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C water sample was obtained from the domestic well that serves the residence on...the subject property:. _ (110 E nce the actual well is inside the detached garage, the water sample was taken from an outdoor nk/faucet. Two separate containers were usedfor the analyses. For nitrate and total alkalinity, a plastic bottle was used for-the sample and for the DBCP/EDB analysis a VOC bottle containing preservative was used. The-samples,were drawn-after,.the.wellpump-had run-for.ten minutes to f censure aquifer formation-water.was.sampled The samples were placed in a cooled ice chest and; transported to A&L Labs of Modesto, under the attached Chain of Custody.. Testing of the well water sample reveals a nitrate concentration'of 52 pnm .4 m NQ -N). The Maximum Contaminant Level (MCL) for nitrate (as NO3) is 45 ppm. Dibromochloropropane- was detected at 0.15 The MCL for DBCP is 0.0002 ppm or 0.2 µg/L. Therefore, the shallower aquifers are near the MCL for DBCP. Ethylene dibromide (EDB) was found to be non-detect. The nitrate-nitrogen loading calculations below are contingent upon the environmental factors - required for nitrification to occur. As discussed; 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 and the _ introduction of wastes to the wastewater: Nitrification consumes approximately 7.1 mg of alkalinity ! for every milligram of ammonia-nitrogen (NH,-N) oxidized. Water chemistry results for the on-site domestic well indicate a Total Alkalinity of 232 mg/L. Assuming complete nitrification of a Total Nitrogen(TN) concentration of 53 mg/L, as determined in Section III D below, and considering that ammonium typically composes 70-90% of the total nitrogen in septic tank effluent, we find that: 53 mg N/L x 80% =42 mg NH4 NIL x 7..1 mg CaCO3 = 301 mg/L alkalinity required. However, only 232 mg/L of alkalinity exists in the upper groundwater. Therefore the alkalinity in the domestic water supply may be deficient if the TN will be approximately 53 mg/L, and nitrification may be inhibited to a slight extent. B. SURFACE 'WATER INFORMATION Surface water consists of all other water sources originating on the surface of the project, other than f septic system effluent. These sources include rainfall, surface runoff, domestic irrigation and on-site stormwater retention.. The attached San Joaquin County of Public Works - Isohyetal Map indicates 13.5 inches of rainfall to be the Mean Annual Precipitation in the area of the project. There should be no impact to surface waters from septic effluent provided applicable distance requirements as promulgated in the San Joaquin County Sewage Standards, are followed. - . 7 -- Chesney Consulting