The 70-year-old Benjamin G. Humphreys Mississippi River Bridge remains structurally sound, but it is coming down.
It’s known for sustaining more barge collisions than any other bridge on the Mississippi River, according to the Mississippi Department of Transportation (MDOT). It even took a hit in 1951 when a jet pilot from nearby Greenville Air Force Base crashed into it while attempting to fly under it. The aircraft was a total loss, the pilot was fatally injured, and the bridge suffered $175,000 in damage.
Nevertheless, the 70-year old Benjamin G. Humphreys Mississippi River Bridge remains structurally sound. It may not be structurally deficient, but it is coming down.
Crash Course in History
Talk of bridge construction for a river crossing at Greenville started in the 1930s. However, the Mississippi River changed paths several times before being tamed by the U.S. Army Corps of Engineering. One change in the 1930s left the once riverside Greenville about 7 mi. from the banks of the Mississippi. After that occurred, the City of Natchez started working on a new river bridge.
By 1936, a group called the Arkansas-Mississippi-Alabama U.S. 82 Association had formed to raise funds for a bridge. The following year, Mayor Milton C. Smith worked with John A. Fox, the secretary of the Washington County Chamber of Commerce, to get Congress to pass a law authorizing the bridge. President Franklin D. Roosevelt signed the bill authorizing the bridge into law in August that year. In 1938, Smith applied for money from the Works Progress Administration (WPA) to fund the estimated $4.5 million needed to build the bridge. The WPA agreed to the proposal in September 1938, and construction started a few months later. On Oct. 4, 1940, the bridge officially opened to traffic
Constructed of riveted steel with a concrete deck, the 1.9-mi.(3 km) -long, 24-ft. (7.3 m) -wide two-lane cantilever bridge named for Benjamin G. Humphreys II, a former United States Congressman from Greenville who was regarded as the father of flood control in the delta region, carries U.S. 82 and U.S. 278 across the Mississippi River between Lake Village, Ark., and Greenville, Miss.
Soon after it opened, the bridge was discovered to be a “navigation hazard.”
It’s in a “bad position in a bend of the river,” Robert Pode, project manager of Granite Construction Company, explained. “It’s the most frequently struck bridge on the river.”
Riverboat operators have to round a sharp bend, then aim for one of the bridge piers, with a swift cross-current pushing the head of the barge tow away from the pier at the last second. It’s a difficult maneuver that only highly experienced river pilots can accomplish.
An unusual design feature of the bridge is the extended arms on the upriver side that carry electrical and communications lines across the river. Typically, those lines are buried in trenches in the riverbed, but due to the fast current, the lines were repeatedly uncovered and snagged by anchor lines. The revenue from leasing space for these utilities allowed the toll to be removed from the bridge in 1950.
The lamentably placed bridge also has the distinction of having both ends in Arkansas. While the Mississippi River is the commonly accepted state line, the official line lies on the east bank due to the river shifting slightly westward. Because of this, the main span of the bridge is located entirely in Arkansas, with only the eastern piers of the approach road positioned in Mississippi. It’s the only river bridge over the lower Mississippi River where the state line boundary does not follow the current main river channel.
Construction Prior to Demo
The Humphreys Bridge has posed a safety concern since its construction, so, at long last, it’s coming down – but not before its replacement is open to traffic.
The new Greenville Bridge is a cable-stayed continuous steel truss bridge that connects to U.S. 82 at a different point than its predecessor, 3/8 of a mile downstream at a less curved area of the river, Pode indicated. That should alleviate hazardous navigation for barge traffic as well as vehicles crossing the bridge. The $250 million bridge’s design, location and span are intended to allow easier navigation for boats and safer driving for vehicles, with four 12-ft. (3.6 m) lanes, 12-ft. outside shoulders and 8-ft. (2.4 m) inside shoulders.
The main span’s 1,378-ft. (420 m) length makes it the third-longest cable-stayed span in the United States and fourth longest in North America. The 2.5 mi. (4 km) bridge deck sits atop two 425-ft. (129 m) concrete towers above water and concrete piers anchored 120 ft. (36.5 m) into the riverbed.
“It is a spectacular crossing over one of America’s most storied rivers,” MDOT said.
HNTB Corp., Kansas City, Mo., designer and consulting engineer of the the Humphreys Bridge, filled the same role for the new bridge. Massman Construction Co. and Traylor Bros. Inc. were awarded the $110 million contract in July 2001 for construction of the Greenville Bridge with a Notice to Proceed on Aug. 9, 2001. The construction on the main span of the bridge was completed on April 21, 2006.
Austin Bridge and Road was awarded a $65 million contract to build Arkansas’ 4,657 ft. (1,419 m) of approach bridge and 3,225 ft. (982 m) of connecting roadway, which was completed in Aug. 2009. Jensen Construction was awarded a $85.9 million contract to work on the road deck of the Mississippi approaches to the bridge, which were completed in 2008.
Granite was awarded the fourth contract for $22 million to apply a latex modified concrete overlay on the surface of the new bridge, stripe the lanes, put up the appropriate road signs and tie in the end of the bridge to existing U.S. 82 before beginning demolition of the old bridge. The 2 in. -thick (5 cm) latex overlay is designed to protect the precast panels and provide a stable riding surface for years to come, Pode explained.
“It’s strong yet flexible.”
An on-site stockpile of sand, aggregate, latex and cement necessary to make the overlay will be used by American Contracting, based in Indianapolis. The Indianapolis firm also is providing trailer-mounted volumetric mixers to perform the work, which will be performed at night due to temperature constraints.
“It’s better for curing and the bridge moves less at night. It expands and contracts in the day. In addition, there is less evaporation at night,” Pode stated.
Pode said work started in April 2010 and that completion of Phase 1 (opening the new bridge) was in July 2010. That marks the first milestone; the second is completion of demolition of the Humphreys Bridge.
A total of 330 days have been allocated for the second milestone, Pode said. Systematic demolition began when the new bridge opened to traffic.
There are three reinforced truss spans over the river, two of which are 840 ft. (256 m) and the other is 640 ft. (195 m).
Crews will begin with the center truss, mechanically lowering the center span using strand jacks mounted on top of the bridge. The remaining steel will be lowered in a similar fashion.
“The hydraulic strand jacks will allow us to lower sections onto a barge to be moved on for recycling,” Pode told the Delta Democrat Times. Local mills able to recycle concrete and steel have been sought.
Crews will then saw-cut the concrete deck slabs and remove them for recycling onsite.
“There’s no native rock in the delta,” Pode pointed out, “so we’ll use it as a road base. That’s a typical use for it here.”
Portions of the U.S. Highway 82 approaches will also be removed and the materials recycled.
“Some of the approach road material will be reused. And parts of 82 will stay in place. Harlow’s will have a loop off of Highway 454 that will cross 82 connecting to their property. And 82 on the Arkansas side will provide access to Farmer’s Grain and the road to the Chicot County State Park,” Pode told the times.
The underwater concrete piers will be removed to elevation 60 (40 ft. under water), Pode continued. That depth is deemed safe for river traffic to pass unobstructed. At that depth, he elaborated, “they don’t present a hazard to any ship or vessel coming through the channel.” Pode added that the levees would be restored to a higher elevation as well.
In order to complete the demolition, Pode said Granite will use Manitowoc 888 series barge-mounted cranes and a 9310 ring mount crane. “We’ll have several 888 and 4100 cranes, some 8100 breakers and Cat 330 and 345 excavators with processing attachments. We may rent additional processors and track loaders if we need to; the rest [of the equipment] is ours.”
At peak, Granite will have 40 employees on-site, both staff and local hires. Granite, based in Watsonville, Calif., is a national company with regional offices in California, Arizona, Florida, Texas and New York. “We work all over the country,” Pode stated. In business since 1922, Granite provides civil construction services and materials and owns and operates local facilities that produce aggregates, sands, asphalt concrete and other construction material.
Removing trusses doesn’t intimidate Pode, but he expresses guarded concern about removal of the piers.
“High water is a risk,” he said simply. “Our biggest challenge is flood waters.
“The problem with this particular bridge will be trying to get the work done at the right water level. A good portion of this bridge is inside the levee in the wetlands, [so] we’re going to need a little help from Mother Nature.”
In the case of bad weather, he said crews will “wait it out.” More worrisome than meeting schedule deadlines, though, is making sure equipment is secure in the face of flooding.
“We need space for the equipment. We have to be ready to remove everything from the flood plain and we have to have moorings for the barges to ride it out.”
Pode said the river was already high in May, due to common spring flooding, although it wasn’t of significant proportions to cause any problems. There’s ample reason for concern, however: the contract contains penalties of $10,000/day for Milestone 2, with an additional $1,400/day after Sept 21, 2012.
Although construction of the old bridge cost $4.5 million, demolition will cost $22 million. The project is federally funded, but not by stimulus money.
Although Greenville has a relatively small population of 38,000, Pode said this project serves a greater need.
“There are only three crossings on the Mississippi River between Mississippi and Arkansas: Vicksburg, Greenville and Tunica. It’s important for commerce.”
In 2002 the daily traffic count was 7,200, much of which, Pode speculated, is truck travel. The new bridge, which facilitates the new 82 bypass around Greenville solves two problems, he said: eliminating truck travel through town and ending difficult water passages on the river. CEG