Brief

At an active gas bar on a high-profile, busy commercial site in a populated urban area, petroleum hydrocarbon impacts, in the form of gasoline along with BTEX (Benzene, Toluene, Ethylbenzene, and Xylenes) and PHC (Petroleum Hydrocarbons) F1 & F2 compounds were discovered in the groundwater and soil. The busy location combined with a large natural seasonal water table variation and deep water table, created a challenging remediation environment.

To contain and remove the LNAPL in the form of gasoline, along with controlling and reducing the mass of BTEX and PHC F1 & F2 in the groundwater, IRSL designed, implemented, maintained, and continuously optimized, an air sparging system.

Various fail-safe monitoring networks and devices ensured that the vapours did not migrate into the atmosphere and/or basements of nearby buildings.

Process

IRSL developed a site-specific numerical model to characterize the site. Through the process, they explored various design parameters, such as screen placement, screen lengths, screen diameters, extraction rates, and injection rates, to determine the best system as well as estimate the remedial timeframe, and set project milestones.

To remove the free-phase gasoline and dissolved phase BTEX, PHC F1 & F2 fractions, IRSL installed, operated, and continuously optimized, a system of 18 sparge wells located around the property and installed to various depths within the plume, targeting the LNAPL and volatile components dissolved within the groundwater.

The wells were connected to an automated specialized blower system, designed to accommodate the deep water table (approximate 20m below ground surface). The injected air volatized the organic compounds and provided additional oxygen required to stimulate aerobic biodegradation, completing the remediation process in-situ. The above-ground systems covered a footprint of less 10m2 and consisted entirely of explosion-proof components. The system was also enhanced with sound proofing to reduce the noise signature.

Results

Within two months of operation, the LNAPL plume was eliminated.

Within 8 months of operation, the dissolved phase plume decreased by 88% on average.

Within a year of operation, mass balance calculations indicated that over 2,800 kg of LNAPL had been recovered by the system.

Operational run time exceeded 98%.

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