Headwall Scour Protection

Project Overview

A Corrugated Metal Pipe (CMP) roughly 72 inches wide by about 42 inches tall had rusted through the invert in some sections. The cost to excavate the soil overburden then remove and replace the culvert was very high. In addition, there were numerous utilities in the area that would make excavation for total replacement quite difficult. The replacement option would have required closing the road for a minimum of several weeks at an estimated cost of at least $60,000. TheCombat Concrete GCCM solution, including installation costs, would be less than a tenth that cost. The city explained, “Combat Concrete adds great value to us because our own forces can install the material in a quick and cost effective manner, which we feel is a long-term solution.”


Combat Concrete GCCM was chosen to line the invert of this culvert, providing protection and extending the useful life of this culvert for years to come. By using the CC solution the roadway could remain open, and the installation could be performed quickly at a fraction of the cost for excavation, removal and replacement or relining.

The plan for the project required Combat Concrete material to be laid parallel to the direction of flow and overlapped near the center line of the pipe. At both the inlet and outlet, CC was to be laid in a trench to prevent water from flowing under the pipe. This would protect about a third of the interior of the pipe. Each piece would then be overlapped approximately four inches, then the sides fastened to the CMP using galvanized self-tapping screws.

On the first day of the installation, the city closed down traffic on this residential street. Combat Concrete GCCM material was unrolled and laid into hand dug trenches at both the inlet and the outlet. Because water was continually running through the culvert, the City used this water to hydrate the CC GCCM after securing the product to the CMP with screws. Installation was completed by 11 am that day.

On the second day, the free edge of the cured Combat Concrete GCCM was sealed with mastic to limit future high water infiltration between the GCCM materials and the pipe.

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