Chlorinated Solvents Treated Using “Trickle-Down” Method
Location: Former Dry Cleaner Site in Southwestern Ontario
Contaminant: Chlorinated Solvents, mainly Tetrachloroethylene (PCE)
Concentration: Up to 480 ug/L PCE in groundwater and greater than 10 ug/g PCE in soil
Soil Type: Silty Clay Till
Historic releases caused significant migration of PCE into soil and groundwater. Major challenge encountered: impacts greater than 6 mbgs in silty clay till beneath occupied building. Facility had to be kept operational during remediation, including indoor excavation, injection well install and oxidant injections.
The Vertex Approach
• Acquired all relevant permits to complete the in-situ remediation program.
• Successfully completed indoor excavation to remove all impacted soils to 3 mbgs with no disruption to neighbouring units.
• To access deeper contamination, innovative infiltration boreholes were drilled and backfilled to 6 mbgs with custom blend of sand and oxidant.
• “Seeded” base of excavation at 3 mbgs with additional oxidant and installed horizontal injection well system.
• After backfilling, injected oxidant solution into horizontal wells and allowed it to “trickle-down” into the boreholes to migrate laterally into fractured silty clay till.
• Greater than 98% reductions to groundwater and soil impacts with no breakdown products generated.