Middle Piney Lake was formed by an ancient landslide. Taking advantage of the partial valley fill created by the landslide, irrigators constructed the current dam between 1921 and 1940 to impound additional water for irrigation. The dam impounds 21 feet of active storage, on top of the natural lake. The reconstruction of Middle Piney Dam is needed because it is classified as a high hazard structure due to the potential for loss of life and damage to property in the event of a failure. Middle Piney Dam currently does not meet State and Federal safety standards and therefore has not been allowed to store water (21 feet) for nearly 20 years. If the active storage pool (21 feet) behind the dam was allowed to fill and the dam were to fail, flooding downstream could cause loss of life and damage to the Sacajawea Campground, the Middle Piney Summer Home area which includes 11 privately-owned summer homes, the FS Road 10024 (Middle Piney Road) infrastructure, and one privately-owned irrigation ditch. The State of Wyoming, through the Wyoming Water Development Commission (WWDC), has funded the analysis, permitting, design, and construction of the Project, which will address dam deficiencies, restore the active storage pool, as well as stabilize the access road.
The reconstruction will require the closure of Middle Piney Road just above Sacajawea Campground, as well as the Middle Piney Lake Campground, starting July 9, 2018. The closure will be in place for up to 4 years, due to the short construction time frames at the Lake’s elevation. Reopening is anticipated for the summer of 2022, or sooner if possible. Initially, foot access to the Lake will be allowed. Furthermore, there is currently a plan to permit snow machine access to just below the dam structure all three winters of construction, with the potential to provide snow machine access all the way to the Lake during the winter of 2018/2019. Public safety is the highest priority, therefore access will be continuously assessed as construction progresses and site conditions change.
Upon reconstruction, the dam will be operated and maintained by the Wyoming Water Development Commission and the Middle Piney Watershed Improvement District through a long-term Special Use Permit.