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05 November 2014 <br /> AGE Project No. 14-3119 <br /> Page 11 of 17 <br /> 8.2. EXISTING OR POTENTIAL GROUNDWATER CONTAMINATION <br /> The immediately adjacent and outlying land use for the parcel is agricultural in nature. <br /> There are potential groundwater contamination issues associated with agricultural uses <br /> and septic systems. A review of the DTSC Envirostor Database revealed one LUST site <br /> within a two-mile radius of the site. The site has been closed for more than 10 years and <br /> is located more than one-mile from the subject parcel. <br /> 8.3. CURRENT AND FUTURE USE OF GROUNDWATER AT THE SITE <br /> The newly installed water supply well conforms to DWR and EHD standard and will be <br /> used to supply the domestic (including the proposed multi use buildings) uses at the <br /> property <br /> 9.0. IMPACT OF NITRATE TO GROUNDWATER <br /> Due to the proposed commercial use of the property and the potential for nitrate leaching <br /> into the ground water from the existing septic systems, a nitrate loading analysis for the <br /> future use with a separate septic system has been required by the EHD. <br /> 9.1. CURRENT OFF-SITE SOURCES OF NITRATE <br /> Septic systems and agriculture are sources of nitrates in the area of the site. The property <br /> is boarded by agricultural lands which might provide a nitrate source. There are three to <br /> four other residences within 1,000-feet of the site. <br /> 9.2. IMPACT OF RAINFALL CONTRIBUTION TO NITRATE LOAD <br /> The rainfall of the area has been estimated for the nitrate loading analysis. Deep <br /> percolation is estimated by calculating the average monthly rainfall and <br /> evapotranspiration of the site area. If average monthly rainfall exceeds average monthly <br /> potential for evapotranspiration (ETo) there is a potential for deep percolation without <br /> consideration for runoff. Average potential ETo was estimated (annually at 60) from data <br /> obtained from the California Irrigation Management Information System (CIMIS) Tracy <br /> Station #167. The average rain fall data for the area was gathered from the Western <br /> Regional Climate Center summary. The averages were calculated based on data <br /> collected between 1961 to 1990, the yearly rain fall average for the Tracy area was 13 <br /> inches. <br /> Advanced GeoEnvironmenfal,Inc. <br />