$200M Bridge to Span Mighty Mississippi

Residents of both Mississippi and Arkansas are witnessing a new structure slowly stretching over the Mississippi River. The new Greenville Bridge, which has an estimated total cost of more than $200 million, will connect Greenville, MS, with Lake Village, AR. &#8220;This is the largest single bridge project [in Mississippi]. There have been projects that were as large monetarily, but they included several large bridges as well as road work,&#8221; said Mississippi Bridge Engineer Mitchell Carr. The Mississippi Department of Transportation (MDOT) is working with the Arkansas State Highway and Transportation Department (ARDOT) on the project, which won&#8217;t be completed until 2006. Carr said both states are sharing equally in the cost and noted that the partnership between Arkansas and Mississippi isn&#8217;t unusual. &#8220;MDOT commonly partners with our sister states on border projects,&#8221; he said. Located approximately .5 mi. downstream from the Benjamin G. Humphreys Bridge, the new cable-stayed bridge will have a main span of 1,378 ft. (420 m) and be the longest cable-stayed bridge in the United States. While the existing bridge is structurally sound, it is considered functionally obsolete for many reasons. These include the fact that the total width of the roadway for the old bridge is 24 ft. (7.3 m) as compared to 80 ft. (24.3 m) for the new bridge. The old bridge will be demolished once the new bridge is open. The new bridge&#8217;s location also is expected to decrease the possibility of barge collisions. Over the past 30 years, the existing bridge has sustained more barge impacts than any bridge over the Mississippi River. In June, 2001, the Mississippi Transportation Commission awarded the contract for construction of the main cable-stayed span to Massman Construction Co., of Kansas City, MO, and Traylor Brothers Inc., AJV, Evansville, IN, with the low bid of $110 million. The current contract consists of both the substructure and superstructure portions of the main span. The substructure is made up of two main river piers, founded on dredged caissons that extend 120 ft. (36.6 m) below the river bottom and support the main towers that soar approximately 425 ft. (129 m) above the river bottom. Each of the two end piers rest on 15 drilled shafts 6 ft. (1.8 m) in diameter. The typical water depth during the working season is expected to be between 60 to 80 ft. (18.3 to 24.4 m). Massman built the substructure of the original bridge, which also was founded on caissons. The superstructure is a cable-stayed design that resembles the Dame Point Bridge in Jacksonville, FL, although design and construction methods are different. The main span portion of the bridge will include four deep river piers anchored 120 ft. (36.6 m) into the riverbed, two concrete towers soaring 425 ft. (129.5 m) above the Mississippi River, a cable stayed span supported by four fans of pre-stressing strand steel cable with a center span 1,378 ft. (420 m) long. Carr said heavy equipment currently at the site includes Manitowoc 999, 4100 and 3900 cranes. The project has not been without obstacles. &#8220;To date, the challenge has been founding the two main river caisson foundations. Although accounted for by the contractor, the spring rise of the Mississippi River and the swift current that comes with it makes the spring and early summer a very interesting time for working in the river,&#8221; said Carr. &#8220;A stipulation of the contract allows the contractor to suspend work each day the Mississippi River elevation, as measured on the Corps of Engineers Greenville Gage, exceeds 121.4 feet,&#8221; he added. &#8220;The current is some of the swiftest on the whole Mississippi River, with a velocity of 13 to 15 feet per second.&#8221; Carr said the heavy rain that occurs in the northern region of the Mississippi River basin may affect the project if it causes the river&#8217;s elevation to rise above an elevation of 121.4 feet. &#8220;Local rains have little effect on the project,&#8221; he said. Between 60 to 100 workers are working at the site depending on the phase of construction. The workers work six days a week, 10 hours a day, said Carr. Future projects will provide for construction of the roadway and bridge approaches on either side of the river as well as for removal of the existing bridge. Funds for the bridge were made available from both federal and governments. U.S. 82 is a major part of the Mississippi Delta&#8217;s transportation network and is designated as part of the National Highway System. U.S. 82 connects the Mississippi Delta to I-55 and other four-lane highways like U.S. 61 and U.S. 65 in Arkansas. During the Nov. 2, 2001, ground-breaking, Central District Transportation Commissioner Dick Hall said, &#8220;Over 60 years ago, more than 5,000 citizens of Greenville, MS, and Lake Village, AR, gathered to dedicate the new U.S. Highway 82, Benjamin G. Humphreys Bridge.&#8221; He noted that the bridge was &#8220;a giant in its time&#8221; and boasted one of the largest spans across the Mississippi River. &#8220;The new bridge will share the same honor,&#8221; he said. &#8220;MDOT decided early in the design of the project to include a Web site. This is a very interesting project for both the engineering community and the general public,&#8221; said Carr. &#8220;There are many links on the site that provide educational and historical information. There is also a Web cam that a user can control to look at construction of both the old bridge and the construction of the new bridge. The Web site provides a unique opportunity for us to showcase the project and promote interest in engineering in general.&#8221; For more information visit www.greenvillebridge.com.