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STATE OF CALIFORNIA—ENVIRONMENTAL PR CTION AGENCY PETE WILSON,Gov mor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD CENTRAL VALLEY REGION 3443 ROUTIER ROAD,SUITE A `qv ORACA 95827.3098 PH � p- PHONE: (916)(916)255-3000 FAX: (916)255-3015 n 16- 15 May 1995 F pF 199S Ms Anastasia Duarte RV�CF Time Oil Company 2737 W. Commodore Way Seattle, WA. 98199-1233 REVIEW OF WORKPLAN FOR PILOT-SCALE TESTING AT STOCKTON BULK FUEL TERMINALS, STOCKTON, SAN JOAQUIN COUNTY We have reviewed the workplan for pilot scale testing of several potential remedial technologies at the Port of Stockton, which was submitted by EMCON on behalf of the Stockton Terminals Technical Committee. Staff comments are contained in the attached memo. The workplan proposes testing of soil vapor extraction (SVE), air sparging, and ground water pumping in vertical wells, and SVE and air sparging in a ground water interceptor trench. Two potential test locations are proposed,one in the southeastern portion of the terminals area, and the other in the northern area. The northern test area will be used only if results in the southern area are deemed favorable. Regardng the ground water interceptor trench, the present workplan does not differ substantially from previous proposals in 1994 and 1993. However, as noted in the attached memorandum review, site conditions have changed since the fust proposal of a trench, in that the thickness of free product has decreased significantly and the vadose zone is even thinner this season than it has been, due to the heavy rains of the past winter. As a result, the need for product skimming in the trench, as formerly proposed, probably no longer exists. and other factors besides thickness of free product may become of greater importance in determining the location of the trench and the test wells. We are concerned that,because of the very thin vadose zone in the proposed southern test area(presently less than 3 feet), this proposal may not represent the most favorable location for testing of the SVE technology. Our principal concern is that, in considering the overall site conditions on a yearly basis, neither SVE nor air sparging, separately or in combination, appear to be very promising technologies. The stratigraphic, lithologic, and hydrogeologic complexities of the terminals area may make this a difficult remediation project using any method or combination of methods. On this basis, we expect that pumping and treating of ground water will have to be employed as part of the remedial package and urge you to make characterization of the aquifer properties a high priority. We recommend that you proceed with aquifer testing in the northern test area without waiting for results of the SVE testing in the southern area, assuming that both of these areas will require remedial installations. We further recommend that STTC begin planning studies for bioremedial techniques.