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California Regional Water Quality Control Board <br /> Central Valley Region ; , <br /> Robert Schneider,Chair <br /> Winston H.Hickox Gray Davis <br /> Secretary for Sacramento Main Office Governor <br /> Environmental Internet Address: http://www.swrcb.ca.gov/rwgcb5 <br /> Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 <br /> Phone(916)255-3000•FAX(916)255-3015 <br /> 1 March 2002 ?Z :? Edd L- ,NW Go <br /> 3JNTS iliNjjd <br /> Mr. Richard Powell <br /> Department of the Navy <br /> Pacific Plaza <br /> 2001 Junipero Serra Blvd., Suite 600 <br /> Daly City, CA 94014-1976 <br /> FINAL BUILDING 817-B UNDERGROUND STORAGE TANK SITE INVESTIGA TION REPOR T, <br /> NAVAL COMPUTER AND TELECOMMUNICATIONS STATION(NCTS), SAN DIEGO <br /> DETACHMENT STOCKTON, STOCKTON, CA <br /> We have reviewed the (1)Final Building 817-B Underground Storage Tank Site Investigation Report, <br /> Naval Computer and Telecommunications Station (NCTS), San Diego Detachment Stockton, Stockton, <br /> CA dated 14 August 2001 prepared by Tetra Tech EM Inc., and received on 6 September 2001, and(2) <br /> Response to our review comments on the draft version of this report. The response to comments was <br /> also prepared by Tetra Tech dated 15 February 2001, and received by us on 16 October 2001. The report <br /> presents the work completed during the investigation of the former UST site at Building 817-B including <br /> four events of quarterly groundwater monitoring well sampling, and recommends three options for <br /> corrective action, in a phased manner: (1)monitored natural attenuation(MNA), (2) enhanced NINA <br /> (injection of air into groundwater to increase dissolved oxygen. Dissolved oxygen is intended to increase <br /> microbial activity thereby increasing degradation of dissolved phase hydrocarbons), and (3) dual-phase <br /> extraction. Please see our comments below. <br /> General: <br /> Based on review of the information presented, it appears that the contaminant concentrations in <br /> groundwater water monitoring wells, in general, are stable and do not show any definite decreasing <br /> trends. The following are the maximum concentrations (in milligrams per liter) of some of the dissolved <br /> chemical concentrations based on the most recent sampling data: Benzene (10), gasoline (<0.05, 54 <br /> reported previously)MTBE (<1, 0.82 reported previously), TBA(<25), DIPE (0.096), 1,2-DCE (<0.5, <br /> 0.49 reported previously). Therefore, we do not believe that MNA is a viable option at this time. We <br /> suggest you consider proceeding with the enhanced NINA approach. If the results from implementation <br /> of the enhanced MNA do not show a decline in dissolved concentrations, we suggest a more aggressive <br /> cleanup approach that includes mass removal. <br /> California Environmental Protection Agency <br /> �a Recycled Paper <br /> The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. <br /> For a list of simple ways you can reduce demand and cut your energy costs,see our Web-site at http://www.swrcb.ca.gov/rwgcb5 <br />