No-Dig Winners

Mitigation of Styrene Emissions from Steam-Cured CIPP Projects

The safety of CIPP due to styrene emissions has been called into question by various researchers, causing hesitancy of many engineers to specify CIPP. This has specifically impacted steam-cured CIPP, which is the most widely used for sewer mains up to 12-inches and also the largest segment of the sewer rehabilitation market in North America. Much of the research causing the concerns was based on questionable scientific methods, so in 2019 the Trenchless Technology Center (TTC) began to investigate the issue, initially with support NASSCO, and subsequently on its own internally. As part of its initial study, the TTC investigated the impact of styrene emissions from nine different sites across the U.S.

The focus of the study was on emissions being released from the exhaust ends of the liner. However, other locations were also monitored. The key findings showed that although there was styrene being emitted, it was not in the concentrations that were reported by the questionable studies. This study resulted in a set of safe working recommendations that include maintaining a perimeter around the exhaust stacks of at least 15 feet during liner curing. The TTC also examined the emissions in and around the cold storage vehicles that bring the liners to the sites.

The general findings found the most common class of coating materials, primarily PEs, PPs, and PUs, regardless of thickness do allow styrene breakthrough after a few days on average resulting in evaluated styrene concentrations in storage trucks. The TTC made additional recommendations to make this environment safer. The TTC has also developed a patent-pending styrene mitigation device that can be used to further reduce the potential impact of emissions from the stacks. This technology uses heat to catalytically burn off the styrene on its way to the stack. Testing has shown the reduction in styrene emissions to be greater than 90%, which would eliminate the need for the stack perimeter.

Download the article on Trenchless Works December 2022 to see more details.