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71. ANAALYSIS OF ON-SITE DOMESTIC WELL The domestic well that serves the DeAngelis homesite was purged by opening the hose bibbs located in the back of the house and cycling the pump three times before sampling. This ensured that aquifer formation water was sampled and not stagnant well water. The sample was taken from the hose bibb located in the back patio and placed in a cooled ice chest. The sample was then delivered to A &L Western Agricultural Laboratories under the attached Chain of Custody. The nitrate concentration was determined to be 42 ppm nitrate (as NO3). The Maximum Contaminant Level (MCL) for nitrate (as NO3) is 45 ppm, or 10 ppm as nitrate-nitrogen. For comparison purposes, the nitrate test results from a nearby domestic well are denoted below in Table 4. Since this nearby well had a DBCP/EDB test result of BDL (Below Detectable Limits), testing of the DeAngelis well for DBCP was waived by EHD staff. This increase in nitrate concentration between the DeAngelis well and the nearby domestic well one-half mile to the east may be attributable to higher upgradient septic system density to the DeAngelis well than the other referenced well. A summary of the water well test results discussed above are as follows: TABLE 4 NITRATE CONCENTRATIONS- DeANGELIS DOMESTIC WELL AND NEARBY DOMESTIC WELL DeANGELIS DOMESTIC WELL NEARBY DOMESTIC WELL 42 ppm as NO, 38 ppm as NO, 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 indicate 9 inches QL ZaiD&D to be the Mean Annual Precipitation in the area of the project. If a second unit dwelling is built on Parcel 1, a percentage of the land surface will be impermeably covered with a structure, concrete, etc. This will have an attenuating effect from surface water 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 system for a second unit dwelling, lawns, and landscaping._Domestic irrigation rechar-e can_account for 2 allons of water/da /reside e n and summer months (approx. 6 mos. out of the yr). Excessive lawn and landscape watering can lead to nitrogen leaching, and runoff to open areas. However, conversely, the groundwater pumped either by the CSA-44 wells, or by on-site domestic wells, and used for domestic irrigation can reduce the mass balance of nitrate since all plants readily use nitrate as a food source. This is provided that fertilizer is carefully applied to lawns, gardens and landscaping, if at all. For example: 42 ppm NO3 as tested for the DeAngelis well=42 ppm x 0.612 =25.7 lbs of NO3/ac ft of water. If an average of 750 allons of domestic irri anon water is used each day for six months= 180 days x 750 gals/day= 135,000 gals (roughly % ac-ft of water). 25.7 lbs NO3 x 0.5 = 13 lbs NO3 applied by % ac-ft of domestic irrigation water. Kentucky blue grass requires 124 lbs Nlac/yr. Therefore, depending on the size of the landscaped area, domestic irri anon �t 42 nnm NO,�may su 1 sufficient nitro en required by this grass without or nitro en fertilizers. Page-7- Chesney Consulting