3.7 GEOLOGY, SOILS, MINERALS, AND PALEONTOLOGICAL RESOURCES

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1 3.7 GEOLOGY, SOILS, MINERALS, AND PALEONTOLOGICAL RESOURCES This section contains an analysis of impacts related to geology, soils, mineral resources, and paleontological resources. The analysis describes seismic hazards, soil conditions, and other geotechnical considerations that could affect people and structures that could be within the SOIA Area, including the multi-sport park complex, in the future. The proposed Project is evaluated relative to its potential to affect regionally significant mineral deposits or paleontologically sensitive geologic formations ENVIRONMENTAL SETTING REGIONAL GEOLOGY The SOIA Area is located in the San Joaquin Valley of the Northern Section of the Great Valley Geomorphic Province (GVGM). The relatively flat valley is bounded by Cascade Range to the North, Coast Ranges to the West, the Sierra Nevada to the East, and Coast Ranges and the Tehachapi Mountains to the South (Page 1986). The GVGM is approximately 400 miles long and 50 miles wide. The San Joaquin Valley is predominately made up of sedimentary units from the Cretaceous to the Quaternary Periods. Minority units include metamorphic rocks from the Jurassic Period and volcanic rocks from the Neogene Period. The geomorphic subunits of the GVGM include the delta, river floodplain, alluvial plain and low foothills. The SOIA Area is located on the river floodplain which contains unconsolidated, inorganic soils. Floodplain sediment is deposited when a river or a stream overflows its natural levees. REGIONAL SEISMICITY Seismicity is the likelihood of an area to be subjected to earthquake activity. Seismic activity has consequential geologic hazards such as: ground shaking, liquefaction, lateral spreading, landslides, avalanches, and ground displacement. These geologic hazards create structural hazards of infrastructure. FAULTING A fault is fracture or a fracture zone where there has been measurable displacement between each side of the fracture. Faults form in rocks when regional stresses overcome the strength of the rock to create fracture with measureable slip. Faults are rarely isolated geological features. A group of faults that develop from the same region in the same time interval are referred to as a Fault System. Fault systems are associated with relative movement of the earth s crust due to tectonic activity. Based on historic seismic activity, faults are categorized as active, potentially active, or inactive. According to the Alquist-Priolo Act, an active fault is one that has ruptured in the last 11,000 years. There are no faults in the SOIA Area or in the vicinity of the SOIA Area that are considered active, potentially active, or inactive by the Alquist-Priolo definition. Sacramento LAFCo and City of Elk Grove Geology, Soils, Minerals, and Paleontological Resources

2 SEISMIC HAZARDS Fault Rupture Fault rupture is the displacement of the ground surface along the fault. There are two types of fault rupture: seismic and aseismic. Seismic faults have a stick-slip behavior. Stress builds up along the fault (the stick phase) until the fault can no longer accommodate the stress and displaces (the slip phase). The slip phase is the cause of an earthquake. Aseismic faults experience offset at such a slow rate that an earthquake is not generated. This is also referred to as fault creep. Ground Shaking The Sacramento Valley has experienced only low levels of seismic shaking. The nearest known active (Holocene or Historic) fault traces are located near the Dunnigan Hills and the Vaca Mountains, approximately 40 miles northwest and southwest, respectively (Jennings 1994). Numerous earthquakes of magnitude (M) 5.0 or greater have occurred on regionally active faults in the Coast Ranges, approximately 30 to 40 miles west of Elk Grove. Table identifies the regionally active faults, their approximate distances from the SOIA Area, and the projected maximum earthquake magnitude and slip rate of each fault. Table Active Regional Faults Fault Name Approximate Distance from Project Area (miles) Regional Location Great Valley Fault Zone, Segment 4 32 Margin between Sacramento Valley and Coast Ranges Great Valley Fault Zone, Segment 5 35 Margin between Sacramento Valley and Coast Ranges Dunnigan Hills Fault 40 Margin between Sacramento Valley and Coast Ranges Great Valley Fault Zone, Segment 3 40 Margin between Sacramento Valley and Coast Ranges Projected Maximum Moment Magnitude Slip Rate (mm/yr) N/A Green Valley Concord Fault Zone 43 Coast Ranges Greenville Fault Zone (includes Clayton and Marsh Creek sections) 43 Coast Ranges Mount Diablo Blind Thrust Fault 25 Coast Ranges West Napa Fault 51 Coast Ranges Hayward Rodgers Creek Fault Zone 60 Coast Ranges Notes: mm/yr = millimeters per year; N/A = not available Sources: Jennings 1994; Working Group on Northern California Earthquake Potential 1996; Working Group on California Earthquake Probabilities 2008 The intensity of ground shaking depends on the distance to the earthquake epicenter, the earthquake magnitude, soil conditions, and the seismic characteristics of the fault. Ground motions can be estimated by probabilistic methods or design calculations and used for earthquake-resistant building design. Although the site-specific seismic characteristics of the SOIA Area have not been calculated by a geotechnical engineer (as required by the California Building Standards Code [CBC]), the potential for seismic ground shaking can be estimated using the California Geological Survey (CGS) Probabilistic Seismic Hazards Assessment Model (CGS 2008). This model Geology, Soils, Minerals, and Paleontological Resources Sacramento LAFCo and City of Elk Grove

3 indicates that a minimum horizontal acceleration of 0.189g for alluvial conditions (where g is the percentage of gravity) could occur at the site with a 10 percent probability of earthquake occurrence in a 50-year time frame (CGS 2008). In other words, there is a 1-in-10 probability that an earthquake will occur within 50 years that would result in a peak horizontal ground acceleration exceeding 0.189g. This indicates a relatively low level of seismic shaking. Liquefaction Soil liquefaction occurs when ground shaking causes a sediment layer saturated with groundwater to lose strength and become fluid. Factors determining liquefaction potential are the type and consistency of soils, the level and duration of seismic ground motions, and the depth to groundwater. Loose sands and peat deposits, uncompacted fill and other Holocene materials deposited by sedimentation in rivers and lakes (fluvial or alluvial deposits), and debris or eroded material (colluvial deposits) are more susceptible to liquefaction. Areas most susceptible to liquefaction-induced damage are underlain by loose, water-saturated, granular sediment within 40 feet of the ground surface. Liquefaction poses a hazard to buildings, bridges, and underground utility pipelines. Loss of soil strength can render bearing capacity (the ability of soil to support the loads applied to the ground) insufficient to support foundation loads, increase lateral pressure on retaining walls, and cause slope instability. The SOIA Area is not located in a seismically active area, and is composed of relatively stable, Pleistocene-age sediments of the Riverbank Formation. The depth to groundwater is approximately 40 to 60 feet below the ground surface (Blackburn Consulting 2014:3). Subsidence, Settlement, and Soil Bearing Capacity Both natural and human phenomena can induce land subsidence. Natural phenomena include tectonic deformations and seismically induced settlements; consolidation, hydrocompaction, or rapid sedimentation; oxidation or dewatering of organic-rich soils; and collapse of subsurface cavities. Subsidence related to human activity can result from groundwater and oil or gas extraction. Groundwater pumping has caused subsidence in various areas of the Central Valley. Seismically induced settlement refers to the compaction of soils and alluvium caused by ground shaking. Finegrained soils are subject to seismic settlement and differential settlement. Areas underlain by low-density silts and clays associated with fluvial deposits are susceptible, including old lakes, sloughs, swamps, and streambeds. The amount of settlement may range from a few inches to several feet. The potential for differential settlement is highest and occurs over the largest areas during high-magnitude earthquakes and can occur in low-density and unconsolidated material such as overbank river deposits (present-day and historical) common along river beds and streambeds. Lateral spreading is the horizontal movement or spreading of soil toward an open face, such as a streambank, the open side of fill embankments, or the sides of levees. The potential for land failure from subsidence and lateral spreading is highest in areas with a high groundwater table, in relatively soft and recent alluvial deposits, and where creek banks are relatively high. Where the soil bearing capacity is too low to support proposed structures, subsidence and settlement may occur. Based on a review of soil survey data from the United States Natural Sacramento LAFCo and City of Elk Grove Geology, Soils, Minerals, and Paleontological Resources

4 Resources Conservation Service (NRCS) (2015a), several of the soils in the SOIA Area have low bearing strength. Seismic Seiches Earthquakes may affect open bodies of water by creating seismic sea waves (often called tidal waves ) and seiches. Seismic sea waves are caused by abrupt ground movements (usually vertical) on the ocean floor in connection with a major earthquake. Because the SOIA Area is far from the Pacific Ocean, seismic sea waves would not represent a hazard. A seiche is a sloshing of water in an enclosed or restricted water body, such as a basin, river, or lake, caused by earthquake motion; the sloshing can occur for a few minutes or several hours. The SOIA Area is not located in a seismically active area, is not near an enclosed water body, and is located approximately 0.25 mile from Deer Creek and approximately 0.75 mile from the Cosumnes River. SLOPE STABILITY A landslide is the downhill movement of masses of earth material under the force of gravity. The factors contributing to landslide potential are steep slopes, unstable terrain, and proximity to earthquake faults. Landslides typically involve the surface soil and an upper portion of the underlying bedrock. Movement may be very rapid or may occur over a period of weeks or years. (This slow change is known as creep. ) The size of a landslide can range from several square feet to several square miles. The SOIA Area is nearly level; elevations range from approximately 45 to 50 feet above mean sea level. There are no adjacent areas with steep terrain. SOILS Exhibit shows the locations of the various soil types in the SOIA Area and Table summarizes the relevant surface soils based on NRCS soil surveys (NRCS 2015a). The majority of the SOIA Area, including the multi-sport park complex area, consists of soils within the San Joaquin soil series. Expansive soils are composed largely of clays, which greatly increase in volume when saturated with water and shrink when dried. Because of this effect, structural foundations may rise during the rainy season and fall during the dry season, potentially resulting in cracking and distortion of portions of the structure. Retaining walls and underground utilities may be damaged for the same reasons. Based on the information shown in Table 3.7-2, the Durixeralfs, Galt, and Kimball soil series within the SOIA Area have been rated with a moderate to high shrinkswell potential. MINERALS Under the California Surface Mining and Reclamation Act of 1975 (SMARA), the State Mining and Geology Board may designate certain mineral deposits (e.g., sand, gravel) as regionally significant for satisfying future needs. The board s designations are based on classification reports prepared by CGS and input from agencies and the public. The Project area lies within the designated Sacramento-Fairfield Production-Consumption Region for Portland cement concrete aggregate, which includes all designated lands within the marketing area of the active aggregate operations supplying the Sacramento-Fairfield urban center. However, as noted below, inclusion of the SOIA Area within this regional designation does not mean that the SOIA Area, itself, contains significant aggregate resources in commercially extractable quantities. Geology, Soils, Minerals, and Paleontological Resources Sacramento LAFCo and City of Elk Grove

5 Source: NRCS 2015b Exhibit SOIA Area Soil Types Sacramento LAFCo and City of Elk Grove Geology, Soils, Minerals, and Paleontological Resources

6 Elk Grove SOI Amendment and Multi-Sport Park Complex Geology, Soils, Minerals, and Paleontological Resources Sacramento LAFCo and City of Elk Grove Table Soil Map Unit Name Durixeralfs, 0 to 1% slopes Soil Characteristics Galt clay leveled, 0 to 1% slopes Kimball silt loam, 0 to 2% slopes San Joaquin silt loam, leveled, 0 to 1% slopes San Joaquin silt loam, 0 to 3% slopes San Joaquin Durixeralfs complex, 0 to 1% slopes San Joaquin Galt complex, leveled, 0 to 1% slopes San Joaquin Galt complex, 0 to 3% slopes San Joaquin Xerarents complex, leveled, 0 to 1% slopes Shrink-Swell Potential 1 High High Permeability 2 Moderately low Moderately low Water Erosion Hazard 3 Wind Erosion Hazard 4 Drainage Hydrologic Soil Group 5 Moderate 4 Well drained D Low 4 Moderately well drained D Moderate Moderate Moderate 6 Well drained D Low Moderate Moderate 6 Moderately well drained C Not limited Low Moderate Moderate 6 Moderately well drained C Not limited Low Moderate Moderate 6 Moderately well drained C Not limited Limitations for Buildings and Roads High shrink-swell potential, low bearing strength High shrink-swell potential, low bearing strength Low bearing strength, moderate shrink-swell potential Low Moderate High 6 Moderately well drained D Low bearing strength Low Moderate Moderate 6 Moderately well drained C Not limited Low Moderate NR NR Moderately well drained NR NR Notes: NR = not rated 1 Based on percentage of linear extensibility. Shrink-swell potential ratings of moderate to very high can result in damage to buildings, roads, and other structures. 2 Based on standard United States Natural Resources Conservation Service (NRCS) saturated hydraulic conductivity (Ksat) class limits; Ksat refers to the ease with which pores in a saturated soil transmit water. Based on the NRCS erosion factor Kw whole soil, which is a measurement of relative soil susceptibility to sheet and rill erosion by water. Based on the NRCS wind erodibility groups. The soils assigned to Group 1 are the most susceptible to wind erosion, and those assigned to Group 8 are the least susceptible. Hydrologic soil groups are based on estimated runoff potential: Group C = slow infiltration rate and moderate to high runoff potential, Group D = very slow infiltration rate and very high runoff potential. Source: NRCS 2015a

7 In compliance with SMARA, CGS has established the mineral resource zone (MRZ) classification system shown in Table to denote both the location and the significance of key extractive resources. In general, active construction aggregate (i.e., sand and gravel) production areas in Sacramento County are currently located primarily along ancestral channels of the American River in northwestern Sacramento County and the city of Rancho Cordova, which have been classified by CGS as MRZ-2 (Dupras 1999:Plate 3). The Hanford Sand & Gravel, Inc., aggregate mining operation is located adjacent to Wilton Road between Deer Creek and the Cosumnes River, approximately 3.8 miles northeast of the SOIA Area (Larosse et al. 1999). This mining operation is also in an area classified by CGS as MRZ-3 (Dupras 1999:Plate 3). The SOIA Area is classified as MRZ-3 areas containing mineral deposits, the significance of which cannot be evaluated from existing data (Dupras 1999:Plate 3). Table Classification MRZ-1 MRZ-1 MRZ-2 MRZ-3 MRZ-4 California Geological Survey Mineral Land Classification System Description Areas where adequate information indicates that no significant mineral deposits are present or where it is judged that little likelihood exists for their presence Areas of mined-out PCC-grade aggregate resources Areas where adequate information indicates that significant mineral deposits are present or where it is judged that a high likelihood exists for their presence Areas containing mineral deposits, the significance of which cannot be evaluated from available data Areas where available data is inadequate for assignment to any other mineral resource zone Notes: MRZ = Mineral Resource Zone; PCC = Portland Cement Concrete Source: Dupras 1999:Plate 3 PALEONTOLOGICAL RESOURCES The potential paleontological importance of the SOIA Area was assessed by identifying the rock units exposed there. Topographic maps that delineate the distribution of the rock units present were used to identify areas of higher and lower paleontological sensitivity. Sensitive formations are rated high for potential paleontological productivity and are known to have produced unique, scientifically important fossils. Paleontological productivity refers to the abundance and density of fossil specimens, previously recorded fossil sites, or both. Therefore, paleontological sensitivity is based primarily on the types and numbers of fossils that have been previously recorded from that rock unit (i.e., the paleontological productivity). The geologic formations in the SOIA Area, including the multi-sport park complex project site, were assigned a paleontological sensitivity consistent with Society of Vertebrate Paleontology (SVP) 1995 guidelines. Geologic maps and available published geological and paleontological literature describing bedrock and surficial geology were reviewed to identify the exposed and subsurface rock units, assess their potential paleontological productivity, and delineate their respective areal distribution. Regional and local surficial geologic mapping and correlation of the various geologic units exists at scales of 1:24,000 (Atwater and Marchand 1980) and 1:250,000 (Wagner et al. 1987). The literature review was supplemented by searching the records of the University of California, Berkeley Museum of Paleontology (UCMP) on December 7, The Pleistocene epoch, known as the great ice age, began approximately 2.6 million years ago. Based on the vertebrate fauna from the nonmarine late Cenozoic deposits of the San Francisco Bay region, two major divisions of Pleistocene-age fossils are widely recognized: the Irvingtonian (older Pleistocene fauna) and the Sacramento LAFCo and City of Elk Grove Geology, Soils, Minerals, and Paleontological Resources

8 Rancholabrean (younger Pleistocene fauna) (Savage 1951). The age of the later Pleistocene, Rancholabrean fauna was based on the presence of bison and of many mammalian species that inhabit the same area today. Other large Rancholabrean fauna include mammoths, mastodons, camels, horses, and ground sloths. The Irvingtonian fauna are scarcer, and are represented by Borophagus (bone-crushing dogs), hyenas, saber-toothed cats, rabbits, giant marmots, horses, mammoths, and mastodons. The SOIA Area is within the Riverbank Formation. Fossils referable to the Riverbank Formation have been found at six sites near Sacramento, including the Teichert gravel mine on State Route 16 in southeastern Sacramento County (Jefferson 1991a, 1991b). This site yielded specimens of broad-footed mole, Harlan s ground sloth, rabbit, California ground squirrel, Botta s pocket gopher, pocket mouse, groove-toothed harvest mouse, woodrat, vole, coyote, dire wolf, mammoth, horse, western camel, deer, antique bison, fish (carps and minnows), frog, snake, Pacific pond turtle, and the family Anatidae (ducks, geese, and swans). There are at least nine recorded Rancholabrean-age vertebrate fossil sites from the Riverbank Formation in Sacramento County. Most recently, Pleistocene-age mammoth remains, including a tusk, ribs, teeth, and portions of a shoulder blade, were discovered on July 2, 2004, during excavation of a Sacramento Municipal Utility District trench in Elk Grove (Kolber 2004). UCMP locality V-74086, located in southern Sacramento at Ehrhardt Avenue, also contained fossilized Rancholabrean-age mammoth remains. The other UCMP sites in Sacramento localities V-6747, V-6846, V-68141, V-69129, and V contained remains of Rancholabrean-age bison, camel, coyote, horse, Harlan s ground sloth, mammoth, woodrat, fish, mole, snake, and gopher. Pleistocene-age fossils were recovered from the Riverbank Formation at the ARCO Arena site (Hilton et al. 2000); those fossils included remains of Harlan s ground sloth, bison, coyote, horse, camel, squirrel, antelope or deer, and mammoth. Finally, San Diego Society of Natural History locality 0663 (Jefferson 1991a, 1991b) included fossil specimens of Rancholabrean-age horse and camel recovered from sediments in Sacramento County. Several localities near the cities of Davis and Woodland have yielded the remains of Rancholabrean-age rodents, snakes, horses, antelope, Harlan s ground sloth, mammoth, and saber-toothed cat from Riverbank Formation sediments (Hay 1927; UCMP 2015). Three sites in Sutter County have yielded Rancholabrean vertebrate fossils recovered from Pleistocene-age sediments (UCMP 2015). UCMP locality V-4043 in the Sutter Buttes yielded remains from a Pleistocene-age horse. Fossil specimens from the Riverbank Formation have been reported near the city of Riverbank (Marchand and Allwardt 1981), and at numerous other locations throughout the Central Valley, including Lathrop, Modesto, Stockton, Tracy (along the Delta-Mendota Canal), Manteca, and Merced (UCMP 2015). The literature and records search indicate that no fossil remains have been recovered within the SOIA Area. However, the occurrence of Pleistocene vertebrate fossil remains in sediments referable to the Riverbank Formation in Sacramento and throughout the Central Valley indicates that this rock formation is paleontologically sensitive. Geology, Soils, Minerals, and Paleontological Resources Sacramento LAFCo and City of Elk Grove

9 3.7.2 REGULATORY FRAMEWORK FEDERAL PLANS, POLICIES, REGULATIONS, AND LAWS Soil and Water Resources Conservation Act of 1977 The Soil and Water Resources Conservation Act of 1977, as amended (RCA) provides the United States Department of Agriculture (USDA) broad strategic assessment and planning authority for the conservation, protection, and enhancement of soil, water, and related natural resources. Through RCA, USDA: appraises the status and trends of soil, water, and related resources on non-federal land and assesses their capability to meet present and future demands; evaluates current and needed programs, policies, and authorities; and develops a national soil and water conservation program to give direction to USDA soil and water conservation activities. Federal Earthquake Hazards Reduction Act This act was passed in 1977 by U.S. Congress to reduce the risks of life and property from future earthquakes through the establishment and maintenance if an effective hazards and reduction program. The National Earthquake Hazards Reduction Program (NEHRP) was established to improve understanding, characterization, and predictions of earthquake hazards and vulnerabilities; improved building codes and land use practices; risk reduction through post-earthquake investigations and education; development and improvement of design and construction techniques; improved mitigation capacity; and accelerated application of research results. The NEHRP designates the Federal Emergency Management Agency (FEMA) as the lead agency of the program and assigns it several planning, coordinating, and reporting responsibilities. Other NEHRP agencies include the National Institute of Standards and Technology, the National Science Foundation, and the U.S. Geological Survey (USGS). Uniform Building Code The Uniform Building Code (UBC) provides site development and construction standards. The UBC is widely used throughout the United States and is generally adopted on a district-by-district or state-by-state basis. The UBC has been modified for California conditions with more detailed and more stringent regulations (see below for discussion of California building code standards). Clean Water Act The Clean Water Act (CWA) regulates discharges into waters of the United States, including a range of potential point and nonpoint sources of water-transported pollutants, and the discharge of fill into waters, such as wetlands and intermittent stream channels. The purpose of the CWA is to restore and maintain the chemical, physical, and biological integrity of the nation s waters through prevention and elimination of pollution. However, compliance with CWA requirements also has co-benefits related to reduction of soil erosion that are relevant for this section of the EIR. Implementation of the CWA has state and regional elements and, although this is the federal Sacramento LAFCo and City of Elk Grove Geology, Soils, Minerals, and Paleontological Resources

10 regulatory subsection, relevant State and regional responsibilities are highlighted here, with further detail below under the State regulatory framework subsection below. The law requires that a CWA Section 404 permit be obtained from the United States Army Corps of Engineers (USACE) for any dredged or fill materials discharged into wetlands or waters of the United States whether the discharge is temporary or permanent. A National Pollutant Discharge Elimination System permit is required through the appropriate regional water quality control board (RWQCB). Clean Water Act (CWA) Section 402 mandates that certain types of construction activity comply with the requirements of Environmental Protection Agency s National Pollution Discharge Elimination System (NPDES) stormwater program. Construction activities that disturb one or more acres of land must obtain coverage under the NPDES general construction activity stormwater permit, which is issued by the RWQCB. Obtaining coverage under the NPDES general construction activity stormwater permit generally requires that the project applicant complete the following steps: File a Notice of Intent with RWQCB that describes the proposed construction activity before construction begins; Prepare a Storm Water Pollution Prevention Plan (SWPPP) that describes Best Management Practices (BMPs) that would be implemented to control accelerated erosion, sedimentation, and other pollutants during and after project construction; and File a notice of termination with RWQCB when construction is complete and the construction area has been permanently stabilized. The SWRCB adopted Order DWQ for a new statewide NPDES Construction General Permit # CA on September 2, 2009 that took effect on July 1, 2010 (SWRCB 2009, 2013). This General Permit imposes more minimum BMPs and establishes three levels of risk-based requirements based on both sediment risk and receiving water risk. All dischargers are subject to narrative effluent limitations. Risk level 2 dischargers are subject to technology-based numeric action levels (NALs) for ph and turbidity. Risk level 3 dischargers are subject to NALs and numeric effluent limitations (NELs). Certain sites must develop and implement a SWPPP and Rain Event Action Plan (REAP) and all projects must perform effluent monitoring and reporting, along with receiving water monitoring and reporting. The General Permit requires that key personnel (e.g., SWPPP preparers, inspectors, etc.) have specific training or certifications to ensure their level of knowledge and skills are adequate to ensure their ability to design and evaluate project specifications that will comply with General Permit requirements. For projects commencing on or after July 1, 2010, the applicant must electronically submit Permit Registration Documents (PRDs) prior to commencement of construction activities including the Notice of Intent, Risk Assessment, Post-Construction Calculations, a Site Map, the SWPPP, a signed certification statement by the Legally Responsible Person (LRP), and the first annual fee. STATE PLANS, POLICIES, REGULATIONS, AND LAWS California Building Code The California Building Standards Code (CBC) establishes minimum building requirements for renovation and construction. The CBC contains provisions intended to regulate grading activities, drainage and erosion control, Geology, Soils, Minerals, and Paleontological Resources Sacramento LAFCo and City of Elk Grove

11 and construction on unstable soil (expansive soils or areas subject to liquefaction). When no other building codes apply, Chapter 29 regulates excavations, foundations, and retaining walls. Chapter 18 of the Building Code contains provisions related to Soils and Foundations, including geotechnical investigations (Section 1803); excavation, grading and fill (Section 1804); assessing soil load-bearing capacity (Section 1806); and foundation design (Sections ). The Residential Code contains provisions regarding soil testing, geotechnical evaluations for building foundations, and excavations for compressible or shifting soils (Section R401), foundations on expansive soils (Section R403), and seismic provisions (Section R301) (CBSC 2018). In addition, the Green Building Standards Code (CALGreen) contains provisions for construction of nonresidential buildings regarding soil erosion and stormwater runoff, and grading activities (Section 5.106). It also contains measures related to soil analysis and protection requirements, and topsoil protection as part of the residential mandatory measures (Chapter 4) (CBSC 2018). Updates to the California Building Standards Code were published in July of These updates, including updates to the CALGreen code, took effect beginning January 1, California Seismic Hazards Mapping Act The California Seismic Hazards Mapping Act (California Public Resources Code Section ) addresses seismic hazards other than surface rupture, such as liquefaction and induced landslides. The Seismic Hazards Mapping Act specifies that the lead agency for a project may withhold development permits until geologic or soils investigations are conducted for specific sites and mitigation measures are incorporated into plans to reduce hazards associated with seismicity and unstable soils. Alquist-Priolo Earthquake Fault Zoning Act The Alquist-Priolo Earthquake Fault Zoning Act of 1972 requires the State Geologist to delineate Earthquake Fault Zones along known active faults that have a relatively high potential for ground rupture. Faults must meet the definition of sufficiently active and well-defined to be included as an Earthquake Fault Zone. These zones extended 200 to 500 feet on either side of the fault. An area of 50 feet on either side of an active fault trace is assumed to underlain by the fault, unless proven otherwise. No structures for human occupancy may be built across an identified active fault trace. Proposed construction in an Earthquake Fault Zone is permitted only following the completion of a fault location report prepared by a California Registered Geologist. National Pollutant Discharge Elimination System Permit In California, the State Water Resources Control Board (SWRCB) administers the United States Environmental Protection Agency s promulgated regulations (55 Code of Federal Regulations 47990) requiring the permitting of stormwater-generated pollution under the National Pollutant Discharge Elimination System (NPDES). In turn, the SWRCB s jurisdiction is administered through Regional Water Quality Control Boards. Pursuant to these federal regulations, an operator must obtain a General Permit under the NPDES Stormwater Program for all construction activities with ground disturbance of 1 acre or greater. The General Permit requires the implementation of best management practices (BMPs) to reduce pollutant loads into the waters of the State and measures to reduce sediment and erosion control. In addition, a Stormwater Pollution Protection Plan (SWPPP) must be prepared. The SWPPP addresses water pollution control during construction. SWPPPs require that all stormwater discharges associated with construction activity, where clearing, grading, and excavating results in soil Sacramento LAFCo and City of Elk Grove Geology, Soils, Minerals, and Paleontological Resources

12 disturbances, must by law be free of site pollutants. Water Quality Order DWQ requires permittees to implement specific sampling and analytical procedures to determine whether BMPs implemented on a construction site are (1) preventing further impairment by sediment in stormwater discharged directly into waters listed as impaired for sediment or silt, and (2) preventing other pollutants, that are known or should be known by permittees to occur on construction sites and that are not visually detectable in stormwater discharges, from causing or contributing to exceedances of water quality objectives. Further, the order contains information regarding the type of construction covered and not covered by the general permit, notification requirements, and a description of general permit conditions. REGIONAL AND LOCAL PLANS, POLICIES, REGULATIONS, AND ORDINANCES City of Elk Grove The City of Elk Grove General Plan establishes policies to guide long-term development and conservation within the City s planning area. The City s General Plan policies and actions related to geology, soils, seismicity, and paleontological resources are provided below. Policy SA-25: The City supports efforts by Federal, State, and other local jurisdictions to investigate local seismic and geological hazards and support those programs that effectively mitigate these hazards. SA-25-Action 1: Implement the Uniform Building Code to ensure that structures meet all applicable seismic standards. Policy SA-26: The City shall seek to ensure that new structures are protected from damage caused by geologic and/or soil conditions. SA-26 Action 1: Require that a geotechnical report or other appropriate analysis be conducted to determine the shrink/swell potential and stability of the soil for public and private construction projects and identifies measures necessary to ensure stable soil conditions. HR-6-Action 1: In areas identified in the Background Report as having a significant potential for containing archaeological or paleontological artifacts, require completion of a detailed on-site study as part of the environmental review process. Implement all recommended mitigation measures. HR-6-Action 2: Impose the following conditions on all discretionary projects in areas which do not have a significant potential for containing archaeological or paleontological resources: The Planning Division shall be notified immediately if any prehistoric, archaeologic, or paleontologic artifact is uncovered during construction. All construction must stop and an archaeologist that meets the Secretary of the Interior s Professional Qualifications Standards in prehistoric or historical archaeology shall be retained to evaluate the finds and recommend appropriate action. All construction must stop if any human remains are uncovered, and the County Coroner must be notified according to Section of California s Health and Safety Code. If the remains are determined to be Native American, the procedures outlined in CEQA Section (d) and (e) shall be followed. Geology, Soils, Minerals, and Paleontological Resources Sacramento LAFCo and City of Elk Grove

13 Elk Grove Land Grading and Erosion Control Ordinance The City s Land Grading and Erosion Control Ordinance (Elk Grove Municipal Code, Title 16, Chapter 16.44) was enacted to minimize degradation of water quality and runoff of sediment and pollutants from construction-related activities. The ordinance establishes administrative procedures, minimum standards of review, and implementation and enforcement procedures for controlling (1) erosion, sedimentation, and other pollutant runoff (including construction debris and hazardous substances used on construction sites), and (2) the disruption of existing drainage and related environmental damage. A grading and erosion control permit is required for activities that disturb 350 cubic yards or more of soil, or for clearing 1 acre or more of land. The ordinance also requires that applicants submit a grading and erosion control plan. The plan must contain, among other items: the location, implementation schedule, and maintenance schedule of all erosion control and sediment control measures; a description of measures designed to control dust and stabilize the construction site road and entrance; and a description of the location and methods of storage and disposal of construction materials. Professional Paleontological Standards The SVP (1995, 1996) guidelines outline professional practices for paleontological resource assessments and surveys, monitoring and mitigation, data and fossil recovery, sampling procedures, specimen preparation, analysis, and curation ENVIRONMENTAL IMPACTS AND MITIGATION MEASURES METHODOLOGY The evaluation of potential impacts on geology, soils, minerals, and paleontological resources is based on the project location, expected construction methods, NRCS soil survey data, CGS mineral land classification studies, and published seismic and geologic resources data (including maps). The information obtained from these sources was reviewed and summarized to establish existing conditions and to identify potential environmental effects based on the standards of significance presented below. THRESHOLDS OF SIGNIFICANCE Geology, Soils, and Minerals The thresholds for determining the significance of impacts for this analysis are based on the environmental checklist in Appendix G of the CEQA Guidelines, as amended. The proposed Project would have a significant impact on geology, soils, or mineral resources 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; Sacramento LAFCo and City of Elk Grove Geology, Soils, Minerals, and Paleontological Resources

14 strong seismic ground shaking; seismic-related ground failure, including liquefaction; or landslides; result in substantial soil erosion or the loss of topsoil; be located on a geologic unit or soil that is unstable or that would become unstable as a result of the Project and potentially result in on- or off-site landslide, lateral spreading, subsidence, liquefaction, or collapse; be located on expansive soil, as defined in table 18-1-b of the uniform building code (1994), creating substantial risks to life or property; 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; result in the loss of availability of a known mineral resource that would be of value to the region and residents of the state; or result in the loss of availability of a locally important mineral resource recovery site. Paleontological Resources Based on Appendix G of the CEQA Guidelines, the proposed Project would have a significant impact on paleontological resources if it would directly or indirectly destroy a unique paleontological resource or site. A unique paleontological resource or site is one that is considered significant under the professional paleontological standards described below. The SVP guidelines (1995) established three categories of sensitivity for paleontological resources: high, low, and undetermined. Areas where fossils have been previously found have a high sensitivity and a high potential to produce fossils. Areas that are not sedimentary and have not produced fossils in the past have low sensitivity. Areas that have not been surveyed or have no fossil finds are considered of undetermined sensitivity. In accordance with the SVP significance criteria (1995), all vertebrate fossils are generally categorized as being of potentially significant scientific value. An individual vertebrate fossil specimen may be considered unique or significant if it is identifiable and well preserved, and it meets one of the following criteria: a type specimen (i.e., the individual from which a species or subspecies has been described); a member of a rare species; a species that is part of a diverse assemblage (i.e., a site where more than one fossil has been discovered) wherein other species are also identifiable, and important information regarding life history of individuals can be drawn; a skeletal element different from, or a specimen more complete than, those now available for its species; or Geology, Soils, Minerals, and Paleontological Resources Sacramento LAFCo and City of Elk Grove

15 a complete specimen (i.e., all or substantially all of the entire skeleton is present). Marine invertebrates generally are common and the fossil record is well developed and documented; therefore, marine invertebrate fossils would generally not be considered a unique paleontological resource. Identifiable vertebrate marine and terrestrial fossils generally are considered scientifically important because they are relatively rare. ISSUES NOT DISCUSSED FURTHER Expose People or Structures to Surface Fault Rupture The SOIA Area is not located in an area classified as an Alquist-Priolo Fault Zone (CGS 2015). Sacramento County does not have any known active faults within its boundaries according to the USGS Earthquake Hazard Program Quaternary Faults maps. No impacts related to loss, injury, or death involving rupture of a known earthquake fault would occur. Therefore, this issue is not addressed further in this EIR. Expose People or Structures to Landslides The SOIA Area is characterized by an entirely flat topography, which also precludes it from the possibility of landslides. Therefore, no impact would occur and this issue is not addressed further in this EIR. Have Soil Unsuitable for Septic Systems No use of an on-site wastewater disposal systems are proposed; therefore, no impact related to the ability of site soils to support the use of septic systems would occur. This issue is not addressed further in this EIR. Loss of Known or Locally Important Minerals No active mining or natural gas extraction operations are located within the SOIA Area boundary. Based on the California Geological Survey s Mineral Resource Zone classifications under the Surface Mining and Reclamation Act, the SOIA Area is zoned as MRZ-3, which indicates areas of undetermined mineral resource significance. In addition, the Sacramento County General Plan does not designate any locally important mineral resource recovery sites within the SOIA Area. Therefore, there would be no loss of known or locally important mineral resources, and this issue is not addressed further in this EIR. IMPACT ANALYSIS IMPACT Exposure to strong seismic ground shaking. Future development within SOIA Area, including the multisport park complex, would not expose people or structures to potential substantial adverse effects, including the risk of loss, injury, or death involving strong seismic ground shaking. The impact is considered less than significant. Strong seismic ground shaking from earthquakes creates risks to people and structures through damage or collapse of buildings and structures, dependent on the intensity of shaking. Future development within the SOIA Area, including the multi-sport park complex, would increase the amount of people and structures within the SOIA Area, potentially exposing them to risks associated with strong seismic ground shaking. The Sacramento Valley has historically experienced low levels of seismic activity. Known active faults that pose a hazard for strong seismic ground shaking are located along the margin between the western Sacramento Valley and the eastern Coast Ranges, and within the Coast Ranges themselves (Table 3.7-1). These faults are located Sacramento LAFCo and City of Elk Grove Geology, Soils, Minerals, and Paleontological Resources

16 30 to 40 miles west of Elk Grove. However, in the event of a major earthquake along any of these regional faults, facilities in the SOIA Area would be subject to seismic ground shaking. Construction of structures, utilities, or roadways associated with future development of the SOIA Area, including development of the multi-sport park complex project, would be required to comply with seismic design provisions of the CBC, applicable local codes, and applicable General Plan policies that contain provisions to ensure that buildings or other structures are designed to be able to withstand reasonably expected ground shaking intensities of the SOIA Area. Future development would increase the amount of people and structures at risk of adverse effects from strong seismic ground shaking. However, based on the California Geological Survey s low predicted likelihood of strong seismic ground shaking in the SOIA Area, including the multi-sport park complex site, and the seismically sound design provisions required by the CBC and other existing regulations, impacts related to exposing people or structures to potential adverse effects from strong seismic ground shaking is considered less than significant. Mitigation Measures No mitigation measures are required. IMPACT Seismic-related ground failure. Future development within the SOIA Area, including the multi-sport park complex, could expose people or structures to potential substantial adverse effects, including the risk of loss, injury, or death involving seismic-related ground failure, including liquefaction. However, the California Geological Survey predicts low probability of strong seismic events in the vicinity of the SOIA Area, and existing regulations require structures are designed to minimize risk associated with liquefaction, lateral spreading, and collapse. The impact is considered less than significant. Future development within the SOIA Area, including the multi-sport park complex, would increase the amount of people and structures within the SOIA Area, potentially exposing them to risks associated with seismic-related ground failure. Seismic-related ground failures, such as soil liquefaction, lateral spreading, and collapse can result from changes in soil physics during seismic shaking. Liquefaction occurs when earthquakes cause sandy particles to separate, causing soil to lose strength and act as a fluid. This can cause damage to large or heavy structures on shallow foundations through cracking, tilting, and differential settlement, which can in turn pose risks to the safety of persons within or near these structures. Lateral spreading and landslides occur when seismic shaking causes lateral movement of soil due to liquefaction. Whole buildings can be damaged or moved downslope by this type of ground failure. As discussed above, the SOIA Area and surrounding area do not have a history of strong seismic ground shaking, nor is it expected to experience ground shaking in the future, which generally precludes it from the effects of liquefaction. However, where there is slight potential for liquefaction, structural and foundation design for new construction activities can minimize or eliminate liquefaction hazard. As discussed in the Regulatory Framework in Section 3.7.2, all construction would be required to comply with the CBC, which includes provisions related to designing structures to be able to withstand reasonably expected seismic activity. Site-specific geotechnical investigations would also be required prior to construction to identify and engineer for the geological limitations of each construction site. Geology, Soils, Minerals, and Paleontological Resources Sacramento LAFCo and City of Elk Grove

17 Development as a result of the proposed SOIA could lead to increased numbers of people and structures at risk of loss or damage from seismic-related ground failure. However, the California Geological Survey predicts low probability of strong seismic events in the vicinity of the SOIA Area, including the multi-sport park complex site, and existing regulations require structures are designed to minimize risk associated with liquefaction, lateral spreading, and collapse. Therefore, the impact is considered less than significant. Mitigation Measures No mitigation measures are required. IMPACT Unstable soils. Future development within the SOIA Area, including the multi-sport park complex, could not result in the Project being 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. However, existing regulations such as the CBC, General Plan policies, and local ordinances require site investigations and sound design practices, which would minimize these potential effects. The impact is considered less than significant. As discussed previously, landslides, lateral spreading, and liquefaction can occur as a result of unstable soils experiencing seismic shaking. When soil becomes destabilized it can cause large-scale movement down slopes or compromise soil strength, which can adversely affect the people or structures the soil supports. Subsidence occurs when water or other fluids are extracted from the soil, causing soils to collapse or their organic matter depleted from microbial respiration. Collapse occurs when soils are located over subterranean caves, mines, or other weak underlying subsurface material. A review of NRCS soil survey data indicates that the Durixeralfs, Galt, Kimball, and San Joaquin Galt complex soil series in the SOIA Area, including the multi-sport park complex site, are rated as very limited for construction of buildings and roads because of low soil bearing strength (Table 3.7-2), which in turn could result in hazards from subsidence and settlement (NRCS 2015a). Compliance with CBC requirements would reduce or avoid these hazards through BMPs and building design intended to withstand unstable soils. Site-specific geotechnical investigations would be required prior to construction per local ordinances, which would identify potential stability issues and incorporate design measures to minimize risk associated with unstable soils. Development within the SOIA Area, including the multi-sport park complex, could have the potential to be located on unstable soils. However, existing regulations such as the CBC, General Plan policies, and local ordinances require site investigations and sound design practices, which would minimize potential effects related to unstable soils or associated landslide, lateral spreading, subsidence, liquefaction, or collapse. Therefore, the impact is considered less than significant. Mitigation Measures No mitigation measures are required. Sacramento LAFCo and City of Elk Grove Geology, Soils, Minerals, and Paleontological Resources