A Tale of Two Dams

UPDATED 8/27/2014 – Construction videos added

Hospital Dam Conewango Creek
Hospital Dam is a concrete-capped, rock-filled timber crib dam constructed around 1900 for water supply, and partially breached in a flood in the early 1960’s

Originating near South Dayton in Cataragus County, New York, Conewango Creek winds its way south, crossing the Pennsylvania border and eventually joining the Allegheny River at Warren. The mainstem Conewango was impounded by dams at two locations: the first dam, known as Carters Dam, was built in 1866. Located just upstream of the confluence of Conewango Creek with the Allegheny River, this lowhead concrete dam provided water power for a grist and saw mill until the mid-20th century. The second dam, built around 1900 to provide water supply for the Warren State Hospital, was located three miles upstream from the Carters Dam. Known as the Hospital Dam, a fifty-foot section of it washed away during a flood event in the early 1960’s, and it was subsequently abandoned for water supply.

Conewango Creek is important because it is part of the Upper Allegheny River system— one of the most biologically rich areas for freshwater mussels and river resident species in the Eastern United States. In fact, at a recent conservation conference, the U.S. Fish & Wildlife Service termed the Upper Allegheny system as “the freshwater mussel honey-hole.” Conewango Creek supports at least 17 species of freshwater mussels, including some that are federally-listed endangered species. In addition to their importance in the food web, freshwater mussels are like little water filtration plants. As they feed, they filter contaminants (particularly metals) from the water. One freshwater mussel can filter up to 18 gallons of water per day!

Freshwater mussels are dependent on certain fish species for part of their life cycle, so fish access to headwaters for spawning and rearing habitat is important for mussel survival. Dams fragment aquatic habitat and limit the passage of fish, which in turn impacts the success of mussels in places like the Upper Allegheny system.

With these two abandoned dams impacting fish and freshwater mussel populations, Conewango Creek became a high priority river restoration target for American Rivers when we first began cultivating dam removal projects in Pennsylvania in 2002. We funded the freshwater mussel survey that helped document the conservation value of dam removal on Conewango Creek and eventually led to the removal of Carters Dam by Pennsylvania Department of Environmental Protection in 2009. This project was a great success and a model for partnership between non-profits, local entities, and state and federal agencies in Pennsylvania, but it was also only the beginning for habitat reconnection on Conewango Creek.

PA Fish & Boat Commission surveying for mussels near the dam remnant upstream of the Hospital Dam, July 2013

Three miles to the north, Hospital Dam still blocked fish from accessing the upper 27 miles of Conewango Creek mainstem, as well as numerous tributaries for spawning and rearing. Even though the Hospital Dam is partially breached, it is a velocity barrier for fish passage. This means that the water flowing through the breached section runs at such a high velocity that fish mussel-host species, who are characteristically “lazy” swimmers, can’t swim through it. Consequently, American Rivers and Conewango Creek Watershed Association teamed up with PA Department of Environmental Protection and PA Fish & Boat Commission in 2011 to develop dam removal plans, permitting, and funding.

Now we are on the verge of celebrating the removal of the Hospital Dam and an upstream dam remnant that we discovered during a site visit in 2012 (there are no records of the dam remnant’s construction or operation). Our dam removal construction, scheduled for this month, will eliminate both the Hospital Dam and the upstream dam remnant. This project will ensure that mussel-host fish species can access all of Conewango Creek from headwaters to the Allegheny River, which will give freshwater mussels a chance to flourish.


Removing remnant dam upstream of Hospital Dam. August 25, 2014

Removing Hospital Dam on Conewango Creek, PA. August 26, 2014

Conewango Creek, PA, flowing freely for the first time in more than 150 years! August 27, 2014

2 Responses to “A Tale of Two Dams”

Monica Bauschard

I have lived in Warren for over fifty years and this article is great news. My son Thomas Osborne owns and operates a business in Russell and has supported the clean up for the creek since opening up his business five years ago. The waters are a sight to behold clear,clean and now full of fish and wild life again. Great job to everyone who helped make this possible.