2000-01-31_HYDROLOGY - M1977378 (2)

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December Monthly/4"' Quarter Report Page 4 Evaluation of the normalized data: The index value of +0.83 for December, 1999 indicates that the dissolved zinc concentration at the reference point A-72 was significantly higher than the mean value of the reference data for the intermediate flow class. In comparison to the December 2, 1998 sample result, the concentration is lower(519 ug/l verses 583 ug/1) but the flow was higher (179 cfs verses 95 cfs) and in a different flow class. The 12 period moving average of index values rose to+0.79 from +0.76. This value is above the+0.577 benchmark value in the Consent Decree requiring a meeting to discuss monitoring results at the discretion of CDPHE. Although October, November and December's monitoring results are significantly above the reference data set and caused a rise in the 12 month running average, the underlying reason for the average being high is the May 6, 1999 sample result which contributes a N(i) value of+4.26 to the average which will influence the running average until it is no longer a factor. Please contact me if CDPHE would like to arrange a meeting to discuss monitoring results. If you have any questions on this report, please contact me. I certify under penalty of law that I have personally examined and am Sincerely, familiar with the information submitted herein: and based on my inquiry ofthose individuals individuals immediately responsible Larry Perino for obtaining the information, I believe Reclamation Manager the submitted information is true, accurate and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment. See 15 U.S.C. Section 1001 and 33 U.S.C. Section 1319 cc: EPA—Melanie Pallman EPA Region 8 (ENF-T) DMG—Wally Erickson Allen Sorenson LP/lp