Back in the 1930's, the issue was already a concern, but little was understood about the impact on the environment. Copper launders existed at the mine which helped slightly, but it was done for economic, not environmental, reasons. These launders were long troughs containing iron scraps. Mine water was fed through the troughs before being discharged. An iron-copper exchange meant the iron pieces became coated in copper, while relatively non-toxic iron dissolved and 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 was closed in 1974.
On closure, mine owners Anaconda installed an outflow pipe that discharged the water 50 metres below sea level. The water was not treated, but was taken away from the intertidal zone, the most vulnerable area for aquatic life. Anaconda also installed a mud/earth dam near the 2200 portal (reinstated in 2001). As a result, water was stopped from entering Britannia Creek, until the dam failed sometime in the 1980's/90's.