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11. Project Description <br /> The leachate collection pumps would discharge to a perimeter leachate header force main. The <br /> main would transport the leachate to the leachate collection holding facility,northwest of the <br /> existing landfill. Pumper trucks would collect the leachate and haul it to the Stockton Municipal <br /> Utility Department for treatment. A 90 day testing period would be required to determine the <br /> quality of the leachate. After this testing period,a pretreatment program,if necessary,would be <br /> defined, Leachate at the holding facility would be removed as necessary. <br /> Uak Detection System <br /> The leak detection system would consist of a series of secondary collection trenches located <br /> beneath the liner and directly below the leachate collection trenches,providing a secondary <br /> containment beneath the leachate collection trenches and sumps. The secondary collection <br /> trenches are lined with a geomembrane liner and use a drainage gravel and collection pipe <br /> similar to the leachate collection system. <br /> This leak detection system would act as a vadose monitoring system to the degree that it can <br /> monitor for leakage through the liner. It would not however,be representative of the soil-pore <br /> liquid quality in the unsaturated zone beneath the water table. A standard vadose monitoring <br /> method would not be practical at this landfill because of the extensive area and depth of the <br /> developed landfill. <br /> Erosion Control <br /> Erosion control measures are necessary to minimize the amount of soil removed from the <br /> landfill. The proposed measures include minimizing slope and runoff distance,providing <br /> vegetative cover,contour furrowing the surface,increasing the organic content of the soil,and <br /> using mulch,erosion control blankets,terraces on steep slopes,sediment basins,and silt fences <br /> or straw bales. <br /> Side slopes would be more prone to erosion because of the steeper slope gradient. The proposed <br /> expansion plans show that the slope is limited to 4:1 (horizontal change:vertical change), <br /> compared to the 1.75:1 allowed by the California regulations. Additional erosion control <br /> measures may be required on the side slopes such as erosion control matting and silt fences. Silt <br /> fences should be included particularly during the first year when the erosion potential of the soil <br /> is high. Phased or partial closure of the landfill site would reduce the potential for excessive <br /> erosion by reducing the unestablished surface <br /> 11.14 <br />