SR0074455_SSNL - Laserfiche WebLink

Home Browse Search

LOGE 1605: Durst Winery NLS Addendum Page 2 March 21, 2016 aquifer would ever experience from the use of on-site septic systems. Mixing and dilution in the aquifer as well as adsorption and adhesion in the soil would tend to substantially reduce the concentration of percolating effluent. The Hantzsche and Finnemore equation is a conservative approximation of ground-water nitrate-nitrogen concentration resulting from the combined effect of on-site sewage disposal systems and precipitation of rain. The equation and method is for estimation of long-term effect ground-water quality, and is not intended for prediction of seasonal changes (Hantzsche and Finnemore, 1992). The method takes into account the development area, soil denitrification factor, rainfall, rainfall nitrate concentration, waste effluent quantity, and waste effluent nitrate concentration from on- site septic systems. No contribution from vineyard irrigation or any soil amendments is considered for the Hantzsche/Finnemore method. It is reasonably assumed that the irrigation and soil amendments would be applied at close to agronomic rates for a net balance of plant irrigation and nutrients. Mass Transport Soil Properties The percolation tests have revealed that the soils are moderately permeable. The soil will allow moderate infiltration of water through the surface soils. The longer the effluent remains near the surface, the more biologic treatment may occur. If permeable soils exist to the depth of the ground water aquifer, it is possible that any remaining surface contaminants may be transported to the first saturated zone of the aquifer. Sources of Nitrate Septic systems and dairies have been found to be the most significant sources of nitrate in ground water. Orchards that require fertilization in sandy soils are also a significant source of nitrate contamination in shallow or sandy aquifers in San Joaquin County. Contribution of Rainfall An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. An estimate of the deep percolation of rain was based a calculation using average monthly precipitation of rainfall and evapotranspiration rates for the area. The calculation first determines whether the average monthly precipitation exceeds average monthly potential evapotranspiration. If so, then the difference is potential deep percolation. This method does not consider runoff. Based on the calculation shown in the following table, the estimated deep percolation of rain (recharge) for the Acampo, California area is estimated to be 6.58 inches per year.