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Who's Afraid Of MTBE? Page 3 of 5 Objective In order to facilitate sale of the property, the owner required that, within a nine-month period, the site was to be free of floating produLt, and contaminant concentrations in soil and groundwater be reduced to levels that would allow natural attenuation of remaining contaminants to achieve site cleanup Approach Ozone sparging was conducted at the site through a series of shallow and deep, sparge points at the site to destroy hydrocarbon compounds in groundwater and soils The ozone sparge system was augmented with soil vapor and groundwater extraction to aid in the removal of the floating product The remedial approach employed a high-density network of remedial wells, under vacuum,to remove the floating gasoline product in approximately one month Soil and groundwater were then addressed via ozone sparging, with soil vapor extraction After approximately four months of these activities, the remedial system was shut off Results The remedial effort at this property vastly exceeded the design goals The objective for the remediation system was to remove floating gasoline, and to reduce the contaminant concentrations in groundwater to the low parts-per- million (ppm) range One week prior to turning on the remedial system, slightly more than 100 gallons of pure gasoline was present on groundwater in an area of approximately 600 square feet In addition, contaminants dissolved in groundwater over regulatory standards were present in an area encompassing over 11,000 square feet with BTEX as high as 58,000 parts- per-billion (ppb) and dissolved MTBE as high as 17,000 ppb The site monitoring wells were sampled one month following remediation Only one of the 17 wells slightly exceeded the State cleanup standards, indicating results that were substantially cleaner than the remedial goals These site wells were sampled again two months after shut down and all were found to comply with State standards, with a decreasing trend evident between the two rounds Three months after system shut down, sampling of soil and groundwater from 10 temporary wells installed between the permanent monitoring points indicated further reduction in hydrocarbon compounds Finally, six months after system shut down, groundwater monitoring of source area wells indicated a continued decreasing trend For this ficial monitoring event, laboratory analyses were expanded from unleaded gasoline to incorporate a wide range of other potential contaminants This analysis indicated that no adverse compounds were generated as by-products from the ozone application The remedial approach removed approximately 3,500 pounds of hydrocarbons from the subsurface via active remediation while stimulating subsequent bioremediation through increased dissolved oxygen http //www mgkflaw com/articles/whosafraidofmtbe html 11/10/2004