Hydrodemolition Technology Deployed to Restore Wyoming Dam
The more than 90,000 dams in the U.S. serve a number of important purposes, including drinking water, irrigation, hydropower, flood control, and recreational opportunities. Unfortunately, the average age of a U.S. dam is 56 years, and 2,170 dams are classified as being “deficient, high-hazard potential.” It is hardly surprising, then, that the American Society of Civil Engineers recently gave the U.S. dam inventory an overall grade of “D.”
Fortunately, however, the latest hydrodemolition technology provides an effective and efficient method for repairing the country’s aging dam infrastructure. A recent project to rehabilitate the Alcova Dam in Wyoming demonstrates hydrodemolition’s value proposition for preserving these mission critical assets.
Owned by the U.S. Bureau of Reclamation, the Alcova Dam is an earthfill structure situated along the North Platte River in Central Wyoming. The dam is utilized for water storage and hydroelectric power generation.
NW Construction, tapped to manage and execute the Alcova Dam rehabilitation project, subcontracted with hydrodemolition specialist, Penn Hydro, Inc., to perform the removal of deteriorated concrete. Penn Hydro’s scope of work consisted of concrete removal from the spillway floor, walls and wall caps. Penn Hydro was also responsible for the collection, treatment and disposal of the hydrodemolition wastewater.
The project presented some unique challenges due to the terrain and the weather conditions. The dam’s spillway includes some very steep grades, vertical walls up to 60 ft (18m) high, and wall caps, all of which contained deteriorated concrete in need of removal and replacement with a fresh overlay. The Bureau’s recommendation for commencement of work on the spillway was October 2020—a time of year when lower water levels of the North Platte River provide the safest conditions for workers. However, the late Fall start could also prove to be difficult given the cold weather in Wyoming at that time of year.
Penn Hydro needed a hydrodemolition robot that was highly versatile. and would perform consistently in these challenging conditions. The company Conjet Automated Concrete Removal (ACR™) Robot 557 to handle this complex project. The 557 has a number of strengths, including its versatility, productivity and the high level of customer support provided by Conjet’s team located in Sweden and North America.
Penn Hydro’s initial scope of work yielded a schedule of roughly 10 weeks. The concrete strength of the spillway floor and walls was tested to be 5,000 psi. The volume of concrete removal was estimated at 209.2 yd3 (160 m3) of concrete on the spillway floor and walls for an average depth of 6 in (15 cm). An additional 140 yd3 (107 m3) of concrete was estimated for removal on the spillway wall caps for an average depth of 15 in (38 cm).