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People walking across the drained frozen mill pond 1916-17. Trestle and flume visible, left; St. Bridget's spire, right. |
One wonders what is on the bottom of the mill pond. No one
is allowed to swim in it, or boat on it, so people who own a diver’s face mask,
or have the ability to look over the side of a boat on a calm day, cannot
fathom what lies on the bottom.
What we do know is that the mill pond is not a ‘kettle pond.’
The most famous kettle pond in Massachusetts is Walden Pond, 65 acres in area
and more than 100 feet deep at its deepest. Kettle ponds closer to Maynard, not
famous and not as deep, include White Pond (Concord), Crystal Lake, Sudbury
(old name “Bottomless Pond”), and possibly White Pond (Hudson), for which
Maynard owns water rights, and until 1999, sourced some of its tap water from
there.
Toward the end of the last ice age, when the glaciers of ice
as much as two miles thick were melting in place there were many instances in
which large (LARGE!) blocks of ice remained as a remnant while the ice surrounding
it melted, leaving an ice ‘island’ separate from the face of the glacier. As
the glacier melted, meltwater would carry sand- and gravel-sized particles to settle
around the ice blocks. On occasion, meltwater lakes were contained behind an
ice dam, the sudden failure of which would release a vigorous flood of water
that would move sizeable rocks. When the
remnant ice blocks finally melted, what remained were open depressions surrounded
by deep layers of sand and gravel and rocks. Wherever the groundwater table is high
enough, these kettles become permanent ponds, replenished by rain falling on
the surrounding sandy plain. Walden Pond has no surface streams flowing into
it, nor an exit stream leaving it, yet it persists, with a surface level that averages
158 feet above sea level. It rises or drops several feet above or below that based
on previous years’ rainfall and snowmelt.
Maynard’s mill pond and its water level are artifacts of the
mill’s construction and management. When Amory Maynard and William Knight came
looking for a site for a woolen mill in 1846, they each had mill ownership in
the past. They deeply understood water power. Key to the attractiveness of Assabet
Village as a potential mill site was the fact that at Rockbottom (not yet renamed
Gleasondale), the site of the nearest existing dam upstream, was more than four
miles away, so that if they could figure a means to dam the Assabet River to
their advantage, they could back up a large enough volume of water for
year-round operation without interfering with the operation of the Rockbottom
dam.
Where the mill pond is now was originally a swamp; by building
a large dam upstream from where there had been a modest dam at Mill Street, and
also constructing a canal to where the first mill building was built, they were
able to flood the swamp. Lost to unrecorded history (?) is whether a dike or
other construction was needed to prevent the newly elevated body of water from
finding a route to the river that was not through the mill’s waterwheel. The
net result was getting the equivalent of 50 horsepower of ‘free’ power, six
days a week, 52 weeks a year. This was enough initially, but by 1862, coal-fired
steam engines began to augment, and then finally replace, water power.
Wait, wait, where were we? Considering draining the pond. Which
is exactly what was done in 1916-17, when what is now numbered as building #3 was
being built. A temporary dam was erected near the Sudbury Road bridge. A wooden
pipe, a “flume,” resting on a wooden trestle, conveyed water to the mill for washing
the raw wool, providing water for the steam engines, and washing wool again after
it was dyed. There are photographs in the collection of the Maynard Historical
Society showing the pond drained. In winter, people walked across the ice- and
snow-covered bottom. From the photos, an estimate can be made that the refilled
pond is no more than 30 feet deep at its deepest.
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Trestle visible in 1977 when the mill pond was partially drained for building repair (photos courtesy of Maynard Historical Society) |
When construction was completed in 1918 the temporary dam
and flume were removed, but the trestle was left in place, partially submerged,
in case there was a future need to drain the pond again. In 1977, the pond was
partially drained to allow for building repairs. The trestle top was visible
and still looking in good shape. At present, the tops of a few remaining wooden
piles can be seen breaking the water’s surface when viewed from between
buildings #3 and #5. Without knowledge of the original intent, many people
assume that these are the remnants of a railroad trestle. Most of the time, the
pond’s water level is maintained within a small range.
Could, should, the pond be drained again? There is no real
reason to. There is little sediment build-up, because most of the silt carried by
the Assabet Rive to the body of water retained by the Ben Smith Dam settles
miles upstream from the canal. One hundred years ago, people swam in the pond
or skated on the ice. According to town records, some died doing so, but the
bottom of the pond is not strewn with bodies. There are rumors that desktop
computers and other equipment were defenestrated when Digital Equipment
Corporation abandoned the buildings. This has not been confirmed. Unlike the
river, the pond was never a dumping place for old tires. Draining it would
surely reveal bottles and cans, but nothing that is impacting the quality of
the water.
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Remnants of trestle (2001) |
The pond does not stagnate because it is managed; during times
of high river flow, fresh water is allowed in through the canal gatehouse (visible
from the Route 117 bridge) and let out via the old mill works tail race,
visible from Walnut Street. The water level can drop during summer droughts
because no water is allowed to be diverted into the pond when the river flow
drops below 39 cubic feet per second. There was a problem the summer of 2017
when the pond would repeatedly fill to almost overflowing into the Main Street
parking lot even though the canal gate was closed. Turns out a sunken log had
prevented the gate from being completely closed. Scuba divers were hired to remedy
the problem.
Mark envisions an annual kayak day sponsored by Mill
& Main, perhaps with a launch fee going to a local charity.