NASSCO finalises long-term emissions review

The study initially commenced in 2017 when a report outlined safety concerns with chemical emissions of the resin used during CIPP processes.

NASSCO requested a formal review of the existing literature and now, three years and multiple phases later, the review has been finalised.

Following the release of the 2017 report outlining safety concerns during cured-in-place pipe (CIPP) processes, the National Accreditation of Sewer Service Companies (NASSCO) made a request for proposals for a formal review of the existing literature of the potential safety impacts associated with CIPP, particularly relating to the chemical emissions of styrene-based resins released during the steam curing process.

Speaking to Trenchless International at the time, NASSCO Executive Director Sheila Joy said questions about safety impacts in the industry must always be taken seriously and, when various reports were published questioning the safety of styrene-based resin used in the CIPP process, NASSCO stepped up considering safety is its number one concern.

A non-conclusive initial study

In December 2017, NASSCO awarded a CIPP safety review to researchers at the University of Texas at Arlington’s (UTA) Center for Underground Infrastructure Research and Education (CUIRE), which also received support from Germany’s Institute for Underground Infrastructure (IKT)

By April 2018, the four-month review of the existing literature surrounding chemical emissions during CIPP installations was completed with non-conclusive results presented to NASSCO and researchers recommending additional sampling and data evaluation. 

NASSCO then opened a CIPP emissions study request for proposals to evaluate the potential release of chemicals during pipe rehabilitation using the trenchless method. After reviewing the submitted proposals, the research project was awarded to the Trenchless Technology Centre (TTC) and its partner of choice – the US Army Engineers’ Research Development Center. 

Ms Joy says it was a priority for industry associations and organisations to join forces and present a unified voice to best serve the industry.

“TTC’s proposal to partner with the US Army Corps of Engineers [demonstrated] their understanding of this concept,” she says.

“We all share the same goal when it comes to the safety of our workers and communities, and this study is a perfect example of how unification will reveal the information we need to make smarter decisions for our industry as a whole.”

The second phase 

TTC’s research project – comprising the second phase of the study – measured styrene and other organic compound emissions at six CIPP installation sites, evaluating varying pipe lengths and diameters to accurately capture the variation in emission. 

TTC conducted measurements before, during and after curing at the termination manhole, as well as at various locations in the surrounding outside area and inside nearby buildings, while worker exposure was measured using personal exposure monitors.

Additionally, dispersion modelling was used to estimate compound concentrations at several locations for a wide variety of meteorological conditions. The measured and modelled concentrations were then compared to appropriate health-based action levels to determine any potential health risks.

Final report 

NASSCO released its final report titled NASSCO CIPP Emissions Phase 2: Evaluation of Air Emissions from Polyester Resin CIPP with Steam Cure in early 2020.  

The primary objectives of this project were to measure and quantify worker and public exposure to CIPP emissions, and then evaluate the potential health risks by making adjustments to the data collection and analysis completed in the first phase of the project. 

The report says, based on the data collected and the modelling completed in the study, styrene was the only compound of interest that had the potential to pose health risks and only two primary locations on CIPP sites have the potential to pose health risks to surrounding personnel. 

These two sites are the liner truck immediately after opening and the areas immediately adjacent to emission
point sources. 

Safety findings 

Based on the study’s data, NASSCO has recommended PPE be worn at the time of the initial opening of a liner transport truck door or storage unit by those entering the truck, as it is likely the air quality will improve once the door is open; however, active air monitoring for VOCs is recommended to ensure a safe work environment in the transport truck or any storage unit. 

NASSCO also recommended active air monitoring be performed when entering manholes, although this is already an established industry practice. 

“Data indicated distances within 10 feet (3m) could be a cause for concern. To provide an extra factor of safety it is recommended that a perimeter of 15 (4.5m) feet be implemented around exhaust manholes and emission stacks during curing,” says NASSCO, explaining this is a conservative distance based on the data collected in the 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 fett (1.8m) 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.” 

NASSCO says the data in its study does not suggest additional PPE for the workers around steam cured CIPP emissions sites is necessary beyond the recommendations already mentioned and what is already standard industry practice, which typically includes eye and ear protection, gloves, steel toe boots, safety vests and hard hats. 

Future studies 

Although the second phase of the study provided conclusive results and extensive collection of data beyond what previous studies had, NASSCO says there is still the potential for further data collection efforts.

“Future studies that focus on task-oriented worker exposure to emissions would be helpful in identifying certain tasks within the typical 8-hour shift window that could post potential health risks,” says NASSCO in its report. 

“This could be accomplished through comparing health risk guidelines to measurements calculated by placing sorbent tubes on a worker at the beginning of a task and collecting those sorbent tubes at the end of the task, thereby targeting specific installation tasks at shorter time-weighted average exposures.” 

NASSCO says additional studies are also required to understand the dispersion of styrene from liner trucks after opening, as well as evaluating factors such as the size and number of liners on the truck and the duration each liner is on the truck for. 

“Modelling rogue emission concentrations was not part of the scope of this project, so work should be done to try and capture concentrations from rogue sources and model them to further evaluate health risks associated with these emissions.”

This article was featured in the Summer 2020 edition of Trenchless International. To view the magazine on your PC, Mac, tablet or mobile device, click here.

For more information visit the NASSCO website.

If you have project news you would like featured in Trenchless International contact Managing Editor David Convery at

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