Reclaiming a Mine with Biosolids: a Case Study from Vancouver, BC

Mining operations typically result in degraded soils lacking in nutrients, organic matter, and other biological characteristics that are not optimal for vegetation. Research has shown that the use of biosolids as a soil amendment can improve soil health to promote successful revegetation, often more successfully than the conventional application of topsoil and fertilizer.

For over 25 years, biosolids have been used in several aggregate (i.e., sand and gravel) mine reclamation projects in British Columbia, Canada (see Han and Teshima, 2005 for more examples). This post highlights a biosolids utilization project in Vancouver, British Columbia, Canada completed in the year 2000 where SYLVIS collaborated with Metro Vancouver Regional District (Metro Vancouver) to transform a gravel mine into a regional park with the use of biosolids and biosolids compost. Metro Vancouver is an entity that administers resources and services which are common among 23 local authorities, including water, wastewater, solid waste, and the development and maintenance of regional parks. SYLVIS is a residuals management consulting and contracting firm based in Canada that has implemented municipal and industrial organic residuals for beneficial reuse applications, including mine reclamation using biosolids.

Aldergrove Lake Regional Park Gravel Pit Reclamation

In the 1990s, SYLVIS was retained by Metro Vancouver to restore a former gravel mine site. Metro Vancouver’s goal was to restore the gravel mine site and incorporate this portion of land into the Aldergrove Lake Regional Park. Figure 1 shows an image of the gravel mine site prior to any reclamation activities.

Figure 1: Gravel Mine Prior to Reclamation

Prior to the full-scale reclamation, SYLVIS conducted a small-scale study from September 1997 through April 1998 consisting of the application of different organic residual treatments (e.g., biosolids, biosolids compost, inorganic chemical fertilizer, etc.) to small experimental plots. The biosolids and biosolids compost treatments produced the most above-ground vegetation from the experimental plots, approximately 13 times more than the control (no treatment). To protect the environmentally sensitive aquifer from potential negative impacts, the small-scale study also measured water samples and tested for nitrogen, phosphorus, carbon, and trace elements. Due to these experimental study results, SYLVIS and Metro Vancouver decided to use biosolids and biosolids compost to increase the organic matter content of the gravel mine’s native soil. Starting in 1999, 930 wet tons of biosolids from Metro Vancouver and 3,918 wet tons of compost were delivered to the site, mixed with native soil at a volumetric ratio (approximately 16% compost, 16% biosolids, 66% native soil), applied to 11 hectares of gravel mine site, and seeded with grass. Figure 2 shows the transformation of the land from a gravel mine to parkland.

Figure 2: Gravel Mine After Reclamation Activities

To ensure that the biosolids and compost applications did not negatively impact the soil or aquifer after full-scale implementation, SYLVIS conducted extensive monitoring of nearby ground water wells, surface water of the lake in the park, and five domestic drinking water wells.

In addition to soil health benefits, research has shown that biosolids used to reclaim mine areas also provides carbon sequestration. SYLVIS conducted a study in 2011 (Trlica and Teshima, 2011) comparing carbon storage levels in biosolids-amended and conventionally reclaimed mine soils several years after closure. Evaluation of soil samples from sites up to 27 years after reclamation revealed that mines reclaimed with biosolids stored, on average, more carbon per hectare than conventionally reclaimed sites. Figure 3 summarizes the results showing the carbon sequestration benefits of biosolids application to mine sites compared to conventional reclaimed mine soils.

Figure 3: Mean organic carbon storage from reclaimed mine areas

This post highlights one example of a mine reclamation project where biosolids were utilized to transform a former gravel mine into regional park providing a wildlife habitat and other recreational opportunities. SYLVIS has many other mine reclamation project summaries posted on their website (see link below).

Sylvis website: https://sylvis.com/

Sylvis Research Papers: