SITE INFORMATION AND CORRESPONDENCE

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ORDER NO.R5-2002-0148 10 - INFORMATION SHEET MUSCO FAMILY OLIVE COMPANY AND THE STUDLEY COMPANY WASTEWATER TREATMENT AND LAND DISPOSAL FACILITY SAN JOAQUIN COUNTY The Discharger has submitted two quarters (April 2002 and July 2002) of water quality data for the site. With limited data, staff calculated the background groundwater monitoring wells in each zone by calculating the average value, and adding two standard deviations to establish a background water quality for the site. This procedure is consistent with CCR Title 27 Section 20415. Because two saturated zones have been identified at the site, each zone must include a unique water quality value. Wells MW-1 and MW-8 were selected as the background wells for the water table aquifer (i.e., Kleinfelder's "perched zone") and the confined unit(Kleinfelder's "deep zone") respectively. Well MW-1 was selected because it is the furthest upgradient shallow zone well. Although MW-8 is not the furthest upgradient confined zone well, it is downgradient of the processing facility which is not considered a source area, and it is located in an area that has not historically been used for land application until recently. The other confined zone wells were evaluated for use and determined to be inappropriate for the following reasons: Well MW-12 is located adjacent to the Title 27 surface impoundments, Well MW-9 is dry, and Well MW-4 is located adjacent to the 1 Mgal settling pond. Well MW-7 might be appropriate, however it is located downgradient of the Title 27 surface impoundments and therefore it was not selected. Staff calculated background groundwater quality values for both the water table and confined zones, as shown on the table below. For the water table aquifer, the limits are: TDS 850 mg/L, chloride 150 mg/L, and sodium 260 mg/L; for the confined aquifer they are: TDS 1,300 mg/L, chloride 400 mg/L, and sodium 300 mg/L. Well Date Units TDS Chloride Sodium Water Table Aquifer MW-1 4/10/02 mg/L 690 67 240 MW-1 6/24/02 mg/L 770 110 250 Average -- mg/L 730 88.5 245 St. Dev. mg/L 57 30 7 Background -- mg/L 850 150 260 Confined Aquifer MW-8 4/10/02 mg/L 1,300 130 280 MW-8 6/24/02 mg/L 1,300 270 290 Average -- mg/L 1,300 200 285 St. Dev. -- mg/L 0 99 7 Background mg/L 1,300 400 300 Alternative No. 4—Use of Regional Wells The 7 August 2002 Revised Background Water Quality Preliminary Evaluation Report described problems with the use of the onsite monitoring wells, and instead proposes the use of regional domestic/agricultural/industrial wells to determine the background groundwater quality. Staff disagree with a number of the conclusions in the report and consider a number of the conclusions unsupported based on the technical information presented in the reports. For example: