CAMDEN — As the bid package for the new Camden-Rockport Middle School to be built on Knowlton Street have been circulating, engineers associated with the project are refining at least one bid option: To heat the new building with wastewater from the neighboring treatment plant that processes all of Camden and some of Rockport’s sewage. The costs have come down from what was originally estimated, and the option has gone back out to construction companies bidding on the job.
Bids on the entire $26 million project are due back to School Administrative District 28 offices by May 16.
Addenda to the base bid package are being sent out this week, and in addition to the heat exchange system from the sewer treatment plant there alternate options SAD 28 is seeking, which include sodding the fields and a snow melt system.
Heating the new 83,400-square-foot school with wastewater requires a sewer thermal pump installed near the Camden Wastewater Treatment Center, which is next to the middle school campus on Knowlton Street.
Talk of possibly heating the new building with wastewater started in the summer of 2017 and architects presented plans to the Camden-Rockport Middle School Building Committee. But, over the past year, the idea had been labeled too expensive and would drive up project costs, which had been approved by voters at $26 million. The wastewater heating exchange system had been tagged at $500,000 and more.
But that has changed, as the Camden Select Board learned May 1 at a regularly scheduled meeting held in the Washington Street Conference Room.
The cost now is estimated at $250,000, according to Oak Point Associated Mechanical Engineer Matt Albright, who told the Select Board that new school’s main heating source would be propane gas, with radiant heat flooring.
With the installation of pipes from the sewer plant and the circulation of thermal wastewater through the building, however, heating costs could be almost entirely shifted from propane to sewer water.
Building the system would entail capturing wastewater at the treatment plant, running it through a heat pump, and then piping it 800 feet along a sewer-thermal trench dug beneath the soccer field to a web of pipes that are to run around the outside of the school.
The system would use 150 to 200 gallons of water per minute, and the return pipe would send the brown water back to the treatment plant, and then down to the harbor, where Camden’s treatment outflow is deposited.
“If we can pull this off it is a great thing for the school,” said Select Board member Marc Ratner. “It is exciting.”
The return on investment would take approximately 20 years, said Albright, with a savings of $10,000 to $15,000 per year.
But the resulting benefits include a school building that would be heated primarily from the wastewater.
“It will help cut heating costs,” he said. “It could heat the building all year long, while ventilation would have to handled by propane. It’s quite a savings.”
Additionally, if the alternate heat exchange option is approved, then other cost savings would be recovered as the propane heating system would require smaller boilers, said Albright.
Ratner made a motion to support the option of the wastewater heat exchange system for the new school, as long as it is funded by the school district.
All members — Alison McKellar, Bob Falciani, Chairman John French, Ratner and Jenna Lookner — approved the motion.
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