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F CLUSIONStical test results of the Nitrate Loading Study, it has been determined that the water high concentrations of nitrate. It was also determined that due to factors which may fication and a clay stratum, the nitrate concentration decreases by an approximate factor of 10 between 13 feet and 28 feet below grade. It is assumed the referenced clay layer is significantly influencing the nitrate concentration above, in and below this stratum through denitrification and impedance of the downward migration of nitrate. This premise is based on the groundwater directional flow which places MW#1 downgradient from more than 50%of the defunct Hayres Egg Farm facility. Water sampled and tested from the on-site domestic well shows nonexistent nitrate in the deeper aquifers. This may be attributed to the upper clay layers as illustrated on the well log for the Widmer well, and possible influence from the San Joaquin River. From previous studies done between the west side of Interstate 5 and the San Joaquin River, analytical testing of several wells over the past 10 years has shown that the deeper aquifers in this locale contain no nitrate. A comparative nitrogen soil profile was done for this project, which included all of the major fractions of nitrogen: nitrate, organic and ammonium. This analysis determined that there is potential for sustained nitrate leaching throughout the soil profile, down to the capillary fringe and into the water table. Regarding the existing nitrate concentration in the water table, upgradient influences must be considered as contributing an indeterminable percentage of nitrate to the water table. As referenced, it is assumed that no manure, etc. was placed on APN 190-230-08, yet there is a high nitrate concentration in the underlying water table. Since upgradient influences cannot be mitigated, then mitigation must take place on the surface of the subject properties. Mitigation factors from the development of the subject properties include the dilution effects not only from treated septic effluent, but also stormwater retention basins. Development will create impermeable and semi-impermeable surfaces such as buildings, asphalt parking areas, concrete slabs and compacted aggregate base parking and driveways. All these improvements will act to prevent or impede the downward migration of nitrate through the soil profile. The number of people on the subject Properties should be limited in accordance with the nitrate loaaing.Qaleulatio . It will be a requirement of the Environmental Health Department to review and approve each proposed septic system installed on the subject properties. This is primarily so that one business does not overload the calculated nitrate loading exclusively. Shallow leachfields, or filter beds, will take advantage of the indigenous fine-grained soils that may promote denitrification. The denitrification potential in combination with landscape plants in the leachfield may reduce nitrate impact to the calculated extent. However, leachlines within landscaped areas should be assessed carefully. Ammonium in high concentrations can be toxic to plants under certain conditions whereby the ammonium ion is hydrolyzed to ammonia. If the landscape plants show signs of stress, this may be the reason. 13 Chmq Conwffing