Continuous Monitoring and Response to Vapor Intrusion

By October 4, 2016 March 25th, 2019 No Comments

Our friends at Cascade Technical Services, Hartman Geosciences, and Groundswell technologies recently gave a talk entitled “Continuous Monitoring and Response to Vapor Intrusion”, about the advantages of continuous monitoring using trichloroethylene (TCE) as an example.

Trichloroethylene has been a subject of multiple lawsuits. IBM Corp. recently settled a lawsuit by 1,000 plaintiffs who alleged that toxic spills from the company’s former Endicott manufacturing plant caused illnesses and deaths, damaged property values, and hurt businesses. In another example, faculty and staff at Oakland Charter High School recently complained that they unaware that they being exposed to TCE and other poisonous compounds. Clearly, more robust monitoring technologies can and should be used for these and many instances.

Trichloroethylene has a cancer-based target of 0.48 ug/m^3 which may take years to achieve. However, the developmental-based target of 2 ug/m^3 only takes days to week to achieve. Thus, failure to account for variability of TCE is a concern for chronic exposure, but a far greater concern for short-term exposures, as the developmental-based target for TCE clearly shows.

New legislation for TCE by Ohio’s EPA for the first time demanded immediate action when contaminant levels exceeded certain established “trigger” levels. In the case of TCE, the Agency expects action within days if the trigger levels are exceeded. This guidance has major implications for businesses, property owners, consultants, and attorneys. The guidance established specific trigger levels for sub-slab vapor and indoor air and mandated that if those levels were exceeded, immediate follow-up action was required. Other states may soon enact such standards.

This new legislation makes it clear that continuous monitoring helps to protect against risks from short-term and also long-term exposure to TCE. Continuous monitoring catches the peaks in indoor air concentration. This is critical because studies have shown variability ranges from two to four orders of magnitude at any site and that discrete measurements will be below the long-term average by one order of magnitude, making it likely that current discrete sampling methods will miss high concentrations.

The challenge is to provide sufficient temporal and spatial resolution to understand the problem, in order to understand 1) the risk to building occupants over acute and chronic time frames, and 2), to elucidate sources of the indoor air contamination. A high resolution system includes temporal resolution, spatial resolution, and immediate response. Temporal resolution may include high frequency monitoring every 10 minutes or less, to observe dynamics, trends, and determine causes. Spatial resolution may include up to 30 locations, to help identify intrusion areas and indoor sources. Immediate response is aimed at exposure prevention, and may include automated alerting and automated engagement of controls.

In this scenario, it was found that opening a door caused a massive drop in TCE. Such information would help titrate the on and off times for a HVAC system in the building to limit TCE exposure.

Sampling systems usually include a small footprint and can be made relatively stealth. Sampling lines come up to 300m from the instrument and include small diameter tubing (1/8” or ¼”). Operation and maintenance may involve only changing nitrogen every 3 to 5 months and calibration holds for months. Internet connectivity and external controls of HVAC system are all possible. Auto-alerting to your smart phone can alert property managers of real time exceedences of trigger levels, and HVAC system can be turned on and off on demand. Groundswell currently offers monitoring software to make this all possible.

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