December 2021 Vol. 76 No. 12
Features
Tunnel Vision
By Michael Kozak, J.D.
A welded PVC waterproofing system was recently applied to an underground rail segment being built in the Washington D.C., Virginia, and Maryland (DMV) area. The system was supplied by CETCO.
Operated by the Maryland Department of Transportation, this 18-mile system allows commuters a swift and environmentally friendly light rail mode of transport between several Maryland suburbs. Additionally, this new infrastructure provides improved regional connectivity for riders from the other three core stations, eliminating the need to travel to Washington, D.C., just to transfer lines.
The operators of the system were faced with an engineering challenge that required a small segment to be constructed underground. This 1,100-linear-foot portion would also be the location of a new station.
In addition to an abnormally complex excavation process, waterproofing the tunnel effectively and efficiently was critical to the success of this project. The waterproofing system chosen for this application was shown to directly contribute to the long-term durability of the tunnel. CETCO’s involvement began in March of 2019, when the company was approached to tap into its vast experience in the waterproofing industry and help develop a solution that would serve the needs of this project.
With decades of experience in developing and manufacturing innovative waterproofing membranes for the construction industry, CETCO offers solutions that address nearly every conceivable building environment. The company’s proven track record of success made it an obvious choice for the owner when assessing competing waterproofing products and systems
Solution
CETCO performed a detailed assessment of the project before recommending its T-100NR, 2.5-mil, non-reinforced PVC-P thermoplastic waterproofing membrane. T-100NR is designed specifically for tunnel projects and offers superior puncture resistance and elongation properties, while performing well under high hydrostatic head pressures and in environments where microorganisms would break down other products. This system is engineered and manufactured to provide waterproofing protection for bored rock tunnels, associated service shafts and subway stations.
Installation began in March 2019 and proceeded through several phases. The specific application of the T-100NR membrane required it be installed directly against the excavated tunnel shoring. This installation would then be followed by the pouring of the structural concrete. The T-100NR membrane served as an impermeable barrier preventing water ingress through the structural tunnel lining. The project utilized over 250,000 square feet of T-100NR by the time the waterproofing phase of the construction was completed in late 2020.
Thanks to quick responses, readily available technical assistance and product offerings that were up to the challenge of this project, a strong relationship was formed between the waterproofing contractor and CETCO. This installation was completed without issue and contributed to the successful completion of this segment of the light rail transit system, all while CETCO’s T-100NR protected the integrity of the tunnel.
In the meantime, when the overall light rail system work is complete, riders of this community-friendly light rail transit system will travel quickly and efficiently between stops.
MICHAEL T. KOZAK, J.D. is the vice president, environmental products & building materials for Minerals Technologies, Inc. He can be reached at mike.kozak@mineralstech.com.
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