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Soil Suitability/ Nitrate Loading Study 1rerracon <br /> Manteca Farm Improvement - Manteca, California <br /> October 29, 2019 Terracon Project No. NA197073 <br /> Result(Nc)* Effluent Deep <br /> Concentration p <br /> Average Leachfield Percolation <br /> Septic System No. ( NcAcres(A) Daily Flow (Nw) Denitrification a Rainfall <br /> N) (Q)(gPd) (mg/L_N) (d) (R)(in) <br /> 3. Proposed 15,000 9.4 14.0 352 85 10% 2.70 <br /> SF Agricultural <br /> Building <br /> Nitrate as N Total 23.3 <br /> Septic Systems <br /> No. 1 &3 <br /> *Maximum contaminant level(MCL)for nitrate in drinking water is 10 mg/L-N. <br /> Based on the nitrate loading balance, the existing land use (Septic Systems No. 1 and 2) is 17.1 <br /> micrograms per liter(mg/L-N)which is above the maximum contaminant level (MCL) of 10 mg/L- <br /> N. The proposed 15,000 SF agricultural building (Septic System No. 3) is anticipated to add 9.4 <br /> mg/L-N. As the existing office building will be demolished, when the proposed 15,000 SF <br /> agricultural building is developed, the office building was not included in the final nitrate loading <br /> calculation. The existing land use (Septic System No. 1) and proposed land use (Septic System <br /> No. 3) have a combined nitrate loading balance of 23.3 mg/L-N, which is also above the MCL. <br /> 2.3.6 Impact of Nitrate Loading to Nearby Water Sources <br /> Based on a review of the topographic map (Section 1.1), an irrigation line is located along <br /> Brunswick Road, to the adjoining west of the site. As the subject property is relatively flat, we do <br /> not foresee percolating effluent affecting surface water resources. <br /> The existing groundwater well is located approximately 150+ feet west of the existing classroom <br /> building leachfield, 150+feet east of the existing office building leachfield, and 150+feet northeast <br /> of the proposed agricultural building leachfield. Records pertaining to the well construction were <br /> not found on the EHD website or on the California Department of Water Resources Well <br /> Completion Report Map Application. Based on the results of the groundwater analysis (Section <br /> 1.4.3) and deep silty sandy soils encountered in our test borings, there is a potential for nitrate <br /> leaching to impact groundwater. <br /> 2.4 Discussion of Nitrate Loading Results <br /> 2.4.1 Total Nitrate Impact <br /> Based on the method and assumptions described, the result of the nitrate loading balance for the <br /> existing classroom building and office building is 17.1 mg/L-N, which is above the MCL of 10 <br /> mg/L-N. The proposed 15,000 SF agricultural building is anticipated to further increase nitrate <br /> levels above the MCL to 23.3 mg/L-N when combined with the existing classroom building. <br /> Responsive ■ Resourceful ■ Reliable 18 <br />