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The Altoona Water Authority's consulting engineer is working on a plan to fill part of a 6-foot diameter pipe that the contractor on the renovation of the authority's Bellwood dam discovered recently.
The pipe was installed as a temporary conduit for water in Bells Gap Run to pass through the site during the 1947 construction of the current dam and was never removed -- despite blueprints that called for its removal, according to authority consulting engineer Mark Glenn of Gwin Dobson & Foreman.
Instead of taking it out, workers at the time filled the middle part with concrete, but left 93 feet on the sloping downstream end empty, officials said.
Workers on the current job will need to fill the concrete-encased pipe's interior with fresh concrete to ensure that it doesn't collapse when they pour concrete for a new spillway above -- and to ensure against leakage of reservoir water along or through the pipe after renovation is complete.
Filling the corrugated pipe will be a challenge, due to lack of access at the upstream end of the 200-foot conduit, where the 1947 concrete stopper ends -- and due to the 45-degree downslope of the empty section.
A provisional design calls for pumping the concrete through a pipe from the downstream end, with a smaller pipe running parallel to that, so that air can escape -- to prevent the creation of voids, according to Glenn.
"We're working through options," Glenn told the authority board at a recent meeting.
The plan will need to be approved by the state Department of Environmental Protection.
Workers also recently discovered old wooden cribbing buried in the dam, a leftover from the 1947 project.
"Evidently, the contractor (at that time) covered it up to save costs," Glenn said.
The cribbing will be removed.
"We're seeing evidence of some old construction that hasn't been the best," Glenn said. "We need to deal with that."