SR0080950 SSNL - Laserfiche WebLink

Home Browse Search

CONCLUSIONS AND RECOMMENDATIONS In summary, the soil conditions near the proposed septic system drain field were found to be suitable. A satisfactory soil percolation rate of 22.7 min/was observed in the shallow soil zone at the percolation test location. The depth of ground water based on recent aquifer levels is approximately 90 to 100 feet below ground surface. Ground water flows down to the northeast at a rate of approximately 12 to 50 feet per mile. The highest recent ground-water levels for the area were experienced in spring of 1983 and 1999; at these times, ground water would have been present at approximately 70 feet below ground surface. Because the percolation rate encountered falls between 5.0 and 30 min/in, the San Joaquin County Environmental Health Department will require an eight-foot separation from the bottom of the dispersal system to ground water. Based on depth to water in the area, no modifications to standard systems should be required. 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 5.8 mg/L-N, below the MCL of 10 mg/L-N. DBCP was detected at a concentration of 0.86 1,tg/L, above the MCL of 0.2 1g/L. It is recommended that bottled water be utilized for drinking, cooking, and bathing until the concentration of DBCP can be brought below the MCL. Two possible ways to reduce the concentration of DBCP are modifying/repairing the domestic well or installing a whole-house water filter. Based on a review of the San Joaquin County Environmental Health Department map of nitrate detections in nearby wells, two wells within a half-mile radius of the subject Site have been tested for nitrate. Nitrate was detected in one well at a concentration between 0.1 and 5.0 mg/L-N, and in the other at a concentration between 5.1 and 10 mg/L-N. According to the DBCP map, one well within a half-mile radius of the Site has been tested for DBCP; DBCP was detected in this well at a concentration greater than 0.2 ig/L. 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 7.0 mg/L-N. This level falls below the US EPA drinking water recommendation of 10 mg/L-N. We believe the Site suitable for the use of standard septic systems utilizing leach lines and seepage pits. Based on the satisfactory result of the nitrate loading calculation, no nitrate mitigation is recommended for the current project. LOGE 1934 Page 13