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Rising water levels at Clinch River and Big Sycamore Creek in east Tennessee make bridge work virtually impossible for most of the year. The contractor patiently waits for water levels to drop while working on other phases of the project.
Planning is important on every job, especially on a bridge contract where the water level is too high for construction eight months a year.
Tom Caudel, project manager for Elmo Greer & Sons of London, Ky., said that high water has significantly impacted construction of a pair of bridges the company is building on U.S. Hwy. 25E in east Tennessee.
The bridges cross the Clinch River and the Norris Lake backwaters at Big Sycamore Creek.
Norris Lake dams up the Clinch and Powell rivers for both hydroelectric power generation and downstream flood control. Lake levels vary by about 23 ft. each year.
"We're not able to work in particular areas, at the river and the lake, from mid-April to about mid-December," Caudel said. "From mid-April to about mid-July we can't get into the center piers on the river."
The contractor has remedied the problem by working on other phases of the project during times of high water, then "we come back in when the water goes back down."
The bridges are part of a $31.4 million contract that also includes expanding the highway from two to four lanes over a 7-mi. stretch in Grainger and Claiborne counties. Work started in June 2004 and is scheduled for completion in December 2008.
The existing narrow, two-lane bridges will remain in use until the new four-lane spans are open, Caudel said. Two new highway lanes will be built, then traffic will be diverted onto them while the other two lanes are under construction.
Keeping traffic moving is important because U.S. 25E is the primary road between Newport, Tenn., and Corbin, Ky., and handles much of the Kentucky traffic headed to upper east Tennessee. Average daily traffic is more than 9,500 vehicles and 20 percent of that is 18-wheel trucks, said Chris Jenkins, project manager for the Tennessee Department of Transportation.
The Clinch River bridge is about twice the size of the Big Sycamore bridge.
At 618 ft. long, the Clinch crossing will have nine rows of precast bulb-tee girders on each of its six spans, Caudel said. The girders, manufactured by Ross Prestressed Concrete of Knoxville, vary in length - the longest is 105 ft. - and will stretch to 5,455 ft. They have 42-in. flanges on top where the 87-ft.-wide deck will be poured.
The bulb-tees are TDOT's choice "because they typically have a longer span," Jenkins said. "You can use those and have fewer piers. We're trying to minimize the impact to the lake area and river so we want to make the span as long as we can."
Caudel said everything necessary is being done to prevent erosion and pollution of the creek.
"That includes installing silt fences, berms and other needed structures," he added.
He said his crews will use at least two cranes to place the girders, in what he calls "a coordinated lift...men guiding it on the deck and pier. We don't have deep enough water for a barge and if you don't have to use a barge you're better off."
The deck and supports will require nearly 3,000 cu. yds. of concrete, 288,000 lbs. of reinforcing steel and 524,000 lbs. of epoxy-coated steel for the bridge deck.
Pilings at the south end are driven until they hit rock at about 30 ft. deep. The river depth ranges from 4 to 5 ft. to 20 to 22 ft., and the bridge is about 25 ft. high.
The Big Sycamore bridge is 290 ft. long and 87 ft. wide and rests on abutments about 50 ft. deep. A total of 2,558 ft. of bulb-tee beams will go into this bridge, along with more than 1,500 cu. yds. of concrete for the deck and supports, 119,000 lbs. of reinforcing steel and 191,000 lbs. of epoxy-coated steel for the bridge deck.
The bridge decks will be 10 in. thick.
The project also includes three box bridges, one 10 by 8 by 369 ft. with 1,198 cu. yds. of concrete; one 16 by 12 by 90 ft. with 291 cu. yds. of concrete ; and one 10 by 8 by 506 ft. with 672 cu. yds of concrete.
Cloud #9 Enterprises of Mooresburg, Tenn., is supplying concrete for the job from its plant 12 mi. from the site. About 12-15 trucks a day will deliver concrete to the site during the bridge pours.
Cloud #9 owner Dale Moles plans to bring in a large pump to place the concrete.
"The pumps we have nowadays, you can pump as fast as a truck can unload," Moles said. "When one is unloading, the next is sitting next to it ready to go. You can stay busy with a 4-in. pump."
The highway widening requires at least 2.3 million cu. yds. of excavation - about 60 percent to 75 percent of which is rock, Caudel said. Most of the excavated material is being transported to the New Tazewell Municipal Airport about 5 mi. up the road.
A rock slide recently stopped work in one section of the jobsite.
"They (TDOT engineers) had designed the slope steeper than what could stand up," TDOT's Jenkins said. The area goes through shale that, in its formation, is sloped in layers that slant toward the road.
"When water gets in there, it expands and causes layers to separate, and that causes slides," Jenkins added. The redesign will require an additional 500,000 cu. yds. of excavation.
Jenkins said probable solutions include cutting a "bench" in the hillside that would catch falling rock or installing chain-link netting to hold the rock against the hill.
The methods have been used on two other sites in the area, he added.
"We hope to salvage some of the stone for crushed stone, but it's too early in the job to know if we can," Caudel said. The highway bed will have 10 in. of stone topped by 7 in. of asphalt.
Drains for the project will run more than 2,300 yds. in concrete pipe from 17 in. to 53 in. diameter. Side drains, to run about 670 yds., are 17- to 47-in. pipe.
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