GEOLOGY AND SOILS MITIGATION MEASURES
Mitigation Measure G-1: Geotechnical investigations shall be performed on the landslides at approximately EMP 16.3 to 16.85, EMP 26.8, EMP 28 and on potentially unstable slopes at EMP 37, EMP 46.4, EMP 50.6 and EMP 53.5 to 54.2 to develop slope stabilization criteria. In addition, steep slopes along the remaining section of the alignment through the Ridge Basin should be evaluated to determine whether detailed geotechnical investigations should be performed. The geotechnical reports shall be submitted to the permitting jurisdictions for review and approval of the slope stabilization measures or pipeline realignments included in the project design. Slope stabilization measures may include soil improvements, buttressing of the slopes, or compaction of trench backfill. In addition, erosion control measures, such as water bars, trench dams and revegetation identified in the Applicant's Erosion Control, Landscaping and Revegetation Plan shall be included in the project design.
Impact: Reactivation of existing landslides in Grapevine Canyon and near Tejon Pass could cause pipeline rupture (Class I); Potential failure of steep slopes in the Ridge Basin could cause pipeline rupture (Class II)
Performance Criteria, Violation Level, and Timing:
PC1 PPSI has geotechnical studies, including, air photo analyses, geologic mapping, and/or subsurface exploration performed for the active landslides located approximately EMP 16.3 to 16.85, EMP 26.8, and EMP 28 to define their dimensions and evaluate their stability. The geotechnical reports should include recommendations for mitigation of the landslide crossings, e.g. stabilization of the slopes, removal of the slide, re-routing of the alignment, or the use and location of block valves to minimize any oil spills created by renewed movement. (Level 1) - Prior to construction
PC2 PPSI has geotechnical studies, including air photo analyses and geologic mapping performed for potentially unstable slopes along the remainder of the alignment, including slopes at approximately EMP 37, EMP 46.4, EMP 50.6 and EMP 53.5 to 54.2 that were identified as potentially unstable by Harding Lawson Associates (1991), to determine whether active landslides are present and develops site specific erosion control, landscaping, and revegetation plans for the potentially unstable slopes that are not failing. (Level 1) - Prior to construction
PC3 If active landslides are identified by the geologic mapping and air photo analyses, these landslide crossings become Class I impacts and they are subject to the detailed geotechnical studies outlined above. (Level 2) - Prior to construction
Effectiveness Criteria: The reports' design recommendations should be reviewed by the responsible agency or their representatives; existing landslides in Grapevine Canyon and near Tejon Pass are not reactivated.
Effectiveness Timing: Design recommendations reviewed prior to construction; landslide activity monitored during lifetime of pipeline.
Mitigation Measure G-2: Prior to the construction of the pipeline, the Applicant shall conduct geotechnical studies at all active fault crossings to define the fault plane orientation and direction of anticipated offset and to refine fault crossing design parameters. These geotechnical reports shall be submitted to each permitting jurisdiction for review and approval of the fault crossing design. The geotechnical report shall review and evaluate the location of block and check valves included in the Proposed Project design, and shall review, evaluate, and recommend other appropriate engineering measures (i.e., use of engineered backfills, expansion loops, and thicker-walled pipe).
Impact: Potential pipeline rupture at active fault crossings (Class I). Kern County faults: White Wolf, Wheeler Ridge, Plieto, Garlock; LA County faults: San Andreas, San Gabriel, Santa Susana, San Fernando, Verdugo, Hollywood, Echo Park, Newport-Inglewood.
Performance Criteria, Violation Level, and Timing:
PC1 PPSI conducts geotechnical studies, including literature review, air photo analyses, and geologic mapping at all active fault crossings to define the location and orientation of the fault plane, the magnitude and direction of anticipated offsets, the angle at which the proposed alignment crosses the fault plane and the anticipated stresses on the pipeline (i.e. extensional or compressional). The geotechnical report should include or be accompanied by a design report that includes details regarding the applicant proposed mitigation at each fault crossing, e.g. the location of block valves, the location and length of ductile steel pipe proposed, design of the trench excavation, and identification of areas where the use of low shear strength backfill is proposed. (Level 2) - Prior to construction.
Effectiveness Criteria: Fault crossing design recommendations should be reviewed by the responsible agency or their representatives; no pipeline rupture after an earthquake.
Effectiveness Timing: Prior to construction; monitor for rupture after an earthquake for lifetime of project.
Mitigation Measure G-3: During final design of the Proposed Project geotechnical investigations shall be conducted in the areas classified as being potentially liquefiable. The geotechnical reports shall be submitted to each permitting jurisdiction for review and approval of the recommended design criteria. Appropriate site-specific mitigation is dependent on site conditions, which shall be identified by the geotechnical investigation.
Impact: Liquefaction could cause pipeline rupture (Class II)
Performance Criteria, Violation Level, and Timing:
PC1 PPSI performs geotechnical studies in areas identified in the EIR/EIS as potentially liquefiable. At a minimum, these studies should include a literature review and geologic reconnaissance. The geotechnical report should also include recommendations for mitigation of areas of potentially liquefiable soils, e.g. shallow burial, use of thick walled, ductile, steel pipe, burial beneath the zone of liquefaction, or relocation of the alignment. The selected, site specific mitigation should be supported by existing data or new subsurface exploration. (Level 2) - Prior to construction.
Effectiveness Criteria: The report's design recommendations should be reviewed and approved by the responsible agency or their representatives; no pipeline ruptures in areas classified as potentially liquefiable.
Effectiveness Timing: Prior to construction; monitor for lifetime of project.
Mitigation Measure G-4: The Erosion Control, Revegetation and Landscaping Plan shall be submitted to each permitting jurisdiction for review and approval of the recommended erosion control criteria.
Impact: Pipeline construction could cause accelerated erosion on natural slopes in the Ridge Basin and Angeles National Forest (Class II)
Performance Criteria, Violation Level, and Timing:
PC1 PPSI submits ECRLP that describes mitigation to be used on potentially erodible slopes, e.g. water bars, trench plugs, compaction of trench backfill, stockpiling and reuse of top soil, and revegetation; develop criteria for their implementation, and outline a maintenance program. Examples of implementation criteria could include a minimum vertical spacing for trench plugs; selection of plants used for revegetation based on soil types, ecosystems, and slope gradients; or minimum slope gradients requiring compaction of trench backfill. (Level 1) - Prior to construction
PC2 PPSI implements ECRLP. (Level 1) - Prior to, during, and post-construction.
Effectiveness Criteria: Erosion control measures should be consistent with county ordinances and accepted standards of practice. The erosion control plan should be reviewed and approved by the responsible agencies or their representatives. No accelerated erosion on natural slopes in the Ridge Basin and Angeles National Forest.
Effectiveness Timing: Prior to construction. Monitor until revegetation on natural slopes complete.
Mitigation Measure G-5: Geotechnical studies shall be performed at the pump station and pressure reduction station sites, and the potential for expansive soils shall be specifically investigated. If expansive soils are identified at any of the sites, they shall be over-excavated and replaced with compacted backfill.
Impact: Potential expansive soils could damage facilities at Emidio, Grapevine and Whitaker Stations (Class II)
Performance Criteria, Violation Level, and Timing:
PC1 PPSI conducts geotechnical studies, including site reconnaissance, subsurface exploration, and laboratory testing at the Grapevine, Emidio, and Whitaker station sites to evaluate the potential for expansive soils. Where expansive soils are present, the geotechnical report should include recommendations for mitigation of this impact, e.g. over-excavation and replacement with engineered fill. (Level 1) - Prior to construction.
Effectiveness Criteria: Design recommendations for areas of expansive soils should be reviewed and approved by the responsible agency or their representatives. No impacts to stations due to construction on expansive soils.
Effectiveness Timing: Prior to obtaining building permits. Monitor for impacts after construction.
GEOLOGY AND SOILS APPLICANT PROPOSED MEASURES
Applicant Proposed Measure G-6**: Use of high-ductility steel pipe in fault and landslide zones
Impact: See Mitigation Measure G-2
Performance Criteria, Violation Level, and Timing: See Mitigation Measure G-2
Effectiveness Criteria: See Mitigation Measure G-2
Effectiveness Timing: See Mitigation Measure G-2
Applicant Proposed Measure G-7**: Placement of block and check valves around fault and landslide zones.
Impact: See Mitigation Measure G-2
Performance Criteria, Violation Level, and Timing: See Mitigation Measure G-2
Effectiveness Criteria: See Mitigation Measure G-2
Effectiveness Timing: See Mitigation Measure G-2