SR0084018_SSNL - Laserfiche WebLink

Home Browse Search

20 July 2021 AdvancedGe- Project No. 21-6486 An Employee-Owned Company Page 11 of 15 " the subject property, the site should not impact the subject property. The review did not reveal any other sites of environmental concern within a half-mile radius of the site. Based on the information reviewed, there is no existing or known groundwater contamination at the site and the potential for groundwater contamination is de minimis. 8.3. CURRENT AND FUTURE USE OF GROUNDWATER AT THE SITE The existing water supply wells at 12511 Mundy Lane appear to conform to DWR and EHD standards. The wells are currently utilized as the potable water sources for the property and will continue to be used to supply the subject property with a domestic water source. 9.0. IMPACT OF NITRATE TO GROUNDWATER Due to the planned residential use of the property and the potential for nitrate leaching into the groundwater from the proposed septic system, a nitrate loading analysis for the future use of the septic system is required by the EHD. 9.1. CURRENT OFF-SITE SOURCES OF NITRATE Septic systems and agriculture are sources of nitrates in the area of the site. The property is bordered by residential and agricultural land, which might provide a nitrate source. There are several residences within 1,000 feet of the site. 9.2. IMPACT OF RAINFALL CONTRIBUTION TO NITRATE LOAD The rainfall of the area has been estimated for the nitrate loading analysis. Deep percolation is estimated by calculating the average monthly rainfall and evapotranspiration of the site area. If average monthly rainfall exceeds average monthly potential for evapotranspiration (ETo) there is a potential for deep percolation without consideration for runoff. Average potential ETo was estimated from data obtained from the California Irrigation Management Information System (CIMIS) Manteca Station #70. Manteca Station #70 has been collecting ETo and precipitation data since January 2014. Deep percolation (average annual rainfall recharge) was estimated utilizing the monthly ETo and precipitation data collected from Manteca Station #70 between 2015 and 2020. The annual rainfall average for the area between 2015 and 2020 was 11.52 inches (CIMIS); the annual ETo average ranged from 0.48 inches in 2020 to 4.41 inches in 2017. The estimated deep percolation (R) was determined by calculating the average of the ETo between 2015 and 2020. The estimated deep percolation (R) is 3.20 inches (Appendix E).