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A Look Into A Vapor Mitigation Project

Nova Consulting Group, Inc., provided a potential property buyer in Boise, Idaho, with Phase I environmental due diligence services in August 2017. This led to a discovery that the property had used a Perchloroethylene (Perc) machine for spot-cleaning rugs for the past 40 years. The machine was still on site.

The owner of the property (with the original client’s permission) then hired Nova to do a Phase II investigation that measured sub-slab vapor and indoor air impact from Perc, which is a volatile organic compound (VOC).  Field screening was conducted with a photoionization detector (PID) to measure VOCs in the breathing space and sub-slab sampling locations. Detections were noted in both areas.  The team then used SUMMA canisters to obtain samples for EPA TO-15 laboratory analysis and found high detections of Perc in sub-slab data and indoor air samples.

The owner then retained Nova to come up with a remediation plan to mitigate the indoor air VOC issue,  and provide follow up testing. Nova had the property owner remove the machine and steam clean the inside of the building. The plan was to seal the existing floor and mitigate vapors by creating sub-slab vent points that exhausted through a vent fan utilizing a radon mitigation system. The system is known as sub-slab vapor mitigation when mitigating chlorinated solvents.

Prior to mitigation, the radon company pre-tested for radon, showing over 4 picocuries per liter in the breathing space, exceeding EPA guidelines. Interestingly, radon acts very much like other gases such as Perc in the subsurface and breathing space. Often radon mitigation systems, which are readily available, can be used to mitigate Perc or other chlorinated solvent indoor air or sub-slab issues.  Therefore, for cost efficiency, we utilized a local radon-mitigation firm for the remediation implementation. Nova discussed both placement of the vacuum points and system components with the radon company, prior to installation.

After they installed the system and it ran for a week, they could not detect radon in the breathing space. Nova used this radon screening as an indicator that it may have also solved the Perc problem in the breathing space. To confirm the radon results, with our previous screening results, Nova had a local lab screen the indoor air with a PID for Volatile Organic Vapors; it showed no detections. Nova then resampled with SUMMA canisters for TO-15 analysis in the breathing space. Our results showed a 99.6% reduction in contaminant mass within 10 days of system operation. With the new data, the owner was able to sell the property in December 2017.

This is just one example of what Nova does every day—solving clients’ problems and supporting real estate development in an environmentally responsible manner.

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Mike Minett smallMike Minett

VP – Mid-Atlantic Regional Manager

Nova Consulting Group Inc.

(704) 258-5196




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