SITE INFORMATION AND CORRESPONDENCE_FILE 1

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Chevron Pipeline Co.,Dividend Prope,�.y -2- 7 March 1996 bioremediation is only one of many remedial methods that may be appropriate for a given site. Passive-bioremediation is not a"do nothing" alternative. Proper site characterization and monitoring are needed to clearly demonstrate the applicability and progress of this remedial metho(i. 6) A mass balance of initially-released material (the mass of hydrocarbons that existed at the site during initial investigations and at present) would add to'the discharger's assessment of the success of the passive bioremediation method. How long ago did the leak occur? 7) Is passive bioremediation the best method for hydrocarbon removal at this site? Why? What of her methods are available and how would their success be compared with the method chosen? Summarize what other remedial actions have been taken since the discovery of contamination at the site (e.g., soil removal, free product skimming, ground water pumping) and the rationale for not following the active measures proposed in November 1993. 8) How does the monitoring performed at the site to date demonstrate the success of the chosen rc medial method in capturing the entire plume? Are some data missing (e.g., down-gradient o:'MW-13)? 9) Background levels have not yet been achieved at the site. How long is it expected to take for tle chosen remedial method to reach beneficial use protective water quality limits? How long to reach background levels? How do these times compare with existing and potential future beneficial use patterns in the area affected by the release? 10) Geomatrix'response to this item indicates that they consider this to be a"low-risk soil case." I 3o not agree. Since pollutants at this site have been detected and continue to exist in waters o;`the State at levels that would impair beneficial uses of these waters, the case is not "soil oily." The site may be "low-risk"; however, documentation of the risk to existing and probable beneficial uses of waters of the State has not been clearly nor completely di;monstrated in a manner consistent with that required by this agency for other similar sites (i.e., leaking underground tanks per the Tri-Regional Recommendations, Appendix B). The ir:formation requested in our 1 February 1996 letter should clarify the extent of risk to water. Well Logs and Geologic Cross Section Several monitoring well logs were not submitted. The logs submitted for monitoring wells MW-8, -11, -1:!, -13, -14,-15, -16, -17, -18 and-19, prepared in August 1991, are rudimentary and incomplete. Lithologic information is incomplete. Well screen intervals and other drilling and well construction details are missing, as is information on initial and static water levels. The geologic cross section is helpful in demonstrating what is known about the site's lithology from monitoring well logs. Sandy zones are interbedded with the more prevalent clayey soils. Information about the interconnectedness of these more permeable zones is apparently unavailable. By indicating only a single ground water table level, the diagram gives the impression that water levels have not changed over the period of site investigation. Showing the range in water levels over the years that the site has been monitored would be more realistic. Also useful would be indications of the extent of contaminants in soil and water at the site, as shown in the cross section contained in Geomatrix' 26 October 1995 report.