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26440,8875,&8925 Thornton Road Project No. 2017-00010 Page 15 <br /> reviewed a recent aerial photograph available from GoogleEarthTM.We counted the clusters <br /> within approximately one square mile of the site, with the assumption each building cluster <br /> has one septic system.Using this method,we determined there are approximately 300 septic <br /> systems per square mile in the immediate vicinity of the site. This is a high amount of septic <br /> systems,with the majority of these systems located within the community of Thornton near <br /> the site. <br /> There are currently no wells located on the parcels to test for nitrate and DBCP on site. <br /> 4.2 Contribution of Rainfall <br /> An estimate of the quantity and quality of rainfall was required for the nitrate loading <br /> analysis. The estimate of deep percolation of rain is based on the average monthly <br /> precipitation of rain fall for Lodi, California, based on the nearest weather station to the site <br /> available. The estimate first determines whether the average monthly precipitation exceeds <br /> average monthly potential evapotranspiration. If so, then the difference is potential deep <br /> percolation. This method does not consider runoff. See Plate 6 for the data and calculation. <br /> Average potential evapotranspiration was obtained from the California Irrigation <br /> Management Information System (CIMIS). The Thornton site is located within <br /> evapotranspiration zone number 12, as well as the Lodi station used in the analysis. The <br /> average rain fall for the Lodi area was obtained from the Western Regional Climate Center <br /> (www.wrcc.dri.edu), and was found to be 17.57 inches per year for the years 1948 through <br /> 2004. <br /> Based on this method, the average deep percolation of rain for the Thornton area is <br /> estimated to be 5.76 inches. The nitrate concentration of rain fall was estimated to be <br /> 1 mg/L-N (Hantzsche and Finnemore, 1992). <br /> 4.3 Current On-Site Sources of Nitrate <br /> The current source of nitrate for the site is the septic system of unknown size for the <br /> three-bedroom residence located at 8875 W. Thornton Road. The septic_system will be <br /> destroyed during the_proposed development. In addition to the existing__stic_system, <br /> groundwater and rainfall-are also recognized as potential current on-site sources of nitrate. <br /> 4.4 Future On-Site Sources of Nitrate <br /> 4.4.1 Quantity and Quality of Domestic Wastewater from Proposed Project <br /> The following discussion is for determining the long-term wastewater flow anticipated from <br /> the existing CFN station and planned Shell service station/mini-mart with fast-food <br /> restaurant for the site, to be incorporated into the nitrate loading analysis. The anticipated <br /> wastewater flow determined is not intended to be used for septic system design, because <br /> septic system sizing includes a peak use factor/surge flow, whereas the numbers discussed <br /> herein are based on a long-term conservative measure of estimated effluent volume. <br /> Petralogix Engineering,Inc. <br /> 26675 Bruella Road,Galt,Ca 95632 <br /> (209)-400-5729 <br /> www.petralogix.com <br />