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WASTE DISCHARGE REQUIREMENTS ORDER NO.R5-2002-0220 -4- TEICHERT AGGREGATES TRACY ROCK PLANT SAN JOAQUIN COUNTY settling pond area is 150 acres. Precipitation that falls on current and former mining areas that do not drain to the settling ponds flows into agricultural tailwater ponds created to reclaim the land for agricultural use. The Discharger will construct site improvements as needed to redirect storm water flows to the new settling ponds so that there is no discharge of stone water to surface water drainage courses. 24. The Discharger's water balance indicates that the water surface elevation within the three new ponds will rise by approximately 15 feet during normal rainfall years, and by approximately 20 feet during the 100-year total annual precipitation event. Any water that overtops the three settling ponds will be contained within the bermed pond area, which provides an additional 28 vertical feet of storage over 22.3 acres. 25. The Discharger has not submitted any detailed as-built drawings or earthwork specifications for the perimeter berm to demonstrate that it is adequate to contain water. Therefore, it is appropriate to require the Discharger to submit such documentation. 26. In the past, others have operated concrete batch plants at the site. The Discharger once operated an asphalt batch plant,but it was recently relocated to the Discharger's Vernalis processing facility. The Discharger may wish to operate a portable asphalt plant and/or concrete batch plant at the facility in the future. There are underground asphalt storage tanks at the facility, which are not currently in use. Therefore, it is appropriate to include discharge specifications and provisions that address this potential future use. Site-Specific Conditions 27. The average annual precipitation is approximately 10 inches and reference evapotranspiration (ETo)rates average approximately 57 inches per year. 28. Surrounding land uses are primarily industrial and agricultural. Tracy Municipal Airport is located west of the site. 29. Process water is supplied by an onsite groundwater well equipped with a 4,000-gpm pump. A second supply well near the scale house supplies non-potable water to the scalehouse. Drinking water for the site is supplied by bottled water. The Discharger does not treat the groundwater prior to use. 30. According to the RWD, the entire facility site has been disturbed by previous and current mining activities, and there are no defined surface water drainage courses on-site. However, local drainage is to the Sacramento-San Joaquin River Delta. 31. The facility is outside the 100-year flood zone. Groundwater Considerations 32. Groundwater exists approximately 90 feet below ground surface. Based on interpretation of the surface topography, groundwater likely flows to the northeast. No site-specific groundwater quality data are available.