Extent of gas spill remains unknown

The amount of gasoline spilled Monday afternoon from a massive ExxonMobil storage tank in Spokane Valley remains unknown, according to officials.

Cleanup crews first vacuumed fuel that had pooled on the ground after maintenance workers accidentally severed a pipe that was part of a temperature gauge, then began excavating dirt.

They hoped to scoop out enough of the saturated dirt to keep the spill from reaching the Spokane Valley-Rathdrum Prairie Aquifer, which sits 60 feet below the ground surface. Soil samples found gasoline had seeped 12 feet by early Tuesday morning.

The tanks do not sit atop impermeable liners.

Hydrologists from the Washington state Department of Ecology said the aquifer moves slowly to the west at that location and were confident crews would have time to pump out contaminated water.

The amount of gasoline spilled won’t be known until ExxonMobil empties the 1.6 million gallon tank and accounts for the lost fuel.