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Taking the existing nitrate concentration determined in the on-site well in combination with the estimated theoretical recharge from the proposed 11 homes, the resultant concentration will theoretically remain under the MCL. SSS§ 4.2 Groundwater analyses of the on domestic well,which has subsequently been destroyed, indicates a relatively low nitrate concentration of 9 ppm. Considering upgradient potential nitrate sources,this concentration would have been expected to be higher. As referenced, the Groundwater Study conducted by EHD in 1994 revealed a very low impact to the domestic wells sampled and tested in the Morada Area. The primary logical reason for this low nitrate well water concentration must be attributable to the subsurface soils possessing a high denitrification potential. Groundwater depth under the site has risen from an approximate depth of 76 feet in 1992 to an approximate depth of 68 feet as measured in the on-site well for this Study. The groundwater directional flow has been in a predominate east southeast direction. Only the regional groundwater directional flow can be ascertained from the information provided in the Lines of Equal Elevation groundwater maps. It is possible that under localized conditions,the groundwater may flow in a different direction than that determined as the regional flow. Regardless, it is known that the Morada area and upgradient land use was, and still is under agricultural production, in addition to other potential upgradient nitrate sources. It can be hypothesized that the observed nitrate concentrations within Morada area groundwater is in equilibrium. Sources contributing nitrate to the underlying groundwater include indigenous soil concentrations from decomposing organic matter from past farming operations,rainfall, upgradient and historical agricultural fertilizer inputs, septic systems (particularly sumps and pits), and lawn/landscape fertilization. The sum total of these sources would suggest the potential for a much higher nitrate concentration than what was observed in the on-site well and in surrounding domestic wells. Factors decreasing the groundwater nitrate concentration include denitrification, groundwater movement(both vertical and horizontal),well pumping and hydraulics, and clean water recharge which contributes to a dilution effect. Therefore, if each of these sources and attenuating factors could be quantified on a mass balance basis, it may be that nitrate input is now roughly equivalent to output, or attenuation. Given that agricultural irrigation recharge is the largest single contributor to groundwater nitrate concentrations, and since the surrounding land has been farmed for several decades, it would be assumed that the nitrate concentrations in the underlying groundwater should be much higher than observed, if the attenuating factors were not significant. This is what was observed with the soil chemical analyses. The nitrate concentration within the soil environment under the existing leachline revealed a very high nitrate-nitrogen concentration of 97 ppm directly under the drain rock. SSS§ 6.7 For the Las Palmas project, it is imperative that: 1.) The architect/engineer/designer of the residential structures, 2.) The plumber, 3.)The septic system contractor, and 4.) The landscaper or landscape architect, must coordinate their services simultaneously for each individual Lot. The architect/engineer/designer must orientate the house on the Lot, taking into consideration the size of the house and location of the septic system disposal area. He/she must coordinate with the plumber to bring the influent to the proper location in relation to the septic tank(s) location. The septic system contractor must connect the system to the plumber's piping and install the disposal area under EHD guidelines. The landscaper must work with, and around the location of the tanks and disposal areas. Page -13- Chesney Consulting