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 BTEX (Benzene, Toluene, Ethylbenzene, and Xylenes) and PHC (Petroleum Hydrocarbons) F1 & F2 compounds were discovered in the unsaturated zone beneath and near underground storage tanks. The busy location, combined with the thick vadose zone, created a challenging remediation environment.

Operation at the high-profile commercial site required continuous collaboration with the facility’s staff to minimize disruption. Preventing migration of vapours into the atmosphere and/or basements of nearby buildings required incorporating various fail-safe monitoring networks and devices.

Process

IRSL developed a site-specifc numerical model to aid in evaluating the distribution of the compounds of concern within the vadose zone. Through the process, they explored various design parameters, such as screen placement, screen lengths, screen diameters, and extraction rates, to determine the best system as well as estimate the remedial timeframe, and set project milestones.

To target the volatile components within the 20m thick vadose zone, IRSL installed, operated, and optimized a network of 44 Soil Vapour Extraction (SVE) wells at various depths and connected the extraction wells to an automated specialized vacuum system. The above-ground system covered a footprint of less 10m-squared and consisted entirely of explosion-proof components. The system was also enhanced with sound proofing to reduce the noise signature.

The petroleum hydrocarbon vapour was then treated using an electric Catalytic Oxidizer, which reduced the concentration of petroleum hydrocarbons by greater than 99.99% prior to discharge into the environment.

Results

Within two months of operation, the LNAPL was eliminated.

Within one year of operation, petroleum hydrocarbon concentrations had decreased 69% on average and mass balance calculations indicated that over 2,800 kg of PHCs had been recovered by the system.

Operational run time exceeded 96%.

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