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CALIFORNIA REGIO�WATER QUALITY CONTROL BOARD • � Cal/EPA CENTRAL VALLEY R ON Sacramento, Roumento, Road,Suite 0 Sacramento,CA 95827-3098 Phone 916 255-3000 ` FAX(916)255-3015 S+I'"I Pete Wilson,Governor 93 Pl^f� 13 PM 12: 4 9 12 March 1998 Ms. Marilyn Guthrie Tesoro Refining, Marketing, and Supply Company 999 Third Avenue, Suite 4000 Seattle,WA 98104 ABANDONMENT OF TESORO WELL 17A1 AT STOCKTON BULK TERMINAL, STOCKTON, CALIFORNIA (San Joaquin County) Regional Board staff and San Joaquin staff have been working closely together regarding the quesion of abandonment of this unused production well at Tesoro's distribution terminal in Stockton. Abandonment of this well was proposed and approved by staff of the Regional Board and San Joaquin County during the summer of 1997. Subsequent field investigation by EMCON found a well in nearly the same location as 17A1 it did not very closely match the description given in the log for 17A1. The known well was found to be significantly shallower than the reported 200-foot depth of 17A1, and seemed also to be of different diameter. It was additionally found to contain 4 feet of floating product. Staff requested analyses of the product and videologging of the well. These tasks were performed, and it was concluded that the known well probably was 17A1 in a silted-up condition. The product was found to be different from gasoline or diesel. Based on these results, staff of both agencies and EMCON concluded that further search for a"missing" well was unnecessary, and that work should proceed to abandon this well as proposed for well VAL The work was scheduled for 6 February 1998, and was observed by staff of San Joaquin County Environmental Health Division. The abandonment was to have involved perforating the casing and pressure grouting the well for its entire available depth. Several problems including bad weather were encountered. Field observations by San Joaquin County staff found that the agreed-upon procedures, which were in accord with standards of the County and State,were not followed. The casing was not perforated, and part of it was extracted. The grout was not applied in a continuous operation and was not applied under pressure. These inadequacies in the procedures are of concern to staff of both agencies. The potential for an unused deep production well serving as a conduit for contamination already known at the site was what prompted Tesoro's initial proposal to destroy the well. The additional discovery of free product in the well adds to this concern. Staff are further concerned that the full depth of this well is not known,but may be significantly greater than the 54 feet that was documented in the grouting operation. The well log stated 200 feet to be the depth, and the soundings of the well prior to the attempted abandonment suggested a depth of around 90 feet. The remaining depth may be silted up or blocked by collapsed casing. Therefore, staff of both agencies now concur that a more stringent approach to well destruction should be taken in this case. rft Recycled Paper Our mission is to preserve and enhance the quality of California's water resources,and ensure their proper allocation and efficient use for the benefit of present and future generations.