SITE INFORMATION AND CORRESPONDENCE

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California Regional Water Quality Control Board Central Valley Region 7 Robert Schneider,Chair Winston H.Hickox Gray Davis Secretaryfor Sacramento Main Office Governor Environmental Internet Address: http://www.swrcb.ca.gov/—rwgcb5 Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 Phone(916)255-3000•FAX(916)255-3015 10 May 2001 Mr. Robert Mihalovich Chevron Environmental Management Company 6001 Bollinger Canyon Road P. O. Box 6012 San Ramon, :�A 94583-0712 COMMENTS ON NO FURTHER ACTION REQUEST, CORRAL HOLLOW AND GRANT LINE ROADS SITE, TRACY, SAN JOAQUIN COUNTY We have reviewed Geomatrix Consultant's (Geomatrix)December 2000 Second Semi-Annual 2000 Groundwater-Monitoring and Additional Information for Site Closure (report) for Chevron Environmental Management Company's (Chevron) site at Corral Hollow and Grant Line Roads in Tracy. The report presents the results of the second semi-annual groundwater monitoring for 2000 and evaluation of'remedial alternatives including natural attenuation(NA), monitored NA, enhanced in situ bioremediation using oxygen releasing compounds (ORC), and soil excavation. The remediation times/costs of these alternatives are 17 years/$28,000, 17 years/$93,000, 15 years/$145,000, and 2 years/$708.000, respectively. The report recommends NA as the remedial alternative. Our comments on the report are presented below. 1. Alternat.ve 1,NA, is the same as a no action alternative. This alternative is unacceptable because at a minimam, Chevron must monitor the site to ascertain that NA is continuing to occur. Alternative 4 is cost prohibitive compared to Alternatives 2 and 3. In addition, Alternative 4 may not be implementable due to site constraints. The 2-year reduction in remediation time that Alternative 3 provide; over Alternative 2 may not be significant considering the added costs to achieve Alternative 3. However, uncertainties in the amount of ORC needed per year and the time to remedia-.e could make Alternative 3 equivalent to or better than Alternative 2, See Comment 3 for additional comments. 2. The report should clarify how the rate of decline of benzene concentrations, ranging from 0.1 to 0.29 per-ent, was derived. California Environmental Protection Agency �a Recycled Paper The Energy challenge facing California is real.Every Californian needs to take immediate action to reduce energy consumption. For a lis,of simple ways you can do to reduce demand and cut vour ener--v costs.see our Website at htta://www.swrcb.ca.gov/rwgcb5.