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2000-07-14_REVISION - M1977378
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2000-07-14_REVISION - M1977378
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Entry Properties
Last modified
3/30/2021 6:25:16 AM
Creation date
6/25/2012 11:43:51 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
M1977378
IBM Index Class Name
REVISION
Doc Date
7/14/2000
Doc Name
Mine Pool Info.
From
Sunnyside Gold Corp
To
DMG
Type & Sequence
TR14
Media Type
D
Archive
No
Tags
DRMS Re-OCR
Description:
Signifies Re-OCR Process Performed
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SGC's Technical Memorandum (9 June 1995) suggests a control limit <br />based on 95% percent of the samples being "in control" (item 3, <br />page 4). Given the sampling frequency, this is an appropriate <br />control limit. I agree with SGC's assertion that a one- sided test <br />should be used because the regulatory concern is that mine closure <br />does not increase the level of zinc in the Animas River. Items 4, <br />5, and 6, pages 4 and 5, however base the control limits on two - <br />sided probability or the 97.5% probability level for a one -sided <br />test. Given the proposed sampling frequency, I think the 95% <br />probability level (1.645 standard deviations) is more appropriate. <br />Most statistical process control methodologies include several <br />criteria applied simultaneously to determine whether or not a <br />process is out of control. These rules usually include 1) one or <br />more points outside the control limit; 2) several points outside a <br />warning limit, but still in control; and 3) a run of points that <br />plots on one side of the center line. The use of multiple criteria <br />suggested in this paragraph increases the chance that one or more <br />criterion will be exceeded, therefore a set of actions leading to <br />restoring water quality should follow the principle of graduated <br />response. <br />For example, an out of control data point should not result in an <br />enforcement action, but should lead to a series of actions that are <br />taken to determine if the point is due to chance, i. e. a false <br />alarm, or if their is an assignable cause for the out of control <br />point. An assignable cause conclusion should lead to further <br />positive steps specified in the Consent Decree as to what actions <br />will be taken. Steps in the graduated response should include 1) <br />increased monitoring, either a higher frequency or at more <br />locations or both; 2) identifying the cause for the new or <br />increased zinc load, and if attributable to closure of Sunnyside <br />Mine, development and implementation of a remediation plan; 3) <br />implementing additional mitigation projects; 4) change in the level <br />of treatment of Cement Creek; and 5) termination of the Consent <br />Decree if water quality cannot be maintained. The data collected <br />for the control chart will ultimately determine when release from <br />the permit will be accomplished. <br />Figure 1 shows simulated Shewart and EWMA control charts for the A- <br />72 data. The center line and control limits for both charts are <br />based on the flow adjusted mean concentration and standard <br />deviation of data collected at A -72 for the reference period (1991 <br />through the present). The EWMA chart uses a weighting factor of <br />0.2 which is somewhat analogous to a 5- period moving average. The <br />simulated charts merely show one of an infinite number of possible <br />outcomes. Both charts are based on monthly sampling for a 5 -year <br />period and assume no change in the mean or variability of the <br />historic zinc concentration. The upper warning limit (UWL) and the <br />upper control limit (UCL) are at 1 and 1.645 standard deviations <br />which correspond to the 85th and 95th percentiles, respectively. <br />
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