CHOCTAW COUNTY, MS

New structure alleviates access issue for large mining equipment

Neel-Schaffer was the Lead Structural Engineer and provided Construction Engineering and Inspection for an $8.1 million project to build a new grade crossing bridge along State Route 9 near Ackerman in Choctaw County, MS.

Traffic was maintained during construction of the bridge and walls by means of a temporary detour road north of the site. The bridge was completed and open to traffic on June 30, 2021.

Mississippi Lignite Mining Company (MLMC) operates the Red Coal Mining operation on the southwest side of SR 9. MLMC planned to mine on the northeast side as well but had no means to cross SR 9 with its large hauling equipment. MLMC then hired Neel-Schaffer for assistance with coordination with the Mississippi Department of Transportation and subsequent design services. MDOT contractually agreed to allow MLMC to pay for the design and construction of a grade-crossing bridge built along SR 9 with enough vertical clearance (35 feet) to allow large hauling equipment to cross beneath without disrupting traffic flow on the overhead route.

To avoid the design of bridge piers that would be subject to collision by one of the large hauling vehicles, it was decided to design a 140-foot long one-span bridge supported by 30- inch diameter pipe piles contained in vertical fills at the abutments.

The vertical fills were retained by geogrid-reinforced heavy block (Redi-Rock) wall systems. The bridge width consists of 2~12’ lanes and 2~10’ shoulders. Prestressed Florida I-beams (FIBs) 63 inches tall were used in the span, which is in a curved and tangent alignment, with slightly skewed (3 degrees) ends. The maximum heights of the retaining wall systems are 42 feet beneath the bridge and taper down at approximate 3:1 slopes outside the edges of the bridge.