SITE HISTORY - Laserfiche WebLink

Home Browse Search

TreadweIEJUIo A LANSAN COMPANY Request for Low-Threat Case Closure 6 June 2013 RWQC9 case#391149 and#391162 Page 10 420 and 423 N Madison Street Stockton,California Project:731589001 (indicates that results of MTBE tests are known to the Regional Water Quality Control Board); and • Nuisance as defined by Water Code section 13050 does not exist at the site(indicates no nuisance odors or threat to public health and safety). Additionally,the LTCP has specific criteria for groundwater, vapor intrusion to indoor air, and direct contact and outdoor air exposure. The recently adopted LTCP guidelines have been used to establish whether closure is appropriate for each Site. Carando LTCP Justification Primary and secondary sources have been removed at Carando including the USTs and dispenser piping, multiple soil excavations with source area groundwater removal, addition of oxygen release compound, and clean soil backfill. Benzene was detected in only one groundwater sample from the site CPT-EXC-W at a relatively low concentration of 46 pg/L in 2004. The concentrations of TPHg and TPHd detected in this groundwater excavation confirmation sample were also relatively low. While there is no down- gradient groundwater data available for Carando,the BioScreen modeling results and degradation rates extrapolated from 423 N Madison indicate that the plume extent is limited (discussed above). Carando meets the criteria for vapor intrusion to indoor air and direct contact and outdoor air exposure. The down-gradient plume extent and mobility has been estimated using BioScreen to model the benzene plume. The following summarizes the LTCP closure guidelines as applied to Carando: LTCP Guideline Justification for Site Closure(Carando) The unauthorized release is within the service area The unauthorized release is within the City of of a public water system. Stockton, which is served by California Water Service Company. California Water Service Company operates municipal supply wells in the City of Stockton but there are no supply wells located within 2,000 feet of the Site. The unauthorized release consists only of Only releases related to petroleum products have petroleum (including oxygenates). been detected at the Site. The unauthorized release has been stopped. All known USTs and dispenser piping have been removed from the Site. Free product has been removed to the maximum Free product has never been detected at the Site. extent possible. A conceptual site model has been developed. A conceptual model has been presented and is supported by previous documents as well as figures and tables provided with this closure request.