In early October 2015, record rainfalls were recorded throughout South Carolina. Runoff from these storms resulted in multiple dam breaches and numerous bridge and culvert failures, precipitating catastrophic flooding throughout the central and eastern part of the state.

SEPI was contracted to assist in providing flood study services and a hydraulic structure recommendation for the emergency replacement of the Norfolk Southern Railroad (NSR) crossing over Mill Creek in Hopkins, Richland County, just southeast of Columbia, SC.

As a result of the flooding, an existing 12-foot brick masonry arch culvert failed. The culvert was estimated by NSR personnel to be over 100 years old and under 30 feet of fill. The rail line carried by this crossing is part of a network of rails that connects Columbia and the Midlands to a major port terminal at Charleston.

In order to restore service to the railroad as quickly as possible, NSR completed an emergency repair with multiple lines of readily available high density polyethylene pipe (HDPE).

Mill Creek is in an area designated by the Federal Emergency Management Agency (FEMA) as Zone AE with Floodway. Multiple residences upstream of the crossing are subject to flooding. The final recommended replacement structure must achieve a “no-rise” condition, or no increase to the 100-year “base flood” water surface elevations, when compared to the original (pre-washout) condition.

SEPI completed hydraulic survey, field reconnaissance, and preliminary structure layout of a 14’-6” structural tunnel liner plate culvert. Additional tasks included hydraulic modeling, final structure recommendation to NSR, and completion of a “no-rise” package for submittal and review by Richland County.