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September 20,2002 Job Number: LG02-261 Page 11 VIII. CONCLUSIONS AND RECOMMENDATIONS _ In conclusion, a satisfactory percolation rate was achieved within all the parcels of the area. The Fall 1998 and Spring 1999 ground-water depth below the site was found to range between 50 to 70 feet in depth. The ground water flow direction at this time was eastward. A ground-water sample obtained from a neighboring water well was analyzed for DBCP and nitrate. The analysis indicated that DBCP was non-detectable and nitrate was 10 mg/L as NO3. 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(Nc) for the 2-acre property with a 3-bedroom residence and second dwelling units is 1_3.4 _ mg/L-N. The average nitrate concentration of percolating water (Nc) for the 45.63-acre property with a 3-bedroom residence with a second dwelling unit is 1.06 mg/L-N. The maximum contaminate limit for safe drinking water is 10 mg/L-N (or 45-mg/L-NO;). The nitrate concentration of ground water could potentially raise above 10 mg/L-N due to the use of a residence and second unit dwelling on all the 2-acre parcels. Because of the sandy soil conditions, fairly rapid percolation rates, and nitrate loading analysis, a filter bed system optimized for nitrate removal is recommended to be utilized on all the 2 aces sites. This type of system should also be utilized on the 45 acre site due to help mitigate the rapid percolation rates. Our office recommends the use of en>;ineered septic systems for the proposed project. These system will significantly reduce the potential impact to ground water from the septic system effluent. Our office could provide additional information, cost estimates, and engineering services for the engineered septic systems. IX. LIMITATIONS _ The conclusions of this report are based on the information provided regarding the existing and proposed development,the use of the subject property, and the site conditions as they existed at the time we excavated our test holes and performed the percolation tests. It was assumed that the test holes and percolation test results are representative of the subsurface conditions in the general area. rOER30 • N Z W O � �'fiO C