Neel-Schaffer provided preliminary engineering design and construction engineering and inspection services for the $8.9-million project to build a bridge and retaining walls on State Route 9 in Choctaw County, Mississippi. The project has allowed Mississippi Lignite Mining Company (MLMC) to expand its Red Hills Mine operation to the east side of SR 9.
MLMC desired to expand its operations to the east side of SR 9 but had no means to safely cross the roadway with its large mining and hauling equipment. MLMC hired Neel-Schaffer, which came up with a solution. Instead of going over SR 9 or crossing at grade, the mine now drives its equipment under the new SR 9 bridge. Neel-Schaffer worked with the Mississippi Department of Transportation (MDOT), and MDOT contractually agreed to allow MLMC to pay for the design and construction of a grade-crossing bridge along SR 9 with enough vertical clearance (35 feet) to allow specialized mining equipment to pass underneath without disrupting traffic flow overhead.
Engineers are accustomed to designing bridges that cross over rivers or streams or other existing obstacles, but this was a first: Neel-Schaffer engineers designed a bridge to span over a future roadway needed for the expansion of the mining operation. Another important aspect of the project was that MDOT required SR 9 to stay open to traffic at all times. To do that, Neel-Schaffer designed a 3,000-yard temporary road that ran east of the existing road, on MLMC property.
After the temporary road was completed and traffic was transferred to it, an opening more than 40 feet deep and more than 140 feet wide was cut out of the existing embankment, creating a corridor for a new mining road that MLMC has built. The new grade-crossing bridge was built across that corridor. It is a 140-foot-long, single-span bridge supported by 30-inch diameter pipe piles. The bridge is 44 feet wide, with two 12-foot travel lanes and two 10-foot shoulders.
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The bridge abutments and vertical fills are protected by two large geogrid reinforced retaining walls that were constructed using more than 3,000 28-inch Redi-Rock blocks. Each wall is 300 feet long. Each reaches a maximum height of 42 feet tall below the bridge, then tapers downward to the outside edges. Nearly 500,000 cubic yards of fill material was excavated during the project, with much of it re-purposed. No fill dirt was brought from off-site for the project.
Neel-Schaffer began preliminary work with MLMC on the project in 2015. Construction began in 2020 and the project was completed on schedule, on June 30, 2021. The project also came in nearly $720,000 under budget.
“This project is a great example of what can be accomplished through cooperation of multiple parties,” said Keith Purvis, PE, Manager of Neel-Schaffer’s Mississippi Transportation division. “Mississippi Lignite Mining, MDOT, and Neel-Schaffer were committed to a successful project. Because of effective and continual communication from the initiation of the project through the completion of construction, that mission was accomplished.”
