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l <br /> li f Al - <br /> t � 1 <br /> { October 12,2000' - I <br /> Job Number:LGOO-312 <br /> Page 5 <br /> Sacramento Valley by Bryan_z It was thought that ground water at that time was close to <br /> `statural" conditions. Based on the work by Bryan, it is estimated that.under"natural" conditions, <br /> ground water concentration containing nitrate is no more then about 3 to N. Areas having 5.5 <br /> mg/LN or more are those in which nitrate concentrations may be increasing. <br /> DBCP was not detected in the water sample. DBCP is a nematocide and soil fumigant for <br /> vegetables, and grapes.;-It is thought to cause health problems consisting of kidney damage, liver <br /> damage, and cancer. The use of DBCP was discontinued in 1979. The Environmental Protection <br /> Agency(EPA) set the maximum contaminate limit(MCL)at(}.2 parts per billion(ppb) because <br /> the EPA believes that given present technology and resources;this is the lowest level to which <br /> water systems can reasonably be required to remove this contaminate should it occur in drinking <br /> water.' <br /> VL GEOLOGY; SOIL,AND PERCOLATION TEST <br /> The geologie'literature indicates that the surficial deposits,near the site are reported to be <br /> composed of the Pleistocene age (about 10,000 to 2-million years old)Modesto Formation <br /> unconformably overlying portions of the older Pliocene age(about 2-million to 5-million years <br /> old)Laguna Formation(Plate 6),5' The Modesto Formation is widespread in the lower elevations <br /> of the Central/Sacram' ento Valleys and the lower western Sierran foothills. The Modesto <br /> 'Formation is generally composed of river alluvium, alluvial terraces, alluvial fans and abandoned <br /> channel ridges.' The Modesto Formation often consists of tan and light-gray gravely sand, silt, <br /> � Y <br /> z Bryan,K., 1923,Geology and ground-water resources of Sacramento Valley of California: U-S. <br /> i Geological Survey Water.-Supply Paper 495, 285p_ <br /> 3 Hull,L.C., 1984,Geochemistry of Ground Water in the Sacramento Valley,California:U.S_ Geological <br /> Survey Professional Paper 1401-B. i <br /> a'EPA, 1999,Drinking water and health,National Primary prinking Water Regulations,consumer fact <br /> E sheet on:DTSR0M0gMOROPRP0ANE_ Internet: http://www.epa.gov./OGWDW/dwh/c-soctdibron-roc.html 1 { <br /> { 5 Wagner,D.L.,Bortugno,E.J.,and Mciunldn,RD., 1990,Geologic Map of the San Francisco-San Jose i <br /> Quadrangle. California Department of Conservation,Division of Mines and Geology Map No. 5A(Geology). <br /> i <br /> Scale 1:250,000_ <br /> ' Helley,E.J.;and Harwood,D.S., 1985, Geologic Map of the Cenozoic deposits of the Sacramento <br /> Valley and Northern Sierran Foothills, California. U.S-G-S.Misc.Field Studies Map MF-1790, Scale 1:62:500. <br /> oIRSQy <br /> k fs pQ� i <br />