Trends Summer 2018 - Page 18

That revelation spurred a series of environmental next-steps. In May of 2016, Ayres performed a Phase 1 environmental site assessment (ESA), which researched the property’s history. Since this assessment identified a recognized environmental condition (i.e., a former dump or landfill), Ayres’ experts recommended a Phase 2 ESA be conducted. This type of assessment literally digs a bit deeper, involving soil samples and laboratory analysis. “We put in test pits around the subject property in July of 2016, ACTIVE VS. PASSIVE SYSTEMS Vapor mitigation systems can be either active or passive. Active systems feature a blower or other mechanical device to extract vapors beneath a building. Passive systems don’t have that blower and instead rely on changing natural atmospheric conditions to remove vapors. Knowing which type is needed where depends on the building site’s level of contamination and/or the contaminant(s) of concern. Sub slab samples can be collected to verify contaminate levels to further determine if an active system is needed. Passive systems are generally used with more minimal contamination threats. Passive systems can be easily retrofitted into an active system if the need is discovered later. TYPICAL CONCEPTUAL MODEL OF VAPOR INTRUSION Resident living over plume Basement or crawl space | Without basement Stack effects Wind effects Indoor air Vapor intrusion through cracks in foundaon slab Ulity line Silt Vapor intrusion through floor-wall cracks Soil contaminated with volales Soil vapor migraon Vadose zone soil gas Water table Groundwater plume of volales Groundwater contaminaon 18│ TRENDS and a couple of the samples we collected contained elevated levels of VOCs (volatile organic compounds),” Rosemore said. “We also identified PAHs (polycyclic aromatic hydrocarbons) and some metals, but the primary concern was the VOCs.” Because of the heightened levels of VOCs, coupled with elevated methane levels discovered in the soil borings taken for a nearby roadway, Ayres recommended that gas probes be installed with Geoprobes soil borings to further assess the situation. “We found elevated levels of some VOCs in our air samples,” Rosemore said. “Because of the gas probe results, we recommended, at a minimum, that they put in a passive vapor system.” Ayres’ environmental engineer Ryan Shimko designed the vapor system and explained that, much like how a radon system removes radon gas from a home, vapor mitigation systems prevent harmful gases and other contaminants from entering a building. “The vapor’s always been the forgotten contaminant,” Shimko said, noting that soil and groundwater contamination tends to be more closely monitored. So what might happen if vapors were to enter a building? Shimko said it depends on what the vapors are. “Methane is odorless, and it’s explosive,” he said. “So if methane is your concern, then it’s an explosive risk. If it’s volatile organics, then it’s a health concern.” Adding a vapor system is “just a safeguard for human health,” added Tim Shupert, a CADD technician at Ayres and draftsperson on the project. Ayres Associates designs vapor systems at sites across the country, the vast majority on former brownfield sites or landfills where new developments are being planned. Such is the case in Glendale,