CS7A - Concurrent Session 07A: Wanapum Dam Repair: A Challenge For Con-Tech Systems USA Inc.

The Wanapum Dam is a hydroelectric project located on the Columbia River downstream (south) from Vantage, WA, where Interstate 90 crosses the Columbia from Grant County into Kittitas County. It is owned by the Grant County Public Utility District (PUD).

On February 27, 2014, the PUD discovered a 65-ft long by 2” wide crack that spanned the full length of Monolith 4, which required an emergency action of lowering the water level 26 ft to reduce the pressure on the gated spillway structure.

Con-Tech Systems (CTS®) was awarded for the supply of DCP Strand and Bar anchors, By Nicholson Construction. The length of the multiple, 61 strands, per anchor, and the underwater placement and stressing of the 3” DCP bar anchors made this very challenging.

A total of thirty-five, 61-strand anchors, with length up to 260 feet, were installed through the monolith piers with lock-off loads of 2,500 Kips. Post-Tensioning the anchors was performed with a 2,200-ton single stroke jack with a stroke length of 35 inches; maximum elongation measured 21.3 inches for the longest anchor. In addition to the strand anchors, 69 solid 3” diameter bar anchors were installed, of which most were installed below water through the ogee spillway on the upstream side of the radial gates.