Visionary project will open access to 1,000 miles of habitat and restore social, cultural and economic aspects of life along the Penobscot River.
Early in 2013, Wright-Pierce was retained by the Penobscot River Restoration Trust to provide engineering associated with the removal of the Veazie Dam, an 830 foot concrete dam across the main stem of the Penobscot River just above Bangor, Maine. The removal of this dam, in concert with other initiatives being undertaken by the Penobscot Trust will significantly improve access to nearly 1000 miles of habitat for a number of species of sea-run fish. In addition to the obvious ecological benefits, the initiative is aimed at restoring social, cultural and economic aspects of life along the river. A visionary project The Penobscot River Restoration Project is significant not only for its magnitude, but also for its visionary nature: the project includes the removal of two hydroelectric dams, and the decommissioning and construction of a bypass around a third, while allowing improvements at other, less-critical locations that preserve or likely increase the overall hydroelectric generation capacity within the river basin. The dam removal efforts are being augmented with additional fish passage enhancements at four remaining dams within the watershed.
Partnering to achieve goals
The non-profit Penobscot River Restoration Trust includes representation from a number of entities, including the Penobscot Indian Nation, American Rivers, Atlantic Salmon Federation, Maine Audubon, Natural Resources Council of Maine, Trout Unlimited, and The Nature Conservancy. In addition, key project partners such as the US Fish and Wildlife Service (USF&WS) and National Oceanic and Atmospheric Administration (NOAA) are providing technical and financial support for the project. The project is made possible through a combination of public and private funds.
Initial services provided by Wright-Pierce included development of bidding documents for the demolition effort, including detailed hydraulic analysis of the dam under a variety of coffer damming, demolition and river flow scenarios. This was necessary to project the sequence and areas of impact associated with construction of temporary rock embankment cofferdams necessary to divert flows during the phased demolition effort. Based on the Penobscot Trust’s experience with the 2012 removal of the Great Works Dam, the design effort included a collaborative component to incorporate the results of discussions with a group of pre-qualified contractors.
The resulting design, and associated components, provided the basis for obtaining final project approvals from the Maine Department of Environmental Protection, US Army Corps of Engineers, Federal Energy Regulatory Commission and state and federal resource agencies. Following a competitive bid process, Sargent Corporation of Stillwater, Maine was selected to perform the demolition work. In-river work began in mid-July, consistent with agency requirements associated with the protection of Atlantic salmon.
The initial phase of demolition included the construction of stone cofferdams, access roads above and below the forebay area at the generating facility, and allowed for removal of the forebay wall, as well as portions of the forebay floor and center river fishway. Following completion of that element, the stone cofferdams/haul roads were removed and used for construction of Phase II cofferdams/haul roads extending along the main portion of the dam from the opposite side of the river.
The project has included a number of challenges, particularly with respect to the high river flows this season. While years of USGS records from upstream gauging stations suggest that median river flows at Veazie for the months of July and August fall within the range of 5000 to 7500 cubic feet per second (CFS), they have only fallen within this range for 2 or 3 days during the work period. Rainfall within the 8600 square mile watershed has kept river flows in excess of 10,000 CFS for much of the period and as high as 25,000 CFS on occasion.
The work continues
Wright-Pierce continues to work with the Penobscot Trust and its contractor to manage ecological impacts associated with the dam removal effort, including control of turbidity from the construction of cofferdams and during concrete demolition. With each phase of demolition, further drawdowns occur within the impoundment, and plans for surveying and relocating freshwater mussels and potentially stranded fish are implemented as necessary. As the river is drawn down, a number of remnants of earlier dams, consisting of stone filled timber cribbing dating from the early 1800’s, will become further exposed. These will be evaluated with respect to impacts on fish passage and other factors, documented from a historical perspective, and in some cases removed. A key project goal is the re-establishment of upstream passage for Atlantic salmon prior to December of this year. As the impoundment is drawn down over the coming months, we will be reviewing the conditions and working to ensure that the project goals are met. Final work on the removal effort is expected to be complete during the summer of 2014.