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.. <br />It will be very difficult to determine the actual buffering <br />capacity of the system due to the fracture permeability in the area <br />and our inability to easily determine what the actual contribution <br />to the Carlton flow from the waste rock is. If the transit time is <br />fast, such as through fracture flow, acid neutralizing capacity of <br />the host rock beneath the waste rock piles and pits will be less <br />than if transit time is slow. The HCI report estimates the travel <br />time is 4 months. However, if the flow time is rapid, the state <br />might be able to take the risk of the system failing because <br />response could be quick (and we should know about failure before <br />mining is over). If transit time is slow, the operator needs to <br />really prove that neutralization will occur. This might be done by <br />determining the origin of the Carlton tunnel water and by <br />quantifying the acid generation from the waste rock accurately. If <br />there is any doubt, the operator should either bond for a waste <br />rock cap, or neutralize the rock in place, as it is placed in the <br />storage areas. <br />2. Failure to Measure or Adequately Estimate Metal Content of <br />Carlton Discharge if Mixed with Acid Mine Drainage. <br />HCI did not calculate the possible <br />because they did not have sufficient <br />Humidity Cell Tests indicate that Zn <br />earlier note on which standards <br />weathering. Thus, whether Zn will e~ <br />is not known or even calculated. <br />III. OBSERVATIONS <br />Groundwater Geochemistry <br />Zn content of the Carlton <br />data. However, some of the <br />in excess of standards (see <br />were used) resulted from <br />Geed water quality standards <br />1. The HCI (1993) report indicates that the information available <br />regarding the Zn were insufficient to support geochemical <br />modeling. Zn' and other metals data are not included in the <br />model calculations for the Carlton Tunnel discharge. <br />2. Some pH model results fall below surface water standards (i.e. <br /><6.5). <br />3. The amount of acid produced from weathering of waste rock <br />depends on the surface area of the exposed rock grains: that <br />is, the surface area in three dimensions. As grain size <br />decreases, due to blasting, the "rock:water ratio" will <br />increase. That is, the rock flowing through blasted rock will <br />come in contact with more rock than the same water passing <br />through undisturbed permeable rock. Furthermore, the rote of <br />infiltration will increase, because of the increased <br />permeability. <br />HCI calculated acid production using 2-dimensional model. By <br />assuming - "conservatively" they said - that 10~ of the waste <br />rock would produce acid, they calculated resultant pH values <br />