Petroleum and solvents in the soil and groundwater beneath what was once a downtown mall are stalling Ogden's effort to build a high-adventure recreation center.

The concentration of the solvent tetrachloroethylene (TCE) in the groundwater of one test hole was at 13 parts per billion, more than twice the contaminant level the state allows for drinking water, Thiriot said.

Thiriot, who is manager of site assessment for the state's Superfund program, said the TCE concentration found so far is not a grave concern.

But TCE is heavier than water, so more tests are needed to determine whether the groundwater underlying the future recreation center is seriously polluted.

"If they increase in concentration as we go deeper, then we've got a problem," Thiriot said.