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19 May 2021 AdvancedGeo <br /> Project No. 21-6435 An Employee-Owned Company <br /> Page 9 of 14 <br /> 8.2. EXISTING OR POTENTIAL GROUNDWATER CONTAMINATION <br /> The immediately adjacent and outlying land use for the parcel is residential/commercial. <br /> Potential groundwater contamination can occur from several sources including leaking <br /> underground storage tanks, septic systems, agricultural activities, dairies, and stormwater <br /> infiltration. <br /> A review of the DTSC EnviroStor Database and the Geotracker Web site revealed <br /> seven (7) LUST site within a half-mile radius of the subject property. The LUST sites have <br /> been closed for over ten years and based on the status of the site and the distance and <br /> direction from the subject property, the site should not impact the subject property. The <br /> review did not reveal any other sites of environmental concern within a half-mile radius of <br /> the site. Based on the information reviewed, there is no existing or known groundwater <br /> contamination at the site and the potential for groundwater contamination is de minimis. <br /> 8.3. CURRENT AND FUTURE USE OF GROUNDWATER AT THE SITE <br /> There are no immediate plans to use groundwater at the site. Potable water is currently <br /> supplied by a public water municipality. <br /> 9.0. IMPACT OF NITRATE TO GROUNDWATER <br /> Due to the planned residential/commercial use of the property and the potential for nitrate <br /> leaching into the groundwater from the existing septic system, a nitrate loading analysis <br /> for the future 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 residential land, and is near agricultural land, which might provide a nitrate <br /> source. There are several 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 from data obtained from <br /> the California Irrigation Management Information System (CIMIS) Staten Island Station <br /> #242. Staten Island Station #242 has been collecting ETo and precipitation data since <br /> November 2015. <br />