Most would expect a National Wildlife Refuge would offer a certain quietude, and at most of the refuges operated by the U.S. Fish and Wildlife Service, it does. But not at all of them.

Parts of the Minnesota Valley National Wildlife Refuge, which stretches from Fort Snelling and Bloomington at the confluence of the Mississippi and Minnesota rivers, to Carver and Chaska, are about to be subject to high levels of noise.

Aircraft will begin flying over the refuge later this month when the new north-south runway opens. Officials expect 8,000 flights a month will leave and arrive at Minneapolis-St. Paul International Airport via runway 17/35.

All takeoffs will head south and all incoming flights will come from the south. Many will pass directly over the refuge at low altitude.

It's not yet clear how extensive the impact will be on the refuge's wildlife, which is one of only four federal wildlife refuges in an urban setting and the only one so close to an international airport. But refuge officials expect significant disruption.

Former manager Rick Schultz told Twin Cities media he expects the noise to be "overwhelming."

"That is going to be a major problem for us," said Patricia Martinkovic, who replaced Schultz as refuge manager two months ago.She said she expects the noise will be at times "deafening."

The refuge includes about 11,000 acres, Martinkovic said. About 4,090 acres have been identified as likely to undergo significant harm from aircraft noise.

"Clearly, this project presented a matter of grave concern for the refuge and the Service," said Dan Ashe, deputy director of refuges and wildlife for the U.S. Fish and Wildlife Service, in testimony before a congressional committee.

Martinkovic suggested the noise might stop conversations among birders along refuge trails. Bird-watchers who in the past were able identify bird species by their calls probably won't be able to do so in the eastern part of the refuge, Ashe testified.

"Our visiting public's ability to view wildlife in its natural setting without significant intrusions will also be compromised," Ashe said.

The Minnesota Valley Refuge hosts roughly 200,000 visitors a year and is the home of bald eagles, deer, foxes, beavers, ospreys, otters, and many songbirds and waterfowl. Even cougars have been seen there, though officials doubt they're permanent residents.

And at this time of year, the refuge is filled with hundreds of thousands of migratory birds gathering to take the Mississippi flyway to warmer climes for the winter. The Minnesota Valley Refuge is touted as one of the top bird-watching spots in the Upper Midwest.

The refuge may lose some of its capacity as a bird sanctuary and an open-air classroom when the new runway sends more jets overhead.

But, there are few studies of the impact of noise on wildlife such as, for example, nesting birds that rely on their calls to establish a territory or find mates, said Tom Kerr, deputy manager of the Minnesota Valley Refuge. Even less information is available concerning the effect of low-level aircraft noise.

There is no formal plan to monitor the impact of aircraft noise on the refuge, Kerr said. But, refuge staff will keep tabs on leading indicators of the refuge's status, such as the number of bald eagle nests.

And, the refuge staff is concerned about the possibility of noise disrupting classes and programs at the Visitor Center, which is at the east end of the refuge and directly under the anticipated flight pattern.

That may be mitigated, in part, by the construction of a smaller classroom building and interpretive center upstream from the Visitor Center, Martinkovic said.

Funds for the new building came from a $26 million payment from the Federal Aviation Administration to the refuge via the Fish and Wildlife Service.

That settlement, finalized not long after the decision to keep the airport at its current location, provides money with which the refuge can continue to work toward mitigating the effects of aircraft noise.

Another example of mitigation, is the acquisition of a 320-acre tract in Carver, recently purchased for the wildlife refuge by the Minnesota Valley National Wildlife Trust Inc., the nonprofit corporation established to oversee noise mitigation.

The Minnesota Valley Trust manages the settlement funds for the purpose of expanding the refuge by at least 4,000 acres - upstream from most aircraft noise.

Most of the recent land purchase will be restored to its natural state, according to the trust. Croplands will be converted to floodplain forest and wet meadows. Smaller wetlands that had been drained by farmers will be restored.

The trust has also acquired tracts in Carver and in St. Lawrence Township in Scott County near Jordan.

"By acting on this and other deals, we can protect critical habitat for wildlife and natural places for the public's enjoyment forever," said Deborah Loon, executive director of the trust.

And at this time of year, the refuge is filled with hundreds of thousands of migratory birds gathering to take the Mississippi flyway to warmer climes for the winter. The Minnesota Valley Refuge is touted as one of the top bird-watching spots in the Upper Midwest.

The refuge may lose some of its capacity as a bird sanctuary and an open-air classroom when the new runway sends more jets overhead.

But, there are few studies of the impact of noise on wildlife such as, for example, nesting birds that rely on their calls to establish a territory or find mates, said Tom Kerr, deputy manager of the Minnesota Valley Refuge. Even less information is available concerning the effect of low-level aircraft noise.

There is no formal plan to monitor the impact of aircraft noise on the refuge, Kerr said. But, refuge staff will keep tabs on leading indicators of the refuge's status, such as the number of bald eagle nests.

And, the refuge staff is concerned about the possibility of noise disrupting classes and programs at the Visitor Center, which is at the east end of the refuge and directly under the anticipated flight pattern.

That may be mitigated, in part, by the construction of a smaller classroom building and interpretive center upstream from the Visitor Center, Martinkovic said.

Funds for the new building came from a $26 million payment from the Federal Aviation Administration to the refuge via the Fish and Wildlife Service.

That settlement, finalized not long after the decision to keep the airport at its current location, provides money with which the refuge can continue to work toward mitigating the effects of aircraft noise.

Another example of mitigation, is the acquisition of a 320-acre tract in Carver, recently purchased for the wildlife refuge by the Minnesota Valley National Wildlife Trust Inc., the nonprofit corporation established to oversee noise mitigation.

The Minnesota Valley Trust manages the settlement funds for the purpose of expanding the refuge by at least 4,000 acres - upstream from most aircraft noise.

Most of the recent land purchase will be restored to its natural state, according to the trust. Croplands will be converted to floodplain forest and wet meadows. Smaller wetlands that had been drained by farmers will be restored.

The trust has also acquired tracts in Carver and in St. Lawrence Township in Scott County near Jordan.

"By acting on this and other deals, we can protect critical habitat for wildlife and natural places for the public's enjoyment forever," said Deborah Loon, executive director of the trust.