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%Supplemental Information Report Of Waste Discharge 8200 N. Highway 99,Stockton, CA Page 3 of 6 6. The proposed extraction system is an interim remediation system. A final remediation system, consisting of groundwater extraction/treatment and/or ozone injection, will be proposed after the interim system can be evaluated for effectiveness. At minimum, we expect groundwater extraction to continue for at Ieast 6-12 months before a final remediation plan is submitted. 7. The nearest known water user is located 350 feet north (cross-gradient) of the proposed extraction well and the proposed discharge area. Since domestic wells in the area are generally completed at depths greater than 120 feet, we do not expect any nearby water users to be directly affected by groundwater extraction or treatment system discharge, given the required effluent limitations. 8. According the Soil Survey of San Joaquin County, California, (USDA, Soil Conservation Service, 1992) the area of discharge is located within Soil Map Unit 180-Jacktone clay. According to the reference, the rate of water intake in irrigated areas is 0.1 inch per hour. Assuming a discharge area of 40 by 100 feet, this corresponds to approximately 250 gallons per hour, or more than 4 gpm. We anticipate extracting an average of up to 2 gpm from well MW 1. C. Groundwater Monitoring Program Groundwater monitoring wells at the site are currently sampled on a quarterly basis. The existing schedule will be adopted for the groundwater monitoring program. Measurement of the Depth to Groundwater in Monitoring Wells The depth of the groundwater surface in each monitoring well will be measured from the top of the well casing to the nearest 0.01 foot with a Solinst or similar electronic water-level indicator. The well will be vented to the atmosphere before obtaining depth-to-water measurements. Venting will be conducted to allow the groundwater to equilibrate to barometric pressure. These measurements are utilized with recorded well casing elevations to evaluate the elevation of the groundwater surface in each well and the slope of the groundwater surface across the site, if enough data points are available. Sampling of Groundwater Monitoring Wells The static water level in each well will be measured to the nearest 0.01 foot with a Solinst or similar electronic water-level indicator cleaned with a laboratory-grade detergent and deionized water before use in each well. A clean bailer will be used to obtain a sample from the surface of the water in the well for subjective analysis of hydrocarbons, if appropriate. The sample will be retrieved and examined for floating product, sheen, color, and clarity. Approximately 3 to 5 well volumes will be purged from each well using a submersible pump or a Teflon bailer to allow sampling of representative formation water. All downhole equipment/materials are decontaminated before use in each well. The wells are purged until pH, temperature, and electrical GAG ROUN DZEITULEB t J RGIReports\%vork plan\W DRSu pplementil.doc