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19 May 2021 <br />Project No. 21-6435 <br />Page 9 of 14 <br />8.2. EXISTING OR POTENTIAL GROUNDWATER CONTAMINATION <br /> <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 /> <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 /> <br /> <br />8.3. CURRENT AND FUTURE USE OF GROUNDWATER AT THE SITE <br /> <br />There are no immediate plans to use groundwater at the site. Potable water is currently <br />supplied by a public water municipality. <br /> <br /> <br />9.0. IMPACT OF NITRATE TO GROUNDWATER <br /> <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 /> <br /> <br />9.1. CURRENT OFF-SITE SOURCES OF NITRATE <br /> <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 /> <br /> <br />9.2. IMPACT OF RAINFALL CONTRIBUTION TO NITRATE LOAD <br /> <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.