ARCHIVED REPORTS XR0006617 - Laserfiche WebLink

Home Browse Search

. Updated Corrective Action Plan—Tosco(76)Service Station No 11192, Stockton, California June 26 2002 OPTION#5—OZONE MICROSPARGING Ozone microsparging is a process where ozone in air is introduced into the groundwater through specially designed spargers to create small"microbubbles "As these microbubbles rise within the column of water, the dissolved VOCs are rapidly oxidized Low total flow rates(2-6 cfm) are used Any ozone not consumed in the direct reaction with hydrocarbons rapidly decomposes to oxygen This has an added benefit of stimulating the natural biological degradation In December of 2000,GR started operation of an OMS system consisting of eight ozone sparge points at the Former Unocal Service Station No 0187, located at 437 East Miner Avenue, in Stockton The former Unocal site is located approximately 186 miles southeast of the Tosco site The geology at the Unocal site consists of a sand zone from approximately 20 to 50 feet bgs, bedded between overlying and underlying silt and clay This is similar to the geology at the Tosco site,although the sand zone at the Tosco site is thinner(approximately 15 feet thick) After 18 months of operation of the OMS system at the Unocal site,groundwater sampling data indicate TPHg, benzene and MtBE concentrations in shallow groundwater declined by 53 to 99%, 68 to 96%, and 48 to 99%, respectively The text of the report detailing the results of the operation of the OMS system at the former Unocal site is included in Appendix B If the PHS- EHD would like to review the complete signed report,including tables,figures,and appendices, Ms Margaret Lagorio (PHS-EHD) is the case worker for the former Unocal site COST $50,000 to $75,000 TIME FRAME Short term for impacts on and near the site, longer for offsite impacts ADVANTAGES 1) Relatively low equipment and operating costs 2) Because of low flow rates,vapor extraction to capture off gassing is not required 3) Natural biodegradation rates may be enhanced by introduction of oxygen 4) GR tests at other sites indicates the ability of an ozone air mixture to degrade MtBE, which is the main constituent of concern DISADVANTAGES 1) Areas outside of the injection point radius of influence may take longer to treat 2) Might be difficult to treat large areas CONCLUSION Initial results of GR field tests at other sites indicate that this is a feasible remedial technique for treating MtBE and other petroleum compounds at this site 140245 08 it