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NOV 2 1 2001 ENVIR01,17 is i 1 i_43H PERP,1'1- HISTORICAL GROUNDWATER DEPTH In accordance with groundwater reports published by the San Joaquin County Flood Control and Water Conservation District (Spring 1990 to Spring 1999), high groundwater in the project area has been recorded at depths in the range of about 90 feet below ground surface. Based on readings determined from three on-site monitoring wells, the average water depth at the site has been about 87 feet below existing ground surface. FIELD EXPLORATIONS AND TESTING On September 11, 2001, four borings were drilled in the proposed leach field area at depths ranging from about 3 to 6 feet below site grade. Based on our findings, the subsurface soils encountered at the site consisted of fine-to medium-grained silty sands. A percolation test was performed in one 3-foot deep boring per accepted guidelines using clear potable water. A site plan showing the approximate percolation test location is attached. The procedure calls for first placing about 2 inches of fine gravel at the bottom of the bore hole. The hole is then pre-soaked with water at least 24 hours prior to performing the test. The test is performed by first adding about 6 inches of water above the gravel. From a fixed reference point, the drop in water level is measured in approximate 30 minute intervals for four hours, refilling as necessary to maintain about 6 inches of water over the gravel. Under the observation of a sanitarian from the San Joaquin County Public Health Department, the last 30 minute reading of the four hour period is recorded and used to calculate the percolation rate in minutes per inch. The estimated percolation rate at the test location is as summarized below. A copy of our field percolation test result is attached. Test Number De th,ft. Percolation Rate min./inch P-1 3.0 34.3 NITRATE LOADING CALCULATIONS Per San Joaquin County Public Health Services (SJCPHS) Department Environmental Health Division (PHS/EHD) requirements, the following presents a summary of our nitrate loading evaluation for the proposed new leach field. As you are aware, the drinking water standard for nitrate is 45 mg/1 as (NO3) and 10 mg/1 as Nitrogen (1). In our evaluation of nitrate loading, we have used the Hantzsche mass balance equation, which is presented below with an explanation for each factor and the value used in our study. Since the intent of the mass balance equation is to evaluate the impact on groundwater over a large area, we have evaluated the nitrate loading using the available, undeveloped/open 31 acres at the winery. This assumption should be conservative since the winery covers a total area of 113.5 acres. For the purpose of this analysis, we understand there will be approximately 40 full-time office staff and 10 full-time warehouse workers using the facility 5 days a week. According to San Joaquin County standards, the water usage of office and warehouse employees at buildings with no cafeterias is 30 and 15 gallons of 204599-01.G01/201 IR1454 November 21,2001 ©2001 Kleinfelder,Inc. Page 2 of 4