Sewer Line Rehabilitation
Each year, Mt. Lebanon has a percentage of its sewers inspected. From time to time, those inspections reveal some lines that need to be repaired. One of the repair options uses a procedure called lining, to avoid having to dig a trench at the site of the line. It involves cleaning the line, temporarily re-routing the drainage and inserting a liquid resin which is then heated to create a new smooth inner surface. The line is then inspected again and the flow is restored. It is generally quicker and cheaper than digging and replacing the sewer line. The procedure is usually used on sanitary sewers (sewers that carry household waste water) but can be used on storm sewers (sewers that carry rain runoff.)
If the sewers near your home need to be lined, you will be notified. Read on for more detailed information.
The report serves as a final report as required under the scope of thePhase 2 project sponsored by National Association of Sewer Service Companies (NASSCO) entitled “CIPP Emissions Testing”. The scope of the project aims to measure air emissions from steam-cured, cured-in-place pipe (CIPP) installations; and determine potential impacts on workers and the surrounding community.
The primary project objectives of this project were to (1) measure and quantify worker/public exposure; and (2) evaluate potential health risks to workers and the public to CIPP emissions.
The research approach for the most part followed the scope of work outlined in Phase 1 of the project. The Phase 2 team made adjustments as necessary to the data collection and analysis. Many of the adjustments were due to unforeseen issues with equipment, sampling, site conditions and personnel. The following tasks were to be completed within the scope of the project.
- Directly measure worker/public exposure to emissions for locations onsite or immediately off site for several CIPP installation sites that represent a range of scenarios typical of CIPP installations.
- Model the dispersion of emissions to estimate compound concentrations for a large set of scenarios to include multiple locations and weather conditions.
- Evaluate potential health risks to workers and the community based on appropriate health-based action levels using both directly measured and modeled data.
Based on the data collected and the modeling completed in this study, styrene was the only compound of interest found at concentrations that had the potential to pose health risks. It was also determined that two primary locations on CIPP sites have the potential to pose health risk to workers and/or the public. The first is the liner truck immediately after opening and the second includes areas immediately adjacent to emission point sources (within 10 feet). It is recommended that suitable PPE with active air monitoring be worn at the time of the initial opening of the liner transport truck door 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 a conservative perimeter of 15-ft be implemented around exhaust manholes and emission stacks during curing. This perimeter could be entered for short amounts of time not exceeding 5 minutes. If this area must be entered for longer than 5 minutes, suitable PPE should be used. The emissions stacks should be of vertical configuration at a minimum height of six feet to enhance the dispersion of emissions and lessen the likelihood of workers entering the perimeter from having to cross into emission plumes. 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.
RECOMMENDATIONS FOR FUTURE STUDIES
While this study represents an extensive collection of data beyond what previous studies have accomplished, 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 pose potential health risks. 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. Additional study is also needed to understand the dispersion of styrene from the liner truck after opening. Additional measurements taken at the liner transport truck over a 5-minute period after opening the cargo door would be useful in making any final definitive conclusions related to PPE or dissipation time. Also, factors such as the size and number of liners on the truck as well the duration each liner is on the truck could be evaluated. Capturing 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 to evaluate health risks associated with these emissions.