4.4 GEOLOGY AND SOILS

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1 Environmental Impacts Analysis: Geology and Soils 4.4 GEOLOGY AND SOILS This discussion addressed potential geologic impacts resulting from implementation of the proposed project. One study has been submitted by the applicant s consultants, and is listed as follows: Soils Engineering Report, Grover Beach Lodge, Pismo Beach State Park, West of Highway 1 and North of Grand Avenue, Grover Beach, California, prepared for Pacific Companies for the City of Grover Beach by GeoSolutions, Inc., September 14, 2010 (report is contained in Appendix I of this EIR). General city-wide conditions were evaluated in the Master EIR prepared in 2009; this document, certified by the City of Grover Beach on February 16, 2010, indicated that city-wide, there were no significant geological impacts resulting from build-out of the city limits, including the proposed project site. Information contained in this EIR has also been referenced with regard to geologic conditions and potential hazards. In addition, a Mitigated Negative Declaration was prepared and certified by the Grover Beach City Council for the proposed Pacific Coast Hotel located at 105 West Grand Avenue, adjacent to the proposed project site, as shown on Figure 3-1 of this EIR. This document also indicates that no significant geologic hazards or risks are present in the vicinity. The Master EIR and Land Use Element Update can be referenced on the Grover Beach web site at The Mitigated Negative Declaration for the Proposed Pacific Coast Hotel is included as Appendix B of this EIR. The State Parks General Development Plan also included a general geology and geomorphologic evaluation of the Pismo State Beach and Vehicular Recreation Area, including the proposed project site. This information is incorporated by reference and can be found in Appendix F of this EIR Existing Conditions Geologic and Soils Characteristics The project site is located to the San Luis Range of the Coast Range Geomorphic Province of California (SMB-SLR) located between the Pacific Ocean and the Sacramento-San Joaquin Valley. The Coast Ranges trend northwesterly along the California coast for approximately 600 miles between Santa Maria and the Oregon border. This domain s surface geology consists of Quarternary and Holocene sediments of alluvium and dune deposits underlain by Jurassic Age Franciscan basement. Based on geologic maps, the site is situated on alluvial gravel, sand, and clay (Dibblee 2006). Elevation of the site varies between 7 and 14 feet above sea level. Appendix I contains a local geologic map for further reference to geologic map units and geologic characteristics for the site; refer also to Appendix F for a further general discussion of geologic conditions as reported in the State Parks General Development Plan for the project site and surrounding State Parks unit. GeoSolutions soils report (Appendix I) contains soils profiles taken on site, and these profiles indicate interbedded layers of sands, silty sands, clayey silt to sandy silt. Groundwater was encountered in three soundings at a depth of 5.0 to 10.0 feet below ground surface (bgs). No unique geologic features exist on the site, the site is relatively level and does not have any City of Grover Beach 4-87 Grover Beach Lodge and Conference Center

2 Chapter 4 steep slopes or landslide prone areas. Coastal dune complex borders the property to the west. Erosion potential is low Seismic Conditions and Liquefaction The Southern Coast Ranges Province is one of the most complex geologic provinces in the State. It is characterized by a number of sub-parallel structural blocks bounded by several onand off shore faults. Earthquake-related hazards have the potential to result in public safety risks and property damage in Grover Beach. Several secondary seismic hazards are associated with strong seismic shaking, especially in areas characterized by a relatively shallow ground water table and underlain by loose, cohesion-less soils deposits. These secondary seismic hazards include fault rupture, liquefaction, and ground shaking. The project site is located approximately three miles from the Oceano fault, an inactive fault that trends northwest/southeast along the coastline. Rupture of this fault may cause ground shaking and damage to property. The GeoSolutions Soils Report includes a seismic hazards analysis based on the distance of the site from known active faults, the expected magnitude of the Maximum Considered Earthquake (MCE) and the site soil profile characteristics. Based on the various structural design parameters, GeoSolutions concludes that the site is underlain by sandy soils that under static loading conditions may provide adequate bearing for foundations provided that loads are kept relatively light. Under seismic loadings the soils below the groundwater interface may liquefy. The result of liquefactions would be settlements of 1 to 2 inches across the site and possibility of sand boils manifesting at the surface (for design purposes, they recommend planning for a sand boil of 12 feet in diameter). The occurrence of sand boils would cause a sudden and complete loss of support under building foundations, and the most critical point would be building corners. Based on the results of the Soils Report, the project can be constructed to withstand ground shaking consistent with building code requirements Erosion Soils in the City are mapped by Natural Resources Conservation Service (NRCS) and documented in the Soils Surveys for San Luis Obispo County. Tests performed on those soils help engineers determine their characteristics (i.e., permeability, strength, composition, etc.). Typically, erosive factors are used to predict the erodibility of a soil and its tolerance to erosion in relations to specific kinds of land use and treatment. Erosive factors are influenced by factors such as plant cover, grade and length of slope, management practices, and climate. Erosion on the project site is relatively limited due to the relatively flat topography. The NRCS maps the soils on site as follows (refer to Appendix I for the Soils map and complete description of the soils unit numbers are given for reference to the appendix map): 124-Corralitos Sand-0 to 2 percent slopes. This is a very deep somewhat excessively drained, nearly level soil on alluvial fans and plains, and covers most of the project site, specifically in the area of the proposed lodge structures. Permeability of this soil is rapid, and available water capacity is low. Surface runoff is slow. The hazard of water erosion is slight, and the hazard of soil blowing is high. This soil has few limitations for construction. City of Grover Beach 4-88 Grover Beach Lodge and Conference Center

3 Environmental Impacts Analysis: Geology and Soils 125-Corralitos Sand-2 to 15 percent slopes. The description of this soil is the same as for Corralitos Sand on gentler slopes given above, and is found in the northernmost portion of the property near the golf course. Permeability of this soil is rapid, and available water capacity is low. Surface runoff is slow. The hazard of water erosion is slight, and the hazard of soil blowing is high. This soil has few limitations for construction. 134-Dune land. This soil is found in hilly areas along the coast that are composed of sand-sized particles that shift with the wind. Most areas are almost devoid of vegetation; included are some areas that are partially covered with California sagebrush or beach grass and are somewhat stabilized. Permeability of this soil is rapid, and available water capacity is low. Surface runoff is slow. The hazard of water erosion is slight, and the hazard of soil blowing is high. Most areas of Dune land are used for recreation, as is the case with the proposed project in the areas west of the project site, including the parking area and Fin s restaurant and dune complex at the beach front, the entrance area to the State Vehicular Recreation Area and North Beach and the dunes located south of West Grand Avenue in the area of the proposed equestrian parking (Area C on Figure 2-6) and equestrian and hiking trails. 170-Marimel silty clay loam, drained. This very deep, well drained, nearly level soil is on alluvial fans and has been naturally drained because of the downcutting of nearby streams (in this case, Meadow Creek). Permeability of this soil is moderately slow, and the available water capacity is high or very high. Surface runoff is slow, and the hazard of water erosion is slight. This soil has few use limitations if properly drained. This soil is found in project Area D (see Figure 2-6) and covers the area proposed for the RV Sewer dump station expansion at the entrance to the State Parks North Beach Campground. 194-Psamments and Fluvents, wet. This map unit consists of small, very poorly drained basins in areas of Dune land or in coarse textured valley alluvium near streams, such as Meadow Creek. This soil unit is in the Meadow Creek corridor on the project site. The soils are wind- or water-deposited sands and loamy sand that commonly contain layers of organic material. Vegetation is water and salt tolerant grasses and forbs. These soils are poorly drained. Free water is within 10 or 20 inches of the surface for most of the year. These soils are mainly used for wildlife habitat. Based on soils characteristics and topography, erosion is not likely to be a significant issue and any slopes or berms associated with the project would be subject to sheet or rill erosion during rainfall, although if the slopes are well-vegetated, it would minimize any damage. Erosion from sheet flow across the project site and any point source discharge into Meadow Creek would cause erosion along creek banks or in adjacent riparian habitat, since soils are poorly drained in the vicinity of the creek Regulatory Setting Alquist-Priolo Earthquake Hazards Zone Act The Alquist-Priolo Earthquake Hazard Zone Act (originally the Alquist-Priolo Special Studies Zone Act of 1972) requires that zones along sufficiently active and well-defined faults be established. The zones vary in width, but are in general approximately 0.25 mile wide. Development is limited in areas defined as Earthquake Hazard Zones and structures for human occupancy are generally not permitted. The act regulates structures with human occupancy or City of Grover Beach 4-89 Grover Beach Lodge and Conference Center

4 Chapter 4 usage of 2,000 person-hours per year or more. The project site is not in or adjacent to an Alquist-Priolo Zone Uniform Building Code and California Building Code The Uniform Building Code (UBC) and the California Building Code dictate seismic design parameters for structures in California. The UBC provides a standard for building laws. Published by the International Conference of Building Officials, the UBC is a widely adopted model building code in the United States. The 2010 UBC is considered the latest edition and has been adopted by the City. The California Building Code incorporates by reference the UBC with necessary California amendments. The California Building Code is codified in the California Code of Regulations (CCR) Title 24 Part 2, commonly known as the California Building Standards Code. Title 24 is assign to the California Building Standards Commission, which, by law, is responsible for coordinating all building standards. Under state law, all building standards must be centralized in Title 24 or they are not enforceable. About one third of the text within the California Building Code has been tailored for California earthquake conditions Local Policies and Regulations for safety The Safety Element (Government Code Sections ) is a required element for the protection of the community from geologic hazards that must include features to minimize risks associated with these hazards. The Safety Element of the Grover Beach General Plan, adopted by the City on October 16, 2000, presents policies and implementation measures with respect to geologic and seismic hazards, with the objective of minimizing the potential for loss of life and property. The policies address hazards associated with seismicity, fault rupture, ground shaking, liquefaction and seismic settlement, slope instability, landslides and coastal bluff erosion. In accordance with this regulation, any proposed development shall be designed to comply and be consistent with the Safety Element Thresholds of Significance The thresholds of a significant soils hazard, geologic, or seismic impact is that which could result in the following: 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 or other substantial evidence of a known fault, as well as strong seismic ground shaking, seismic-related ground failure, or landslides. Result in substantial soil erosion or the loss of topsoil. Result in the loss of a unique geologic feature. 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, creating substantial risks to life or property. City of Grover Beach 4-90 Grover Beach Lodge and Conference Center

5 Environmental Impacts Analysis: Geology and Soils Impact Assessment and Methodology Soils, geologic and seismic hazards and impacts, and environmental hazards and impacts were evaluated based upon a review of the GeoSolutions report, Master EIR for the Land Use Element Update, existing information contained in the State Parks General Development Plan, Pacific Coast Hotel MND and a site reconnaissance Project-Specific Impacts and Mitigation Measures Faulting and Seismicity No active faults cross the project area but the project site is subject to seismic activity due to its proximity to numerous faults, including local faults associated with the San Luis Range fault system which are within 3 miles from the project area, and the San Andreas fault, located approximately 42 miles from the project site. Seismic activity can induce liquefaction, resulting in settling or cracking of foundations. Specific to this site is the potential for sand boils which could cause a sudden and complete loss of support under building foundations. Settlement is estimated by GeoSolutions to be about 1 to 2 inches across the site. Two potential mitigation strategies are discussed in the GeoSolutions Soils Report; one is to construct a mat foundation or post-tensioned slabs. A reinforced slab inches thick with two reinforcement layers could be considered. Conventional driven piles may be required where loads exceed what a matt foundation can distribute over the foundation system. The other strategy to mitigate for liquefaction is to use vibro-replacement (stone column) in-situ soil densification, or groups of driven pile deep foundations know as compaction piles, embedded into dense material. Stone columns may be required to a depth of 40 feet below ground surface, extending 15 feet beyond the perimeter of the buildings. However, the data obtained during GeoSolutions field investigation indicates that the incremental improvement to the site may not justify this strategy. GS Impact 1 The project site may become unstable when a seismic event results in liquefaction of the underlying soils. GS/mm-1 Construction of the project site shall follow the conclusions and recommendations given in the GeoSolutions Soils Report, dated September 14, These apply to preparation of building pads, mat foundation, driven piles, preparation of paved areas, foundation settlement, slab-on-grade construction, retaining walls, pavement design and additional geotechnical services needed during plan development, review of grading and foundation documents prior to construction and construction inspections and testing as required, including but not limited to, stripping, grading, over-excavating, backfill placement, imported materials, site densification, foundation excavation observations and compaction. GS/mm-2 Foundation design shall conform to the requirements of Chapter 18 of the latest edition of the California Building Code. City of Grover Beach 4-91 Grover Beach Lodge and Conference Center

6 Chapter 4 Residual Impact With implementation of mitigation this impact would be considered insignificant Erosion Construction activities would result in exposed soils that could wash into nearby Meadow Creek. Although the applicant indicates that cuts and fills would be balanced on site, because the soils are sandy and subject to wind blowing, it is possible that disturbing the project surface could carry soils into the creek. Berming, associated with landscaping and creek protection, also could rill and erode if not sufficiently revegetated. Introducing additional people onto the site as a result of the lodge and beach activities could cause erosion to the existing dune complex to the west of the site (in the picnic areas and adjacent to boardwalks, between the project site and the sandy beach). These impacts are relatively minor and easily mitigated. To the south of West Grand Avenue are existing trails through the dune complex currently being used by equestrians and hikers.by providing a specific parking area for equestrian use, these trails could be further impacted by increased equestrian use, and dune lands could further erode from horses and hikers, possibly creating new trails through the dune complex. Although this is an existing use, the proposed improvements and signage could increase usage to the detriment of the dune complex. Erosion impacts to the dunes would occur regardless of the location of the equestrian parking area location. Mitigation would be necessary to designate the trails and rehabilitate the existing disturbed dune habitat in order to reduce the effects of erosion on the dune complex. GS Impact 2 GS/mm-3 Soils disturbed during construction and general site use after construction would be subject to erosion from stormwater and flooding events, watering of landscaping, and secondarily from increased public access to sensitive wetland and dune habitat areas (Areas A and C). Prior to issuance of grading permits for Areas A and C, an erosion control plan shall be developed in conjunction with RWCQB staff, City staff and State Parks biologists to ensure that sensitive areas are protected. Measures in the plan shall include measures to deter sands from blowing into Meadow Creek and the creek buffer area during grading, retention and settling of spray waters from irrigation prior to discharge into the creek, adequate dampening of graded areas during construction to reduce blowing sand, and measures to reduce rilling of any stockpiled soils. The plan shall be completed prior to construction; during construction, monitoring of construction activities shall occur as needed to ensure compliance with the erosion control plan. Residual Impact With implementation of mitigation this impact would be considered insignificant. GS Impact 3 Introduction of additional visitors into the dune complex could increase the potential for development of new trails through the dunes to the west of the project site and to the south of West Grand Avenue thus causing increased erosion and loss of dune habitat (Areas A, B and C). Implement BIO/mm-1 through BIO/mm-14 related to revegetation and restoration efforts to reduce erosion and restore habitat areas throughout the project site. City of Grover Beach 4-92 Grover Beach Lodge and Conference Center

7 Environmental Impacts Analysis: Geology and Soils Implement DES/mm-1 through DES/mm-5 related to control of stormwater runoff into Meadow Creek and incorporation of bioswales into the riparian habitat area to reduce erosion and resultant pollutants into Meadow Creek and adjacent watersheds. GS/mm-4 GS/mm-5 The erosion control plan required in GS/mm-3 for Area C shall be expanded to include restoration of the dune complex adjacent to the proposed equestrian parking area. The area for erosion control shall include the vicinity of the parking area as determined by the City and State Parks. The plan shall also include measures to block off and restore minor trails, and fence (type to be determined in consultation with State Parks and could be peeler core or pipe and cable) at least 100 feet along both sides of a major trail from the parking area to the beachfront to the west and from the parking area to the overall trail system accessible to the east of the parking lot. Erosion control shall be coordinated with revegetation and restoration of habitat areas associated with this project and with any revegetation efforts ongoing by State Parks. Work effort shall be completed prior to occupancy of the Grover Beach Lodge. Assistance from equestrian groups in restoration and rehabilitation efforts along these trails is recommended. Prior to issuance of a grading permit for the equestrian parking area, the applicant shall include a retaining wall and fencing or other method, if needed, along the interior perimeter of the parking area to retain sand and to act as a deterrent to equestrians and horses from crossing the fill area to gain access to trails. The retaining wall shall be of sufficient height to reduce fill from falling back into the parking area. Residual Impacts There is always the potential that grading during construction and increased public use could cause erosion in landscaped areas and in adjacent natural areas, beachfront dunes, Meadow Creek riparian area, and dune complex south of West Grand Avenue. This possibility is decreased by revegetation. Generally, once mitigation is in place, impacts would be reduced to insignificance Cumulative Impacts Potential impacts related to geologic, soils and seismic hazards are all site-specific, and mitigation measures are applied to each project to minimize the potential for significant geologic impacts. All development projects are required to comply with State and local regulations regarding grading and construction; therefore, cumulative impacts related to these issues would be less than significant. No mitigation is required. City of Grover Beach 4-93 Grover Beach Lodge and Conference Center

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