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Soil Suitability /Nitrate Loading Study Irerracon Thornton Road Trailer Parking Facility ■ Lodi, California December 15, 2021 ■ Terracon Project No. NA217079 2.3.5 Nitrate Loading Scenario A nitrate loading scenario was performed to determine the impact from the proposed project. The scenario utilizes the variables discussed previously which represent the estimated conditions and uses associated with this project. The following table presents a summary of the nitrate loading calculation for the site. A copy of the nitrate loading calculation is included in Appendix F. Table 8. Summary of Nitrate Mass Balance Equation. Maximum contaminant level (MCL) for nitrate in drinking water is 10 mg/L-N Based on the nitrate loading balance, nitrate levels for the proposed development is anticipated to increase nitrate levels to 2.7 mg/L-N for the project area which is below the MCL of 10 mg/L- N. 2.3.6 Impact of Nitrate Loading to Nearby Water Sources The nearest surface water source is an irrigation canal which is located to the adjoining north of the site 2,700± feet. Based on distance of the septic system and topographic cross -gradient position relative to the canal, the canal is not anticipated to be affected by percolating effluent. 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 indicate that the proposed development is anticipated to be below the MCL. 2.4.2 Methods of Mitigation Nitrate mitigation measures appear unwarranted. 3.0 CONCLUSIONS AND RECOMMENDATIONS Three percolation tests (P1-3', P2-3.5' and P3-6.3') were conducted in the vicinity of the proposed septic system located at 15314 Thornton Road (APN 025-19-031). The soils encountered in the percolation test borings consisted primarily of sandy silt in the upper foot and layers of silty sand at 3 feet. The two shallow percolation tests demonstrated a percolation rate of 8.32 minutes per Responsive ■ Resourceful ■ Reliable 15 Average Effluent Leachfield Net Rainfall Proposed Result (Nc)' Acres Daily Flow Concentration Denitrification Recharge Development (mg/L-N) (A) (Q) (gpd) (Nw) (d) (in/year) (R) (mg/L-N) Truck Facility 2.7 4.96 106.25 85 15% 11.46 Maximum contaminant level (MCL) for nitrate in drinking water is 10 mg/L-N Based on the nitrate loading balance, nitrate levels for the proposed development is anticipated to increase nitrate levels to 2.7 mg/L-N for the project area which is below the MCL of 10 mg/L- N. 2.3.6 Impact of Nitrate Loading to Nearby Water Sources The nearest surface water source is an irrigation canal which is located to the adjoining north of the site 2,700± feet. Based on distance of the septic system and topographic cross -gradient position relative to the canal, the canal is not anticipated to be affected by percolating effluent. 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 indicate that the proposed development is anticipated to be below the MCL. 2.4.2 Methods of Mitigation Nitrate mitigation measures appear unwarranted. 3.0 CONCLUSIONS AND RECOMMENDATIONS Three percolation tests (P1-3', P2-3.5' and P3-6.3') were conducted in the vicinity of the proposed septic system located at 15314 Thornton Road (APN 025-19-031). The soils encountered in the percolation test borings consisted primarily of sandy silt in the upper foot and layers of silty sand at 3 feet. The two shallow percolation tests demonstrated a percolation rate of 8.32 minutes per Responsive ■ Resourceful ■ Reliable 15