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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 «g/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. The laboratory analytical results are attached as Appendix 5 of this report. Soil Profile and Geologic Information The Site is mapped on the Preliminary geologic map showing Quaternary deposits of the Lodi quadrangle, California (Marchand and Atwater, 1979). It is depicted within a map unit of the Modesto Formation upper member, "arkosic alluvium forming Mokelumne River alluvial fan; chiefly sand... probably glacial outwash." A small area on the west side of the Site is described as "arkosic sand forming low dunes on the Mokelumne River fan and in the Delta" (Plate 7). The surface and near surface soils located at the Site are reported by the Soil Survey of San Joaquin County, California (USDA, 1992) to be composed of Kingdon fine sandy loam, Tokay fine sandy loam, and Tujunga loamy sand (Plate 8). The table below presents some selected properties of these soils: Table 1. Selected Properties of On-Site Soils (USDA, 1992) Soil Name Depth Unified Soil Salinity Soil Perme- Septic tank and Map (in) Classification mmhos/cm Reaction ability absorption Symbol pH (in/hr) fields Kingdon 0-5 Fine sandy loam, SM <2 5.6-7.3 2.0-6.0 Moderate: fine sandy 5-14 Fine sandy loam; SM <2 6.1-7.3 2.0-6.0 wetness, loam, 0-2% 14-28 Sandy loam, fine sandy <2 6.1-7.3 2.0-6.0 peres slowly slopes, loam; SM 189 28-42 Fine sandy loam, loam; <2 6.1-7.8 0.6-2.0 SC-SM, CL-ML 42-61 Fine sandy loam, sandy <2 6.6-8.4 2.0-6.0 loam, coarse sandy loam; SM LOGE 1505 Page 5