AIR SPARGING LIFE CYCLE DESIGN FOR AN MTBE AND BTEX SITE

摘要

This study presents the life-cycle design, operation, and exit strategy that Battelle implemented at a gas station site (Site 43286) at Marine Corps Base (MCB) Camp Pendleton. This site required remediation due to elevated concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX) and methyl tert-butyl ether (MTBE) in groundwater, and due to its proximity to an ecologically sensitive area. The remedial approach consisted of operating an in situ air sparging/soil vapor extraction (IAS/SVE) system and then implementing natural attenuation. The full-scale IAS/SVE system, which operated from February 1999 to August 2000, consisted of 18 sparge wells and 4 vapor extraction wells. Life-cycle design approaches were implemented during operation of the IAS/SVE system, taking advantage of the most cost-effective methods of off-gas treatment and negotiating shutdown when system operation was no longer cost effective. After approximately 18 months of operation, over 90% mass removal of BTEX and over 75% mass removal of MTBE was achieved and contaminant removal reached asymptotic conditions. Although final cleanup levels had not been met, continued operation was no longer cost-effective. Therefore, after discussions with the regulators, it was agreed that the system would be shut down, and that quarterly monitoring would continue at the site to evaluate rebound for 1 year. If significant rebound occurs, system operation will recommence; otherwise, monitored natural attenuation will be implemented, as necessary, until final cleanup goals are achieved.