SE-137 69 Österhaninge
There are more than 90,000 dams in the U.S. They make up a critical aspect of the U.S. infrastructure system, serving 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.”1 It is not surprising 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.
The Alcova Dam is owned by the U.S. Bureau of Reclamation (the “Bureau”). The Alcova Dam is an earthfill dam situated along the North Platte River in Central Wyoming. The dam is utilized for water storage and hydroelectric power generation.
Through a request for proposal (RFP) process, the Bureau chose NW Construction as the general contractor to manage and execute the Alcova Dam rehabilitation project. NW Construction then 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 feet in height, 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. This time of year was selected due to the lower water levels of the North Platte River and safest conditions for all involved. However, the late Fall start could also prove to be difficult given the cold weather in Wyoming at that time of year.
Brad Beaudry, project superintendent for NW Construction, stated that he chose Penn Hydro as the hydrodemolition subcontractor because of its prior experience and expertise with complex dam projects. Brad also noted that hydrodemolition, when compared to other concrete removal methods he evaluated when planning this project, was “much faster” and the other alternatives “could not touch hydrodemolition in terms of speed.” According to Brad, the project would have been “nearly impossible” using any other concrete removal processes or technologies.
Penn Hydro needed a hydrodemolition robot that was highly versatile and would perform consistently in these challenging conditions. Penn Hydro chose to use its 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 160 m³ of concrete on the spillway floor and walls for an average depth of 15 cm. An additional 107 m³ of concrete was estimated for removal on the spillway wall caps for an average depth of 38 cm. “However, the quantity of removal on the spillway floor and walls continued to grow as additional repair areas were identified,” according to Penn Hydro.
Penn Hydro is headquartered in Pittsburgh, Pennsylvania, approximately 1,600 miles from the Alcova Dam jobsite. The Alcova Dam jobsite itself is relatively isolated, being approximately 30 miles from the nearest major town of Casper, Wyoming.
Due to the remote location of the Alcova Dam, it was imperative that Penn Hydro’s operators had well-functioning equipment as well as additional spare parts and materials to ensure successful execution. There was a significant amount of preparation that Penn Hydro had to undertake in order to ensure minimal downtime once the project was underway.
Before mobilization from Pittsburgh, Penn Hydro carefully examined and serviced its Hammelmann pump and Conjet 557 robot. Conjet assisted with the preparations by making its Swedish engineering team available for virtual collaboration with Penn Hydro. In addition, Conjet sent its customer success manager for North America, Tim Best, to visit Penn Hydro’s Pittsburgh headquarters prior to mobilization to ensure that the Robot 557 was working properly. While the Alcova project was ongoing, Tim also visited the jobsite to ensure that the robot was continuing to perform up to Conjet’s and Penn Hydro’s operational standards.
In early October, the Penn Hydro team, along with two tractor trailer loads of equipment, departed Pittsburgh to make the 1,600-mile trek to Wyoming.
Once onsite in Wyoming but just prior to Penn Hydro’s commencing operations, the Bureau performed a second survey. This second survey uncovered additional areas for repair along the floor of the spillway. The Bureau decided to proceed with hydrodemolition on the newly discovered repair areas as well.
As operations began, the spillway was found to have a large amount of algae present that needed to be removed before work could commence. Also, the late Fall weather became very cold, meaning that there was often snow and ice to contend with. Using only the Conjet 557 and no additional attachments or tools, Penn Hydro was able to operate on extremely steep sections of the spillway under sometimes icy conditions. The Penn Hydro team was also able to reach the high vertical wall sections with the 557’s standard, multi-purpose arm. Finally, the structurally compromised wall caps had to be removed, and the Conjet 557 quickly transitioned to operating on an uneven dirt platform above the dam while using its arm to reach out and over the wall caps.
Penn Hydro’s expertise, equipment versatility and production rates were considered crucial in the effort to expedite the schedule given the expanded scope. Mr. Beaudry stated that he has been “impressed with Penn Hydro’s operation of the Conjet 557 based on its production rates, and also because of its versatility in being able to quickly switch from horizontal to vertical removal” using the robot’s standard arm. Penn Hydro’s President Oliver Scigliano, likewise said that the Conjet 557 “performed extremely well on this project. The versatility was huge and the robot did a phenomenal job of dealing with challenging, unique terrain and conditions.”
Safety was also a major priority on the Alcova jobsite. Because the Conjet 557 can be operated using a wireless remote control, the robot operator was able to stand a safe distance away from the robot itself (up to 30 feet), which minimized the possibility of being hit with flying debris from the demolition. No injuries occurred during the project.
The concrete removal was completed by Penn Hydro in mid-December, a full week ahead of schedule. The early completion was especially impressive given the fact that the project ultimately required even more concrete removal than originally estimated. Mr. Beaudry commented that, based on the impressive results from Penn Hydro and the Conjet 557, he believes that NW Construction is likely to start using hydrodemolition on more of its heavy civil projects in the future.
There is a massive global need for the rehabilitation of heavy concrete infrastructure, and as the Alcova Dam renovation project has demonstrated, hydrodemolition is an emerging hero in this battle to preserve such critical assets.
CUSTOMER: Penn Hydro
MISSION: Repair dam with hydrodemolition
ROBOT USED: 557 MPA
Conjet ACR™ robot 557 MPA features the latest technology in hydrodemolition. Combining the reach of Robot 367, the flexibility of Robot 327 and the diesel engine of Robot 437, this robot has it all.
Fill out the form and we will get back to you with a tailor-made offer to your specific needs.