Section 4.6 Geology and Soils Introduction Environmental Setting. Regional Setting. Geologic Setting

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1 4.6.1 Introduction Section 4.6 Geology and Soils This section describes the geologic and soil characteristics of the project site and the potential geology and soils impacts associated with construction and operation of the proposed project. The analysis in this section is largely based on the Limited Feasibility Level Geological & Geotechnical Evaluation for the Proposed Alta-Oak Creek Mojave Project, prepared by Soils Engineering Inc (SEI) in October of 2008 (SEI, 2008). The complete geotechnical report is provided in Appendix E. A description of the environmental setting (affected environment) for geology and soils is presented below in Section 4.6.2, including discussion of the geologic setting (soils and geologic formations; faults and seismic history), and geologic and seismic hazards (slope stability; soil hazards; faults and seismicity; strong ground shaking; fault rupture; liquefaction). The regulatory setting applicable to geology and soils is presented in Section The impact analysis, including discussion of project impacts and associated mitigation measures, is presented in Section Additional descriptions of erosion and sediment impacts on surface water (e.g., turbidity) and mitigation measures are presented in Section 4.8, Hydrology and Water Quality Environmental Setting Regional Setting The proposed project site is located in the westernmost portion of the Antelope Valley. The project area straddles the desert floor and the adjacent foothills of the Tehachapi Mountains, a short transverse range that connects the southernmost Sierra Nevada Mountains (to the northeast) with the San Emigdio Mountains (to the southwest). Terrain of the project site is mountainous in the west, and generally flat in the east, with a slight slope to the southeast. Geologic Setting Tehachapi Mountains. The Tehachapi Mountains are an east-west trending mountain range at the southern end of the Sierra Nevada which separates the Great Valley from the Mojave Desert. The Tehachapi Mountains have been sheared into this east-west trend by left-lateral fault movement of the Garlock fault which runs near the southern boundary of the range. The Tehachapi Mountains are primarily composed of Mesozoic Quartz monzonite with local lenses of hornblende diorite. The Tehachapi Mountains are also characterized by deeply incised valleys, steep hillsides, and mountains that lie on the eastern side of the Pacific Crest line descending towards the Mojave Desert. Antelope Valley. The Antelope Valley consists of approximately 1,200 square miles of elevated desert terrain, located along the western edge of the Mojave Desert and is primarily an alluviated desert plain containing bedrock hills and low mountains. The rocks of the Antelope Valley are Alta Oak Creek Mojave Project August 2009

2 characterized by relatively flat-lying topography and valley fill deposits. The Antelope Valley is covered primarily by alluvial deposits of Quaternary age: Holocene Alluvium and Pleistocene Older Alluvium. The Holocene alluvial deposits consist of slightly dissected alluvial fan deposits of gravel, sand and clay. The Older Alluvium is located primarily near the margins of the Antelope Valley at the flanks of the Sierra Pelona and Tehachapi Mountains and consists of weakly consolidated, uplifted and moderately to severely dissected alluvial fan and terrace deposits composed primarily of sand and gravel. Soils and Geologic Formations The western project area (Tehachapi Mountains) is underlain by Mesozoic crystalline rocks (quartz monzonites / quartz diorite) with occasional uplifted limestone blocks, while the eastern project area (Antelope Valley / Mojave Desert) is underlain by Quaternary alluvium deposits (Qoa). Near surface soils within the zone of influence of future developments include decomposed granitic rocks, sandy silt, and well-graded sand layers overlying bedrock, which is at or near the surface on the western portion of the project area. The depth of alluvium in the eastern project area is estimated to be more than 50 feet. These sediments were derived in the Tehachapi Mountains and deposited by local drainage. (SEI, 2008) Soils at the proposed project site are classified into three groups (from oldest to youngest): late Paleozoic metamorphic rocks, Mesozoic crystalline rocks, and Quaternary age sedimentary deposits. The crystalline rocks on-site are plutonic (intrusive) igneous rock characterized by mainly quartz monzonite with an occasional metamorphic assemblage known as the Bean Canyon formation. Soils and geologic formations at and near the proposed project site are shown on Figures and and are described in further detail below, based on geologic mapping completed by Dibblee (1963 / 1967) and evaluated by SEI (2008). Quaternary sediments consist of older fanglomerate deposits, exposed within the proposed project site, reaching up the lower portions of the slopes of mountainous terrain to the west and spreading towards the southeast. Recent alluvial deposits are found within the Oak Creek Canyon drainage, as well as smaller and historically recent drainages and erosion features. Quartz Monzonite is commonly exposed on the lower slopes of the Tehachapi Mountains and forms the mountainous terrain of the westerly elevated portion of the proposed project site. This formation is generally a medium- to coarse-grained granitic rock, gray-white when fresh and weathering to buff-white. This formation is generally massive in character. Quartz Diorite formation is similar in physical character to the Quartz Monzonite, differing only in minor mineral makeup. It is a medium- to coarse-grained granitic rock, grayishwhite when fresh and weathering to buff-white, and generally massive in character. Bean Canyon formation is a metamorphic rock, generally consisting of white marble/ limestone and dark plagioclase schist. This formation is a metamorphosed sequence of sedimentary rocks and occurs as a pendant within the intrusive quartz monzonite. This formation is elongated parallel to the mountain front. Alta Oak Creek Mojave Project August 2009

3 I Aspen Environmental Group Alta-Oak Creek Mojave Project Source: Soils Geologic Inc, Figure Regional Geologic Map August 2009

4 Sedimentary deposits of Quanternary age range from coarse-sand gravel and cobble fanglomerate to young alluvium consisting of finer grained sands and silts. These deposits are separated into two units: older alluvial fan deposits of Pleistocene age, and recent alluvium and surficial deposits of Holocene age (SCE, 2008). Older Alluvium at the proposed project site forms a dissected fan of detritus derived from the nearby crystalline rocks of the Tehachapi Mountains. At its upper edge, this fan laps upon the crystalline rocks of the mountains and thickens toward the south-southeast. Recent Alluvium at the proposed project site is generally located in the eastern portion of the proposed project area and within Oak Creek Canyon. These materials are unconsolidated and generally undissected surficial deposits. These sediments generally thin out upslope against the older alluvial deposits and consist of poorly-sorted gravels, as well as sand derived from nearby older alluvium and crystalline rocks of the Tehachapi Mountains. The thickness of these materials ranges between approximately 50 feet to more than 100 feet. As summarized above, the proposed project site is generally composed of sand, gravel, and cobbles with very little to no fine-grained soil. Faults and Seismic History Active faults within 50 miles of the project site include the following: Garlock Fault (West), running through the western portion of the project site; the White Wolf Fault, located approximately 19.2 kilometers to the northwest; the Garlock Fault (East), located approximately 42 kilometers to the northeast; the San Andreas Fault (multiple segments), located approximately 42.5 kilometers to the west; the Pleito Thrust Fault, located approximately 45.6 kilometers to the west; and the San Gabriel Fault, located approximately 58.5 kilometers to the southwest. Regional faults are shown on Figure As shown on Figure 4.6-4, portions of the proposed project site are located within the Garlock Fault Alquist-Priolo Special Study Zone (California Fault Zone). (SEI, 2008) The Garlock and San Andreas Faults are near vertical, active faults along which movements are predominantly horizontal. Movement along the Garlock Fault is estimated as southwesterly at several tens of kilometers, while the land southwest of the San Andreas Fault has moved northwest several hundred kilometers, with respect to the Mojave block. The southwest half of the Mojave block is broken by near vertical faults subparallel to the San Andreas Fault with similar but smaller movements. (SEI, 2008) Following are summaries of the major faults (Garlock and San Andreas) located in the vicinity of the proposed project area. Garlock Fault. This is a major structural break trending east-northeast from its intersection with the San Andreas Fault approximately 23 miles west of the proposed project site. From its intersection with the San Andreas Fault, the Garlock Fault zone extends about 260 kilometers toward Death Valley. The western segment of the Garlock Fault is located alongthe southern perimeter of the Tehachapi Mountains. In this segment, stream channels have been displaced by left slip movement. The western portion of the proposed project site is located within the boundaries of an Alquist-Priolo Special Study Zone (California Fault Alta Oak Creek Mojave Project August 2009

5 Figure Aspen Detailed Geologic Map Environmental Group Source: Soils Geologic Inc, Alta-Oak Creek Mojave Project August 2009

6 Los A ngeles A E(2 1/2 )R S A K e r n White Wolf Fault Garlock Fault Project Site Pielto Fault L o s A n g e l e s San Andreas Fault S B e r n V e n t u r a San Gabriel Fault I Miles Alta-Oak Creek Mojave Project Faults Project Site Counties Figure Regional Fault Map December 2008 August 2009

7 S CURRY ST S GREEN ST SHAWNEE AV ERIE AV CHEYENNE AV HIGHLINE RD NEALE DR LAURA LN TURF ST STEUBER RD HARRIS RD WHITE OAK DR ORCHARD ST STIEKMAN ST ABAJO AV WADE AV 58 EAST HWY TEHACHAPI BLVD JAMESON ST 3RD ST CHANTICO RD 58 WEST HWY SAND CANYON RD DUGAN DR TARPEY DR EMMETT LN WAKEMAN DR SCARPERO DR BLACKBURN CANYON RD DENNISON RD PEARCE DR SUMMERS DR A DANFORD RD JARRETT DR A E(2 1/2) RS Subarea 3 CAMERON RD BLACKPINE LN OAK CREEK RD Subarea 2 OAK CREEK RD Subarea 1 115TH STREET WEST ROBERT RANCH RD TEHACHAPI WILLOW SPRINGS RD I Miles Proposed Wind Turbine Location Project Site Faults Alquist Priolo Zone Figure Alquist Priolo Zone Map December 2008 Alta-Oak Creek Mojave Project August 2009

8 Zone) related to the Garlock Fault. The north branch of the Garlock Fault is considered an active fault, and is a high-angle shear zone with predominant strike slip movement to the west. In the region of the proposed project site, the displacement is unknown, although it is likely to be great (Dibblee, 1967). (SEI, 2008) San Andreas Fault. In general, this high-angle fault trends northwest and was formed and active in Pleistocene time. Many related faults, including the Tylerhorse Fault (3.5 miles southwest of the proposed project site) and the Cottonwood Fault (5.0 miles southwest of the proposed project site), off-set alluvial deposits and are active or potentially active. Several of the regionally related faults, including the Galway Lake and Homestead Valley Faults, have caused earthquakes and ground ruptures (right slip) in 1975 and 1979, respectively. All of these faults are considered part of the San Andreas Fault system. It has not been possible thus far to determine the nature and amount of fault displacement; however, Holocene age movement has been shown on many of these northwesterly trending faults as observed by displacement in alluvial fans and offset lines of drainage (SEI, 2008). Numerous historic earthquakes have affected the Mojave Desert region where the proposed project site is located. Table 4.6-1, below, provides a summary of major known seismic events. Table Historic Seismic Events in the Proposed Project Area Date Name Fault Magnitude Notes 01/09/1857 Fort Tejon Earthquake San Andreas Fault feet of slippage over a 200-mile area, widespread damage 07/21/1952 Arvin/Tehachapi White Wolf Fault 7.7 Extensive damage to buildings and Earthquake 08/22/1952 Bakersfield Earthquake (aftershock of Arvin/Tehachapi) Source: SEI, 2008 White Wolf Fault, 6 miles ESE of Bakersfield highways 5.8 Extensive damage to alreadyweakened structures and multiple surface fissures The majority of recent seismic activity in the vicinity of the proposed project site has occurred along the White Wolf Fault and the San Andreas Fault. Historic earthquakes along the Garlock Fault, which underlies part of the proposed project site, have not occurred within the last 200 years. (SEI, 2008) Geologic and Seismic Hazards Slope Stability The western portion of the proposed project site, situated in the foothills of the Tehachapi Mountains, is characterized by hills and ravines, while the eastern portion of the proposed project site, situated on the desert floor of the Antelope Valley, has a gentle slope to the southeast and appears to be very stable, as determined by SEI (2008). There is a low to moderate potential for rockfalls to impact the western site area in the event of a major earthquake (SEI, 2008). The proposed project site is not located within a State California Seismic Hazard Zone for landslides. In steep areas of the western project site, seismically-induced landslides may occur when ground motion causes unstable or steeply sloping and loosely aggregated soils and rocks to move down-slope under the force of gravity. In the event of a major earthquake, there is a low to moderate potential for rock falls and a low potential for landslides at the proposed project site (SEI, 2008). Alta Oak Creek Mojave Project August 2009

9 The wind turbines for the proposed project would be placed on competent hill tops or ridges with grading conducted to minimize the potential for movement. Soil Hazards Geologic hazards associated with soil characteristics include erosion, expansion ( shrink-swell patterns), and settlement, as described below. Erosion. Soil erosion occurs when surface materials are worn away from the earth s surface due to land disturbance and/or natural factors such as wind and precipitation. The potential for soil erosion is determined by characteristics including texture and content, surface roughness, vegetation cover, and slope grade and length. Wind erosion typically occurs when fine-grained non-cohesive soils are exposed to high velocity winds, while water erosion tends to occur when loose soils on moderate to steep slopes are exposed to high-intensity storm events. As described above in Section (Geologic Setting Soils and Geologic Formations), soils at the proposed project site are generally composed of sand, gravel, and cobbles with little to no fine-grained soils. Due to these soil characteristics, the potential for wind erosion to affect the structural integrity of project features would be low. Additionally, although the western portion of the proposed project site is characterized by slopes of the Tehachapi Mountain foothills, infrastructure associated with the proposed project would not be situated on steep slopes. Expansion. Soils which expand and contract in volume ( shrink-swell pattern) are considered to be expansive, and may cause damage to aboveground infrastructure as a result of density changes that shift overlying materials. Fine-grain clay sediments are most likely to exhibit shrink-swell patterns in response to changing moisture levels. As described above in Section (Geologic Setting Soils and Geologic Formations), geotechnical investigations conducted at the proposed project site have determined that the proposed project site is generally composed of sand, gravel, and cobbles with very little to no fine-grained soil. These characteristics indicate a low probability of shrink-swell soil behavior at the proposed project site. Settlement. The settlement of soils is characterized by sinking or descending soils that occurs as the result of a heavy load being placed on underlying sediments, and may be triggered by seismic events. The potential for seismically induced settlement at the proposed project site is considered low to moderate. Minor settlement (less than one inch) could occur at the proposed project site in the event of a major earthquake (SEI, 2008). Faults and Seismicity As described in Section (Geologic Setting Faults and Seismic History), the proposed project is crossed by an Alquist-Priolo Special Study Zone. The north branch of the Garlock fault is considered an active fault (known to have been active during Holocene time, in the past 10,000 years) and crosses the north-western portion of the project site. A number of other active faults are located within a 50-mile radius of the proposed project site. SEI (2008) conducted a computer modeling analysis to evaluate the affect that a major earthquake may have on the proposed project site. The results of this analysis are presented below, in Table The SEI analysis summarized in Table estimates that a maximum peak ground acceleration of g (gravitational acceleration) would be felt at the proposed project site as a result of a Alta Oak Creek Mojave Project August 2009

10 maximum earthquake of magnitude 7.1 on the Garlock Fault (West), which crosses through the western portion of the proposed project area. (SEI, 2008) Table Modeled Effects of Seismic Potential in the Proposed Project Area Fault Distance from Proposed Project (km) Maximum Earthquake Magnitude (Mw) Maximum Peak Ground Acceleration (g) Estimated Site Intensity (MM) Garlock (West) < IX X White Wolf VIII IX Garlock (East) VII VIII San Andreas VII VIII (various segments) Pleito Thrust VII San Gabriel VII Source: SEI, 2008 The Mojave Desert region, including the proposed project site, is a geologically young and seismically active area. The uplift of the Tehachapi Mountains and the San Gabriel Mountains, as well as associated seismic activity, is the result of movement along the San Andreas and Garlock Fault systems. In addition to the Garlock Fault (active, north branch) passing through the western portion of the proposed project site, other active or potentially active fault traces such as the Cottonwood Fault and the Tylerhorse Fault are located in close proximity to the proposed project site. (SEI, 2008) Strong Ground Shaking Strong ground shaking from an earthquake can result in damage associated with landslides, ground lurching, structural damage, and liquefaction. The Garlock Fault has an estimated slip rate of 6 millimeters per year and a maximum earthquake magnitude of 7.1 (SEI, 2008). As such, the proposed project site could experience strong ground shaking caused by moderate to strong earthquakes during the lifetime of the proposed project. In-depth geotechnical study of final turbine locations would be conducted prior to implementation of the proposed project, in order to ensure proper design and compliance with applicable building codes and geotechnical requirements associated with the potential for strong ground shaking. Fault Rupture Ground surface rupture along an earthquake fault may cause damage to aboveground infrastructure and other features. The State of California has mapped known active faults that may cause surface fault rupture in inhabited areas as part of the Alquist-Priolo Earthquake Fault Zoning Act. The Garlock Fault, which crosses through part of the proposed project site, is mapped as an Earthquake Fault Zone; the construction of occupied structures within an Earthquake Fault Zone is regulated under the Alquist-Priolo Earthquake Fault Zoning Act and must conform to strict building codes. However, development of the proposed project would not be subject to the regulations of the Alquist-Priolo Special Studies Zones Act as long as the project does not include the construction of habitable structures in the Alquist-Priolo Earthquake Fault Zones. Alta Oak Creek Mojave Project August 2009

11 In the proposed project area, there is potential for ground surface rupture to occur due to the presence of faults that have displaced recent alluvial deposits that cross the project site. Ground rupture and ground failure could occur within 500 feet of an active trace of the Garlock Fault. This potential can be mitigated through identification of fault locations during a comprehensive geologic investigation of the property combined with prudent site planning, which would preclude locating critical structures on or immediately adjacent to an active fault trace. (SEI, 2008) Liquefaction Liquefaction is the phenomenon in which saturated granular sediments temporarily lose their shear strength during periods of earthquake-induced strong groundshaking. In order to determine the liquefaction susceptibility of a region, three major factors must be analyzed. These include: (1) the density and textural characteristics of the alluvial sediments; (2) the intensity and duration of groundshaking; and (3) the depth to groundwater. Groundwater was encountered in two of the geotechnical soil borings conducted by SEI at the proposed project site, at depths of 41 and 46 below ground surface (SEI, 2008). Subsurface lithology in this area includes dense decomposed granitic material and rock. Considering the soil types, geology, and the average groundwater level at the project site, the potential for liquefaction is considered low (SEI, 2008) Regulatory Setting Federal Geologic resources and geotechnical hazards are governed primarily by local jurisdictions. The conservation elements and seismic safety elements of city and county general plans contain policies for the protection of geologic features and avoidance of hazards. CEQA is the major environmental statute that guides the design and construction of projects on non-federal lands in California. This statute sets forth a specific process of environmental impact analysis and public review. In addition, the project proponent must comply with other applicable State and local applicable statutes, regulations and policies. Relevant and potentially relevant statutes, regulations and policies are discussed below. Clean Water Act The Clean Water Act (CWA) (33 U.S.C. Section 1251 et seq.), formerly the Federal Water Pollution Control Act of 1972, was enacted with the intent of restoring and maintaining the chemical, physical, and biological integrity of the waters of the United States. The CWA requires states to set standards to protect, maintain, and restore water quality through the regulation of point source and certain non-point source discharges to surface water. Those discharges are regulated by the National Pollutant Discharge Elimination System (NPDES) permit process (CWA Section 402). Projects that disturb one or more acres of land are required to obtain NPDES coverage under the NPDES General Permit for Storm Water Discharges Associated with Construction Activity (General Permit), Order No DWQ. The General Permit requires the development and implementation of a Storm Water Pollution Prevention Plan (SWPPP), which includes Best Management Practices (BMPs) to protect stormwater runoff. Alta Oak Creek Mojave Project August 2009

12 Requirements of the federal CWA and associated SWPPP requirements are described in further detail in Section 4.8 (Hydrology and Water Quality). State California Environmental Quality Act (CEQA) (Pub. Resource Code sections ). CEQA was adopted in 1970 and applies to most public agency decisions to carry out, authorize or approve projects that may have adverse environmental impacts. CEQA requires that agencies inform themselves about the environmental effects of their proposed actions, consider all relevant information, provide the public an opportunity to comment on the environmental issues, and avoid or reduce potential environmental harm whenever feasible. Relevant CEQA sections include those for protection of geological and mineral resources and the protection of soil from erosion. The Alquist Priolo Earthquake Fault Zoning Act of 1972 The Alquist-Priolo Earthquake Fault Zoning Act of 1972, (formerly the Special Studies Zoning Act) regulates development and construction of buildings intended for human occupancy to avoid the hazard of surface fault rupture. In accordance with this law, the California Geological Survey maps active faults and designates Earthquake Fault Zones along mapped faults. This Act groups faults into categories of active, potentially active, and inactive. Historic and Holocene age faults are considered active, Late Quaternary and Quaternary age faults are considered potentially active, and pre-quaternary age faults are considered inactive. These classifications are qualified by the conditions that a fault must be shown to be sufficiently active and well defined by detailed site-specific geologic explorations in order to determine whether building setbacks should be established. Any project that involves the construction of buildings or structures for human occupancy, such as an operation and maintenance building, is subject to review under the Alquist- Priolo Earthquake Fault Zoning Act, and any structures for human occupancy must be located at least 50 feet from any active fault. The Seismic Hazards Mapping Act (the Act) of 1990 In accordance with Public Resources Code, Chapter 7.8, Division 2, the California Department of Conservation, Division of Mines and Geology [now the California Geological Survey (CGS)] is directed to delineate Seismic Hazard Zones. The purpose of the Act is to reduce the threat to public health and safety and to minimize the loss of life and property by identifying and mitigating seismic hazards, such as those associated with strong ground shaking, liquefaction, landslides, other ground failures, or other hazards caused by earthquakes. Cities, counties, and state agencies are directed to use seismic hazard zone maps developed by CGS in their land-use planning and permitting processes. In accordance with the Seismic Hazards Mapping Act, site-specific geotechnical investigations must be performed prior to permitting most urban development projects within seismic hazard zones. Alta Oak Creek Mojave Project August 2009

13 The California Building Code (CBC, 2008) The State of California provides minimum standards for building design through the California Building Code (CBC). The CBC is based on the Uniform Building Code (UBC), which is used widely throughout the United States (generally adopted on a State-by-State or district-by-district basis), and has been modified for conditions within California. In 2008, a revised version of the CBC took effect. In accordance with the CBC, a grading permit is required if more than 50 cubic yards of soil is moved during implementation of a proposed project. Chapter 16 of the CBC contains definitions of seismic sources and the procedure used to calculate seismic forces on structures. Kern County Construction and operation of the proposed project is subject to policies and regulations contained within General and Specific Plans including the Kern County General Plan, the Cameron Canyon Specific Plan, the Kern County Zoning Ordinance, and the Kern County Code of Building Regulations, which include policies for the avoidance of geologic hazards and/or the protection of unique geologic features, as well as for the preservation of paleontologic resources (please see Section 4.5 [Cultural Resources] for discussion of paleontologic resources relevant to the proposed project). The policies, goals, and implementation measures in the Kern County General Plan for geology and soils applicable to the project are provided below. The Kern County General Plan contains additional policies, goals, and implementation measures that are more general in nature and are not specific to development such as the proposed project. These measures are not listed below, but, as stated in Chapter 2, (Introduction), all policies, goals, and implementation measures in the Kern County General Plan and Cameron Canyon Specific Plan are incorporated by reference. Kern County General Plan 1.3 Physical and Environmental Constraints Policy 1. Kern County will ensure that new developments will not be sited on land that is physically or environmentally constrained (Map Code 2.1 [Seismic Hazard], Map Code 2.2 [Landslide], Map Code 2.3 [Shallow Groundwater], Map Code 2.5 [Flood Hazard], Map Codes from , Map Code 2.10 [Nearby Waste Facility], and Map Code 2.11 [Burn Dump Hazard]) to support such development unless appropriate studies establish that such development will not result in unmitigated significant impact. Policy 6. Regardless of percentage of slope, development on hillsides will be sited in the least obtrusive fashion, thereby, minimizing the extent of topographic alteration required and reducing soil erosion while maintaining soil stability. Policy 7. Ensure effective slope stability, wastewater drainage, and sewage treatments in areas with steep slopes are adequate for development. 1.9 Resource (Land Use, Open Space, and Conservation Element) Policy 17. Lands classified as MRZ-2, as designated by the State of California, should be protected from encroachment of incompatible land uses. Alta Oak Creek Mojave Project August 2009

14 4.3 Seismically Induced Surface Rupture, Ground Shaking, and Ground Failure (Safety Element) Policy 1. The County shall require development for human occupancy to be placed in a location away from an active earthquake fault in order to minimize safety concerns. 4.5 Landslides, Subsidence, Seiche, and Liquefaction (Safety Element) Policy 1. Determine the liquefaction potential at sites in areas of shallow groundwater (Map Code 2.3) prior to discretionary development and determine specific mitigation to be incorporated into the foundation design, as necessary, to prevent or reduce damage from liquefaction in an earthquake. Policy 2. Route major lifeline installations around potential areas of liquefaction or otherwise protect them against significant damage from liquefaction in an earthquake. Policy 3. Reduce potential for exposure of residential, commercial, and industrial development to hazards of landslide, land subsidence, liquefaction, and erosion. 5 Energy Element Policy 2. All wind energy development shall be subject to the development standards of Kern County Zoning Ordinance. Cameron Canyon Specific Plan Section I Physical Constraints Policy 1. Kern County will not permit new developments to be sited on land which is environmentally unsound to support such development. Policy 2. Zoning and other land use controls will be used to regulate and, in some instances, to prohibit development in areas with physical hazard constraints. Policy 5. Development proposed in areas with steep slopes will be subject to the standards of the Hillside Development Ordinance. Regardless of the percentage of slope, development on hillsides will be required to be sited in the least obtrusive fashion minimizing the extent of topographic alteration. Policy 7. Development on highly erosive soils shall be limited and measures incorporated in order to reduce erosion material. The expertise of the Tehachapi Resource Conservation District shall be employed whenever possible to aid in the design of future development of all kinds. Section VI Resource Goal 1. To contain new development within an area large enough to meet projected demand, but in locations that will not impair rangeland and other resource uses. Goal 2. To protect area soils from erosion by encouraging proper soil management practices as defined by the Soil Conservation Service, by ranchers, and wind farm developers in cooperation with the Tehachapi resource Conservation District. Goal 4. To ensure that any earthwork or grading is adequately designed for drainage and erosion control and site rehabilitation. Goal 5. To separate new wind farm sites from residential areas, thereby protecting established residences. Alta Oak Creek Mojave Project August 2009

15 Policy 6. No new WE (Wind Energy Combining) zoning shall be allowed and new wind farm development will be discouraged within the Cameron Creek Canyon. The boundaries of the Cameron Creek Canyon are delineated by the ridgelines shown on the adopted Specific Plan. Policy 7. Wind farm developers will be encouraged to minimize the environmental effects of their installations. Wind farm development within the plan boundaries shall require prior approval of the WE (Wind Energy Combining) zoning. No new wind farm development shall be allowed by conditional use permit within the Specific Plan boundaries. Section X Seismic Safety and Safety Element Goal 1. To reduce the potential for loss of life, injury, and property damage resulting from natural disasters and environmental factors by limiting and regulating in areas of known hazards. Goal 5. To provide for various land uses in accordance with the capability of the land to safely accommodate such uses. Policy 3. Emphasis will be given to soil capabilities in reviewing development requests in order to avoid construction of structures or roads on soils not suited for those purposes. Policy 4. Development will also be guided by the policies of Section I of this plan that relates to physical constraints. Kern County Zoning Ordinance (Title 19 of the Ordinance Code of Kern County) Chapter Wind Energy Combining District The WE Combining District contains the following sections applicable to geology and soils: Section (A): All necessary building and grading permits shall be obtained from the Kern County Planning Department. For construction and permit purposes, all wind turbine generator towers shall conform to the regulations of the applicable seismic zone of the Uniform Building Code (UBC) and the applicable ground shaking zone. Section (K): Prior to issuance of any grading permit, a plan for the mitigation of potential soil erosion and sedimentation shall be prepared by a California registered civil engineer or other professional and submitted for the approval by the Director of the Engineering and Survey Services Department. Section (L): A minimum of on-site roadways shall be constructed. Temporary access roads utilized for initial machine installation shall be revegetated to a natural condition after completion of machine installation. The project proponent shall submit a plan of all proposed roads, temporary and permanent, for approval by the Planning Director prior to the issuance of any building permits. Section (M): Construction of any slopes steeper than four to one (4:1) shall be prohibited unless specifically authorized by the Kern County Planning Department and mitigation is provided. Section (N): Soil erosion and sedimentation control plan, including revegetation plan, as provided in Section (grading permits only). Alta Oak Creek Mojave Project August 2009

16 Kern County Code of Building Regulations (Title 17 of the Ordinance Code of Kern County) All construction in Kern County is required to conform to the Kern County Building Code (Chapter 17.08, Building Code, of the Kern County Code of Regulations). Kern County has adopted the Uniform Building Code (UBC), 2007 Edition, with some modifications and amendments. The entire County is in Seismic Zone 4, a designation previously used in the UBC to denote the areas of highest risk to earthquake ground motion. California has an Unreinforced Masonry program that details seismic safety requirements for Zone 4. Seismic provisions associated with Seismic Zone 4 have been adopted. Chapter Kern County Grading Code. The purpose of the Kern County Grading Code is to safeguard life, limb, property and the public welfare by regulating grading on private property. All requirements of the Kern County Grading Code will be applied during implementation of the proposed project. All required grading permit(s) shall be obtained prior to commencement of construction activities. Sections of the Grading Code that are particularly relevant to geology and soils are provided below. Section Erosion control. A. Slopes. The faces of cut and fill slopes shall be prepared and maintained to control against erosion. This control may consist of effective planting. The protection for the slopes shall be installed as soon as practicable and prior to calling for final approval. Where cut slopes are not subject to erosion due to the erosion-resistant character of the materials, such protection may be omitted. B. Other Devices. Where necessary, check dams, cribbing, riprap or other devices or methods shall be employed to control erosion and provide safety. C. Temporary Devices. Temporary drainage and erosion control shall be provided as needed at the end of each work day during grading operations, such that existing drainage channels would not be blocked. Dust control shall be applied to all graded areas and materials and shall consist of applying water or another approved dust palliative for the alleviation or prevention of dust nuisance. Deposition of rocks, earth materials or debris onto adjacent property, public roads or drainage channels shall not be allowed. Section Grading inspection. A. General. All grading operations for which a permit is required shall be subject to inspection by the building official. Professional inspection of grading operations and testing shall be provided by the civil engineer, soils engineer and the engineering geologist retained to provide such services in accordance with Subsection (E) for engineered grading and as required by the building official for regular grading. B. Civil Engineer. The civil engineer shall provide professional inspection within such engineer s area of technical specialty, which shall consist of observation and review as to the establishment of line, grade and surface drainage of the development area. If revised plans are required during the course of the work they shall be prepared by the civil engineer. Alta Oak Creek Mojave Project August 2009

17 C. Soils Engineer. The soils engineer shall provide professional inspection within such engineer s area of technical specialty, which shall include observation during grading and testing for required compaction. The soils engineer shall provide sufficient observation during the preparation of the natural ground and placement and compaction of the fill to verify that such work is being performed in accordance with the conditions of the approved plan and the appropriate requirements of this chapter. Revised recommendations relating to conditions differing from the approved soils engineering and engineering geology reports shall be submitted to the permittee, the building official and the civil engineer. D. Engineering Geologist. The engineering geologist shall provide professional inspection within such engineer s area of technical specialty, which shall include professional inspection of the bedrock excavation to determine if conditions encountered are in conformance with the approved report. Revised recommendations relating to conditions differing from the approved engineering geology report shall be submitted to the soils engineer. E. Permittee. The permittee shall be responsible for the work to be performed in accordance with the approved plans and specifications and in conformance with the provisions of this Code, and the permittee shall engage consultants, if required, to provide professional inspections on a timely basis. The permittee shall act as a coordinator between the consultants, the contractor and the building official. In the event of changed conditions, the permittee shall be responsible for informing the building official of such change and shall provide revised plans for approval. F. Building Official. The building official may inspect the project at the various stages of the work requiring approval to determine that adequate control is being exercised by the professional consultants. G. Notification of Noncompliance. If, in the course of fulfilling their responsibility under this chapter, the civil engineer, the soils engineer, or the engineering geologist finds that the work is not being done in conformance with this chapter or the approved grading plans, the discrepancies shall be reported immediately in writing to the permittee and to the building official. Recommendations for corrective measures, if necessary, shall also be submitted. H. Transfer of Responsibility. If the civil engineer, the soils engineer, or the engineering geologist of record is changed during the course of the work, the work shall be stopped until: 1. The civil engineer, soils engineer, or engineering geologist, has notified the building official in writing that they will no longer be responsible for the work and that a qualified replacement has been found who will assume responsibility. 2. The replacement civil engineer, soils engineer, or engineering geologist notifies the building official in writing that they have agreed to accept responsibility for the work Impacts and Mitigation Measures This section describes the methodology used in conducting the CEQA impact analysis for geology and soils, the thresholds of significance used in assessing impacts to geology and soils, and the assessment of impacts to geology and soils, including relevant mitigation measures. Alta Oak Creek Mojave Project August 2009

18 Methodology This section describes the potential geology and soils impacts associated with development of the proposed project. This analysis first established baseline conditions for the affected environment relevant to geology and soils, as presented above in Section (Environmental Setting). These baseline conditions were evaluated based on their potential to be affected by construction activities as well as operation and maintenance activities for the proposed project. As described in Sections 3.7 (Construction), 3.8 (Operation and Maintenance Activities), and 3.9 (Decommissioning and Repowering), activities that are reasonably expected to occur throughout the life of the proposed project, including construction and installation of wind turbines, operation and maintenance, and decommissioning, may extend over a period of approximately 30 years. The predicted interactions between the affected environment and project activities are evaluated based on the significance criteria identified below (Thresholds of Significance). Thresholds of Significance The Kern County CEQA Implementation Document and Kern County Environmental Checklist state that a project would have a significant impact on Geology and Soils 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 ground shaking; Seismic-related ground failure, including liquefaction; or Landslides. Result in substantial soil erosion or 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. Be located on expansive soil, as defined in Section of the California Building Code (2007), 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 of wastewater. Project Impacts Impact 4.6 1: Expose people or structures to substantial adverse effects involving the rupture of a known earthquake fault. Wind energy facilities associated with the proposed project would be subject to hazards of surface fault rupture at crossings of the active faults identified in Section 4.6.2, particularly as related to the Garlock Fault. The Alquist-Priolo Earthquake Fault Zone (EFZ) Map for the Garlock, California Quadrangle indicates the northwestern portion of the project site is in a designated earthquake fault zone, associated with the Garlock Fault. Damage to wind turbines and associated Alta Oak Creek Mojave Project August 2009

19 project facilities could occur from direct rupture along the Garlock Fault, where it crosses through the proposed project site. The project would include an operations and maintenance facility which would be occupied by staff. Additionally, structural damage to wind turbines, overhead transmission lines, and other associated facilities could injure workers at the proposed project site. Under the Alquist-Priolo Earthquake Fault Zoning Act, no commercial or industrial structures may be located within an EFZ delineated on an official map unless geological investigations are conducted on the site. Adherence to CBC standards would reduce the potential for structural damage to facilities and corollary indirect impacts associated with seismic-related ground rupture to the extent feasible. Nevertheless, given the proximity of the project site to the Garlock Fault and the overall seismic activity in the region, structures on the project site may be subject to moderate to severe ground shaking. This may result in structural damage. Therefore, impacts from seismic hazards are considered potentially significant and mitigation would be required. Mitigation Measures MM 4.6-1: Prior to the issuance of building or grading permits, the project proponent shall conduct a full geotechnical study to evaluate soil conditions and geologic hazards on the project site and submit it to the Kern County Engineering and Survey Services Department for review and approval. The geotechnical study must be signed by a California-registered professional engineer and must identify the following: Location of fault traces and potential for surface rupture; Potential for seismically induced ground shaking, liquefaction, landslides, differential settlement, and mudflows; Stability of existing cut-and-fill slopes; Collapsible or expansive soils; Foundation material type; Potential for wind erosion, water erosion, sedimentation, and flooding; Location and description of unprotected drainage that could be impacted by the proposed development; and Recommendations for placement and design of facilities, foundations, and remediation of unstable ground. MM 4.6-2: MM 4.6-3: The project proponent shall determine the final siting of project facilities based on the results of the geotechnical study and implement recommended measures to minimize geologic hazards. The project proponent shall not locate project facilities on or immediately adjacent to a fault trace. The Kern County Engineering and Survey Services Department will evaluate any final facility siting design developed prior to the issuance of any building or grading permits to verify that geological constraints have been avoided. Utility lines crossing potentially active faults shall be designed to withstand vertical and horizontal displacement. If determined necessary by the findings of the sitespecific geotechnical study, the project proponent shall remove and replace shrinkswell soils with a non-expansive or non-collapsible soil material. Alta Oak Creek Mojave Project August 2009

20 Level of Significance after Mitigation Impact would be less than significant. Impact 4.6 2: Expose people or structures to substantial adverse effects involving strong seismic ground shaking. As described in Section 4.6.2, the Garlock Fault, which is considered an active fault, crosses through the northwestern portion of the project site and other active and potentially active faults are located within 50 miles of the proposed project site, as described in Table The proposed project site would likely experience strong ground shaking resulting from moderate to strong earthquakes during the lifetime of the project. While the shaking would be less severe from an earthquake that originates farther from the project site, the effects could potentially be damaging to wind energy infrastructure. It is likely that the proposed project would be subjected to at least a moderate or larger earthquake occurring close enough to produce strong ground shaking at the project location. Therefore, this impact is considered potentially significant and mitigation would be required. Mitigation Measures Implement MM through MM MM 4.6-4: The project proponent shall design wind turbines and all associated infrastructure to withstand substantial ground shaking. All project facilities shall be designed in accordance with applicable California Building Code (CBC) seismic design standards, Kern County Building Code, Chapter 17, and as recommended by a California registered professional engineer in the site-specific geotechnical review. Level of Significance after Mitigation Impact would be less than significant. Impact 4.6 3: Expose people or structures to substantial adverse effects involving seismic related ground failure, including liquefaction. Portions of the proposed project site are located within the Garlock Fault Alquist-Priolo Special Study Zone (California Fault Zone). The proposed project would not include residences, but it would include an operations and maintenance building that would periodically be used by personnel to complete operations and maintenance activities. Seismic-related ground failure has the potential to result in surface rupture at or near the proposed project site, due to the presence of faults that have displaced recent alluvial deposits in the project area. Ground rupture and ground failure could occur within 500 feet of an active trace of the Garlock Fault, as described in Section 4.6.2, and such event(s) could potentially result in damage to project facilities/structures. Seismic event(s) also have the potential to result in liquefaction, which occurs when saturated granular sediments temporarily lose their shear strength. However, due to subsurface lithology and depth to groundwater at the proposed project site, the potential for liquefaction to occur is considered low. Impacts from seismic-related ground failure would be considered potentially significant and mitigation would be required. Alta Oak Creek Mojave Project August 2009