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Soil Suitability/Nitrate Loading Study Irerracon Gribaudo Property ■ Acampo, CA November 12, 2019 ■ Terracon Project No. NA197081 Result Average Effluent Leachfield Deep APN Land Use (Nc)* Acres Daily Flow Denitrification Concentration Percolation (mg/L- (A) (Q)(gpd) (Nw) (d) of Rainfall N) (mg/L-N) (R)(in) Future residence(if Up to applicable) U9 80 36.62 5,500 45 35% 4.49 Proposed Acreage Nitrate as N Total Up to APN 017-260-30 9.8 *Maximum contaminant level(MCL)for nitrate in drinking water is 10 mg/L-N. Based on the nitrate mass balance, nitrate as nitrogen levels for the existing three bedroom residence located on the 2.0 acre parcel (APN 017-260-31) is 11.9 mg/L-N when two people are calculated per bedroom which is slightly above the MCL of 10.0 mg/L-N. There are currently no septic systems or structures located on the 35.81 acre parcel (APN 017- 260-30)or proposed to be developed on the parcel;therefore, a nitrate loading was not calculated. As the parcel is proposed to increase to 36.62 acres as part of the parcel realignment, a nitrate loading scenario was calculated as if the parcel will be developed with a residence at a later time. The parcel can theoretically be developed with a residential use septic system (up to 5,500- gallons per day) which results in a mass balance of 9.8 mg/L-N, below the MCL of 10.0 mg/L-N. 2.3.6 Impact of Nitrate Loading to Nearby Water Sources Based on a review of the topographic map (Section 1.1), there are no surface water sources near the site. As the subject property is relatively flat, we do not foresee percolating effluent affecting surface water resources. 2.4 Discussion of Nitrate Loading Results 2.4.1 Total Nitrate Impact Based on the method and assumptions described, the result of the nitrate loading balance (11.9 mg/L N) indicates that the existing residential use on the 2.0 acre parcel (APN 017-260-31) may cause a buildup of nitrates in the aquifer slightly above the MCL of 10 mg/L-N; however, based on the results of the domestic and agricultural well groundwater analysis, Nitrate as N (6.0 and 5.3 mg/L-N) reported below the MCL indicating the 120+ foot soil column between the leachfield and groundwater appears to provide adequate denitrification. The proposed 36.62 acre parcel (APN 017-260-30) can theoretically be developed with a residential use septic system up to 5,500-gallons per day resulting in a nitrate loading balance of 9.8 mg/L-N and remain below the MCL of 10.0 mg/L-N. Responsive■ Resourceful ■ Reliable 17