D.6 Geology and Soils

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1 This section addresses the Proposed Project and alternatives as they would affect geology and soils. Section D.6.1 provides a description of the environmental setting, and the applicable plans, regulations, and requirements are introduced in Section D.6.2. An analysis of the Proposed Project impacts is presented in Section D.6.3, and analysis of geology and soils impacts related to the project alternatives is presented in Sections D.6.4 through D.6.6. D.6.1 Environmental Setting Environmental Baseline and Resources Baseline geologic, seismic and soils information for the Proposed Project and surrounding area were collected from literature, GIS data, and online materials. All sources used for the purposes of characterizing baseline conditions and conducting this analysis are referenced. The literature and data review was supplemented by a brief field reconnaissance of the proposed site. The literature review and field reconnaissance focused on the identification of specific geologic hazards. Regional Overview The Proposed Project site is located in San Gorgonio Pass that connects Yucaipa Valley to the west and the upper Coachella Valley to the east. The Pass area is an east-west trending valley between the San Bernardino Mountains on the north and the San Jacinto Mountains to the south and lies at the geologic junction of Transverse Ranges and Peninsular Ranges geomorphic provinces of California. Environmental Setting of the Project Topography The project site, including the biomass storage area, is located on an alluvial fan surface that slopes gently from elevation 2070 to 2050 feet. Smith Creek wash bounds the east side of the project site. Smith Creek lies at the base of a steep slope that rises to the south to Barker Peak at elevation 4357 feet, representing the north end of the San Jacinto Mountains. Smith Creek flows east to join San Gorgonio River near Cabazon. Geology San Gorgonio Pass is an east-trending lowland that is covered by alluvial fan deposits that mainly are derived from the San Bernardino Mountains to the north. The alluvial fan deposits at the surface overlie older alluvium and alluvial fan deposits deposited by the southward prograding fans (Rewis and others, 2006) that are superimposed on the local streams that drain San Gorgonio Pass, such as Smith Creek. These materials consist of unconsolidated layers of sand, gravelly sand and gravel. Thin, discontinuous layers of clay, silt and fine grained sand occur locally (Rewis and others, 2006). The alluvial fan deposits range in age from Recent to late Pleistocene and are roughly estimated to be 200 to 400 feet thick at the Proposed Project site (Rewis and others, 2006). Topographic maps and aerial photographs indicate that gravel mining occurred at the biomass storage area site. It is unclear if the area has been partly filled (imported material for artificial fill) to restore the ground surface and if so the characteristics of the fill material are unknown. Draft EIR D.6-1 June 2008

2 The unconsolidated alluvial deposits overly bedrock of the San Jacinto Mountains block located south of the Proposed Project site. Metasedimentary rock (quartzite, schist, and gneiss) and granitic rocks form the bold ridge south and east of Smith Creek. These pre-batholithic rocks are older than the Jurassic and Cretaceous granitoid (granodiorite, quartz diorite, tonalite) rocks that intruded them and comprise much of the San Jacinto Mountains and occur as screens and large bodies. Faults and Seismicity The junction of the Peninsular Ranges and Transverse Ranges geomorphic provinces is a structurally complex area dominated by the San Andreas Fault Zone and several related faults. The San Andreas is considered to be the boundary between the Pacific and North American tectonic plates and is generally a right-lateral strike-slip fault. The main strand of the San Andreas fault in southern California consists of two segments: (1) the Mojave Desert segment that mainly separates rocks of San Gabriel Mountains-type from rocks of San Bernardino Mountains-type, and (2) the Coachella Valley segment that separates rocks of Peninsular Rangestype from rocks of San Bernardino Mountains- and San Gabriel Mountains-type. In the San Gorgonio Pass region the San Andreas fault displays a left step from the Coachella Valley segment to the Mojave segment and trends east-west rather than northwest. This left step formed a structural knot as the San Bernardino Mountains block projected across the fault trace during the Pleistocene (Matti and others, 1992). The knot has resulted in both compressional (shortening) and extensional (expansion) forces that have caused many of the unusual structural features of the area, (Matti and others, 1992). These features include the uplift of the San Bernardino Mountains and the presence of thrust faults and wrench faults. The San Andreas fault strands in the area include the Banning fault, Mission Creek, Mill Creek, and San Gorgonio Pass fault. The Quaternary San Gorgonio Pass fault forms a saw tooth or zig-zag pattern along the low hills north of Beaumont and Banning reflecting the shallow north dip of the reverse and thrust faults and right-lateral wrench faults (Matti and others, 1992). The older sedimentary rocks (Pliocene-Pleistocene) deposits that form the hills are folded and cut by north-dipping low-angle faults and wrench faults of the San Gorgonio Pass Fault zone (Matti and others, 1992).The San Gorgonio Pass fault has demonstrated Holocene age offset on the Millard Canyon fan (Matti and others, 1992) and is considered an active fault. The Banning fault and the San Gorgonio Pass fault are about four miles north of the Proposed Project site. No known active faults pass through the project site. Inactive faults within the San Jacinto Mountains block include the Lawrence fault located five miles south of the site. Northwestern Riverside County, like much of southern California, is crossed by numerous active and potentially active faults. Regional faults are depicted on Figure D.6-1. The Beaumont Plain fault zone consists of northwest trending en echelon faults with east facing scarps in late Pleistocene deposits that accommodates extensional forces (Matti and others, 1992). The fault zone is inactive or potentially active and is located on the west side of Beaumont. Finally, buried faults are postulated from groundwater level data that indicate the presence of subsurface barriers (Rewis and others, 2006). The Banning Barrier fault, located about one mile north of the project site, is inferred to be a northdipping reverse fault, without surface expression, and inactive (Rewis and others, 2006). An inactive, pre- Quaternary fault known as the Lawrence fault cuts the metasedimentary rock in the northern San Jacinto Mountains about 1.5 miles south of the site (Rewis and others, 2006). Seismicity in the San Gorgonio Pass region is not associated with strands of the San Andreas fault. A deep wedge of seismicity in San Gorgonio Pass is caused by reverse and thrust fault mechanisms but also includes left-lateral and right-lateral mechanisms, and defines the deepest (22 km) seismicity known from southern California. June 2008 D.6-2 Draft EIR

3 PREPARED BY Liberty XXIII Renewable Energy Power Plant Project Figure D.6-1 Regional Fault Map Aspen Environmental Group June 2008 D.6-3 Draft EIR

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5 Figure D.6-1 show locations of active and potentially active faults (representing possible seismic sources) in the region surrounding the project area. Active and potentially active faults that are significant potential seismic sources are presented in Table D.6-1. Faults can be classified as historically active, active, potentially active, or inactive, based on the following criteria (CGS, 1999): Faults that have generated earthquakes accompanied by surface rupture during historic time (approximately the last 200 years) and faults that exhibit aseismic fault creep are defined as Historically Active. Faults that show geologic evidence of movement within Holocene time (approximately the last 11,000 years) are defined as Active. Faults that show geologic evidence of movement during the Quaternary (approximately the last 1.6 million years) are defined as Potentially Active. Faults that show direct geologic evidence of inactivity during all of Quaternary time or longer are classified as Inactive. Although it is difficult to quantify the probability that an earthquake will occur on a specific fault, this classification is based on the assumption that if a fault has moved during the Holocene epoch, it is likely to produce earthquakes in the future. Blind thrust faults do not intersect the ground surface, and thus they are not classified as active or potentially active in the same manner as faults that are present at the earth s surface. Blind thrust faults are seismogenic structures and thus the activity classification of these faults is predominantly based on historic earthquakes and microseismic activity along the fault. Since periodic earthquakes accompanied by surface displacement can be expected to continue in the study area through the lifetime of the project, the effects of strong groundshaking and fault rupture are of primary concern to safe operation of the proposed transmission line and associated facilities. Table D.6-1. Significant Active and Potentially Active Faults in the Project Area Name Closest Distance to Estimated Max. Earthquake Project Route (miles) 1 Magnitude 2,3 Fault Type 3 San Andreas Fault Zone, Active, right-lateral strike slip including Banning Fault San Gorgonio Pass Fault Active, reverse, thrust and right-lateral wrench Beaumont Plain Fault Zone 9 NA Potentially Active & Unknown, normal slip San Jacinto Fault Zone Active, right-lateral strike slip Table Notes: 1) Information primarily derived from Blake ) Maximum Earthquake Magnitude the maximum earthquake that appears capable of occurring under the presently known tectonic framework, using the Richter scale. 3) Fault parameters from CGS Revised 2002 California Probabilistic Seismic Hazard Maps report, Appendix A California Fault Parameters. Fault Rupture. Fault rupture is typically defined as the point on the ground surface where earthquake-related offsets are manifested. Although generally limited in lateral extent, fault offset can induce profound damage to man-made structures. Mitigation of damage through structural design is generally infeasible, so hazard reduction efforts have concentrated in defining the location of active fault traces, and providing setbacks. Historic fault rupture has occurred on both the San Andreas and San Jacinto Fault Zones. Strong Ground Shaking. Perhaps the most important single factor to be considered in the seismic design of electric power plants is the amount and type of potential ground shaking. The seismic waves associated with the rupture along a fault plane result in surface ground acceleration or shaking. This ground shaking generally causes the majority of damage to structures and loss of life. The level of shaking is dependent on many factors, including the size of the earthquake, relative distance, orientation of structures with respect to the fault rupture Draft EIR D.6-5 June 2008

6 plane, and nature of the underlying soils or bedrock. The U.S. Geological Survey and California Geological Survey have generated regional maps depicting peak horizontal ground acceleration through their Probabilistic Seismic Hazards Assessment (PSHA) Program. Ground acceleration is expressed as a probabilistic seismic hazard (10 percent probability of exceedance in a 50 year period) for firm ground conditions. The regional map for northern Riverside County shows the San Gorgonio Pass area is located within the 0.6 to 0.7 gravity (g) contour. Ground motions may be even greater on alluvial sediments, which underlie the Proposed Project (CGS, 2007). A review of historic earthquake activity from 1800 to 2005 indicates that many earthquakes of M6.0 or greater have occurred within 50 miles of the Proposed Project site (CGS, 2005). The 1986 M5.9 North Palms Springs Earthquake is included on the list due to its close proximity to the project site and the significant damage caused at nearby facilities. Figure D.6-1 shows locations of historic earthquakes in the project area and surrounding region. A summary of significant M6.0 or greater earthquake events is presented in Table D.6-2. Table D.6-2. Significant Historic Earthquakes Affecting the Project Area Date Earthquake Name or General Location Fault Involved, if Known Magnitude 1 Approximate Distance from Project Site 1 San Jacinto miles southwest December 25, 1899 San Jacinto Fault Earthquake, located southeast of San Jacinto April 21, 1918 San Jacinto Earthquake San Jacinto miles southwest December 4, 1948 Desert Hot Springs Earthquake Banning or South San miles east Andreas July 8, 1986 North Palms Springs Earthquake Banning or Garnet Hill miles northeast April 23, 1992 Joshua Tree Eureka Peak miles northeast June 28, 1992 Landers Earthquake Johnson Valley, Landers, miles northeast Homestead Valley, Emerson, Camp Rock, and others June 28, 1992 Big Bear Earthquake (aftershock of the Landers Earthquake) Table Notes: Source: CGS EQ database, 2005; SCEC Website, ) Earthquake magnitudes and locations before 1932 are estimated based on reports of damage and felt effects. Unnamed fault miles north Liquefaction. Liquefaction is the phenomenon in which saturated granular sediments temporarily lose their shear strength during periods of earthquake-induced strong groundshaking. The susceptibility of a site to liquefaction is a function of the depth, density, and water content of the granular sediments and the magnitude and frequency of earthquakes in the surrounding region. Saturated, unconsolidated silts, sands, and silty sands within 50 feet of the ground surface are most susceptible to liquefaction. Liquefaction related phenomena include lateral spreading, ground oscillation, flow failures, loss of bearing strength, subsidence, and buoyancy effects (Youd and Perkins, 1978). In addition, densification of the soil resulting in vertical settlement of the ground can also occur. Although the project site is underlain by unconsolidated alluvial sand and gravel, the liquefaction potential is estimated to be low due to deep groundwater levels. Seismically Induced Landslides. Seismically induced landslides and rockfalls are considered to have a moderate to high potential on the steep hillside south of Smith Creek. However, rockfalls that are initiated on the adjacent slopes would have to continue across Smith Creek wash (250 feet) which is unlikely and would not be a significant impact. Slope Instability. Slope instability covers a series of mass-movement phenomena such as landslides, rockfalls, mudflows, and shallow soil failure. Natural slope instability occurs either as a part of the normal weathering process, or through seismic or major storm events. Contributing factors to instability include topography, June 2008 D.6-6 Draft EIR

7 bedrock and soil types, bedrock orientation, precipitation, vegetation, and human modification of the topography. Man-made slope instability is usually attributable to the alteration of topography during development, and/or through modification of natural slope drainage or percolation. The project site has a very low gradient and slope instability will not occur. The steep slopes on the south side of Smith Creek are underlain by foliated metamorphic bedrock with no slope stability concerns. There is potential for rock falls caused by erosion during intense rain and runoff events, although as discussed above, the Smith Creek wash provides a buffer limiting potential impact at the project site. Soils The project is located in a semi-arid environment with soils sensitive to human activities. However most of the power plant site and storage annex are within areas that are partly disturbed, crossed by dirt roads and transmission lines. Table D.6-3 describes the numerous soil units found within and adjacent to the project. Table D.6-3. Major Soils in the Project Area Soil Name Description Gorgonio Gravelly loamy fine sand, on 0 to 2% slopes Hanford Coarse sandy loam, on 8 to 15% slopes Tujunga Gravelly loamy sand, on 0 to 8% slopes Notes: Source: NRCS Web Soil Survey. Shrink- Swell Potential Erosion Potential Corrosion Potential Concrete Steel Low Low Low Moderate Low Low Low Low Low Low Low Low The Gorgonio gravelly loamy fine sand is the predominant soil type at the project site and storage annex. This soil has a slight erosion potential for off-road travel and will likely experience wind and water erosion during grading. All of the soils at the project site have a high potential to caving in shallow excavations (NRCS, 2007). Corrosivity of soils is generally related to several key parameters: soil resistivity, presence of chlorides and sulfates, oxygen content, and ph. Typically, the most corrosive soils are those with the lowest ph and highest concentration of chlorides and sulfates. High sulfate soils are corrosive to concrete and may prevent complete curing reducing its strength considerably. Low ph and/or low resistivity soils could corrode buried or partially buried metal structures. Mineral Resources Mineral resources in the project area include gravel, sand, and aggregate along San Gorgonio River. These products are the most important mineral resources in California and are actively quarried along the River north of Banning and in Cabazon. In accordance with the requirements of the California Surface Mining and Reclamation Act (SMARA) (Pub. Res. Code 2710 et seq.), the State Geologist has mapped and classified the aggregate resources of the Greater Los Angeles Area, San Bernardino Production-Consumption Region including those along the San Gorgonio River. Because adequate information exists to indicate that significant mineral deposits are present, the California Geological Survey (CGS) has classified the River area as Mineral Resource Zone 2 (MRZ-2) (CGS, 1987). The MRZ-2 area covers river wash deposits from north of Banning to south of Cabazon. The project site is within the MRZ-3 boundary, an area underlain by alluvial deposits containing aggregate materials but the significance of which cannot be fully evaluated based on the lack of subsurface data (CGS, 1987). Draft EIR D.6-7 June 2008

8 A review of California Department of Conservation, Division of Oil, Gas, and Geothermal Resources (DOGGR) online maps indicates that no oil or gas fields are located in the vicinity of the project area. The nearest wildcat exploratory well (dry well, plugged) is located about five miles southwest. There are no geothermal resources in the project area; the nearest thermal spring is more than 10 miles northwest in Highland (DOGGR, 2007). D.6.2 Applicable Regulations, Plans, and Standards Regulatory governance or oversight of geologic hazards and soils are 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, but do not specifically address power plant projects. Local grading ordinances establish detailed procedures for ground disturbing activities including slope inclination, setbacks, drainage, trench backfill, compaction, and testing. D Federal Uniform Building Code Published by the International Conference of Building Officials, the Uniform Building Code (UBC) provides complete regulations covering all major aspects of building design and construction relating to fire and life safety and structural safety. This is the code adopted by most western states. The provisions of the 1997 Uniform Building Code, Volume 1, contain the administrative, fire and life-safety, and field inspection provisions, including all nonstructural provisions and those structural provisions necessary for field inspections. Volume 2 contains provisions for structural engineering design, including those design provisions formerly in the UBC Standards. Volume 3 contains the remaining material, testing and installation standards previously published in the UBC Standards. D State Alquist-Priolo Earthquake Fault Zoning Act of 1972 The Alquist-Priolo Earthquake Fault Zoning Act of 1972 (formerly the Special Studies Zoning Act) regulates the development and construction of buildings intended for human occupancy to avoid the hazard of surface fault rupture. While this act does not specifically regulate power plants, it does help define areas where fault rupture is most likely to occur. 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. Seismic Hazards Mapping Act The Seismic Hazards Mapping Act (the Act) of 1990 (Public Resources Code, Chapter7.8, Division 2) directs the California Department of Conservation (CDC), Division of Mines and Geology (DMG) [now called California Geological Survey (CGS)] 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. Cities, counties, and State agencies are directed to use seismic hazard zone maps developed by CGS in their land-use planning and permitting processes. The Act requires that site-specific geotechnical investigations be performed prior to permitting most urban development projects within seismic hazard zones. June 2008 D.6-8 Draft EIR

9 California Building Code The California Building Code (CBC, 2001) is based on the 1997 Uniform Building Code, with the addition of more extensive structural seismic provisions. Chapter 16 of the CBC contains definitions of seismic sources and the procedure used to calculate seismic forces on structures. As the Proposed Project lies within UBC Seismic Zone 4, provisions for design must follow the requirements of Chapter 16. D Local The Riverside County Plan Chapter 6 Safety Element identifies geologic hazards such as fault rupture, liquefaction, rockfall, landslides and subsidence throughout the county. The plan adopts policies to mitigate and reduce geologic hazards. Policy S 1.1 is intended to mitigate hazard seismic shaking impacts through the adoption and strict enforcement of current building codes. Policy S 2.1 will minimize fault rupture hazards through enforcement of Alquist-Priolo Earthquake Fault Zoning Act provisions to require site-specific fault investigations within Earthquake Fault Study Zone. The Proposed Project is not located in a Alquist-Priolo or Riverside County recommended Fault Study Zone. Policy S 2.4 requires that a State-licensed professional investigate the potential for liquefaction in areas identified as underlain by "Susceptible Sediments" for all proposed critical facilities project. The Proposed Project lies is underlain by susceptible sediments. Although no slope or soil instability hazards are anticipated, Riverside County will likely require grading plans and geotechnical studies for the Proposed Project. The City of Banning General Plan Geotechnical Element includes policies to protect the general health and welfare of the community and reduce potential impacts, such as the loss of life and property damage, associated with seismic and geologic hazards (City of Banning, 2002). Geologic hazards identified in the Geotechnical Element include landslides and slope instability, compressible soils, collapsible soils, expansive soils, ground subsidence, and erosion. Seismically-induced geotechnical hazards in the City of Banning include ground shaking, liquefaction, seismically-induced settlement, seismically-induced rockfalls and landslides, and ridgetop fissures. The Geotechnical Element outlines six policies to address seismic and geotechnical hazards, fault rupture of the ground surface, slope instability, lands subsidence due to groundwater withdrawal, assure functionality of major utility systems after a major earthquake, and soil collapse. D.6.3 Environmental Impacts and Mitigation Measures for the Proposed Project This section explains how impacts are assessed presents the significance criteria on which impact determinations are based. D Criteria for Determining Significance Geologic conditions were evaluated with respect to the impacts the project may have on the local geology, as well as the impact that specific geologic hazards may have upon the power plant facilities. Impacts of the project related to the geologic environment are characterized on the basis of CEQA statutes and guidelines and thresholds of significance developed by local agencies, government codes and ordinances, and requirements stipulated by the California Alquist-Priolo statutes. Impacts would be considered significant and require additional mitigation if: Construction activities would cause slope instability. Draft EIR D.6-9 June 2008

10 Construction activities would accelerate erosion. Project structures would be damaged by corrosive, expansive, soft, loose and/or compressible soils. Project structures would be located on a geologic unit or soil that is or could become unstable and would result in landslides, rockfalls, earthflows, and/or debris flows. Project structures would be damaged by seismically induced groundshaking and ground failure, including liquefaction and lateral spreading. Project structures would be damaged by surface fault rupture at crossings of active and potentially active faults. Project would interfere with access to mineral resources. D Impact Analysis The geology and soils impacts of the Proposed Project are discussed below under subheadings corresponding to each of the significance criteria presented in the preceding section. The analysis describes the impacts of the Proposed Project related to geologic, seismic, and soils hazards and, for each criterion, determines whether implementation of the Proposed Project would result in significant impacts. Impact GEO-1: Construction activities would cause slope instability (No Impact) Destabilization of natural or constructed slopes as a result of grading is not likely due to the very gentle gradients at the project site. No grading for the site or access roads is planned for areas with steep slopes and no steep or high slopes will be constructed. Therefore, proposed grading would not result in slope failures during construction and there is no impact (No Impact). Impact GEO-2: Construction activities would accelerate erosion (Class II). Excavation and grading for the Proposed Project and the biomass storage area, including permanent and temporary access roads, could loosen soil or remove stabilizing vegetation and expose areas of loose soil. These areas, if not properly stabilized during construction, could be subject to increased soil loss and erosion by wind and stormwater runoff. Newly constructed and compacted engineered slopes can also undergo substantial erosion through dispersed sheet flow runoff. More concentrated runoff can result in the formation of small erosional channels and larger gullies, each compromising the integrity of the slope and resulting in significant soil loss. The Proposed Project site is underlain by soils with a low potential for erosion but lies immediately adjacent to Smith Creek which is tributary to San Gorgonio River. The Applicant shall commit to perform construction activities in accordance with the soil erosion/water quality protection measures specified in a Construction Storm Water Pollution Prevention Plan (SWPPP). In accordance with Section 402 of the federal Clean Water Act (CWA) and the State Water Resources Control Board (SWRCB), any construction project which disturbs one acre or more of ground surface must prepare a Construction SWPPP (SWRCB, 2007). The SWPPP would be prepared once the Proposed Project is approved and after the necessary facilities are sited and designed, in order to ensure site-specific conditions are effectively addressed. All SWPPPs must include Best Management Practices (BMPs) for erosion and sediment control, as well as for construction waste handling and disposal. This impact would be significant without mitigation. However, implementation of Mitigation Measure GEO-1 (Minimize Soil Erosion) ensures that potential impacts from erosion related to grading and use of access roads and work areas during construction would be reduced to a less-than-significant (Class II) level. Mitigation Measures for Impact GEO-2 GEO-1 Minimize Soil Erosion. The Construction SWPPP for the Project shall include Best Management Practices (BMPs) designed to minimize soil erosion along access roads and at work areas. June 2008 D.6-10 Draft EIR

11 Appropriate BMPs may include construction of water bars, grading road surfaces to direct flow away from natural slopes, use of soil stabilizers, and consistent maintenance of roads and culverts to maintain appropriate flow paths. Silt fences and straw bales installed during construction shall be removed to restore natural drainage during the cleanup and restoration phase of the project. Where access roads cross streams or drainages, they shall be built at or close to right angles to the streambeds and washes and culverts or rock crossings shall be used to cross streambeds and washes. Design of appropriate BMPs should be conducted by or under the direction of a qualified geologist or engineer. Impact GEO-3: Project structures would be damaged by unsuitable soils (Class II). Soils with low to moderate potential for corrosion exist at the project site (Table D.6-3). Corrosive soils could have a detrimental effect on concrete and metals. Depending on the degree of corrosivity of subsurface soils, concrete and reinforcing steel in concrete structures and bare-metal structures exposed to these soils could deteriorate, eventually leading to structural failures. Expansive, loose or compressible soils are not anticipated at the project site. Prior to final design of the power plant and storage annex foundations, the Applicant will perform geotechnical studies to identify site-specific geologic and soil conditions. This impact would be significant without mitigation. However, implementation of Mitigation Measure GEO-2 (Geotechnical Studies for Corrosive Soils), which adds specific requirements for a geotechnical investigation prior to final Project design, Impact GEO-2 would be reduced to a less-than-significant (Class II) level. Mitigation Measure for Impact GEO-3 GEO-2 Geotechnical Studies for Corrosive Soils. In areas underlain by potentially corrosive soils, the design-level geotechnical studies shall identify the presence, if any, of potentially detrimental soil chemicals, such as chlorides and sulfates, and soil parameters, such as ph and electrical resistivity. Appropriate design measures for protection of reinforcement, concrete, and metal-structural components against corrosion shall be utilized, such as use of corrosion-resistant materials and coatings, increased thickness of Project components exposed to potentially corrosive conditions, and use of passive and/or active cathodic protection systems. Impact GEO-4: Project structures would be damaged by unstable soils, landslides, earthflows, and/or debris flows (No Impact). The Proposed Project site and biomass storage area site are located on gently sloping areas immediately adjacent to Smith Creek which may periodically be subject to flooding. However, slope instability including landslides, earth flows, and debris flows, are not anticipated at the project site or on the bedrock slopes south of Smith Creek. Therefore, the project site is not at risk from landslides, earthflows and debris flows and there is no impact (No Impact). Impact GEO-5: Project structures would be damaged by seismically induced groundshaking and ground failure, including liquefaction and lateral spreading (Class II). Moderate to strong groundshaking would be experienced at the project site in the event of an earthquake on the faults in the project area. The regional map for Riverside County shows the Proposed Project area is located within the0.6 to 0.7 gravity (g) contours. Ground motions may be even greater on alluvial sediments, which underlie the Proposed Project site, and the thrust fault motion on the San Gorgonio Pass fault may result in severe ground shaking. Strong to severe seismically induced groundshaking could cause damage to project Draft EIR D.6-11 June 2008

12 structures. Project features would also be subject to groundshaking from any of the major faults in the region. While the shaking would be less severe from an earthquake that originates farther from the project site, the effects could be damaging to Project structures. Liquefaction occurs in low-lying areas where saturated noncohesive sediments are found. Lateral spreading occurs along waterfronts or canals where non-cohesive soils could move out along a free-face. The soils beneath the Project site have potential for liquefaction. Lateral spreading potential at the gentle, short slopes adjacent to Smith Creek wash is estimated to be low. These impacts would be significant without mitigation. However, with implementation of Mitigation Measure GEO-3a (Protect Against Liquefaction and Lateral Spreading), which adds specific requirements for the geotechnical investigations prior to final Project design, impacts related to liquefaction and lateral spreading would be reduced to a less-than-significant level (Class II). It is likely that the Project facilities would be subjected to at least one moderate or larger earthquake occurring close enough to produce strong to severe groundshaking in the Project area. This impact would be significant without mitigation. To reduce Impact GEO-5 to a less-than-significant level, Mitigation Measure GEO-3b (Reduce Effects of Groundshaking) shall be implemented prior to final Project design to ensure that people or structures are not exposed to hazards associated with strong seismic groundshaking. Mitigation Measure GEO- 3b adds specific requirements to the geotechnical investigations necessary for design to ensure that impacts from Impact GEO-5 are reduced to a less-than-significant level (Class II). Mitigation Measure for Impact GEO 5 GEO-3a Protection Against Liquefaction and Lateral Spreading. Since seismically induced ground failure has the potential to damage or destroy project components, a design-level geotechnical investigation to assess the potential for liquefaction and lateral spreading hazards to affect the approved project and all associated facilities shall be performed. Where these hazards are found to exist, appropriate engineering design and construction measures shall be incorporated into the project designs. Appropriate measures could include construction of pile foundations, ground improvement of liquefiable zones, installation of flexible bus connections, and incorporation of slack in underground cables to allow ground deformations without damage to structures. The Applicant shall submit a report of the required investigations to the City of Banning and County of Riverside building and safety departments for review and approval at least 60 days before construction. GEO-3b Reduce Effects of Groundshaking. The design-level geotechnical investigations performed by the Applicant shall include site-specific seismic analyses to evaluate the peak ground accelerations for design of Project components. The Applicant shall follow the generally accepted standards for design of power plants and may include the Institute of Electrical and Electronics Engineers (IEEE, 2006) 693 Recommended Practices for Seismic Design of Substations which has specific requirements to mitigate the types of damage that equipment at substations have had in the past from such seismic activity. Power plant and substation control buildings shall be designed in accordance with the 2001 California Building Code for sites in Seismic Zone 4 with near-field factors. Impact GEO-6: Project structures would be damaged by surface fault rupture at crossings of active and potentially active faults (No Impact). The Proposed Project site is not crossed by any known active fault traces and is not within a mapped Alquist- Priolo zone. There is no threat of fault rupture at the Proposed Project based on the current understanding of June 2008 D.6-12 Draft EIR

13 active faults in the project area. Therefore, the project site is not at risk from fault rupture and there is no impact to the Project (No Impact). Impact GEO-7: Project would interfere with access to mineral resources (No Impact). The Proposed Project site is within mineral resource zone MRZ-3, an area that contains mineral resources although the significance has not been fully evaluated due to lack of subsurface information. The underlying formations are alluvial deposits a proven valuable resource of sand and gravel. However, the site location may render future mineral extraction difficult or impossible. The project site is located between the City of Banning wastewater treatment plant and Smith Creek. Mineral extraction consisting of a large, deep pit would likely encroach on the treatment plant and future expansion areas. The proximity to the creek would prevent any excavation that would alter the course of the stream or other environmental constraints. Consequently, the project will not result in the loss of availability of mineral resources due to the existing conditions that preclude the effective development of an open-pit quarry at the site and there is no impact by the project (No Impact). D.6.4 Alternative 1 Charles Street Truck Route The Charles Street Truck Route would provide site access along the southern boundary of the project site. Along this Alternative, instead of turning east on Westward Avenue, trucks would continue south on Hathaway Street to Charles Street, where they would turn east and follow Charles Street to the Liberty XXIII Biofuels Power, LLC (Liberty Energy) facility. All other components of construction and operation of the Liberty Energy facility would remain the same as described for the Proposed Project. D Alternative 1 Environmental Setting The Charles Street Truck Route Alternative would have similar truck travel routes as the Proposed Project, and no other components of construction or operation of the Liberty Energy facility would change as compared to the Proposed Project, the environmental setting for geology and soils would be identical to that described above in Section D.6.1 for the Proposed Project. D Alternative 1 - Environmental Impacts and Mitigation Measures Impact GEO-1: Construction activities would cause slope instability (No Impact) Destabilization of natural or constructed slopes as a result of grading is unlikely and the slope instability impacts presented above in Section D for the Proposed Project are identical for Alternative 1. As Alternative 1 would modify the operational related truck routes only and not alter the construction of the proposed facility, the construction-related slope instability impacts for Alternative 1 are identical to the Proposed Project. No grading is planned for areas with steep slopes and no steep or high slopes will be constructed. Therefore, proposed grading would not result in slope failures during construction and there is no impact (No Impact). Impact GEO-2: Construction activities would accelerate erosion (Class II). Construction activities that would accelerate erosion presented above in Section D for the Proposed Project are identical for Alternative 1. As Alternative 1 would modify the operational related truck routes only and not alter the construction of the proposed facility, the construction-related erosion impacts for Alternative 1 are identical to the Proposed Project. Excavation and grading for Alternative 1, including the power plant Draft EIR D.6-13 June 2008

14 facilities, biomass storage area, and permanent and temporary access roads, could loosen soil or remove stabilizing vegetation and expose areas of loose soil. These areas, if not properly stabilized during construction, could be subject to increased soil loss and erosion by wind and stormwater runoff. The Applicant shall commit to perform construction activities in accordance with the soil erosion/water quality protection measures specified in a Construction Storm Water Pollution Prevention Plan (SWPPP). Implementation of Mitigation Measure GEO-1 (Minimize Soil Erosion) ensures that potential impacts from erosion related to grading and use of access roads and work areas during construction would be reduced to a less-than-significant level (Class II)). Impact GEO-3: Project structures would be damaged by unsuitable soils (Class II). The potential for corrosive soils at the site presented above in Section D for the Proposed Project are identical for Alternative 1. As Alternative 1 would modify the operational related truck routes only and not alter the construction or design of the proposed facility, the operational impacts of unsuitable soils for Alternative 1 are identical to the Proposed Project. This impact would be significant without mitigation. However, implementation of Mitigation Measure GEO-2 (Geotechnical Studies for Corrosive Soils), which adds specific requirements for a geotechnical investigation prior to final Project design, Impact GEO-2 would be reduced to a less-than-significant level (Class II)). Impact GEO-4: Project structures would be damaged by unstable soils, landslides, earthflows, and/or debris flows (No Impact). The lack of unstable soils, landslides, earthflows, and/or debris flows at the site as presented above in Section D for the Proposed Project are identical for Alternative 1. Since Alternative 1 would only modify the operational related truck routes and continue to avoid areas of unstable soils and landslides, the operational impacts of unstable soils, landslides, earthflows, and/or debris flows for Alternative 1 are identical to the Proposed Project. Slope instability including landslides, earth flows, and debris flows, are not anticipated along the Alternative 1 truck route and the project site. Therefore, the project is not at risk from landslides, earthflows and debris flows and there is no impact (No Impact). Impact GEO-5: Project structures would be damaged by seismically induced groundshaking and ground failure, including liquefaction and lateral spreading (Class II). The seismic conditions and potential for strong groundshaking and liquefaction as presented above in Section D for the Proposed Project are identical for Alternative 1. Since Alternative 1 would only modify the operational related truck routes, the operational seismic shaking and ground failure impacts for Alternative 1 are identical to the Proposed Project. Moderate to strong groundshaking would be experienced at the project site in the event of an earthquake on the faults in the project area. These impacts would be significant without mitigation. However, with implementation of Mitigation Measure GEO-3a (Protect Against Liquefaction and Lateral Spreading) and Mitigation Measure GEO-3b (Reduce Effects of Groundshaking), which add specific requirements for the geotechnical investigations prior to final Project design, impacts related to liquefaction, lateral spreading, and strong groundshaking would be reduced to a less-than-significant level (Class II). Impact GEO-6: Project structures would be damaged by surface fault rupture at crossings of active and potentially active faults (No Impact). The fault rupture hazard presented above in Section D for the Proposed Project is identical for Alternative 1. Since Alternative 1 would only modify the operational related truck routes, the surface fault June 2008 D.6-14 Draft EIR

15 rupture impacts for Alternative 1 are identical to the Proposed Project. Alternative 1 is not crossed by any known active fault traces and is not within a mapped Alquist-Priolo zone and there is no threat of fault rupture based on the current understanding of active faults in the project area. Therefore, Alternative 1 is not at risk from fault rupture and there is no impact to the Project (No Impact). Impact GEO-7: Project would interfere with access to mineral resources (No Impact). The mineral resource potential presented above in Section D for the Proposed Project is identical for Alternative 1. Since Alternative 1 would only modify the operational related truck routes along existing paved streets, the interference with access to mineral resources impacts for Alternative 1 are identical to the Proposed Project. Due to the existing conditions that preclude the effective development of an open-pit quarry at the site, there is no impact by Alternative 1 to future access of mineral resources (No Impact). D.6.5 Alternative 2 Avoid Peak Hours Traffic Under this alternative, operational truck traffic would be restricted to occur only outside of peak traffic hours. Construction of the Alternative 2 would be the same as described for the Proposed Project. With the exception of the times that operational truck traffic would be restricted, operation and maintenance of Alternative 2 would be the same as the Proposed Project. D Alternative 2 Environmental Setting As the Avoid Peak Hours Traffic Alternative would have identical truck travel routes as the Proposed Project, and no other components of construction or operation of the Liberty Energy facility would change as compared to the Proposed Project, the environmental settings for geology and soils would be identical to that described above in Section D.10.1 for the Proposed Project. D Alternative 2 - Environmental Impacts and Mitigation Measures Impact GEO-1: Construction activities would cause slope instability (No Impact) Destabilization of natural or constructed slopes as a result of grading is unlikely and the slope instability impacts presented above in Section D for the Proposed Project are identical for Alternative 2. As Alternative 2 would only restrict the operational related trucking periods and not alter the routes or construction of the proposed facility, the construction-related slope instability impacts for Alternative 2 are identical to the Proposed Project. No grading is planned for areas with steep slopes and no steep or high slopes will be constructed. Therefore, proposed grading would not result in slope failures during construction and there is no impact (No Impact). Impact GEO-2: Construction activities would accelerate erosion (Class II). Construction activities that would accelerate erosion presented above in Section D for the Proposed Project are identical for Alternative 2. As Alternative 2 would only restrict the time periods that delivery and ash removal trucks would operate and not alter the construction of the proposed facility, the constructionrelated erosion impacts for Alternative 2 are identical to the Proposed Project. Excavation and grading for Alternative 2 could loosen soil or remove stabilizing vegetation and expose areas of loose soil. These areas, if not properly stabilized during construction, could be subject to increased soil loss and erosion by wind and stormwater runoff. The Applicant shall commit to perform construction activities in accordance with the soil Draft EIR D.6-15 June 2008

16 erosion/water quality protection measures specified in a Construction Storm Water Pollution Prevention Plan (SWPPP). Implementation of Mitigation Measure GEO-1 (Minimize Soil Erosion) ensures that potential impacts from erosion related to grading and use of access roads and work areas during construction would be reduced to a less-than-significant (Class II) level. Impact GEO-3: Project structures would be damaged by unsuitable soils (Class II). The potential for corrosive soils at the site presented above in Section D for the Proposed Project are identical for Alternative 2. As Alternative 2 would only restrict the operational trucking activities and not alter the construction or design of the proposed facility, the operational impacts of unsuitable soils for Alternative 2 are identical to the Proposed Project. This impact would be significant without mitigation. However, implementation of Mitigation Measure GEO-2 (Geotechnical Studies for Corrosive Soils), which adds specific requirements for a geotechnical investigation prior to final Project design, Impact GEO-2 would be reduced to a less-than-significant level (Class II)). Impact GEO-4: Project structures would be damaged by unstable soils, landslides, earthflows, and/or debris flows (No Impact). The lack of unstable soils, landslides, earthflows, and/or debris flows at the site as presented above in Section D for the Proposed Project are identical for Alternative 2. Since Alternative 2 would only restrict trucking activities during operation, the operational impacts of unstable soils, landslides, earthflows, and/or debris flows for Alternative 2 are identical to the Proposed Project. Slope instability including landslides, earth flows, and debris flows, are not anticipated for Alternative 2. Therefore, the project is not at risk from landslides, earthflows and debris flows and there is no impact (No Impact). Impact GEO-5: Project structures would be damaged by seismically induced groundshaking and ground failure, including liquefaction and lateral spreading (Class II). The seismic conditions and potential for strong groundshaking and liquefaction as presented above in Section D for the Proposed Project are identical for Alternative 2. Since Alternative 2 would only restrict the operational period for delivery and ash disposal trucks, the operational seismic shaking and ground failure impacts for Alternative 2 are identical to the Proposed Project. Moderate to strong groundshaking would be experienced at the project site in the event of an earthquake on the faults in the project area. These impacts would be significant without mitigation. However, with implementation of Mitigation Measure GEO-3a (Protect Against Liquefaction and Lateral Spreading) and Mitigation Measure GEO-3b (Reduce Effects of Groundshaking), which add specific requirements for the geotechnical investigations prior to final Project design, impacts related to liquefaction, lateral spreading, and strong groundshaking would be reduced to a lessthan-significant level (Class II). Impact GEO-6: Project structures would be damaged by surface fault rupture at crossings of active and potentially active faults (No Impact). The fault rupture hazard presented above in Section D for the Proposed Project is identical for Alternative 2. Since Alternative 2 would only modify the time period for trucking, the surface fault rupture impacts for Alternative 2 are identical to the Proposed Project. Alternative 2 is not crossed by any known active fault traces and is not within a mapped Alquist-Priolo zone and there is no threat of fault rupture based on the current understanding of active faults in the project area. Therefore, Alternative 2 is not at risk from fault rupture and there is no impact to the Project (No Impact). June 2008 D.6-16 Draft EIR