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WASTE DISCHARGE REQUIREMENTS ORDER NO. 99-103 -4- SEBASTIANI VINEYARDS, INC. SAN JOAQUIN COUNTY 20. Domestic wastes at TRV East and West are discharged to a septic system. There are three leachfields at the TRV East facility: near the northeastern corner, midway along the eastern boundary, and near the southern tip of the site. The leachfield at TRV West is near the southeastern corner of the facility 21. The total annual precipitation at the facilities is approximately 17.6 inches per year as measured at the City of Lodi, during the period from 1962 to 1996. The annual pan evaporation rate is 60 inches and the evapotranspiration rate is typically within five percent of the straight pan evaporation rate. 22. The TRV East facility had a 550-gallon, gasoline underground storage tank (UST) which was removed in November 1988. The UST site was investigated and remediated, and closure has been recommended by San Joaquin County (Local Oversight Program). Monitoring wells, installed as part of the investigation, indicate depth to groundwater has varied historically between approximately 5 to 20 feet bgs, with a westerly to northwesterly flow direction. 23. The Discharger sampled one of the existing UST monitoring wells in Spring 1999 and found 86 mg/1 of Nitrate and 1500 mg/l of Total Dissolved Solids (TDS). These concentrations are greater than their respective Maximum Contaminant Levels (MCLS), as cited in Finding No. 27. An upgradient monitoring well at the TRV East-facility is needed to determine whether these elevated compound concentrations are associated with past on-site discharges or regional activities. 24. Nitrate concentrations have been detected in area supply wells in excess of the Primary MCL, suggesting the presence of regional nitrate pollution. The main supply well at TRV East was replaced and abandoned in 1998 due to elevated nitrates, which were consistently detected at 40 to 55 mg/l. In addition, the backup fire supply well has consistently had over 70 mg/1 of Nitrate. According to the Environmental Health Division of San Joaquin County, the Turner Road School supply well had between 28 and 68 mg/l in samples collected during 1998. l 25. The ground surface elevation at the TRV East facility is approximately 20 feet mean sea level (msl), and is approximately 15 feet msl at the TRV West facility. Surface water drainage in the area of the TRV East and West facilities is to Sycamore Slough, tributary to South Fork Mokelumne River. The facilities are within Lower Mokelumne Hydrologic Area(No. 531.20), as depicted on interagency hydrologic maps prepared by the Department of Water Resources in August 1986. 26. The Board adopted a Water Quality Control Plan,Fourth Edition, for the Sacramento/San Joaquin River Basins (hereafter Basin Plan), which contains water quality objectives for all waters of the Basin. These requirements implement the Basin Plan. 27. The beneficial uses of Sycamore Slough and its tributaries are municipal, industrial, and agricultural supply; recreation; esthetic enjoyment; navigation; ground water recharge; fresh