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Many simulations can be run, however I selected one to represent a <br />somewhat "worst" outcome so that graduated response criteria can be <br />evaluated. Because the EWMA chart is more appropriate for the <br />monitoring frequency proposed for the Animas, more typical control <br />limits (2 to 2.75 standard deviations) may be more applicable. <br />If a single point plots "out of control," on the Shewart chart SGC <br />should immediately begin an investigation to determine the cause. <br />This may include resampling at A -72, sampling at A -68, C -48, or M- <br />34, or other suitable quantitative investigation to determine which <br />stream caused the of the out of control point. If an assignable <br />cause, related to mine closure, is identified SGC should develop <br />and implement a preplanned contingency program to correct the <br />problem. <br />If two out of three points plot above the upper limit, and the <br />search for an assignable cause indicates that high zinc <br />concentration in Cement Creek is the reason, the level of treatment <br />of Cement Creek should increase or treatment at the American Tunnel <br />resumed. <br />Three consecutive points above the UCL should result in immediate <br />treatment of the American Tunnel or termination of the Consent <br />Decree. <br />If three out of four points plot above the one standard deviation <br />warning limit, effluent limits for Cement Creek should be tightened <br />and /or the "B" list of projects should be implemented. (On average <br />1.8 samples are expected to exceed the warning limit in one year <br />based on monthly sampling). <br />If eight consecutive points plot above the "center line," on the <br />Shewart chart (12 points on the EWMA chart) the "B" list of <br />projects should be implemented. <br />The control chart should also be used to measure progress toward <br />release from the discharge permit. After the mine pool has <br />physically stabilized, the "A" list of projects implemented, and a <br />ser%es of eight consecutive points plot below the "center line," on <br />the Shewart chart (twelve points on the EWMA chart) treatment of <br />Cement Creek should be terminated. <br />Eight consecutive points below the center line, following cessation <br />of treatment of Cement Creek should lead to application for permit <br />release. <br />The final criterion, release from the permit, should require that <br />the mean zinc concentration has not increased over the 1991 to 1995 <br />reference period. The final test should be based on the <br />statistical "null hypothesis" that the flow adjusted mean zinc <br />concentration at A -72 for the defined period, i. e. 18 months, <br />