FRANKLIN — Today you'll find what was virtually an inconceivable sight during last summer's months-long drought: torrents of water pouring over the city's dam on the Harpeth River.

Though the river's flowing, the dam's future — a crucial part of how the city collects water — faces uncertainty. Environmentalists and politicians alike must decide the complicated question of whether it should be removed.

Tearing down the dam means returning the river to a more natural state, where water runs in deep and shallow parts and different forms of life can survive in it. Built in 1961, the 7-foot-tall concrete dam backs up roughly two miles of water in a deep impoundment from which the city pumps into its nearby reservoir for treatment.

"You're going to return a natural flow, you're going to return a natural state to the river," said Pam Davee, the Harpeth River Watershed Association's development director. "(Removing the dam) means it's a healthy, real-flowing river where the wildlife can actually move the entire length of it."

But removing the dam poses its own questions that scientists have only just begun to answer.

Riverbed begs questions

On a recent frigid January morning, environmental scientists Mike Cain and Kim Elkin ignored the river's natural beauty, preferring to concentrate on the muck and mud they could scoop from the bottom.

Ironically, it's the riverbed where the dam's future might be determined. Cain and Elkin have begun work on a study of the sediment in the river. They plan to spend the next few months learning how much sediment the river has and if it contains harmful pollution.

They're concerned about possible waste such as lead and mercury that may have collected in the river after being dumped there for years by Metalico, a former battery smelting operation in College Grove. The plant, closed years ago, was declared a federal Superfund cleanup site.

Until now, no one has tested those chemicals in the river's sediment, Cain said. Removing the dam means the release of sediment that may have those chemicals trapped inside.

"If we tear this dam down, the sediment starts moving," said Cain, a watershed expert for the association. "If we find there's something in the sediment, then the sediment probably has to be dealt with before the dam gets removed."

Results of the study, funded by a $10,000 grant from the Tennessee Wildlife Resources Agency, won't be complete until June.

Environmental concerns aside, the study will likely affect a key decision city

aldermen must eventually make: whether to close the city's water plant or pay millions to expand it.

Capacity could double

Late last year, Franklin officials were ordered by state environmental officials to complete a feasibility study on removing the dam after the city got approval from the Tennessee Department of Environment and Conservation to nearly double the amount of water the city's 55-year-old plant can treat.

"That is information that needs to be obtained," City Administrator Jay Johnson said about the city's own impending study. "That was a very reasonable request by TDEC."

The water plant, located off Lewisburg Avenue, treats 2.1 million gallons a day. With TDEC's permission, that amount now can be increased to 4.15 million gallons.

As part of the approval, state officials said withdrawal from the river cannot occur when the river is flowing below 10 cubic feet of water per second, a stricter cut-off limitation than a city-authorized consultant's report recommended.

To meet the state's requirement, Franklin officials approved spending $78,000 on their own study that would include the same information HRWA officials are collecting.

Rather than duplicate information, Mayor John Schroer and city aldermen want Franklin and HRWA to share information.

That may be a test after years of squabbling between the two entities about the river and the water plant.

"I don't want to pay for anything that's already going to get paid for," said Alderman Dana McLendon, chairman of the city utilities committee.

In addition to drawing water from the Harpeth River, the city buys much of its water from Harpeth Valley Utility District.

Contact Kevin Walters at 771-5472 or kewalters@tennessean.com.