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Draft Environmental Impact Report Page IV.F-22 Forward Inc. Landfill Expansion These procedures would reduce drainage impacts to a less than significant level. Mitigation Measure F1: None required. Impact F.2: Uncontrolled erosion from soil stockpiles and landfill surfaces,or inadvertent spills of refuse or other substances onsite,could contaminate surface water. { Erosion from stockpiles and landfill refuse could create sedimentation in Littlejohns Creek and cause potential contaminants in the refuse to migrate in the surface water and bedeposed downstream. Austin Road and Forward Landfill units have both historically had programs in place (Wet Weather Plans and Erosion Control Plans) to protect against such erosion and sedimentation. In 1996, the City of Stockton completed the Report of Disposal Site Information for Austin Road landfill that presented procedures for preventing spills as part of its standard operating plan. Forward Landfill also had a similar Report of Disposal Site Information { completed. The Austin Road Landfill Supplemental EIR(2000) showed no change to the impact analyses or proposed mitigation measures, due to the operation procedures being extended to the expanded landfill. These procedures also have been incorporated into the 2003 Consolidated Forward landfill permit. No new regulatory issues have been identified with regard to management of such erosion potential. The following procedures are proposed as part of the project: • The current Forward Landfill drainage control structures and monitoring would continue to be implemented to inhibit erosion and sedimentation in the expansion areas. Proposed structural controls include the drainage control system and daily cover. Operational controls include maintenance of the drainage system by keeping ditches clear of debris and excessive vegetation, and making needed repairs to drainage structures. Corrective measures would be implemented if inspections show excessive erosion or damage to drainage channels. Eroded areas would be mitigated by removing loose debris followed by replacement, regrading, and compacting the area. Monitoring and protection against sediment from entering the Littlejohn Creek channel would be implemented, including the diversion of part of Littlejohns Creek farther away from the landfilled area. • In order to minimize sediment transport to the Littlejohns Creek,landfill slopes, ridgetops, and peripheral areas would be revegetated to inhibit erosion. ' Implementation of these procedures would reduce the impact to a less-than-significant level. Mitigation Measure F.2: None required. Impact F.3: Groundwater contamination would result if the leachate collection systems for the expansion areas fail. The expansion areas would have a leachate collection system installed in the phased manner of the expansion that is designed to meet the Class II landfill requirements. While there have been no historical problems of note with the exiting leachate system at the landfill units and the new ` leachate collection system is not expected to encounter more difficult conditions that would inhibit its successful installation,there is always a change of failure of leachate systems due to differential settlement of the refuse beneath the liner and upward gas pressure on the liner. If the leachate collection system fails then contaminated leachate could potentially impact groundwater, which lies approximately 50 feet below the landfill.