enlarge Gordon Chibroski/Staff Photographer

Nick Stasulis and Mark Huard, hydrologic technicians for the U.S. Geological Survey, collect data on water flow in the Presumpscot River near the Route 302 bridge on the Westbrook-Portland line.

enlarge Gordon Chibroski/Staff Photographer

Barry Mower puts a gill net into the Presumpscot River to collect biological samples for testing as John Reynolds steadies the boat. They are part of a team of technicians and scientists testing the Presumpscot River for flow, quality and health of biological species.

enlarge Gordon Chibroski/Staff Photographer

Tim Bridges, a scientist for the Environmental Protection Agency, sets up an automatic water sampling and testing machine.

enlarge Gordon Chibroski/Staff Photographer

This automatic collection device will take a water sample each hour from the Presumpscot River.

State and federal scientists, equipped with flow meters, fishing nets and red dye, began a thorough checkup of the Presumpscot River on Tuesday.

The comprehensive study is the first effort in at least a decade to assess the health of one of Maine's hardest-working waterways. Results will help state officials measure progress in the river's ongoing cleanup and set future standards for dam flows and pollution discharges.

Since the last close look, in fact, a pulp mill in Westbrook stopped discharging waste and the Smelt Hill Dam was removed.

"The conditions are different," said Barry Mower of the Maine Department of Environmental Protection. "It should be better. In fact ... we know it's better. We don't know if it's good enough yet."

The Presumpscot was one of Maine's first industrialized rivers and was once one of its dirtiest. It was described as an open sewer in the 1960s and '70s and is now in the midst of a gradual, but dramatic, comeback.

The removal of the Smelt Hill Dam in 2002, for example, restored a natural falls that attracts sea-run fish such as alewives, as well as city residents who now use a trail system and canoe launches in the area.

There are now eight dams along the 25-mile river that connects Sebago Lake to Casco Bay.

Those dams, especially one at the outlet of Sebago Lake, control the flow of the river and are needed to maintain enough water flow to flush out pollution, including discharges from Westbrook's sewage treatment plant and the Sappi Fine Paper mill in Westbrook.

The tests being done this week will help determine what the flow rate and discharge limits need to be for the river to meet Maine's clean water standards and sustain fish and other aquatic life, Mower said.

Mower and John Reynolds from the DEP spent Tuesday collecting water samples and setting out a series of gill nets at several points in the river, including just above the Route 302 bridge between Portland and Westbrook.

The nets are suspended by buoys and catch fish that try to swim through the mesh. Mower and Reynolds will return today to pull up the nets and gather fish for tissue and blood samples.

Smallmouth bass will be tested for the presence of dioxin, a contaminant linked to historic paper mill discharges.

And white suckers, fatty bottom-feeding fish, will be tested for the presence of endocrine disrupters, a family of compounds that is showing up in some urban waterways and fish because of the widespread use and improper disposal of pharmaceuticals.

Farther upstream on Tuesday, at the Sappi Fine Paper mill in Westbrook, Tim Bridges, a federal environmental scientist, dumped a pail of red dye into the river as part of a sophisticated flow test.

The dye quickly mixed in so that it was not visible. But machines set up along the river automatically collected and scanned water samples for traces of red as it slowly flowed toward Casco Bay.

"The dye is kind of spreading out and dispersing here," Bridges said later, as he set up scanning equipment near the Route 302 bridge.

Just downstream, a team from the U.S. Geological Survey used a small outboard to slowly pull an acoustic profiler back and forth across the river.

The floating instrument measured the water's velocity and used soundwaves to create a three-dimensional profile of the river, including depth and width and the shape of the river bottom.

Much of the study will be completed this week, although scientists expect to collect fish into next week. Analyzing all of the water samples and fish samples, as well as the flow data, will take months. But researchers could know later this year just how healthy, or unhealthy, the Presumpscot is.

"It's a good start," Mower said Tuesday afternoon after the initial tests. "We'll see if we learn anything."

Staff Writer John Richardson can be contacted at 791-6324 or at:

jrichardson@pressherald.com