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October 11, 2005 NOA Project Number: E05111B 4.0 DISCUSSION OF NITRATE LOADING RESULTS 4.1 Total Nitrate Impact Based on the method and assumptions described,the result of the nitrate loading balance indicates that the proposed development on the proposed parcels should not cause a build up of nitrates in / the aquifer above 10 mg/L-N. However,a well water test has shown the groundwater concentration for nitrate was found to be 65.1 mg/L-NO3 (about 14.5 mg/L-N)which is fairly elevated. 0 i4G�/40t-'5� 4.2 Methods of Mitigation To minimize the impact to the aquifer from percolating effluent containing nitrogen,we would propose the following steps to be taken during construction the septic systems on the property. • Utilize standard leach line and seepage pit septic system with the following exceptions. • Minimum Septic Tank Sizes 2 bedroom-1200 3 bedroom- 1600 4 bedroom-2000 5 bedroom-2400 6 bedroom-3200 7 bedrooms and above will require consultation. • Apply 4 inches of compost or peat in the bottom of the leach line trenches. Utilize gravel drain systems to improve denitrification. • The effluent should fill the entire leach line trench up to 6-inches before being allowed to flow into any seepage pit for final disposal. 5.0 CONCLUSIONS AND RECOMMENDATIONS Our office concludes that the Site is suitable for development with the use of a modified standard septic system as discussed in Section 4.2.Methods of Mitigation. Though the standard septic systems are"improved" to enhance denitrification,it is difficult to quantify the denitrification capacity of these systems. We would estimate on the order of a 5 to 10 percent increase in denitrification when compared to standard systems. All septic system construction should follow the San Joaquin County On-Site Wastewater Disposal Standards where applicable. 7