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u 1%./ Additional constituents tested were Total Dissolved Solids (TDS),pH and Total Alkalinity. These constituents play a role in nitrification. A summary of the water well test results discussed above are as follows: TABLE 5 UNDERLYING GROUNDWATER ANALYSIS FROM ON-SITE DOMESTIC WELL ANALYTE LEVEL FOUND MAXIMUM CONTAMINANT LEVEL (MCL) Nitrate 9 mg/I, 45 mg/L Total Dissolved Solids 380 mg/L No Standard(500 mg/L Recommended Level) pH 7.7 Range 6.5-8.5 Total Alkalinity 196 mg/L No Standard Calculation of Alkalinity Requirement for Nitrification The nitrate-nitrogen loading calculations below are contingent upon the environmental factors required for nitrification to occur. These conditions include soil pore-space oxygen content, soil temperature,pH, electrical conductivity, organic matter, cation exchange capacity, and alkalinity. Alkalinity in wastewater effluent is derived from the domestic water supply in addition to the introduction of wastes. Nitrification consumes approximately 7.1 mg of alkalinity for every mg of ammonia-nitrogen(NH4 N) oxidized. Nitrification of the average Total Nitrogen (TN) concentration of 66 mg/L, as determined below would require: 66 mg/L NH;N x 7.1 mg CaCO3=469 mg/L alkalinity. Therefore,nitrification may be inhibited if the alkalinity in the domestic water supply is approximately 196 mg/L and the TN is approximately 66 ppm. B. SURFACE WATER INFORMATION Surface water consists of all other water sources originating on the surface of the project, other than septic system effluent. These sources include rainfall, surface runoff, domestic irrigation and stormwater retention. The San Joaquin County of Public Works -Isohyetal Map shows 15.5 inches of rainfall to be the Mean Annual Precipitation over the project locale. As the project is built-out, a percentage of the land surface will be impermeably covered with structures, concrete, asphalt, etc. This will have an attenuating effect from surface water(rainfall and domestic irrigation) on the downward migration of nitrate molecules currently"in-transit'and on nitrate yet to be formed. These impermeable surfaces will be traded for potential point sources of nitrate,namely the on-site septic systems, lawns, and landscaping. Domestic irrigation recharge can account for 250 to 1,500 gallons of water/day/residence during the spring and summer months (approx. 6 mos. out of the yr). Excessive lawn and landscape watering can lead to nitrogen leaching, or runoff to open areas, including the retention basin to become a point source. Page-8- Chesney Consulting