• Span: 30-ft.
• Length: 200 ft.
The 350-acre West Plains Mining's (WPM) Kentner Creek operation is located outside of Wabash, Indiana near Richvalley and mines Silurian-age limestone in a unique geological formation featuring predominately non-reefal rock. The stone quarry extends 218' in depth with both open pit and underground mining, and its latest expansion in 2019 included the addition of a rail system looping through the west property.
Wabash County has one of the highest concentrations of ocean reefs in North America, and since the Kentner Creek Mine was protected from storms and/or drastic climate events, the result is a chemically unique, high calcium and physically superior product. Most limestone quarries in northern Indiana mine ancient coral reefs, but this operation mines limestone through three massive layers, each with different qualities and chemical makeups.
In 2019, WPM executed an expansion project which included a double-loop rail system that tied into the Norfolk Southern Railroad (NSR) system servicing east and west destinations. As part of the new track layout, a tunnel under old US-24 was needed to allow connection to NSR's system east of the mining property. A significant amount of coordination was needed between WPM, Pathfinder Engineering and the Wabash County Road Department to limit the local impact of the heavily-traveled roadway.
The WPM team coordinated with Contech Engineered Solutions to create the tunnel portion of the project. After reviewing options such as a precast arch system, an at-grade truss and a plate structure, as well as the corresponding costs for each option, it was determined that a 30' round BridgeCor® Structural Plate, 200' in length, was the best solution for the tunnel. The 15” x 5.5” advanced profile allows designers to convert traditional bridges into more economical buried bridges by clear spanning up to 65'. This corrugation is widely accepted by AASHTO and the international engineering community.
A BridgeCor structure was selected for its ability to meet the project demands, including NSR's 18' wide x 23' tall clearance area for rail and safety and a proposed 50' vertical dimension between the final rail height and the current roadway height resulting in 25' of cover. Additionally, it was imperative that the structure was able to be installed despite the existing three-span bridge situated less than 80' from the proposed tunnel.
Beginning in January 2020, the tunnel channel was blasted and aggregate was removed. In mid-February, construction began on the tunnel. The structure was assembled on-site within the 45' blasted limestone trench in two phases over the course of six weeks with the assembly of each phase taking approximately one week to complete. The benefit of working within a mining operation was that select backfill material was readily available on-site, and it was made specifically to the requirements of the tunnel and wall system. The challenge, however, was completing the backfill within the confines of the 45' channel and the 30' wide tunnel system. At times, the team had only about 8' of area to backfill and compact around the structure.
In addition to the tunnel, Contech coordinated with Reinforced Earth Company Wall Systems to design and provide a precast MSE wall end treatment for the tunnel. The precast wall included over 3000 sq ft of wall surface with the west wall at 70' wide x 43' tall and the east wall at 80' wide x 32' tall. Custom panels were designed to follow the round shape of the BridgeCor tunnel, and the teams coordinated on a closure design between the tunnel and the blown limestone wall system. Each precast wall panel included a series of galvanized steel reinforcing strips that extended up to 30' behind the wall.
The project was completed in June and old US-24 was reopened to traffic.
“There was a lot of coordination required between Pathfinder, the West Plains team, Wabash County, their review engineer, Norfolk Southern, Balkema and Contech on such a complex project," concluded Robert Goodheart, President/Engineer with Pathfinder Engineering. "The Contech team assisted from every aspect of the project including concept design, to product selection, to structure and wall engineering, and even field support during installation. It was a true team effort to allow West Plains Mining to expand and grow their business.”
• Span: 30-ft.
• Length: 200 ft.