Innovation in the trenches: MARMAC couplings
To bridge the gap between new reinforced concrete pipe (RCP) and older corrugated metal pipe (CMP), the county raised the question during a training session conducted by the Georgia Concrete Pipe Association. During the discussion, one instructor mentioned MARMAC couplings, manufactured by MarMac Construction Products, as a potential option. These couplings use a reinforced mastic and mechanical band system designed to seal and restrain external pipe joints.
While not originally intended for joining deteriorated CMP to new RCP, the couplings provided a practical solution when ROW and budget constraints ruled out building new junction boxes.
Challenges included:
- Deteriorated CMP is too weak to withstand strap pressure
- The need for a concrete saddle over the coupling to prevent collapse
Despite these obstacles, the couplings offered a workable link between new and old systems, ensuring continuity. Importantly, the difficulties encountered were due to site conditions — not product performance.
Lessons Learned
The Fox Hall Farms project highlights the complexities of stormwater replacement under ROW restrictions. Success required:
- Flexibility to adapt plans as conditions changed
- Innovation in using specialized products like MARMAC couplings
- Resourcefulness in balancing costs, easements, and construction methods
As one project manager reflected, “The true test of success will be time.”
For counties working under similar restrictions, Fox Hall Farms serves as both a cautionary tale and a model of innovation—demonstrating that even within tight boundaries, it is possible to stay within the lines while protecting vital infrastructure.
References
1 - National Corrugated Steel Pipe Association. CSP Durability Guide: Product Usage Guidelines for Corrugated Steel Pipe. Washington, DC: National Corrugated Steel Pipe Association, May 2000. Available from https://www.conteches.com/media/4iwpslij/tech_durabilityguide.pdf