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Manntown Bridge Project Progresses

Tue May 01, 2012 - Southeast Edition
Cindy Riley


Photo courtesy of the Florida Department of Transportation.
Curing compound is sprayed on the new concrete surface of the County Road 125 Manntown Bridge in Baker County.
Photo courtesy of the Florida Department of Transportation. Curing compound is sprayed on the new concrete surface of the County Road 125 Manntown Bridge in Baker County.
Photo courtesy of the Florida Department of Transportation.
Curing compound is sprayed on the new concrete surface of the County Road 125 Manntown Bridge in Baker County. Photo courtesy of the Florida Department of Transportation.
As part of the County Road 125 Manntown Bridge replacement, the concrete screed machine worked six hours overnight on the concrete pour. Photo courtesy of the Florida Department of Transportation.
FDOT project engineer Jason Bordner points out the section of newly poured concrete on the County Road 125 Manntown Bridge replacement in Baker County. A Kobelco CK 2500 crane walks alongside the new bridge on the work trestle to deliver materials to the other side of the bridge.
Photo courtesy of the Florida Department of Transportation Photo courtesy of the Florida Department of Transportation.
The aging Florida bridge, seen here before construction began, dates back to the early 1950s and needed to be replaced.

Despite a change in the original plans, the replacement of Florida’s Manntown Bridge on County Road 125 in Baker County is progressing on schedule, according to the Florida Department of Transportation (FDOT).

The 60-year-old structure, which is situated over the south prong of the St. Mary’s River, had been scheduled to remain open during construction of a new bridge; however, it had to be closed to all traffic in mid-January, and most likely won’t reopen until late spring or early summer. The closure prevents an unsafe condition for motorists while the bridge is being replaced and the roadway approaches are being rebuilt.

“The existing bridge required replacement because it was near the end of its life span and had substantial deterioration of the timber piles and approach slab cracking with undermining voids,” said Jason Bordner, FDOT project administrator. “The existing bridge was also narrow with an approximate 20-foot width and substandard traffic railing. Its capacity was reduced over the years for multi-axle trucks and had a weight limit posted at 23 tons.”

Motorists were allowed to continue using the existing bridge as long as possible, but for safety and efficiency, traffic had to be detoured for approximately five months during the more complicated phases, including subsoil excavation and existing bridge removal. During the time that motorists were allowed to come through the project, traffic on the existing bridge was high, including large vehicles such as tractor trailers that had very minimal clearance with 10-ft. (3 m) lanes. FDOT officials describe it as a very busy and quite tense situation for workers who had to be vigilant while working adjacent to the traffic.

Through traffic has been detoured to County Road 130, also known as Mud Lake Road, State Road 121, Interstate 10 and back to County Road 125, during the closure. Currently, between 4,000 to 4,800 cars travel the area per day. The traffic data included in the contract plans project traffic could increase to 7,300 cars per day by the year 2028.

FDOT hired Hal Jones Contractor Inc., Jacksonville, Fla. to replace the bridge. The existing structure, built in 1949 of steel and timber, has 10-ft wide lanes with no shoulders. The newly constructed bridge will be concrete, with two 12-ft. (3.7 m) travel lanes and two 10-ft. emergency lanes. A 3-ft. (.9 m) high solid concrete barrier will be built along the edge of the bridge based on current safety standards.

“This project has gone very smoothly,” Bordner explained. “This may be attributed to the extensive experience the prime contractor has with more complex and sizable bridge projects. Additionally, there has been great communication and a teamwork approach between FDOT, GAI Consultants Inc., J.B. Coxwell Contracting Inc. and the other subcontractors.”

Although cold, hot and windy weather can affect proper concrete curing and be a factor in scheduling delays, the project has had minimal impacts due to the extremely mild winter. Additionally, the contractor didn’t experience a busy 2011 hurricane season or high water tables and flooding due to rain.

Equipment being used on the job includes one or more Kobelco 200-ton (181 t) cranes, Kobelco 275-ton (249 t) cranes, Bidwell screed machines, Caterpillar 320 track hoes, Caterpillar motorgraders, Caterpillar front-end loaders, Caterpillar rollers, Komatsu D31 dozers, Caterpillar dozers, Caterpillar wheel-mounted hydraulic excavators, dump trucks, air compressors, generators, diesel pile driving hammers, vibratory sheet pile drivers, vibratory timber pile drivers/removers, heavy equipment hydraulic jackhammer attachments, hydraulic earth augers, metal cutting and fabrication equipment, high lift man buckets, soil mixers, asphalt pavers, backhoes, flatbed transports, logging equipment and a concrete pump truck.

Estimated quantities of materials on the job include 845 cu. yds. (646 cu m) of concrete; 157,021 lbs. (71,223 kg) of reinforcing steel, 2,441 tons (2,214 t) of rip rap rubble/bedding stone, 50,638 cu. yds. (38,715 cu m) of earthwork, 13,304 sq. yds. (11,123 sq m) of limerock base, 2,232 tons (2,024 t) of asphalt and 54,000 sq. yds. (45,150 sq m) of grassing.

Workers have been completing five-day work weeks Monday through Friday for the last seven months. Hal Jones Contracting has been using two to three crews on eight hour shifts and J. B. Coxwell Contracting has authorized one-crew, ten-hour shifts. Most of the work has been daytime work, with the exception of the concrete deck placement.

Due to the sensitivity of the surrounding environment, a work trestle (bridge) was required to be constructed to reduce wetland impacts. This allowed the cranes to access both sides of the creek in order to reduce construction costs and project duration. Hal Jones Contracting has used its own work trestle design, successfully recycling most of the components on numerous projects including the I-95 Trout River Bridge in Jacksonville as well as the Zoo Parkway Bridge project, also in Jacksonville (both required an approximately 1,500 ft. long trestle), before bringing the trestle to this project.

The specific improvements under the bridge replacement contract include pile driving, bedding stone, concrete approach/sub/prestressed/super structures, asphalt milling/resurfacing, base work, shoulder treatment, drainage improvements, riprap rubble, guardrail, clearing/grubbing/structure removal, highway signing, pavement markings and other incidental construction at the Little St. Mary’ s South Prong in Baker County. Contract time began being assessed in mid-August 2011.

Once the new bridge and roadway are reopened, there will be daytime lane closures until all the work can be finished. Approximately half the work has been completed at last report. Work began on the west side of the existing bridge with construction of a temporary work platform where the new bridge is being constructed. Crews also have started with plans to clear the right-of-way on both bridge approaches and widening the roadway to line up with the new bridge location.

The total cost to replace the bridge is $3.5 million, and will be paid for using federal funds. The new bridge is expected to be completed within the year timetable, depending on future weather concerns or other potential complications.

Added Bordner, “This project, when finished, will be a dramatic safety improvement for motorists who will have wider lanes to meet opposing traffic on the bridge, as well as for those vehicles who were weight restricted. It should be much more comfortable and reassuring for motorists, bicyclists and pedestrians with the 12-foot travel lanes and 10-foot shoulder emergency lanes.”