By DAVID SMITH/ecoRI News contributor
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| Nature Conservancy photo. If not a Rhode Island company, why not one from Connecticut? |
The dam is on the border of Westerly, R.I., and Stonington, Conn.
The contractor will have access to the dam on both sides of the river, but the
main staging area will be from a piece of property on the Westerly side owned
by Cherenzia & Associates.
The contractor is expected to begin bringing in
equipment and supplies to the property adjacent to the dam in June. According
to regulations, work on the river can’t begin until July 1.
“They know what they are doing,” Comings said about SumCo. “They
have done a lot of these (dam removals).”
Comings said the first work will be to build a bridge across a
sluiceway and work on sculpting the river bed below the dam. The Nature
Conservancy is working to maintain the level of the river below the dam so that
it doesn’t change the potential for flooding.
When that work is complete, a cofferdam will be built upstream of
the dam to dewater it and aid in its removal.
There will be signs on the river notifying boaters of the
construction project and to direct them to a path for safe portaging while the
project continues into October. The granite wall sluiceway, which has been a
favorite for kayakers and canoeists, will not be removed. A barrier will be
built in front of it on the upriver side and water will only flow into it
during high water, Comings said.
“It will be neat to see the river run free for the first time
since we became a country,” Comings said.
The first dam at the site was built in 1770. It was rebuilt
several times over the centuries. When the dam was washed away in the 1938
Hurricane it was again rebuilt using concrete.
Comings said that if excavation reveals parts of the original rock
and wooden dam, work will be halted for a few days so that it can be recorded.
He said it is possible that when it was rebuilt workers used the same stone
foundation.
Nils Wiberg, an associate with Fuss & O’Neill Engineering of
Providence, has said that because the level of the river is so flat in that
area, the water levels will drop from 2.5 to 3 feet at the dam, from 1.5 to 3
feet upstream at the Boom Bridge Road Bridge and up to a half-foot at Potter
Hill Dam, more than a mile upstream.
Wiberg said tests on the sediment behind the dam show the usual
levels of volatile organic compounds and metals expected to be found in a river
system dotted with mills, but that the levels are all below exposure levels
established by the Environmental Protection Agency (EPA). That means the
sediment will stay on site and be used to form the new river channel or
distributed in the old canal and capped with rock.
White Rock would be the third dam on the Pawcatuck River earmarked
either for removal or modification. The effort is designed to improve fish passage
on the 20-plus-mile waterway that stretches from Worden’s Pond in South
Kingstown to Little Narragansett Bay in Westerly. The work is also expected to
reduce flooding above the site.
About 15 miles upstream, the Kenyon Dam and Lower Shannock Falls
Dam have been removed, while a fish ladder was built at the historic Horseshoe
Falls.
A total of $1.9 million in federal Sandy funds is available for
the White Rock project, according to Comings.
Comings said that the engineering contract for the White Rock
project is $313,793, and will cover all three phases of the dam removal and the
first phase of study regarding Bradford Dam, about 6 miles upstream.
Fuss & O’Neill has done the work on the two dam removal
projects and the building of the fish ladder at Horseshoe Falls Dam.