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Nitrate Loading Study Nerracon Arellano Property ; Stockton, California April 26, 2019 Terracon Project No. NA187058 "natural" conditions, groundwater concentration containing nitrate is no more than about 13.5 milligrams per liter(mg/L) nitrate (NO3) or (3 mg/L-N). Areas having 24.75 mg/L-NO3 (5.5 mg/L- N) or more are those in which nitrate concentrations may be increasing (Hull, 1984). DBCP (dibromochloropropane) is a nematocide and soil fumigant for vegetables and grapes. It is thought to cause health problems consisting of kidney damage, liver damage, and cancer. The use of DBCP was discontinued in 1979. Agricultural land use and septic systems in the area should be considered potential groundwater contamination sources. The concerns for groundwater contamination in this area are deemed low based on the anticipated depth to groundwater greater than 90 feet bgs. 2.3 Current and Future On-Site Ground Water Uses A domestic groundwater well located south of the existing residence well provides water for the site. The groundwater well will remain in use for the existing and proposed development. On February 26, 2019 two groundwater samples (GW-1 and GW-2) were collected from an exterior faucet connected to the onsite groundwater well and submitted on ice to McCampbell Analytical Inc. for analysis. Sample GW-1 was collected into a clean unpreserved plastic 125 milliliter(ml) bottle and analyzed for nitrate as N by EPA Extraction Method E300.1. Sample GW -2 was collected into two clean glass 40 ml amber VOA preserved with ascorbic and meleic acid and analyzed for DBCP (1,2-Dibrom 3-chloropropane) by EPA Extraction Method E524.3. Nitrate as N was reported at 4.7 mg/ groundwater sample GW-1 which is below the MCL of 10 mg/L N. Groundwater 'sam-pled�(GW-2 reported below laboratory reporting limits of 0.020 micrograms per liter (ug/L)for DBCP. 3.0 SOURCES AND IMPACT OF NITRATE TO GROUNDWATER 3.1 Current Off-Site Sources of Nitrate The adjoining northern property consists of an apparent utility followed by agricultural land. The adjoining eastern and southern properties consist of rural farm structures and/or residences. Terracon assumes the farm structures and/or residences are connected to individual septic systems based on the absence of municipal sewer systems in the area as reported on the San Joaquin County District Viewer. Therefore, off-site sources of nitrate include septic systems, agricultural land use, and natural processes. The DWR Water Data Library online records were searched for wells potentially containing elevated nitrates; however, there was no information regarding nitrates in the wells listed on the website. The State Water Resources Control Board Website did not identify nitrate impacted groundwater wells within 2,000 feet of the site. Responsive a Resourceful a Reliable 5