Some trees are removed from a south metro park, but for a good reason

In an era when suburbs are getting more and more protective of trees, it was an odd sight and sound one afternoon last week:

Crews with chain saws worked in Savage's Hidden Valley Park, loudly chewing through the trunks of huge mature trees and reducing their branches to piles of brush.

There were two aims, said Jon Allen, the city's parks chief. One was to help preserve the integrity of what the city discovered was a rare swatch of authentic tall-grass prairie within its borders, containing precious native species; the other was to use some of the logs and brush in an innovative approach to improving the health of the nearby Credit River.

"We are lucky to have a very scenic stretch of the Credit River, with lots of residents nearby and extensive trail access," he said. "Even though it has been removed from the state's impaired-waters list, we wanted to make sure we were being good stewards of the Credit River. It's a reminder to the city that we need to remain diligent."

The problem for the river is still plainly visible despite the efforts being made to correct it.

At points, especially where the river makes a U-turn, floodwaters rise up and eat into the sandy mini-bluffs alongside it, drawing sediment into the water that can harm fish and wildlife.

On the day last week when crews were finishing up, Greg Czywczynski, owner of Prior Lake-based CBI Excavating, pointed to where workers had been constructing what's called a "toe wood-sod mat," using $18,000 in Clean Water grants from the state.

They covered all that with a layer of sod, Czywczynski said, and used cables and anchors to hold willow, dogwood, and cedar cuttings to the side of the bank.

This approach to streamback restoration has added benefits, said Savage spokeswoman Amy Barnett.

"It uses native vegetation, which grows quickly and develops dense roots. In addition, the woody material used as fill provides a natural habitat for aquatic and terrestrial life."

The result, visible from the opposite shore to anyone who cares to stop by and check it out, is indeed a loose web of material that fish, frogs and the like could readily use.

In the meantime, Allen said, the removal of trees from the native-prairie areas nearby helps restore that area to what it ought to be, namely a teaching tool for what much of Minnesota used to be, back before European settlement.

"We discovered 10 years ago a remnant prairie still in pre-settlement condition. The reason it had remained as such was that it was such a steep slope," Hidden Valley park being located deep within a ravine.

"We don't see many of those within the city — a real, remnant tallgrass prairie. So we've done some biocontrol management, removing invasive species and converting some turf to prairie about five years ago to cut down on mowing and help recharge the aquifer."

In 2008, he said, a rain garden was created between the parking lot at Hidden Valley and the river, to make sure runoff containing pollutants from cars doesn't race into the river and from there into the Minnesota River, already beset with pollution problems.

In one of those quirky twists that happens sometimes, it turns out that the city was unknowingly helping sustain the native prairie on the steep slope.

"We were inadvertently helping it along," Allen said, "by mowing the slope each year to help make it a better sliding hill once the snow arrived. Once we knew what it was, we needed to take steps to preserve rare plants."

Efforts by Savage, Scott County and other agencies to enhance the Credit River and other natural resources are outlined in the city's Storm Water Resource Management Plan, available for viewing at cityofsavage.com.