GEOLOGY AND SOILS 7.1 INTRODUCTION 7.2 ENVIRONMENTAL SETTING Regulatory Context

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1 CHAPTER 7.0 GEOLOGY AND SOILS 7.1 INTRODUCTION This chapter describes the geologic and soils characteristics of Phases 1 and 2 of the proposed Plan area and evaluates the extent to which implementation of the proposed Plan could be affected by the following geologic and seismic hazards: rupture of a known earthquake fault; strong seismic ground shaking; seismic-related ground failure, including liquefaction; soil erosion; soil stability; and expansive soils. Section 7.2 provides the regulatory context, including state and local laws and policies relevant to geological and soils resources, impacts, and mitigations (where required). This section also provides information on the regional setting and existing conditions within the proposed Plan area. Section 7.3 provides a project level and a program level impact analysis of potential effects associated with the proposed Plan. Mitigation measures to reduce, avoid or eliminate effects to a less than significant level are provided, where appropriate. Guidelines and key sources of data used in the preparation of this chapter include the following: Preliminary Geotechnical Design Recommendations (Hultgren-Tillis Engineers, 2013); Additional Geotechnical Exploration (Hultgren-Tillis Engineers, 2014); General Plan & Pittsburg Municipal Code (, 2001 and 2013); Alquist-Priolo Earthquake Fault Zone Map (California Department of Conservation, 2013); and Association of Bay Area Governments Liquefaction Susceptibility Map (ABAG, 2015). No public or agency comments were received related to geology and soils during the public scoping period in response to the Notice of Preparation. The following sections provide information on the regulatory context as well as information on the regional setting, geology, and soil resources within the proposed Plan area. 7.2 ENVIRONMENTAL SETTING The following sections provide information on the regulatory context, specifically related to the City of Pittsburg General Plan, as well as information on the regional setting, land use, and planning within Phases 1 and 2 of the proposed Plan area Regulatory Context The regulatory setting for Phases 1 and 2 of the proposed Plan is derived from the Clean Water Act / National Pollutant Discharge Elimination System (CWA/NPDES), the California Building Code (CBC), International Building Code (IBC), California s Alquist-Priolo Earthquake Fault Zoning Act (Alquist-Priolo Act), the California Seismic Hazards Mapping Act of 1990, and the General Plan and Pittsburg Municipal Code (PMC). Goals and policies from these documents relevant to geology and soils resources are described below Federal Regulations Federal Clean Water Act. As discussed in Chapter 10.0, Hydrology and Water Quality, CWA 402 (33 U.S.C. 1342) establishes a framework for regulating municipal and industrial stormwater discharges under the NPDES Permit Program. One of the ways that the NPDES program controls water pollution is by regulating May,

2 point sources that discharge pollutants into waters of the United States. Point sources are discrete conveyances, such as pipes or constructed ditches. Examples of pollutants include, but are not limited to, rock, sand, and dirt as well as agricultural, industrial, and municipal waste discharged into waters of the United States. Under the NPDES Phase II Rule, construction activity disturbing one acre or more must obtain coverage under the state s General Construction Permit. General Construction Permit applicants are required to prepare a Notice of Intent (NOI) and a Storm Water Pollution Prevention Plan (SWPPP), and to implement and maintain Best Management Practices (BMPs) to avoid adverse effects on receiving water quality as a result of construction activities, including earthwork. CWA measures at the proposed Plan sites would be control of soil erosion during construction. International Building Code. IBC specifies acceptable design criteria for excavations and structures under both static and dynamic loading conditions. The IBC, which is published by the International Conference of Building Officials, has been developed to promote safe construction as it relates to seismicity State Regulations Porter-Cologne Water Quality Act. As discussed in Chapter 10.0, Hydrology and Water Quality, the Porter-Cologne Water Quality Act of 1969 provides the basis for water quality regulation in California. As with the Federal CWA, the effect on Phases 1 and 2 of the proposed Plan would be control of soil erosion during construction. The San Francisco Regional Water Quality Control Board (SFRWQCB) has jurisdiction over the proposed Plan sites. As part of the General Construction Permit, a SWPPP would be prepared that would include implementation of BMPs to prevent soil erosion. California Building Code. The CBC is contained in Title 24 of the California Code of Regulations (CCR), Part 2, a portion of the California Building Standards Code (CBSC). The purpose of the CBC is to provide minimum standards to safeguard life or limb, health, property, and public welfare by regulating and controlling the design, construction, quality of materials, use and occupancy, location, and maintenance of all buildings and structures. The CBC is based on the IBC, a widely adopted model. The CBC was last updated in 2013 based on the IBC with California-specific amendments. These amendments include building design criteria that must be incorporated into a project to address California s seismic conditions. Phases 1 and 2 of the proposed Plan would be required by the (prior to receiving building permit approval) to demonstrate compliance with all applicable requirements of the CBC. Alquist-Priolo Earthquake Fault Zoning Act. California s Alquist-Priolo Act (Public Resources Code [PRC] 2621 et seq.), originally enacted in 1972 as the Alquist-Priolo Special Studies Zones Act and renamed in 1994, is intended to reduce the risk to life and property from surface fault rupture during earthquakes. The Alquist-Priolo Act prohibits the construction of most types of structures intended for human occupancy across the traces of active faults and strictly regulates construction in the corridors along active faults (Earthquake Fault Zones). It also defines criteria for identifying active faults and establishes a process for reviewing building proposals in and adjacent to Earthquake Fault Zones. Under the Alquist-Priolo Act, faults are zoned, and construction along or across them is strictly regulated if the faults are sufficiently active, and, well-defined. A fault is considered sufficiently active if one or more of its segments or strands shows evidence of surface displacement during Holocene time (defined for the purposes of the Act as within the last 11,000 years). A fault is considered well-defined if its trace can be clearly identified by a trained geologist at the ground surface or in the shallow subsurface, using standard professional techniques, criteria, and judgment (Bryant & Hart, 2007). Seismic Hazards Mapping Act. Like the Alquist-Priolo Act, the Seismic Hazards Mapping Act of 1990 (PRC ) is intended to reduce damage resulting from earthquakes. While the Alquist-Priolo Act May,

3 focuses on surface fault rupture, the Seismic Hazards Mapping Act addresses seismically induced liquefaction and landslides. Under the Seismic Hazards Mapping Act, the permit review process is the primary mechanism for local regulation of development. Specifically, cities and counties are prohibited from issuing development permits for sites in Seismic Hazard Zones until appropriate site-specific geologic or geotechnical investigations have been carried out, and measures to reduce potential damage have been incorporated into the development plans Local Regulations General Plan. The Health and Safety Element of the General Plan contains goals and policies regarding geology and seismic hazards. The goals and policies of the Pittsburg General Plan are targeted at minimizing potential hazards. The goals and policies that may be applicable to Phases 1 and 2 of the proposed Plan are as follows: Goal 10-G-1: Minimize risk to life and property from geologic and seismic hazards; Goal 10-G-2: Establish procedures and standards for geotechnical review of projects located in areas of steep slopes, unstable soils, or other geologic or seismic risks; Goal 10-G-3: Minimize the potential for soil erosion by wind and stormwater runoff; Goal 10-G-4: Mitigate potential seismic hazards, including landslides and liquefaction, during the design and construction of new development; Policy 10-P-1: As part of development review, ensure preparation of a soils report by a City-approved engineer or geologist in areas identified as having geological hazards; Policy 10-P-9: Ensure geotechnical studies prior to development approval in geologic hazard areas. Contract comprehensive geologic and engineering studies of critical structures regardless of location; Policy 10-P-10: As part of development approval, ensure that a registered engineering geologist is available at the discretion of the City Engineer to review reports submitted by applicants in the geologic hazard areas; and Policy 10-P-13: During rehabilitation and redevelopment of industrial properties along the Suisun Bay waterfront, ensure that geotechnical mitigation measures are used to prevent collapse of structures in the event that liquefaction occurs. Municipal Code. PMC Titles 15 and 18 contain the s Building Design and Planning provisions intended to ensure that development occurs safely and would not expose people to seismic or geological hazards (, 2013) Local and Regional Setting The Dow Facility lies within the San Francisco Bay Area portion of the Coast Ranges geomorphic province. The Coast Range province is characterized by northwest-trending mountain ridges and valleys, running subparallel to the San Andreas Fault Zone. Phases 1 and 2 of the proposed Plan would be located on the relatively flat lowland margins of the New York Slough of the Suisun Bay, which are typically underlain by bay mud and Holocene and Pleistocene alluvial fan and fluvial deposits (Helley & Graymer, 1997). The proposed Plan sites are also underlain by artificial fill used to convert the greater area from a marsh to an industrial corridor over the last century. Surficial material at the proposed Plan sites are currently primarily asphalt, compact aggregate base, and gravel. May,

4 Surficial sediments are classified as follows (Helley & Graymer, 1997): Holocene Alluvial Fan and Fluvial Deposits (Qhaf) Holocene age fan deposits that are brown or tan, medium dense to dense, gravely sand or sandy gravel that generally grades upward to sandy or silty clay. Pleistocene Alluvial Fans and Fluvial Deposits (Qpaf) Pleistocene age fan deposits that are brown and are dense gravely and clayey sand or clayey gravel that fines upward to sandy clay. These deposits display various sorting and are located along most stream channels in the county. All Qpaf deposits can be related to modern stream courses. They are distinguished from younger alluvial fans and fluvial deposits by higher topographic position, greater degree of dissection, and stronger soil profile development. They are less permeable than Holocene deposits. Locally they contain fresh water mollusks and extinct late Pleistocene vertebrate fossils. They are overlain by Holocene deposits on lower parts of the alluvial plain and incised by channels that are partly filled with Holocene alluvium on higher parts of the alluvial plain. Maximum thickness is unknown but at least 50 meters. Test borings during geotechnical investigation reveal that shallow artificial fills overlie stiff alluvial clays and silts at the 760 Block (Hultgren-Tillis Engineers, 2013). Artificial fill was determined to be generally less than three feet except in the areas of the former Sym-Tet Fire Water Basin and Latex Fire Water Basin where six to nine feet of clayey fill was encountered (see Hydrology Section for a description of these basins). The alluvial sediment below the artificial fill appears strong and relatively incompressible and contains clayey and silty sand layers less than five feet thick that vary from medium-dense to dense Existing Conditions Seismicity The San Francisco Bay Area contains numerous active faults that are capable of generating large magnitude earthquakes. The USGS evaluated the probability of one or more earthquakes of magnitude at least 6.7 occurring in the San Francisco Bay Area within the next 30 years (USGS, 2008). The result of the evaluation indicated at 63 percent. A list of active faults and their general proximity to the Dow Facility are provided in Table 7-1. According to the, a larger-magnitude earthquake on the nearby Concord-Green Valley Fault could generate ground-shaking intensities with Modified Mercalli Intensity IX in areas north of State Route 4 (, 2001). The closest fault to the Dow Facility is the Pittsburg-Kirby Hills fault, a structure that has been postulated as an active fault beginning near the western boundary of the City of Pittsburg and striking north-northwest across Suisun Marsh to the western end of the Montezuma Hills. Pittsburg-Kirby Hills Fault. The Pittsburg-Kirby Hills fault extends a distance of approximately 26 miles from the Kirby Hills north of the Sacramento River, to the eastern flank of Mount Diablo, south of Pittsburg. Unruh and Sawyer (1995) suggest that the structure is a right lateral tear fault bounding the eastern margin of a series of thrusts and folds in the Grizzly Bay-Van Sickle Island area. The fault is defined by a linear alignment of microseismicity, which is unusual in that it occurs at depths of 20 to 25-kilometers (Wong, Ely, & Kollmann, 1988). Focal mechanisms indicate that the movement on the fault is almost pure right lateral strike slip. Empirical relationships among various fault parameters and earthquake magnitude indicate that the maximum earthquake for the fault is moment magnitude scale (M W) 6.75 (Wells & Coppersmith, 1994). The Pittsburg thrust has been considered to be a potentially active trace (Williams, 1998). In the vicinity of Pittsburg, the fault is defined as the Pittsburg-Kirby Hills Fault Zone and is located approximately 1.8 miles to the west of the 760 Block Site and can be seen in Figure 7-1 (, 2001). May,

5 It should be noted that, although the Pittsburg-Kirby Hills Fault is a known seismogenic 1 structure, it is not included in the regional tectonic model used to predict future earthquake activity in the San Francisco Bay Area (WGNCEP, 1996; 1999). This is due to the fact that the model only includes fault structures with a demonstrated slip rate of 1 mm/yr. and the Pittsburg-Kirby Hills Fault does not meet this criterion. Furthermore, recent trenching studies conducted within the failed to clarify the Pittsburg fault in the near subsurface (Terrasearch, Inc., 2005). Accordingly, this fault structure has been removed from the s Health & Safety Element of the General Plan (, 2001). Table 7-1: Major Active Faults in the Vicinity of Pittsburg, California Fault Hayward Concord- Green Valley Clayton- Greenville San Andreas Calaveras (Northern) Location/Direction from Dow Facility 20-miles west 6-miles west Recency of Movement Historical (1868 rupture) Historical (1955 rupture) Fault Classification Active Active Historical Seismicity 6.8, 1868; many <4.5 Historical active creep Maximum Credible Earthquake 3-miles south Holocene Active None known miles west 15-miles south Historical (1838, 1906, & 1989 ruptures) Historical (1861 rupture) Holocene Active Active 7.1, 1989; 8.25, 1906; 7.0, 1838; many < , 1861; swarms, 1970, Source: (, 2001) Surface Fault Rupture The Dow Facility is not within a quadrangle delineated to have surface fault rupture in the state s Alquist- Priolo Earthquake Fault Zone Map (California Department of Conservation, 2013). It was previously believed that a fault, known as the Pittsburg thrust fault, was located approximately 1.5 miles west of the Dow facility; however, a recent study concluded that the fault does not exist (Environmental Science Associates, 2007) Liquefaction Liquefaction occurs when the strength and stiffness of sediments are reduced by earthquake shaking or other rapid loading. Poorly consolidated, water saturated sands and silts that have low plasticity and are located within 100 feet of the ground surface are typically considered the most susceptible to liquefaction. Soils that are not fully saturated and consist mostly of fine grained materials (cohesive soils) are generally less susceptible to liquefaction. Geologic age also influences the potential for liquefaction. Artificial fill and sediments naturally deposited within the past few thousand years are typically much more susceptible to liquefaction than older Holocene sediments. Pleistocene sediments are even more resistant, while pre-pleistocene sediments are generally immune to liquefaction (California Geological Survey (CGS), 2008). 1 Seismogenic means capable of generating earthquakes. May,

6 Two potential ground failure types typically associated with liquefaction in the region are lateral spreading and dynamic compaction/settlement (Association of Bay Area Governments [ABAG], 2015). Lateral spreading occurs as lateral displacement of gently sloping ground as a result of liquefaction in a shallow underlying deposit during an earthquake. Dynamic compaction may occur due to variable soil conditions, which can adversely impact structures on top of it. Liquefaction may also cause loss of soil load bearing capacity that may cause building foundation failure. Liquefaction hazard in the ranges from very low to very high. The has identified some coastal areas, including the Dow Facility, as having high liquefaction risk. In addition, ABAG has identified the lowland areas immediately adjacent to Suisun Bay as being highly susceptible to liquefaction hazards (ABAG, 2015). The specific areas proposed for the 760 Block Expansion and Railcar Parking, however, are identified as having low potential for liquefaction by ABAG. The site specific geotechnical studies conducted by Hultgren-Tillis Engineers for the 760 Block (Hultgren-Tillis Engineers, 2013, 2014) also concluded that soil underlying the 760 Block has low liquefaction potential, though more testing is recommended. However, a review of existing geotechnical data near the proposed additional railcar parking site indicates that subsurface conditions include a thick layer of loose, saturated sand. This layer exhibits a high risk of liquefaction Landslides Strong ground motions that occur during earthquakes could induce landslides where unstable slope conditions already exist. The portions of Pittsburg having the greatest susceptibility to landslides are hilly areas underlain by weak bedrock units on slopes greater than 15 percent (, 2001). The Dow Facility is not within an area determined to be at risk of landslides. 7.3 IMPACT ANALYSIS This section addresses the impacts to the geology and soil resources surrounding the proposed Plan sites, as well as defines how potential impacts were identified during the analysis Methodology This evaluation is based on a literature review of the following publicly available data and on geotechnical studies conducted by Hultgren-Tillis Engineers on the 760 Block and proposed new railcar parking site: Preliminary Geotechnical Design Recommendations (Hultgren-Tillis Engineers, 2013) and Additional Geotechnical Exploration (Hultgren-Tillis Engineers, 2014) Significance Criteria Criteria for determining the significance of impacts related to geology and soils are based on the environmental checklist form in Appendix G of the State CEQA Guidelines et seq. An impact would be considered significant if the proposed Plan would: Expose people or structures to substantial geologic hazards 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 groundshaking; Seismic-related ground failure, including liquefaction; or Landslides; May,

7 Result in substantial soil erosion or the loss of topsoil; Potentially cause onsite or offsite landslide, lateral spreading, subsidence, liquefaction or collapse as a result of being located on: a geologic unit; soil that is unstable or that would become unstable as a result of the proposed Plan; Be located on expansive soil, as defined in Table 18-1-B of the Uniform Building Code (UBC) (1994); or Be located on soils incapable of adequately supporting the use of the proposed Project s septic tanks or alternative wastewater disposal systems where sewers are not available for the disposal of wastewater. Areas of No Plan Impact The following impacts either are not applicable to Phases 1 and 2 of the proposed Plan or are not reasonably foreseeable: Expose people or structures to potential substantial adverse effects, including the risk of loss, injury, or death involving landslides. As stated in the Initial Study (Appendix B, page 4-11), the proposed Plan area is on relatively flat land with no adjacent hillsides. In addition, the General Plan Chapter 10.0, Health and Safety, does not designate the proposed Plan as being within a potential landslide hazard area. Therefore, the potential for landslides from a seismic event is not expected to result in a significant impact that would cause a risk of upset or a hazardous materials spill from Phases 1 and 2 of the proposed Plan facilities. Therefore, this issue will not be addressed further in this EIR. Located on 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 As stated in the Initial Study (Appendix B, page 4-11), the proposed Plan would not require the use of septic tanks or alternative wastewater disposal systems. The proposed Plan would connect into the Dow Facility s existing sanitary waste system. As a result, Phases 1 and 2 of the proposed Plan would have no impact related to septic systems. Therefore, this issue will not be addressed further in the EIR Potential Significant Impacts and Mitigation Measures Construction-related Impacts Impact Geology and Soils (GEO)-1: Construction of the proposed Project could potentially result in substantial soil erosion or the loss of topsoil. Project-Level Impact Analysis (Phase 1) Significance before Mitigation: No impact. Impact Description: Construction activities associated with the modernization improvements to the 540 Block would not include any ground disturbing activities (e.g., grading or excavation). Therefore, Phase 1 of the proposed Plan would not result in substantial soil erosion or the loss of topsoil. Program-Level Impact Analysis (Phase 2) May,

8 Impact Description: Grading and excavation would be necessary for construction of the 760 Block facility and installation of the additional railcar parking area. Erosion due to wind or rain could occur if soil is left uncovered for extended periods. There exists only minor potential for the loss of top soil because the 760 Block and additional railcar parking area are primarily covered in asphalt, compact aggregate base, and gravel. A small portion (approximately 1,500 square-feet) of the northeast corner of the 760 Block is bare soil that is mostly covered in nonnative, ruderal plants. Implementation of Mitigation Measure GEO-1: Preparation & Implementation of a SWPPP (see Section ) would reduce the potential for substantial soil erosion or loss of topsoil to a level that is less than significant. Mitigation Measures Project-Level (Phase 1) No mitigation required. Program-Level (Phase 2) The following mitigation measure is required. MM GEO-1: Preparation of an Erosion Control Plan and SWPPP. All construction projects greater than one acre are required to comply with the State General Permit for Discharges of Stormwater Associated with Construction Activity (CGP) (Order No DWQ) and prepare a project specific SWPPP. Runoff of sediment and contaminants during construction activities of the proposed Plan shall be minimized through compliance with the CGP. Prior to issuance of grading permit for Phase 2 of the proposed Plan, the Applicant shall prepare all permit registration documents (PRDs), including the Notice of Intent (NOI), project-specific SWPPP, and water pollution control diagrams (WPCDs) for coverage under the NPDES General Permit for Storm Water Discharges Associated with Construction and Land Disturbance Activities ( General Permit ). The SWPPP shall comply with current SFRWQCB guidelines and incorporate acceptable BMPs for control of sediment and stabilization of erosion in the proposed Plan area. During that process the Phase 2 component sites shall undergo an evaluation of risk factors; depending on the determined risk factor for the proposed Plan, there may be additional BMP installation or sampling requirements. The Applicant shall assemble a SWPPP that summarizes the actions that shall be taken to minimize and/or reduce erosion and sedimentation impacts. The SWPPP shall adhere to the conditions meeting the requirements of the General Permit. Potential BMPs may include, but shall not be limited to: Implementation of hazardous and contaminated soil handling procedures such as placing materials into lined bins and covering soils with plastic sheeting. Designation of appropriate parking and fueling areas for all construction-related equipment. Deploying applicable sediment and runoff control measures such as coir rolls, sediment fences and geotextile filter fabric at catch basin inlets. Minimizing new land disturbance throughout the rainy season, and avoiding disturbance of sensitive areas (e.g., natural watercourses) where site improvements would not be constructed. May,

9 Providing temporary stabilization measures to disturbed soils whenever active construction is not occurring on a portion of the site Delineating a construction site perimeter to prevent disturbances to areas outside the project designated limits of the construction areas. Implementation of appropriate handling and storage procedures for waters generated during construction dewatering activities. Implementing hazardous materials storage, containment, and control measures such as secondary containment berms. Diverting upstream run on safely around and through construction areas. Hydro-seeding; Placement of erosion control measures within drainage ways and upstream of drop inlets; The temporary lining (during construction activities) of drop inlets with a geotextile filter fabric; The placement of coir rolls for erosion control; Directing subcontractors to single designation wash-out location (as opposed to allowing them to wash-out in any location they desire); The use of siltation fences; and/or The use of sediment basins and dust palliatives. Mitigation Measure: Implement MM GEO Operational-related Impacts Impact GEO-2: Operation of the proposed Project could potentially 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 (refer to Division of Mines and Geology Special Publication 42). Project-Level Impact Analysis (Phase 1) Significance before Mitigation: Less than significant. Impact Description: The nearest earthquake fault zone designated by Alquist-Priolo Act is located approximately 10 miles west of the Dow Facility. The closest fault not designated by Alquist-Priolo Act: the Clayton-Greenville Fault, is approximately 3 miles south of the Dow Facility. No known faults traverse the proposed Plan area and, as a result, the potential to expose people or structures to adverse impacts associated with surface fault rupture is less than significant. Program-Level Impact Analysis (Phase 2) Significance before Mitigation: Less than significant. May,

10 Impact Description: As discussed above, the nearest earthquake fault zone designated by Alquist-Priolo Act is located approximately 10 miles west of the Dow Facility. The closest fault not designated by Alquist-Priolo Act, the Clayton-Greenville Fault, is approximately 3 miles south of the Dow Facility. No known faults traverse the proposed Plan area and, as a result, the potential to expose people or structures to adverse impacts associated with surface fault rupture is less than significant. Mitigation Measures Project-Level (Phase 1) No mitigation required. Program-Level (Phase 2) No mitigation required. Impact GEO-3: Operation of the proposed Project could potentially expose people or structures to potential substantial adverse effects, including the risk of loss, injury, or death involving strong seismic groundshaking. Project-Level Impact Analysis (Phase 1) Impact Description: Strong seismic groundshaking could result in damage to Phase 1 Plan Components, potentially resulting in personal injury and/or the accidental release of chemicals stored or produced on the proposed Phase 1 site. Dow s Site Contingency Plan (SCP) contains provisions for emergencies, including earthquakes, that include protocols for storage of chemicals, chemical release detection methods and controls (i.e., leak monitoring devices, tank level gauges, flow totalizers, shutoff devices, gas emission monitoring devices, pressure sensors, and temperature sensors), as well as initial and follow-up actions and notification (Dow, 2015). Although potential damage from a significant seismic event is possible, adherence to current governing building codes (IBC and CBC), Dow s earthquake-related provisions of the SCP, and implementation of Mitigation Measure GEO-2, would minimize the potential for damage that could result in personal injury and/or an accidental release of chemicals from Phase 1 of the proposed Plan. Implementation of Mitigation Measure GEO-2 would reduce potential damage and seismic-related impacts associated with strong groundshaking to a level that is less than significant. Program-Level Impact Analysis (Phase 2) Impact Description: Strong seismic groundshaking could result in damage to Phase 2 Plan Components, potentially resulting in personal injury and/or the accidental release of chemicals stored or produced on the proposed Phase 2 sites (i.e., Block 640, Block 660 and Block 760 and additional railcar parking area). Detailed engineering design, calculations, specifications, and construction information would be provided to the for review and approval pursuant to the City s Building Design and Planning provisions (PMC Titles 15 and 18, respectively). The preliminary geotechnical report for the 760 Block includes recommendations for: site-specific foundation support (mat and footings); ground preparation; fill and May,

11 aggregate base placement and compaction; pavement thickness; and measures for corrosion protection (Hultgren-Tillis Engineers 2013 and 2014). Although potential damage from a significant seismic event is possible, adherence to current building codes (IBC and CBC), Dow s earthquake-related provisions of the SCP, and the implementation of Mitigation Measures GEO-3 and GEO-4, which include site-specific geotechnical recommendations for the 760 Block and the proposed railcar parking area, would minimize the potential for damage that could result in personal injury and/or an accidental release of chemicals from Phase 2 of the proposed Plan. Implementation of Mitigation Measure GEO-3 and GEO-4 would reduce potential damage and seismic-related impacts associated with strong groundshaking to a less than significant level. For the 640 and 660 Blocks implementation of Mitigation Measure GEO-2 would reduce potential damage and seismic related impacts associated with strong groundshaking to a level that is less than significant. Mitigation Measures Project-Level (Phase 1) The following mitigation measure is required. MM GEO-2: Conduct a Design-level Geotechnical Engineering Investigation. (a) A design-level geotechnical engineering investigation consistent with California geologic and engineering standards shall be conducted by the Applicant for applicable facilities by a licensed geotechnical engineer to reduce the hazards of seismic damage. The geotechnical engineer shall prepare a report that summarizes the results of a field investigation, including site inspection and soil testing, identification of potential geologic hazards (including fault rupture and severe secondary effects of earthquakes), along with design criteria and construction methods to effectively construct the proposed facilities with an acceptable level of risk with respect to earthquake, liquefaction, foundations, landscaping, dewatering (if applicable), pavement sections, and utilities. The report shall address all geologic and geotechnical factors related to the design and construction of the proposed Phase 1 Plan Components. The report shall be submitted to the Engineering Division, for review and approval. (b) Appropriate seismic design provisions shall be implemented with project design and construction in accordance with current governing building codes. Mitigation Measure: Implement MM GEO-2. Program-Level (Phase 2) The following mitigation measures are required. MM GEO-3: Compliance with Geotechnical Investigation Recommendations. The Applicant shall implement applicable recommendations of the site specific geotechnical studies prepared by Hultgren-Tillis Engineers for the 760 Block (Hultgren-Tillis Engineers 2013 and 2014) to the final design. A site specific geotechnical investigation shall also be completed for all of the proposed Phase 2 Plan Components and its recommendations shall be applied to the final design of each component. All design plans will be stamped by a licensed architect/engineer. The City will review all building plans (and/or have outside plan check) where all building and engineering work require approval. For the 760 Block, the May,

12 recommendations shall include: ground acceleration parameters for seismic design; foundation support (mat and footings) for anticipated settlements and bearing and lateral earth pressures; ground preparation; fill and aggregate base placement and compaction; pavement thickness; and recommendations for corrosion protection. The specific measures shall be selected during final design and are likely to include one or more of the following: Placing a layer of compacted, select, 12 inch thick fill beneath and 5 feet beyond the foundations; Providing additional steel reinforcement in concrete slabs; and/or Treating the expansive soil under proposed concrete slabs with lime. MM GEO-4: Preparation of a Site-Specific Geotechnical Investigation for the Proposed Additional Railcar Parking Area. Prior to the City s approval of Improvement Plans and issuance of grading permits for the proposed Plan, the Applicant shall submit to the Engineering Division, for review and approval, a design level geotechnical engineering report produced by a California Registered Civil Engineer or Geotechnical Engineer. The report shall include the recommendations in the reports entitled Preliminary Geotechnical Design Recommendations and Additional Geotechnical Exploration (Hultgren-Tillis Engineers, 2013, 2014). The design level report shall address, at a minimum, the following: Compaction specifications for onsite soils; Road and pavement design; Structural foundations, including retaining wall design (if applicable); Grading practices; Erosion/winterization; and Expansive/unstable soils. The Applicant shall provide for engineering inspection and certification, that earthwork has been performed in conformity with recommendations contained in the geotechnical engineering report. Proof that earthwork has been performed in accordance with the recommendations of the design level geotechnical report shall be provided to the City of Pittsburg Engineering Division. Mitigation Measure: Implement MM GEO-3 and GEO-4. Impact (GEO)-4: Operation of the proposed Project could potentially expose people or structures to potential substantial adverse effects, including the risk of loss, injury, or death involving seismicrelated ground failure, including liquefaction. Project-Level Impact Analysis (Phase 1) Impact Description: Strong seismic groundshaking could expose people or structures to potential substantial adverse effects, including the risk of loss, injury, or death involving seismic related ground failure, including May,

13 liquefaction. Liquefaction hazard in the ranges from very low to very high. The City of Pittsburg has identified some coastal areas, including the Dow Facility, as having high liquefaction risk. Implementation of MM GEO-2 would reduce potential damage and seismic-related impacts associated with strong groundshaking and seismic related ground failure to a level that is less than significant. Program-Level Impact Analysis (Phase 2) Impact Description: The Hultgren-Tillis Engineers geotechnical study for the 760 Block included an evaluation of the liquefaction potential of the 760 Block site. The liquefaction potential was determined to be low, overall, but with some localized liquefaction potential in a sandy layer that appears to be discontinuous (Hultgren-Tillis Engineers 2013 and 2014). ABAG also identifies the 760 Block as having a low potential for liquefaction (ABAG 2015). The geotechnical report also stated that, although further analysis of liquefaction potential is needed, a mat foundation at the process area of the 760 Block would perform satisfactorily during an earthquake. The proposed additional railcar parking area was identified as having a high risk for liquefaction (Hultgren- Tillis Engineers 2014). A site specific geotechnical report for the proposed additional railcar parking area shall be conducted as required by Mitigation Measure GEO-4. The has identified some coastal areas, including the Dow Facility, as having high liquefaction risk. Therefore, a site specific geotechnical report for the 640 and 660 Blocks shall be conducted as required by Mitigation Measure GEO-2. Phase 2 of the proposed Modernization Plan would be designed and constructed in accordance with the current building codes (IBC and CBC). With building code compliance and implementation of MM GEO-3 and MM GEO-4, risks associated with the potential for liquefaction would be reduced to a level that is less than significant. Mitigation Measures Project-Level (Phase 1) Mitigation Measure: Implement MM GEO-2. Program-Level (Phase 2) Mitigation Measure: Implement MM GEO-2, MM GEO-3, and MM GEO-4. Impact GEO-5: Operation of the proposed Project could potentially 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 onsite or offsite landslide, lateral spreading, subsidence, liquefaction, or collapse. Project-Level Impact Analysis (Phase 1) May,

14 Impact Description: The 540 Block site could be located on a geologic unit or soil that is unstable, or that would become unstable as a result of the implementation of Phase 1 of the proposed Plan. Landslide potential is not discussed because it was determined to have no impact in the Initial Study (see Appendix B). Refer to Impact GEO-4, above, for discussion relating to liquefaction. Lateral spreading could result from the liquefaction of soil after a seismic event. However, implementation of MM GEO-2 would reduce potential damage to Phase 1 Plan Components related to Lateral spreading to a level that is less than significant. Program-Level Impact Analysis (Phase 2) Impact Description: Landslide potential is not discussed because it was determined to have no impact in the Initial Study (see Appendix B). Refer to Impact GEO-4, above, for discussion relating to liquefaction. Lateral spreading can result from the liquefaction of soil after a seismic event; however, with the exception of the proposed additional railcar parking area, the site has been determined to have low liquefaction potential (Hultgren-Tillis Engineers 2013 and 2014; ABAG 2015). Lateral spreading could occur in areas immediately adjacent to the Suisun Bay due to high liquefaction potential in these areas. However, it is not expected to impact the proposed Plan due to the setback distances from the shoreline. Soil that is soft or loose could settle due to the additional weight of the proposed buildings and structures; however, implementation of MM GEO- 2, MM GEO-3 and MM GEO-4 would reduce the potential for excessive settlement to a level that is less than significant. Mitigation Measures Project-Level (Phase 1) Mitigation Measure: Implement MM GEO-2. Program-Level (Phase 2) Mitigation Measure: Implement MM GEO-2, MM GEO-3, and MM GEO-4. Impact GEO-6: Operation of the proposed Project could potentially 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. Project-Level Impact Analysis (Phase 1) Impact Description: The 540 Block site could potentially be underlain with expansive soils, which can shrink or swell as a result of moisture changes. This expansion or contraction of underlying soils can cause heaving and/or cracking of slabs on grade, pavements, railways, and structures on shallow foundations such as the proposed office and control building, parking area, electrical substation, and above grade piping supports. However, implementation of MM GEO-2 would reduce potential damage to Phase 1 Plan Components related to expansive soils to a level that is less than significant. May,

15 Program-Level Impact Analysis (Phase 2) Impact Description: Near surface soil underlying the proposed Phase 2 sites are of various types and has low to high expansion potential (Hultgren-Tillis Engineers 2013, 2014). Changes in moisture content can cause differential movement within the expansive soil that can cause cracking, uneven surfaces and tripping hazards on concrete slabs, and could affect foundations. MM GEO-3 and MM GEO-4 include measures to reduce the impact of expansive soil as identified in the geotechnical report. Implementation of MM GEO-3 and MM GEO-4 shall reduce the impact to a level that is less than significant. Spills of hazardous materials during storage that could result from expansive soils is discussed in Chapter 9.0, Hazards and Hazardous Materials. Dow s SCP contains provisions for emergencies, including chemical spills, that include protocols for storage of chemicals, chemical release detection methods and controls (i.e., leak monitoring devices, tank level gauges, flow totalizers, shutoff devices, gas emission monitoring devices, pressure sensors, and temperature sensors), and initial and follow up actions and notification. Compliance with current building codes and implementation of MM GEO-3 and MM GEO-4 would reduce the potential impacts of expansive soils on the proposed structures. In addition, the Phase 2 Plan Components do not include construction of residential housing or commercial development that would house or serve large populations on a daily basis. During operations, the risks of exposure of human life to hazards related to expansive soils is considered minor because the proposed Phase 2 sites are located in a heavily industrial area, the number employees at the site would be minimal, and the buildings and structures that employees would work in and around would comply with CBC regulations. Therefore, the potential impact of expansive soils on life and property is anticipated to be less than significant. Mitigation Measures Project-Level (Phase 1) Mitigation Measure: Implement MM GEO-2. Program-Level (Phase 2) Mitigation Measure: Implement MM GEO-3 and MM GEO-4. May,

16 Vaca fault zone (Montezuma Hills fault) Kirby Hills fault Rio Vista fault m cra Sa Suisun Bay Pittsburg-Kirby Hills fault 4 «! ( to en Ri r ve 160 «Pittsburg Pittsburg Dow Facility Antioch! ( Antioch Antioch fault Concord fault, Ygnacio Valley section Fault Line*1 Pittsburg-Kirby Hills Fault2 Fault Traces*3 Well-located Concealed by Younger Rocks, Lakes, or Bays Sources: 1 U.S. Geological Survey and California Geological Survey, 2006, Quaternary fault and fold database for the United States, accessed 12/16/2015, from USGS web site: http//earthquakes.usgs.gov/regional/qfaults/ 2 Digitized from Figure in the Trans Bay Cable Project Draft EIR (URS, 2006) 3 Digitized off the 2010 Fault Activity Map of California, California Geological Survey, accessed 12/23/2015, from web site: Basemap Source: ESRI World Imagery, Image Dated 6/12/2014 \\galt\proj\dow\664227\mapfiles\faults_ mxd 0 $ 1 Miles 2 NAPA *Note: Unlabeled lines indicate unnamed faults. SONOMA Dow Facility Greenville fault zone, Clayton section (Clayton fault) MARIN LEGEND 4 «SOLANO Site Location ( Vallejo! ( Pittsburg! CONTRA COSTA! ( San Francisco 10 Miles FIGURE 7-1 Project Vicinity Faults Dow Pittsburg Modernization Plan ALAMEDA 17-16