SR0083744_SSNL - Laserfiche WebLink

Home Browse Search

Nitrate was detected in the sample at a concentration of 6.0 mg/L-N. DBCP was not detected in the water sample. The laboratory analytical results are attached as Appendix 5 of this report. Nitrate is commonly detected in shallow ground water aquifers of the Central Valley. Application of fertilizers, livestock waste, and untreated septic tank waste can all contribute to nitrate in ground water. Nitrate is mobile and tends to accumulate in shallow ground water zones. Based on work in the Sacramento Valley from the early 1900s, it is estimated that under "natural" conditions, ground water contains nitrate at concentrations no more then about 3 mg/L-N. Nitrate may be increasing in areas with concentrations of 5.5 mg/L-N or more (Hull, 1984). The US EPA has set the Maximum Contaminant Level (MCL) for nitrate at 10 mg/L-N. Although nitrate is a naturally-occurring compound necessary for plant growth, it can cause health problems when present at high levels in drinking water. The most common health effect of nitrates in water is methemoglobinemia, or blue baby syndrome, which results in reduced oxygen supply to vital tissues. Pregnant women and certain others can also develop methemoglobinemia. Symptoms include a bluish color of the skin, as well as headache, dizziness, weakness, and difficulty breathing. Ingestion of high levels of nitrates over time can also lead to gastric problems. DBCP is a nematocide and soil fumigant for vegetables and grapes. It is known to cause male reproductive effects and is classified as a probable human carcinogen. Most domestic use of DBCP was discontinued in 1977 through 1979. The US EPA set the MCL at 0.2 parts per billion (ppb, equivalent to ig/L) because it believes that given present technology and resources, this is the lowest level to which water systems can reasonably be required to remove this contaminant should it occur in drinking water. The Maximum Contaminant Level Goal (MCLG) for DBCP is zero. Soil Profile and Geologic Information The Site is depicted on the Preliminary geologic map of Cenozoic deposits of the Be/Iota quadrangle, California (Marchand & Bartow, 1979). The Site is depicted within a map unit of the Riverbank formation middle unit, described as "arkosic alluvium forming Mokelumne River terraces and alluvial fan; chiefly sand; probably glacial outwash" (Plate 9). The surface and near surface soils located at the Site are reported by the USDA Web Soil Survey to be composed of BrueIla sandy loam and San Joaquin loam, thick surface (Plate 10) (USDA, 2020). The table below presents some selected properties of these soils: LOGE 2062 Page 5