Page 12 - QuakerMillDam

Left and center: images of the interior of the dam, 2002. In
center image, note the exposed bedrock near the western end
of the dam. Right: close-up image of the Tainter gate and fish
ladder, facing northwest (Doug Hawker).
Engineering of the Dam

How the Dam was Designed and they also included a square opening beneath the main

large opening, apparently for water drainage. 19
Following its 1922 reconstruction, the dam was divided
into a main overflow dam that was reportedly 18 feet high The hollow construction of the Quaker Mill Dam most like-
and 196 feet long, a fishway, and a type of radial floodgate ly dated to the original 1914 dam rather than the 1922
known as a Tainter gate. A floodgate is intended to regu- expansion. In later years this interior passage may have
late water flow through a dam during floods. The dam also provided access to the Tainter gate and hoist mechanism;
included two prominent wing walls that extended from the however, the 1914 dam appears not to have had a flood-
west end of the Tainter gate. All of these features have been gate. The purpose for the hollow construction is currently
removed. not known.

The concrete dam was hollow, and was divided into at least The dam was constructed of reinforced concrete that rep-
eight small chambers that were accessible though the pow- resented at least two separate major building episodes and
erhouse foundation. The chambers were separated from additional repairs. The original 1914 dam was reportedly 14
each other by concrete walls that typically had two open- feet high, but it was raised to 18 feet by the Iowa Electric
ings: a large opening near the floor through which people Company in 1922. A third building episode appears to have
could move between chambers, and a small square open- taken place at a later point—dam owner Willard Hawker
ing above the main opening, used for electrical wiring and guesses in the late 1940s or early 1950s—when the dam
possibly also as an air vent. For most of the length of the crest was raised several inches and made level by the use
dam, the doors were lined up in a row so that, with enough of rails from the abandoned Manchester & Oneida Railway
light, one could see nearly from one end of the dam to the nearby. Two openings at the bottom of the dam near the
20
other. However, the west end of the dam, by the fishway and powerhouse were used to drain the upstream pond when
Tainter gate, was built on stone ledges that project from the necessary. These openings were sufficiently large for people
river bank. Because these ledges are higher than the river to use to gain access to the dam’s interior from the down-
floor, the two chambers at the west end of the dam were stream face of the dam rather than through the powerhouse
higher and smaller than those elsewhere in the dam, since base. In addition to these openings, two small square holes
21
they had the same ceiling height over a raised floor. Their were located near the crest of the downstream face. The po-
doors and other openings were also correspondingly higher, sition of these holes near the crest of the dam suggests that

10 University of Iowa Office of the State Archaeologist