Hydrology and Water Quality

H-1a Implementation of Erosion and Sediment Best Management Practices. The following Best Management Practices (BMPs) shall be implemented in order to minimize potential hydrologic and water quality impacts of erosion and sedimentation created through project construction:

· Mechanical and vegetative measures shall be implemented to provide surface soil stability where necessary, as described in Section 12.22 (Road and Building Site Construction Best Management Practices) of the USDA's guidance document entitled "Water Quality Management for Forest System Lands in California" (USDA, 2005). Mechanical measures may include but are not limited to: wattles, erosion nets, terraces, side drains, blankets, mats, riprapping, much, tackifiers, pavement, soil seals, and windrowing construction slash at the toe of fill slopes. Vegetative measures shall be used to supplement mechanical measures, as appropriate.

· Road slope stabilization practices shall be implemented prior to the first winter rains. These practices shall include: verification of the correct slope steepness as dependent upon the dominant soil type/s present, implementation of methods to handle surface and subsurface runoff, and finalization of road surface compaction or application of appropriate surfacing material.

· Any temporary roadways which are built or used for the purpose of transporting construction equipment and materials to construction sites shall be situated to prevent undercutting of the designated final cut slope, avoid deposition of materials outside the designated roadway limits, and accommodate drainage with temporary culverts as necessary. Proposed road designs on NFS lands shall be submitted to the USDA Forest Service for prior approval and shall be incorporated into the Special Use Authorizations to be issued by the USDA Forest Service.

· Embankment methods shall be implemented to ensure adequate strength of the roadway and shoulder and to minimize potential failure of road embankments and fill areas. Acceptable stabilization methods include: sidecasting and end dumping, layer placement (roller compaction), controlled compaction, minimization of fill volumes, or strengthening of fills using retaining walls, confinement systems, plantings, or a combination of techniques. The appropriate stabilization effort shall be determined by the supervising project or crew leader prior to the onset of construction, based on site-specific conditions. Proposed stabilization efforts on NFS lands shall be submitted to the USDA Forest Service for prior approval and shall be incorporated into the Special Use Authorizations to be issued by the USDA Forest Service.

· Strictly control vehicular traffic to only that which is necessary.

· Restore temporary construction areas (e.g., temporary roads, pulling and splicing stations) to a near natural condition and ensure that the sites are re-vegetated and stabilized, unless operation and maintenance of the project would require the areas to remain clear. Restoration plans on NFS lands shall be submitted to the USDA Forest Service for prior approval, and shall be incorporated into the Special Use Authorizations to be issued by the USDA Forest Service.

· Establish the use of concrete washout stations to capture and contain concrete washout material and wastewater to avoid direct release of washout to surface water. Any concrete waste shall be disposed of properly on non-NFS lands.

· Erosion control measures shall be completed prior to the first anticipated rains at all construction sites. An Erosion Control Plan shall be prepared as part of the Project SWPPP, and shall be submitted to the USDA Forest Service for prior approval and incorporated into the Special Use Authorizations to be issued by the USDA Forest Service.

H-1b Maximum Road Gradient. The maximum allowable road gradient applicable to all new roadways, including access roads and spur roads, which would be installed to provide temporary or permanent access during construction and/or operation and maintenance activities shall be no greater than ten percent, except where SCE can demonstrate that a steeper grade, such as twelve percent, results in fewer impacts.

H-1c Road Surface Treatment. Road surface treatments shall be implemented on non-NFS lands in order to minimize the erosion of road surface materials and reduce the likelihood of related sediment production. Treatments may include watering, dust oiling, penetration oiling, sealing, aggregate surfacing, chip sealing, or paving. The technique utilized at each site shall depend upon traffic, soils, geology, and road design specifications. The Forest Service shall approve all road surface treatments implemented on NFS lands. Watering of roads shall be required on NFS lands. Site-specific road surface treatments shall be specified by the supervising project or crew leader prior to the onset of construction activities.

H-1d Timing of Construction Activities. Construction activities, particularly regarding roadway installations and improvements, must occur during the dry season or when precipitation events are not expected.

H-1e Dispersion of Subsurface Drainage from Slope Construction Areas. In order to minimize sediment production from the potential failure of slope construction areas, subsurface drainage devices shall be implemented where necessary, as determined during final siting and engineering of transmission towers. Where it is determined necessary due to site-specific conditions such as slope severity, soil condition, precipitation levels, and inherent instability, subsurface drainage will be utilized to avoid moisture saturation and potential subsequent slope failure. Subsurface dispersion methods would include underdrains or subdrains such as pipes, horizontal drains, or chimney drains. Proposed subsurface drainage devices on NFS lands shall be submitted to the USDA Forest Service for prior approval, and shall be incorporated into the Special Use Authorizations to be issued by the USDA Forest Service.

H-1f Control of Side-cast Material, Right-of-Way Debris and Roadway Debris. Side-cast material includes any loose, unconsolidated materials that must be re-located to facilitate construction activities. This may include rocks and boulders as well as other organic materials. Prior to the onset of any construction activities, waste areas must be designated where excess material can be deposited and stabilized. During road construction and maintenance, potential sidecast and other waste material will be utilized on the road surface. Any unused material shall be removed to designated disposal sites. Waste areas shall not be left exposed and must be transported to disposal facilities on a regular basis, which will be determined based on site-specific conditions. Temporary waste areas shall be located on NFS lands as needed, but shall be subject to prior approval by the USDA Forest Service Officer. At a minimum, temporary waste areas shall be removed before the first anticipated rains. Disposal areas shall not be located on NFS lands.

H-4 Develop and Implement a Groundwater Remediation Plan. Prior to the onset of any construction activities, the Applicant shall determine the specific location and extent of any groundwater resources that may be encountered through project-related excavation activities such as the installation of underground infrastructure. The Applicant shall develop and implement a groundwater remediation plan if it is determined that known groundwater resources would be unavoidable during construction. In the event that unknown groundwater resources are encountered or an unplanned disturbance of known resources occurs, the Applicant shall immediately halt the disruptive excavation activity and develop and implement a site-specific remediation plan. This remediation plan may require activities such as bioremediation or other applicable technology, as determined appropriate under site-specific conditions.

H-5 Permeability of Ground Cover. Untreated crushed rock or a comparable material will be used to maintain permeability to the subsurface and allow for infiltration in all areas where it is necessary to provide a cap over the natural or existing ground cover, including over trenches, graded access roads , underground transition stations, and substation additions or expansions, and excluding areas where it is necessary to use an impermeable material such as concrete.

H-7 Aboveground Structures shall be Protected Against Flood and Erosion Damage. Aboveground project features such as transmission line towers and substation facilities shall be designed and engineered to withstand any mechanical stresses that may result from location, such as potential flooding or erosion of the surrounding area. Site-specific measures may include tower anchoring, installation of slope protection, or raising foundation levels. All Project-related facilities shall be placed outside the current and reasonably expected future flow path of watercourses. No Project-related facilities shall be positioned within a known watercourse.