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Removal Timeline


Dam removal is planned for July through October of 2016. These months are ideal for their low flows and reduced impact to fish. The demolition will occur in two phases, first on the west side opposite the powerhouse and then on the east side. A cofferdam will be used to isolate the work area. Removal of the dam will be performed in an environmentally responsible manner with excavators and other equipment. During the first removal phase, about 213 feet of the dam from the west bank will be removed. Phase two will remove the remaining 35 feet of the dam, as well as the stoplog gate structure and the concrete walkway. All that will remain is the powerhouse. The general sequence of the removal project will be as follows:
 
Mobilization
In-stream work is restricted prior to July 15 per NYS Department of Environmental Conservation guidelines protecting aquatic ecology. Equipment will be mobilized to the site in order to begin work as soon as possible.
 
Reservoir Draining
June 27 - July 18, 2016
Stoplog removal
All stoplogs will be pulled from the stoplog gate structure, allowing the reservoir to drain. The stoplog gate structure is a control device used to alter the water level in the impoundment. This photo, taken in late September 2015, shows the removal of stoplogs during a controlled impoundment drawdown. Enough logs have been removed so that the impoundment level is below the crest of the dam.
stop log gate
 
Bank stabilization
When the river banks are exposed after the draining of the reservoir, they will be stabilized through various approaches, utilizing rip-rap and/or vegetation plantings and seeding. Stabilization will occur where necessary from 200 feet downstream of the dam to 200 feet upstream of the Route 37 bridge. Stabilization measures will be maintained throughout the duration of the removal project. A temporary impoundment drawdown was done in fall 2015 to make observations in preparation for dam removal. This photo taken on October 1, 2015 gives an example of the expected bank exposure in the former impoundment area. The flags indicate changes in water level as the drawdown progressed.
expected bank exposure
 
Installation of erosion and sediment controls and access roads
Siltation prevention measures such as perimeter fencing will be installed. The sediment Dewatering Area and Concrete Rubble Processing Area, as well as access roads will be constructed. The movement of silt to wetlands, streams, or the river will be mitigated throughout the project.
 
Phase I Removal
July 19 August 15 (20 days)
Demolition of about 213 feet from the west side of the dam.

Cofferdam installation
A temporary cofferdam will be constructed from the west bank to isolate both upstream and downstream faces of the dam. River flow will be directed through the stoplog gate structure on the east.

Dredging
The area between the cofferdam and the dam will be dewatered and sediment and debris will be mechanically dredged and transported to the Dewatering Area. Dredged material will be incorporated as fill for other Tribal Public Works projects.
west end
 
Dam demolition
The concrete dam within the cofferdam limits will be demolished and concrete will be transported to the Concrete Rubble Processing Area. Rubblized concrete will be re-incorporated into the project as fill or bank stabilization.

Cofferdam removal
Flow will return to the western reach of the river.
march 7 2011
 
Phase II Removal
August 16 - September 5 (15 days)
Demolition of the remaining 35 feet of the dam on the east side, stoplog gate structure, concrete walkway, and trash rack. Phase II demolition will be done in the same way as Phase I.
 
Cofferdam installation
A temporary cofferdam will be constructed from the east bank to isolate the remaining section of the dam. River flow will be directed through the western reach.

Dredging

Dam demolition, Stop log demolition, Trash rack demolition (trash rack shown in picture)
trashrack
 
Permanently plug powerhouse intake
The powerhouse intake will be permanently plugged in order to preserve the interior of the powerhouse for future work. Additionally, rip-rap will be installed on the upstream side of the building to protect it from high flows and ice jams.

Cofferdam removal
Natural flow of the river will be restored.

Site Cleanup and Demobilization
All disturbed areas will be seeded and mulched for vegetative cover, and erosion control measures will be removed.
water intake
 
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Saint Regis Mohawk Tribe Environment Division
http://www.srmtenv.org/index.php?spec=2016/04/wrp/removal-timeline