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Taking to the Sky at Mount Morris Dam: innovation in the face of a challenge By Kalli Rasbury, Modern Contractor Solutions and Bruce Sanders, Public Affairs Office It took the Buffalo District four years from 1948 to 1952 to construct Mount Morris Dam at a cost of some $25 million dollars. Since that time, this 1,028-foot-long concrete sentinel on the Genesee River has prevented over $1 billion in flood damages to the City of Rochester, NY, about 35 miles downstream. In the intervening 57 years, approximately 1,500 cubic yards of dirt, trees, and debris accumulated along the south training wall of the dam, making it impossible to inspect the wall and ascertain the condition of the concrete and the integrity of the structure.
Buffalo District went out for proposals to remove the accumulation from the training wall and along the fillet of the south edge of the dam. But there was a catch: while workers could access the wall using the dam’s elevator and stairs, the only apparent approach for equipment was across the Genesee River itself. The “what” of the project was clear from the beginning; the “how” was another matter. Along came good old American ingenuity. When Manno Construction, Inc., decided to bid on the contract, they were basically flying blind—no pun intended. Three scenarios emerged during the bid preparation process. It seemed obvious that the best way to get equipment to this relatively inaccessible site was through the air. Other options included using a barge with a crane on it or using a combination of both a barge and a helicopter. Manno decided to start by using a helicopter to move the necessary equipment to the site. This would give them the opportunity to try the helicopter for a day and see if it could meet the production rates needed to finish the job on time. There was never a need to explore other options. The helicopter, supplied and operated by Construction Helicopters, Inc., out of Ypsilanti, Michigan, proved to be the perfect approach. The helicopter used for the project, a Sikorsky 61, has a 9,000-pound total lifting capacity while the heaviest equipment used for the project weighed in at 8,000 pounds which included: a Hitachi 270LC excavator; a Cat D-6 bulldozer; a Bobcat T-190 and Bobcat T-200; two Bobcat Mini Excavators; and three custom 2-yard, self-dumping bins. The installation of fall protection and the access road improvements took approximately 5 days to complete. The actual debris removal took 5 days, including mob and demob of the helicopter crew and equipment. The Manno team began by clearing the trees and other woody debris by hand from the work site using military-grade cargo nets to bundle the debris. On the helicopter’s first trips, it would move a piece of equipment from the staging area to the work area, then they would attach the prebundled trees and woody debris for the return trip. By the time all of the equipment was brought to the site, all of the woody debris was gone. Next, the Manno crew began concentrating on the dirt, brush, and other debris that needed to be removed. They used the two main excavators and two tracked skid steers on the wall, which was roughly 300 feet long. They used an excavator and a skid steer on each side of the wall, with a self-dumping bin in the middle. This allowed them to work in from both directions. According to Denny Cornell, Manno Construction project superintendent, “We needed that amount of equipment just to keep up with the cycle times the helicopter was able to achieve. The helicopter could take a bin to the other side and come back in an average time of 2 minutes, 35 seconds. I think the fastest trip it made was in 1 minute, 45 seconds.” |
The self-dumping bins were a key to the helicopter’s quick turnaround time. To transport a bin, the helicopter was connected to the lifting handle of the dump bin and airlifted across the river to the staging area, where it was lowered to the ground until the arm on the bin was tripped and it dumped itself. Then the empty bin was returned to the work area. Once the flight activities began, the removal activities continued virtually nonstop until sunset. The helicopter was refueled approximately every 2 hours, giving the crews short breaks throughout the day. The lunch meal was brought to the crew to minimize downtime and to maximize production. This project was unique in that it required many times the number of loads the construction helicopter would typically transport on a project. A typical job might call for 60 loads, whereas this job called for 750 loads to be transported. Construction Helicopters gave Manno a very conservative production estimate on the front end, and they were able to meet and exceed that estimated production rate on the job. To address the significant challenges of the Mount Morris project, Manno Construction held a variety of preparatory meetings to discuss and coordinate work activities. The crew worked from sunrise to sunset to take advantage of all daylight hours available. Construction Helicopters provided a ground team member, who would start the day by being shuttled to the removal side of the project and being briefed on the day’s work. This team member also served as a rigger, with help from one of Manno’s crew members also assigned to that task. The ground team member was in direct communication with the helicopter crew throughout the project. Another important factor was safety coordination. Not only was the Corps involved, but because of the use of a helicopter, the New York Office of Parks and Preservation, and local fire and police departments also had to be in the loop. The key to overall success was the intricate control over helicopter activities. Manno had to get enough equipment to the site to keep up with the helicopter’s high production rates while factoring in that equipment choices had to be limited by the amount of weight the helicopter could lift. This was a unique job, so there was no prior project on which to base equipment decisions. In the end, it was decided to go with the smallest equipment that could accomplish the work at the necessary rate. NEWS YOU CAN USE Lake Ontario Ordnance Works
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