SITE INFORMATION AND CORRESPONDENCE

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Kennedy/Jenks/Chilton Mr. John Menke California Regional Water Quality Control Board 30 November 1989 Page 3 fuel storage tank. The remaining 4 borings and 3 monitoring wells did not indicated that petroleum hydrocarbons were of a concern. Although other potential contamination sources exist near the Cal -Farm Supply Facility (Pacific Molasses and Port of Stockton) the results of the Preliminary Site Investigation did not indicate that these sites have contributed to the problem previously detected at the site. Task 4 is additional soil sampling to determine the extent of DDT contaminated soil . The described sampling procedure is satisfactory, but you may wish to decrease the number of sampling points south of the facility fence and conduct some sampling at depth in the areas of known contamination in order to estimated the volume of soil needing treatment or removal . I note that you are proposing 1 ppm as a cleanup level as discussed in 14 July 1989 Preliminary Site Investigation Report (page 7, last paragraph) . As noted in the Report, the TTLC is not an action level ; however, the TTLC level of 1 ppm is often proposed as cleanup goal . A more appropriate method of setting goals is to consider potential health effects, routes of exposure, and probable attenuation. Such a process results in a site specific level that usually considers current and potential site use. By applying such a process to the Cal-Farm Supply site, you may be able to justify the proposed 1 ppm level . Until the site is fully characterized, I cannot validate the 1 ppm level as adequate to protect water quality, but I expect that it will be acceptable. Likewise, other pesticide residues at the site should be reviewed and cleanup levels determined. The process of calculating cleanup levels based on toxicities relative to the TTLC for DDT does not result in satisfactory goals because no consideration is given to relative mobility and appropriate toxicity (the TTLC for DDT was based on cumulative toxicity to fish) . Based on my review of the pesticide levels determined to date, I do not anticipate that any other pesticide at the site will displace DDT as the focus for cleanup activities (i .e. , if soils are remediated to address concerns for DDT, no additional soil remediation will be necessary for other pesticides) . A clean-up level of 1 ppm was proposed for the Cal -Farm Supply Stockton Facility so that soils which contain chemicals at concentrations which the State of California considers hazardous (CCR Title 22) would be removed from the site. The EPA, in it's RCRA Facility Investigation (RFI) document (530/ SW-89-031) proposes a health-based action level of 2.1 ppm for DDT in soil based on oral exposure. Site specific information such as dominant site lithology, the low mobility of DDT in the environment, and the depth to groundwater at the site would likely cause this number to rise if a risk assessment was conducted for the Cal -Farm Supply Stockton Facility. However, Cal -Farm Supply wishes to remove soil containing concentrations of DDT which exceed 1 ppm, therefore, a risk assessment was not deemed necessary. Task 5 is disposal of soil containing DDT. Whereas DDT is a "soft-hammer" land ban waste, it will be necessary to demonstrate that no treatment process is