A narrow channel of water curves along what was the bottom of the O'Connor Reservoir. In the background heavy construction equipment widens the breach in the earthen dam.
O'Conner Dam Breach Moosic Mountain Preserve's O'Conner Reservoir is little more than a trickle following the breach of the dam on December 1, 2021. © Andrea Campbell

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Emergency Dam Removal at Eales Preserve Completed

The former O'Conner dam site will be allowed to restore naturally with TNC monitoring the changes.

The Nature Conservancy announced it has completed the removal of the aging O’Conner dam and reservoir at the Eales Preserve on Moosic Mountain. After an inspection last year revealed that the dam was increasingly at risk of breaching during heavy rainstorms, TNC closed the area to visitors and temporary measures were taken to lower the water level. In December, contractors were engaged to remove the center of the dam and allow the water to safely drain. The site will be allowed to restore naturally with TNC monitoring the changes.

The reservoir area will remain closed to visitors due to muddy conditions that could lead hikers or bikers to get stuck. The surrounding trails remain open, but visitors are asked to stay on the trail.

The dam was constructed via stacked logs and stones more than 100 years ago, but staff monitoring the site had noticed increasing erosion and water moving through the structure. Though the center of the dam was removed, the stacked stone structures on either side were left in place to mark where the dam once stood and preserve a piece of its history. TNC hopes to add interpretive signage at some point in the future that tells the site’s story.

“Though we are saddened that this historic dam had reached a point where it was no longer safe to leave in place, we are glad that we have been able to preserve some pieces of it for future visitors to see for themselves,” said Lori Brennan, Executive Director for The Nature Conservancy in Pennsylvania and Delaware. “The dam and reservoir were cherished by many people in the local community and an important part of Moosic Mountain’s history.  We want to make sure its story is preserved.”

Draining the reservoir also revealed the original stream channel that flowed through the area prior to it being dammed. Staff will monitor the site to track how well the vegetation reestablishes itself and whether any invasive species controls or additional plantings are required. 

“Seeing the original stream channel emerge once again from the bottom of the reservoir reminded us how resilient nature can be,” said Christine Arnott, Freshwater Project Manager for The Nature Conservancy in Pennsylvania and Delaware.  “The former dam site will provide a great opportunity for us to observe how nature can restore itself, and for our visitors to see and experience that as well,”

After the site restores itself, the returning vegetation and stream should provide excellent wildlife habitat. Moosic Mountain contains globally recognized ridgetop barrens that are home to a number of native and rare species, including bobcats, snowshoe hares, rattlesnakes, butterflies and rare moths.  It is also an important flyway and stopover for many species of migrating birds and raptors. 

Visit nature.org for more information about Eales preserve and how to visit. Photos of the dam site and removal process are available for download

The Nature Conservancy is a global conservation organization dedicated to conserving the lands and waters on which all life depends. Guided by science, we create innovative, on-the-ground solutions to our world's toughest challenges so that nature and people can thrive together. We are tackling climate change, conserving lands, waters and oceans at an unprecedented scale, providing food and water sustainably and helping make cities more sustainable. Working in 76 countries and territories: 37 by direct conservation impact and 39 through partners, we use a collaborative approach that engages local communities, governments, the private sector, and other partners. To learn more, visit www.nature.org or follow @nature_press on Twitter.