000 square feet of general retail and 8,000 square feet of restaurant space. The proposed structure would occupy a total of 920,000 gross square feet of floor area, with a floor area ratio (FAR) averaging 3.4:1.

The proposed structure would consist of six levels of apartment dwellings atop an elevated base (podium) which would be approximately 20 feet above street level at the Wilshire Boulevard end of the property and approximately 28 feet above street level at 8th Street.

The residential floors would consist of two elements: a primary structure arranged in a “wing” configuration, which would create building “fingers” that would surround open-ended courtyards, and a smaller “bar” structure along the podium edge at Sycamore Avenue. The “finger” building would be six stories plus mezzanines above the podium, while the “bar” building would be two stories above the podium. Overall, the “finger” building would be a maximum of 100 feet above grade, and the “bar” building would be up to 44 feet above grade.

The proposed project would provide a total of 1,083 parking spaces. Parking would be provided in a partial above-ground “mezzanine” level, in a ground level, and in a 2.5-level subterranean structure.

Geologic Hazards

Seismic Ground Shaking

Impacts related to geologic hazards are considered significant if the proposed project would

 Cause or accelerate geologic hazards, which would result in substantial damage to structures or infrastructure, or expose people to substantial risk of injury.

Surface Fault Rupture

The project site is located approximately 4.5 km (2.8 miles) from the surface projection of the Santa Monica fault and 55 km (34.2 miles) from the surface project of the Cucamonga fault. For purposes of planning, zoning, and building regulation functions, the state provides maps to City and County agencies designating Alquist-Priolo Earthquake Fault Zones. The project is not located within a state-designated

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Alquist-Priolo Earthquake Fault Zone.2 The nearest fault zone is the Santa Monica Fault Zone, located approximately 2.8 miles north of the project site.3

Faults located within the vicinity of the project, along with their distance to and direction from the project site, are listed in Table IV.D-1, Fault Locations in the Vicinity of the Project Site. As a result of the project’s proximity to faults in the greater Los Angeles area, the potential for surface rupture resulting from the movement of this fault or other nearby faults, although not known with certainty, is considered to be low. Therefore, impacts resulting from potential surface fault rupture would not expose people to substantial risk of injury and would be less than significant.

Table IV.D-1 Fault Locations in the Vicinity of the Project Site

Distance to Site Fault Type Nearest Fault km(miles) Magnitude B Santa Monica 4 (2.4) 6.6 B Newport-Inglewood 4 (2.4) 6.9 B Hollywood 5 (3.0) 6.5 B Eagle Rock 14 (8.4) -- B Raymond 15 (9.0) 6.5 B Verdugo 16 (9.6) 6.7 B Malibu Coast 19 (11.4) 6.7 B Palos Verdes 20 (12.0) 7.1 B Whittier 29 (17.4) 7.0 B Redondo Canyon 31 (18.6) 7.1 B Los Alamitos-West Baseline 32 (19.2) 6.8 B Cabrillo 34 (20.4) 7.1 A Cucamonga 55 (33.0) 7.0

Strong Seismic Ground Shaking

The site, similar to all of Southern California, is located within a seismically active region. The site is not within a currently designated Fault Rupture Hazard Zone, but is located approximately 4.5 km (2.8 miles) south of the Santa Monica fault. Accordingly, strong ground shaking is anticipated as a result of a major seismic event at the proposed project site. The provisions of the CBC and LAUBC are considered

2 City of Los Angeles Department of Planning, Parcel Profile Report for 5220 W. Wilshire Boulevard, 5224 W. Wilshire Boulevard, 5222 W. Wilshire Boulevard, 700 S. La Brea Avenue, 702 S. La Brea Avenue, 704 S. La Brea Avenue, 706 S. La Brea Avenue, 708 S. La Brea Avenue, 700 1/2 S. La Brea Avenue, 2007. 3 RTF&A Geotechnical Engineering and Engineering Geology, Draft Report of Preliminary Geotechnical Investigation, Proposed Wilshire La Brea Mixed-Use Project, 5220 Wilshire Boulevard, Los Angeles, California for Wishlab 90, LLC, 2006.

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appropriate for the design of the proposed project. As the proposed structure would be designed in accordance with the CBC and LAUBC to ensure safety in the event of an earthquake, impacts associated with strong seismic ground shaking are anticipated to be less than significant.

Seismic Related Ground Failure, including Liquefaction

Liquefaction potential has been found to be the greatest where the groundwater level and loose sands occur within a depth of approximately 50 feet below ground surface or less. The potential for liquefaction decreases with increasing grain size and clay and gravel content, but increases as the ground acceleration and duration of ground shaking increase.

Although the historic high groundwater level is at a depth of only about 12 feet, the firm to stiff clay soils and the dense to very dense sands create a low to very low potential for soil liquefaction at the site. These soils generally contain silt and occasionally contain gravel. They have high blow counts for the obtained soil samples. As such, the impacts to liquefaction are less than significant.

Landslides

The project site, as well as the surrounding area, is relatively flat. Landslides, lateral spreading, and slope failures are associated with sloping land and, therefore, the potential at the project site for seismically induced landslides or other ground failures associated with slopes is very low. The potential for impacts to the project site and surrounding area from landslides is considered to be less than significant.

Soil Conditions

According to the Los Angeles County, California, USDA Natural Resources Conservation Service (NRCS) Report and General Soil Map (December 1969), soils at the project site are classified as Ramona-Placentia association (2 to 5 percent slopes). Ramona soils in the Los Angeles Basin are over 60 inches deep, are well drained, and have slow subsoil permeability. They are characterized by brown to reddish-brown, heavy loam, loam, or sandy loam surface layers about 18 inches thick. Placentia soils are over 18 inches deep, are moderately well drained, and have very slow subsoil permeability. They are characterized by brown to reddish-brown loam or sandy loam surface layers abruptly underlain by a dense, dark reddish-

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brown clay loam subsoil at about 18 inches. Permeability is slow, and available water capacity is 8 to 10 inches. Surface runoff is slow, and the erosion hazard is moderate.4

Sedimentation and Erosion

Impacts related to sedimentation and erosion are considered significant if the proposed project would

 Constitute a geologic hazard to other properties by causing or accelerating instability from erosion; or

 Accelerate natural processes of wind and water erosion and sedimentation, resulting in sediment runoff or deposition, which would not be contained or controlled on site.

Construction of the proposed project will require the removal of approximately 163,000 cubic yards of soil. Construction activity associated with project site development may result in wind and water driven erosion of soils due to grading activities if soil is stockpiled or exposed during construction. This impact would be considered short term in nature since the potential for significance would end after construction is finished. During project operation, each project site would be covered with structures, pavement, and landscaping.

As part of the project, the applicant would adhere to conditions under the NPDES permit set forth by the LARWQCB and prepare and submit an SWPPP, as outlined in MM-GEO-2, to be administered throughout project construction. The SWPPP would incorporate BMPs to ensure that potential water quality impacts during construction from erosion would be reduced to less than significant. In addition, the applicant would adhere to SCAQMD Rule 403 – Fugitive Dust during construction activities, which would further prevent impacts associated with wind erosion. The project applicant would employ actions described in MM-GEO-3, which are currently recommended to implement Rule 403 and have been quantified by the SCAQMD as being able to reduce dust generation between 30 and 85 percent depending on the source of the dust generation. All grading activities would require grading permits from the Department of Building and Safety, which include requirements and standards designed to limit potential impacts to acceptable levels. In addition, all on-site grading and site preparation would comply with applicable provisions of Chapter IX, Division 70, of the Los Angeles Municipal Code, which addresses grading, excavations and fills. Therefore, potential sedimentation and erosion impacts would be less than significant.

4 EFI Global, Final Phase I Environmental Site Assessment (Phase I ESA), Wilshire Property, 5220 Wilshire Boulevard and 714-780 South La Brea Avenue, Los Angeles, California, 90036.

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Risk of Flood

According to the official Flood Insurance Rate Maps from the Federal Emergency Management Agency, the project site is not located within a 100-year flood zone.5 Given the low chance of flooding on the project site, changes in geology due to flooding is not significant.

Groundwater

Groundwater beneath the project site has the potential to affect the proposed development during construction and during the life of the structure. Historical groundwater levels on the project site have been documented to be as shallow as 12 feet below the existing ground surface. Measures will be required for construction extending below the groundwater level, such as temporary dewatering or the use of drilling fluids to maintain open excavations. With adherence to one of these measures, geology and soil impacts associated groundwater during construction would be less than significant.

Concerning project operation, measures will also be required for all permanent structures extending near or below the groundwater level. Such measures should be determined by project consultants, and may include permanent dewatering, and/or waterproofing, and structure design to resist hydrostatic pressures (including uplift). With the selection of one of these measures, geology and soil impacts associated with groundwater would be less than significant.

Landform Alteration

Impacts related to landform alteration are considered significant if the proposed project would

 Have one or more distinct and prominent geologic or topographic features destroyed, permanently covered or materially and adversely modified. Such features may include, but are not limited to, hilltops, ridges, hill slopes, canyons, ravines, rock outcrops, water bodies, streambeds and wetlands.

The proposed Wilshire and La Brea Project siteis located on flat land in the Los Angeles area. This area is a highly urbanized area, and the project site is neither on nor near any unique or natural geologic or topographic features such as hilltops, ridges, hill slopes, canyons, ravines, rock outcrops, water bodies, streambeds, and/or wetlands. Therefore, the project would not have a significant impact by altering landforms.

5 Federal Emergency Management Agency. Map Service Center. “Public Flood Map.” http://www.fema.gov/ hazard/map/firm.shtm. 2007.

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Potential geologic hazards associated with the proposed project are site-specific and do not represent a cumulative impact concern. Implementation of the proposed project and other projects in the Southern California region would cumulatively increase the number of structures and people exposed to geologic- and seismic-related hazards. As long as project design and construction occurs consistent with proper engineering practices and to the requirements of applicable portions of the CBC and LAUBC as they apply to each component of the project, seismic and regional geologic hazards would not be considered cumulatively considerable.

Grading of the proposed project would adhere to the City’s thresholds and the City’s Department of Building and Safety codes and requirements. Grading and geologic hazards and features are not expected to have cumulative impacts as individual development projects would be required to comply with the requirements of the City’s Department of Building and Safety thresholds. Compliance with the City’s requirements would ensure that both individual and cumulative project impacts associated with the project’s structure and grading would not exceed the identified thresholds of significance. Therefore, impacts would not be cumulatively considerable and so are considered to be less than significant. d. Mitigation Measures

MM-GEO-1. The project shall be designed and constructed in accordance with the requirements outlined in the latest edition of the California Building Code and the Los Angeles Uniform Building Code, including all applicable provisions of Chapter IX, Division 70 of the Los Angeles Municipal Code, which addresses grading, excavations and fills.

MM-GEO-2. Prior to start of soil-disturbing activities at the site, a Notice of Intent (NOI) and SWPPP shall be prepared in accordance with, and in order to partially fulfill, the California State Water Resources Control Board Order No. 99-08-DWQ, NPDES General Permit No. CAS000002 (General Construction Permit), and Chapter 6 Article 4.4, Stormwater and Urban Runoff Pollution Control from the Los Angeles Municipal Code. The SWPPP shall meet the applicable provisions of Sections 301 and 402 of the CWA and Chapter 6 Article 4.4, Storm Water and Urban Runoff Pollution Control from the Los Angeles Municipal Code, by requiring controls of pollutant discharges that utilize best available technology economically achievable (BAT) and best conventional pollutant control technology (BCT) to reduce pollutants.

MM-GEO-3. The project applicant shall implement dust control measures consistent with SCAQMD Rule 403 – Fugitive Dust, during the construction phases of new project development.

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The following actions are currently recommended to implement Rule 403 and have been quantified by the SCAQMD as being able to reduce dust generation between 30 and 85 percent depending on the source of the dust generation:

 Apply water and/or approved nontoxic chemical soil stabilizers according to manufacturer’s specification to all inactive construction areas (previously graded areas that have been inactive for 10 or more days).

 Replace ground cover in disturbed areas as quickly as possible.

 Enclose, cover, water twice daily or apply approved chemical soil binders to exposed piles with 5 percent or greater silt content.

 Water active grading sites at least twice daily during construction activities.

 Suspend all excavating and grading operations when wind speeds (as instantaneous gusts) exceed 25 miles per hour over a 30-minute period.

 All trucks hauling dirt, sand, soil or other loose materials are to be covered or shall maintain at least 2 feet of freeboard (i.e., minimum vertical distance between top of the load and the top of the trailer), in accordance with Section 23114 of the California Vehicle Code.

 Sweep streets at the end of the day if visible soil material is carried over to adjacent roads.

 Install wheel washers or gravel construction entrances where vehicles enter and exit unpaved roads onto paved roads, or wash off trucks and any equipment leaving the site each trip.

 Post and enforce traffic speed limits of 15 miles per hour or less on all unpaved roads. e. Adverse Effects

The proposed project incorporates the City’s requirements pertaining to geologic hazards, including grading fill techniques and seismic safety. With the implementation of the mitigation measures recommended in this draft EIR to mitigate potentially significant impacts associated with geologic hazards and sedimentation and erosion, no significant adverse impacts would result from the construction and operation of the proposed Wilshire and La Brea Project.

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