SU0008520 SSNL - Laserfiche WebLink

Home Browse Search

rSources ontributing nitrate to the underlying groundwater in this locale also include indigenous soil eoncentrations from lightning/rainfall, past and present upgradient agricultural fertilizer inputs, septic systems, lawn/landscape fertilization and naturally occurring geological deposits. Of these sources; however, it appears that only past and present upgradient agricultural fertilizer inputs, decomposing organic matter and naturally occurring geological deposits are contributing nitrate to the groundwater underlying the Church property. Factors decreasing the groundwater nitrate concentration include denitrification, groundwater movement (both vertical and horizontal), well pumping and hydraulics, and cleaner water recharge contributing to a dilution effect. If each of these sources and attenuating factors could be quantified on a mass balance basis, it may be that nitrate input to groundwater is now roughly equivalent to output, or what is referred to as attenuation. Given that agricultural irrigation recharge is the largest single contributor to groundwater nitrate concentrations, and since the underlying and surrounding land has been farmed for several decades, it could be assumed that the nitrate concentrations in the underlying groundwater should be much higher than those observed, if the attenuating factors were not significant. This is particularly evident with the soil nitrate-nitrogen test results of the sampled depths. The denitrification potential appears to be a factor due to the clay content and differential strata of the indigenous soils, the higher soil pH, high soil moisture content and organic fraction content. Jenssen and Siegrist (1990) found the factors that favor denitrification are fine-grained soils such as clays and silts layered with soils consisting of alternating fine-grained and coarser grained soils with distinct boundaries between the texturally different strata. This was observed in the exploratory/deep perc test boring whereby percolating water encountering coarser soil strata accumulates on top of this stratum until sufficient soil moisture increases for the soil vadose water to travel into this higher porosity stratum. This strata differentiation may also explain the low soil nitrate-nitrogen concentrations, and comparatively low concentrations of nitrate in the groundwater(as determined in the on-site domestic well) throughout the Morada area by creating favorable denitrification environments. NLS§ 4.2, SSS§ 6.7. Due to the referenced problems that have occurred along Highway 99 corridor with conventional septic systems, it is the opinion of the EHD that the upcoming new General Plan may require commercial facilities along Highway 99 which must operate with decentralized systems, may have to at some point in the future, treat their wastewater to a higher degree. NLS§ 4.1. The nitrate loading calculations show the resultant effluent from the proposed project will theoretically possess a nitrate-nitrogen concentration under the Federal nitrate Maximum {� Contaminant Level of 45 ppm as nitrate. A total nitrogen concentration almost equivalent to domestic sources, as referenced in the scientific literature was used in the loading calculations giving a significant safety factor. 1 recommended, and will ultimately become an EHD requirement, i It is a so e to nstall a water use meter Y Y—on the domestic well supply line that will serve the new Church facility. The EHD may also stipulate Pp Y tY Y p that a water meter be installed on the landscape line. As referenced, the defunct irrigation well is to be destroyed under EHD permit. This well was determined to be 94 ft deep with a Standing Water .Level (SWL) at 75 ft. Therefore, the well possesses very small volume capacity. 12 Chesney Consulting f