| III. GEOLOGICAL PROBLEMS | ||||
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| d) Seiche, tsunami, or volcanic hazard? | ||||
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| g) Subsidence of the land? | ||||
| h) Expansive soils? |  |
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Explanation:
a) Fault rupture: Despite engineering measures incorporated by SFPP into the project design, pipeline rupture could be caused by a major earthquake. This is a potentially significant impact which needs to be evaluated in an EIR. As described in PEA Section 3.8.1 (page 3-76), the Newport-Inglewood fault zone traverses the southwestern flanks of the Dominguez Hills (immediately adjacent to the western portion of the pipeline route). There are designated Alquist-Priolo Earthquake Hazard Special Study Zones associated with the Newport-Inglewood fault in the area just to the north of the Dominguez Hills, and to the southeast of the pipeline route (the Cherry Hill segment of the fault). There are no special study zones designated in the area between these segments where the proposed pipeline would be located. However, fault rupture in this area is still considered to be a significant potential hazard (PEA, page 3-81). In the eastern portion of the pipeline route, the pipeline may be located over or near the Peralta Hills/Norwalk fault and the Compton/Los Alamitos/Pelican Hill fault system. These faults pose less of a risk of pipeline rupture due to their depth and/or location.
Pipelines can be designed to survive some degree of fault movement, soil liquefaction, or strong ground shaking resulting from an earthquake. The proposed project includes a comprehensive measure, G-1 (PEA, page 3-83) where certain engineering studies and design features would be used to minimize the potential for damage to the pipe. However, if a pipeline crosses a fault that moves in a large earthquake or if the pipe is located within an area that experiences severe lateral spreading, engineering measures cannot prevent pipe rupture. In these cases, block valves can be installed to reduce the size of a resulting spill, but they will not prevent a spill from occurring.
b) Strong ground shaking: Impacts to above ground structures are expected to be less than significant because building codes are generally sufficient to prevent damage to above-ground facilities, despite the proximity of the proposed project to the faults as discussed above and to other larger faults in the region. SFPP will construct modifications to its above ground facilities (i.e., the pump stations at Watson, Norwalk, Industry, and Colton) in accordance with the Uniform Building Code’s earthquake design criteria for Seismic Zone 4 as required for conformity with city and county building permits. Strong ground shaking is unlikely to effect the pipeline itself.
c) Seismic ground failure (including liquefaction): Impacts in this area are expected to be less than significant due to SFPP’s commitment to perform geotechnical studies prior to construction. According to the PEA (page 3-81), the soils along the pipeline route have a very low to moderate susceptibility to liquefaction. The area with highest susceptibility is west of Alameda Street and east of Woodruff Avenue at the western end of the route.
d) Seiche, tsumani, or volcanic hazard: The proposed project is not located in an area where these potential hazards exist, therefore no impact is expected.
e) Landslides or mudflows: Due to the essentially flat terrain along the proposed project route, landslides or mudflows are very unlikely to occur, therefore no impact is expected.
f) Erosion, unstable soil conditions: The potential for erosion and sedimentation, as well as trench safety issues, is a potentially significant impact which needs to be evaluated in the EIR. Construction of the proposed project will cross Compton Creek by means of an open cut trench, which can result in erosion of the creek bottom or increased sedimentation downstream for a short period of time. In addition, pipeline construction will occur in a trench that passes through a variety of soil types.
g) Subsidence: No impact related to subsidence is anticipated. While portions of this project are in an area that has experienced subsidence in the past (the ground surface subsided as a result of the large volumes of oil produced) subsidence will not be caused by this project, nor will the project be affected by subsidence occurring on a regional level.
h) Expansive soils: Expansive soils are a potentially significant impact and need to be evaluated in the EIR because such soils could cause damage at pump stations if they are not designed to accommodate potential expansion. These soils are not a concern for the safety of the pipeline itself because soils expand or contract in a similar way around the pipe and no differential movement is expected.
| IV. WATER | ||||
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| a) Changes in absorption rates, drainage patterns, or the rate and amount of surface runoff? |
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c) Discharge into surface water or other alteration of surface water quality (e.g. temperature, dissolved oxygen or turbidity)? |
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| e) Changes in currents, or the course or direction of water movements? | |
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| f) Change in the quantity of ground waters, either through direct additions or withdrawals, or through interception of an aquifer by cuts or excavations or through substantial loss of ground water recharge capability? | |
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| g) Altered direction or rate of flow of ground water? | |
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| h) Impacts to ground water quality? | |
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| i) Substantial reduction in the amount of ground water otherwise available for public water supplies? | |
Explanation:
a) Changes in drainage or absorption: The proposed action would take place almost entirely in paved streets; therefore, no impact would result to drainage or absorption.
b) Exposure of people to flooding/hazards: The proposed action would have no effect on flooding because the pipeline would be buried in city streets or beneath the depth of scour at river crossings.
c) Discharge into surface water: The proposed project could result in potentially significant impacts on surface water as a result of both construction and operation (upset). Pipeline construction could affect surface water quality for a short period of time as a result of sedimentation, or possibly from accidental construction equipment leakage. Section 3.4 of the PEA addresses Hydrology. These impacts need to be evaluated in the EIR.
Operational impacts such as a pipeline leak or rupture that occurred directly at a water crossing (e.g., if the pipeline were to break at the bridge crossing over the San Gabriel River), or if it occurred in a street and the product flowed into storm drains and then into surface waters, can be potentially significant. Even with a computerized leak detection system, assuming that valves are closed quickly, the petroleum products between any two valves could potentially flow into surface waters before it could be removed from the pipe. Pipeline design features (i.e., placement of block valves on either side of river crossings, as proposed by SFPP) can minimize the amount of an oil spill and reduce the likelihood of a spill (i.e., frequent pipe inspections); however they cannot prevent a spill from occurring.
d) Change in amount of surface water, and e) Change in water movements: The proposed action would have no effect on quantity or movement of surface water because the pipeline would be buried in city streets or beneath the depth of scour at river crossings.
f) Change in quantity or availability of ground water, and g) Altered direction of ground water flow: The proposed pipeline will be buried approximately 7 feet below ground surface, and will have no effect on quantity or movement of ground water.
h) Impacts to ground water quality: The proposed project can have a significant impact on ground water quality. Ground water basins and aquifers are described in Section 3.4.11 of the PEA. Ground water in shallow aquifers is generally between 50 and 150 feet below surface, but perched groundwater in some project areas is as shallow as 15 feet below surface. Construction of the pipeline is not expected to impact ground water quality. However, if a pipeline rupture occurs during operation in an area where ground water is very shallow and various other conditions are present (variables include soil moisture content, soil permeability, etc.), there is a possibility that ground water could be contaminated. Even with a computerized leak detection system, assuming that valves are closed quickly, the petroleum products between any two valves could potentially flow into ground water before it can be removed from the pipe. Project design measures (i.e., placement of block valves) can minimize the amount of an oil spill and reduce the likelihood of a spill (i.e., frequent pipe inspections); however they cannot prevent a spill from occurring.