As the giant piers of a new four-lane commuter bridge rise from the St. Croix River, millions of dollars are quietly being spent to protect the blue ribbon waterway from environmental decay.

But even as work begins on everything from asbestos removal to archaeological inventories, concerns have surfaced that it won’t be extensive enough to shield the Lower St. Croix from further contamination once the bridge opens and exposes more grassland and forest to urban development.

Among the biggest worries is the potential harm caused by the bridge and its traffic to Lake St. Croix, the wider, deeper portion of the river from Stillwater south to Prescott, Wis. The lake was added to Minnesota’s impaired waters list in 2008 because extensive phosphorous, from stormwater runoff, was creating large oxygen-sucking algae blooms.

But that discovery didn’t come until two years after 28 stakeholders representing competing political interests — environmentalists, preservationists and local, state and federal government agencies — reached a compromise to offset “unavoidable” changes the new bridge will bring when it opens in 2016.

“We fought as hard as we could and we got what we got,” said Jim Erkel, an attorney at the Minnesota Center for Environmental Advocacy who participated in the debate. “My fear is that the money isn’t enough.”

About $42 million of the $676 million bridge project was set aside for more than 30 protection projects, but much of that will be spent on moving or removing old buildings and other structures. An endowment fund for the Stillwater Lift Bridge, plus money spent to convert it for pedestrian use, account for about a quarter of the overall mitigations budget.

Less than $10 million will be given to local governments in St. Croix County to address urban growth and the potential threat to the river.

Engineers and planners on both sides of the river say their environmental work carries far-reaching benefits for water quality, tourism and other major issues confronting the St. Croix. It also will increase public awareness of pollution, erosion and other threats, they said.

“Being right there on the National Wild and Scenic River, there’s quite a gem there that this effort is identified to help protect,” said Dan Bauman, a regional director at the Wisconsin Department of Natural Resources who is coordinating efforts on his side of the river. “We need to be smart about protecting water quality and quantity. If we don’t do the planning now, by the time the development gets here, it’s too late, it’s too costly.”

The dozens of projects designed to protect the river and its surrounding environment might be the most ever for a Minnesota bridge project, said Todd Clarkowski, the MnDOT project engineer overseeing the work.

The projects include an agreement in which Minnesota and Wisconsin will pay a total of $2.7 million to manage urban growth in St. Croix County. That agreement includes land-use planning and new local zoning ordinances in cities and towns most affected by the bridge, such as the Town of St. Joseph, Wis. A “riverway impacts” agreement also supplies $4.5 million for land conservation purchases to compensate for damage to the Wisconsin bluff land where the bridge will cross.

Fixing old problems

Environmentalists say mitigation spending is necessary because potential harm to the river from converting rural land to paved roads, parking lots, houses and commercial buildings is becoming more unpredictable as construction transforms the landscape.

The 2006 stakeholder agreement, Erkel said, didn’t result from policy-based consensus but from painful negotiations and threats of lawsuits. But the millions of dollars set forth in the agreement are only a beginning — local governments will still need to find additional funding to sustain water quality programs through taxation or through state grants, because mitigation funding falls short, Erkel said.

“One of the frustrations is that the [mitigations] package was done a long time ago,” said Deb Ryun, executive director of the St. Croix River Association.

Money allocated for the work, she said, is standard for a construction project, but doesn’t reflect the river’s special qualities.

Clarkowski and other engineers and planners, however, say mitigations will eliminate long-standing problems, such as oil and gas running off the Stillwater Lift Bridge into the river, and eyesores such as abandoned buildings and unused barge piers. Stormwater diversions will reduce phosphorous entering the river, he said.

Still, Erkel said, the mitigations pale in comparison to threats posed by the bridge, which will stand more than two times taller than the Interstate 94 bridge at Hudson, Wis.

Minnesota and Wisconsin each will pay half of all mitigation costs, regardless of location, according to partnership agreements. MnDOT is considered the lead agency, spending state funds for work in Wisconsin, but contracts stipulate that Wisconsin will refund half the overall cost.

Scientist Jim Almendinger, of the St. Croix Watershed Research Station, said the bridge will cause more stormwater runoff that will complicate attempts to reverse contamination in Lake St. Croix. The research station will receive $55,000 to study that very issue.

Almendinger also is studying potential phosphorous reductions in another St. Croix tributary, the Sunrise River, in hopes of offsetting anticipated phosphorous increases in Lake St. Croix. Once the bridge opens and urban development escalates, deterioration of the river’s water quality will accelerate, he said.

“It’s significant. This is a monkey wrench thrown into our plans to reduce phosphorous,” Almendinger said of the new bridge. “It’s hard for me to say that building the St. Croix bridge will make the river better.”

Some projects finished

Although the bridge opening is still two years away, some mitigation work has already been completed.

On the Minnesota side of the river, that includes restoration of a 1938 scenic overlook and moving the Bergstein Shoddy Mill, an early rag factory, from the path of the bridge approach in Oak Park Heights to land along the river.

The hulking Terra Terminal fertilizer warehouse, on the riverbank near Stillwater, was razed. And divers moved rare Higgins eye pearlymussels from the bridge site.

On the Wisconsin side of the St. Croix, conservationists transplanted threatened Dotted Blazing Star plants from the spot where a new highway will connect to the east end of the bridge. A large and dilapidated “Buckhorn” sign, once glowing in red neon to attract customers to a 1930s-era tavern and supper club that was destroyed by fire 50 years ago, will be removed from the blufftop.

Some of the most visible and important work, however, is just beginning.

In St. Croix County, that work includes bluff-land protections, stormwater diversion projects and an economic study to help forecast population changes and anticipated commercial development once the bridge opens.

There are plans, too, to build a 5-mile loop trail to cross both the new bridge and the 1931 Stillwater Lift Bridge once it’s closed to vehicle traffic. The old bridge also will be outfitted with safety features to protect pedestrians and will be repainted from dark gray to its original federal green.

The $7.2 million being spent in Wisconsin will be doubled with matching grants, Bauman said, and result in better land management practices that in turn will improve water quality of the St. Croix’s tributaries, such as the Apple and Willow rivers.

The National Park Service also plans to improve riverway education, interpretation and recreation. The agency received $300,000 to build informational kiosks and outdoor exhibits and make possible improvements at the St. Croix River Visitor Center in St. Croix Falls, Wis. Another $100,000 will be spent to help develop a spill response plan in case of sudden and drastic pollution of the river.

Clarkowski, the MnDOT engineer, said stakeholders recognized the importance of setting enough money aside to study all the implications of building a bridge over such a scenic and spectacular river.

“It was a very collaborative, stakeholder-driven effort to get to this,” he said.