Underground Storage Tanks Pose Groundwater Threat

by kespeland on July 28, 2009


In an empty lot off Lower Hunters Trace road in Louisville, an excavator is deftly scooping away the gravel around a truck-sized tank lodged in the ground.

“We’ve got two underground storage tanks, typical two dispenser pump island.  It was your typical convenience store that’s gone out of business.”

Rob Daniells mananges Kentucky’s Underground Storage Tank program.  He’s overseeing the operation to clear this site of the previous owners’ gasoline storage tanks—the ones that stored the gas customers pumped into their cars—so that another business can use the property.  But why not just leave them there, undisturbed, under the pavement?

“Any time you’ve got a tank system that’s been in the ground for 15, 20, 25 years, you always have the threat that that system may have leaked at some point during its lifespan,” says Daniells.

So while the excavator gently nudges aside more of the debris that’s trapping the tank, environmental consultant Mark Hopkins climbs into the pit to take soil samples.

Data source: Environmental Protection Agency

Data source: Environmental Protection Agency

“In this soil we’ll be testing for gasoline constituents: benzene, toluene, ethyl benzene, some xylene,” says Hopkins.

If tests come back positive, that could mean trouble for groundwater.  According to the Kentucky Division of Water, nearly two million Kentuckians rely on groundwater as a source for drinking water.  Once these toxic chemicals have seeped into the ground or directly into a drinking water source, they can be tough to tease out.   Rob Daniells says just containing such contamination is the bulk of the state removal program.

“ And that’s where things really get difficult obviously, because when gasoline or diesel constituents get into the groundwater table, it’s very, very difficult, it’s very time-consuming, and it’s very expensive to try to remove that material from the groundwater,” Daniells says.

To help clear that backlog of contaminated sites, Kentucky will receive more than $4 million dollars in federal stimulus funds. Daniells hopes that might be enough to clean up nearly 70 sites.  Kentucky does have a state fund to help tank owners clean up sites.  But it’s not enough to cover abandoned or improperly registered sites.  And it’s some of those older sites, with the traditional steel tanks, instead of the newly required fiberglass, that worry Patricia Ellis.  That’s because the steel corrodes over time.  She’s a hydrologist with the state of Maryland’s underground storage tank department. But she says that’s not the only concern.

“There’s just so many little places where pipes connect and things like that.  And every one of those has a chance of leaking,” says Ellis.

What’s more, Ellis says newer fiberglass tanks aren’t immune to corrosion either.  But ironically, she’s talking about their vulnerability to what many consider an environmentally friendly bio-fuel.  Many gas stations offer gas with 10% ethanol.  And a few vehicles have been designed to run on blends of 85% ethanol.

“And even at the lower percentages it’s having a corrosive effect on some systems, because they were never certified for ethanol to begin with. And when you increase the percentages, there’s kind of a magic intermediate percent that’s even more corrosive than 100% ethanol,” Ellis says.

Ellis says that if the tank springs a leak, the ethanol poses less immediate danger.

“One wonderful thing about ethanol is that is degrades wonderfully in the soil and groundwater, but it takes away the oxygen and nutrients the other components of gasoline need to naturally degrade in the groundwater,” says Ellis.

While states eye new regulations for tanks, they still face the enormous task of tackling what’s already been buried beneath the surface.  The Environmental Protection Agency is doling out varying amounts to nearly every state to address the problem. But in Kentucky, those funds may be stretched to their limit.  The state has the third worst record in the country in terms of the number of tank owners who actually comply with the regulations for preventing and detecting leaks.  And it’s in the top 10 nationwide for the largest number of leaks already confirmed.

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