The dispersion of heavy metals in the vicinity of Britannia Mine, British Columbia, Canada

Abstract

Britannia Mine in British Columbia, Canada, is a major source of copper and other heavy metal pollutants, which enter the sea at Howe Sound. This investigation aims to determine whether there is sufficient Cd, Cu, Pb, and Zn, in the terrestrial environment surrounding the mine to suggest that dispersion and subsequent bioaccumulation has occurred in the past and continues. Samples of spoil, vegetation, and water were collected in January 2003 from areas at sea level and up to an altitude of 790 m. The samples of soil and vegetation were digested with aqua regia. The subsequent extracts and water samples were analyzed using flame atomic absorption spectrophotometry. The target metal concentrations were found to be much higher on the hillside spoil tips than on the seashore where the ore concentrators had formerly been located. The dispersion of heavy metals into the surrounding biosphere is discussed and further investigations into dispersion and partitioning within organisms including humans are suggested.

Introduction

Britannia Mine is situated above the settlement of Britannia Beach, some 50 km north of Vancouver on Highway 99, also known as the Sea to Sky Highway. The nearest large town is Squamish, 11 km north of the site.

The mine at Britannia Beach operated from 1898 until 1974 and in the 1920s was said to be the largest copper mine in the British Commonwealth (URS, 2002). Between 1905 and 1974 the mine produced 47.8 million tonnes of ore (Mills, 2003). Secondary products were Zn, Ag, Au, Cd, and Pb (URS, 2002)

The site is currently considered to be one of the worst sources of water pollution in North America (Warkentin, 2000). The mine covers an area of some 28 km² and consists of a series of tunnels and some open-cast mining. The mine originally commenced on a hill at an elevation of 1400 m above sea level and now extends below sea level. Five open pits were also created near the summit of the hill. A series of portals exit onto the hillside at different altitudes and aspects, but all have waste rock dumps (spoil tips) nearby, eventually washing down into a series of creeks. When the mine was abandoned, acid mine drainage (AMD) became a major problem, issuing from several portals and a submerged drain extending into Howe Sound. Britannia Creek, which collected AMD from Jane Creek and Mineral Creek, was also a source of discharge into Howe Sound. A concrete plug is reported to have closed off AMD from the 2200 level portal (Britannia Mine Remediation Project, 2002) and AMD from the mine is being discharged via the submerged drain. Dr. John Meech of the UBC Department of Mining estimates that at least 1 tonne of copper is discharged into the Sound each day (personal communication, 2002).

The provincial government has obtained reparations from various previous owners of the mine to carry out remedial work and currently employs several consultants who are determining the extent of the remediation required to make the site safe. They have identified many areas of environmental concern (AEC), the majority of which center on the Fan Area, where the old concentrators were sited. This area now supports some 300 individuals who live in either old mine housing or trailers. The site owners when the samples were collected were Copper Beach Estates, however currently, responsibility for the area appears to have been assumed by the Provincial Government. It is clearly in their interest to have the site declared safe to allow further commercial development of the land.

Fig. 1 illustrates the extent of the site. The old town site (Mt. Sheer) has been leveled and the area has now been invaded by Alnus spp. with some early growth of Picea sitchensis, the usual successional sequence in western Canada after clear cutting of lumber. The prevailing winds are either northerly or southerly up and down Howe Sound and have little effect in the valleys on either side of the mine. The area is classified as a coastal wet climatic zone with high levels of precipitation most of the year but with very warm summers. Precipitation in winter regularly falls as snow above about 300 m.

Much work has been carried out examining the effect of AMD into the Sound and the effects of some 40,000 tonnes of tailings (from the concentrators) that were discharged from 1902 to 1974 into Howe Sound (Hagen, 2001). Such examinations range from underwater surveys from diving vessels (Levings and McDaniel, 1973) to the effects of the local sea water on transplanted rainbow trout (Barry et al., 2000) and estimates of benthic organism reduction around the Sound (Ellis and Hoover, 1990). There has been no assessment of the dispersion, accumulation, and partitioning of copper and associated metals into the surrounding biosphere. Local residents have expressed concern over health issues for many years, although such concerns have been refuted by the various consultants employed by the provincial government. Hagen in 2001, noted that groundwater and upland influences will need to be studied. It should be noted that a pilot water-treatment plant has been installed in the local primary school to allay concerns regarding the health of children in the area (Golder Associates, 2002a).