The Town of Merrimack desired to replace the CMP arch structure and elevate the roadway above the 100-year flood elevation to mitigate the overtopping of the roadway. The hydraulics and hydrology study for the Baboosic Brook identified that the location of the crossing is controlled by backwater conditions and that raising the roadway would require a substantially larger crossing than that of the original structure. Additionally, underlying soils conditions at the site would have required extensive excavation operations for construction of oversized spread footings to support the new abutments, wingwalls and superstructure.

The Quantum Construction Consultants project design team and the Town Engineer agreed that the selection of the NEXT beam in conjunction with pile foundations and integral short pile cap abutments, offered the best solution for constructing the longer span crossing. Furthermore, the use of the precast NEXT beam would enable accelerated bridge construction (ABC) throughout the winter months thus not requiring the traditional winter shutdown. This ABC approach reduced construction time thus reducing project costs and minimizing road closure time lines.

Each integral abutment and wingwall is supported by single line of steel H-Piles driven to approximately 90-foot depth. The cast in place short pile caps decreased the amount of excavation needed for construction, and reduced the need for dewatering during construction of the abutments and wingwalls. Scour protection for the piles and substructure was provided through placement of keyed stone fill within the channel and around the structures.

The Town was so extremely pleased with this NEXT Beam bridge replacement project they celebrated the bridge completion with an official ribbon cutting ceremony.

All the precast components were manufactured by J.P. Carrara & Sons, Inc. of Middlebury, VT.

Timeline:
Construction Start Date – November 01, 2012
Beams Erected Date – February 21, 2013
Project Completion Date – May 08, 2013