Maine contractor, Reed & Reed Inc., recently moved and installed a 4 million-pound replacement for a New Hampshire Department of Transportation (NHDOT) bridge carrying the White Mountain Highway over the Bearcamp River in Ossipee.

The Woolwich contractor has a $16.9 million contract with NHDOT for Project 14749 to replace three 65- to 70-year-old red-listed river bridges on the Highway (Route 16), which traverses New Hampshire’s pristine White Mountain National Forest. The deteriorating bridges carry NH 16/25 over the Bearcamp River, the Bearcamp River Flood Relief Area, and the Lovell River, respectively.

This is the second, and largest, bridge installed by Reed & Reed in little more than a year’s time that utilized Slide-In Bridge Construction (SIBC). In the SIBC process, a new bridge superstructure (deck and beams) is built on temporary supports, usually parallel to an existing bridge that continues to carry traffic. After new abutments and piers have been constructed and the new bridge superstructure is completed, the road is temporarily closed. The existing structure is demolished or removed, and the new bridge is positioned into place on the new permanent supports.

Reed & Reed installed the Bearcamp Flood Relief Bridge in four and a half days using SIBC in September 2019, and the Bearcamp River Bridge in the same timeframe in October 2020. The Lovell River Bridge is being built using traditional construction procedures, that is, the existing bridge is closed, with detours having been previously set up by the contractor to direct travelers during the time it takes to build the entire replacement bridge at the original location.

The Bearcamp Relief Bridge was NHDOT’s first use of SIBC, a form of Accelerated Bridge Construction, and it efficiently and safely moved a 168-foot, 1.75 million-pound structure. And it also provided valuable experience for the same crews, who were next slated to build, slide and install Bearcamp River Bridge – a 400-foot, 4 million-pound behemoth.

While Reed & Reed is building the three bridges, subcontractor A.J. Coleman is performing the earthwork for reconstructing 3.4 miles of Route 16 as part of the 14749 contract.

NHDOT’s Construction Bureau is overseeing the project, with key personnel Including Project Manager Jennifer E. Reczek, P.E., and Contract Administrator Chuck Flanders. Domenic Cyr is Reed & Reed’s Project Manager, while Greg Letourneau is the contractor’s Project Superintendent. According to Flanders, the project was about 90 percent complete as of early January 2021.

Reed & Reed followed the same SIBC procedure for each bridge. They built a new bridge superstructure on temporary supports parallel to the existing bridge, which continued to carry traffic. After new abutments and piers were constructed, and the new bridge superstructure completed, the contractor closed the road for just 84 hours. During this brief window, crews demolished the old structure, and then moved the new bridge into place on the new permanent supports.

But while the SIBC procedure was similar for the two bridges, jobsite conditions were markedly different. The weather for the first bridge’s move was uneventful, while the second was impacted by a rainstorm that temporarily transformed the Bearcamp River from a picturesque stream to a raging torrent.

Such variations in flows are common for the Bearcamp River. The 26-mile river is the largest tributary of Ossipee Lake, which is part of the Saco River watershed leading to the Atlantic Ocean. Bearcamp rises up in Sandwich Notch (elevation 1,420 feet) at the northeast end of the Squam Mountain Range, flows to the southeast, passing near the base of the Ossipee Mountains and enters Ossipee Lake (surface elevation 407 feet). During a significant storm, the river picks up tremendous amounts of water in this 1,000-foot plunge to the lowlands.

“Visibility was horrible while it poured all night,” said Letourneau. “We got an inch of rain, and the water level rose about 4 feet very quickly. We demolished the four pier bents, which were made of exposed H-piles with concrete pile caps. We used torches to cut the steel and excavators to topple them over. Then we had the cranes use vibratory hammers to pull out the remaining H-piles like pulling carrots up out of a garden.

“The storm slowed us down and it took us about 12 hours longer to demolish the old bridge than it would have in good weather, but we made up time when the weather improved,” he said.

As demolition was underway, Reed & Reed had built the new abutments and the two new piers. To support these structures, the contractor had driven HP14x89 piles and 30-inch concrete-filled pipe piles about 120 feet to bedrock. Most of this work was completed while traffic continued on the old bridge. And with demolition having cleared away any obstructions, crews were ready to move the completed new bridge into position.

The new Bearcamp River bridge is a three-span steel-girder bridge with a length of approximately 392 feet and a width of 37 feet. While it is more than twice the length of Bearcamp River Relief structure, its configuration mirrors the latter – two 12-foot travel lanes, two 5-foot shoulders, an 8-inch concrete deck, a barrier membrane, and a roadway pavement of 1-inch bituminous concrete base course and a 1-1/2-inch surface course. T3 steel bridge rails and 2-foot-wide, raised brush concrete curbs are also part of the deck structure. Five welded steel plate girders underlie the deck. The contractor built the new structure adjacent to the existing bridge on temporary, but very heavy duty, support bents.

The temporary bents were fabricated of H-Pile “A” frames that also were driven to refusal at about 120 feet. Adjacent A frames were joined together with diagonal steel bracing, and capped with a pair of horizontal W36x260 steel beams. Half-inch steel plates braced the caps. Workers welded channel steel to the top of the steel caps, providing a roller channel for heavy duty Hillman rollers that were used to facilitate the slide.

Stantec, consultants for the project, designed the move. The massive structure had to slide sideways about 50 feet without cracking the concrete deck.

The demolition and SIBC replacement of the Bearcamp River Bridge was scheduled for an 84-hour window beginning Friday, October 16 at 6 p.m. NH Route 16 was closed to all traffic at the Bearcamp River area. Crews had previously set up the sliding mechanism for moving the new superstructure.

The sliding mechanism consisted of a W14x176 pull beam mounted over the Hillman rollers and a 1-3/4-inch threaded pull rod attached to a 100-ton center-hole hydraulic jack. This equipment was set up at both abutments and both piers.

Jacks were used to lift the new structure off its temporary supports and placed on the sliding mechanism. Next, four 100-ton pull jacks were used to slide the structure over to the new abutments and piers. This 50-foot move was performed in 8-inch increments. When its destination was reached, the structure was again jacked up to allow workers to remove the sliding mechanism and replace temporary bridge bearings with permanent ones. Then the bridge was lowered in place.

Reed & Reed completed all necessary additional work to allow opening traffic of the new bridge at the scheduled time, which was Tuesday, October 20 at 6 a.m. The entire slide-in construction of a 2,040-ton bridge was accomplished in just 84 hours, the same as its much shorter and lighter predecessor.