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SECTION 1 -LANDFILL EXPANSION ISSUES Page 1-12 Discussions with staff the Wastewater Facility indicate that a 90 day testing period will be required to determine the quality of the leachate. After this testing period, a pretreatment program,If even necessary, would be defined. 1.3.9 Leak Detection System The leak detection system is a series of secondary collection trenches located beneath the liner and directly below the leachate collection trenches. These secondary collection trenches are lined with a geomembrane liner and use a drainage gravel and collection pipe system similar to the leachate collection system. Although this leak detection system is not a full second liner, it does provide secondary containment beneath the collection trenches and sumps. These areas are considered the critical areas for potential landfill leakage because it is at these locations where the leachate is concentrated. The leak detection system functions to a degree as a vadose monitoring system in the sense that it can monitor for leakage through the liner. It will not be representative of the soil-pore liquid quality in the unsaturated zone beneath the water table. However,because of the extensive area and depth of the developed landfill, standard vadose monitoring methods do not appear to be practical. 1.4 SLUDGE TREATMENT FACILITIES The City of Stockton Municipal Utility Department(Department) stockpiled approximately 20,000 to 25,000 cubic yards of digested sewage sludge at the Austin Road Landfill. Permission was granted from the Regional Water Quality Control Board to use this material as the foundation for the final cover if the necessary compaction could be achieved. Due to concerns that this compaction requirement might be difficult to achieve,the City Department of Public Works(DPW) decided to not accept any more sludge at the landfill. Additional discussions with personnel at the Department and the DPW indicate that the Department will remove the stockpile at the landfill. They anticipate that this task will be performed prior to closure of the existing landfill. Removal of this material is not a part of this project. No sludge treatment facility is included in the conceptual design for the Austin Road Landfill expansion. At this time, the Department is managing its sewage sludge by hauling it to an agricultural user In Merced County. The Department is currently developing its long-term sludge management plans. Included In the alternatives to be evaluated is composting and co-composting. The facility for this procedure is anticipated to be sited adjacent to the wastewater treatment plant The composted material could be utilized in agriculture, for daily cover at the landfill, or as a soil amendment to aid in revegetation of the final cover at the landfill. As noted above, the anticipated location of the facility at this time is adjacent to the wastewater treatment plant; however, it is possible that both the Department and the DPW may wish to site such a facility at the Austin Road Landfill in the future. Therefore, in the conceptual site layout, approximately 13 acres are delineated for future composting and/or co-composting operations. Included in such a facility would be receiving and short term storage areas, a greenwaste sorting . area, a mixing area, windrow composting and curing areas, storage and loading areas for the R.W.Beck and Associates Gty of Ston 1811.002