Mile 106.8 - Just before this dam is something you don't see that often
on the canal: a hill! The canal starts shallow but gets very deep as
the hill progresses and leads to the dam.
There's a plaque that reads:
Floods occur at regular intervals in the Potomac Valley. Between 1829
and 1998, there have been 144 recorded floods or high water occurrences. Repairing
flood damage was a continuing battle for the C & O Canal Company and is still
a problem for the National Park Service. During periods of low water, the
remains of the original crib and rubble dam, destroyed by floods, can be seen downstream
from the present dam built in 1857.
In 1998, the guard lock and flume were filled with soil to halt the collapse
of the stone walls. A section of towpath that was collapsing was replaced
with "Roller Compacted Concrete (RRC)" which is a concrete mix with a
small amount of cement and a high amount of gravel. The stone for the aggregate
was acquired locally to the match the stone already used here. The RRC is
spread and compacted by a roller and does not require formwork like conventional
concrete. By filling the lock and bypass flume, and reconstructing the towpath
and guard dike, the National Park Service is trying to protect the historical structures
here from future flood damage.
towpath rests on a concrete platform. This is what the plaque referred to
as the "towpath and guard dike". If you stop by the
Williamsport Visitors' Center, you can see a photo of the stone wall it replaced.
Past the small bridge over the canal, the canal stops for a couple of miles. Use
the bridge to cross over to the other side where the towpath continues.
This is the inlet lock that was filled in. Canal traffic from here to Lock 45 was
routed to slackwater along the Potomac River via this lock.