EVALUATION OF ARD FROM BRITANNIA MINE AND THE OPTIONS FOR LONG TERM REMEDIATION OF THE IMPACT ON HOWE SOUND BCAMD 3.31 This project was prepared for Ministry of Energy, Mines and Petroleum Resources B.C. Acid Mine Drainage Task Force By Stephen, Robertson and Kirsten (B.C.) Inc. November 1991 EVALUATION OF ARD FROM BRITANNIAMINE AND THE OPTIONS FOR LONG TERM REMEDIATION OF THE IMPACT ON HOWE SOUND Prepared for: Ministry of Energy, Mines and Petroleum Resources B.C. Acid Mine Drainage Task Force Room 105 - 525 Superior Street Victoria, B.C. WV lx4 . Prepared by: In associationwithz Stephen,Robertson and Kirsten (B.C.) Inc. Gormley ProcessEngineering 580 Homby Street #6l2 - l200 West Pender Street Vancouver, B.C. Vancouver, B.C. V6C 3B6 V6E 2S9 November 1991 This project was funded by the Province of British Columbia Sustainable Environment Fund. EVALUATION OF ACID MINE DRAINAGE (AMD) FROM BRJTANNIA MJ.NE AND THE OPTIONS FOR LONGTERM REMEDIATION OF THE IMPACT ON HOWE SOUND Prepared by ReclamationSection ResourceManagement Branch Ministry of Energy, Mines and Petroleum Resources The Britannia Mine is located at Britannia Beach, on the east shore of Howe Sound, approximately48 km north of Vancouver. Operated from 1905to 1963 by the Britannia Mining and Smelting Company Ltd., and from 1963 to 1974 by Anaconda Mining Company, in its prime the mine was one of the biggest copper producers in the British Empire. The mill/mine complex fmally shut down in 1974, and nowadaysis used as a museum. The area containing the mine workings and the mill is currently owned by Copper BeachEstates. The major environmental concem at Britannia Mine is with acid mine drainage, and associatedhigh copperand zinc levels emanatingfrom old adits and waste dumpsl. While dissolvedcopper concentrationsare an order of magnitudeless than they were during mine operation, they still have an impact on the invertebrate and fish in Howe Sound. This study was carried out to assistthe present owner in dealingwith this problem. Funding was granted by the SustainableEnvironment Fund (SEF), with managementprovided by the British Columbia Acid Mine Task Force. The objectivesof the study were to review ail available information, critique the present systemof control, and to recommend posstble long-term solutionsto reduce or eliminate acid mine drainage. Mining at Britannia was carried out in seven ore bodies, all located east of Britannia Beach, in the ridge between Britannia and Furry Creeks. Over the seventy years of operation, 80 km of underground workings - the sourceof 95% of the or6 - and five open 1 Waste Dump: Barren or submarginalrock or ore which has been mined but is not of suffrcient value to warrant treatment, and is therefore removed ahead of the milling process. pits were created. Accessto the underground workings was primarily provided through portals at 200, 1550, and 2100 ft above sea level. Surface pit excavationocctirred 5 km inland, largely between 3000 and 4500 ft above sea level. In addition to portals and oben pits, surface disturbance associatedwith mining included three small waste dumps, the road network, a series of dams on Britannia Creek, and subsidenceassociated with the underground workings. Ore generated by mining was processedin milling facilities at Britannia Beach. During operation, approximately45 million tonnes of ore were processed,predominantly copper, but lesser amounts of silver, zinc, and gold were also recovered. Tailingss,the main waste product from the mih, were either dischargedinto ‘Howe Sound or used underground as backfilk Concems regarding the fate of the tailings were addressedin a recent study of Howe Sound, paid for in part by the Ministry in conjunction with the British Columbia Acid Mine Drainage Task Force. Acid generation results from the oxidation of sulphide minerals contained in rock exposed to air and water. Water draining through areas of sulphide oxidation cari transport the reaction products. While this phenomenon is often referred to as acid mine drainage, it is not confined to lands disturbed by mining; for example,natural Springsare often acidic in the vicinity of outcrops of sulphide-bearingrock. The principal ingredients in the AMD processare reactive sulphide mine&, oxygen and water. The oxidation reactions are-often acceleratedby microbiological activity. Not all mining operations that expose sulphide-bearingrock result in acid mine drainage. For example,AMD will not occur if the sulphide minerais are non-reactiveor if the rock is not leached. If alkaline material is availablein the rock waste, pH changesmay be buffered by neutralizing reactions as the drainagepasses through the waste. The main impact of acid mine drainage is caused by the dissolution of heavy metals. ‘Qpically, mined rock contains abnormally high concentrations of a number of heavy metals that will be releasedby weathering reactions occurring concurrently with sulphur oxidation. In the usual pH range of soils and water, heavy metals releasedby weathering normally precipitate in immobile compounds. However, under highly acidic conditions, the heavymetals dissolveand are entrained in runoff and seepage,and cari causea detrimental impact on water quality in the receiving environment. 2 Or-e: A mineral, or mineral aggregate,containing precious or useful metals or metalloids, and which occurs in such quant@, grade, and chemical combination as to make extraction commerciallyprofitable. 3 Tailings: The portion of the ore which after grinding and washing is regarded as too poor to be treated further; used especiallyof the debris from stamp mills or other ore-dressingmachinery, as distinguishedfrom material (concentrates)that is to be smelted. The geological strata of the ore bodies mined at Britannia consist of massive sulphides, widely disseminated or concentrated in stringers and along bedding planes. Prior to mining, sulphide oxidation will have been limited to a thin surface layer, a few small outcrops, and areas of landslide debris. Exposure, cracking and communition of the sulphide bedrock in the underground workings, pits, and rock dumps have significantly increased the amount of sulphide oxidation, which in tum increasesthe rates of acid generation and metal dissolution. The open pits and gloryholescollect drainage, tünnelling rainwater through the extensiveunderground workings, flushing out the oxidation products. Under the precepts of sustainabledevelopment, mining is regarded as a temporary land use. This objective is enforced by current mine reclamation legislation requiring that land and water resourcesbe reclaimed to a level of productivity not less than that which existed previously, and that water released from a minesite meet long-term water quality standards. Acid mine drainage is a major impediment to successfulreclamation for mining operations throughout the world. In British Columbia, AMD presently occursat six operating mines. Four other metal mines and two coal mines are consideredpotentially acid generating, as are severalproposed mines. Under the British Columbia,Mine Development Assessment Process,ail mines with a potential to generate acid mine drainage must develop plans to prevent it. TO enable the British Columbia mining industty to comply with the present comprehensive reclamation requirements, the Ministry of Energy, Mines and Petroleum Resources is participating in a program of researchaimed at developingcost-effective solutions to major environmentalproblems. A major part of this program focuseson acid mine drainage. As part of this, the Ministry coordinates and provides funding for the British Columbia Acid Mine Drainage Task Force, and strongly participates in activities of the national acid mine drainage program (Mine Environmental Neutral Drainage Program - MEND). In 1992, the proposed researchprogram for the British Columbia Acid Mine Drainage Task Force is $1.5 million, with funding shared by industry and the Provincial and Federal Govemments. The problems of acid mine drainage will not easily be solved. However, work carried out during the last five years has done much to enhanceour knowledgeand ability to predict, prevent, control, and monitor AMD. The cooperativeefforts betweenour Ministry and the British Columbia mining industry are widely regardedwith envy by the rest of Canada,and we are recognizedby many as world leaders in acid mine drainage technology. As a result, the British Columbia consulting industry is currently selling its services abroad, an important @n-off of the ongoing researchactivity. At present, six of the mine sites abandoned prior to the enactment of reclamation legislation are acid generating. Fortunately, many of these older sites are small underground operations and the impact is manageable. The administration and control of acid mine drainage tiom historic mine sites is shared between Environment Canada and two British Columbia Ministries: Environment, Lands and Parks and Energy, Mines and Petroleum Resources. Our Ministry has assumed responsibility for reclamation of several closed mine sites, including the Mount Washington Mine on Vancouver Island. Work carried out at Mount Washington since 1988 has included the testing of various caver types and spoil configurations, and developing monitoring technology. Results to date have included the development of a cost effective asphalt emulsion/geotextile caver designed to seal the surface, thereby redueing the removal of oxidation products. The program of AMD researchat Britannia Beachis being done in concert with that at