SR0084207_SSNL - Laserfiche WebLink

Home Browse Search

4.2 Description/discussion of any existing and/or potential groundwater contamination issues in the general location of the site: Description of existing or potential groundwater contamination issues in the general location of the site are referred to in Section 4.2 of the Soil Suitability Report prepared by Dillon & Murphy (See Appendix). 4.3 Description of the current use of groundwater at the site and of the future expected use of groundwater as related to the proposed development project: Based on the most recent results from San Joaquin County's "Flood Control and Water Conservation District" report on groundwater from Spring 2018, the estimated depth to groundwater was determined to be 135-145 feet below the surface. This was verified with the California Department of Water Resource's Water Data Library. The results of the historic depth to ground water show that the relative depth has not changed drastically throughout the years. It fluctuates minimally on a yearly basis. The proposed improvements will not have a negative effect on the current depth to ground water as the proposed usage is less than that of agriculture. See appendix for the site's depth groundwater tables and diagrams. 5.0 SOURCES AND CALCULATED IMPACT OF NITRATE TO GROUNDWATER 5.1 Description of all current off-site sources of nitrate to soil and groundwater in the general up gradient area and the contribution of nitrate load from these sources to the project site: Current off-site source of nitrate to soil and groundwater in the general up gradient area and the contribution of nitrate loads are agriculture and neighboring sites with septic systems with minimal to no current impact to the site it's bare ground. 5.2 Description of impact of rainfall contribution of nitrate load to the project site: The impact of rainfall contribution on the project site was obtained to determine the nitrate load. The average monthly precipitation and evotranspiration are required to calculate the site nitrate load. These two values are used to estimate the deep percolation. The deep percolation is estimated by analyzing the difference between the monthly average precipitation and the evotranspiration, when the evotranspiration exceeds the monthly average precipitation. The available evotranspiration was adjusted with an adjustment factor based landscaping on-site. These calculations are attached in the Appendix. The calculations were done for the two proposed 60 acre parcels. The data for the potential evotranspiration water was obtained from the California Irrigation Management Information System (CIMIS). The project is located within an area designated as Zone 12. Based on the values for this area along with the average monthly precipitation values obtained from the Western regional Climate Center (Station 262) for the Linden region an estimate of the deep percolation of rain for the project was determined. The results for the deep percolation at the site were 4.49 in./year for the 60 acre parcels. The nitrate concentration is estimated to be about 1 mg/L-N. (Hantzche and Finnemore, 1992). 4