The mining activities at the Britannia Mine left behind an environmental legacy that for decades left the local groundwater, creeks and nearby Howe Sound waters bereft of life. The problem was Acid Rock Drainage (ARD). ARD forms when water and oxygen react with metal sulphides such as pyrite to form sulphuric acid and dissolved metals. ARD occurs naturally, anywhere that metal sulphides are exposed to air and water, so the digging of the mine's tunnels allowed for vast quantities of ARD to form and then flow from the mine into the creeks and Howe Sound.

Thankfully, through a remediation campaign led by the BC Province, Britannia's ARD issue has been resolved. Since 2002, Golder Associates have spearheaded a cleanup of the local contaminated soils, and since 2005, a water treatment plant has been operated by EPCOR to treat all water coming from the mine.

For a more in depth look at Britannia's environmental story, check out The Facts About Britannia's Environment.

Acid Rock Drainage

ARD is a natural process where oxygen and water react with metal sulphides, to create sulphuric acid and dissolved metals.

Acid Rock Drainage (ARD) is a natural process that happens when metal sulphides are exposed to oxygen and water - air and rain. Bacteria (Thiobacillus ferrooxidans) also plays a big part in the process. The biggest ARD producer is pyrite (iron sulphide), though at Britannia, others include chalcopyrite (the copper ore), galena (lead ore) and sphalerite (zinc ore). A chemical reaction happens that produces sulphuric acid and dissolved metals, both of which pollute the local environment when they get into the groundwater and local water sources.

It only takes two pennies worth of copper dissolved in a swimming pool to make it toxic to marine life. The mine was producing the equivalent of 69 pennies worth of copper and 20,800 pop cans worth of vinegar every minute. Clearly something had to be done to resolve it.

History of the Problem

The size of the mine generated large amounts of ARD, but the environmental regulations of the day were minimal, meaning that little was done to stop the problem.

ARD has occurred here for as long as the sulphide minerals have been exposed at the surface of the ground. The digging of 210 km of tunnels in the mountain, and the fractured nature of the rock, created a much larger surface area for this chemical reaction. With high snow and rainfall and an open pit at the very top of the mine, you can imagine just how much water was entering the mine, becoming polluted, and then leaving the mine further down.

In the 1930's, the issue was known about, though little was understood about the environmental impacts. Since the 1930's, copper launders existed at the mine. This process helped slightly, but it was done for economic, not environmental reasons. The launders were long troughs containing iron scraps. Mine water was fed through these before being discharged. An iron-copper exchange happened; copper coated the iron pieces and dissolved, relatively non-toxic iron flowed with the water out of the troughs. The copper was then collected and sold. So it did help reduce the amount of copper entering Howe Sound, but only until the mine closed in 1974.

On closure, the owners Anaconda installed an outflow pipe that discharged the water 50 m below sea level. The water was not treated, but was taken away from the intertidal zone, the most vulnerable area for aquatic life. They also installed a mud/earth dam near the 2200 portal (reinstated in 2001). This stopped water from entering Britannia Creek, until the dam failed sometime in the 1980's/90's.

Water Treatment Process

Today, the mine water is captured and treated at the EPCOR Britannia Mine Water Treatment Plant before being discharged clean into Howe Sound. The acidity is neutralized and the metals are removed.

The mine's portals have been sealed to channel all the water down to a portal not far from the top of the Mill building. Here a concrete plug and outlet pipes control the exit of the water. It is fed to the water treatment plant, where it is cleaned before being discharged into Howe Sound.

The first step in the process is to neutralize the acidity. Lime slurry (lime and water mixture) is added to a tank containing the ARD. This raises the pH from 3.8 to 9.3; in other words, it goes from being acidic to being alkaline. When this happens, the metals, which have been dissolved in the ARD, naturally precipitate out to become metal particles. In the next tank, a man-made customized polymer is added which electrostatically attracts the metal particles. These heavy particles sink to the bottom of the tank and the clean water is removed from the top.

The metal sludge is removed, dewatered and twice yearly, taken up to the original Jane Basin mining pit. Here it helps to cap the pit, preventing some of the water from entering the mine. As the metal sludge is not in the form of metal sulphides, it won't form ARD in the future.

Each day, the facility removes 600 to 700 kg of metal sludge - all this is metal that is no longer being discharged into Howe Sound.

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