Bedford Road over Baboosic Brook was a 21-foot span corrugated metal pipe (CMP) arch installed in 1984. Although not on the New Hampshire Department of Transportation’s (NHDOT) Municipal Redlist, it was noted to have moderate corrosion and holes at its inlet. Due to the CMP being severely undersized and the low point of the roadway being located below the 50-year flood elevation, the roadway experienced frequent overtopping due to flooding.
The replacement bridge is a 90-foot span steel girder superstructure with integral abutments consisting of cast-in-place concrete pile caps supported on steel H-piles. The new bridge width is 39.5 feet out-to-out with an exposed concrete deck constructed with stainless steel reinforcing and a 6-foot sidewalk along the upstream side. Replacement of 850 linear feet of 12-inch water line which passes through the bridge abutments was also included. To address the frequent overtopping, the roadway elevation at the crossing was raised approximately 5 feet. The western roadway approach features installation of 300 linear feet of permanent steel sheet piling with a concrete cap to support the elevated roadway construction.
The bridge replacement project was funded by the Town of Merrimack and the NHDOT Municipally-Managed Bridge Aid Program and was completed in September 2020.