HYDROLOGY MITIGATION MEASURES

Mitigation Measure H-1: To ensure appropriate protection against flooding, the Applicant shall incorporate the following specific measures into the Erosion Control, Revegetation, and Landscaping Plan (see also Mitigation Measures B-V-3, B-V-4, B-V-5, and B-V-7). The Plan shall be submitted to the CPUC, ANF and appropriate water management agencies for review and approval prior to initiation of construction. The Plan shall include the following:

$ Develop a construction schedule that calls for construction in stream beds to occur as quickly as is reasonably possible.

$ Excavation in stream crossings shall be limited to the pipeline right-of-way except as otherwise approved by the appropriate permitting agencies.

$ Describe specific methods for stream-bed and creek-bank protection including but not limited to, soil stabilization techniques, temporary retention basins and drainage diversion structures to reduce siltation due to runoff from areas disturbed by construction.

Impact: Flooding impacts could occur downstream of construction if the normal flow path of water is obstructed or diverted (Class I or II)

Performance Criteria, Violation Level, and Timing:

PC1 PPSI incorporates above bulleted items into ECRLP. (Level 1) - Prior to construction.

Effectiveness Criteria: Project is constructed according to mitigation measures, approved plans and schedule. Site inspections shall be conducted daily during construction. Flooding does not occur downstream from construction.

Effectiveness Timing: Construction plans shall demonstrate compliance prior to granting construction permit. Monitor for flooding after construction.

Mitigation Measure H-2: The stream channel topography, or cross section, shall not be permanently altered by the pipeline construction. Pre-construction and post-construction channel cross sections at the location of the pipeline shall be included in the construction plans which shall be approved by the CPUC, ANF, Army Corps of Engineers (ACE), CDFG, and other agencies responsible for watercourse management.

Impact: Permanent channel geometry changes, fill or bank protection could result in flooding downstream of construction (Class I or II)

Performance Criteria, Violation Level, and Timing:

PC1 PPSI provides pre-construction channel cross sections at pipeline crossings. (Level 1) - Prior to start of construction.

PC2 PPSI provides post-construction channel cross sections at pipeline crossings. (Level 1) Within 30 days of each pipeline crossing.

PC3 Pipeline construction does not permanently alter the stream channel topography or cross section. (Level 3) - During construction.

Effectiveness Criteria: Project is constructed according to approved plans. Flooding does not occur downstream of construction.

Effectiveness Timing: Monitor for flooding after construction.

Mitigation Measure H-3: The pipeline shall be located in a position that will not intercept or obstruct flow or debris from a 100-year flood on all crossings where a bridge structure is to be used. In Los Angeles County the Capital Flood discharge shall be used to estimate water surface elevations. Construction plans shall include water surface elevation as determined by site-specific engineering analysis, if accurate information is not already available from previous studies. If it is not possible to keep the pipe out of the flow path, another crossing method shall be used. Compliance with this measure shall be demonstrated in an engineering report to be reviewed and approved by the CPUC, ANF, ACE, CDFG, and other agencies responsible for watercourse management prior to approval of construction plans.

Impact: Placement of the pipeline within the flow path on a bridge structure could cause flooding of adjacent property, failure of the bridge structure or rupture of the pipeline (Class II)

Performance Criteria, Violation Level, and Timing:

PC1 PPSI submits plans prepared by a registered civil engineer showing location of pipeline on bridges (plan and profile) and 100-year or Capital Flood water surface elevation (whichever is greater) at bridges. (Level 1) - Prior to construction.

PC2 Construction plans include water surface elevation. (Level 2) - Prior to construction.

Effectiveness Criteria: Design plans must demonstrate compliance. Property adjacent to bridge structure does not flood, bridge structure does not fail, and pipeline does not rupture.

Effectiveness Timing: Monitor for flooding adjacent to bridge structure, bridge failure, and pipeline rupture after construction for lifetime of pipeline.

Mitigation Measure H-4: All permanent, above-ground structures associated with the pipeline shall be located outside of the 100-year floodplain (or Capital Floodplain in Los Angeles County if the Capital Flood discharge is greater than the 100-year discharge) as demonstrated to the CPUC, ANF, COE, or other appropriate watercourse management agencies, prior to approval of construction plans. The block valve proposed by the Applicant at approximately EMP 60.7 should be re-located to approximately EMP 61.0.

Impact: Locating structures within the floodplain could cause flow diversions, increases in flood levels and contamination of flood flows (Class II)

Performance Criteria, Violation Level, and Timing:

PC1 PPSI to submit construction plans prepared by a registered civil engineer showing location and finished grade elevation of all above-ground structures along with proof of compliance (water surface elevations, floodplain maps, etc.). (Level 1) - Prior to construction.

Effectiveness Criteria: Project is approved with appropriate floodplain certification. Flow diversion, increased flood levels and contamination of flood flows does not occur.

Effectiveness Timing: Construction plans shall demonstrate compliance prior to granting construction permit. Monitor after construction

Mitigation Measure H-5: Category 1 crossings must be adequately protected from erosion; this issue must be addressed in the ECRLP (see also Mitigation Measure H-1). A determination of the adequacy of the erosion protection at each crossing shall be made by a registered Civil Engineer with experience in erosion and erosion control. Compliance with this mitigation measure shall be demonstrated in an engineering report to be reviewed and approved by the COE, ANF, CPUC, or appropriate watercourse management agencies, prior to approval of construction plans.

Impact: Overtopping of undersized culverts could result in erosion of fill above the culvert, causing pipeline rupture (Class II)

Performance Criteria, Violation Level, and Timing:

PC1 For all Category 1 crossings, PPSI submits engineering computations showing flow discharges, culvert capacities, overflow discharges and return periods, overflow durations, probable scour depths in roadway. These estimations shall demonstrate that overtopping does not occur. (Level 1) - Prior to construction.

Effectiveness Criteria: Fill above culverts does not erode.

Effectiveness Timing: Monitor after construction,

Mitigation Measure H-6: The pipeline shall be buried at a depth not less than 4 feet below the maximum depth of scour for a 100-year 24-hour flood, or 1.3 times the same depth of scour, whichever is greater. In Los Angeles County, the Capital Flood discharge (50-year design frequency) shall be used to estimate scour. Crossings of streams upstream of and draining into water-supply reservoirs (as identified in Table C.7-2) shall use the 500-year flood as a design discharge. The scour depth shall be estimated at all crossings by a registered Civil Engineer with experience in river sediment transport, using methods acceptable to the COE, CPUC, ANF or appropriate watercourse management agency, as the sum of long-term degradation, general scour, bed forms, the low-flow channel and local scour, and taking into consideration other foreseeable or proposed projects which could influence scour depth. Properly-designed protective measures such as bed lining may be used to reduce or eliminate scour. Compliance with this mitigation measure shall be demonstrated in an engineering report to be reviewed and approved by the appropriate agencies prior to approval of construction plans.

Table C.7-2 Stream Crossings Potentially Affecting Water Supply or Water Recreation

Impact: Stream scour could result in rupture of the pipeline (Class II)

Performance Criteria, Violation Level, and Timing:

PC1 PPSI submits engineering computations prepared by a registered Civil Engineer with experience in river sediment transport for scour depth (or scour mitigation) at all crossings. Engineering computations to be site-specific and show methodology, assumptions, input data used, computer and other computation output, cross sections, stream profiles, stream plan views, photographs, construction drawings and other information as necessary. (Level 1) - Prior to construction.

Effectiveness Criteria: Pipeline is buried at the required depth and worst-case scours do not result in exposed pipe.

Effectiveness Timing: Monitor after heavy rain storms after construction for lifetime of pipeline

Mitigation Measure H-7: Category 4 crossings shall not be used in cases where the bridge piers and abutments do not provide a factor of safety at least 1.3 times the 100-year depth of scour (or the Capital Flood depth of scour, if in Los Angeles County). The scour depth shall be computed as the sum of long-term degradation, general scour, bed forms, the low-flow channel and local scour taking into consideration other foreseeable or proposed projects which could influence scour depth. Calculations shall be made by a registered Civil Engineer using methods acceptable to the agencies. Compliance with this mitigation measure shall be demonstrated in an engineering report to be reviewed and approved by the COE, ANF, CPUC, and appropriate watercourse management agencies, prior to approval of construction plans. In cases where the permitting agency determines that a Category 4 crossing is not appropriate, another crossing method acceptable to the permitting agency shall be used after assessment of potential impacts to other resources is completed.

Impact: Pier scour can undermine the bridge upon which the pipeline will rest; bridge failure could rupture the pipeline (Class II)

Performance Criteria, Violation Level, and Timing:

PC1 PPSI submits for review and approval engineering computations prepared by a registered Civil Engineer for scour depth in comparison to pier and abutment depth at bridges. Engineering computations to be site-specific and show methodology, assumptions, input data used, computer and other computation output, cross sections, stream profiles, stream plan views, photographs, construction drawings and other information as necessary. (Level 1) - Prior to construction.

Effectiveness Criteria: .Pier scour does not undermine bridge upon which pipeline rests.

Effectiveness Timing: Monitor after heavy rain storms, after construction for lifetime of pipeline.

Mitigation Measure H-8: In order to provide safety against lateral erosion from a 100-year flood, the Applicant shall implement the specific measures listed below, which shall be reviewed by a registered professional engineer with experience in river mechanics and approved by the COE, CPUC, ANF, or appropriate watercourse management agencies prior to approval of construction plans. Compliance with this measure shall be demonstrated in an engineering report to be reviewed and approved by the appropriate agencies prior to approval of construction plans. (See Figure C.7-17 for examples of specific construction techniques.)

$ The maximum depth of burial at Category 2 and 3 crossings shall extend for a sufficient distance outside the stream banks. The setback shall be determined on a case-by-case basis taking into consideration site conditions, stream morphology, erosion history, bank composition and condition, total sediment transport capacity for the entire flood, and other factors as determined appropriate by the reviewing engineer.

$ The Applicant shall monitor unlined channel banks at stream crossings and where the pipeline parallels streams (Liebre Creek, Marple Canyon, Gorman Creek, and Tecuya Creek) during the life of the project. If channel bank erosion begins to threaten the pipeline, the setback shall be increased or the river stabilized to prevent further erosion. Permitting agencies may require that pipeline operations must cease in the event of a flood-related emergency which results in erosion threatening the pipeline, or in the event that preventive measures required by this mitigation measure are not implemented in a timely manner, as determined according to circumstance and by the permitting agency.

$ Setbacks and burial depth are preferred methods of erosion protection. In cases where, burial depth or monitoring are considered inappropriate by the reviewing engineer and the monitoring agencies, the Applicant shall install bank protection to prevent erosion. The bank protection must extend a sufficient distance upstream to prevent being cut behind by upstream erosion. Bank protection plans must be reviewed and approved by the appropriate permitting agency prior to construction. Long-term maintenance of the bank protection shall be ensured through dedication to a public agency, posting of maintenance bonds or another method acceptable to the permitting agency prior to approval of construction plans.

Impact: Lateral erosion and headcut could cause pipeline rupture (Class II)

Performance Criteria, Violation Level, and Timing:

PC1 PPSI submits proposed setbacks for each Category 2 and 3 crossing. The each proposed setback will include stream geomorphology evaluations, historical trends, cross sections, profiles, photographs, sediment transport analysis, maps, scour calculations, bank protection design computations, construction drawings and other information as appropriate to each site. (Level 1) - Prior to construction.

PC2 PPSI ensures long-term maintenance of the bank protection through dedication to a public agency, posting of maintenance bonds or another method acceptable to the permitting agency. (Level 1) - Prior to construction.

Effectiveness Criteria: Lateral erosion and headcutting do not occur.

Effectiveness Timing: After heavy rain storms after construction for lifetime of pipeline.

Mitigation Measure H-9: All pipeline crossings potentially subject to headcut erosion, as listed in Table C.7-4 and otherwise identified by the design engineer prior to design approval, shall be stabilized by stream grade-control or drop structures to prevent the headcut from reaching the pipeline. Alternatively, the pipeline could be located below the anticipated maximum depth of headcut plus local (drop) scour and long-term degradation. Grade stabilization structures shall be designed by a registered professional engineer with expertise in the field of surface water drainage, erosion and sedimentation. Grade stabilization structures and headcut analysis shall be reviewed and approved by the CPUC, ANF, COE, or authority with jurisdiction over surface water drainage.

Table C.7-4 Summary of Crossing Impacts of Proposed Project

L.A. = Los Angeles ^a Los Angeles County Capital Discharge

Performance Criteria, Violation Level, and Timing:

PC1 PPSI stabilizes all pipeline crossings potentially subject to headcut erosion, as listed in Table C.7-4 and otherwise identified by the design engineer prior to design approval by stream grade-control or drop structures to prevent the headcut from reaching the pipeline or locates pipeline below the anticipated maximum depth of headcut plus local (drop) scour and long-term degradation. (Level 2) - Prior to construction

PC2 Grade stabilization structure designed by a registered Professional Engineer with expertise in the field of surface water drainage, erosion and sedimentation. (Level 2) - Prior to construction

PC3 Grade stabilization structures and headcut analysis reviewed and approved by the CPUC, ANF, COE, or authority with jurisdiction over surface water drainage. (Level 1) - Prior to construction

Effectiveness Criteria: Lateral erosion and headcutting do not occur.

Effectiveness Timing: After heavy rain storms after construction for lifetime of pipeline.

Mitigation Measure H-10: Deleted; see SS-12

Mitigation Measure H-11: In preparation of the Oil Spill Contingency Plan (see C.13, System Safety Mitigation Measure SS-13), the Applicant shall prepare a table listing each stream crossed by the pipeline where spilled oil could flow into a water supply reservoir (Castaic and Pyramid Lakes). For each stream crossing, the table shall list the maximum volume of oil that could spill if a rupture occurred at that location, and the estimated time it would take for the oil to reach the reservoir, including times for both dry and peak-flow conditions. That information shall be used by the Applicant, the ANF, and the water districts to evaluate and develop other means of protecting these reservoirs. This evaluation shall include consideration of pipeline engineering features that could reduce the likelihood of pipeline failure [e.g., use of thicker-walled pipe (see Mitigation Measure SS-10A), use of concrete coating to reduce likelihood of third-party damage to the pipeline (see Mitigation Measure H-12)] or reduce the likelihood that an oil spill could enter a stream channel (e.g., install the pipeline within a concrete-lined channel in critical areas) or a more intensive maintenance and monitoring program in certain areas.

In addition, the Applicant shall consult with the appropriate water districts regarding purchase of proper emergency response equipment and to develop emergency response procedures and appropriate coordination required to respond to a potential oil spill from the Proposed Project into watercourses leading to the water supply. Specifications for types and quantities of equipment shall be developed by the Applicant in cooperation with the water districts; this equipment shall also be reviewed and approved by the agencies responsible for oil spill response.

Impact: Oil spill during pipeline operation could reach water supply reservoirs(Class I)

Performance Criteria, Violation Level, and Timing:

PC1 PPSI provides the information requested in this mitigation measure, plus engineering computations supporting travel time estimates. (Level 1) - Prior to pipeline operation.

PC2 PPSI consults with the appropriate water districts regarding purchase of proper emergency response equipment and develops emergency response procedures and appropriate coordination required to respond to a potential oil spill from the pipeline into watercourses leading to the water supply. (Level 1) - Prior to pipeline operation.

Effectiveness Criteria: Oil from a spill does not reach water supply reservoirs.

Effectiveness Timing: After an oil spill.

Mitigation Measure H-12: The Applicant shall develop measures, in coordination with the CPUC, ANF, CDFG, and RWQCB, that would reduce the likelihood of pipeline rupture in areas of shallow ground water. The pipeline shall be designed to prevent uplift by the use of concrete coating (or other measures, if determined appropriate). Such coating would also minimize the possibility that a third-party could damage the pipeline.

Impact: Burial of pipeline below ground water in local areas of shallow ground water could result in uplifting forces which could rupture the pipeline (Class II)

Performance Criteria, Violation Level, and Timing:

PC1 PPSI, in coordination with CPUC, ANF, CDFG and RWQCB, develops pipeline coating and/or other measures that reduce the likelihood of pipeline rupture in areas of shallow ground water. (Level 2) - Prior to construction

PC2 PPSI designs pipeline to prevent uplift by the use of concrete coating (or other measures, if determined appropriate). (Level 2) - Prior to construction

Effectiveness Criteria: Pipeline buried such that it is not affected by uplifting forces.

Effectiveness Timing: During lifetime of pipeline.

Mitigation Measure H-13: The proposed pipeline shall be located at least 200 feet from any existing water well. Depending on the geology of any particular well location, a greater separation or special pipeline design features might be required. The Applicant shall coordinate with the State Department of Health Services to locate these wells and develop specific design requirements prior to construction.

Impact: Location of pipeline within 200-feet of an existing water well could risk water contamination (Class II)

Performance Criteria, Violation Level, and Timing:

PC1 PPSI to locate pipeline at least 200 feet away from any existing water well. (Level 2) - Prior to construction

PC2 PPSI and SDHS to develop specific design requirements. (Level 1) - Prior to construction

Effectiveness Criteria: Water wells within 200 feet of pipeline (at time of pipeline construction) are not contaminated.

Effectiveness Timing: During lifetime of pipeline.

Mitigation Measure H-14: Deleted

Mitigation Measure H-15*: Deleted, not applicable to current route

Mitigation Measure H-16*: Deleted, not applicable to current route

HYDROLOGY APPLICANT PROPOSED MEASURES

Applicant Proposed Measure H-17**: Streams would be crossed during the normal period of low stream flow (May to October) or would be crossed by "in the dry" construction techniques. No work would be done in a flowing portion of a stream channel. The "in the dry" construction techniques would divert the stream flow into one channel on one side of the streambed to provide a construction zone free of surface flow on the other side of the stream. (Depending on depth to ground water, the pipeline trench may fill with ground water seepage). This technique is also called "fluming". The stream would be returned to its original configuration, substrate replaced, banks stabilized, and revegetated as appropriate.

Impact: See Mitigation Measure B-AQ-2

Performance Criteria, Violation Level, and Timing: See Mitigation Measure B-AQ-2

Effectiveness Criteria: See Mitigation Measure B-AQ-2

Effectiveness Timing: See Mitigation Measure B-AQ-2

Applicant Proposed Measure H-18** Any small drainage ways or gullies that need to be frequently crossed by construction traffic would be protected by temporary access installations, consisting of culverts and temporary access fords.

Impact: See Mitigation Measure B-AQ-4

Performance Criteria, Violation Level, and Timing: See Mitigation Measure B-AQ-4

Effectiveness Criteria: See Mitigation Measure B-AQ-4

Effectiveness Timing: See Mitigation Measure B-AQ-4

Applicant Proposed Measure H-19**: Frequently-used construction entrances from paved streets would be stabilized if expected to be in use for more than a week. Such entrances are intended to inhibit sheet flow and the tracking of sediments into streets and storm drains.

Impact: Sheet flow and sediments impacting streets and storm drains

Performance Criteria, Violation Level, and Timing:

PC1 Construction entrances from paved streets are stabilized if expected to be in use for more than one week (Level 1 - Prior to, during and post-construction

Effectiveness Criteria: Streets and storm drains are not impacted and no complaints are received

Effectiveness Timing: Prior to, during and post-construction

Applicant Proposed Measure H-20**: During construction in steep terrain, erosion-control structures, including water bars, diversion channels, and terraces, would be employed to reduce erosion and runoff from the ROW and adjacent areas.

Impact: See Mitigation Measure B-V-3

Performance Criteria, Violation Level, and Timing: See Mitigation Measure B-V-3

Effectiveness Criteria: See Mitigation Measure B-V-3

Effectiveness Timing: See Mitigation Measure B-V-3

Applicant Proposed Measure H-21**: At open-cut stream crossings, a trench would be excavated to a depth four feet below calculated 100-year scour depths or 1.3 times the scour depth. (Scour depth is maximum the predicted depth to which a storm with a recurrence interval of 100 years would create). At most well-developed creeks, streams and rivers, the pipeline would be buried by trenching. The pipeline would be buried at a depth of four feet below the probable scour depth of the 100-year flood event calculated at that particular crossing

Impact: See Mitigation Measure H-6

Performance Criteria, Violation Level, and Timing: See Mitigation Measure H-6

Effectiveness Criteria: See Mitigation Measure H-6

Effectiveness Timing: See Mitigation Measure H-6

Applicant Proposed Measure H-22**: PPSI has prepared an Erosion Control, Revegetation, and Landscaping Plan (ECRLP) which provides a summary of the methods recommended for impact-reduction. PPSI's goals for guiding the selection of restoration procedures include:

- Disturbed areas would be restored as closely as practical to their original (before construction) conditions.

- PPSI would work closely with the appropriate public agencies, especially on ANF land, to develop an adequate restoration plan; all appropriate regulations and guidelines would be followed. Privately owned land would be restored to its condition prior to construction.

- Revegetation and erosion-control measures, including watershed stabilization, would be implemented prior to the succeeding winter season.

- The program of maintenance would determine the techniques and extent of restoration. A maintenance program would be implemented where necessary to ensure restoration of sensitive resources.

The restoration process would typically follow these steps: removal of debris, construction signs, surplus material and equipment; surface contouring; water control structures; cultivation, mulching, application of soil amendments; and, where applicable, replanting. In all land types, restoration would follow pipeline construction specifications, beginning with the disposal of debris and the restoration of normal contour and surface soils. Surface contouring and water control structures would be used as diversions to concentrate and/or channel surface-water flow and prevent soil erosion.

Impact: Flood impacts could occur downstream of construction

Performance Criteria, Violation Level, and Timing:

PC1 Disturbed areas restored as closely as practical to their original (before construction) conditions. (Level 2) - During construction

PC2 PPSI works closely with the appropriate public agencies, especially on ANF land, to develop an adequate restoration plan and all appropriate regulations and guidelines.(Level 2) - Prior to construction

PC3 Privately owned land restored to its before construction condition. (Level 2) - During construction

PC4 Revegetation and permanent erosion-control measures, including watershed stabilization, prior to the winter season. (Level 2) - During construction and revegetation

PC5 A maintenance program is implemented to ensure restoration of sensitive resources. (Level 2) - During construction and post-construction

Effectiveness Criteria: Sites are returned to pre-construction conditions, no landowner complaints about restoration, permanent erosion control measures in place before winter season, and sensitive resources are restored.

Effectiveness Timing: After construction.

Applicant Proposed Measure H-23**: At larger stream crossings, the original stream banks would be graded to a 5:1 maximum slope, protected with a filter cloth and overlain with an aggregate bed; surface flows would be diverted across the ford by bladed swales. Materials for the fords would be stored adjacent to the installation. When no longer needed for construction traffic, the ford would be restored to original conditions for revegetation according to landowner requests and permitting conditions. Generally, construction traffic would not move up and down drainages except for limited, short runs as needed to install protective stream crossings features.

Impact: See Mitigation Measure B-AQ-4

Performance Criteria, Violation Level, and Timing: See Mitigation Measure B-AQ-4

Effectiveness Criteria: See Mitigation Measure B-AQ-4

Effectiveness Timing: See Mitigation Measure B-AQ-4