08 May 2007
08 May 2007
Graettinger, Iowa, made the decision to reline old clay sewers with new cured-in-place pipe (CIPP) to prevent storm and ground water entering the wastewater system.
During periods of wet weather, the water table rose above the level of the sewer pipe system which was leaking at its joints. The result sent extra water through a wastewater system that was designed to collect, pump and treat much lower volumes.
The solution was a new CIPP liner installed by Visu-Sewer Clean and Seal using Vipel isophthalic polyester from AOC. With the new liner sealing old leaks, infiltration and inflow during rainy periods is reduced by up to a half million gallons (1.9 million litres) per day.
“I didn’t believe the numbers at first,” said Graettinger Utility Superintendent Paul Kroenke. “I kept checking and re-checking, but the results kept coming up great.” The substantial infiltration and inflow reduction allows Graettinger’s wastewater holding lagoons to operate within their designed capacity. Keeping the lagoons within capacity keeps DNR from designating Graettinger’s sewer system as “continuous discharge.” Having that status would have significantly increased the cost of monitoring and reporting.
The improved Graettinger system was designed by the engineering firm DeWild Grant Reckert & Associates Co. (DGR), Rock Rapids, IA. DGR ruled out replacing the old sewers, especially the line buried 20 feet (6 meters) deep in sandy soil under the Main Street business district.
Visu-Sewer uses National Liner CIPP technology licensed from National EnviroTech Group. This technology saturates a non-woven polyester felt liner with a corrosion-resistant thermoset resin, then inverts the liner (turns it inside out) through the pipe in need of repair. The resin for the Graettinger project was a Vipel® isophthalic polyester manufactured by AOC and purchased through distributor CIPPCON, Ponte Vedra Beach, FL. The resin is engineered to provide ease of formulation, predictable handling and user-friendly wetting characteristics. The felt liners for Graettinger were wet-out at the Visu-Sewer facility then shipped to the job site under environmentally-controlled conditions to prevent premature curing.
To speed installation and minimize disruption, access to the host pipe was accomplished through existing manholes. Water was pumped inside the liner to create pressure that moved the liner forward and against the inner wall of the host pipe. After the entire length of an individual inversion was complete, the water was heated to initiate the reaction that turned the liquid resin into a thermoset solid. The end-result is a new seamless liner that stops the leaking at the faulty joints.
After the liner was installed, the Visu-Sewer crew used a remote-controlled pneumatic cutter to open access to laterals. Connections at the laterals were then reinstated and grouted in place with AV-100 gel grout to form a water-tight seal at the lateral connection.