The CSX tunnel project called for a pre-construction clearance survey of a 1,400 ft tunnel prior to the weeklong shutdown replacement of rails and ties. Utilizing the AMBERG GRP Trolley and a 3D Hi-Definition laser scanner, our crew measured the existing clearance between a 20’2”+3 rail car envelope and the top of the tunnel. Construction crews removed and replaced approximately 400 ft of rails and ties per day.

At the end of the daily construction, the completed section was re-scanned, and the new clearance distance was recorded. Data was processed immediately on site, and the resulting new clearance was reported to CSX Railroad. With assurance that the top of the rails were at original grade or lower, the tunnel was re-opened and train traffic resumed immediately. Final data indicated an additional clearance of 3” to 6” was gained, thereby giving the client additional reassurance that tunnel strikes were less likely to happen. The deliverable included tables of pre-construction clearances and daily results. A final as-built survey was performed after all work in and at the approaches to the tunnel was completed.