WORK PLANS - Laserfiche WebLink

Home Browse Search

WEST ASSOC S STOCKTON DC, TANK NO. 3 CONCEPT CLOSURE PROPOSAL, Page 2 In March 1991 DDS arranged to have two angle borings completed under each tank end in order to retrieve soil samples for laboratory analysis. Four soil samples were eventually collected. One of the soil samples was found to contain 3, 200 PPM TPN. The other three were uncontaminated. A full report of findings describing the 1991 soil investigation was prepared by West & Associates (formerly West & Hansen) and submitted to the San Joaquin County Environmental Health Division in May 1991 . The discovery of soil contamination in 1991 under tank No. 3 precluded closure in place at that time. Consequently, DDS pursued other alternatives such as tank removal. A structural engineer was retained to determine costs associated with a tank removal project. As expected, the costs to shore up the water tower during the tank removal were excessive. Once it was decided to close Stockton as a Developmental Center, the possibility of removing the water tower entirely became viable. DDS studied a project to remove the tower, thus providing unlimited access for underground tank removal . DDS even went so far as to solicit bids for tower demolition. However, removal of the water tower is now no longer considered a viable option due to the likelihood that CSU Stanislaus will take over most of the Stockton facility for a satellite college campus . Without the tower, it is unlikely that fire hydrant flow rates would be within fire code specifications for that type of usage. In early 1995 DDS arranged to have the full magnitude and extent of soil contamination in the tank No. 3 vicinity investigated. Tetra Tech subsequently completed eight borings and collected 31 soil samples for laboratory analysis . The Tetra Tech investigation determined that soil contamination in the tank No. 3 vicinity was of minor extent. Only 3 of the 31 soil samples collected contained detectable contaminant concentrations. CONCEPT CLOSURE PROPOSAL In 1991 , DDS requested approval from San Joaquin County to close tank No. 3 in place. Approval was not granted at that time. Since 1991 , two factors have changed which makes closure in place of tank No. 3 viable. 1 ) . The full extent and magnitude of contamination has been investigated and found to be minor. 2) . Regulatory agencies have become more receptive to risk based closure decisions. It is proposed to pursue closure in place of tank No. 3 at this time. Specifically, a package would be submitted to the San Joaquin County, Environmental Health Division, consisting of the following: