Sub-slab soil vapour and indoor air sampling and analysis are common lines of evidence for assessing potential risks to human health associated with subsurface vapour intrusion to indoor air for volatile organic compounds (VOCs). Conventional sub-slab soil vapour sampling has shown substantial spatial variability. Indoor air sampling has shown substantial temporal variability and is also susceptible to false positives from interior sources. This often makes data interpretation difficult. Through funding by the United States Department of Defense, new methods and technologies have been developed that reduce the variability in vapour intrusion assessment, especially in large buildings. Two main tools were used to improve our understanding of the vapour intrusion conceptual site model: high volume sampling (HVS) and building pressure cycling (BPC). These will be discussed along with case studies to demonstrate these new technologies.

HVS is a new method of monitoring sub-slab soil vapour over a large area and extracts a large volume of soil vapour from beneath the floor slab of a building. Laboratory samples are taken at predetermined intervals for speciation and regular field screening is conducted to assess the trend of VOC concentrations as a function of the volume removed. This method provides insight into the spatial distribution of vapours at progressive distances away from the point of extraction. HVS sampling can also provide all the design data needed for mitigation system design at the investigative stage for minimal additional cost. This approach not only minimizes the risk of failing to identify the areas of elevated soil vapour concentrations that may exist between discrete sample locations but does it with fewer holes drilled through the floor and fewer samples for analysis. This results in a higher level of certainty with comparable or lower costs compared to conventional methods.

BPC is a technique for quickly characterizing building susceptibility to vapour intrusion, determining interior sources and estimating the potential vapour intrusion risks. BPC can control the pressure inside a building by using a blower door or existing air handing units to depressurize or pressurize the building. Under these conditions, vapour intrusion can be enhanced or inhibited. Indoor air samples are collected during each of these steps for laboratory analysis to evaluate if vapour intrusion poses a potential concern. BPC tests can be conducted in one day for most buildings and can provide data that characterizes the range of potential impacts that may arise from vapour intrusion and background sources under the typical operating conditions. By controlling the building to represent seasonal/operational changes it provides a higher level of certainty that you did not sample on the “wrong” day and eliminates the need for seasonal sampling. This results in lower costs while providing data to rapidly evaluate sites for vapour intrusion and strengthen risk management decisions.

Darius Mali, Remediation Engineer, Geosyntec Consultants, Inc.
Darius Mali is an engineer with Geosyntec Consultants, Inc., where he leads field events and manages projects specializing in vapour intrusion site characterization and mitigation system design. Darius has worked with the vapour intrusion team for the past six years on projects ranging from traditional residential sampling to Department of Defense facilities with buildings of over one million square feet. Darius is part of the R&D group at Geosyntec Consultants, always looking for new and innovative ways to push the industry forward.

While many of us take the quality of the air we breathe for granted, the Fort McKay First Nation (FMFN) were determined to develop a community-based air monitoring station in their remote territory to assess air quality changes in an area of increased industrial development. FMFN, with assistance of Wood, designed, built and installed an off-grid solar powered air quality monitoring station.

The FMFN is in the heart of the Athabasca Oil Sands Region where the ongoing expansion of oil sands development poses growing risks to an even greater portion of the FMFN’s traditional territory. Of significance is the Moose Lake area, a culturally and historically sacred region for the FMFN, located 60 km northwest of Fort McKay. Currently the Moose Lake area is relatively pristine. The area is of immeasurable importance as a refuge for FMFN members to be able to safely practice their rights away from the disturbance and cumulative impacts of oil sands development that surround their home at Fort McKay.

FMFN’s Namur Lake air monitoring station (AMS) consists of three highly modified sea-cans, an Airpointer® (which continuously monitors: PM2.5, NO/NO2/NOx, SO2, H2S, O3, and BTEX ¬– benzene, toluene, ethylbenzene and xylene), thirty-six 260W solar panels, two charge controllers, an inverter, back-up generator, and twenty-four deep cycle 2V batteries (weighing a total of 8,000 lbs.). During peak power production, combined solar panel charging to the batteries has reached just over 10,000 watts. Two key development constraints were the need to develop a reliable, stable and remotely accessible energy system and the 10 helicopter trips with two different helicopters required to mobilize equipment to the remote site.

Since becoming operational in late 2016, the AMS has remained online with only minor system resets, maintaining greater than 90% operational uptime each month. The solar charging system remains fully functional with remote access maintained 24/7. The AMS has regularly measured impacts on air quality in the Moose Lake area. The frequency and concentrations measured have been, at times, quite surprising given that the closest oil sands mining facility is approximately 50 km away.

This station, which uses solar power as its primary energy source, represents, to our collective knowledge, the first of its kind within Canada. This ground-breaking project reinforces the need for early collaboration and dialogue among an interested community and subject matter experts to increase the likelihood of a successful outcome. The configuration of the station allows for the possibility of developing a wide-reaching air monitoring network not tied to the conventional power grid. The yearlong functionality of the station demonstrates the viability and the potential for greater adoption in other locations.

This presentation will demonstrate how community-based monitoring can be an extremely powerful tool when it comes to obtaining continuous air quality data in a remote location, creating new understanding, and illustrating the need for stringent regulation by Alberta to protect an area of incredible importance to the FMFN.

Scott Robertson, Office Manager, Environment Group, Environment and Infrastructure Solutions, Wood
Scott Robertson is currently the Office Manager for the Edmonton Environment Group for Wood Environment and Infrastructure Solutions. Scott provides senior review and technical direction for the soil and terrain disciplines as well contributes to the development of conservation and reclamation plans. Scott has twenty years professional experience in geomorphology, terrain analysis, and soil survey and classification. Scott has completed of aerial interpretation for nearly 3.5 million hectares in western and northern Canada at a variety of mapping scales in support of a variety of surficial geology mapping programs. As Office Manager, he leads a team of remediation, reclamation and permitting scientists and professionals.

Upland remediation of the Middle Harbour Fill Site (MHFS) was undertaken by Public Services and Procurement Canada on behalf of Transport Canada. MHFS is located on Laurel Point Peninsula, approximately 350 m from Victoria's downtown core. The main activity of concern was the historical operations of a BAPCO paint factory that had occupied the site between 1906 and 1976. The primary contaminants of concern were metals, polychlorinated biphenyls (PCBs), and various hydrocarbons – most at hazardous waste concentrations. Upland remediation work began in October 2018 and ended in June 2019. Remediation consisted of excavating approximately 75,000 tonnes of hazardous waste and soil with chemical concentrations exceeded commercial land use standards (CL+) and loading it onto barges for transport to Vancouver.

Given the potential for dust and odour concerns, the nature of the contaminants being remediated (PCBs, metals, and hydrocarbons), and the proximity of the project to a major urban centre (350 m from downtown Victoria), a Neighbourhood Air Quality Monitoring Plan (NAQMP) was developed and implemented. The NAQMP was an investment made by Transport Canada to protect people living and working in the vicinity of the MHFS project.

The NAQMP program that was developed included a combination of real-time and 24-hour time-integrated sampling for a variety of contaminants of concern, including: benzene, toluene, ethylbenzene and xylenes (BTEX); volatile petroleum hydrocarbons (VPH); light extractable petroleum hydrocarbons and fraction 2 hydrocarbons (LEPH/F2); naphthalene; polycyclic aromatic hydrocarbons (PAHs); as well as, fugitive dust assessed as total suspected particulate (TSP); 10-micron particulate matter (PM10); and, 2.5-micron particulate matter (PM2.5).

Three local First Nation monitors were employed to assist with daily sampling at three monitoring stations around the perimeter of the project site to ensure constant monitoring downwind of site activities. An on-site meteorological station provided real-time site-specific wind direction, wind speed, and temperature data. Results were compared to site specific health-based trigger values for both acute (24 hour) and chronic (lifetime) exposure. The trigger value for TSP was developed to be protective of particle-bound contaminants (e.g., metals and PCBs). The TSP trigger value was developed using a model that predicted air quality based on soil concentrations found at MHFS during the investigation phase and on the expected construction activities.

Throughout the project, concentrations of TSP, PM2.5, and benzene greater than the trigger values were recorded in real-time samples. Persistent (longer than one hour) real-time exceedances occurred four times and two inquiries regarding dust deposition were received. Each time, the exceedances and inquiries were successfully managed according to the NAQMP. Concentrations of time-integrated samples were less than trigger values throughout the project.

Based on the results collected during the project, the NAQMP was successful in managing the quality of air leaving the MHFS. That is, we identified no unacceptable risks to the general public living and working in the vicinity of the site as a result of exposure to vapours, odour, and particulate matter generated during the MHFS remediation project.

Karey Dow, Senior Project Manager and Business Leader, Hemmera
Karey Dow is a Senior Project Manager and Business Leader at Hemmera and she specializes in land transaction due diligence and Brownfield redevelopment. She is a Professional Agrologist and Project Management Professional with 18+ years of experience in environmental consulting in British Columbia.