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Facility. The grading plan is the same for all of the potential composting alternatives. A one percent minimum grade is provided at all points in the composting site. The composting Windrows are arranged normal to the slope to allow free drainage and minimize ponding. The site is sloped to drain to two ditches designed to carry the water from the 25-year, 10- minute duration storm (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 runs off. This exceeds the 25-year, 24-hour rainfall event (2.28 inches). As described above in this section, the composting pad will be constructed of native earth. The permeability of soils below the surface of the composting pad is low. Operations will be suspended, if necessary, during periods of wet weather to prevent damage to the composting pad or the surface will be paved with gravel or asphalt if the economics justify the higher cost. Due to the low-permeability of native soils and depth to groundwater, monitoring of soil moisture is not warranted. Soil sampling for ammonia, nitrates, metals and trace organics could be conducted to confirm the lack of movement of these constituents. Given the slow annual movement of groundwater at this site, soils could be removed and disposed of if movement of pollutants was found through soil monitoring. 2.1.7 Leachate Control (14 CCR, Section 17867(a)(12)) If leachate generation is expected, provide a schematic drawing of the leachate collection and removal system. If necessary, indicate the location of drainage blankets, piping, drainage swales, collection points, etc. Describe the method of monitoring, collection, treatment, and disposal. Note: (1) Facilities that use amendments or additives in their composting operations shall include in their active composting areas a compost leachate management control system, which is designed to contain and collect twice the anticipated volume of compost leachate, and the precipitation from a 25 year, 24-hour rainstorm event, and (2) Shall have leachate holding facilities with a liner with a permeability of no greater than 1 x 106 cm/sec, which is constructed of a thickness and type of material that is resistant to damage due to weather or machinery, other standard allowed in writing by the regional board. Since additional water will only be applied to the compost when necessary for maintaining adequate internal moisture, significant leachate generation is not anticipated. As stated in Section 3.5.3, the site is in a region of net evaporation. Additionally, compost windrows typically form a light crust on the outside, which repels rainfall. The site's drainage control system was designed to handle all runoff from a 25-year, 24-hour storm, including runoff from the compost piles. This system is illustrated in Figure 6 and design calculations are attached in Appendix B. a. Leachate Barriers If leachate barriers are proposed, describe their length, width, depth, and design characteristics. There are no leachate barriers currently proposed for the site. Forward Composting Facility RCS1 7/20/09;Page 16 SWT Engineering