Greater Johnstown Water Authority North Fork Dam

Located across the North Fork of Bens Creek, North Fork Dam is a 1000 foot long, 105 foot high, earth embankment dam owned by the Greater Johnstown Water Authority. North Fork Dam, along with other impoundments at Saltlick Creek and Dalton Run, provide over 2.1 billion gallons of raw water storage for the Greater Johnstown Water Authority system which serves over 21,500 domestic, commercial, and industrial customers, as well as several consecutive water systems.

A design project is currently in progress to make modifications to the dam to bring it into compliance with current PA DEP standards. The main components of the selected plan are:

RCC Spillway. A 390 foot wide auxiliary roller compacted concrete spillway will be constructed over the middle portion of the dam embankment
Existing Spillway Alterations. The existing masonry arch bridge over the spillway will be removed and replaced with a new single span bridge at a higher level. A 10-foot high cap extension will be placed on top of the upstream right spillway sidewall to allow it to contain the full Probable Maximum Flood (PMF).
Dam Crest Floodwall. A 4.5-foot high concrete floodwall will be constructed on the dam crest on both sides of the RCC spillway to contain the PMF.
PA DEP has approved the concept plan and final design is underway by Gibson-Thomas Engineering on this project with a preliminary estimated cost of approximately $8 million.


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Gibson-Thomas Engineering Co., Inc. is a multi-discipline consulting engineering firm established in 1916 in Latrobe, Pennsylvania. Our past experience, key staff and commitment to total client satisfaction are the major factors that our clients consider when contracting with Gibson-Thomas Engineering.

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