Emergency Re-Construction of Sawmill Brook Culvert on Monument Street

Town Contact:

Justin Richardson, Assistant Town Engineer, 978-318-3213, jrichardson@concordma.gov

General Contractor:

MIG Corporation, Inc.

Project Schedule:

Work began Monday, June 28, 2021 and is expected to continue until the end of August. 

Traffic Implications:

One lane of the roadway will be closed through the duration of the project, requiring alternating lanes of traffic.

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Project Overview:

Background:

On April 29, 2021, Concord Public Works (CPW) responded to a report of unusually high water in Sawmill Brook in the vicinity of 1061 Monument Street. While attempting to remove a suspected beaver dam believed to be blocking the inlet of the culvert, rushing backwater created a sinkhole close to edge of the roadway. CPW and its subcontract stopped the follow of water with sandbags which prevented the road from further washout.

Monument Street is a major arterial route for the Town and Minuteman National Park. A road washout at this location would have directly compromised a 12” water main and service to approximately 150 households, isolate those homes from emergency services as well as potentially impact the agricultural land downstream. There is also a natural gas main in the roadway and a utility pole located immediately over the culvert and adjacent to the sink hole.

CPW prepared and implemented an emergency response that involved a large pumping operation that at first deployed three large pumps to bring the water level down to an elevation that no longer threatened that roadway and utilities. The pumping operation has been reduced to now only running one pump with another pump asking as backup until a permanent solution can be implemented.

Repair:

Through emergency funding approved at Town Meeting CPW has executed a contract with MIG Corporation, Inc. to repair the culvert and its headwalls. Additionally, an engineering firm, Wright-Pierce of Andover, MA with significant experience in culvert design was brought in to evaluate the situation and recommend a remedy.   The permanent repair will involve the installation of five precast concrete box culvert segments matching the existing stone box dimensions to replace the existing, compromised, corrugated metal pipe on the inlet side of the culvert and to extend the culvert downstream for a safer road embankment slope. The design plan can be seen below.

SMB Reconst Design Plan

Construction Updates:

Updates will be provided weekly on the contractor’s progress.

June 28, 2021- July 2, 2021: – MIG Corporation, Inc. has mobilized and has set up jersey barriers and temporary traffic signals to close one travel lane to provide a work area adjacent to the Sawmill Brook Culvert. They have also installed erosion control devices and cleared/grubbed the area where the cofferdam and crane pad will be installed.

July 5, 2021- July 9, 2021: – MIG Corporation, Inc. installed pad to support cofferdam installation equipment and re-established erosion controls in the area of the pad. Sheeting for the cofferdam was brought to the site and stockpiled. A major rainstorm even occurred on Friday (July 9, 2021) and site preparation for the storm was implemented.

July 12, 2021- July 16, 2021: – MIG Corporation, Inc. has installed the northerly side of the cofferdam and is in the process of installing the westerly and southerly side of the cofferdam

July 19, 2021- July 23, 2021: – MIG Corporation, Inc. has installed the three sides of the cofferdam and has been working on attaching the structural supports to the cofferdam. They have also installed the wooden matting on the Easterly/Downstream section of the culvert to reduce the damage from construction equipment, and allow access to the downstream section of culvert.

Construction Look Ahead:

Next week (July 26, 2021- July 30, 2021), MIG will continue the installation of the supports for the cofferdam and begin work on the downstream section of culvert.