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Project Description - Report of Composting Site Information Tracy Material Recovery Facility and Transfer Station 30703 S. MacArthur Drive, Tracy, California 95377 = 4 northeast. The site is located in a relatively flat area east of the Diablo foothills. Prior to the commencement of gravel mining activities, the elevation of the site ranged from approximately 150 to 160 feet MSL (see Figure 2, Location Map). Generally, the side slopes of the quarry are inclined at from 2:1 (horizontal to vertical)to 4:1. A cut slope at the northwest comer of the quarry is inclined at approximately 1.5:1. The ground surface within the quarry is relatively level. Along the rim of the quarry the ground surface slopes gently to the east. Present site elevations range from approximately 160 feet MSL at the top of the pit to 120 feet MSL at in the bottom of the quarry Potable water is provided by an on site well. Rest rooms, serviced by a septic system, are located in the-maintenanceladministrative and MRFltransfer buildings. An emergency water supply system is in place in the event of an electrical outage capable of providing 150,000 gallons of water at 1,200 gallons per minute. Waste water from the truck wash is processed through an oil and grease separator before being discharged into the septic system. Wash down water from the MRFltransfer building is contained in storage tanks for transfer to a POTW. Storm water runoff and leachate from the compost pad is directed to an evaporation pond. The evaporation pond is lined with 3 foot of clay with a permeability of 1x10"6 centimeters per second (cm/sec) or less and sized for a 100 year/24 hour storm event. All other storm water runoff from the facility is directed to a retention pond. Storm water entering the retention pond evaporates and percolates. The retention pond is sized to contain 200 percent of the computed volume of runoff from the 10 year/24-hour rainstorm event (EBA, 1993). -` Based on groundwater levels recorded in 1990 by San Joaquin County Flood Control District, groundwater occurs at elevation of 60 to 70 feet which is approximately 40 to 50 feet below the bottom of the pit. This groundwater lies with sand and gravel layers of alluvial fan deposits and flow is towards the north (EBA, 1993). Eight exploratory borings were drilled at the site in July of 1993 by RGH (1993). These borings, located along the edge and in the bottom of the quarry, penetrated to depths of from 9 to 25 feet. These existing borings encountered interbedded sand, silt, and gravel, with discontinuous silt and clay layers to a depth of 25 feet. Groundwater was not encountered during drilling. Local water wells indicate that groundwater is present at a depth of approximately 90 feet. The San Joaquin County Flood Control and Water Conservation District maintains an annual record of elevation of water in wells in San Joaquin County. Water at the site stands at elevation 70 MSL, or at approximate depth 90 to 95 feet below the ground surface and approximately 40 to 50 feet below the bottom of the existing pit (EBA, 1993). All MRFITS and composting equipment is serviced, maintained and stored on site. To provide for disposal during wet weather all access roadways and operating areas are paved with either asphalt concrete or concrete. The following section "Site Characteristics" (in italics) is from the Report of Waste Discharge prepared by EBA Wastetechnologies in 1993. 5 Edgar&Associates,Inc. Tracy Compost Fac ProjDesc042310