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Soil Suitability/ Nitrate Loading Study Addendum Irerracon <br /> Arriaga Property Stockton, California <br /> August 31, 2020 Terracon Project No. NA207046 <br /> Table 8. <br /> Typical Quantity of Effluent - Revised. <br /> Average Effluent Average Effluent <br /> Number of Quantity for Long Term Average <br /> Residence ID total Quantity for Additional Discharge Rate <br /> bedrooms Bedroom 1 Bedroom(s) (gpd*) <br /> (gpd*) (gpd*) <br /> Existing Residence 2 100 x 1 50 x 1 150 <br /> Proposed Mobile 2 100 x 1 50 x 1 150 <br /> Total gpd 300 <br /> 'gpd-gallons per day <br /> Based on a review of Table 8, the revised long term average discharge rate for the existing and <br /> proposed residence is 300-gallons of effluent per day. <br /> As indicated in our prior 2019 NLS report (Terracon Project No. NA187059), it is estimated that <br /> the average concentration for total nitrogen in wastewater for the project is approximately 35 <br /> mg/L-N over the long term. <br /> 2.3.4.2 Denitrification Estimate <br /> As indicated in our prior 2019 NLS report (Terracon Project No. NA187059), based on the clay <br /> soils anticipated at leach field depths (between 36 and 42 inches bgs), hardpan layer, and <br /> stratified clay soils to 500 feet bgs, a denitrification factor of 35 percent was selected. <br /> 2.3.5 Nitrate Loading Scenario <br /> As reported in our prior 2019 NLS report (Terracon Project No. NA187059), nitrate levels for the <br /> current two bedroom residence (12.6 mg/L-N) was anticipated to slightly exceed the MCL of 10 <br /> mg/L-N for nitrate in drinking water when an average two person occupancy was calculated per <br /> bedroom. The construction of the proposed two bedroom mobile home (12.6 mg/L-N) was <br /> anticipated to further increase nitrate levels to 25.2 mg/L-N, also above allowable limits for <br /> groundwater. <br /> For the purpose of the nitrate mass balance equation, the long term average discharge rate for <br /> each septic system was added together to calculate the nitrate loading for the parcel. The <br /> following table presents a summary of the revised nitrate loading calculation based on the revised <br /> long term average discharge and revised net rainfall recharge. <br /> Table 9. <br /> Summaryof Nitrate Mass Balance Equation - Revised. <br /> ResultAverage Effluent Leachfield Net Rainfall <br /> Land Use (Nc)* Acres Daily Flow Concentration Denitrification Recharge <br /> (mg/L-N) (A) (Q)(gpd) (m9 L)N) (d) (R)(in/year) <br /> Existing 2 Bedroom 4.5 1.25 150 35 35% 8.35 <br /> Residence <br /> Responsive ■ Resourceful ■ Reliable 14 <br />