TTC Phase 3 of Steam-Cured CIPP Study

TTC Completes Phase 3 of Steam-Cured CIPP Study

The Trenchless Technology Center (TTC) at Louisiana Tech University has released the NASSCO CIPP Emissions Phase 3 “Evaluation of Styrene Emissions Associated with Various CIPP Coatings in Refrigerated Storage” Final Report.

Published reports in recent years have questioned the safety of emissions from the cured-in-place pipe (CIPP) process when using styrenated resin. In response, NASSCO spearheaded a three-phase emission study, to ensure workers and communities stay healthy by understanding these claims through the funding of comprehensive, third-party, objective research.

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Phase 1 of the NASSCO emission study was completed in the spring of 2018 by a team of researchers led by the Center for Underground Infrastructure Research and Education (CUIRE) at the University of Texas at Arlington. Phase 1 of the project focused on reviewing CIPP emission study literature and found that of the 21 papers reviewed, previous studies have “defective methodologies” that do not evaluate CIPP emissions (Najafi et al., 2018). The CUIRE team then developed a scope of work for capturing and analyzing CIPP emissions data (Najafi et al., 2018).

Phase 2 of the project was awarded to a team of researchers at TTC. The Phase 2 team also collaborated with experts at the U.S. Army Corps of Engineer Research and Development Center (ERDC) on the study. Phase 2, which was completed in February of 2020, indicated that preliminary data that elevated styrene emissions inside trucks storing uncured liners was worth further investigation.

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Based on this finding and to better understand the buildup of emissions inside liner storage and transport trucks, a Phase 3 project was developed and implemented. The project’s scope was to better understand cured-in-place pipe (CIPP) styrene emissions associated with storing uncured liners prior to installation.

TTC’s Phase 2 and Phase 3 Reports include important safety recommendations for field workers:

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Phase 2 Study “Evaluation of Air Emissions from Polyester Resin CIPP with Steam Cure” February 2020

  • Based on the data collected in this study, it is recommended that PPE be worn at the time of the initial opening of the liner transport truck door or storage unit by those entering the truck. It is likely that the air quality will improve once the door is open, but active air monitoring for VOCs is recommended to ensure a safe work environment in the transport truck or any storage unit.
  • It is also recommended that active air monitoring be performed when entering manholes, which is already an industry practice.
  • Data indicates distances within 10 ft could be a cause for concern. To provide an extra factor of safety it is recommended that a perimeter of 15-ft be implemented around exhaust manholes and emission stacks during curing. This is a conservative distance based on the data collected in this study. This perimeter could be entered for short amounts of time not exceeding five minutes. If this area must be entered for longer than five minutes, suitable PPE should be used.
  • The emissions stacks should be a minimum of 6 ft in height 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. Our team noted that for the taller stacks, when standing in upwind directions it was much easier to avoid the plume. With the horizontal stacks closer to the ground, it was very difficult to avoid emissions when approaching the stack. Workers would have to approach stacks periodically to adjust valves.
  • The data in this study does not suggest additional PPE for the workers around steam cured CIPP emissions sites beyond the recommendations above and what is already standard practice. Standard practice typically includes eye and ear protection, gloves, steel toe boots, safety vests and hard hats.

Phase 3 Study “Evaluation of Styrene Emissions Associated with Various CIPP Coatings in Refrigerated Storage” April 2023

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Phase 3, which began in 2021, included testing in two steps:

  1. The styrene emissions generated inside and around a “test” CIPP storage unit to develop a baseline for monitoring in actual CIPP storage units.
  2. The styrene emissions generated inside and around actual CIPP storage units based upon the findings of step one, while considering CIPP liner sizes, resin weight, liner stacking and liner coatings.

Based on the results of the study, TTC has made the following recommendations to NASSCO:

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  • Once doors are opened and styrene thresholds reduce to below regulatory agencies’ limits for the planned exposure time of workers, the truck can safely be entered for that amount of time with minimal PPE. Please refer to the latest exposure guidelines for styrene for full guidance.
  • If durations must be exceeded, manufacturers could consider using thicker coatings, more impermeable coatings, wrapping the liners with impermeable materials to reduce the release of styrene in the cold storage trucks, additional PPE appropriate for the higher styrene thresholds, etc.

The results of this research will be evaluated and compared to other studies running in parallel with the NASSCO Phase 3 study. The resulting data generated from these concurrent studies will be used to determine if NASSCO should conduct further testing beyond the items described above.

To download the full reports, along with “Guideline for the Safe Use and Handling of Styrene-Based Resins in Cured-in-Place Pipe” and other related resources, visit .

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