Laserfiche WebLink
02 March 2023 AdvancedGeo <br /> Project No. 23-7124 An Employee-Owned Company <br /> Page 10 of 14 <br /> Based on the information reviewed, there is the potential for groundwater contamination <br /> at the site. However, based on the surrounding land use, the proposed development and <br /> planned site use, it is AGI's opinion that impact from the nearby sites is de minimis. <br /> 8.3. CURRENT AND FUTURE USE OF GROUNDWATER AT THE SITE <br /> Groundwater beneath the site is currently not utilized and will not be utilized as the <br /> domestic water source for the subject property. The subject property will be provided <br /> potable water from the City of Lathrop. <br /> 9.0. IMPACT OF NITRATE TO GROUNDWATER <br /> Due to the planned commercial use of the property and the potential for nitrate leaching <br /> into the groundwater from the proposed septic system, a nitrate loading analysis for the <br /> 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 commercial, agricultural, and residential 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) Manteca Station #70. <br /> Manteca Station #70 has been collecting ETo and precipitation data since January 2014. <br /> Deep percolation (average annual rainfall recharge) was estimated utilizing the monthly <br /> ETo and precipitation data collected from Manteca Station #70 between 2018 and 2022. <br /> The annual rainfall average for the area between 2018 and 2022 was 10.93 inches per <br /> year (CIMIS); the annual ETo average ranged from 0.48 inches in 2020 to 6.43 inches in <br /> 2022. The estimated deep percolation (R) was determined by calculating the average of <br /> the ETo between 2018 and 2022. The estimated deep percolation (R) is 3.39 inches <br /> (Appendix F). <br />