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1900s, it is estimated that under "natural" conditions, ground water contains nitrate at <br />concentrations no more then about 3 mg/L-N. Nitrate may be increasing in areas with <br />concentrations of 5.5 mg/L-N or more (Hull, 1984). The US EPA has set the Maximum <br />Contaminant Level (MCL) for nitrate at 10 mg/L-N. <br />Although nitrate is a naturally-occurring compound necessary for plant growth, it can <br />cause health problems when present at high levels in drinking water. The most <br />common health effect of nitrates in water is methemoglobinemia, or blue baby <br />syndrome, which results in reduced oxygen supply to vital tissues. Pregnant women <br />and certain others can also develop methemoglobinemia. Symptoms include a bluish <br />color of the skin, as well as headache, dizziness, weakness, and difficulty breathing. <br />Ingestion of high levels of nitrates over time can also lead to gastric problems. <br />DBCP is a nematocide and soil fumigant for vegetables and grapes. It is known to <br />cause male reproductive effects and is classified as a probable human carcinogen. <br />Most domestic use of DBCP was discontinued in 1977 through 1979. The US EPA set <br />the MCL at 0.2 parts per billion (ppb, equivalent to g/L) because it believes that given <br />present technology and resources, this is the lowest level to which water systems can <br />reasonably be required to remove this contaminant should it occur in drinking water. <br />The Maximum Contaminant Level Goal (MCLG) for DBCP is zero. <br />Soil Profile and Geologic Information <br />The Site is depicted on the Preliminary geologic map showing Cenozoic deposits of the <br />Be/Iota quadrangle, California (Marchand and Bartow, 1979). The Site is depicted <br />within a map unit of the Riverbank formation lower unit, described as "arkosic alluvium, <br />probably glacial outwash, and locally derived sandy alluvium, chiefly sand" (Plate 11). <br />The surface and near surface soils located at the Site are reported by the USDA Web <br />Soil Survey to be composed of BrueIla sandy loam and Bruella sandy loam, hard <br />substratum (Plate 12) (USDA, 2019). The table below presents some selected <br />properties of these soils: <br />LOGE 1850 Page 5