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15 December 2020 AdvancedGeo <br /> Project No. 05-1278 An Employee-Owned Company <br /> Page 10 of 14 <br /> including leaking underground storage tanks, septic systems, agricultural activities, <br /> dairies, and stormwater infiltration. <br /> A review of the DTSC EnviroStor Database and the Geotracker Web site revealed three <br /> (3) LUST sites, including the subject property, within a half-mile radius of the site. The <br /> LUST sites have been closed since 2012 and 2016. Based on the status of the sites and <br /> the direction from the subject property, the sites should not impact the subject property. <br /> The LUST investigation at the subject property was performed by AGI between 1998 and <br /> 2012. Based on all historical data and remediation performed at the site, AGI concluded <br /> that petroleum hydrocarbons remaining beneath the site pose minimal risk to human <br /> health as no direct exposure route to the residual soil is complete and soil vapor samples <br /> collected near the main structure at the site posed no threat to indoor air quality. The site <br /> was closed with residual impact left in place. <br /> 8.3. CURRENT AND FUTURE USE OF GROUNDWATER AT THE SITE <br /> There is currently no water well on the property. The property is supplied with potable <br /> water by the San Joaquin County municipal well system and will be for the foreseeable <br /> future. <br /> 9.0. IMPACT OF NITRATE TO GROUNDWATER <br /> Due to the planned use of the property and the potential for nitrate leaching into the <br /> groundwater from the proposed septic system, a nitrate loading analysis for the future <br /> use of the septic system is 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 bordered by commercial land, and is in the general vicinity of agricultural land, which <br /> might provide a nitrate source. <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 from data obtained from <br /> the California Irrigation Management Information System (CIMIS) Staten Island Station <br />