SITE INFORMATION AND CORRESPONDENCE

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W.T.Nickerson July 14, 1997 Page 2 "3. The report contains an outdated and inaccurate water quality criterion for 1,2-DCP. As listed in staff report A Compilation of Water Quality Goals(July 1995; updated April 1996),the following criteria have been established for 1,2-DCP: California Primary MCL: 5 µg/1 USEPA Primary MCL: 5 µg/1 USEPA MCL Goal: zero Calif Recommended Public Health Level (proposed): 541 USEPA Health Advisory(for toxicity other than cancer risk): 90 µg/1 Cal/EPA Cancer Potency Factor(1-in-a-million cancer risk) 0.56 µg/1 USEPA IRIS (1-in-a-million cancer risk) 0.5 µg/1 USEPA Health Advisory (probably human carcinogen) 0.5 µg/l" The water quality criterion presented in the Executive Summary was the State and Federal Maximum Contaminant Level (MCL), cited as S µg/1. This corresponds with the California Primary MCL and the USEPA MCL, as listed, and is also the same as the California Recommended Public Health Level (proposed) on the list. We are aware that the human health risk assessment process is designed to arrive at an acceptable cleanup criterion which is site specific. This being so, none of the five different criteria listed will actually be arbitrarily implemented onsite. "1.0 Introduction 1. The maximum listed concentration of 1,2-DCP is in error." As noted above, we stand corrected. "2. Site investigations have shown that the nitrates and 1,2-DCP in the groundwater are due to the disposal of waste products into the oil-water separator and three dry wells,as well as the disposal of rinsewater to the evaporation ponds." These additional former potential sources are noted. "2.4 Groundwater Chemis rt y I think it is important to relate the chemicals that have been found in the groundwater to regulatory limits, as this shows whether there is a basis for further environmental work. The report does not do this, so I have summarized the information in the following table. (See Original Review Comments, attached, for table entitled Chemicals detected and levels of concern. 1905 N. Broadway. Stockton) As the table shows, there are ten chemicals which have been detected at concentrations greater than the regulatory level of concern. The evaluation of remedial alternatives needs to focus on all the chemicals, not just on 1,2-DCP."