RAPID CITY - Four underground fuel tanks were removed from the northwest corner of the parking lot at Sixth and St. Joseph Streets last week. City officials assume more tanks are buried throughout the lot.

The lot is the proposed site of the Rushmont project, a 17-story multi-use building of condominiums, retail shops, offices and several levels of parking proposed by Dream Design International.

While conducting soil tests in the spring, Dream Design encountered fuel tanks, according to Rodell Grosz, project administrator in the Rapid City public works department.

The discovery led Dream Design to research old maps in the library, where they learned a gas station used to be at the northeast corner of the lot and also some tanks at the northwest corner. The known tanks were removed, but some may still exist.

"Later maps showed the tanks were gone. Is that true? I don't know. They have their doubts," Grosz said.

To remove the tanks, the city took advantage of the state's Petroleum Release Compensation Fund. Under the program, the state hires a contractor to remove the tanks. The city's only cost is about $1,500 to replace the asphalt.

"There's probably still contaminated soil there. There's more than likely still more tanks there. But for this project, they just removed four tanks," Grosz said. "They don't go in and explore and do more exploratory digging. They identified four, and that's what they took out."

An evaluation of the Rushmont project is underway after the state office of historic preservation made a request for more information about the building's impact on the downtown historic district.

In September, the state office disagreed with the Rapid City Historic Preservation Commission, which had decided that the Rushmont would not have an adverse impact on the downtown historic district.

The state office did not reject the project outright or specifically mention the proposed height, but a detailed case report is necessary because of the potential effect on the historic district.

The city is preparing a case report, essentially a description of the project, its potential impact on historic property and an evaluation of other alternatives.

If the Rushmont project moves forward and more tanks are discovered, the same state program may be used again. Grosz indicated chances are good that more tanks exist. If so, the state will pay for tank removal and contaminated soil removal directly under the tank.

Although the tanks were discovered in the spring, removal was delayed until now to limit disruption of the parking lot during the height of summer tourist season, Grosz said.

"We didn't know how extensive it was going to be or how big a hole we would have," Grosz said.

As it turned out, the contractor didn't need to dig up a large area. Grosz said the tanks were about five feet down and fairly small. Each was about 10 feet long and held about 1,000 gallons.

Contact Scott Aust at 394-8415, or scott.aust@rapidcityjournal.com