Residents of Tate County in north Mississippi are eagerly awaiting completion of the new, $22.7 million U.S. Highway 51 Bridge over Coldwater River this spring, after having endured detours and additional traffic congestion since the Mississippi Department of Transportation (MDOT) closed the old bridge March 2016.

A Growing Community

City of Hernando Mayor Tom Ferguson anticipates the new bridge will not only improve mobility, but also help to support continued growth in the area.

Hernando is considered something of a bedroom community to Memphis about 30 miles north, and has experienced rapid growth in recent years. With a population of about 18,000, the city is anticipating more growth with the 1,139-acre upscale Hernando West community development project that is currently under construction. Hernando also boasts several recent improvements such as a farmer's market, bike- and pedestrian-friendly streets, and a new, one-acre dog park located in the city's Renaissance Park.

"Since the old bridge was closed, I would say that 90 percent or more of our residents south of here have to come to the first I-55 exit here in Hernando, which has created some traffic congestion," Ferguson said. "Farmers have been forced to drive their equipment all the way to Eudora around the dam, and Northwest Community College students and teachers have to go north about 5 to 7 miles and then go back south about 14 miles."

Retiring the Old Bridge

The old bridge was originally built in 1935 under the Works Progress Administration as part of a vast highway that would run from New Orleans to St. Paul, Minnesota, and increase tourism and commerce.

Flooding in March 2016 caused "a great deal of scouring, removing up to 12 feet of streambed material from several pile bents on the north end of the bridge, and causing three of them to settle," said Melinda L. McGrath, P.E., MDOT's Executive Director. "After inspection, MDOT determined that repairing the bridge was not a feasible or economic solution because of the damage and the bridge's low sufficiency rating."

MDOT already had plans to build a new U.S. 51 Bridge over Coldwater River, with construction beginning November 2016. Consequently, the department had already begun the design for a replacement bridge. MDOT enlisted the services of Garver Engineering of Jackson to assist in completion of the bridge design. 

"The project replaces the old, 1,100-foot-long bridge with a new, 2,000-foot-long bridge and raises the roadway elevation by 4 feet to prevent future flooding," McGrath explained. 

Designing Around the Environment 

In addition to being longer and at a higher elevation, the new bridge is designed to reduce the substructure footprint to the wetland on which it is located by using as many locally available systems as possible, such as Bulb T girder beams, reinforced cast-in-place concrete and coated steel pipe piling, McGrath explained. The new bridge consists of 11, 120-foot-long by 63-inch-tall, pre-stressed, Bulb T girder approach spans supported by cast-in-place, reinforced concrete caps on 30-inch-diameter steel, concrete-filled, pipe piles.

"There are nine approach spans to the south of the main spans and two approach spans to the north of the main spans," McGrath said. "The main span is a 615-foot-long unit that is comprised of three (180-foot, 255-foot and 180-foot) spans of weathering steel welded plate girder units supported on cast-in-place reinforced concrete caps on 72-inch-diameter drilled shafts. The deck is cast-in-place reinforced concrete."

The weathering structural steel main spans were used because they required no field painting, McGrath explained. Additionally, due to the inaccessibility of the area, the weathering steel will also reduce future maintenance cost. The bridge was also designed to resist seismic loadings.

Working Around Severe Weather

MDOT let the project in May 2016, six months ahead of the original schedule. L&A Contracting Company of Hattiesburg, Mississippi, won the contract and received the Notice to Proceed July 12, 2016. The contractor began demolition of the old bridge in August 2016 and completed that in early December 2016.

The threat of Hurricane Harvey, which ultimately made landfall near Rockport, Texas on August 25, caused L&A some delay.

"They were forecasting 12 to 14 inches of rain, so we had to get all of our equipment out of the river bottom and up on the hill," said Charlie Sutherland, III, L&A's Vice President of Operations. "We lost about seven days."

The contractor made up the lost time by working weekends.

"The best part about this project is that the road is shut down, so we haven't had to deal with a lot of traffic on the job," Sutherland said. "The biggest thing we had to deal with, as far as the public, was all of the sightseers."

Setting the Girders

Many of those were on hand when L&A used a 275-ton Manitowoc crane and a 230-ton American crane to set the structural steel across the river.

"That was one of the highlights of the job," Sutherland recalled. "We set the steel girders for the flanking span on the south side of the river first and then moved to the north side, the Hernando side, and set the flanking span there. The following week we brought the drop-ins that closed up the hole."

Using the two cranes, L&A picked the steel girders off the truck, placed them on sectional barges in the river, and then slid them into place.

"Each of the steel girder spans were 130 feet long and weighed 72,000 pounds," Sutherland said. "We placed five in one week."

Sutherland, who's been with L&A since 1992, followed the company tradition of working his way through the firm from the ground up and learning every position. He started out as a laborer, moved to being a pile driver, and then transitioned into hanging structural steel.

"That's what I know best, big lifts," he said. "Those big, heavy lifts are what I get up and go to work for every morning. It's the most interesting and challenging part, and that's what separates most of the contractors when they bid on work is the difficulty of crossing the river."

A Focus on Safety

L&A has been building bridges since 1947, and has a portfolio of successful projects all over the Southeastern United States, Sutherland said. Additionally, the Coldwater River Bridge project is located inside what he calls their "magical bubble," within a five-hour drive of the company's Hattiesburg home. L&A's sister company, F-S Prestress, LLC, fabricated all of the concrete girders for the project.

Since the project is on a flood plain, the job specifications included provisions for turbidity barriers and a floating silt fence along the length of the entire project to contain any possible erosion.

When the contractor was performing a lot of earthwork over the summer, manpower peaked at 48. By the beginning of November, L&A had already begun demobilizing, and the workforce was down to 30 men. At that time, L&A had zero lost time accidents.

"The job is 100 percent tied off," Sutherland said. "That's not even negotiable."

All of L&A's foremen and superintendents go through CPR training, and L&A conducts safety talks every morning "to keep everybody's mind awake with what's going on around them," Sutherland added.

"My main concern is to get everybody home safe," he said. "I want everybody to leave the job just like they came in that morning. If you don't take care of your people, they won't take care of you."

He added that L&A has been building bridges for so long that "we just go and try to build the very best bridge we can build wherever we go, get it on time and within budget, with everybody safe, and then go home."