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 founda on slab
U lity line
Silt
Vapor intrusion through
floor-wall cracks
Soil contaminated
with vola les
Soil vapor migra on
Vadose
zone
soil gas
Water table
Groundwater plume of vola les
Groundwater
contamina on
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,