Methyl-tertiary Butyl Ether Natural Attenuation Case Studies

The occurrence of methyl-tertiary butyl ether (MtBE), a gasoline additive in ground water and surface water, is causing regulatory agencies, owner/operators, environmental professionals, and researchers to reevaluate remediation strategies at sites where gasoline containing this additive has been released. Over the last 5 to 10 years, monitored natural attenuation has been applied at petroleum hydrocarbon-impacted sites with increasing frequency. The efficacy of this remediation method for releases containing MtBE is now coming under increased scrutiny. The question of natural attenuation efficacy stems from uncertainty about MtBE biodegradability and behavior in the subsurface. Researchers and applied environmental scientists have completed and are continuing studies concerning MtBE biodegradability and behavior. This article briefly summarizes the history of MtBE, its physicochemical properties, its behavior in the environmental, and the applicability of monitored natural attenuation as a remediation tool. Case studies representing past and current research are then presented and followed by a brief discussion. Results from the documented research reviewed show that MtBE does biodegrade in the laboratory and at actual release sites. “Plumathon” studies document MtBE concentration and mass reduction and/or plume stabilization over time. MtBE concentrations in monitoring wells may show declining concentrations indicating natural attenuation. The data reviewed from past and current research suggest that natural attenuation may be the appropriate remediation strategy at some release sites. Yet, the data also indicate that care must be exercised in determining the efficacy of applying monitored natural attenuation at sites impacted with MtBE.