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- caps, covers or diversions to minimize infiltration of rain water or snowmelt, or <br />• limited holding times, i.e. limit the time available for precipitation to contact the ore or waste rock. <br />For the Division to allow waste rock to remain unprotected and still assure that impacts to the hydrologic <br />balance have been minimized, the operator should show that pollutants released from either ore or waste <br />rock would be diluted sufficiently prior to enterin <br />classified stream. Because selenium concentration ~xceed both at some use point or prior to meeting a <br />the lazgest percentage factor, selenium is used to derive the diluti~ values nece~ssaacryWO demo d ides by <br />minimization of impacts to the hydrologic balance (see Table 1). For waste rock, it must be demonstrated <br />that pollutants will be diluted at Least 46 times before reaching a stream (see lead, Table 1). <br />I understand that the operator at the JD Mines already has constructed a small runoff retention features <br />below the waste piles to establish some protection for <br />runoff anticipated from some design storm: I would re~mmend a~least the I00 yearstotmn If w ter in <br />this pond is meant to evaporate rather than leach slowl into <br />Y groundwater, there should be measures in <br />place to prevent evaporate residues in the pond from becoming blowing dust. Land application of the <br />fluids maybe acceptable provided the permit is revised appropriately. <br />There is precedent in the Division allowing dilution of contaminants with fresh water or groundwater in <br />order to meet groundwater numeric protection levels. If dilution is selected as a means of meeting <br />groundwater numeric protection levels, the operator should construct a model showing what dilution rates <br />can be expected if rain or snow melt drives pollutants from the rock piles into local groundwater. <br />Numeric protection levels may also need to be developed if high ambient levels are to be considered in <br />the dilution calculations. <br />The Division should cazefully evaluate the proximity of ore and waste rock piles to surface and <br />groundwater resources. This will require site-specific examinations that consider proximaty to streams, <br />proximity to groundwater; saze of ore and waste rock facilities, duration of their exposure to weathering, <br />and reclamation and closure techniques. <br />Discussion; The Synthetic Precipitation Leach Procedure (EPA Method SW-846) requires adding 2 liters <br />of siightIy acidified deionized water (initial pH = 4,2 using a mixture of H SO <br />nitric acid) [o l Op g of powdered sample, and agitating the mixture end-over-end at 3020 <br />Tt is reco a (sulfuric and <br />gnized that the SPLP is an aggressive test that tends to overstate the amount ofpollutants that~s. <br />may derive from a rock mass under natural conditions, unless their natural state is to be crushed as in the <br />SPLP. Test results for this study aze considered maxima that might be expected under worst-case <br />conditions. Although the test is chemically more aggressive than natural conditions might allow, the tests <br />do indicate what pazameters are likely to appear under natural conditions. <br />on these parameters primarily to minimize the release of contaminants fromOtheirtoperatio Sash to focus <br />Overall, I believe the facilities need to examine their ore and waste handling procedures in context of <br />potential exposure to ground and surface water. <br />Ce: Bruce Humphries <br />Cazl Mount <br />Steve Shuey <br />