The bed of the stream at the site selected for the dam is composed of
solidly packed gravel. It was not considered advisable to lay timbers
on such a foundation, so a ditch about two feet deep and one and
one-half feet wide was dug across the creek bed and filled with
concrete, to which a heavy timber was securely bolted, to form the
upstream sill for the super-structure. The downstream side was
supported on a sill of heavy timber whose ends were embedded in the
concrete walls, or abutments, at either end of the dam and whose middle
portion was supported by posts, spaced six feet apart, which in turn
rested on large blocks of concrete placed in the bed of the creek.
This downstream sill was about two and one-half feet higher than the
upstream sill. A horizontal floor of double plank extending twelve
feet downstream from the upstream sill and supported by the concrete
foundations under the downstream sill formed an apron for the water to
fall on. This prevents back-washing under the dam. A double layer of
heavy plank was then fastened on the two sills, forming a sloping face
on the water side of the dam. On the upper edge of this plank-facing,
at the crest of the dam, are placed flashboards, one foot high and
extending the full length of the dam, thirty-six feet, but divided into
six sections, each six feet long. Each of these sections is hinged by
the lower edge to the crest of the dam, while the upper edge is held
from tipping over by chains fastened to cast-iron lugs located about
halfway down the planking. The chain is held in these lugs by pins
which are connected by rod and chain to a capstan, or spindle, located
at one end of the dam, and are so arranged that by turning the spindle
the pins will be drawn successively, thereby letting the flashboards
down one at a time. The idea of this arrangement is that, when a flood
is rising, the capstan may be turned with a heavy lever crank, winding
up the chain and pulling down the flashboards one at a time, to give
more space for the flood to pass through so as to prevent the water
upstream from the dam from rising too high. This plan has prevented the
washing away of Mr. Miner’s power house on several occasions.
[Illustration: Farm Power House on Oriskany Creek