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Coopers
Mills Dam Needs ‘Major
Rehabilitation’, Say Engineers
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| By
Lucy L. Martin |
An engineering survey of
the Coopers Mills dam
points to major
renovations if the
historic structure is to
have another 25 years of
useful life.
The study quantified
what many observers of
the decaying structure
have been saying for
years.
Public safety is a big
concern, along with low
water flows that could
hamper local fire
protection, according to
the findings presented
by Kleinschmidt
consulting engineer Matt
Bernier.
Attending the meeting
were Whitefield
selectmen Charlene
Bartlett and Steve
McCormick; Sheepscot
River Watershed Council
coordinator Levi
Krajewski; and Jed
Wright and Jeff Reardon
of council partners U.S.
Fish and Wildlife (USF&W)
and Trout Unlimited,
respectively. Local
resident Helen Smith, a
member of the
council’s dam review
committee, also
attended.
In addition to safety
issues, the engineering
study addressed the
impact of the leaky dam
and deteriorating fish
ladder on passage of
alewives and Atlantic
salmon. Bernier said he
“wouldn’t be
surprised if (the cost
of repairing the dam)
was $200,000 or more.”
Federal money could be
available because of the
involvement of national
agencies and their
interest in maintaining
or restoring fisheries
in the Sheepscot River
watershed.
The earliest dam was
built in the early
1800s, and for 150 years
water provided power for
a variety of sawmills.
Structural weakness
The report focuses on
the unstable sections of
abutment on the east
side of the dam, a
dangerous situation that
“needs to be addressed
immediately.” The
concrete structures are
supported by rock
masonry that “has
either crumbled or
fallen out from under”
the abutment, posing a
“serious hazard” to
anyone below or on the
structure. Some of the
concrete, the size of
golf balls, has broken
loose and sits in the
fish ladder, according
to Bernier. The study
recommends that the town
fence off this area
because many people
visiting the dam may not
be aware of the hazard.
In addition, two
malfunctioning gates on
the upstream side of the
west abutment need to be
restored. “The gates
may be important for
minimizing headpond
levels (and forces on
the dam) during
floods,” the study
notes.
Dam repairs in the past
were done improperly, so
a critical step is to
remove the old concrete
and replace it with new,
the study recommends.
Coffer damming would be
done upstream to divert
the water while
excavating the sediment
that has settled where
the present dam is. A
new footing at the dam
base would be bound to
the underlying bedrock.
The engineers found the
main spillway is
apparently all right but
it doesn’t perform its
primary purpose of
retaining water. This in
turn affects the
operation of the fish
ladder. During a dry
spell this summer, the
engineers observed
juvenile alewives in the
impoundment circling
“for days and days”
because the gate for the
Denil fishway was above
water and they
couldn’t swim
downstream.
Bernier said the
fishway’s
configuration was “a
little odd” compared
to others he had seen.
“You’d think it
would extend more toward
the river.”
Flow issues
In the low flow study,
the engineers found that
whether they were
considering average flow
conditions or times of
drought, the dry hydrant
can be out of water and
the fish ladder, too,
because of leakage
problems at the dam.
Most important to the
village community,
drawing water from the
hydrant can’t be
counted on during
typical summer flows.
“This should be a
concern,” Bernier
commented. Watershed
council coordinator
Krajewski mentioned the
possibility of the fire
department applying for
FEMA (Federal Emergency
Management Agency) funds
to extend the hydrant
intake pipe to deeper
water.
Jeff Reardon of Trout
Unlimited, speculating
on the worst imaginable
outcome, said he doubted
that if the dam did fail
during high flooding
“people living
downstream would be
running for their
lives.”
Bernier reminded the
group that the state’s
rating of the dam is
“low hazard. The pond
is so small the water
would pass quickly
downstream.” He said
the concern of his
colleague, engineer
Peter Bastien, was about
people standing on the
east abutment “and it
toppling and carrying
them with it.”
The report’s final
recommendation is that a
stability and hydraulic
capacity analysis be
done.
Next step
Reardon suggested
seeking a consultant
“to conduct an
alterna-tives analysis
that would identify at
least three possible
alternatives and analyze
their estimated cost,
feasibility, and impacts
on the existing natural
and cultural
environment.” He said
such alternatives could
include removing the dam
and finding some other
water source for fire
protection, or building
a lower dam with
suitable fish passage.
He emphasized the key to
moving forward is to put
together a group of
people, “project
partners”,
representing the major
interests, including the
fire department, the
town, village residents,
watershed council and
other stakeholders.
There would be several
meetings to talk about
and rank each option.
Reardon said whatever
alternative is selected
“would maintain the
aesthetics of the
village.”
Jed Wright of USF&W
queried selectmen about
the town’s interest.
McCormick said, “Fire
protection in that end
of town is a concern,”
especially because of
Country Manor senior
residence and nursing
home; Bartlett was
primarily concerned
about the town’s
liability for people
climbing on the dam.
Reardon said he wants to
be sure the town is
comfortable with what TU
and the watershed
council are seeking
before he sends out the
request for proposals.
McCormick said the town
would need the article
concerning the chosen
alternative by mid
January, if it is to be
voted on in March.
Reardon said he expected
he could get responses
for several design
options by Dec. 1 and
could get information
out to the public by mid
December. There would
have to be a public
meeting in February. |
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