Evaluating CIPP Emission Data

Study concludes Phase 2 of Trenchless Technology Center’s investigation into CIPP safety concerns.

Evaluating CIPP Emission Data

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The results of a study focused on the safety of emissions resulting from the steam-cured CIPP process are in. The Trenchless Technology Center at Louisiana Tech University was tabbed by NASSCO to conduct the study, and earlier this year, it released a report sharing its findings.

As part of the study, the Trenchless Technology Center collected data at nine CIPP project sites dating back to December 2018.

“The sites reflected variety — different geographies and climates, high altitude and dry and low altitude and wet, different times of the year,” says Elizabeth Matthews, one of the members of the team heading up the study.

The pipe lengths and diameters also varied at the CIPP job sites in Shreveport, Louisiana; St. Louis; and Aurora, Colorado, where data was collected. Various emissions measurements were taken before, during and after curing at the job sites and the surrounding areas. Meteorological measurements like wind speed were also taken into account. Dispersion modeling was used to estimate compound concentrations for areas extending farther away from the job sites.

Main focus

Though it wasn’t the only chemical looked at (the study captured all 19 toxic organic airborne compounds on the U.S. Environmental Protection Agency’s TO-15 list), styrene was the only one identified with concentrations significant enough to potentially pose a health risk to workers and the surrounding community. That potential health risk was based on action-level guidelines published by the EPA, OSHA and the National Institute for Occupational Safety and Health.

However, much of the emissions testing — using both directly measured and modeled data — showed styrene amounts below those health risk thresholds. Across the various job sites, the trend that emerged was that the liner truck opening and emissions stack posed the greatest concern.

“Because of the consistency of the data, those are the areas we focused on with our safety recommendations,” says John Matthews, director of the Trenchless Technology Center.

The research team noted that the presence of a styrene odor on its own is not necessarily a sign of danger. Styrene produces a noticeable smell at levels far below the most conservative regulatory exposure limits.

In the study, no measurement taken at a distance of 10 feet or more from the termination manhole and/or the emissions stack exceeded recommended exposure limits. They were far below guidelines. Measurements taken in homes near exhaust points produced styrene concentrations less than 0.01 ppm, suggesting there is little danger of emissions collecting in homes and rising to potentially dangerous levels. Even near the insertion manhole, the highest styrene level measured was 26 ppm, enough for temporary irritation possibly but still below all published exposure guidelines.

Those relatively low levels of styrene were compared with the 100 to 200 ppm measured inside the liner trucks (none of the job sites used in the study did wet-out in the field). Levels near emissions stacks were mostly lower than the trucks, but they were still high enough to pose a potential health risk if workers’ exposure exceeded the five-minute range.

Data was also collected by sorbent tubes worn by workers or at different points on the job sites to approximate worker exposure. None of this data revealed any instances where workers exceeded the exposure limits for longer than recommended, indicating that CIPP installers generally experience safe long-term exposures to styrene.


Based on the collected data, some of the safety recommendations include:

• Active air monitoring for anyone entering the liner truck, as well as the appropriate personal protective equipment for those workers.

• A 15-foot perimeter around exhaust manholes and emissions stacks during curing. The perimeter can be entered for short amounts of time not exceeding five minutes. Beyond five minutes, the appropriate PPE should be used.

• A minimum height of 6 feet for emissions stacks to enhance the dispersion of emissions and lessen the likelihood of workers entering the perimeter from having to cross into the plume, even when wearing PPE.

“There was a lot of data collected,” Matthews says. “We feel this is a pretty comprehensive study, but there’s always an opportunity to collect more data.”

According to the research team, some areas of future study could include:

• A look at task-oriented worker exposure to emissions to identify specific tasks that could pose a potential health risk.

• Further study of the dispersion of styrene from the liner truck after it is opened to develop more definitive conclusions about dissipation time and the appropriate PPE to wear.

The full report is available on the NASSCO website, www.nassco.org. NASSCO is also providing additional safety recommendations through its CIPP Safety Workgroup and is encouraging industrywide participation. Email director@nassco.org to join. 


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