SIOUX CITY | During World War II, bombers zoomed through the skies of Siouxland as young pilots and their crews trained to go to war at the air base on the south side of Sioux City.

Once the war was over, the bombers left, and much of the air base property eventually became Sioux Gateway Airport. Few structures from those days remain, but the long runways are still there, as are memories of Sioux City's role in the long-ago war effort.

City leaders believe that era left behind more than just memories. Soil and groundwater contamination caused by fuel spills was discovered at the airport in the early 1990s, leading to a dispute still to be resolved over who should be responsible for the $1.47 million that cleaning up the pollution is expected to cost.

The city believes the U.S. Army Corps of Engineers should pay part of the cost.

But the corps appears unwilling to help clean up the fuel spills, which may date to the 1940s, when B-17 and B-29 bombers ruled Sioux City's skies.

The city and corps disagree about when the fuel leaks occurred. The corps claims the pollution was caused by city and private users after the site was no longer an air base.

"The corps' stance at this time is we have not yet seen any evidence that the petroleum product is tied to the Department of Defense use in the 1940s or 1950s. There's nothing that's linking the contamination now to use by a Department of Defense entity," said Tom Tracy, deputy district counsel with the corps, which handles environmental cleanup at former Department of Defense installations.

The city claims that one of the two polluted sites has not been used by the airport or private entities since the military left.

"Our contention is we have documentation that on at least one site, the city or fixed-base operator never used it," said Rick Mach, Sioux City Water Plant superintendent.

Both sides have asked the U.S. Environmental Protection Agency Region 7 office in Lenexa, Kan., to help resolve the dispute.

"EPA Region 7 has exchanged information with the agencies involved and is currently evaluating all available information to determine the next steps," EPA spokesman David Bryan said.

Sioux City Mayor Bob Scott said the city awaits an EPA decision to decide how to proceed.

"I've suggested we probably begin litigation (against the corps)," Scott said, adding that would probably be a last resort.

The corps seems content to wait for an EPA opinion.

"That's kind of where we're at right now. We're cooperating with (the EPA)," Tracy said. "The corps' position has always been we're willing to look at any new information or facts that may indicate why we should become actively involved."

Groundwater and soil contamination were found at the airport in the early 1990s, when 110 underground fuel tanks, most of them dating to World War II, were removed.

Airport Director Curt Miller said fuel had leaked from the tanks and the pipe system that connected them. Some of the contamination also could stem from fuel being dumped on the ground.

The corps participated in the tank removal and some cleanup work, but notified the city and state regulators in 2005 that it did not believe it had the responsibility to continue to participate.

"They have participated up to a certain point. They just kind of shut their wallets," Mach said.

The two sites are the only ones to be cleaned up, Miller said. One is near the Tee Hangar south of the terminal. The other is north of the air control tower.

Miller's fiscal year 2015 budget includes the $1.47 million cleanup project. The city has budgeted $500,000 of the total to come from the corps, $300,000 from leftover state funds from previous cleanups and the remaining $670,000 from the airport's budget. Miller said the city continues to look for grants and other funding sources to pay for cleanup.

"Eventually, we'll have to clean it up," Miller said. "We are trying to exhaust every avenue to get participation in the cost."

The airport has spent $25,000-$30,000 annually maintaining monitoring wells and skimmer pumps that remove 50-100 gallons of fuel off the top of the groundwater each year. The monitoring wells bracket the contamination plumes so that any movement in the plumes will be detected. The contamination currently poses no threat to the Missouri River or drinking water sources.

"It's pretty flat topographics at the airport, so the plumes don't move around very much," Mach said.

State regulators say the city's ongoing removal of fuel floating on the groundwater is adequate action while waiting for an EPA decision.

"The city is meeting state requirements at this time," said Julie Sievers, environmental specialist senior with the Iowa Department of Natural Resources, the state agency tasked with regulating cleanup of fuel leaks.

Miller said it's hard to determine how much fuel is in the ground. The cleanup will include removal of the fuel from the water and possibly some soil removal.

Only a couple of underground fuel tanks remain at the airport, Miller said, and they were upgraded or replaced in the 1980s. All other airport and private fuel tanks are above ground, he said.

The contamination poses no hindrance to airport operations or future development, and the airport currently faces no cleanup deadlines, Miller said. Still, it would be nice to get funding answers so the cleanup can progress.

"We just want to make sure we have it cleaned up," he said. "It's one of those nagging projects."

Online

Visit siouxcityjournal.com to see historical photos of the Sioux City Air Base and a report about the fuel spills on the site.