Hauser Dam Survey
NorthWestern Energy’s Hauser Dam is a hydroelectric facility on the Missouri River 14 miles northeast of Helena. This original steel spillway was under construction starting in 1905 and completed in 1907. A year later, it failed. A second, 700-foot long and 80-foot high concrete spillway reopened in 1911 and is still in existence today.
The project required Morrison-Maierle to replace the old horizontally-designed turbine with a new vertically-designed version in the power house that was built in the early 1900s. In order to design a space for the new vertical turbine, the team tried to use the 1900-era drawings, which had to be pieced together and were minimal at best.
Morrison-Maierle’s surveyors combined some old and new methods to create a clear picture of the dam’s interior. Due to the unique nature of this project, they adopted some creative measures to provide a clear picture for the design team.
The first step involved placing control I-beams on all four corners of the existing unit. Morrison-Maierle surveyors fastened the beams, which were part of the original scan, to the wall with threaded rods that allowed the beams to move in and out. After assessing the beams in the 3D scan, Morrison-Maierle was able to create a perfect 20-foot by 50-foot control grid around the turbine. Small holes were then drilled into the control beams and piano wire was used to create grid lines that could be physically measured from during construction. Because Morrison-Maierle knew the relationship of the centerline of the existing turbine to this grid, the engineering team could now place the new turbine from the same grid based off its designed relationship to the original turbine.
The next step included fabricating a 45-pound milled plumb bob that was hoisted up by a crane in the powerhouse. Morrison-Maierle’s surveyors were able to take the measurements using this method. Since the base of the turbine was 30 feet below grade of the powerhouse floor, they captured all measurements needed to set the new turbine on the floor level using the plumb bob and the grid created by the control beams.
Morrison-Maierle’s surveyors then created a 3D laser scan of the existing horizontal turbine in order to create a model that measured the existing space and was within a millimeter of the exact size. From this model, the engineering team was able to progress and plan the remainder of the project that included the design and specifications of the new vertical turbine, demolish the existing horizontal turbine, and guide the structural, mechanical, and electrical planning and designs. The data provided by these scans let Morrison-Maierle’s team of engineers plan the project and design the new turbine space. It also proved to be crucial for the contractors throughout the construction phases.
The 3D scan was also a way to look at the turbine, penstock, and tailrace as a whole, and not as separate areas of the site. With the drastic elevation changes, and confined space parameters, the 3D scan allowed Morrison-Maierle to survey the entirety of the site in safer manner in about half the time, ultimately saving the owner and client time and money.