A Comparative Plume Study of <scp>DRO</scp> , <scp>GRO</scp> , Benzene, and <scp>MTBE</scp> : Implications for Risk Management

Abstract Groundwater remediation and no‐further action decision making at petroleum underground storage tank (UST) sites has largely been based on an understanding of plume length, stability, attenuation rates for key hydrocarbon constituents. Regulatory guidance to support guide such decisions is in part studies involving individual constituents, namely benzene methyl tert‐butyl ether (MTBE). Questions remain regarding whether current applicable chemical mixtures as gasoline range organics (GRO), diesel (DRO), oxygen containing organic compounds (OCOCs) resulting from biodegradation. To help address this concern, data California's GeoTracker database were used estimate maximum lengths, DRO (which can be analytical surrogate OCOCs) GRO relative MTBE. The distributions lengths similar the four constituents with medians ranging 27 32 m. fraction monitoring wells a decreasing concentration trend ranged 19% 40% MTBE, while fewer than 7% had increasing any Median 0.10% day −1 0.17% results suggest risk management appropriate plumes most UST sites.