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Nitrate Loading Analysis BSK Job E21-002-01B <br />2482 Carpenter Road July 13, 2021 <br />Stockton, California P a g e | 4 <br /> <br />3.2 Groundwater Quality Data: <br /> <br />Nearby and recent water quality data was available from only one source, Site Number: <br />375545121141601 Site Name: 001N007E17N001M Operated by the USGS. This well is approximately <br />2,640 feet to the north-northeast of the site, 170 feet north of Duck Creek. The nitrate concentration of <br />this groundwater sample was 2.11 milligrams per liter (mg/L). The analytical data from the USGS for this <br />well is included in Appendix D. The proximity to the creek may impact the concentrations of nitrate and <br />other constituents compared to the site. <br /> <br />3.3 Current Groundwater Use at the Site: <br /> <br />Currently the site is split approximately in half with the northern section being occupied by three buildings <br />being used as an Adult Care Facility and the southern section is an undeveloped field that is being <br />developed to expand an electrical substation that is adjacent to the western edge of the site. Currently, <br />the site has two septic/wastewater leech line areas. The future development of the site is to replace the <br />previous wastewater septic/leech lines and have a new, commercial septic system installed on the <br />northeastern edge of the site for the three existing buildings. Discharge and use should remain the same <br />as the adult care facility is not planned to be expanded or altered. The only change will be the removal of <br />the previous septic/leech line system and the installation of a commercial septic system. <br /> <br /> <br />4. SOURCES AND CALCULATED IMPACT OF NITRATE TO GROUNDWATER <br /> <br />4.1 Current Off-Site Sources of Nitrate to Soil and Groundwater in General Up Gradient <br />Area: <br /> <br />Upgradient from the site is mixed residential and commercial buildings. It is unknown whether the <br />residential buildings to the west are connected to the city sewer system or discharge to a septic/leech <br />system. If the residential area is connected with the city sewer system, the contribution to nitrate load to <br />the site would be less than if the homes discharges to septic/leech systems. <br /> <br />Downgradient and cross gradient agriculture/orchards can be a source of nitrate-nitrogen in soil and <br />groundwater due to fertilizer use. <br /> <br />4.2 Impact of Rainfall Contribution of Nitrate Load to Project Site: <br /> <br />Publicly Available Climate Data: Climate data from 1991 to December 2021 from Station GHCND: <br />USW00023237 (Appendix A) was compiled from the NOAA website (NOAA, 2021). Information used in <br />the nitrate loading analysis is presented below: <br /> <br />• The average rainfall for Stockton ranges from 0.02 inches in June through September to 1.36 <br />inches in February.