SITE INFORMATION AND CORRESPONDENCE FILE 2

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Membrandurri CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION 3443 Routier Road Phone: (916) 361-5600 Sacramento, CA 95827-309$ ATSS: B-495-5600 TO: ( Ij Antonia Vorster :� FROM: Gary A. Reents, .P,E. _ 1 Senior Engineer Project Engineer DATE: 10 February 1988 SIGNATURE; SUBJECT: TEICHERT & SONS STOCKTON, SAN JOAQUIN COUNTY - LBME Corporation (Elder Engineering) submitted a Soil and Ground water Assessment Report, dated 20 December 1987, on behalf of Teichert & Sons. The LBME Report document actions taken at the site since the initial Soil and Ground Water Assessment Report dated 27 April 1987, -was submitted by Kleeinfe' lder. The latest Report describes soil excavation and aeration; monitoring well instal- 1 ation and sampling; analytical results; and proposed . remedial actions for contaminated ground water and soils. . Proposed remedial actions consist of an extraction well , air stripping, and discharge to the storm drain for ground water; vapor extraction with venting to the atmosphere for remaining soil contamination. The primary problem with the Report and the proposed actions is that neither the :I extent of contamination in the soil nor ground water has been defined (an issue discussed in our previous comments of..17 June 1987) . For soils, sample results . indicate that significant levels exist �to the north and south of the excavation. Once an estimate of the contamination extent is made, the area of influence of the vapor extraction system must be determined to ensure effectiveness. One possible approach is to use soil vapor .points '-for .both soil .gas sampling and pressure ; monitoring. Once the extent and effectiveness of the system is determined, and a permit has been obtained from the San Joaquin Air Pollution Control District, we can approve the system. Far groGnd water, sample resultsYgfor monitorinq"we"tis 1; 2,"3; aritl 5 all -ezc`eed` the State Action Level for Benzene. Monitoring well 1 also exceeds the Action Level for Toluene and,'Xyiene. This indicates a potential contamination plume of a minimum of 60 foot radius. The vertical extent of contamination is unknown since } all monitoring wells are water table wells. The proposed single extraction well r is estimated to have a radius of influence of 25 feet which will not be adequate. The proposed ground water treatment system appears adequate,; although the F projected flow volumes are probably 16w since the proposed extraction system . appears undersized. The proposed discharge from the air stripper;` however, will require waste_ discharge requirements. - "�A Report of Waste Discharge, filing fee, � and evidence of local permits, primarily from. the Air Quality Management District, I are required before requirements can be Issued,