Organizers have pulled the plug on a plan to build a single-stream recycling plant, unable to move forward with the $15.6 million construction project after Concord withdrew from the venture last month.

The joint board of the Concord Regional Solid Waste/Resource Recovery Cooperative decided last night, to terminate contracts with outside communities that had pledged to send material to the plant. 

Those votes effectively killed the project, which had been in the works for more than half a decade and had already cost the co-op roughly $3 million. The group was preparing to close on financing and begin construction this spring when Concord, which had previously supported the project, decided to pull out, calling its latest projections too risky.

Concord city officials said they were concerned that the co-op had not quite achieved commitments of 25,000 tons of materials a year from participating communities, considered a threshold for the plant to break even on operating costs. The volatile market for recycled commodities over the past few years also caused worry.

The main issue, city officials said, was a change in the financing model for the plant, which meant that if the plant were to fail, Concord would have been responsible for paying back 41.5 percent of the project's loans, or roughly $4.03 million...