4.5 GEOLOGY AND SOILS

Transcription

1 4.5 GEOLOGY AND SOILS This section of the EIR describes the existing geology, soils, and seismic conditions on campus and analyzes the potential physical environmental effects related to seismic hazards, underlying soil characteristics, slope stability, erosion, and excavation and export of soils. Potential effects of soil conditions on air and water quality as a result of construction-related activities are discussed in Section 4.2, Air Quality, and Section 4.7, Hydrology and Water Quality, respectively. Portions of this section are based on a geotechnical analysis for the 2004 LRDP which was prepared by Ninyo and Moore in a report entitled Geological Technical Study University of California, San Diego 2004 Long Range Development Plan Environmental Impact Report (included in Appendix D) ENVIRONMENTAL SETTING REGIONAL GEOLOGY UCSD is located in the western portion of the Peninsular Ranges geomorphic province of southern California. This geomorphic province encompasses an area that extends for approximately 790 miles, from the Transverse Ranges and the Los Angeles Basin to the tip of Baja California, and varies in width from 30 to 100 miles. The majority of this geomorphic province is characterized by northwest trending mountain ranges separated by subparallel fault zones. In general, the Peninsular Ranges are underlain by Jurassic-age metavolcanic and metasedimentary rocks and by Cretaceous-age igneous rocks of the southern California batholith. The westernmost portion of the province in San Diego County generally consists of Tertiary- and Quaternary-age sedimentary rocks. The Peninsular Ranges are traversed by several major active faults. The Whittier-Elsinore, San Jacinto, and San Andreas faults are major active fault systems located northeast of San Diego. The Agua Blanco-Coronado Bank and San Clemente faults are active faults located to the west-southwest. The Rose Canyon fault zone is also a major active fault system located in the San Diego area with portions that have been included in the State of California Earthquake Fault Zones. Right-lateral strike-slip movement is the major tectonic activity associated with these and other faults within this regional tectonic framework, which also have the potential for generating strong ground motions (earthquakes) at the UCSD campus SOILS AND GEOLOGIC FORMATIONS Soils and geologic formations that occur on the UCSD campus are illustrated on Figure and are described below: Artificial Fill (Qaf). Numerous areas of man-made artificial fill are present on the campus. Some of these fills date back to the days of the long abandoned Camp Matthews. Other fills are associated with the improvements for UCSD. It is expected that the fill soils were derived mostly or entirely from local sources. Fill depths range from no more than a few feet to 60 feet or more in depth where canyons or substantial depressions have been filled. Documentation of the placement and compaction of the older military fills is limited; however, for some of the newer fills documentation of geotechnical observation and testing may be available. Quaternary Alluvium (Qal). Quaternary alluvium (soils that have been transported by flowing water) is present in the water courses on the site. Alluvial soils are typically in a loose, unconsolidated condition. The largest areas of alluvium occur on the east campus where they are estimated to range up to 20 feet in thickness. The deposits are expected to be thinner elsewhere on the campus. September 2004 UCSD 2004 Long Range Development Plan Final EIR 4.5-1

2 Colluvium. On most of the lower slopes of steep canyons, slow downhill soil creep has produced accumulations of colluvial soils. The colluvium is composed of three- to six-feet thick unconsolidated clayey soils. Colluvium is compressible and usually expansive. Due to its relatively thin and sporadic distribution, colluvium is not a mapped unit in Figure Topsoil. In undisturbed areas there is a relatively thin mantle of topsoils that cover much of the underlying formational units. The on-site topsoils consist predominantly of portions of three soil series: the Carlsbad, Chesterson, and Gaviota series. The Carlsbad and Chesterson soils are the most common on the site, with widespread exposure in undeveloped portions of east and west campus and SIO. Gaviota soils are generally limited to smaller exposures in the southern part of SIO. Carlsbad soils are composed of gravelly loamy sands, whereas Chesterson and Gaviota soils consist chiefly of fine sandy loams. Native soils have been replaced with construction fill throughout the developed portions of the campus. The on-site topsoils exhibit varying engineering and agricultural characteristics. Prime Farmland topsoils are absent from the site. Portions of the Chesterson soils contain clayey subsoils, which may be subject to expansion effects due to the water holding capacity of clay materials. Surficial expression of expansive potential may include cracks from desiccation and popcorn texture (expansive nodules or agglomerations upon wetting). Due to its relatively thin and sporadic distribution, topsoil is not a mapped unit in Figure Quaternary Beach Deposits (Qb). Quaternary beach deposits are located along the shoreline at the westernmost boundary of the campus. Beach deposits typically consist of very loose, fine- to coarsegrained sands of variable thickness. Quaternary Landslide Deposits (Qls). Numerous Quaternary landslides are present in the steep canyon slopes of the campus. The landslides consist of mostly arcuate back and side scarps and hummocky slide mass topography. Pleistocene Bay Point Formation (Qbp). Exposures of the Bay Point Formation are limited to the southwestern portion of SIO. This formation is composed of mostly marine and nonmarine, poorly consolidated, fine- to medium-grained, pale brown, fossiliferous sandstone. The fossils found occur between 0 and 100 feet above mean high tide and include mollusks, Foraminifera, and ostracods. These fossils indicate an ancient brackish water estuarine environment and a late Pleistocene age. Pleistocene Lindavista Formation (Qln). The early Pleistocene-age Lindavista Formation is predominately composed of reddish-brown interbedded sandstone and conglomerate. Ferruginous cement, mainly hematite, gives the Lindavista Formation its characteristic color and a resistant nature. The formation is relatively flat lying and exhibits massive to indistinct stratification. However, some conglomerate channel deposits can be traced laterally over several thousand feet. The unit is very resistant to weathering and forms the relatively flat tops of the mesas in the campus above about elevation 340 to 350 feet. Eocene Scripps Formation (Tu). Underlying the Lindavista Formation is the Eocene-age Scripps Formation. The Scripps Formation consists primarily of yellowish brown, silty fine- to medium-grained sandstone with interbeds of siltstone and claystone and occasional cobble-conglomerate. The Scripps Formation is widely exposed across the campus and underlies many of the steep canyon slopes. Eocene Ardath Shale (Tu). Underlying the Scripps Formation and in partial intergradation is the Eocene-age Ardath Shale. The Ardath Shale consists predominately of weakly fissile, olive-gray shale. Concretionary beds containing molluscan fossils are common. On the campus, both the Scripps and Ardath formations contain clay beds and clay seams. Landsliding has occurred and continues to occur in both units. UCSD 2004 Long Range Development Plan Final EIR September

3 EAST AND WEST CAMPUS Pacific Ocean La Jolla Shores Drive Genesee Avenue 5 Expedition Way North Campus Hopkins Drive Scripps Pier Downwind Way Eleanor Roosevelt La Jolla Shores Drive SCRIPPS INSTITUTION OF OCEANOGRAPHY Feet North Torrey Pines Road Thurgood Marshall University Center Warren Campus Services Complex Voigt Drive Pacific Ocean La Jolla Farms Road Muir UCSD Medical Center La Jolla Science Research Park Regents Road Gilman Drive School of Medicine Campus Building Parking/Recreation Facility Soil Classification Qaf - Artificial Fill Qal - Quaternary Alluvium La Jolla Shores Drive Revelle Mesa Housing Qbp - Quaternary Bay Point Formation Qln - Quaternary Lindavista Formation Qls - Quaternary Landslide Deposits Undifferentiated Tertiary Sedimentary Deposits (Including Scripps Formation and Ardath Shale) Approximate Limits of Landslide Theatre District Gilman Drive Villa La Jolla Drive La Jolla Village Drive Fault Trace (Approximate or Inferred) Fault Trace (Concealed) ,000 Feet Source: Ninyo & Moore, 2003 GEOLOGIC FORMATIONS AND FAULTS ON THE UCSD CAMPUS FIGURE /12/03 JV MV Z:\\Projects\IS\UCSD\mxd\GeologicFormations.mxd

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5 FAULTING AND SEISMICITY Ground shaking as a result of earthquakes is a potential hazard throughout southern California. The intensity of ground shaking at any particular site and relative potential for damage from this hazard depends on the earthquake magnitude, distance from the source (epicenter), and the site response characteristics (ground acceleration, predominant period, and duration of shaking). Faulting in the region generally consists of a number of northwest trending, predominately right-lateral strikeslip faults at the boundary between the Pacific and North American tectonic plates. In the general area of UCSD, these include the Rose Canyon fault, the Elsinore fault zone, and the off-shore zone of deformation. There are no Alquist-Priolo (A-P) Study Zones (active faults) located on the campus. The A-P Study Zones Act of 1972 defines active faults as those with evidence of displacement during the Holocene epoch (roughly the past 11,000 years) and requires that structures intended for human occupancy not be constructed over an active fault. Several faults have been mapped at various locations on the campus, which are located in Figure and described below. None of these faults are considered active or significant sources of seismic activity; however, the UCSD campus is in a seismically active area as is much of southern California. Ground surface rupture is not likely to occur as a result of an earthquake or seismic event because none of the faults on the campus are considered active; however, as discussed below, one fault is considered potentially active. In general, the unnamed faults on campus have not been studied in detail and little is known about their style of faulting; however, it is likely that many of them are high-angle normal faults. The Powers fault (not formally named) trends in a southwesterly direction from the I-5 and Genesee Avenue interchange to Seaweed Canyon, where it is lost in the disturbed bedding of the Seaweed landslide and associated slide masses. The Redwood fault is an up/down (normal) fault passing beneath Ritter Hall and the deep sea drilling facility and continues east-northeasterly to end at the Azul fault (Elliott 1988). The Azul fault is a horizontal slip fault passing in a roughly north-northwest direction under the eastern side of SIO (Elliott 1988). The Salk Fault, which is a high-angle normal fault, crosses the northerly most part of the campus in an east-northeasterly direction. The Torrey Pines fault is another high-angle fault which crosses the campus in a northeasterly direction just south of the Salk Fault. Based upon current understanding, all of the faults shown on the campus are considered inactive except for the Powers fault, which is considered potentially active. A potentially active fault is one that has demonstrated movement during the last 1.6 million years but not during the last 11,000 years. Although no active faults are located on campus, a significant seismic event could affect the campus. The UCSD campus is located in Seismic Zone 4, defined by the California Building Code (CBC), the highest risk seismic zone. Based on the Uniform Building Code (UBC), the CBC defines and ranks different regions according to their seismic hazard potential. There are four types of these regions, Seismic Zones 1 through 4, with Zone 1 having the least seismic potential and Zone 4 having the highest seismic potential. The UCSD campus is also within a Near-Source Zone for active faults. A Near-Source Zone is an area subject to the largest and most damaging ground acceleration and velocity with severe structural damage because of its proximity to an active fault that is capable of producing a major earthquake. The Rose Canyon Fault is an active fault capable of producing a major earthquake and is located approximately one mile south and southwest of SIO. The Rose Canyon Fault is classified as seismic source type B based upon the criteria of the CBC. Seismic source type is determined upon maximum moment magnitude (M) and slip rate (R). A B-type seismic source is an active fault capable of generating a maximum earthquake magnitude (moment magnitude) greater than or equal to 7.0 and having a slip rate of less than 5 millimeters (mm) per year, or having a maximum earthquake magnitude of less than 7.0 but having a slip rate greater than 2 mm per year. Specifically, the Near-Source Zone for B-type faults is an area that lies within 10 kilometers (6.2 miles) of the fault. UCSD is approximately one mile from the Rose Canyon Fault at its closest point. According to data from the California Geologic Survey (formerly the California Division of Mines and Geology), the Rose September 2004 UCSD 2004 Long Range Development Plan Final EIR 4.5-5

6 Canyon fault is capable of generating a magnitude 6.9 earthquake which would cause strong ground motions at the campus. Based upon Probabilistic Seismic Hazards Maps produced by the California Geological Survey, there is a 10 percent probability that ground acceleration at the campus will exceed 0.3 g (30 percent the acceleration of gravity) in the next 50 years LANDSLIDES Areas having the potential for earthquake-induced landslides generally occur within areas of previous landslide movement, or where local topographic, geological, geotechnical, and subsurface water conditions indicate a potential for permanent ground displacements. Historic landslides have been identified at several locations on the campus based upon a review of published geologic and topographic maps and stereoscopic aerial photographs. Figure includes the limits of landslide areas known on campus. The potential for earthquake-induced landslides in hillside terrain on the campus is also present. Generally, these types of failures consists of rock falls, disrupted soil slides, rock slides, soil lateral spreads, soil slumps, soil block slides, and soil avalanches. Failures of man-made slopes could also occur in some areas of the previously developed portions of UCSD if the slopes were created prior to contemporary standards or if conditions have changed around the slopes that alter the loads that they bear. Known/confirmed landslides on campus are in the vicinity of the Southwest Fisheries Building, the Birch Aquarium at Scripps, the Oceanic and Atmospheric Research Facility, the main canyon on the west campus north of Warren, and the east campus Mesa Housing. The landslide at the Southwest Fisheries Building is a deep-seated landslide that is currently buttressed to some degree by a large pile of rubble at the toe of the slide which is reducing the effects of wave action on the slide mass. A deep-seated landslide is one that tends to fall incrementally with the movement triggered by cumulative rainfall over long periods of time or high ground accelerations experienced during large earthquakes. The landslide at the Birch Aquarium at Scripps is also deep-seated. A geotechnical investigation conducted by Kleinfelder in 1988, prior to construction of the aquarium, concluded that the landslide was adequately stable in its then current configuration. A known deep-seated landslide is at the east end of the Oceanic and Atmosphere Research Facility off of La Jolla Shores Drive at SIO and extends east to underlie La Jolla Shores Drive. Reportedly, this landslide was stabilized during construction of the facility (Geocon 1998). The landslides in the vicinity of the east campus Mesa Housing are relatively shallow and do not currently underlie any structures GROUNDWATER Groundwater is expected to occur at relatively shallow depths along the bottoms of canyons and drainages. The direction of groundwater flow is generally toward the ocean (or west-southwest), with significant local variations. Groundwater depths vary throughout the campus depending upon topography and range, from just beneath the ground surface in low-lying areas near the ocean to hundreds of feet in hilly areas. However, the majority of the campus is not expected to be affected by shallow groundwater. Groundwater levels may be expected to fluctuate due to tidal influences, seasonal rainfall variations, irrigation, and other factors. Perched groundwater (sometimes resulting in temporary springs ) may exist in the canyon areas on campus; however, it is unlikely that substantial groundwater would be encountered in any areas on campus, with the exception of the canyon bottoms TOPOGRAPHY The UCSD west and east campuses are part of the Torrey Pines Mesa and therefore consist of relatively flat elevated lands incised with deep canyons. East of North Torrey Pines Road is a north-south trending ridge over 400 feet above mean sea level (AMSL). Two canyons south of Genesee Avenue just west of Interstate 5 drop below 200 feet AMSL. The remainder of the west and east campuses ranges in elevation between 300 and 400 feet AMSL. At SIO, on-site elevations range from over 400 feet AMSL in the northeastern corner to UCSD 2004 Long Range Development Plan Final EIR September

7 almost sea level along the western border. SIO can be characterized as a westerly sloping mesa that ends as a bluff along the ocean. It is also traversed with several drainages. The University House and associated beach property are located on the northern side of a deep drainage known as Black Canyon. Except for some graded slopes along I-5, Gilman Drive, and La Jolla Village Drive, slopes greater than 15 percent are associated with the drainages that traverse the study area. Two major drainages with smaller finger canyons branch off from each other in the northeastern corner of the west campus. Side slopes of these two drainages are generally greater than 25 percent. Drainages and associated steep slopes also occur on the east campus and SIO REGULATORY FRAMEWORK Regulations pertaining to water quality impacts that may result from erosion are included in Section 4.7 of this EIR FEDERAL Uniform Building Code The Uniform Building Code (UBC) is a model building code that provides the basis for the California Building Code (CBC). The UBC defines different regions of the United States and ranks them according to their seismic hazard potential. There are four types of these regions, which include Seismic Zones 1 through 4, with Zone 1 having the least seismic potential and Zone 4 having the highest seismic potential. UCSD is located in Seismic Zone STATE California Building Code California law provides a minimum standard for building design through the CBC. The CBC is based on the UBC, with amendments for California conditions. The University of California by administrative policy follows the CBC. Chapter 23 of the CBC contains specific requirements for seismic safety. Chapter 29 of the CBC regulates excavation, foundations, and retaining walls. Chapter 33 of the CBC contains specific requirements pertaining to site demolition, excavation, and construction to protect people and property from hazards associated with excavation cave-ins and falling debris or construction materials. Chapter 70 of the CBC regulates grading activities, including drainage and erosion control. Construction activities are subject to occupational safety standards for excavation, shoring, and trenching as specified in Cal-OSHA regulations (Title 8 of the California Code of Regulations [CCR]) and in Section A33 of the CBC. Seismic Hazards Mapping Act The California Geologic Survey, formerly the California Department of Conservation, Division of Mines and Geology (CDMG), provides guidance with regard to seismic hazards. Under CDMG s Seismic Hazards Mapping Act (1990), seismic hazard zones are to be identified and mapped to assist local governments in land use planning. The intent of this publication is to protect the public from the effects of strong ground shaking, liquefaction, landslides, ground failure, or other hazards caused by earthquakes. In addition, CDMG s Special Publications 117, Guidelines for Evaluating and Mitigating Seismic Hazards in California, provides guidance for the evaluation and mitigation of earthquake-related hazards for projects within designated zones of required investigations. September 2004 UCSD 2004 Long Range Development Plan Final EIR 4.5-7

8 UC Policies on Seismic Safety The UC Seismic Safety Policy last updated January 17, 1995 is to acquire, build, maintain, and rehabilitate buildings and other facilities that provide an acceptable level of earthquake safety. The level of safety is also defined in the UC policy. The UC Seismic Safety Policy articulates five primary points: Program for Abatement of Seismic Hazards. Develop a program for the identification and temporary and permanent abatement of seismic hazards to existing buildings and other facilities. Consulting Structural Engineer. Engage structural engineers to examine existing buildings and other facilities. Structural engineers are to submit reports on the adequacy of University facilities to resist seismic forces, based on Chapter 23 of the CBC and the engineer s professional evaluations with respect to Appendix A of the UC Seismic Safety Policy. Standards for Seismic Rehabilitation Projects. Correctional programs for structures that do not provide adequate safety shall provide, at a minimum, an acceptable level of earthquake safety equivalent to the current seismic provisions of Chapter 23 of the CBC, or local seismic requirements, whichever is more stringent, with respect to life safety and prevention of personal injury. Preliminary plans for all seismic rehabilitation shall be reviewed by the consulting structural engineer, and recommendations of the structural engineer shall be incorporated into the project plans by the design engineer. Repair of Buildings and Other Facilities Damaged by Earthquakes. This section sets standards for University buildings and facilities that are damaged by earthquakes, based on the reduction in lateral load capacity of the structure in question. New Buildings and Other Facilities. The design of new buildings shall, at a minimum, comply with the current provisions of Chapter 23 of the CBC, or local seismic requirements, whichever is more stringent. Provisions shall also be made for adequate anchoring of nonstructural building elements. No new University structures may be constructed on the trace of a known active fault. All plans shall be reviewed by a consulting structural engineer who must, prior to release of construction funds, certify that the structure complies with the UC Seismic Safety Policy. The UC has also adopted an Independent Seismic Review of Structures Policy, effective October 1, 1986, to ensure that seismic safety and other structural considerations are fully incorporated into capital project design, purchase, and lease decisions. The policy states that independent review shall be conducted by a qualified licensed structural engineer of the structural seismic design of all capital projects, whether new construction or remodeling, which involve structural design and are intended for human occupancy, or which affect human safety. The review shall be initiated early in the project's life, and preferably during the preparation of schematic designs, so that it can be performed in conjunction with the independent design and cost review and value engineering processes, where applicable, and shall be continued at appropriate times during the design process. In all cases, working drawings and calculations shall be reviewed for conformance of the new work to the most current applicable seismic design code requirements prior to inviting bids for such work or authorizing structural change orders. California Coastal Act of 1976 The CCA, discussed in greater detail in Section 4.8, includes policies for development proposed within the coastal zone and is administered by the California Coastal Commission (CCC). Policies relevant to the issues discussed in this section of the EIR primarily include those that address minimizing impacts (such as soil erosion) that could adversely affect biological resources. Section of the CCA states that: The biological productivity and the quality of coastal waters, streams, wetlands, estuaries, and lakes appropriate to maintain optimum populations of marine organisms and for the protection of human health shall be UCSD 2004 Long Range Development Plan Final EIR September

9 maintained and, where feasible, restored through, among other means, minimizing adverse effects of waste water discharges and entrainment, controlling runoff, preventing depletion of ground water supplies and substantial interference with surface water flow, encouraging waste water reclamation, maintaining natural vegetation buffer areas that protect riparian habitats, and minimizing alteration of natural streams. The 1989 LRDP EIR addressed the CCA policies regarding landform alteration in the Geology and Soils section of the EIR. In this EIR, landform alteration issues are addressed in the Section 4.1, Aesthetics, because of their relevance to visual quality PROJECT IMPACTS AND MITIGATION The following sections address various potential impacts relating to geology and soils that could result due to the implementation of the proposed 2004 LRDP. Potential impacts to development on the UCSD campus are generally summarized in the geologic constraints map provided as Figure Figures and do not include La Jolla del Sol. This area was not mapped because substantial new development of this site is not anticipated. However, the geologic and seismic conditions of this site and the associated hazards are anticipated to be similar to those discussed for the rest of the campus, and potential impacts to development on this parcel are included in the impact analyses in the following sections ISSUE 1 EXPOSURE TO SEISMIC-RELATED HAZARDS Geology and Soils Issue 1 Summary Would implementation of the 2004 LRDP expose people or structures to potential substantial adverse effects of a rupture of a known earthquake fault, strong seismic groundshaking, seismic related ground failure, liquefaction or landslides? Impact: The UCSD campus contains seismic hazards but compliance with the California Building Code and UC Seismic Safety Policy would reduce seismic related hazards to people and structures. Significance Before Mitigation: Less than significant. Mitigation: No mitigation is required. Significance After Mitigation: Less than significant. Standards of Significance Based on Appendix G of the CEQA Guidelines, implementation of the 2004 LRDP may have a significant adverse impact if it would expose people or structures to potential substantial adverse effects, including the risk of loss, injury, or death involving: 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; Strong seismic groundshaking; Seismic related ground failure, including liquefaction; or Landslides. Significant adverse geologic impacts not directly related to seismic activity including topsoil loss, soil stability, landslides, lateral spreading, subsidence, liquefaction, collapse, and expansive soils are discussed in Issues 2 through 4. September 2004 UCSD 2004 Long Range Development Plan Final EIR 4.5-9

10 Impact Analysis Fault Rupture. None of the faults on the campus are considered active; therefore, ground surface rupture is not likely to occur as a result of an earthquake or seismic event. In addition, the campus routinely reviews all building plans for compliance with the California Building Code (CBC) and the campus also follows the UC Policy on Seismic Safety that requires compliance with the CBC as well as independent review of structural seismic design of both new construction and remodeling projects. If development is planned within 100 feet of a fault trace (the line formed by the intersection of a fault and the earth s surface), it is likely that a fault study would be recommended. Figure illustrates fault traces located on the UCSD campus. The purpose of a fault study would be to determine the location and orientation of the respective fault, to evaluate the potential geologic anomalies adjacent to the fault trace, and to evaluate the fault plane as a potential slope stability factor. The fault study would be used by structural engineers to determine the most appropriate design and building techniques, such as additional structural support, required to comply with the CBC and UC Policy on Seismic Safety. Because no active faults are located on campus and UC complies with the CBC as well as the UC Seismic Policy, implementation of the 2004 LRDP is considered to result in a less than significant impact associated with the rupture of a known earthquake fault. Ground Shaking. As previously discussed, the campus is located in a seismically active area that could experience strong ground shaking. Ground shaking has the potential to dislodge objects from walls, ceilings, and shelves, and to damage and destroy buildings and other structures. People in the area would be exposed to these hazards. UCSD minimizes hazards associated with damage or destruction to buildings and other structures through a number of ways, including: Reviewing and approving all draft building plans for compliance with the CBC, which includes specific structural seismic safety provisions; Implementation of the UC program to upgrade or replace existing buildings not adequately prepared to withstand seismic hazards, which diminishes the existing hazards; Compliance with the UC Seismic Safety Policy, which requires anchorage for seismic resistance of nonstructural building elements such as furnishings, fixtures, material storage facilities, and utilities that could create a hazard if dislodged during an earthquake; and Incorporation of seismic related emergency procedures into departmental emergency response plans. These programs and procedures reduce the hazards from seismic shaking by preparing faculty, staff, and students for emergencies. All of these programs and procedures would continue to be implemented as new facilities are developed on campus under the 2004 LRDP. Therefore, impacts associated with ground shaking are considered to be less than significant. Ground Failure and Liquefaction. Ground failure such as fault rupture and landslides is discussed within other portions of this issue. Liquefaction is the other seismic related ground failure hazard that was identified as relevant for the UCSD campus. Soil liquefaction occurs within relatively loose, cohesionless sands located below the water table (60 to 200 ft below ground) that are subjected to ground accelerations from earthquakes. Due to the dense nature of the underlying formational materials (Lindavista Formation) and lack of near surface groundwater over the majority of the campus, the potential for liquefaction occurring on campus is considered very low. Furthermore, geotechnical investigations that address the potential for liquefaction, lateral spreading, and other types of ground failure are routinely performed for applicable projects, and compliance with CBC would reduce hazards associated with liquefaction if there were a potential for it to occur at a given site. Therefore, impacts associated with liquefaction are considered to be less than significant. UCSD 2004 Long Range Development Plan Final EIR September

11 EAST AND WEST CAMPUS Torrey Pines Center North Torrey Pines Center South Genesee Avenue 5 Pacific Ocean La Jolla Shores Drive Coast Apartments Expedition Way Visitor Information Center North Campus Recreation Area North Campus Hopkins Drive Scripps Pier Director's Office SIO Library La Jolla ShoresDrive Downwind Way Birch Aquarium at Scripps SCRIPPS INSTITUTION OF OCEANOGRAPHY Feet North Torrey Pines Road Pangea Parking Structure Extended Studies & Public Programs Eleanor Roosevelt Institute of the Americas IR/PS Marshall Field Thurgood Marshall RIMAC Arena San Diego Supercomputer Center Faculty Club Book Drop Fitness Par Course Geisel Library University Center Price Center & Bookstore Chancellor's Complex Matthews Quad Warren Campus Services Complex Canyonview Aquatics & Activities Center Voigt Drive Recreation Fields Shiley Eye Center Preuss School Pacific Ocean La Jolla Farms Road Muir Muir Field Mandeville Center Student Center Student Center B Parking Office Gilman Parking Structure Thornton Hospital Perlman UCSD Medical Center La Jolla Science Research Park Regents Road Faults: Potentially Active, Inactive, Presumed Inactive, or Activity Unknown Campus Building Parking/Recreation Facility Geologic Constraints La Jolla Shores Drive Revelle Commons Revelle Mandell Weiss Forum School of Medicine Visitor Information Center Guava VA Medical Center Gilman Drive Mesa Housing Generally Stable Areas Potentially Compressible Alluvial Soils with Potential for Liquefaction Coastal Bluff Areas with Potential Slope Instability Steeply Sloping/Canyon Areas with Potential Slope Instability Coast Apartments Mandell Weiss Theatre Theatre District Gilman Drive Villa La Jolla Drive La Jolla Village Drive Landslides: Confirmed, Known, or Suspected ,000 Feet Source: Ninyo & Moore, 2003 GEOLOGIC CONSTRAINTS ON THE UCSD CAMPUS FIGURE /12/03 JV MV Z:\\Projects\IS\UCSD\mxd\GeologicConstraintsMap.mxd

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13 Landslides. As previously identified, areas having potential for landslides occur throughout the campus, but are mainly restricted to steep slopes and hillsides. Development on, within, or down slope from landslides, landslide deposits, or manufactured slopes could result in structural damage to the development, foundational failure, undermining of the supporting structural soils, or damage from land sliding debris. However, all conditions present on the UCSD campus are believed to be mitigable with standard planning and design techniques (Ninyo & Moore 2003). If necessary, an unstable slope or landslide can be stabilized with shear pins, which are shafts that have been excavated through the slide mass into stable materials and are then filled with reinforced concrete. Buttressing (by creating a large earthen mass in front of the landslide to halt its movement) or removal of the landslide deposits prior to construction of any structures is another stabilization method. Because most of the areas on the campus that are prone to landslides are located on, above, or below steep slopes and hillsides, limited development that could be impacted by landslides is expected to occur as a part of the 2004 LRDP. Areas anticipated for development that could be impacted include the SIO and Mesa Housing area. Geotechnical investigations that address the potential for landslides are routinely performed for applicable projects (those on or adjacent to known landslides or slopes) and compliance with CBC as well as the UC Policy on Seismic Safety would reduce hazards. Therefore, impacts associated with landslides are considered to be less than significant. Mitigation Measures The 2004 LRDP would have a less than significant impact with regard to seismic related hazards such as fault rupture, strong seismic ground shaking, seismic related ground failure, liquefaction, and landslides; therefore, no mitigation measures are required ISSUE 2 SOIL EROSION OR TOPSOIL LOSS Geology and Soils Issue 2 Summary Would implementation of the 2004 LRDP result in substantial soil erosion or the loss of top soil? Impact: Implementation of the 2004 LRDP could result in minimal amounts of increased erosion associated with construction activities. Significance Before Mitigation: Less than significant. Mitigation: No mitigation is required. Significance After Mitigation: Less than significant. Standards of Significance Based on Appendix G of the CEQA Guidelines, implementation of the 2004 LRDP may have a significant adverse impact if it would result in substantial soil erosion or the loss of topsoil. Impact Analysis As stated in Section , there is a relatively thin mantle of topsoil that covers much of the underlying formational units in undisturbed areas of the campus. Native soils have been replaced with construction fill throughout the developed portions of the campus. Erosion can occur as a result of, and can be accelerated by, site preparation activities associated with development. Vegetation removal in landscaped (pervious) areas could reduce soil cohesion, as well as the buffer provided by vegetation from wind, water, and surface disturbance, which could render the exposed soils more susceptible to erosive forces. Additionally, excavation or grading for any proposed building or parking structures may also result in erosion during construction activities, irrespective of whether hardscape previously existed at the construction site, as bare soils would be exposed and could be eroded by wind or water. September 2004 UCSD 2004 Long Range Development Plan Final EIR

14 Earth-disturbing activities associated with construction would be temporary and erosion effects would depend largely on the areas disturbed, the quantity of disturbance, and the length of time soils are subject to conditions that would be affected by erosion processes. All construction activities would comply with Chapter 29 of the CBC, which regulates excavation activities and the construction of foundations and retaining walls, and Chapter 70 of the CBC, which regulates grading activities, including drainage and erosion control. As stated in Section 4.2, Air Quality, UCSD would continue to implement dust control measures consistent with APCD regulations. Additionally, as stated in Section 4.7, Hydrology and Water Quality, UCSD would continue to comply with the National Pollutant Discharge Elimination System (NPDES) general permit for construction activities, pursuant to which, as part of an erosion control plan, construction site erosion and sedimentation control BMPs would be implemented and would include such measures as silt fences, watering for dust control, straw bale check dams, hydroseeding, and other measures. Further, UCSD would continue to implement the campus wide runoff management program required to comply with the applicable provisions of NPDES Phase II, which includes implementation of best management practices (BMPs) to control erosion and sedimentation. With the continued implementation these measures, substantial erosion or topsoil loss is unlikely to occur during 2004 LRDP related construction, and the associated impact would be less than significant. Erosion can also occur in connection with the hydrology of a project. Increases in flow, typically associated with increased impermeable surface, can result in increased erosion in on- and off-site drainage courses. As stated in Section 4.7, Hydrology and Water Quality, UCSD would implement mitigation measures as appropriate and, consequently, the velocity of flows would not substantially increase. Therefore, substantial erosion is unlikely to occur on an operational basis, and this impact would be less than significant. Mitigation Measures The 2004 LRDP would have a less than significant impact on the loss of topsoil and soil erosion; therefore, no mitigation measures are required ISSUE 3 SOIL STABILITY Geology and Soils Issue 3 Summary Would implementation of the 2004 LRDP be located on a geologic unit or soil that is unstable or that would become unstable and potentially result in a landslide, lateral spreading, subsidence, liquefaction, or collapse? Impact: Loose or compressible soils may be found on campus; however, implementation of the 2004 LRDP is unlikely to expose people or structures to hazards associated with soil stability issues. Significance Before Mitigation: Less than significant. Mitigation: No mitigation is required. Significance After Mitigation: Less than significant. Standards of Significance Based on Appendix G of the CEQA Guidelines, implementation of the 2004 LRDP may have a significant adverse impact if it would 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. A significant impact would occur in cases where people or structures could be exposed to potential substantial adverse effects due to soil stability including the risk of loss, injury, or death. UCSD 2004 Long Range Development Plan Final EIR September

15 Impact Analysis Areas of the campus that are susceptible to landslides, collapse, liquefaction, and other seismic-related hazards are discussed in Issue 1. Compressible soils, slope instability, and coastal bluffs are the other soil stability issues that are discussed in this section. Compressible Soils. Loose or compressible soils may be found on campus, especially in undeveloped areas with deposits of alluvium or slope wash/colluvium and developed areas with undocumented and/or uncompacted fill. These materials may be subject to settlement under increased loads, or due to an increase in moisture content from site irrigation or changes in drainage conditions. Typical measures to treat compressible soils involve removal and replacement with properly compacted fill, compaction grouting, or deep dynamic compaction. Geotechnical investigations that are required in order to comply with the CBC address compressible soils and compliance with CBC would reduce hazards. Therefore, impacts associated with compressible soils are considered to be less than significant. Slope Instability. Potential hazards associated with slope instability may include surficial failures, earthflows, debris flows, mudslides, rockfalls, soil creep, or erosion. Based on the steep nature of many slopes and the generally poorly consolidated nature of the sedimentary materials, including colluvial soils, such hazards may adversely effect development on the campus. Slopes steeper than 25 degrees (approximately 2:1 [horizontal to vertical]) are more susceptible to instability. Areas with slopes this steep generally exist in the northern and western portions of the campus, and in many of the drainages and canyons. Similar to landslides, steep slopes can typically be stabilized and all conditions present at UCSD are believed to be mitigable with standard planning and design techniques (Ninyo & Moore 2003). Geotechnical investigations that are required in order to comply with the CBC address slope stability and compliance with CBC would reduce hazards; therefore, impacts associated with slope instability are considered to be less than significant. Coastal Bluffs. Coastal bluffs occur along the western margins of SIO. They also occur to the west of the Gliderport, just beyond UCSD land, and are therefore not mapped in Figure Coastal bluff areas are susceptible to slope failure due to erosion by wave action. Wave erosion at the base of the bluffs causes oversteeping of the bluff face, which results in block fall-type of slope failures. Block falls occur when the bluff face fails as coherent blocks of formational material. In addition, irrigation and other surface water at the tops of bluffs can cause slope failure. Impacts can be avoided or reduced through setbacks from the bluffs and/or stabilization. Based on the 2004 LRDP, no development is planned to occur close enough to the coastal bluffs to result in substantial impact and, therefore, the potential impact is considered to be less than significant. Mitigation Measures The 2004 LRDP would have a less than significant impact related to soil stability; therefore, no mitigation measures are required. September 2004 UCSD 2004 Long Range Development Plan Final EIR

16 ISSUE 4 EXPANSIVE SOILS Geology and Soils Issue 4 Summary Would implementation of the 2004 LRDP result in the construction located on expansive soils? Impact: Expansive soils may be found on campus; however, they are unlikely to pose a substantial hazard associated with implementation of the 2004 LRDP. Significance Before Mitigation: Less than significant. Mitigation: No mitigation is required. Significance After Mitigation: Less than significant. Standards of Significance Based on Appendix G of the CEQA Guidelines, implementation of the 2004 LRDP may have a significant adverse impact if it would result in construction located on expansive soil, as defined in Table 18-1-B of the Uniform Building Code (1994 or most current edition), creating substantial risks to life or property. Impact Analysis Expansive soils are soils that are high in expansive clays or silts and that swell and shrink with wetting and drying, respectively. This shrinking and swelling can be detrimental to foundations, concrete slabs, flatwork, and pavement. However, proper fill selection, moisture control, and compaction during construction can prevent these soils from causing significant damage. Expansive soils can be treated by removal (typically the upper three feet below finish grade) and replacement with low expansive soils, lime-treatment, and/or moisture conditioning. Expansive soils on campus are prevalent in the Chesterson Series soils. Portions of the Chesterton soils contain clayey subsoils, which may be subject to expansion effects due to the water holding capacity of clay materials. Colluvium is compressible and also usually expansive. The Regents requires compliance with the CBC, which includes provisions for construction on expansive soils. Complying with the provisions of the CBC requires that a geotechnical investigation be performed to provide data for the architect and/or engineer to responsibly design the project. In addition, the campus Office of Facilities Design and Construction requires geotechnical investigations for every applicable project. Continued compliance with the CBC would ensure that this impact would be less than significant. Mitigation Measures The 2004 LRDP would have a less than significant impact related to expansive soils. Therefore, no mitigation measures are required. UCSD 2004 Long Range Development Plan Final EIR September

17 4.5.4 CUMULATIVE IMPACTS AND MITIGATION Geology and Soils Cumulative Issue Summary Would implementation of the 2004 LRDP have a cumulatively considerable contribution to a cumulative geology and soils impact considering past, present, and probable future projects? Cumulative Impact Significance LRDP Contribution Regional exposure of persons to the hazards of Potentially significant. Not cumulatively considerable. seismic ground shaking. Regional exposure of persons to other seismic Less than significant. Not cumulatively considerable. related or geotechnical hazards. Erosion or loss of topsoil in affected watersheds due to development. Potentially significant. Not cumulatively considerable. The geographic context for the analysis of impacts resulting from seismic ground shaking is generally sitespecific, rather than cumulative in nature, because each development site has unique geologic considerations that would be subject to uniform site development and construction standards. In this way, potential cumulative impacts resulting from geological, seismic, and soil conditions would be minimized on a site-bysite basis to the extent that modern construction methods and code requirements provide. Nevertheless, even though adequate study, design, and construction measures can be taken to reduce potential impacts, cumulative development in the region would contribute to the cumulative increase in the number of persons exposed to these hazards (e.g., the general seismic risk that exists throughout southern California). As described above, and unlike some other areas within the region, the UCSD campus is not located within an Earthquake Fault Zone as defined by the Alquist-Priolo Act. All development on campus would continue to comply with the CBC and UC Seismic Safety Policy, which requires the use of the most stringent seismic safety standards, consistent with all applicable regulations. The contribution of the 2004 LRDP to impacts associated with exposing people and property to ground shaking effects is, therefore, considered not to be cumulatively considerable. With regard to other seismic related or geotechnical hazards, the geographic context for analysis of impacts on development is also generally site specific. Nevertheless, when considering the impacts in a larger geographic context, all development on the UCSD campus and in the surrounding jurisdictions are required to undergo analysis of geological and soil conditions applicable to the development site in question. Because restrictions on development would be applied in the event that geological or soil conditions pose a risk to safety, it is anticipated that cumulative impacts from development on soil subject to soil instability, liquefaction, subsidence, and expansive soil would be less than significant and the 2004 LRDP s contribution would not be cumulatively considerable. Impacts from erosion and loss of topsoil from site development and operation can be cumulative in effect within a watershed. The Los Peñasquitos Hydrologic Unit forms the geographic context of cumulative erosion impacts. This analysis accounts for all anticipated cumulative growth within this geographic area as represented by full implementation of the City of San Diego General Plan (which includes UCSD) and the related projects provided by Table 4-1 in Section 4.0. Development at UCSD and throughout the City of San Diego is subject to state and local runoff and erosion prevention requirements, including the applicable provisions of the general construction permit, BMPs, and Phases I and II of NPDES, as well as implementation of fugitive dust control measures of the San Diego Air Pollution Control District. These measures are implemented as conditions of approval for development projects and are subject to continuing enforcement. As a result, it is anticipated that cumulative impacts on the Los Peñasquitos Hydrologic Unit September 2004 UCSD 2004 Long Range Development Plan Final EIR