Recently, Vapor Mitigation Strategies completed a single-day install of a 4,600 square foot chemical vapor barrier system in St. Louis, MO. At the site, the previous building had been a car service center for more than 70 years, and when the property was purchased by a bank, the bank decided to tear down and build a new structure on the existing lot.
Before completing construction of the new facility, the owner opted to have a chemical vapor barrier installed as a preventive measure. This decision was made because improper handling, previously unregulated disposal, or accidental spills and leaks of these car service chemicals may have introduced themselves into the subsurface where they emit toxic gasses into the soil vapor. Although not immediately, these chemical vapors can cause air quality and health concerns for occupants of buildings directly over and adjacent to the source contamination.
“After bidding a competitive price, the owner chose us to install the chemical vapor barrier system between the slab-on-grade and base,” said Wes Robb, director of technical strategies and applications at Vapor Mitigation Strategies, a St. Louis-based Wellington Environmental Company that offers vapor intrusion barrier solutions to new building projects and existing structures.
Robb continued, “This system will reduce the risk of exposure to vapor emanating from subsurface contamination through the concrete floor and utilities openings of the building (known as vapor intrusion).”
For the new site owner, Vapor Mitigation Strategies installed Geo-Seal Spray-on Membrane Gas Vapor Barrier, which includes three layers: 5 mil Geo-Seal FILM 5 (High-density polyethylene layer), 30 mil Geo-Seal CORE (Spray-applied copolymer modified asphaltic membrane), and an 18 mil Geo-Seal BASE (High-density polyethylene layer).
To install this system, Vapor Mitigation Strategies’ crew prepared the surface by removing potential penetrating materials. Next, they rolled out the lowest layer of tarp, the 18 mil Geo-Seal BASE (high-density polyethylene layer), and made cut-ins around the uprights. This step was followed by the application of the 30 mil Geo-Seal CORE (spray-applied copolymer modified asphaltic membrane) on the first layer of closure to all seams and uprights of the tarp. Next, they rolled out the final tarp, the 5 mil Geo-Seal FILM 5 (high-density polyethylene layer) and applied a second seal to all the seams and uprights. Lastly, they measured thicknesses and conducted a smoke test to ensure the chemical vapor barrier system was installed properly.
This solution, which has been accepted by state environmental agencies, branches of the military, and environmental consulting firms around the world, takes the advantages of chemically resistant, high-density polyethylene and combines it with the benefits of spray-applied membranes.
“Vapor Mitigation Strategies did an excellent job of coordinating their work with our general contractor,” said Kevin Lasater, owner’s representative and president of Doubletree Construction Consulting, LLC, who has been in the construction industry for 40 years. “They installed the chemical vapor barrier on-schedule and within budget, and the new property owner was very pleased with their competitive price and quality of their work.”
With this new chemical vapor barrier system in place, the bank mitigated any potential vapor intrusion issue and reduced the risk to human health.