PLSO The Oregon Surveyor March/April 2022

16 The Oregon Surveyor | Vol. 45, No. 2 Featured Article Staking The Ochoco Dam By Dick Bryant, PLS (ret.) When you have been connected with the surveying profession as long as I have, you are bound to have worked on projects that stick in your mind. When my partner, Tom McCullough, and I were in the business we covered a lot of territory. This included cadastral surveys, running control for large mapping projects, finding and remonumenting public land survey corners, subdivisions, and utility construction. If you have ever flushed a toilet at the Diamond Lake Campground or the nearby Broken Arrow Campground, you can thank our company, at least partially, for that convenience. Many other projects come to mind. Probably the job that sparked themost interest for me personally was when I was working for David Evans & Associates out of Bend. DEA was hired by a contractor to provide the construction staking for the renovation of the Ochoco Dam east of Prineville. But before we get to that story, a little history is in order. The damwas built by a group of ranchers in 1920 in order to impound water for irrigation. It was an earthen dam and tomy understanding was constructed as a community do-it-yourself project. My research showed that certain design standards apply when it comes to building this type of dam, none of which seemed to have been followed by the original builders. The basic rule is to construct anearthendamsowater will not flow through it, under it, around it (I refer you to the Teton Dam in east central Idaho, circa 1979), or overtop it (Johnstown, Pennsylvania flood in 1889). This is done by keying both abutments well into the existing walls on both ends of the dam, doing a cutoff trench below the dam to not allow water to flowbeneath it, building a vertical impervious layer inside the damto prevent water from passing through it and last, adding in a spillway so the damwill not be overtopped during a flood. Another safeguard is to not build the dam on a fault. Apparently all of these design criteria, except a spillway, were either not known or not followed. There was an ancient rock slide at the right abutment which allowed Start of original dam construction using a water cannon.