IV. ENVIRONMENTAL IMPACT ANALYSIS E. GEOLOGY AND SOILS

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1 IV. ENVIRONMENTAL IMPACT ANALYSIS E. GEOLOGY AND SOILS INTRODUCTION This section of the (Draft EIR) evaluates potential geology and soils impacts associated with development of the proposed (proposed Project or Project). The analysis in this section is based primarily on the following technical report: Update Geotechnical Engineering Report, Proposed Five (5) Story Structure with Two (2) Levels of Subterranean Parking, S. La Cienega Boulevard, Los Angeles, California prepared by CalWest Geotechnical Consulting Engineers a division of LC Engineering Group, Inc. on April 15, This technical report is herein referred to as the Geotechnical Report and a complete copy is included in Appendix F of this Draft EIR. Previous geotechnical studies were prepared by CalWest Geotechnical, for the southern portion of the Project site ( South La Cienega Boulevard) in December Geotechnical studies for a previously proposed development for the northern portion of the Project site ( South La Cienega Boulevard) were prepared by West Coast Geotechnical and CalWest Geotechnical in 2004 and 2006, respectively. The 2004 West Coast Geotechnical Report and the 2006 CalWest Geotechnical Report were submitted, reviewed and approved, and are on file at the City of Los Angeles Department of Building and Safety. The boring logs, laboratory results and findings of the previous geotechnical studies are referenced in the April 15, 2008 Geotechnical Report and are subsequently also found in Appendix F of this Draft EIR. ENVIRONMENTAL SETTING Regional and Local Setting The Project site is located in the northern portion of the Peninsular Ranges geomorphic province of southern California. The Peninsular Ranges is one of the largest geologic areas in western North America and extends from the Los Angeles Basin south into Mexico to the tip of Baja California. The province is characterized by northwest trending mountain ranges and valleys, subparallel to the San Andreas Fault. In general, the Peninsular Ranges are underlain by Mesozoic granitic rocks derived from the same massive batholith which forms the core of the Sierra Nevada Mountains. Faults dominate the structure of the range. As discussed in Section III, Project Description, of this Draft EIR, the Project site is located in the City of Los Angeles (City) at 1022 to 1054 South La Cienega Boulevard, between West Olympic Boulevard and Whitworth Drive (refer to Figure II-1, Regional and Project Vicinity Map). It is approximately 1.2 acres in extent and is comprised of four relatively level parcels (APNs: , , , and ). The Project site is in an area that previously served as a natural flood plane, hence the street name La Cienega which means The Marsh in Spanish. Currently, the northern Page IV.E-1

2 portion of the Project site is vacant, but was previously occupied by a variety of commercial and retail uses, including an automobile repair shop and a billboard. The southern portion of the Project site is occupied by a two-story, 36-unit apartment complex, including an open center with a swimming pool and lounge area for the residents, as well as a surface parking lot (refer to Figure II-2, Aerial Photograph). Subsurface Conditions As described in the Geotechnical Report, subsurface conditions on the Project site consist of alluvial terrace deposits and shallow groundwater levels. These conditions are discussed in more detail below. Alluvial Deposits Alluvial terrace deposits were encountered during soil borings on the site in November 2004 and December 2006 to depths of up to approximately 50 feet. The alluvium generally consisted of grayish brown to dark gray silty clay and sandy clay that is moist and stiff. Groundwater Groundwater was encountered at a depth of approximately 17 to 17.5 feet below existing grade during soil borings on the site in November 2004 and December However, the groundwater level is projected to fluctuate with seasonal variations and other indeterminate factors. The highest historic groundwater depth based on the Seismic Hazard Report for the Beverly Hills and Hollywood Quadrangles is approximately 13 feet below existing grade. Seismic Conditions Faulting The Project site is located in the seismically active region of southern California. The numerous faults in the region include active, potentially active, and inactive faults. These major groups are based on criteria developed by the California Geological Survey (CGS), formerly known as the California Division of Mines and Geology, for the Alquist-Priolo Earthquake Fault Zoning Program. By definition, an active fault is one 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 during Quaternary time (the last 1.6 million years). Inactive faults have not moved in the last 1.6 million years. Earthquake Fault Zones, formerly known as Special Studies Zones, have been established along active known faults in California in accordance with the Alquist-Priolo Earthquake Fault Zoning Act (Act) passed in The main purpose of this Act is to prevent the construction of buildings used for human occupancy on the surface trace of active faults. The Act only addresses the hazard of surface fault rupture and is not directed toward other earthquake hazards. The Seismic Hazard Mapping Act, passed in 1990, addresses non-surface fault rupture earthquake hazards, including liquefaction and seismically induced landslides. Page IV.E-2

3 Fault Rupture Ground surface rupture results when the movement along a fault is sufficient to cause a gap or break along the upper edge of the fault zone on the surface. Damage due to surface rupturing is limited to the actual location of the fault line break, unlike damage from ground shaking, which can occur at great distances from the fault. As shown on Figure IV.E-1, the Project site is not located within an Alquist- Priolo Earthquake Fault Zone, and no active faults are known to underlie the Project site. 1 Therefore, surface rupture is not expected to affect the Project site. Active Faults The nearest known active surface fault is the Santa Monica Fault, which is located approximately 2 miles from the Project site. Other nearby active faults are the Hollywood Fault and the Newport-Inglewood Fault Zone located approximately 2.5 miles north, 2 miles south-southwest, respectively (see Figure IV.E- 1). The active San Andreas Fault Zone is located approximately 36 miles north of the Project site. Ground Shaking Ground motion is generated during an earthquake as two blocks of the Earth s crust slip past each other. In general, ground motion is greatest near the epicenter, increases with increasing magnitude, and decreases with increasing distance. However, the ground motion measured at a given site is influenced by a number of criteria, including depth of the epicenter, proximity to the projected or actual fault rupture, fault mechanism, duration of shaking, local geologic structure, source direction of the earthquake, underlying earth material, and topography. Earthquake magnitude is a quantitative measure of the strength of an earthquake or the strain energy released by it, as determined by seismographic or geologic observations. Earthquake intensity is a qualitative measure of the effects a given earthquake has on people, structures, or objects, which varies to place to place within the area affected by the earthquake. Earthquake magnitude is measured on the Richter scale or as moment magnitude, and intensity is described by the Modified Mercalli intensity scale. A related form of measurement is peak ground acceleration, which is a measure of ground-shaking during an earthquake. Peak ground acceleration values are reported in units of gravity (g). Structures founded on thick soft soil deposits are more likely to experience more destructive shaking, with higher amplitude and lower frequency, than structures founded on bedrock. In addition, thick soft soil deposits at far distances from earthquake epicenters may result in seismic accelerations significantly greater than expected in bedrock. As a general rule, the severity of ground shaking increases with proximity to the epicenter of the earthquake. Ground shaking is a seismic hazard that can cause damage to structures. As described above, several faults exist within close proximity of the Project site. As such, the Project site could be subjected to 1 City of Los Angeles Department of City Planning: Zone Information and Map Access System [web application]. Available: (Accessed: March 21, 2008). Page IV.E-3

4 moderate to severe ground shaking in the event of a major earthquake on any of the faults referenced above or other faults in Southern California. However, the risk of hazard associated with ground shaking at the Project site is comparable to the risk experienced in the Project area in general. Liquefaction Soil liquefaction, the condition in which soils below the groundwater table temporarily lose their solid state, results from loss of strength during cyclic loading, such as that imposed by earthquakes. When seismic ground shaking occurs, the soil is subject to seismic shear stresses that may cause the soil to undergo deformations or changed appearance. If the soil undergoes virtually unlimited deformation without developing significant resistance, it is said to have liquefied or been made into liquid. When soils consolidate during and following liquefaction, ground settlement occurs. Soils most susceptible to liquefaction are clean, loose, saturated, uniformly graded, and fine-grained sands. Shallow groundwater is considered a factor, amongst others, as it creates the saturated condition of the soil. In compliance with the Seismic Hazard Mapping Act, the CGS has mapped areas prone to liquefaction. According to the CGS, as illustrated on Figure IV.E-2, Liquifaction Hazard Zone Map, the Project site lies in an area of potential liquefaction hazard. 2 Generally, materials with a fine fraction content (i.e., mm) greater than 15 percent with a liquid limit below 35 percent, or a natural water content of greater than 0.9 times the liquid limit are considered exempt of liquefaction. The grain size distributions on the Project site display well graded material with abundant fine fraction content and as such the Project site is considered exempt of liquefaction. Landslides Steep slopes, shallow soil development, excess water, and lack of shear strength in an area can result in slope instabilities and landslides. Ground shaking during an earthquake may lead to seismically induced landslides, but most slides result from the weight of rain saturated soil and rock exceeding the shear strength of the underlying material. As illustrated on Figure IV.E-3, Landslide Hazard Zone Map, there are no portions of the Project site mapped by the CGS in accordance with the Seismic Hazard Mapping Act as a seismically-induced landslide hazard area. 3 Further, the probability of seismically-induced landslides affecting the Project site is considered to be remote, due to the relatively flat nature of the site and surrounding area. 2 3 City of Los Angeles Department of City Planning: Zone Information and Map Access System [web application]. Available: (Accessed: March 21, 2008). City of Los Angeles Department of City Planning: Zone Information and Map Access System [web application]. Available: (Accessed: March 21, 2008). Page IV.E-4

5 Hollywood Fault Santa Monica Fault Project Site Newport-Inglewood Fault Zone Newport-Inglewood Fault Zone Legend Major Fault Alquist-Priolo Fault Zone Source: California Geological Survey, ESRI Streetmap, County of Los Angeles and Christopher A. Joseph & Associates; May Miles Figure IV.E-1 Major Faults and Alquist-Priolo Fault Zones

6 Project Site Legend Liquefaction Hazard Zone Source: California Department of Conservation: Seizmic Hazard Zonation Program, ESRI Streetmap, County of Los Angeles and Christopher A. Joseph & Associates; May ,500 2,250 3,000 Feet Figure IV.E-2 Liquefaction Hazard Zone Map

7 Project Site Legend Landslide Hazard Zone Source: California Department of Conservation: Seizmic Hazard Zonation Program, ESRI Streetmap, County of Los Angeles and Christopher A. Joseph & Associates; May ,000 2,000 3,000 4,000 Feet Figure IV.E-3 Landslide Hazard Zone Map

8 Lateral Spreading Lateral spreading typically occurs as a form of horizontal displacement of relatively flat-lying alluvial material toward an open or free face such as an open body of water, channel, or excavation. Generally in soils, this movement is due to failure along a weak plane, and may often be associated with liquefaction. As cracks develop within the weakened material, blocks of soil displace laterally toward the open face. Cracking and lateral movement may gradually propagate away from the face as blocks continue to break free. Expansive Soils Expansive soils are soils that have a relatively high percentage of clay minerals and are subject to changes in volume with changing moisture conditions. Although the Project site is located within an area for which there is little or no specific data on expansive soils, 4,5 the expansion study completed as part of the Geotechnical Report determined that the Project site is underlain by soils with a medium to high expansion potential. ENVIRONMENTAL IMPACTS Thresholds of Significance City of Los Angeles CEQA Thresholds Guide Based on the City of Los Angeles CEQA Thresholds Guide, a project would have significant geological impacts if the risk from geological hazards exceeds that for the region. The determination of significance is based on the following thresholds: (E.1) Geological Hazards: A project would normally have a significant geologic hazard impact if it would cause or accelerate geologic hazards which result in substantial damage to structures or infrastructure, or expose people to substantial risk of injury. (E.2) Sedimentation and Erosion: A project would normally have a significant geologic hazard impact if it 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. 4 5 United States Department of Agriculture, Natural Resources Conservation Service. Web Soil Survey [web application]. Available: (Accessed: March 25, 2008). United States Geological Survey. Swelling Clays Map of the Conterminous U.S., Soil Map of California (1989) [web application]. Available: (Accessed: March 25, 2008). Page IV.E-8

9 (E.3) Landform Alterations: A project would normally have a significant impact on landform alteration if 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, hill slopes, canyons, ravines, rock outcrops, water bodies, streambeds and wetlands. (E.4) Mineral Resources: Whether, or the degree to which, the project might result in the permanent loss of, or loss of access to, a mineral resource that is located in a MRZ-2 6 or other known or potential mineral resource area; and whether the mineral resource is of regional or statewide significance, or is noted in the Conservation Element as being of local importance. Appendix G of the State CEQA Guidelines In accordance with guidance provided in Appendix G of the State CEQA Guidelines, the Project could have a potentially significant impact relating to geology and soils 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 issued by the State Geologist for the area 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) (c) Result in substantial soil erosion or the loss of topsoil. 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. 6 To implement the Surface Mining and Reclamation Act of 1975, the State Geologist developed the Mineral Resource Zone (MRZ) nomenclature and criteria based on the California Mineral Land Classification System. Under the MRZ classification, lands are classified into four main categories: MRZ-1, areas where geologic information indicates no significant mineral deposits are present; MRZ-2, areas that contain identified mineral resources; MRZ-3, areas of undetermined mineral resource significance; and MRZ-4, areas of unknown mineral resource potential. (California Department of Conservation, Division of Mines and Geology, California Surface Mining and Reclamation Policies and Procedures, Guidelines for Classification and Designation of Mineral Lands [web application]. Available: (Accessed August 8, 2008). Page IV.E-9

10 (d) (e) Be located on expansive soil, as identified in Table 18-1-B of the Uniform Building Code (1994), creating substantial risks to life or property. Have soils incapable of adequately supporting the use of septic tanks or alternative wastewater disposal systems where sewers are not available for the disposal. As presented in Section IV.A, Impacts Found To Be Less Than Significant, of this Draft EIR and the Initial Study, included as Appendix A of this Draft EIR, impacts associated with State CEQA Guidelines Thresholds (a) (ii) and (iv) and (e) above were found to be less than significant in the Initial Study and are therefore not included in the impact analysis below. Therefore, only Thresholds (a)(i) and (iii), (b), (c), and (d) for which the Initial Study disclosed potentially significant impacts will be addressed in the impact analysis below. Project Details Development of the Project would include the construction of an Eldercare Facility comprised of 149 Assisted Living Care dwelling units, four Alzheimer s/dementia Care guest rooms, and 22 Skilled Nursing Care guest rooms, with associated landscaping, over two levels of subterranean parking. The Project would range from four to five stories in height. For a detailed discussion of the Project description, refer to Section III, Project Description, of this Draft EIR. Project Impacts and Mitigation Measures Impact GEO-1 Fault Rupture Ground surface rupture results when the movement along a fault is sufficient to cause a gap or break along the upper edge of the fault zone on the surface. Damage due to surface rupturing is limited to the actual location of the fault line break, unlike damage from ground shaking, which can occur at great distances from the fault. As shown on Figure IV.E-1, the Project site is not located within an Alquist- Priolo Earthquake Fault Zone, and no active faults are known to underlie the Project site. 7 Therefore, surface rupture is not expected to affect the Project site. In addition, the City of Los Angeles Seismic Safety Element does not include the Project site within an Alquist-Priolo Special Study Zone or Fault Rupture Study Area. 8 Nonetheless, the Project would be constructed in compliance with all applicable provisions of the Los Angeles Building Code (LABC) and the State of California Uniform Building Code (UBC). Therefore, impacts from fault rupture would be less than significant and no mitigation measures are required. 7 8 City of Los Angeles Department of City Planning: Zone Information and Map Access System [web application]. Available: (Accessed: March 21, 2008). City of Los Angeles General Plan, Safety Element, Exhibit A: Alquist-Priolo Special Study Zones & Fault Rupture Study Areas in the City of Los Angeles, March 1994, website: March 25, Page IV.E-10

11 Impact GEO-2 Liquefaction and Soil Instability The Project site is within an area identified as having a potential for liquefaction; however, a Project site specific study completed as part of the Geotechnical Report determined that the Project site is not subject to liquefaction. Because the potential for liquefaction to occur at the site is considered non-existent, the potential for ground failures often associated with liquefaction (e.g., lateral spreading, settlement, etc.) is also considered unlikely. The Project would be constructed in compliance with all applicable provisions of the LABC and the UBC. Therefore, impacts from liquefaction would be less than significant and no mitigation measures are required. Impact GEO-3 Soil Erosion and Loss of Topsoil Construction Currently, the northern portion of the Project site is vacant and the southern portion is developed with a 36-unit apartment building. 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 in 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, of this Draft EIR). All grading activities 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 onsite 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. Additionally, construction activities must meet the National Pollution Discharge Elimination System (NPDES) requirements for storm water quality and comply with all applicable regulations with regard to surface water quality as governed by the State Water Resources Control Board (SWRCB). The SWRCB mandates that projects that disturb one or more acres of soil or less than one acre but are part of a larger development disturbing one or more acres must obtain coverage under the Statewide General Permit for Discharges of Storm Water Associated with Construction Activity. The General Permit requires that prior to construction activity project applicants file a Notice of Intent (NOI) with the SWRCB and prepare a project-specific Storm Water Pollution Prevention Plan (SWPPP) that incorporates Best Management Practices (BMPs) to control erosion and to protect the quality of surface water runoff during the construction period. Because the grading and excavation required for the proposed Project would involve a footprint of greater than one acre, the proposed Project would be required to file a NOI and prepare a SWPPP. With implementation of the applicable grading and building permit requirements and the application of BMPs outlined in the site-specific SWPPP, a less-than-significant impact would occur with respect to erosion or loss of topsoil and no mitigation measures are required. Page IV.E-11

12 Operation The northern portion of the Project site has been graded and does not contain substantial vegetative cover, paved areas or permanent structures. As such, the existing erosion potential is relatively high. The proposed Project would develop the entire Project site with pervious and impervious surfaces including structures, paved areas, and landscaping. Therefore, the proposed development would reduce the rate and amount of erosion occurring at the Project site and a less-than-significant impact would occur with respect to erosion or loss of topsoil and no mitigation measures are required. Impact GEO-4 Unstable Soils As discussed above, the soils underlying the Project site consist of artificial alluvial terrace deposits to depths of up to approximately 50 feet. The alluvium generally consists of grayish brown to dark gray silty clay and sandy clay that is moist and stiff. While local excavation and earthwork would be conducted to provide footings, foundations and subterranean walls to support the proposed parking structure and buildings, impacts associated with soil stability would be potentially significant. However, with implementation of Mitigation Measure GEO-4, impacts from soil instability would be reduced to a less-than-significant level. Mitigation Measure GEO-4 Unstable Soils The Project Applicant shall implement the following measures as recommended in the Geotechnical Report to further reduce potential impacts from unstable soils: a. Any trees or shrubs designated for removal shall be cut down and all stumps and roots shall be removed. All major vegetation and debris material shall be stripped and wasted from the site. b. All abandoned utility lines designated for removal shall be excavated and removed from the Project site. Unreinforced concrete irrigation lines may be crushed to a size acceptable to the Project Geotechnical Consultant and distributed in the future compacted fill. Abandoned cesspools and seepage pits encountered during grading shall be excavated under the observation of a representative of the Project Geotechnical Consultant and backfilled with pea-gravel, or where possible, with certified compacted fill. c. The existing artificial fill located in areas to be constructed upon with reinforced concrete slabson-grade, or in areas to receive certified compacted fill, shall be excavated to expose the dense natural alluvium deposits. The approximate horizontal and vertical extent of these excavations shall be verified by the Project Geotechnical Consultant in the field. d. The surface exposed by stripping and excavation activities shall be scarified to a minimum depth of eight inches, moisture conditioned to produce a moisture content of about two percent above Page IV.E-12

13 optimum moisture and compacted to a minimum 90 percent relative compaction, based on American Society for Testing and Materials (ASTM) Test D1557. e. A completion of stripping and scarification certified compacted fill may be placed to design grades using onsite inorganic soils or approved import. f. Soil proposed for use as structural fill shall be inorganic, free from deleterious materials, and contain no more that 15 percent by weight of rocks larger than four inches. g. If excavations within well-cemented bedrock units produce irreducible rock that exceeds a maximum dimension of 12 inches, it shall not be placed in certified compacted fill without specific approval of the material by the Project Geotechnical Consultant, the disposal location and the disposal method. All disposal areas for oversized materials shall be mapped by the Project Geotechnical Consultant and indicated on the final as-built geotechnical map. h. Materials excavated on the Project site shall be considered suitable for use as certified compacted fill provided they do not contain appreciable quantities of organic debris. i. Where in-place moisture content exceeds optimum values, the materials shall be spread and dried, or mixed with dryer material. Final determination shall be provided in the field by the Project Geotechnical Consultants at the time the excavation takes place. j. Excavated material containing excessive organic debris shall not be suitable for use in the certified compacted fill. Materials deemed unsuitable shall be wasted offsite or as designated by the Project Architect or Geotechnical Consultant. k. The approved material shall be placed in layers, each not exceeding eighth inches in thickness (before compaction), water conditions to about two percent above optimum moisture content and compacted to a minimum 90 percent relative compaction based on ASTM Test D1577. l. Fill compaction tests shall be performed during placement of the future fills to verify acceptable compaction and moisture content. At a minimum, one test shall be performed with each 12 to 24 inches (vertical depth) or 1,000 cubic yards of fill (whichever is less). The Project Geotechnical Consultant shall determine if more frequent testing is required. m. Graded slopes shall be constructed at a maximum gradient of 2:1 (Height:Velocity). Fill slopes shall be constructed by overfilling and cutting back to the compacted core. Cut slopes shall be observed and approved by the Project Geotechnical Consultant. n. The upper 12 inches of pavement subgrade shall be compacted to a minimum of relative compaction of 95 percent. Page IV.E-13

14 o. Unless concrete bedding is required around utility pipes, free-draining sand shall be used as bedding. Sand proposed for use in bedding shall be tested in the Project Geotechnical Consultant s laboratory to verify its suitability and to measure its compaction characteristics. Sand bedding shall be compacted by mechanical means to achieve at least 70 percent relative density based on ASTM Tests D4253 and D4254. p. Only approved, onsite, inorganic solid or imported materials may be used above the base as utility trench backfill. If imported material is proposed for this use, a sample shall be tested and approved by the Project Geotechnical Consultant before any is delivered to the site. q. Proper compaction of trench backfill would be necessary under and adjacent to certified compacted fill, building foundations, concrete slabs and vehicle pavements. In these areas, backfill shall be conditioned with water to produce a soil-water content of about two percent above optimum content and placed in horizontal layers not exceeding six inchers in thickness (before compaction). Each layer shall be compacted to at least 90 percent relative compaction based on ASTM Test D1557. The upper 12 inches of trench backfill under vehicle pavement shall be compacted to at least 95 percent relative compaction. Where any trench crosses the perimeter foundation line of any building, the trench shall be completely plugged and sealed with compacted clay soil for horizontal distance of two feet on either side of the foundation. r. All foundation shall be founded a minimum of 24 inches into the dense natural alluvium deposits. Foundation reinforcement shall be specified by the Project Structural Engineer. Foundations may be sized utilizing the design parameters identified by the Project Geotechnical Consultant as identified in the Geotechnical Report. Scheduling the construction sequence shall be done to minimize the time interval between foundation excavation and concrete placement to reduce evaporation of water from foundation and floor subgrades. Concrete shall be placed only on foundation excavations that have been kept moist and free from drying crack and that content no loose debris or soil. s. The installation of temporary shoring shall be observed and approved by the Project Geotechnical Consultants. All excavations shall be stabilized within 30 days of initial excavation. Water shall not be allowed to pond on top of the excavations, nor to flow towards it. No vehicular surcharge shall be allowed within five feet of the top of the cut. t. The earth retaining elements on the perimeter of the Project site shall be designed to resist potential surcharge loads of nearby structures and vehicles for both temporary and permanent scenarios as identified in the Geotechnical Report. Page IV.E-14

15 u. Reinforced concrete slabs-on-grade should be designed as a structural slab-on-grade and should be a minimum of 12 inches thick and be reinforced as specified by the Project Structural Engineer, but not less than six bars spaced at 16 inches on center in each direction. Concrete shall be cast over a minimum four inch thickness of sand, placed over the approved subgrade. To minimize floor dampness, a ten millimeter visqueen (i.e., polyethylene) moisture barrier should be placed near the center of the sand layer, a minimum of two inches below the concrete slab. Concrete slabs shall be allowed to cure adequately before placing vinyl or other moisture sensitive floor coverings. When planning for site improvements, the landscape theme shall maintain uniform moisture conditions around isolated structures and concrete slabs-on-grade. The soil shall be kept on the moist side, minimizing differential moisture contents. v. All final design plans and supporting documents shall be reviewed by the Project Geotechnical Consultant. Impact GEO-5 Expansive Soils The Project site is underlain by soils with a medium to high expansion potential. Without proper site preparation or design, expansion and contraction of the onsite soils could cause pavement, concrete slabson-grade, and other structures to crack, posing a hazard to people, property, and infrastructure. Compliance with Mitigation Measure GEO-4 (e.g., reinforcing concrete slabs-on-grade to increase their resistance to differential movement as specified by the Project Structural Engineer and developing a landscape theme to maintain uniform moisture conditions around isolated structures and concrete slabson-grade) and applicable provisions of the LABC and the UBC, which include building foundation requirements appropriate to site conditions, would ensure impacts from expansive soils would be less than significant and no additional mitigation measures are required. CUMULATIVE IMPACTS Impact GEO-6 Cumulative Impacts Development of the proposed Project in conjunction with the related projects listed in Table II-1 (refer to Section II, Environmental Setting, of this Draft EIR) would result in further infilling of various land uses in the City of Los Angeles. Geotechnical hazards are site-specific and there is little, if any, cumulative relationship between development of the Project and the related projects. As such, construction of the related projects is not anticipated to combine with the Project to cumulatively expose people, property, or infrastructure to such geologic hazards as earthquakes, ground shaking, liquefaction, landslides, unstable soils, expansion soils, and/or result in substantial soil erosion or the loss of topsoil. Therefore, no cumulative geology and soils impacts are anticipated from the proposed Project combined with the related projects and no mitigation measures are required. Page IV.E-15

16 LEVEL OF SIGNIFICANCE AFTER MITIGATION Project impacts related to geology and soils would be less than significant with implementation of Mitigation Measure GEO-4. Page IV.E-16