SU0003930 SSNL - Laserfiche WebLink

Home Browse Search

June 10,2002 Job Number: LG02-164 Page 12 VIII. CONCLUSIONS AND RECOMMENDATIONS In conclusion, a satisfactory percolation rate was achieved on proposed Parcel 1. No percolation test was performed on the designated remainder parcel. The Fisher Family does not plan to develop either the proposed new Parcel 1 or the designated remainder parcel. The septic permit review has shown that septic systems utilizing leach lines and sumps are used in the area. The depth to ground water was found to be about 12 to 13 feet below the ground surface. Ground water measured from the onsite water well was analyzed for DBCP and nitrate. The analysis indicated that DBCP was non-detectable (ND) and nitrate was found at 5.6 mg/1- NO3 (or 1.2 mg/L-N). The result of the nitrate test indicates the ground water is well below the maximum contaminate level set by the United States Environmental Protection Agency of 45 mg/L as NO3 (or 10 mg/L-N). As a result of the nitrate loading analysis, an average nitrate concentration of percolating water on both parcels is below 10 mg/L-N. This means that if both parcels are to be fully developed with SUD's, the long term average build up of nitrogen in the ground water is not expected to be above 10-mg/L-N. The nitrate concentration of 10 mg/L-N (or 45-mg/L-NO3) is the maximum contaminate limit for safe drinking water in California. This is mostly due to the relatively large size of the property, quantity of rain falling on the property, and the relatively low quantity of effluent. ,� care �ok '�� //Z6-0# A concern for development is the v sand soils encountered, the shallow depth to ground water, and the reported high existing levels oWtrate in the shallow ground water. Though the nitrate loading study indicate-da area wide build up would not occur above 10-mg/L- N in the shallow ground water, local impacts may occur due to the rapid percolation rates and the shallow depth to ground water. Based on these factors, we recommend the use of a filter bed. septic system or�ec uivalent, rUadified for additional nitrate reduction for any future construction on the property. Our specific recommendations are as follows: 1) A filter bed septic system or equivalent modified for nitrate reduction is recommended for any new construction. 2) To obtain some higher degree of nitrate reduction, a filter bed system should be supplemented with approximate) 4-inches of DQat or organic soil. This material should be placed on t e base of the filter bed below the filter material. The supplemental material should slow the percolation rate and provide a carbon source to increase denitrification of the effluent. ?pERSO P N a z W o � P <,ySp G♦