Geologist: Plant poses no great threat to aquifer

Geologist: Plant poses no great threat to aquifer by David Lias Derrick Iles, a state geologist with the Geological Survey Program at The University of South Dakota, told members of the Vermillion City Council Monday that a fertilizer plant soon to be constructed in Riverside Township will pose no danger to aquifers used as water sources for rural and city residents.

Brad Trudeau of Centerville plans to construct his fertilizer plant on property just east of the former site of the Seven Mile Station, located approximately two miles north of one of the well heads that is a water source for Clay Rural Water.

The Clay County Commission recently changed the zoning of Trudeau's property from agricultural to industrial to allow the construction to take place.

Citizens have expressed concern that an accidental chemical spill at the plant could contaminate both the Vermillion River and shallow underground aquifers in the region. Among the concerned are Mayor William Radigan who invited Iles and Stan Pence of the Geological Survey Program to address aldermen Monday.

Iles noted that the fertilizer plant will be resting on a thick bed of clay, and added that water in the aquifer in that region moves very slowly.

Should a catastrophic spill occur at the fertilizer plant, Iles said, "it would have to soak through the clays and the silts that are present at the land surface out there, and then get down to the water table, and assuming that it did that, then it would have to start migrating in the direction of the groundwater flow."

If the spill flowed in a straight line in a southerly direction from the plant site, "the best estimate that we have at this point in time is that it would take 25 years for the water to get that far, and that's why our opinion is that there is no real imminent threat to the Clay Rural Water well field."

If a spill occurred, there would be ample time for people to respond. Mother Nature would also help. "There would be a tremendous amount of dilution that would go on, there would be biological activity that would help to degrade the contaminants into something else less harmful, so there are a lot of reasons we are not concerned," he said.

The Vermillion River, located south of the proposed plant site, also acts as a discharge point for shallow ground water. "You have a natural barrier to shallow contaminants, " Iles said.

He added that the fertilizer plant poses virtually no threat to the aquifer that the city of Vermillion taps for water. "You're probably looking at greater than 600 years of travel time for a spill to get down here," Iles said.

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