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Soil Suitability/ Nitrate Loading Study Eagle's Nest Motorcycle School ,: Stockton, California July 27, 2021 Terracon Project No. NA217040 2.3.5 Nitrate Loading Scenario I Ferracon 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 9. Summary of Nitrate Mass Balance Equation. * Maximum contaminant level (MCL) for nitrate in drinking water is 10 mg1L-N Based on the nitrate loading balance, nitrate levels for the proposed motorcycle school is anticipated to increase nitrate levels to 3.1 mg/L-N which is below the MCL of 10 mg/L-N . 2.3.6 Impact of Nitrate Loading to Nearby Water Sources Based on the aerial photographs and topographic maps (Section 1.1), the nearest surface water source is the Diverting Canal which is located approximately 989 feet northeast of the site. Based on distance and gradient, the Diverting 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 Mitigation measures appear unwarranted. 3.0 CONCLUSIONS AND RECOMMENDATIONS Site soils consisted primarily of clay in the upper horizons and silty, silty sand and poorly graded sand to 25 feet. The percolation test results of 25 minutes per inch at 16 feet deep bgs indicate the soils within the proposed sewage disposal area appear suitable for seepage pits. Responsive ■ Resourceful ■ Reliable 16 Effluent Result (Nc)* Acres Average Concentration Leachfield Net Rainfall Septic System No. (mg/L-N) (A) Daily Flow (NW) Denitrification Recharge (Q) (gpd) (mg/L-N) (d) (in/year) (R) Proposed 3.1 2.28 55 85 25% 9.17 Motorcycle School * Maximum contaminant level (MCL) for nitrate in drinking water is 10 mg1L-N Based on the nitrate loading balance, nitrate levels for the proposed motorcycle school is anticipated to increase nitrate levels to 3.1 mg/L-N which is below the MCL of 10 mg/L-N . 2.3.6 Impact of Nitrate Loading to Nearby Water Sources Based on the aerial photographs and topographic maps (Section 1.1), the nearest surface water source is the Diverting Canal which is located approximately 989 feet northeast of the site. Based on distance and gradient, the Diverting 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 Mitigation measures appear unwarranted. 3.0 CONCLUSIONS AND RECOMMENDATIONS Site soils consisted primarily of clay in the upper horizons and silty, silty sand and poorly graded sand to 25 feet. The percolation test results of 25 minutes per inch at 16 feet deep bgs indicate the soils within the proposed sewage disposal area appear suitable for seepage pits. Responsive ■ Resourceful ■ Reliable 16