SR0080609 SSNL - Laserfiche WebLink

Home Browse Search

CONCLUSIONS AND RECOMMENDATIONS In summary, the soil conditions examined near the proposed septic system drain field were found to be suitable for standard septic systems utilizing leach lines and seepage pits. Satisfactory soil percolation rates of 50.0 min/in (east side) and 41.7 min/in (west side) were observed in the shallow soil zones at the test locations. The depth of ground water based on recent aquifer levels is approximately 87 to 95 feet below ground surface. The ground-water flow beneath the Site is to the east or southeast at a rate of approximately four to eight feet per mile. San Joaquin County experienced its highest recent ground-water levels in spring of 1983 and 1999; depth to water was approximately 65 feet in 1983 and 70 feet in 1999\_, A water sample was collected from the domestic well on the Site as part of this investigation. Nitrate was detected in the sample at a concentration of 0.5 mg/L-N, well below the MCL of 10 mg/L-N. DBCP was not detected in the sample; the MCL for DBCP is 0.2 [g/L. Based on a review of San Joaquin County Environmental Health Department maps of nitrate and DBCP detections in nearby wells, it appears that eight wells within a half- mile radius of the subject Site have been tested for nitrate; it was detected in five at concentrations between 0.1 and 5.0 mg/L-N, and in three at concentrations between 5.1 and 10.0 mg/L-N. Six wells within one-half mile of the Site were tested for DBCP; no DBCP was detected in any of the wells. Based on the current project, the use of on-site septic tanks and drain field systems on the Site is not expected to cause a buildup of nitrate in the aquifer above 9.4 mg/L-N. This level falls below the US EPA drinking water recommendation of 10 mg/L-N. Because of the satisfactory result of the nitrate loading calculation, no nitrate mitigation is recommended. LOGE 1919 Page 13