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1 <br /> Soil Suitability/ Nitrate Loading Study Addendum Letter <br /> Lange Twins Winery , Acampo, California Irerracon <br /> May 21, 2019 o-. Terracon Project No. NA197005 <br /> Result Effluent Deep <br /> Septic Leachfield <br /> Tank Land Use <br /> (Nc)* Acres 'Average Daily Concentration Denitrification Percolation <br /> (mg/L- (A) Flow(Q)(gpd) (Nw) (d) of Rainfall <br /> No. N) (mg/L-N) (R)(in) <br /> Future <br /> Tasting Room <br /> 6 Stand Alone 2.2 41.38 275.03 85 25% 4.49 <br /> Restroom <br /> Building <br /> (400 SF) <br /> Future <br /> 7 Administration 1.9 41.38 206.27 85 25% 4.49 <br /> Building <br /> Special 1.2 41.38 54.79 85 25% 4.49 <br /> Events <br /> 'Maximum contaminant level(MCL)for nitrate in drinking water is 10 mg/L-N. <br /> Highest average daily flow rate calculated per septic tank/building. <br /> Based on the nitrate loading balance calculation, nitrate as N levels for the existing facility is 9.0 <br /> mg/L-N with up to 10.2 mg/L-N when a special event occurs. The proposed development is <br /> anticipated to add 1.9 mg/L-N which increases nitrate as N levels for the facility to 12.1 mg/L-N <br /> slightly above the MCL of 10 mg/L-N. <br /> It should be noted the future tasting room stand alone restroom building will serve as the primary <br /> restroom for the daily customers visiting the existing wine tasting room; therefore, the nitrate <br /> loading of 2.2 mg/L-N associated with future restroom was not included in the above calculations <br /> as not to be counted twice. <br /> Conclusions and Recommendations <br /> Depth to groundwater is approximately 57 feet bgs with a southeast groundwater flow direction. <br /> Low levels of nitrate as N (<2.7 mg/L-N)were reported in the onsite groundwater monitoring well <br /> (MW-3) below the MCL of 10 mg/L-N. Elevated nitrate as N levels (<39 mg/L-N) were reported <br /> in off-site groundwater monitoring wells (MW-1 and MW-2) located to the adjoining west of the <br /> site. <br /> A groundwater sample analysis and a percolation test were not included as part of the SSNLS <br /> addendum. <br /> The on-site septic system currently consists of five septic tanks with a tank holding capacity of <br /> 8,700 gallons which discharge to a common 1,248.5 SF leach field area. The proposed <br /> development will add two additional septic tanks with a 4,000 gallon tank holding capacity which <br /> will also discharge to the common leach field. The total tank holding capacity for the facility will <br /> be 12,700 gallons. <br /> Responsive■ Resourceful ■ Reliable 7 <br />