During the Geotechnical Investigation conducted at the project location for a new building, ENG-TECH Consultants Limited (ENG-TECH) identified probable impact in the soil from diesel fuel based on staining and strong odour.
A Phase II ESA was subsequently conducted to assess soil and groundwater conditions in the area where the diesel impact was observed to determine if PHC concentrations were greater than the applicable guidelines and to delineate the anticipated diesel impact. The diesel impact at the site was delineated and determined to be from approximately 3.0 metres below grade (mbg) to 3.8 mbg and covered an area of approximately 25 m². The client made arrangements for the contractor to conduct the excavation with ENG-TECH responsible for supervision of the remedial activities. The RAP required the excavation of unimpacted soil (above the PHC-impacted zone) to be stockpiled on site prior to the excavation of the impacted soil since it would be used as backfill for the excavation to reduce the amount of imported fill required to backfill the excavation.
The excavation was conducted using a trackhoe and the impact soil was hauled from site using a tandem truck. Approximately 300 tonnes of PHC-impacted soil was excavated and disposed of at the nearby landfill. The excavation was backfilled with the clean overburden soil stockpiled at the site and additional clean soil that was brought to the site.