IV. ENVIRONMENTAL IMPACT ANALYSIS E. GEOLOGY/SOILS Except where otherwise noted, the following Section is based on the Preliminary Geotechnical Investigation, Proposed Medical Office Buildings and Mixed-Use Development, 12333 Olympic Boulevard and 1901 to 1933 Bundy Drive, Los Angeles, California (the Preliminary Geotechnical Investigation ) prepared by Geotechnologies, Inc., dated February 7, 2007. In addition, this Section is also based on a more recent report entitled Geotechnical Engineering Investigation, Proposed Medical Park 12333 Olympic Boulevard and 1901 to 1903 Bundy Drive, Los Angeles, California (the Geotechnical Investigation ). A copy of both reports can be found as Appendix D to this Draft EIR. ENVIRONMENTAL SETTING Geologic Conditions and Topography The project site is located in the extreme southern end of the Transverse Ranges Geomorphic Province, characterized by roughly east-west trending mountains with northern and southern boundaries formed by faults. Within the Transverse Ranges, the project site is located in the Los Angeles Basin, which is generally located at the northern end of the Peninsular Ranges Geomorphic Province. The basin is bounded to the east and southeast by the Santa Ana Mountains and San Joaquin Hills, and to the northwest by the Santa Monica Mountains. Previous reports observed the project site s topographic elevation to be approximately 162 feet above mean sea level (msl) with a slight south southwesterly slope. 1 The United States Geological Survey (USGS) topographic quadrangle for the region shows the project site elevation sloping southwest from approximately 160 to 155 feet above mean sea level (msl). 2 The nearest open body of water to the project site is the Pacific Ocean, which is located approximately 2.5 miles west of the project site. Soil Conditions As part of the Preliminary Geotechnical Investigation, two exploratory borings were drilled at the project site to a depth of 30 and 50 feet, respectively. Results of these borings show that, up to a depth of 1.0 to 1.5 feet below ground surface (bgs), the project site is underlain by fill materials including clayey silt and clayey sand which are brown to dark brown; moist; medium dense to medium stiff; fine grained; and contain occasional gravel. Beneath the fill materials are native soils consisting of silt, clay, and sand, ranging from light gray to brown, moist to wet, medium dense to very dense, and containing varying 1 2 Environmental Resources Management, Phase I Environmental Site Assessment, Westside Medical Park, 1901, 1925, 1933 South Bundy Drive, Los Angeles, California, September 2004. United States Department of the Interior, United States Geological Survey, Beverly Hills Quadrangle, California-Los Angeles Co, 7.5 Minute Series (Topographic), 1995. Page IV.E-1
amounts of gravel. These native soils are underlain by younger alluvial materials. Similar soil conditions were discovered during exploration conducted as part of previous Phase II subsurface investigations which involved drilling up to approximately 40 feet bgs (see Section IV.F, Hazards and Hazardous Materials, and Appendix E to this Draft EIR). These previous borings also showed the project site to be underlain by alternating layers of silty to clayey sands and sands with gravel to a depth of approximately 35 to 40 feet bgs, at which depth a confining layer of clayey silt was encountered. 3 These soils are underlain by marine and non-marine terrace deposits of the Lakewood Formation. 4 Groundwater and Stormwater During the exploratory borings conducted as part of the Preliminary Geotechnical Investigation, groundwater was encountered at a maximum depth of approximately 37 feet bgs. This is consistent with previous borings conducted at the project site, which encountered groundwater at depths ranging between approximately 33 and 44 feet bgs. 5,6 Based on mapping provided by the U.S. Geological Survey, the historical high groundwater level in the project area is between 30 and 40 feet bgs. 7 The project site is almost entirely covered with impermeable surfaces. Storm water from the project site is gravity-fed via a man-made engineered slope which drains towards the south, where stormwater enters catch basins within a paved surface parking lot and is directed to off-site City of Los Angeles municipal storm drains in Bundy Drive. 8 Seismic Hazards The entire Southern California area is considered to be a seismically active region. The region has numerous active, potentially active, and inactive faults. According to California Division of Mines and 3 4 5 6 7 8 Environmental Resources Management, Phase II Site Investigation Report, Westside Medical Park, West Los Angeles, California, September 9, 2004. Environmental Resources Management, Phase I Environmental Site Assessment, Westside Medical Park, 1901, 1925, 1933 South Bundy Drive, Los Angeles, California, September 2004. Ibid. Environmental Resources Management, Phase II Site Investigation Report, Westside Medical Park, West Los Angeles, California, September 9, 2004. U.S. Geological Survey, Historical Highest Ground Water Contours and Borehole Log Data Locations, Beverly Hills Quadrangle, 30 x 60 minute series, 2002. Environmental Resources Management, Phase II Site Investigation Report, Westside Medical Park, West Los Angeles, California, September 9, 2004. Page IV.E-2
Geology, now known as California Geologic Survey (CGS), an active fault is defined as a fault that has had a 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). Buried thrust faults are faults without a surface expression but are a significant source of seismic activity. Due to the buried nature of these thrust faults, there existence is usually not known until they produce an earthquake. However, the seismic risk of these buried faults is believed to be low. According to the City of Los Angeles Safety Element, the project site is not located within an Alquist- Priolo Special Study Zone Area or Fault Rupture Study Area. However, the project site is located immediately adjacent to an identified Fault Rupture Study Area located east of Bundy Drive and south of Olympic Boulevard. 9 According to the Geotechnical Investigation the South Branch of the Santa Monica Fault underlies the project site near Olympic Boulevard and may underlie the project site near Building D. While some geologists consider the Santa Monica Fault to be active, it has not been designated as an active fault by the State of California. Surface Fault Rupture Ground rupture is defined as surface displacement which occurs along the surface trace of the causative fault during an earthquake. According to the Geotechnical Investigation, no known active or potentially active faults underlie the project site. In addition, the project site is not located within an active Alquist- Priolo Earthquake Fault Zone. Therefore, the potential for surface ground rupture at the project site is considered to be low. Ground Shaking The Preliminary Geotechnical Investigation included modeling to determine the potential for seismicrelated ground motion at the project site. The deterministic model showed that the largest estimated earthquake acceleration experienced at the project site would be a magnitude 6.6 event along the Santa Monica Fault. Ground Failure and Liquefaction Liquefaction is a process by which water-saturated unconsolidated sediments lose their strength due to increased pore pressure during or after an earthquake. Liquefaction potential is greatest where the groundwater level is shallow, and loose, fine sands occur within a depth of about 50 feet. Liquefaction potential decreases as grain size and clay and gravel content increase. Liquefaction potential increases as ground acceleration and shaking increases during earthquakes. According to the City of Los Angeles 9 City of Los Angeles, Safety Element of the General Plan, Exhibit A: Alquist-Priolo Special Study Zones & Fault Rupture Study Areas in the City of Los Angeles, March 1994. Page IV.E-3
Safety Element, the project site is not located within a liquefaction hazard area. 10 However, CGS shows approximately the southern half of the project site within a liquefaction area. 11 Based on this designation and because the historic high groundwater level at the project site is approximately 30 feet below grade, a liquefaction analysis was conducted as part of the Geotechnical Investigation. This analysis showed that soils underlying the project site would not be considered prone to liquefaction during the ground motion expected during the design based earthquake. Earthquake-induced volumetric strain and dissipation of pore pressure in saturated silts and sands after liquefaction can result in settlement. Soil settlement is most likely after a major earthquake when a site is underlain by dry, loose, sandy soils. The Geotechnical Investigation concluded that the medium dense to very dense clay, silt, and sand underlying the project site would not be considered prone to dynamic settlement. Soil Stability (Landslide, Spreading, Subsidence, Liquefaction, or Collapse) Landslides may occur when a site is located on or in the vicinity of hillside areas. Similarly, free-faces or slopes generally contribute to lateral spreading. The project site is not mapped by the City of Los Angeles as within a Landslide Inventory or Hillside Area. 12 The USGS shows the project site elevation sloping southwest from approximately 160 to 155 feet above msl. 13 This is confirmed by visual observation of the project site which shows it to be generally flat and, furthermore, not located in the vicinity of any hills or slopes. Subsidence is a localized mass movement that involves the gradual downward settling or sinking of the ground, resulting from the extraction of mineral resources, subsurface oil, groundwater, or other subsurface liquids, such as natural gas. The project site is not located within a City-designated oil field or oil drilling area, or a City-designated Mineral Resource Zone 2 Area (MRZ-2). 14 Furthermore, research shows that the project site was primarily used for agriculture from as early as 1902 through the late 10 11 12 13 14 City of Los Angeles Department of City Planning, Safety Element of the General Plan, Exhibit B: Areas Susceptible to Liquefaction in the City of Los Angeles, 1995. State of California, Division of Mines and Geology, Seismic Hazard Zone Map, Beverly Hills Quadrangle, 1997. (See Geotechnical Investigation provided as Appendix D to this Draft EIR.) City of Los Angeles Department of City Planning, Safety Element of the General Plan, Exhibit C: Landslide Inventory and Hillside Areas in the City of Los Angeles, June 1994. United States Department of the Interior, United States Geological Survey, Beverly Hills Quadrangle, California-Los Angeles Co, 7.5 Minute Series (Topographic), 1995. City of Los Angeles Department of City Planning, Safety Element of the General Plan, Exhibit E: Oil Fields and Oil Drilling Areas in the City of Los Angeles, May 1994. Page IV.E-4
1940s/early 1950s when the existing on-site manufacturing and office structures were constructed. The project site is not known to have been used historically for extraction of mineral resources, subsurface oil, groundwater, natural gas, or other subsurface liquids. 15,16 The nearest open body of water to the project site is the Pacific Ocean, which is located approximately 2.5 miles west of the project site. Liquefaction is most likely after a major earthquake when the groundwater level is shallow and loose, fine sands occur at a site. As discussed previously, the project site is not identified by the City to be located within a liquefaction hazard area. 17 However, the State has indicated that approximately half of the project site is within a liquefaction area. 18 Nonetheless, the liquefaction analysis conducted for the project site showed that soils underlying the project site would not be considered prone to liquefaction. Collapse of structures could occur if a proposed development were not constructed in accordance with local and State building standards, as well as other site-specific recommendations. Applicable building requirements include the 2001 California Building Code with City of Los Angeles Amendments, the City s Planning and Zoning Code (Chapter I of the Los Angeles Municipal Code), as well as site-specific recommendations of the City s Department of Building and Safety. Conditions affecting the stability of a proposed development may include the proposed depth of excavation, nature of soils underlying a proposed development site, and proximity of adjacent structures. Expansive Soils Soils in the project area consist of sandy loams and loamy sands, which have a low to moderate expansion hazard potential. The Geotechnical Investigation included an analysis of soils at the project site which showed soils to be in the very low to low expansion range. 15 16 17 18 Environmental Resources Management, Phase I Environmental Site Assessment, Westside Medical Park, 1901, 1925, 1933 South Bundy Drive, Los Angeles, California, September 2004; Glenfos, Inc., Preliminary Site Assessment Report, 12333 West Olympic Boulevard and 1901, 1925 & 1933 Bundy Drive, AGI Properties, Inc., Los Angeles, CA 90064, June 26, 1995. (See Appendix E to this Draft EIR.) Christopher A. Joseph & Associates, Historic Report, December 2006. (See Appendix B to this Draft EIR.) City of Los Angeles Department of City Planning, Safety Element of the General Plan, Exhibit B: Areas Susceptible to Liquefaction in the City of Los Angeles, 1995. State of California, Division of Mines and Geology, Seismic Hazard Zone Map, Beverly Hills Quadrangle, 1997. (See Geotechnical Investigation in Appendix D.) Page IV.E-5
ENVIRONMENTAL IMPACTS Thresholds of Significance In accordance with Appendix G to the State CEQA Guidelines, a project would have a significant effect if it would: (a) Expose people or structures to potential substantial adverse effects, including the risk of loss, injury, or death involving: i) Rupture of a known earthquake fault, as delineated on the most recent Alquist-Priolo Earthquake Fault Zoning Map or based on other substantial evidence of a known fault? ii) Strong seismic ground shaking? iii) Seismic-related ground failure, including liquefaction? iv) Landslides? (b) Result in substantial soil erosion or the loss of topsoil? (c) Be located on a geologic unit or soil that is unstable, or that would become unstable as a result of the project, and potentially result in on- or off-site landslide, lateral spreading, subsidence, liquefaction, or collapse? (d) Be located on expansive soil, as defined in Table 18-1-B of the Uniform Building Code (1994), creating substantial risks to life or property? (e) Have soils incapable of adequately supporting the use of septic tanks or alternative waste water disposal systems where sewers are not available for the disposal of waste water? As discussed in Section IV.A (Impacts Less Than Significant) of this Draft EIR, the proposed project would have no impact with respect to Thresholds (a)(iv), (b), and (e) listed above. As such, no further analysis of these topics is required. Based on the City of Los Angeles L.A. CEQA Thresholds Guide, the proposed project would also result in a significant geotechnical impact if it exceeds any of the following thresholds: (a) 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; (b) It would constitute a geologic hazard to other properties by causing or accelerating instability from erosion; Page IV.E-6
(c) It would 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; or (d) One or more distinct and prominent geologic or topographic features would be destroyed, permanently covered or materially and adversely modified. Such features may include, but are not limited to, hilltops, ridges, hillslopes, canyons, ravines, rock outcrops, water bodies, streambeds and wetlands. As the proposed project was determined to have no soil erosion and loss of topsoil impact under Threshold (b) from Appendix G to the State CEQA Guidelines (see Section IV.A of this Draft EIR), the proposed project would likewise have no erosion impacts with respect to Thresholds (b) and (c), above, from the L.A. CEQA Thresholds Guide. As discussed in Section IV.A, the project site does not contain any geologic resources such as rock outcroppings. Furthermore, and as described in the Environmental Setting of this Section, the project site does not contain and is not nearby any hilltops, ridges, hillslopes, canyons, ravines, water bodies, streambeds or wetlands. As such, the proposed project would have no impact with respect to Threshold (d), above. Geologic hazards (i.e., Threshold (a), above) are discussed throughout the Project Impacts discussion on the following pages. Project Impacts Seismic Hazards Surface Fault Rupture The project site is located in the seismically active region of Southern California. Numerous active and potentially active faults with surface expressions (fault traces) have been mapped adjacent to, within, and beneath the City of Los Angeles. As discussed previously in this Section, the project site is not located within an Alquist-Priolo Special Study Zone Area or Fault Rupture Study Area. The South Branch of the Santa Monica Fault underlies the project site near proposed Building D; however, this fault is not considered to be active by the State of California. Moreover, the proposed project would comply with local and State regulations regarding seismic design, including the CGS Special Publications 117, Guidelines for Evaluating and Mitigating Seismic Hazards in California (1997), which provides guidance for the evaluation and mitigation of earthquake-related hazards. Therefore, as the potential for surface fault rupture at the project site is remote and the proposed project would be constructed in accordance with standard seismic requirements, the proposed project would result in a less-than-significant impact with respect to exposure of people or property to hazardous conditions resulting from rupture of a known earthquake fault. Ground Shaking The principal seismic hazard to the proposed project is strong ground shaking from earthquakes produced by local faults. Modern, well-constructed buildings are designed to resist ground shaking through the use Page IV.E-7
of shear walls and reinforcements. The proposed construction would be consistent with all applicable provisions of the City of Los Angeles Building Code, as well as the seismic design criteria contained within the Uniform Building Code. Although the project site is located within approximately 2.1 miles of the active Santa Monica Fault, and is within 60 miles of several other active faults on a regional level, the potential seismic hazard to the proposed project site would not be higher than in most areas of the City of Los Angeles or elsewhere in the region. Therefore, as the proposed project would be constructed in accordance with standard seismic requirements, the proposed project would result in a less-thansignificant impact with respect to exposure of people or property to hazardous conditions resulting from strong seismic ground shaking. Ground Failure and Liquefaction As discussed previously in this Section, the project site is not located within an area prone to liquefaction. Furthermore, an analysis of soils at the project site showed that these soils would not be prone to liquefaction. Therefore, the proposed project would result in a less-than-significant impact with respect to exposure of people or property to hazardous conditions resulting from liquefaction during a seismic event. The Geotechnical Investigation concluded that the medium dense to very dense clay, silt, and sand at the project site would not be considered prone to dynamic settlement during an earthquake. Therefore, the proposed project would result in a less-than-significant impact with respect to exposure of people or property to hazardous conditions resulting from dynamic settlement during a seismic event. Soil Stability (Landslide, Spreading, Subsidence, Liquefaction, or Collapse) With respect to landslides, the topography at the project site is relatively flat and the site is not located near any foothills or mountains. Therefore, the possibility of landslides occurring on the project site is minimal. Since the project site does not contain free-faces or slopes, the potential for lateral spreading to occur is low. As the project site is not known to have been used for extraction of mineral resources, subsurface oil, groundwater, natural gas, or other subsurface liquids, there is low potential for subsidence at the project site. As stated previously, an analysis of soils at the project site showed that these soils would not be prone to liquefaction. Therefore, the proposed project would not result in a significant soil stability impact with respect to any of the following: landslides, lateral spreading, subsidence, or liquefaction. With respect to collapse, based on the explorations, laboratory testing, and research conducted, the Geotechnical Investigation concluded that the proposed project would be feasible from a geotechnical standpoint. However, several conditions present at the project site may influence the proposed construction, such as the presence of fill materials from 1.0 to 1.5 feet bgs that would need to be removed prior to new construction, and the proposed depth of excavation (i.e., approximately 15 feet in vertical height), nature of on-site soils, and proximity of adjacent structures that may demand shoring measures in the proposed excavations. As such, prior to mitigation, the proposed project could result in a potentially significant soil stability impact related to collapse. Page IV.E-8
The proposed project would be required to be constructed in accordance with City of Los Angeles building regulations including the 2001 California Building Code with City of Los Angeles Amendments, the City s Planning and Zoning Code (Chapter I of the Los Angeles Municipal Code), as well any sitespecific recommendations of the City s Department of Building and Safety. In addition, to ensure the stability and safety of the proposed development, the Geotechnical Investigation (see Appendix D to this Draft EIR) includes site-specific construction recommendations including, but not limited to, those pertaining to: soil compaction requirements, reuse of soil and use of import materials, construction of retaining walls, disposal of stormwater, allowable bearing values, allowable friction coefficients, concrete slab design, shoring and lagging measures, and monitoring by a competent professional. Conformance with standard City building requirements along with the implementation of all recommendations set forth in the Geotechnical Investigation for the proposed project, as re-stated in the mitigation measures identified in this Section, would ensure that any project impacts related to collapse would be reduced to a less-than-significant level. Expansive Soils The Geotechnical Investigation included an analysis of soils at the project site, which were shown to be in the very low to low expansion range. The Geotechnical Investigation concluded that conformance with the minimum City of Los Angeles reinforcement requirements for foundations and slabs would adequately address this level of expansiveness. As such, impacts associated with expansive soils would be less than significant. CUMULATIVE IMPACTS Construction of the identified related projects and other future development may introduce new sitespecific hazards to the project area including those related to seismic events (e.g., surface fault rupture, ground-shaking, liquefaction, landslides) as well as soil conditions (e.g., erosion, expansiveness, subsidence, lateral spreading, collapse). Such impacts would be directly related to the conditions present at each individual related project site and the specific characteristics of each related project. Therefore, impacts would not generally combine between related projects nor combine with impacts of the proposed project. Furthermore, like the proposed project, the development of each of the related projects would be subject to uniform City and State construction standards designed to protect public safety as well as structures. Therefore, the proposed project would not combine with the related projects to create a cumulative impact to geology or soils and cumulative impacts would be less than significant. MITIGATION MEASURES The following mitigation measures are recommended to address the proposed project s geology and soils impacts with respect to soil stability: (E-1) Construction of the proposed project shall comply with recommendations set forth in the Preliminary Geotechnical Investigation, Proposed Medical Office Buildings and Mixed-Use Page IV.E-9
Development, 12333 Olympic Boulevard and 1901 to 1933 Bundy Drive, Los Angeles, California prepared by Geotechnologies, Inc., dated February 7, 2007 and the Geotechnical Engineering Investigation, Proposed Medical Park 12333 Olympic Boulevard and 1901 to 1933 Bundy Drive, Los Angeles, California prepared by Geotechnologies, Inc., dated May 23, 2008 (see also Appendix D to this Draft EIR) to the extent feasible. LEVEL OF SIGNIFICANCE AFTER MITIGATION The proposed project s impacts associated with geology and soils (soil instability) would be less than significant with the implementation of the mitigation measures listed above. The proposed project would not result in substantial adverse effects related to seismic hazards or expansive soils and, therefore, would have less-than-significant impacts. Page IV.E-10