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Turning will be scheduled to provide compliance with pathogen reduction requirements and maintain aerobic conditions. Water Usage. Water will be added to' the piles as necessary before turning to maintain efficient composting. Water will also be used to control dust from the compost pad and various composting operations such as grinding and screening as determined from experience. 2.1.5 Grading and Drainage Plan Provide a schematic drawing of the grading plan for the site. Indicate how this design will prevent ponding and control runoff. The grading and drainage plan (Figure 9) shows the proposed grading of the site. The grading plan is the same for all of the potential composting options. A one percent minimum grade is provided at all points in the composting site. The composting windrows are arranged normal to the site slope to allow free drainage and minimize ponding. The composting pad will be constructed of compacted native soils. These soils are silt and clay and when compacted will provide a composting pad of low permeability. During periods of wet weather, the composting facility may suspend composting operations to prevent damage to the composting pad. Alternatively, economics may allow construction of a gravel surfaced or asphalt paved composting pad to allow continuous operations. During periods of extreme wet weather, the composting facility may not accept wastes. The site is sloped to drain surface water to perimeter ditches designed to convey storm water from a 25-year, 10-minute duration storm event (0.25 inches, 1.5 inches per hour) assuming all the water that falls on the composting site runs off. The ditches will carry the water to a retention pond designed to hold the net average annual rainfall during months where rainfall exceeds evaporation (5.67 inches) assuming all the water that falls on the site composting runs off. This exceeds the 25-year, 24-hour rainfall event (2.28 inches). The location of the retention pond is shown on Figure 9. All surface water runoff from the Compost Facility will be collected and stored in the retention pond. Collected runoff that has not contacted any waste, or has contacted waste but meets the water quality criteria for storm water discharges, is either discharged to the South Fork, used to add water to the initial compost mixture to provide the desired initial moisture content, or evaporated. All collected runoff which does not meet the water quality criteria for stormwater discharge will be either pumped into the leachate evaporation pond located in Interim WMU F, or hauled to a wastewater treatment facility for treatment. 2.1.6 Pad Composition and Dimensions Active composting areas consisting solely of compacted soils shall be constructed such that the compacted soil layer is of sufficient thickness to ensure the integrity of the bottom I foot of compacted soil from the effects of composting operations. Forward Composting Facility Z:\PROJECTS\Allied Waste\Forward\Resource Recovery Facility\Permitting Services\2009 RCSI\RCSI Final 031609.doc; Page 20