Salmon Get a Smoother Slide May 2007
Pumping the Skelton Dam Spillway Makes a Good Fish Tale
STURTEVANT, WI (May 1, 2007) – Atlantic salmon make a mystifying lifetime journey, migrating from fresh waters of their youth to feeding grounds in the ocean and then, amazingly, returning to spawn at the same stream they were hatched. In the future, the unique salmon and other fish species on the Saco River should have a smoother trip over the Skelton Dam in Maine. With the strategic use of a Putzmeister 47Z-meter truck-mounted concrete boom pump, Northeast Concrete Pumping fixed a bumpy and deteriorated section of the dam’s spillway, while also adding an extension to the special path taken by the fish.
About 15 years ago, a fish lift and spillway at the dam were constructed so the declining fish population would have free access to their habitat when spawning. Over time, however, the water’s constant forces had eroded over a 100 ft. section of the 280 ft. spillway. Plus, the fish were encountering a treacherous ten foot drop into the river once they reached the end of the so-called fish slide. Other repairs were also necessary at the dam, which connects the towns of Dayton and Saco.
Responsible for the $1.7 million upgrade was general contractor Cianbro Corporation of Pittsfield, Maine, who called upon the experienced services of Northeast Concrete Pumping of Portland, Maine. Both contractors had been involved with the initial fish passage project at Skelton Dam in 1993, and again would prove instrumental in its improvements.
A stressful challenge To ready the site, crews chipped away the weakened spillway section; then they formed and reinforced the two ft. wide by 110 ft. long segment. They also formed a new 60 ft. extension for a more gradual descent into the water. The demanding task in pumping concrete ultimately became a critical factor to the job’s ultimate success.
“We’ve pumped far more complex projects before; however, this one was definitely the most stressful,” says Joe Croteau, co-owner of Northeast Concrete Pumping. “The job had to be absolutely flawless.”
For environmental purposes, not a single drop of concrete could spill into the fresh waters of the Saco River. Inspectors were on-site throughout the entire concrete pumping process to monitor this vital requirement.
“The equipment had to perform without fail,” says Croteau, “because if the pump would have experienced problems or if we would have blown a pipe full of concrete, it would have been disastrous to the environment.” Consequently, the 25 year old concrete pumping company took several preventive steps.
Going the distance Prior to pumping, Northeast surveyed the job. For boom pump setup, a trestle bridge which crossed over the dam seemed logical. However, the overpass proved too narrow for outrigger deployment. In fact, the only spot available to position the unit was on the edge where land joined the north side of the bridge.
“I eyeballed the far distance from the top of the dam’s trestle to the bottom point where pipeline would be attached,” says Croteau. “Then, I walked out the distance across the uneven rocks to calculate how much delivery system would be needed.”
As a result, Northeast scheduled the longest reaching boom pump in their fleet – the Putzmeister BSF 47Z-meter. The pump was a perfect fit, as every inch of the unit’s 151 ft. long boom was effectively used to reach the bottom.
“We positioned the first boom section over the wall of the trestle,” says Croteau. “Then, we placed the last four boom sections at a straight shot down. It was picture perfect for showing the amazing reach depth of the boom.”
At the rocky bottom, the unit’s end hose was connected with 340 ft. of four-inch delivery line to reach the furthest point of concrete placement.
It takes time… To pump the concrete, Northeast made two nerve-racking pours in a slow, methodical process. Three of Northeast’s operators were on-site – one operating the boom pump and the other two meticulously watching the pipeline for leaks or troublesome areas.
To prime the pump and pipe, scale pans were used to catch the slurry. Five-gallon buckets were filled and hand carried to a point where a small truck crane could lift it for disposal away from the ecological site.
On the first critical pour, the crew pumped 58 cubic yards, while the second one required 68 cubic yards. The concrete, supplied by Auburn Concrete of Westbrook, Maine, was a 5,000-psi mix with a special rust inhibitor.
Each pour took nine hours to complete, with only four hours of actual pumping time. The remaining time was spent in setup and tear down, as all pipeline had to be installed in the morning and removed at night. This was a precautionary measure so if flooding occurred during the evening, the steel pipe would not touch the fresh waters.
The alternatives With the complicated requirements in placing the concrete, various alternatives were considered. Although a large crane was an option, it would not have been able to set up in the space afforded nor reach the extreme 400 ft. distances needed to bucket the heavy concrete.
Using a trailer-mounted concrete pump was also considered; however, it would have required extending 110 ft. of stand pipe over the trestle bridge and then straight down in mid-air for connection to the delivery system below. Even though a trailer pump had handled the initial project about 15 years ago, this approach was now viewed too labor intensive and had questionable safety concerns.
Northeast’s co-owner Brian Laughlin personally pumped the original fish passage project in the early 90s with a trailer pump. He says, “Fortunately, with the longer reaches of today’s boom pumps, projects which once required excessive pipeline and tricky maneuvers can now be handled in a more efficient and safe manner.”
“As a result, our 47Z-Meter boom pump proved to be the most logical and cost-effective approach for handling the job,” adds Laughlin.
Laughlin, equipped with vast construction experience, started Northeast Concrete Pumping in 1982. His aggressive efforts resulted in rapid company growth; and in 2002, he decided to partner with one of his first employees, Joe Croteau.
The company continues to go the extra mile to ensure professional pumping services, as is evident from the repeat business gained almost two decades later when the same dam required enhancements. Today, the fleet owned by this well-respected organization comprises 15 modern Putzmeister pumps, operating from two locations – Portland, Maine and Seabrook, New Hampshire.