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February 27,2002 Job Number:LG02-048 Page 13 —' Parcel Size Parcel No. (Plate No.) Result: Average Quantity of Nitrate Concentration Effluent of Percolating Water 2.50 acre(4-bdrm res+SDU) Parcels 2,3,41 5 (Plate 14) 11.23 mg/L-N 630 gpd 61.28 acre(4-bdrm res) Parcel 8 (Plate 15) 0.55 mg/L-N 350 gpd 61.28 acre(4-bdrm+ SDU) Parcel 8(Plate 16) 0.85 mg/L-N 630 gpd Note: Maximum drinking water standard for Nitrate is 10 mg/L-N(45 mg/L as NOJ,ac-acres,bdrm-bedroom,res- residence,SDU-second dwelling unit,gpd-gallons per day. As a result of the analysis, the addition of a single 4 bedroom home to each parcel is not predicted to contribute to a build up of nitrogen in the shallow ground water above 10 mg/L-N. A second dwelling unit constructed on Parcels 1 thru 7 may contribute to a build up of nitrogen in the shallow aquifer above 10 mg/L-N. The analysis has shown thata residence_and second_ dwelling unit constructed on the 6. 1.28 ac ..-site-will not contribute to a buildup of nitrates in the ground water above 10-mg/L-N. The nitrate concentration as nitrogen of 10 mg/L is the maximum contaminate unit for safe drinking water in California. VIII. CONCLUSIONS AND RECOMMENDATIONS In conclusion, a satisfactory percolation rate was achieved on all of the proposed parcels of the lot line adjustment. The septic permit review has shown that septic systems utilizing leach lines and filter beds are used in the area. The depth to ground water was found to be about 15 feet below the ground surface. The nitrate level of ground water measured directly from a shallow boring was found to be 13.092 mg/L-N(I 3092 ug/L-N). The nitrate concentration of 10 mg/L-N is the maximum contaminate limit for safe drinking water in California. No DBCP was detected in the water quality analysis. The source of the nitrate detected in the ground water sample is unknown but may be indicative of the overall quality of the shallow ground water. The concentration of nitrate in the shallow ground water may fluctuate with agricultural pumping, rainfall, irrigation, and fertilization of the orchards. The nitrate loading analysis has shown that constructing a second dwelling unit in addition to the.�rtaiti.rf de�uld_potentially contribute to the existing nitrate level in the - ._ shallow a uifer above 1 m L-N for arcels 1, 2, 3, 4, 5, 6, and 7. This contribution may occur because of the additional quantities of e uent om�' tie second dwelling unit, the relatively low denitrification factor in sandy soils, and the smaller parcel size or parcel density. jpERSO r t 1 h O � r �SSpC♦