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Nitrate Loading Study Flag City#4 ■ Lodi, California Irerracon September 20, 2018 ■Terracon Project No. NA187043 2.2 Potential Ground Water Contamination Issues The presence of nitrates is not uncommon in shallow groundwater aquifers in San Joaquin County and other parts of the Central Valley. Nitrate in groundwater occurs as a result of the application of fertilizers, livestock waste, and untreated septic tank waste. Nitrate is mobile and often accumulates in the shallow groundwater zones. In the early 1900s, natural levels of nitrate in groundwater were measured in forty-three (43)wells throughout the Sacramento Valley by Kirk Bryan (1923). It was thought that groundwater at that time was close to "natural" conditions. Based on the work by Bryan, it is estimated that under "natural' conditions, groundwater concentration containing nitrate is no more than about 13.5 mg/L-NO3 (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 (1,2-dibromo-3-chloropropane) is a nematicide 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 moderate based on the agricultural land use and anticipated depth to groundwater between 14 and 40 feet bgs. 2.3 Current and Future On-Site Ground Water Uses One groundwater well is currently located on the site. It is our understanding the groundwater well is intended to be used for the proposed development. On August 30, 2018 two groundwater samples (GW-1 and GW-2) were collected from a tank 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 in a clean glass 40 ml amber VOA preserved with ascorbic and meleic acid and analyzed for DBCP (1,2-Dibromo-3-chloropropane) by EPA Extraction Method E524.3. Both groundwater samples GW-1 and GW-2 reported below laboratory reporting limits of 0.10 mg/L for nitrate as N and 0.010 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 and eastern properties consist of commercial/industrial facilities. The adjoining western and southern properties consist of agricultural land. Terracon assumes the Responsive ■ Resourceful ■ Reliable 5