Earthen Dam Removal to Begin at Zebedee Headwaters

With the January 20, 2010 purchase of Zebedee Headwaters in Thetford, the Upper Valley Land Trust became not only the owner, but also the steward of a very special place. The importance of Zebedee was illuminated by a last-minute effort by many individuals and groups, including Thetford Elementary School students, to raise the funds that enabled the permanent protection of the property. As the property’s owner, UVLT is responsible for ensuring that the property continues to be a place for the public to visit, enjoy, and learn.

Northeastern corner of Thetford Hill Wetland in 2008. The earthen dam which will be breached according to permitted plans to restore the wetland to a more natural system.

As part of this stewardship responsibility, UVLT plans to breach the old earthen dam on the property, to restore the natural channel out of the wetland, and recreate the place for wildlife (especially the very active beavers) to interact with their environment as they would in a more natural system. Realizing that the beavers may very quickly rebuild a dam of their own in the location of this man-made one, UVLT and its community partners, including the Thetford Conservation Commission, believe that the earthen dam’s removal will help the essence of a natural wetland return to Zebedee Headwaters.

Any substantial alterations to wetlands (even those that were partially created by man-made structures, including dams) require oversight by state environmental agencies and permits with clear plans. UVLT sought, and was awarded, a Watershed Grant from Vermont’s Agency of Natural Resources to assist with the costs of the dam removal and wetland restoration. Using funds from the grant, and those in its management fund for the property, UVLT hired Root Engineering of Springfield, VT to prepare plans for the dam breach and permit applications. With the plans complete and permits in place, UVLT is now at the point where the groundwork will begin.

Permits from Vermont Agency of Natural Resources

The first phase will consist primarily of drawing down the water in the pond behind the dam. UVLT staff and volunteers will begin the gradual lowering of the pond by removing beaver dam debris from the lowest outlets of the wetland, and continue (hopefully at a pace that exceeds what the beavers will rebuild each night!) draining the pond to reach a significantly lower water level before dam removal can begin. Final drawdown, to a point below the excavation level of the dam, may require some active pumping by the contractor, Northwoods Excavating of Thetford, who will perform the dam breach.

Work on lowering the water level began Thursday, October 28, with the removal of part of one of the many beaver dams that is located near the earthen one. Ongoing maintenance of the property in the presence of beavers is nothing new to neighbor Tim McCosker, who understands the routine of maintaining “beaver baffle” pipes and other tools used to keep water flowing out of the wetland past the earthen dam. With McCosker’s help, and staff visits to the property, the goal will be to continually remove debris, allowing water to drain from the pond.

UVLT Stewardship Coordinator Jason Berard, and volunteer Tim McCosker, pull sticks from the beaver dam near the wetland outflow.

Once the water level is low enough, the contractor will begin excavation work to breach the dam with a large cut, twelve feet wide at the base with low-angled channel sides. The material removed from the dam will be deposited in an upland portion of the property, blended into the topography and seeded to revegetate the area. As with all of its properties, UVLT will lookout for invasive plants that might attempt to take root in newly exposed wetland soils, and combat them without mercy.

UVLT is excited to initiate this restoration phase of the Zebedee Headwaters management plan and will keep you updated as we progress. Please check back soon for more photos of the work and results of our wetland restoration efforts!