PEPPERELL -- After months of work, Swift River Hydro is finishing up the installation of their new steel penstock, the 600-foot tube that carries water from the Nashua River to the Pepperell Hydro Plant.
The metal cylinders have been put into place and workers are completing some final assembly and welding; once that is finished, the enormous pipe will be complete.
"Things are going at an incredible rate right now," Bill Fay, president of Swift River Hydro, said.
If everything goes according to plan, the company hopes the penstock will be up and running again around Feb. 11.
"We'll be opening the gate and filling that great big pipe with water," said operations manager Wayne Bailey.
The new pipe will be an improvement over the former penstock, said company employees. The previous wooden penstock, which was installed in 1950, had been leaking in multiple spots and had surpassed its 50-year life expectancy. The former penstock had a 13-foot diameter. The new one has a 12-foot diameter, creating the same amount of power with fewer inches.
Pieces of the steel penstock arrived over the course of October, November and December. Two excavators lifted the tubes into place and construction crews welded them together. The use of the excavators allowed the company to align the pieces with ease.
The steel penstock could last up to 60 to 70 years, said Fay.
"It may outlast us, but it's going to be sitting there as an asset -- a source of green, renewable power," he said.
Because of the strength of the steel, the concrete pedestals that suspend the penstock are fewer and farther between than with the previous penstock. The former pipe was held aloft by cradles every six feet down its length; the new penstock required cradles only every 40 feet. In addition, the old cradles had spanned the width of the tube; the new feet were placed at a width distance of eight feet apart, saving an enormous amount of concrete and allowing the river to move more freely under the pipe.
The old concrete, which had been mixed by hand and poured into molds in 1920, was excavated and disposed of. It was replaced by new concrete feet four feet square.
"We added compensatory storage in that area by doing that," said Fay.
The steel pipe will be more environmentally friendly. The wooden pipe had originally been treated in creosote, a preservative, which over the years had leached out into the water. By the time Swift River Hydro had acquired the plant and penstock in 2000, most of the creosote was gone, but a bit remained. After being removed, the former penstock was shipped to Ohio and disposed of at a hazardous waste site.
The company is also placing environmental pans beneath the transformers for oil containment in case of leaks.
On Wednesday morning, a crane came in to install a new stainless steel turbine in the power house.
Though the penstock is complete, there are still a few items on the agenda. The company hopes to install a new propeller on the center turbine in March. They are also putting in a plunge pool for fish to swim into at the plunge gate. The plunge pool will allow fish a safe landing place when swimming downstream through a notch in the head gate. It will also prevent them from getting caught in the penstock.
As of right now, the project has gone according to plan, said Bailey.
"Every project has its little problems, but nothing we couldn't work out," he said.
By the time the work is complete, the company will have spent about $5.5 million on the project. But it will be worth it, said Fay.
"We're excited to be helping out the town of Pepperell in preserving one of its incredibly great aspects," he said.
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