IV. ENVIRONMENTAL IMPACT ANALYSIS E. GEOLOGY/SOILS

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1 IV. ENVIRONMENTAL IMPACT ANALYSIS E. GEOLOGY/SOILS The following discussion is based upon information contained in the Hollywood Redevelopment Plan Amendment EIR and a letter prepared by Geotechnologies, Inc. on January 31, 2006, titled Updated Supplement to Environmental Impact Report Soil and Geology Issues, Proposed Hollywood Gateway Development, Northeast Corner and Southeast Corner of Hollywood Boulevard and Argyle Avenue, Hollywood, California. A copy of this letter can be found in Appendix F of this document. PREVIOUS ENVIRONMENTAL ANALYSIS As discussed in Section 1.0, Introduction/Summary, the Hollywood Redevelopment Plan Amendment EIR addressed impacts associated with the development and redevelopment of properties within the boundaries of the Hollywood Redevelopment Area. The following summarizes the analyses and mitigation measures identified in that document with respect to geology and soils. It was determined that all impacts would be less than significant with the incorporation of the identified mitigation measures. Ground Rupture Active or potentially active faults known to exist in the vicinity of the Hollywood Redevelopment Area include the Verdugo Fault, Newport-Inglewood Fault and Whittier Fault. A segment of the Santa Monica-Hollywood Fault underlies the southeastern corner of the Hollywood Redevelopment Area. Projects located within a City designated Fault Rupture Study Zone would be subject to special projectspecific foundation and structural studies and imposition of structural design standards. With adherence to these standards, impacts related to fault rupture hazards would be less than significant. Ground Shaking The Hollywood Redevelopment Area could be subjected to strong groundshaking motions as a result of an earthquake occurring along one or more of the faults listed as well as other undiscovered faults that may be located in the region. While the area would be susceptible to strong groundshaking, there is no evidence to suggest that the severity of groundshaking would be greater at other locations in Southern California. Specific projects would be constructed in compliance with accepted engineering practices and current building codes to resist seismically generated motions. With adherence of these standards, specific projects would not expose people, property, or infrastructure to greater seismic impacts than already exist in southern California. Impacts related to groundshaking would be less than significant. Liquefaction The Hollywood Redevelopment Area includes areas with a high probability of liquefaction. Liquefaction of soils can cause damage to structures and utility lines, resulting in a significant impact. Specific projects located in areas subject to liquefaction would be required to undertake special liquefaction studies, incorporate foundation design features to reduce risks associated with liquefaction, and comply Page IV.E-1

2 with the requirements of the City building code with respect to design requirements in areas subject to liquefaction. Impacts related to liquefaction hazards would be less than significant. Subsidence While subsidence may have occurred during the 1950 s though the 1970 s as a result of groundwater withdrawal, the General Plan Framework Draft EIR indicates that potential for subsidence is not known to be present within the Hollywood Redevelopment Area. Therefore, no impacts related to subsidence are anticipated as a result of potential development projected to occur. Landslides Landslides are known to have occurred at the edges of the Hollywood Redevelopment Area. According to the Environmental and Facilities Maps published by the City of Los Angeles, the northwestern end of the Hollywood Redevelopment Area has a cluster of small shallow surficial landslides. Specific projects located within areas identified for potential landslide and slope hazards would be subject to design requirements set forth in the City Building Code. Impacts related to landslide hazards would be less than significant. Mitigation Measures The following mitigation measures were identified in the Hollywood Redevelopment Plan Amendment EIR as required: 1. Prior to the design and construction of a site-specific project, a comprehensive geotechnical investigation shall be performed. If liquefiable soils or soils subject to seismic settlement are found, appropriate site preparation and foundation design measures shall be included in the project design that would minimize the effects of the soil conditions on the integrity of proposed structures. The required measures would be dependent upon the specific site conditions encountered. The geotechnical analysis and design measures shall be reviewed and approved by the City of Los Angeles Department of Building and Safety prior to issuance of building permits for the project. 2. All structural elements shall be designed and built to resist strong ground motions in accordance with the requirements of the City Building Code. These measures shall be reviewed and approved by the City of Los Angeles Department of Building and Safety prior to issuance of building permits. 3. All projects located within areas designated by the City as subject to landslide and slope stability hazards shall include design features to address site-specific conditions as required by the City of Los Angeles Department of Building and Safety. Page IV.E-2

3 ENVIRONMENTAL SETTING The project site is located along both sides of Hollywood Boulevard between Argyle Avenue and El Centro Avenue. The project site is currently developed with commercial uses and parking lots. The project site is sloped with steeper slopes occurring at the northern end of the proposed development along Carlos Avenue. The Proposed Project would involves the removal of the existing uses and the construction of an approximately 1.13 million square foot mixed-use development. Geology and Soils The project site is located within the Hollywood Redevelopment Area, which has geologic formations that consist of older surficial deposits in the southern portion and bedrock units found in the Santa Monica Mountains in the northern portion. These include Mesozoic granitic rocks, Cretaceous sandy conglomerates, and Tertiary sedimentary rocks all surrounded by minor amounts of surficial deposits (alluvium and older alluvium). Soils present in the project area are predominately Hanford loam, with some pockets of Ramona loam at the base of the mountains and at the eastern edge of the project area. The bedrock is folded and tilted yielding a relatively complex geologic structure with bedding attitudes (strikes and dips) oriented in various directions. Scattered known and probable bedrock landslides are found mainly near the crest of the ranges, and on the south and east facing slopes. Essentially all of the bedrock area has slopes greater than 15%. Seismic Hazards The entire southern California area is considered a seismically active region. The region has numerous active, potentially active, and inactive faults. Active faults are defined as a fault that has had surface displacement within Holocene times (about the last 11,000 years). A potentially active fault is a fault that has demonstrated surface displacement of Quaternary age deposits (within the last 1.6 million years). Inactive faults have not moved in the last 1.6 million years. Major faults in the vicinity of the Hollywood area include: Newport-Inglewood, Hollywood, Elysian Park, Santa Monica, San Fernando, Raymond, Sierra Madre, Verdugo, Northridge and Palos Verdes. The City has designated approximately one-eighth mile wide Fault Rupture Study Zones on each side of identified active and potentially active faults to establish areas of particularly acute seismic hazard potential. The State Alquist-Priolo Special Studies Zone Act mitigates fault rupture hazards by prohibiting the location of most structures for human occupancy across the traces of active faults. No Alquist-Priolo Special Study Zones are located within the project site. The closest Alquist-Priolo Zone to the project site is associated with the Newport-Inglewood Fault, approximately five miles to the south. Landslides Landslides may be triggered by earthquakes, rainstorms, or construction-related activities (e.g., improper grading, structural design, landscaping, etc.). The project site is located within the Hollywood Redevelopment Area. According to the Los Angeles Citywide General Plan Framework Draft EIR, this Page IV.E-3

4 area is located in a portion of the City where the likelihood of landslides ranges from Not Known to be Present to High. The project site and the immediately surrounding area are completely paved with no areas of steep slopes. According to City of Los Angeles Zoning Information and Map Access System (ZIMAS), the project site is not located in an area at risk for on or off-site landslides. Liquefaction Liquefaction is the process in which loose granular soils below the groundwater table temporarily lose strength during strong ground shaking as a consequence of increased pore pressure and thereby, reduced effective stress. The vast majority of liquefaction hazards are associated with sandy soils and silty soils of low plasticity. Potentially liquefiable soils (based on composition) must be saturated or nearly saturated to be susceptible to liquefaction. Significant factors that affect liquefaction include water level, soil type, particle size and gradation, relative density, confining pressure, intensity of shaking, and duration of shaking. Liquefaction potential has been fond to be the greatest where the groundwater level is shallow and submerged loose, fine sands occur within a depth of about 50 feet or less. According to the ZIMAS, the project site is not in an area prone to liquefaction. 1 Subsidence and Expansive Soils Subsidence is the downward settling of the earth s surface as a result of fluid withdrawal from deep geologic formations. Unless these voids are refilled, they may collapse causing subsidence in the shallower earth layers between the ground surface and the pumped geologic units. Several inches of subsidence was reported to have occurred during the 1950s to 1970s due to groundwater pumping in the area around Vine between Sunset Boulevard and Santa Monica Boulevard. However, according to the Los Angeles Citywide General Plan Framework Draft EIR hazards associated with subsidence are not known to be present in this area. ENVIRONMENTAL IMPACTS Thresholds of Significance The Proposed Project would result in a significant impact if it exposes people or structures to potential substantial adverse effects, including the risk of loss, injury or death involving: 1) rupture of a known earthquake fault, as delineated on the most recent Alquist-Priolo Earthquake Fault Zoning Map issued by the State Geologist for the area or based on other substantial evidence of a known fault or strong seismic ground shaking; 2) seismic-related ground failure, including liquefaction; 3) ground failure related to subsidence or 4) seismically-induced landslides. 1 November 29, Page IV.E-4

5 A project would normally have a significant geologic hazard impact if it would cause or accelerate geologic hazards, which would result in substantial damage to structures or infrastructure, or expose people to substantial risk of injury. Project Impacts Erosion The project site is currently developed with commercial uses and parking lots. Almost the entire area is covered with imperious surfaces. These uses would be removed during development of the Proposed Project. During construction activities, particularly during excavation for the subterranean levels and grading, the amount of impervious surfaces would be reduced, increasing the potential for wind-borne erosion. Additionally, there is a potential for erosion to occur during the grading process during periods of heavy precipitation. Regulatory measures are required to be implemented during construction periods to minimize wind and water-borne erosion (see Sections IV.C, Air Quality, and IV.G, Hydrology and Water Quality). With implementation of these measures as required by existing law and regulation, impacts related to erosion would be less than significant. Surface Fault Rupture and Ground Shaking The project site does not contain any known surface fault traces. The area of the City of Los Angeles in which the project site is located does not contain any Alquist-Priolo Earthquake Fault Zones. Therefore, the project site is not located within an established Alquist-Priolo Earthquake Fault Zone for surface fault rupture hazards. As noted above, closest Alquist-Priolo Earthquake Fault Zone, established for the Newport-Inglewood Fault, is located approximately 5 miles south of the project site. Therefore, the likelihood of a surface fault rupture affecting the project site is low. No active or potentially active faults are known to lie beneath the Proposed Project. However, the project site is located against a small topographic rise to the north, which is considered to be a fault scarp for the Hollywood Fault. The fault dips to the north and therefore, does not underlie the site. Therefore, with incorporation of the mitigation measures identified in below, impacts would be less than significant. The project site is located within the Southern California region that is known for its seismic activity. Additionally, the location of the project site relative to known active or potentially active faults indicates that it could be subjected to significant ground shaking. The State of California Building Code with local amendments regulates the design of buildings to resist gravity forces, to minimize fire hazards and to resist forces generated by winds and major earthquakes. Compliance with the State of California Building Code, with its local amendments, would ensure that potential seismic and ground-shaking impacts associated with the proposed development would be less than significant. Page IV.E-5

6 Landslides The project site does not contain any landslides and no landslides exist in the immediate vicinity. According to ZIMAS, the project site is not located in an area prone to landslides. Additionally, the Proposed Project would be subject to the design requirements set forth in the State of California Building Code, with local amendments. Therefore, impacts related to landslide hazards would be less than significant. Liquefaction, Subsidence, and Expansive Soils According to ZIMAS, the project site is not located in an area that is prone to liquefaction hazards. Furthermore, compliance with the State of California Building Code, with local amendments, which regulates the design of buildings and foundations, would further reduce liquefaction impacts on the project site. Therefore, development of the Proposed Project would not expose people to significant liquefaction impacts such as seismic settlement and differential compaction. No subsidence associated with fluid withdrawal, peat oxidation, or hydrocompaction is known to have occurred on or in the vicinity of the project site. Therefore, development of the Proposed Project would not result or expose people to significant impacts related to subsidence. The soils underlying the project site are not known to have any significant expansion potential. However, as of this time a complete geotechnical evaluation of the project site has not been completed. If during the course of the geotechnical investigation, it is determined that the soils have significant expansive properties, recommendations will be included to address the issue. The Proposed Project would comply with all recommendations contained in the geotechnical report and requirements of the California Building Code. Therefore, impacts with respect to expansive soils would be less than significant. Subsurface exploration has yet to be performed for the project site. After laboratory testing and engineering analysis, conclusions regarding seismic related ground failure, including liquefaction, landslides, lateral spreading, subsidence, or collapse will be presented. Based on information currently available, the proposed construction will not cause, or increase the potential for any seismic related ground failure on the subject site or adjacent sites. CUMULATIVE IMPACTS Development of the Proposed Project in conjunction with the related projects listed in Section III.B would result in further infilling of various land uses in the City of Los Angeles. Geotechnical hazards are sitespecific and there is little, if any, cumulative relationship between development of the Proposed Project and the related projects. As such, construction of the related projects is not anticipated to combine with the Proposed Project to cumulatively expose people or structures to such geologic hazards as earthquakes, ground shaking, liquefaction, landslides, and/unstable soils, expansion soils, or result in substantial soil erosion or the loss of topsoil. Therefore, no cumulatively considerable geological impacts are anticipated from the Proposed Project and the related projects. Page IV.E-6

7 MITIGATION MEASURES The mitigation measures identified in the Hollywood Redevelopment Plan Amendment EIR are applicable to Proposed Project and shall be required, as listed below. E-1 Prior to the design and construction of the Proposed Project, a comprehensive geotechnical investigation shall be performed. If liquefiable soils or soils subject to seismic settlement are found, appropriate site preparation and foundation design measures shall be included in the project design that would minimize the effects of the soil conditions on the integrity of proposed structures. The geotechnical analysis and design measures shall be reviewed and approved by the City of Los Angeles Department of Building and Safety prior to issuance of building permits for the project. E-2 All structural elements shall be designed and built to resist strong ground motions in accordance with the requirements of the City Building Code. These measures shall be reviewed and approved by the City of Los Angeles Department of Building and Safety prior to issuance of building permits. LEVEL OF SIGNIFICANCE AFTER MITIGATION All geotechnical and seismic impacts would be less than significant. Page IV.E-7