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December 14, 2005 NOA Project Number: E05 079B Page 4 -Parcel sizes, 1.81 AC (Parcel 1) and 2.68 AC (Parcel 2) i The resulting Nc value for Parcel 1 is 10.7 mg/L-N and for Parcel 2 the Nc value is 8.1 mg/L-N. Paan-lT-1 iM sli`ghti above h imum-ebntamiate'le el'(MCL) f=i'O-mg/L�I�sf0r-7 Mutes- N in-drinlcin water 10-7 mg/1TN)where-as-Parcel 2wL!slow-t e MCL for i'rates as N in ft g _ - drinking•water�(8 mgL�1 ) Conclusions and Recommendations In summary, a satisfactory percolation test was achieved on both proposed parcels. No ground 1 ary, rY p ` water was encountered in any of the borings drilled on the property to a maximum depth of 3.5 feet. The result of the nitrate loading calculation indicates a potential build up of nitrates slightly above 10 mg/L-N for Parcel and below 10 mg/L-N for Parcel 2. n general agreement with several assumptions and the f this addendum are i p The results o g g conclusions presented in the original Chesney Consulting report. The information presented in this addendum report may be relied on for the purposes of the soil suitability and nitrate loading addendum. Though Parcel 1 indicated a possibility of causing a buildup of nitrogen slightly above 10 mg/L- N in ground water, we do not anticipate a build up of nitrates to occur below the site do to the unlikeliness of two residences existing on the property with fall occupancy over the long term. Parcel 2 indicated a Nc value of 8.1 mg/L-N which is below the MCL for drinking water. Based on the results of the study, our recommendation for the project are to take some additional steps to minimize nitrogen impacts to ground water. The following steps will help to mitigate nitrate impacts to the ground water from the use of onsite septic systems. These steps have been accepted by EHD staff for similar projects in the Tracy area. Our office believes the project is suitable for development with an onsite septic system provided the following steps are taken: • Utilize standard filter bed septic system design as described by the EHD with.the following modifications Minimum Septic Tank Sizes (larger tank sizes may be imposed by EHD) 2 bedrooms- 1200 gallons 3 bedrooms- 1600 gallons 4 bedrooms-2000 gallons F 5 bedrooms-2400 gallons 6 bedroom homes and above will require consultation. i • Apply 4 loose inches of loose compost or peat in the bottom of the filter bed. Utilize gravel drain systems rather than gravelless drain products to improve