In addition to being home to 5,000 people, thousands more drive through the Town of New Ipswich, N.H., every year on their way to popular New England hiking trails.
In late 2015, the Department of Public Works (DPW) found corrosion in many of the town’s culvert pipes. Two in particular, each 6 feet in diameter and running side by side for 40 feet under a main thoroughfare, threatened to become a safety hazard by deteriorating further.
As with any public agency, cost was a factor in determining a viable solution.
Because the culverts run under a paved road, the department preferred rehabilitation over open cut and replacement. The expense of concrete-pouring equipment as well as limited pipe access ruled out concrete. Concrete also required a permit, a time-consuming process that would have set the project back further. Finally, ease of installation was important to the two-person public works crew.
A small grant from the state DOT would pay to repair one culvert pipe using traditional rehabilitation methods. However, the town’s consulting firm recommended a solution that would repair both within budget.
ACF Environmental of Richmond, Va., recommended a geosynthetic cementitious composite mat (GCCM) made by Milliken Infrastructure Solutions LLC of Spartanburg, S.C.
The fabric comes in rolls, is wet with water, and applied. In addition to giving ditches, slopes, culverts, and other contoured assets a new surface, the product mitigates backfill loss around pipes by covering perforations in pipe inverts.
The product also met requirements of the New Hampshire Department of Environmental Services (NHDES), which approved the solution one week after the project engineer submitted the initial concept.
“New England’s environmental permitting agencies can sometimes conduct complex and lengthy evaluation and approval processes for new technologies,” says ACF Environmental New England Regional Sales Manager Rick Fotino. “We were surprised by how quickly the product was determined to be an environmentally responsible, low-impact solution, especially compared to other rehabilitation options.”
Installation began in July 2016 and was as easy as permitting had been. Summer is better for such rehabilitation work than other months, when water levels in the culvert pipes regularly rise to 2 feet. However, even with little water in the pipe, flow needed to be diverted to one culvert before laying down the GCCM in the other.
Once the first pipe was ready, the GCCM was lowered into the culvert, where the public works crew rolled it out and used mechanical fasteners to attach it to the existing pipe. Flow was then directed to the second pipe and the process repeated. That phase of the project took about three hours for each culvert; the rest of the two-day job was focused on re-diverting flows.
“We anticipate many situations in this region where the product will help failing infrastructure handle high volumes of stormwater,” says Fotino. “The material’s durability and abrasion resistance compares favorably to typical poured concrete with wire reinforcing. And with fewer associated costs, municipalities can stretch their dollars further.”