EJQ6 - Fall 2025 - Journal - Page 18
Traces Québec and introduced royalties in 2024 to encourage treatment
and valorization—further tipping the scales toward onsite solutions.
Why ISS belongs in the excess soil conversation
Traditional “dig-and-dump” site remediation approaches send thousands of truckloads of soil o昀昀site—incurring tipping fees, logistics risk,
and a high carbon footprint. ISS can reduce or eliminate that by treating
soils in place, so they stay on site as engineered 昀椀ll.
Bene昀椀ts typically include:
Waste avoidance: Fewer exports to land昀椀ll.
Schedule control: Treatment and veri昀椀cation occur
within the project footprint.
Cost predictability: Less hauling and fewer disposal uncertainties.
Performance: Low permeability and adequate uncon昀椀ned compressive strength (UCS) to support redevelopment.
Critically, those performance claims are not handwaving. The U.S. Environmental Protection Agency’s guidance treats ISS as an established
technology and points to strength and permeability as core veri昀椀cation
metrics, e.g., UCS ≥ 50 psi (~345 kPa) as a baseline indicator. Owners often specify more stringent targets depending on enduse.
Three ISS methods suited to Canadian projects include the following:
Mass Soil Mixing with Cementitious Binders (Solidi昀椀cation) Mixing tools such as largediameter augers or bucket mixing blend soil
with binders (e.g., Portland/slag cement, bentonite). The result:
a low-k, higher-UCS matrix suitable for capping, back昀椀ll, or subgrade
support—particularly e昀昀ective for polycyclic aromatic hydrocarbons
(PAHs), pentachlorophenol (PCPs), metals, and oily sludges at legacy
industrial sites.
Cuto昀昀 Walls and Permeable Reactive Barriers (PRBs) - Whether
soil-mixed or delivered via trenching, cuto昀昀 walls and reactive barriers
can be a very cost-e昀昀ective method of containing any large contaminant mass. Once the direction of groundwater 昀氀ow is con昀椀rmed, a strategically placed cuto昀昀 wall can prevent the excavation and land昀椀lling of
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