In 2021, Pat McElhenny led removal of a dam that had held back water for 100 years. 1 year later, the original Sterry Creek channel resurfaced intact, restoring a natural floodplain on Moosic Mountain

For more than 100 years, water covered the place where Sterry Creek once flowed. Then, in 2021, the O’Conner Dam on Pennsylvania’s Moosic Mountain was removed. The reservoir drained, and conservationists expected to find a changed landscape beneath it. Instead, they saw something remarkable: Sterry Creek’s original channel was still intact.

That discovery gave the restoration team something nature had already built for them. They did not need to invent an entirely new route for the creek. The old channel could once again guide the water, while the former reservoir could become a natural floodplain.

What happened to the old O’Conner Dam?

The O’Conner Dam stood within The Nature Conservancy’s Dick and Nancy Eales Preserve at Moosic Mountain. The reservoir covered about six acres and had held back Sterry Creek for generations. By 2021, the aging structure had become a safety concern.


Heavy rain had already caused damage, making the situation more urgent for the conservation team. Pat McElhenny, The Nature Conservancy’s director of stewardship, led efforts to manage the deteriorating dam. The team carefully lowered the reservoir before removing the central portion of the structure.

The work was not simply a matter of bringing in heavy machinery. Water levels had to be reduced carefully to limit pressure on the aging structure. Pipes and pumps were used before stream restoration specialist Bill Weihbrecht arrived with an excavator in December 2021.

The surprising part was waiting underneath

Once the dam was breached and the reservoir drained, the restoration team could finally see the old streambed.

What they found was the detail that made the project unusual. Sterry Creek’s original channel had survived more than a century beneath the reservoir. The landscape had retained a physical trace of the creek’s former route, even after generations of standing water.

That changed the restoration equation. Instead of forcing Sterry Creek into a completely engineered channel, conservationists could allow the original route to return. It is a useful reminder that restoration sometimes begins with removing what interrupted nature rather than constructing something new.

A stream needs more than a line for water to follow. Its surrounding landscape helps determine how quickly water moves, where sediment settles and where plants and animals can live.

The former reservoir bottom now offers an opportunity to restore that relationship. The Nature Conservancy says the drained lakebed will serve as a natural floodplain for Sterry Creek. During higher flows, water can spread into that low-lying area rather than remaining confined to the narrow channel.

The restoration also gives native vegetation room to return. Over time, that can improve streamside, wetland and riparian habitat across the former reservoir area. It can also help reconnect habitat between the creek’s headwaters and downstream sections.

What does this mean for people downstream?

Sterry Creek is not an isolated mountain stream with no connection to nearby communities.

The creek eventually flows into the Lackawanna River after passing through parts of northeastern Pennsylvania. Its watershed has already been shaped by development, historic mining and changes to natural stream flows. That history makes restoration near the headwaters especially valuable.

Flooding is also part of Sterry Creek’s story. The creek has been identified as a significant source of flooding in the borough of Jessup. Restoring floodplain space does not eliminate flooding, but giving water more natural room can change how a stream responds to high flows.

That distinction matters. The project is not a promise that communities downstream will suddenly stop experiencing floods. Instead, it restores one piece of a watershed that had been altered for more than a century.

What did McElhenny’s team actually restore?

The project combined deliberate engineering with a willingness to let the landscape recover on its own.

The section of stream passing through the former dam breach was designed to handle higher flows. Through the former reservoir, however, the stream channel is being allowed to develop naturally. Conservationists also left parts of the old dam and its stone-lined spillway in place.

Those remaining pieces serve another purpose beyond ecology. They preserve evidence of the site’s human history, including portions of the original infrastructure. Pieces of the timber crib discovered during construction are also being used for historical interpretation.

So the restoration does not erase the past. It leaves enough behind to show what changed, while giving the creek a chance to behave differently.

Why Pennsylvania’s project matters beyond Moosic Mountain

Across the United States, aging dams are becoming an increasingly important infrastructure and environmental issue.

Some dams remain essential for water supply, flood control or other purposes. Others have outlived their original usefulness, while their maintenance and safety requirements continue. Removing one can therefore become both an engineering decision and an ecological opportunity.

The Moosic Mountain project shows what can happen when those two goals meet. A failing structure was removed, an old stream channel resurfaced and a former reservoir began transitioning toward floodplain habitat.

The most interesting part may be what conservationists did not have to rebuild. Sterry Creek had already kept its old route beneath the water. Once the barrier disappeared, the landscape still remembered where the creek belonged.