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22 RISK ASSESSMENT /MANAGEMENT relief and commonly include bogs and wetlands, while the plateau areas to the west are distinguished by a regular pattern of rounded peaks separated by moderate to steeply sloping valleys. The mine is located in the lowlands, while the mill and tailings disposal areas are located within the plateau. Geology. The predominant surficial material in the area site is glacial till; glaciofluvial deposits are common in lowland areas. Fluvial and colluvial deposits are found along most rivers and creeks. The ore deposit mineralization is gold and silver with trace amounts of mercury, arsenic, antimony and other metals as sulfides. Elevated mercury, antimony, and arsenic values (greater than 10, 80 and 600 per parts million, respectively) in waste rock occurs in one 35 meter stratigraphic sequence in the proposed pit. Seismicity. A major fault system lies approximately 65 kilometers west of the proposed mine site. It marks the contact between two major crustal plates. Approximately 10 large earthquakes (magnitude greater than seven) have occurred on this fault in recent times. Biological Resources. The river and creek drainages in the project area support Pacific salmon, as well as populations of anadromous and resident trout and char populations. One of the rivers is unique in supporting populations of all five species of Ocean salmon (sockeye, pin, chum, chinook, and coho), as well as anadromous rainbow (steelhead) and cutthroat trout. Vegetation is a mixed coniferous coastal forest, with bogs and wetlands. Deer and black bear are the major wildlife species. Water Duality. Surface waters are characterized as poorly- buffered, somewhat acidic, soft water with high concentration of organic matter, iron and manganese, and low levels of suspended sediments. Minimum values for pH and alkalinity are usually associated with low flows during the summer. The mean measured alkalinity of the study area streams range from 4.3 to 17.6 milligrams CaCo per liter; minimum 0.63, maximum 40.0. The low pH values in the study areas do not appear to be caused by the presence of acid generating minerals in the watershed, but are more probably the result of a combination of the poor buffering capacity and the presence of humic acids leached from decomposing coniferous forest litter. Groundwater quality results show moderately alkaline conditions ranging from 7.0 to 9.7 pH units. They show moderate alkalinities, typically on the order of 100 milligrams CaCo per liter with a range of 68 to 180. Total dissolved solids levels range from 154 to 2839 milligrams per liter. The local springs are fed mainly by very shallow circulating groundwater flow. These slightly acidic and poorly buffered spring waters are much more similar in chemistry to the local surface waters than to the deep groundwater. Population Centers. The town closest to the site is 16 kilometers to the north of the project area. Other population centers are at a larger distance. In summary the site - specific environmental characteristics selected for consideration in the qualitative risk assessment are: • key fishery resource, includes spawning and nursery habitats; ► high annual rainfall; ► stream hydrology has low potential for dilution of effluent; ► water quality and characteristics: low pH, alkalinity, hardness, and dissolved solids; flowing streams with alternating wetlands; - low temperatures during most of the year; ► high seismic hazard; and, organic debris from high ecosystem productivity. Potential impacts posed by the various components of the project include the effects of: ► ARD on aquatic ecosystems and fisheries and direct effects on water quality; ► heavy metals release from ARD, soils or rocks, including copper and possibly mercury; ► sediment releases to streams and drainages; ► breaches or releases of mill effluent, tailings and contaminated water from impoundments and dams; • spills or releases of reagents, fuel or cyanide during transportation, storage or use at the mill; ► nutrient loading of streams from mining or milling activities; ► direct physical activities on fisheries habitat, loss of spawning or rearing sites; and, ► flow changes in streams and subsequent effects on fisheries, contaminated waters entering the groundwater. A total of 36 failure scenarios were evaluated for this Example Project. Appendix A contains example risk assessments for two individual failure scenarios. Each of these risk assessments contain sufficient information to support the basis for a quantitative risk assessment. Hazard Assessment The project has been divided into three geographic areas: the mine; mill tailings; and transportation, storage and handling facilities. A stepwise review of the activities at each component throughout the project life identified hazards and potential release mechanisms associated with each component. Table 1 presents a systematical identification of the potential hazard for each component and the associated release mechanisms. Some hazards identified are not present in high concentrations or volumes and were not ' further investigated. The following hazards are considered for further development and application in the risk assessment: ► sediment; ► physical movement by slope failure (stockpiles, tailings); ► acid rock drainage (ARD); ► metals (copper as an indicator);