The Columbia National Wildlife Area (NWA) is located in the Southern Rocky Mountain Trench of British Columbia, near the towns of Invermere and Radium, and comprises a series of wetlands adjoining the headwaters of the Columbia River. The four units of the NWA have been managed by the Canadian Wildlife Service since the 1970s and provide an important breeding and resting habitat for migrating birds as they travel along the Pacific Flyway. The NWA also provides an important habitat for non-migratory wildlife, including several species at risk. The project site is located within the Wilmer Marsh Unit of the Columbia NWA and comprises a bench-land of fine-grained glaciolacustrine sediments, which slopes steeply down to the marshlands of the meandering Columbia River, located 60 m below.
The subject site was used as an unofficial refuse dump for several decades. Several environmental assessments and remediation phases conducted between 2002 and present have revealed extensive refuse depositions comprising automobiles, construction materials, metal debris and general household refuse. Waste materials had been dumped within the marsh, cast down the face of the slopes, and had been buried in the upland area of the site. Car bodies had also been used as the foundations of a trail built to access the marsh from the bench. Contaminants of concern comprising metals, polycyclic aromatic hydrocarbons and petroleum hydrocarbons were encountered in the soil, sediment and surface water associated with the debris.
Various debris and soil removal programs have been completed between 1997 and 2017, removing over 9,000 tonnes of debris and associated contaminated soil. The location of this debris and contaminated soil in sensitive ecological habitat, combined with steep, unstable slopes and geotechnically sensitive soils made the execution of remediation programs technically and logistically challenging.
This presentation will outline the methods used during the 2016/2017 remediation phase and the challenges faced when using heavy machinery to conduct a traditional dig and dump excavation program in an environmentally sensitive area. The presentation will outline the importance of bringing together a team of specialists, comprising an earthworks contractor utilizing specialist earthworks equipment, biologists, geotechnical specialists, contaminated sites specialists and the responsible regulatory agencies, to ensure that the objective of safely removing as much debris as possible from the slopes was met; whilst also limiting disturbance of the sensitive environment, and restoring the site to a state that approached pre-dumpsite conditions. However, it was not possible to remove all debris during the 2016/2017 remediation program, therefore this presentation also outlines the techniques subsequently utilized to deal with the debris that was left in place.