EJQ2 - Fall 2024 - Journal - Page 54
this larger contaminant loading might have greater impacts to the
environment. Consequently, new and more conservative standards were
developed to take this into account; for example, the ESQS, with most
of these values being signi昀椀cantly lower than the already conservative
brown昀椀eld standards.
But was this extra level of caution and conservatism necessary? Arguably
it was not. There are two main lines of reasoning for this.
Firstly, the brown昀椀eld standards already incorporate many conservative
assumptions and approaches that have a net e昀昀ect of making the
standards over-protective in most cases, or put di昀昀erently, they
already include signi昀椀cant “safety factors” (even if such factors are not
explicitly included in their derivation). This is entirely appropriate when
developing generic standards that need to be broadly applicable across
the province. But the level of conservatism in this process should not
be underestimated. It is not the intent here to fully explore this topic,
but a case in point is the conservatism involved in the leaching-based
pathways. Practitioners across the province can attest based on years of
experience working with these standards that contaminant leaching does
not occur under real world conditions at the rates that would be predicted
by the models. Groundwater impacts are instead found at sites
where signi昀椀cantly higher source concentrations occur in soil, or
where contaminant discharges more directly come into contact with
groundwater.
The other (and arguably more important) reason that the
development of more conservative ESQS was not necessary
revolves around the very di昀昀erent context between excess soils
on the one hand, and soils in a brown昀椀eld context on the other
hand. Contaminated sites and brown昀椀elds by their very nature are
expected to have soils impacted by chemical contaminants. When
soil quality standards are applied in this context, they can e昀昀ectively
become clean-up standards. It is therefore not an
unreasonable expectation that fairly signi昀椀cant
volumes of soil could hypothetically occur at such
sites, with chemical contaminants present at
concentrations at or close to the standard.
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However, in an excess soils context, this would
rarely be the case. These soils are generated in a
construction context for a multitude of infrastructure
BROWNFIELDS AND
CONTAMINATED SITES
WITH THE CANADIAN
BROWNFIELDS NETWORK
E N V I RON M E N T J OURN A L QUA RT E RLY RE PORT • FA L L 2 02 4 • P AGE 5 4
