Gibson County Coal, LLC (GCC) produces upwards of 3.5 million tons of clean coal annually. With a daily volume of nearly 16,000 clean tons per day, the company used up to 700 trucks a day to transport the coal to two nearby railways, crossing the heavily traveled US 41 in the process. Worse, the busy crossing was located atop a steep hill, and the tall trucks obstructed the view of traffic lights for other drivers, causing safety concerns. So the company began to look at better ways to transport the coal.
After evaluating alternatives, which included an overhead conveyance system and a tunnel, GCC opted for an approach that involved an open-cut across the highway to allow for installation of a precast-concrete box culvert with conveyor system. Working with a local concrete precaster, Lochmueller Group(Lochgroup) engineers determined that a 376 long, precast-concrete box culvert with an 11-foot span and 6.5-foot rise of would be required. This would allow a man of average height with a safety helmet sufficient room to access and maintain the conveyor system throughout the box culvert.
Not surprisingly, the Indiana Department of Transportation (INDOT) had serious concerns about closing a major 4-lane highway. So Lochgroup proposed avoiding total closure of the highway by diverting traffic across the median using temporary cross-over lanes into two single-file lanes. This allowed half of the roadway to be closed while half of the culvert was installed, then switched over to the other half. INDOT agreed to issue a construction permit to allow this activity given the very aggressive, fast-track schedule for construction proposed.
Due to varying cover and loading conditions, the precast box culvert was designed, constructed, and installed in two different strengths. This equated to 29 pieces requiring a heavier loading condition and 18 pieces with a lesser loading condition, for a total of 47 pieces. Each precast box culvert section was 8 feet in length, with 12-inch-thick walls, and weighed approximately 43,500 pounds. To meet the aggressive schedule required for installation, each section was constructed and labeled according to specifications to be delivered to the job site at the appropriate sequence and time.
The contractor working with Lochgroup construction engineers installed all 47 sections of the precast box culvert in only 5 working days. Construction in the US 41 right-of-way required only 7 weeks, including weather delays.
This innovative approach to using and installing precast box culverts provided all parties with several long-term benefits. GCC has the benefit of along-lasting, aesthetically-pleasing alternative for conveying their coal across a major highway for years to come, while minimizing future transportation expenses. Benefits to INDOT and the surrounding community include an estimated reduction of up to 75–80% of the daily truck traffic entering and exiting the highway, resulting in improved safety of the highway and access to the intersection.