What Is Happening in the NE Corner of Nagog Pond?

The floating barges, pipes, cranes, construction activity and traffic diversion at the corner of Great Road and Nashoba Road are in support of the first phase of the Town of Concord’s renovation of their Nagog Pond water treatment facility: extending and replacing the intake pipe.

For many years now, the Town of Concord has been trying to upgrade its water treatment facility at Nagog Pond. Concord’s current plan is a phased effort, beginning with removing a portion of the old cast iron intake pipe and replacing it with new, high-density polyethylene pipe.

The new intake pipe will be much longer than the existing pipe (see map, below), extending nearly to the Acton–Littleton town line. The current phase of work covers only the section of pipe that lies offshore from the island at the mouth of the cove. Replacement of the inboard section of pipe, which will require damming and draining the cove, is being left for a future, as-yet-undetermined date.

At the end of the new pipe, there will be a structure to hold the actual intake — the opening where the water enters the pipe — up off the pond bottom and out of the mud. As a condition of its Massachusetts permits, Concord is required to build the new system with an intake that is at the same elevation as (or higher than) the existing intake, so that the new system cannot pull the pond level down any lower than the old system.

The elaborate floating barge system at the corner of Great Road and Nashoba Road was negotiated with Acton’s Conservation Commission as a way to stage the assembly of the pipe and the construction of the intake structure with minimal disturbance to the pond. Concord’s property at the southeast end of the pond, around the treatment plant, did not provide adequate access for heavy equipment; thus the staging is being done at the northeast end of the pond, where the road runs right next to the pond. As each section of the assembly is completed, it will be floated out into place and installed by divers.

There are some checks and balances in place to help ensure that the issues raised by Nagog abutters and other Acton residents over the years are being addressed. To keep stakeholders informed, Concord posts project updates on its website; members of the public can sign up on that page to get email notifications when new updates are posted. The Acton Conservation Commission held a site walk on April 20 to ensure that its conditions were being met. Unlike most site walks, this one was posted as a public meeting, and the presence of several knowledgeable members of the public added an extra measure of transparency. A licensed surveyor was contracted to ascertain the depth of the existing intake and will return to survey the new intake; those surveys will be submitted to ConsCom when Concord comes back for its Certificate of Compliance.

• Barge description and plans as submitted to the Acton Conservation Commission
• Green Acton coverage of Nagog Pond issues