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Nitrate Loading Study Irerracon Guillermo Ramirez Property a Ripon, California April 29, 2019 rd Terracon Project No. NA197019 The groundwater flow direction and the depth to shallow, unconfined groundwater, if present, would likely vary depending upon seasonal variations in rainfall and other hydrogeological features. Without the benefit of on-site groundwater monitoring wells surveyed to a datum, groundwater depth and flow direction beneath the site cannot be directly ascertained. 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 (dibromochloropropane) 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. EDB (ethylene dibromide) was used in gasoline to prevent lead deposits and build up. It was also used in pesticides and fumigants. Exposure to EDB is linked to many adverse health effects stemming from organ damage to cancer. 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 to high based on the agricultural land use and anticipated depth to groundwater between 45 to 68 feet bgs. 2.3 Current and Future On-Site Ground Water Uses It is our understanding there are no groundwater wells located on the site; therefore, a groundwater sample was not collected. We further understand the site will be developed with a groundwater supply well for the future residential use. 3.0 SOURCES AND IMPACT OF NITRATE TO GROUNDWATER 3.1 Current Off-Site Sources of Nitrate The adjoining properties consist of agricultural land primarily orchards and 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 Responsive ■ Resourceful ■ Reliable 5