Marwell Tar Pit – investigation, assessment and remediation

Challenge

The Marwell Tar Pit contained approximately 30,000 m3 of hydrocarbon contamination consisting mainly of tar from a historical oil refinery which operated in Whitehorse for a short time in the 1940s.

Remediation of the project was important to reduce the risk of contamination to the underlying groundwater system and to eliminate the possibility of impact to the local population from direct contact with the contaminated soils.

Solution

SLR’s strong investigation and assessment teams were selected by the government to undertake the initial phases of investigations and risk assessment including DQHHERA. Following that, remediation design was developed by SLR that would allow remediation to proceed with the minimum of impact to the local community.

The remediation consisted of excavation of the majority of the contaminated soils within the boundary of the tar pit and further extraction of hydrocarbon contamination by heating the soils for a period of time. Following extraction, clean soil was returned to the excavation.

Impact

The remediation was completed successfully in 2019, under the supervision of SLR staff in Whitehorse.

Monitoring of surface water and groundwater is ongoing to demonstrate that the remediation works were successful in mitigating the migration of contaminants into the underlying aquifer.