5.5 GEOLOGY, SOILS, AND SEISMICITY

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1 5.5 GEOLOGY, SOILS, AND SEISMICITY This section of the environmental impact report (EIR) describes the existing geology and soils conditions in the Project area and analyzes the potential for impacts associated with hazards that could be caused by seismic activity (groundshaking, landsliding, liquefaction), development on unstable geologic units or expansive soils, and potential erosion that could result from Goals, Policies, and Actions presented in the General Plan Update. Implementation of the General Plan Update will not directly result in any specific development project; individual projects would undergo environmental review as they are proposed. As such, while no specific project is addressed in this Program EIR, this discussion will instead focus on potential impacts from geologic hazards, associated with new Goals, Policies, and Actions contained in the General Plan Update to guide future development in the City. Information in this section is based on previous reports such as the Geologic Map of the Fontana 7.5 Quadrangle, which was produced as part of the Southern California Areal Mapping Project (SCAMP) as a joint effort by the United States Geologic Survey (USGS) and the California Geologic Survey (CGS), as well as the Fault Activity Map of California and adjacent Areas (CGS) Regional Geology The City of Fontana generally lies within the northern and northwestern portion of the Peninsular Ranges Geomorphic Province of Southern California, which is characterized by northwestsoutheast trending faults, folds, and mountain ranges. During the time from the Pliocene period to the Pleistocene period (the past 2 to 3 million years), activities on the Newport-Inglewood Fault, combined with regional tectonic effects (such as uplift), climatic forces, and changes in sea level, have resulted in the formation of the underlying basement materials and structures that underlay and support the Project area. The forces that have created the geomorphology of the Project area and vicinity are still active today. Much of the region is underlain by terrace deposits, which are unconsolidated sediments (i.e., loose soil materials, such as sand, silt, etc.) left by streams on shore benches cut by the ocean. These deposits were laid in a shallow marine to near-shore terrestrial environment in the Pleistocene timeframe (about two million to about ten thousand years ago). The source of these sediments was erosion of the rocky highlands of San Bernardino, Santa Ana, and other mountain belts. Tectonic forces associated with regional faulting from the Newport-Inglewood, Cucamonga, Chino, San Andreas, San Joaquin, and additional off-shore zones uplifted these deposits, exposing the terrace materials to erosion that removed much of their cover. In late Pleistocene time, the action of coastal plain rivers and streams dissected the terrace materials and subsequently formed gaps. As sea levels subsequently rose with the melting of continental ice sheets, sediments filled these gaps

2 5.5.2 Seismic Setting The faulting and seismicity of Southern California is dominated by the San Andreas Fault zone. The zone separates two of the major tectonic plates that comprise the earth s crust. The Pacific Plate lies west of the fault zone. This plate is moving in a northwesterly direction relative to the North American Plate, which lies east of the fault zone. This relative movement between the two plates is the driving force of fault ruptures in western California. There are numerous faults in Southern California that are categorized as active, potentially active, and inactive. A fault is classified as active by the state if it has either moved during the Holocene epoch (during the last 11,000 years) or is included in an Alquist-Priolo Earthquake Fault zone (as established by the California Geological Survey). A fault is classified as potentially active if it has experienced movement within the Quaternary period (during the last 1.6 million years). Faults that have not moved in the last 1.6 million years generally are considered inactive. The severity of an earthquake generally is expressed in two ways magnitude and intensity. The energy released, as measured on the Moment Magnitude (MW) scale, represents the magnitude of an earthquake. The intensity of an earthquake is measured by the Modified Mercalli Intensity (MMI) scale, which emphasizes the seismic response at a subject site and measures groundshaking severity according to damage done to structures, changes in the earth surface, and personal accounts (see Table 5.5-1). Table MMI Scale MMI I II III IV V VI VII VIII IX X XI XII Detected by only sensitive instruments Felt by a few people at rest Description Felt noticeably indoors, but not always recognized as a quake; vibration like a passing truck Felt indoors by many and outdoors by few Felt by most people. Some breakage of windows, dishes, and plaster Felt by all; falling plaster and chimneys; damage small Damage to buildings varies; depends on quality of construction Walls, monuments, chimneys fall; panel walls thrown out of frames Buildings shift off foundations; foundations crack; ground cracks; underground pipes break Most masonry and frame structures destroyed; ground cracks; landslides Ground fissures; pipes break; landslides; rails bent; new structures remain standing Damage total; waves seen on ground surface; objects thrown into the air SOURCE: United States Atomic Energy Commission

3 Major active faults in the Study Area vicinity are listed in Table Although there are no major active faults within the City boundaries, there are a number of faults that border the Lytle Creek alluvial basin, including the Chino, Cucamonga, San Andreas, and San Jacinto faults, as described below. All structures associated with the development covered by the proposed General Plan Amendment would be required by state law and regulation to comply with all adopted geotechnical design criteria. Table Major Fault Zones near Fontana Fault Zone Mw Magnitude San Jacinto 7.2 Chino Whittier-Elsinore San Andreas (southern) 7.8 Cucamonga SOURCE: California Geological Survey 1998 Cucamonga Fault/ Sierra Madre Fault Zone. This fault system is northwest trending and generally right lateral. The fault consists of several near vertical breaks marking the southern boundary of the San Gabriel Mountains. The Cucamonga fault is part of the Sierra Madre Fault Zone. Based on historic earthquakes and evidence of Holocene activity, the fault zone is considered active. Whittier-Elsinore Fault System. The Whittier-Elsinore Fault system consists of several steep to nearvertical faults along a zone as much as one-half mile wide. The inferred sense of movement along these faults is predominately reverse slip west of the Chino area, and right lateral strike slip to the east. Historic seismicity indicate that the fault system is active. The San Jacinto Fault Zone. The San Jacinto Fault is a young, right lateral zone of seismic strain that has dominated fault movement in southern California for a least a century. Notwithstanding the notoriety of the San Andreas Fault, since 1857 there have been thirty-six major earthquakes identified to faults in the San Jacinto system. San Andreas Fault. Extending more than 700 miles, the San Andreas Fault is the longest and most significant system in California. Within and south of the Transverse Ranges, the strike of the fault trends west-northwest within a nearly vertical dip. Motion along the fault is right lateral with post- Oligocene (i.e., less than 22 million years) offset of more than 150 miles. Historic seismicity, sag ponds, offset channels, and linear geomorphic features indicate that this fault system is active

4 Seismicity and Faulting Groundshaking According to the 2016 California Building Code (CBC), the City of Fontana is in Seismic Zone 4. Seismic Zone 4 includes those areas that lie in a zone of major historic earthquakes (i.e., MW magnitude greater than 7.0) and recent high levels of seismicity. Major damage corresponding to intensities VIII or higher on the MMI Scale should be expected within this zone. Thus, strong earthquake groundshaking is a potentially significant seismic hazard throughout the Project area. The amount of earthquake shaking at a site is a function of earthquake magnitude; the type of earthquake source (i.e., type of fault); distance between the site and the earthquake source; the geology of the site; and how the earthquake waves subside (attenuate) as they travel from their source to a given location. Larger, nearer quakes will increase the degree of groundshaking at a given location. Soil and rock type may act to amplify or attenuate seismic waves and consequent groundshaking. Generally, areas that are underlain by bedrock tend to experience less groundshaking than those underlain by unconsolidated sediments such as artificial fill. Surface Fault Rupture Rupture of the surface during an earthquake generally is limited to the narrow strip of land immediately adjacent to the fault on which the earthquake is occurring. Surface fault rupture may occur suddenly during an earthquake or slowly in the form of fault creep and almost always follows pre-existing faults, which are zones of weakness. Secondary surface faulting can be triggered by aquifer compaction and subsidence or by the effects of strong groundshaking triggering a slip on neighboring faults. Not all earthquakes will result in surface rupture and the Alquist-Priolo Earthquake Fault Zone Act instigated a statewide program to identify fault zones that are susceptible to surface rupture. Numerous rupture zones were identified in Project area Soils Soils in the area are characteristic of the Southern California interior alluvial basins, consisting of alluvial deposits and floodplain soils. The City is underlain by the relatively young (Holocene and late Pleistocene) alluvial deposits of the Lytle Creek alluvial fan. These deposits primarily consist of unconsolidated, gray, cobbly and bouldery alluvium. In the southern reaches, the deposits are relatively fine-grained (pebbly and cobbly) and become coarser grained (cobbly and bouldery) to the north Expansive Soils In addition to seismic hazards, soils can exhibit characteristics that can restrict development. Expansive soils possess a shrink-swell behavior that occurs in fine-grained clay sediments from the process of wetting and drying, which may result in structural damage over a long period of time. Settlement occurs when loose, soft soil material comprised of sand, silt, clay, and/or peat if 5.5-4

5 not properly engineered, has the potential to settle after a building is placed on the surface. Settlement of the loose soils generally occurs slowly, but over time can damage structures. Expansive soils are common throughout California and can cause damage to foundations and slabs, separation of masonry, or failure of paved surfaces unless properly treated during construction. Expansive soil conditions could cause damage to facility components if they are not designed with proper engineering and grading practices. The hazard for expansive behavior is considered a low risk for alluvial fan locations because soils in these areas are frequently saturated and generally do not contain clay-sized particles. The risk is low in the Mountains Region because of the generally limited extent, shallow depth, and coarse-grained nature of soils in this area Liquefaction Liquefaction is a phenomenon in which saturated soils lose strength and cohesion when subjected to dynamic forces, such as shaking during an earthquake. Liquefaction can occur in unsaturated soils with low cohesion, such as uniformly fine sand. Liquefaction potential is greatest in areas with shallow groundwater and saturated soils. Soil type, climate, topography, slope geometry, and excavations influence the potential for slope failures and landslides. Liquefaction and related phenomena have been responsible for a tremendous amount of damage during historical earthquakes as soil cohesion is lost, along with the support that it normally supplies to building foundations (Youd 1973). Ground failure resulting from liquefaction can include sand boils, ground settlement, ground cracking, lateral spreading, slope toe failure, and ground warping (Youd and House 1978). Alluvial deposits in San Bernardino County generally contain geologically young, loose, sedimentary deposits, which have the potential to liquefy during intense seismic shaking. Liquefaction typically occurs at depths less than 50 feet below ground surface (bgs), with the most susceptible conditions occurring in sandy soils with less than 15 percent silt and clay at depths shallower than 30 feet bgs (Rosinski 2005). Saturated deposits that are deeper than 50 feet bgs generally are stable regardless of their grain-size distribution. The CGS Seismic Hazard Zone Maps for Study Area identify that areas within the basin are potentially subject to liquefaction. Site-specific geotechnical investigation would determine, on a case-by-case basis, the potential for liquefaction in a given area to ensure that final project design incorporates all necessary and appropriate engineering features to reduce the potential hazards associated with liquefaction Subsidence Soil subsidence at the land surface can result from both natural and man-made phenomena. Natural phenomena that may induce subsidence include tectonic deformation and seismically induced settlements (liquefaction); soil consolidation; oxidation or dewatering of organic-rich soils; and collapse of subsurface cavities. Human activities that may help induce subsidence 5.5-5

6 include decreases in pore pressure caused by the excessive withdrawal of subsurface fluids (pumping), including water and hydrocarbons. The groundwater basin underlying the project area contains a substantial amount of gravel and broken conglomerate in its framework, making it unlikely that, as a result of the accumulated overdraft, the aquifer would compact causing the overlying ground to subside. Potential subsidence is one of several reasons that groundwater overdraft should be minimized. Sitespecific geotechnical investigation would, on a case-by-case basis, determine the potential for subsidence in a given area to ensure that final project design incorporates all necessary and appropriate engineering features to reduce the potential for subsidence-related hazards. However, as the accumulated overdraft range is not anticipated to change as a result of the General Plan Update, the potential for subsidence within the basin would not be expected to change significantly Landslides Landslides, rock falls, and debris flows are all forms of mass wasting, the movement of soils and rock under the influence of gravity. A landslide may occur if source material on a slope is triggered by some mechanism. Source materials include fractured and weathered bedrock and loose soils. Triggering mechanisms include earthquakes, saturation from rainfall, and erosion. Post fire erosion rates may be more than 50 to 100 times greater than on a well-vegetated watershed (Radtke 1983). Shaking during an earthquake may lead to seismically induced landslides, especially in areas that have previously experienced landslides or slumps, in areas of steep slopes, or in saturated hillsides. The City of Fontana is generally flat and not at risk from the threat of landslides. Potential areas where seismically-induced landslides could occur are in the foothill portions of the basin. Still, site-specific geotechnical investigation would, on a case-by-case basis, determine the potential for landslides in a given area to ensure that final project design incorporates all necessary and appropriate engineering features to reduce the potential for landslide-related hazards Soil Erosion Erosion refers to the removal of soil from exposed bedrock surfaces by water or wind. The effects of erosion are intensified with an increase in slope (as water moves faster, it gains momentum to carry more debris), the narrowing of runoff channels (which increases the velocity of water), and by the removal of groundcover (which leaves the soil exposed to erosive forces). Surface improvements, such as paved roads and buildings, decrease the potential for erosion onsite, but can increase the rate and volume of runoff, potentially causing off-site erosion

7 Soil Settlement Soil settlement is the condition where soils deform in a vertical direction when a vertical load is placed on top of it. The compression of the soil bed by the vertical load results from the characteristics of the soil particles that are contained in the soil bed, as the spaces that are filled with either air or water between the soil particles are squeezed out. Site-specific geotechnical investigation would, on a case-by-case basis, determine the potential for soil settlement in a given area to ensure that final project design incorporates all necessary and appropriate engineering features to reduce the potential geologic hazards Thresholds of Significance Implementation of development under the General Plan Update may have a potentially significant impact to geology and geologic hazards if it were to result in any of the following: Expose people or structures to potential substantial adverse effects involving risk of loss, injury, death involving: Rupture of a known earthquake fault, as delineated on the most recent Alquist-Priolo Earthquake Fault Zoning Map issued by the State Geologist for the area or based on other substantial evidence of a known fault Strong seismic ground shaking Seismic-related ground failure, including liquefaction 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-A of the CBC (2001), 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 Environmental Impacts Would the project create a significant hazard to the public or the environment through the exposure of people or structures to potential substantial adverse effects involving risk of loss, injury or death involving rupture of a known earthquake fault or strong seismic shaking or seismic-related ground failure or landslides? Or result in substantial soil erosion? Active and potentially-active faults in Southern California are capable of producing seismic shaking throughout the Project area, and it is anticipated that this area would periodically experience ground acceleration as a result of exposure to small and moderate magnitude earthquakes occurring on active distant and blind thrust faults. New and existing development 5.5-7

8 would be subject to earthquakes that could damage facilities and/or affect reliable use of facilities, including faults identified on the Alquist-Priolo Earthquake Fault Zoning Map. Primary earthquake hazards include damage from ground displacement along a fault zone, severe ground shaking, and induced secondary hazards such as liquefaction in areas that are underlain by unconsolidated alluvial deposits, seismically induced differential settlement, lurching, landslides, and rockfalls. In addition to that described above, as groundshaking hazards are near surface phenomena, pipelines and other infrastructure are particularly susceptible to damage. Damage or rupture of pipelines during a seismic event could result in underground and surface release of water, which could result in localized flooding, erosion, liquefaction, differential settlement, and lateral spreading. The General Plan Update guides the planning of new walkable mixed-use land categories, which promotes development that may result in potential exposure to geologic hazards greater than current conditions. The two new walkable-mixed used land categories are in the Downtown Area Plan and promote pedestrian and bicycle friendly development, increase housing diversity, increase transit use and ensure economic vitality in the downtown and along important corridors. Compliance with federal, state, county, and local regulations relating to the geologic hazards would reduce the potential risk of potential impacts from geologic hazards to a less than significant level. The 2016 CBC Title 24 Section 3417: Earthquake Evaluation and Design for Retrofit of Existing Buildings and the 2016 International Building Codes (IBC) regulate the infrastructure in the City of Fontana. Furthermore, adherence to the mitigation program included in the City s Local Hazard Mitigation Plan (LHMP) to protect life, property and the environment would further reduce potential impacts relative to geologic resources and geologic hazards (City of Fontana, 2017; Appendix F). The intent of hazard mitigation is to reduce and/or eliminate loss of life and property. Hazard mitigation is defined by the Federal Emergency Management Agency (FEMA) as any action taken to reduce or eliminate the longterm rise to human life and property from natural hazards. With the approved and adopted LHMP, the City of Fontana is eligible for federal disaster mitigation funds/grants aimed to reduce and or eliminate/risk. Because the City is in Seismic Zone 4 of the 2016 CBC, structures would be designed in accordance with parameters given within Chapter 16 of the current CBC. In addition, as required by CBC Chapter 16, Division IV for the construction of new buildings and/or structures, specific engineering design and construction measures would be implemented to anticipate and avoid the potential for adverse impacts to human life and property caused by seismically induced groundshaking. Thus, the majority of earthquake-related hazards would be minimized by engineering design, compliance with local, state, and/or federal regulations pertaining to geological hazards, or avoidance of high hazard areas

9 The General Plan Update would not create a significant hazard to the public or the environment through the exposure of people or structures to potential substantial adverse effects. The General Plan Update includes goals, policies, and actions that would further reduce risks from geologic hazards. Applicable Goals, Policies, and Actions from the General Plan Update include the following: Table Applicable Goals, Policies, and Actions Noise and Safety Element Goals & Policies Action Goal 4: Seismic injury and loss of life, property damage, and other impacts caused by seismic shaking, fault rupture, ground failure, earthquake-induced landslides, and other earthquake-induced ground deformation are minimized in the city of Fontana. The City shall monitor development or redevelopment in areas where faults have been mapped through the city. The City shall continue to ensure that current geologic knowledge and peer (third party) review are incorporated into the design, planning, and construction stages of a project and that site- specific data are applied to each project. The City shall continue to ensure to the fullest extent possible that, in the event of a major disaster, essential structures and facilities remain safe and functional, as required by current law. Essential facilities include hospitals, police stations, fire stations, emergency operation centers, communication centers, generators and substations, and reservoirs. A. The City shall strive to ensure that the design of new structures and the performance of existing structures addresses the appropriate earthquake hazards. B. The City shall continue to ensure to the fullest extent possible that in the event of a major disaster dependent care and highoccupancy facilities will remain safe. C. The City shall continue earthquake strengthening and provisions for alternate or back-up essential services, such as water, sewer, electricity, and natural gas pipelines and connections throughout the city. D. The City shall ensure that all residents and business owners in the City have access to information regarding seismic hazards. Goal 9: The City maintains regulations, plans, protocols and emergency training to reduce hazards and risks and to meet state and federal requirements for emergency assistance. Keep hazard-mitigation and emergency services programs up to date. Continue to provide hazard and risk mitigation and emergency training to public employees and the public at large. A. Update the local HMP as required to meet FEMA requirements. B. Explore the opportunity to create Business Emergency Response Training in cooperation with the Fire Department

10 Would the project be located on a geologic unit or soil that is unstable our would become unstable, or potentially result in a potentially significant risk from on- or off-site landslide, lateral spreading, subsidence, liquefaction, or collapse? Would the project be located in an area of expansive soils? The General Plan Update does not consider or analyze specific development projects; therefore, the actual potential for future construction sites or developments associated with the General Plan Update are unknown. However, given the relatively stable geology and soils within the City, it is unlikely that there would be a potential risk that represents a significant change or increase from the conditions that are currently present. Compliance with federal, state, and local regulations would minimize the risks associated with the potential risk from landslides, subsidence, liquification, or collapse relative to existing conditions. San Bernardino County has adopted the 2016 CBC to regulate development in the hillside areas in the City and County. According the City of Fontana 2017 LHMP, there have been no reported historical occurrences of landslides in the City of Fontana. The only areas susceptible to landslips are the southern Jurupa hillsides and the northern part of the city close to the San Bernardino National Forest, but there is a low probability of this hazard affecting these areas in the future. Therefore, future development under the General Plan Update would result in a less than significant impact relative to these potential risks. Adherence to building codes and development that includes site specific geotechnical studies that would be prepared for each specific future project as mandated by the CBC would identify and minimize risks from areas of unstable soils by ensuring the incorporation of recommendations from the site-specific geotechnical investigations into design of plan for those future projects. Overall, the Planning Area would not be located on a geologic unit or soil that is unstable. In addition, the General Plan Update includes goals, policies, and actions would further reduce risks from geologic hazards. Accordingly, impacts are less than significant. Would the project 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? The General Plan Update does not consider or analyze specific development projects; therefore, the actual potential for future construction sites or developments associated with the Update are unknown. The City of Fontana has limited septic systems and given the relatively stable geology and soils within the City, it is unlikely that there would be a potential risk that represents a significant change or increase from the conditions that are currently present. Overall, the City of Fontana is served by a sewer system and the use of septic systems or other alternative wastewater disposal systems would be managed on a case-by-case basis

11 5.5.6 Mitigation Measures No mitigation measures are required that would further reduce the identified less than significant impacts References Borderdt, D., et al Maximum Earthquake Intensity Predicted on a Regional Scale. United States Geological Survey, Miscellaneous Field Investigations Map MF 09, scale 1: 125,000. California Alquist-Priolo Earthquake Fault Zoning Act. Signed into law December 22, 1972; amended 1974, 1975, 1976, 1979, 1991, 1993, and California Public Resources Code, Division 2, Geology, Mines, and Mining, Chapter 7.5, Earthquake Fault Zones, Sections 2621 through California Department of Conservation Fault Activity Map of California. California Geological Survey Maps of Known Active Fault Near-Source Zones in California. CCCarto Faults in the San Bernardino area. City of Fontana, Local Hazard Mitigation Plan. Hart, E.W., and W.A. Bryant Fault-Rupture Hazard Zones in California, Alquist-Priolo Earthquake Fault Zoning Act with Index to Earthquake Fault Zones Maps. California Geological Survey (formerly the Division of Mines and Geology). Special Publication 42, 1997 Edition. Supplements 1 and 2 added 1999, Supplement 3 released 1 May 2003, updated on-line 7 October. International Conference of Building Officials Chapter 16, Structural Forces (earthquake provisions); Chapter 18, Foundations and Retaining Walls; Appendix Chapter A33, Evacuation and Grading. Uniform Building Code. Volumes 1, 2, & 3. Whittier, CA. Jennings, C.W Fault Activity Map of California and Adjacent Areas, with Locations and Ages of Recent Volcanic Eruptions. California Geological Survey. Geologic Data Map No. 6. Scale 1:750,000. Accompanied by 92 pages of explanatory text. Leake, S.A., Land Subsidence from Ground-Water Pumping, United States. Geological Survey, Last modified, January Oakeshott, G.B California s Changing Landscapes: A Guide to the Geology of the States. 2nd Edition. McGraw-Hill Book Company: San Francisco. 378 pages

12 Radtke, Klaus W Living More Safely in the Chaparral-Urban Interface. Technical Report PSW-67. U.S. Department of Agriculture. Rosinski, A.M., California Geological Survey, Geologic and Geotechnical Characterization of Sediment for Liquefaction-Induced Deformation Hazard Maps in the Northern Santa Clara Valley, California, Paper No , Geological Society of America, Cordilleran Section 101st Annual Meeting (April 29, 2005). United States Atomic Energy Commission Nuclear Reactors and Earthquakes. TID Washington, D.C. Youd, T.L Liquefaction, Flow and Associated Ground Failure. U.S. Geological Survey. Circular pages. Youd, T.L., and S.N. House Historical Ground Failures in Northern California Triggered by Earthquakes. U.S. Geological Survey. Professional Paper. 993 pages