Roughly 85 per cent of the gasoline spilt at the Rubis facility in St George’s in March remains unrecovered, according to the Department of Environment and Natural Resources.

In a monthly update provided this afternoon, the department said that monitoring from 12 on-site wells and two off-site wells “continue to define the extent of the spill”.

The spill consists of three parts: a liquid plume floating on groundwater roughly 70 feet below the surface, a vapour plume of gasoline fumes above the water table within the limestone, and a dissolved plume of water-soluble components of the gasoline dissolved in the groundwater.

Recovery of the liquid and vapour plumes has used six recovery wells as well as a vacuum skimmer.

“Operational data indicated that the vacuum extraction system is limiting the liquid and vapour plumes to the confines of the Rubis site,” the Bermuda Government said in the release.

“Regular groundwater sampling is being performed to assess the potential for any constituents that comprise the ‘dissolved plume’ to migrate beyond the site boundaries at concentrations exceeding drinking water or odour-threshold limits.”

The vacuum system, the department said, had been operating daily since April 1, “with occasional downtime for maintenance and upgrades”.

“The recovered vapour/liquid product from this system is about 15 per cent of the original volume of the spill as of July 26,” the department said.

“This backs up previous predictions that active clean-up operations will likely run for several years, followed by a confirmatory monitoring period following active remediation.”

Naturally-present bacteria are expected to remove gasoline through biodegradation over time, Government said.

Rubis and consultants Arcadis are preparing a comprehensive site assessment report, following Government-established guidelines. The report will subsequently be reviewed by John Wilson, a Government consultant, and DENR personnel, to “ensure that the appropriate long-term remediation strategy is designed and implemented”.