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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 ug/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 />Bellota quadrangle, California (Marchand and Bartow, 1979). The Site is depicted <br />within a map unit of the Modesto formation upper member, described as "arkosic <br />alluvium forming Mokelumne River terraces and alluvial fan, chiefly sand with minor <br />gravel and silt; probably glacial outwash" (Plate 8). <br />The surface and near surface soils located at the Site are reported by the USDA Web <br />Soil Survey to be composed of Tokay fine sandy loam (Plate 9) (USDA, 2019). The <br />table below presents some selected properties of this soil: <br />Table 1. Selected Properties of On -Site Soils (USDA, 1992) <br />Soil Name Depth Unified Soil Salinity Soil Perme- Septic tank <br />and Map Reaction ability absorption <br />Symbol (in) Classification mmhos/cm pH (in/hr) fields <br />Tokay fine <br />0-19 Fine sandy loam; SM <2 6.1-7.8 2.0-6.0 Slight <br />sandy loam, <br />19-45 Fine sandy loam, sandy <2 6.1-7.8 2.0-6.0 <br />0-2% <br />loam; SM <br />slopes, <br />45-60 Fine sandy loam, sandy <2 6.1-8.4 2.0-6.0 <br />256 <br />loam, coarse sandy <br />loam; SM <br />Note: The table descriptions do not necessarily reflect site-specific soil properties. See description of the map unit for <br />composition and behavior characteristics of the map unit. <br />LOGE 2212 Page 5 <br />