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1 • 0 <br />QUALITATIVE ENVIRONMENTAL RISK ASSESSMENT FOR MINE DEVELOPMENT 31 <br />II water management system, including the <br />treatment plant. <br />e. Magnitude of release <br />Small under normal operating condition and <br />II quick detection, <br />Large if flood, then water is diluted and <br />pH is not a concern. <br />f. Duration of release <br />Very short to days, dependent on site or <br />release and seasonal flow rates, lack of <br />detection or maintenance. <br />g. Pathways <br />Overland to drainages or directly into <br />wetland, creeks: eventually to river. <br />II Very little neutralization potential for <br />acidity or dilution in small creeks and <br />wetlands at low flow, with low complexing <br />potential of metals by high organic <br />content in natural waters. Water <br />treatment plants add considerable hardness <br />II to water reducing metal toxicity. River <br />has high flow rate and adequate dilution <br />for most releases. <br />h. System at risk <br />Aquatic ecosystems, fishery resources, <br />11 spawning and nursery areas in nearby <br />creeks and wetlands. Forest vegetation <br />effects are transient and low. <br />i. Exposure Description and Qualitative <br />Assessment <br />II Due to the low release potential of <br />untreated water and the dilution by the <br />receiving streams, the pH of the streams <br />as a result of a release is expected to be <br />in the range of 3.8 -6.4. Based on Table 2 <br />II the exposure to the aquatic ecosystem will <br />be very low to low. <br />Consequence Assessment <br />j. Consequence Description and Qualitative <br />Assessment <br />II A very low release and exposure of short <br />duration of ARD will result in slight <br />effects on growth or diversity ( <5%), <br />therefore based on Table 3, the <br />consequences are very low. <br />II Risk Characterization <br />k. Risk Description and Qualitative <br />Characterization <br />Very low probability of release and <br />II significant effect if the control and <br />treatment systems are operating as <br />designed. There is very low to low <br />exposure leading to very low consequences, <br />therefore the risk is very low (row 2, <br />II Table 4). <br />Proiect Specific Considerations <br />1. Management /Control Systems in Final Design <br />Water collection, segregation and <br />I treatment before release; liming of mine <br />waste rock to neutralize acid generation; <br />degradation of rock types for disposal <br />into stockpiles with treatments for <br />controlling ARD. Capacity for water <br />storage during periods of malfunction, or <br />il high rainfall. <br />m. Mitigation /Compensation and Contingency <br />Cleanup, restoration of water quality and <br />restocking of streams. <br />n. Recommendations <br />II Maintenance and good control procedures <br />are necessary to reduce the probability of <br />a release that will cause any significant <br />consequences. <br />