When to Use Continuous Monitoring to Resolve Vapor Intrusion Challenges

Several common questions arise when investigating a site for potential vapor intrusion related challenges. Often it is difficult to discern whether vapor intrusion is occurring and if so, where it is entering the building. Additionally, it is important to be able to identify the composition of intruding vapors, because certain harmful vapors such as trichloroethylene (TCE) require immediate action to minimize health risks and associated liabilities. Once vapor intrusion is discovered and mitigation ensues, an added concern is whether or not the mitigation achieved key risk reduction objectives or actually increased potential exposures. In the past, each of these concerns has been difficult to address with traditional canister and sorbent sample monitoring methods because of their propensity for false positive and false negative conclusions and insufficient sampling resolution in dynamic settings. However, technological developments over the past decade have rendered continuous monitoring platforms viable and cost-effective solutions capable of addressing each of these concerns.

Vapor intrusion mitigation
At this site, Retro Coat™ Vapor Intrusion Coating was implemented to mitigate risk of vapor intrusion.

VaporSafeTM, an automated laboratory grade analytical and reporting solution developed by Groundswell Technologies and Hartman Environmental Geoscience, is a near real-time continuous vapor monitoring and response platform capable of tracking chemical concentrations from up to 30 locations as far as 300m from the instrument. This system is used to assess whether vapor intrusion is an issue, determine the vapor composition, distinguish between indoor sources and vapor intrusion, and to quickly identify vapor entry locations. VaporSafe is particularly useful for sites experiencing trichloroethylene (TCE) vapor intrusion concerns because these sites require rapid response to minimize health risks and associated liabilities. Unlike traditional monitoring methods, VaporSafe responds to acute TCE risks within minutes – well before an exposure duration of concern has transpired.

vapor intrusion monitoring
VaporSafe is particularly useful for sites experiencing trichloroethylene (TCE) vapor intrusion concerns

The VaporSafe data patterns enable rapid resolution and advancement to the next step in the site management process. As such, this technology can be integrated into projects during several phases: during initial screening and due diligence efforts; when monitoring to confirm no risk; to rapidly identify vapor entry points; to distinguish between indoor sources and vapor intrusion; to optimize mitigation systems; and to prevent current and future exposures through automated response. Because this technology produces key patterns and correlations within hours, it is also useful for efficiently resolving questions during escrow for property transactions and Brownfield redevelopment efforts. VaporSafe makes it possible to anticipate and correct problems before concentration levels become acute – saving time, money and energy. For more information, go to groundswelltech.com/VaporSafe.

Vapor Intrusion Characterization and Management Solutions: The Case for Continuous Monitoring

Vapor intrusion is challenging to characterize for a multitude of reasons. For example, many cases involve indoor background sources, preferential subsurface migration pathways, shallow subsurface and indoor concentration dynamics, or limitations associated with manual monitoring. Typically, canisters and passive diffusion samplers are used to measure and monitor potential vapor intrusion exposures. Unfortunately, these types of samplers don’t provide sufficient temporal or spatial resolution in dynamic settings. As a result, this method has a propensity to yield false-negative and false-positive results. In addition, the time required to obtain a result is longer than the acute TCE exposure duration of concern, so these options can result in unhealthy exposures and liabilities.

Thanks to technological advances, continuous monitoring platforms are now being used to characterize and monitor vapor intrusion. These platforms are made of multiplexed lab grade analytical components with quality control features to automatically generate geospatial time stamped renderings and time weighted averages through a cloud-based management platform. Continuous monitoring platforms provide auto alerts and responses within one minute of the threshold exceedance detection. Further, these platforms provide superior temporal and spatial resolution based on high frequency repeat analyses from strategic monitoring locations, resulting in an optimized remediation design and unequivocal mitigation system performance confirmation. Blower and HVAC controls can also be engaged automatically when needed.

Continuous vapor intrusion monitoring
Continuous monitoring platforms provide auto alerts and responses within one minute of a contaminant vapor exceedance detection

Until a few years ago, cost and instrumentation limitations rendered continuous monitoring systems impractical. Automation and multiplexing now make it possible to perform rapid, cost-effective and continuous assessment and response with a single instrument. For example, a cost comparison analysis of a series of common monitoring scenarios showed that continuous monitoring platforms were cost-competitive when 5 or more locations were being monitored (read the full article here). Automated response capabilities also provide for acute TCE risk prevention, which is not possible with any other monitoring method.

Regulatory support for these platforms has enabled property owners and their consultants to more accurately address potential liabilities, reduce unnecessary remediation costs, produce more effective and surgical remediation strategies, and allow practitioners to most effectively evaluate remediation system performance. More specifically, continuous monitoring allows practitioners to quickly (within a day or two) determine whether vapor intrusion is an issue, and if so, to identify the vapor entry location(s). Once mitigation has been engaged, continuous monitoring is used to confirm that risk reduction objectives have been met. When aggressive remedies such as thermal remediation and oxidation are employed, continuous monitoring is used to assure all stakeholders that fugitive emissions are managed appropriately and to inform site managers when system adjustments are required.

vapor intrusion mitigation
Once mitigation has been engaged, continuous monitoring is used to confirm that risk reduction objectives have been met.

Any project manager considering using in-situ thermal heating would be well advised to use continuous real-time monitoring of the rapidly changing emission scenario.  We have been able to anticipate and correct problems before the concentration levels became acute, which has saved time, money and energy.” – EPA Project Manager

It is clear that many of the difficulties associated with characterizing and managing vapor intrusion can be eliminated with continuous monitoring and response.  These systems should therefore be considered by industry practitioners as a cost-effective and viable method for quickly resolving vapor intrusion challenges.