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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division <br />Rationale - Page 7. Permit No. CO-0033367 <br /> <br />DISCUSSION: CCont.) <br />G. Active Mining <br />The only limitations which are applicable to 002 and 005 are those <br />indicated in Table 1. Because 002 and 005 are for underground mine <br />drainage, they are not eligible for the storm event exemption condition, <br />as is 003. <br />H. Flocculants <br />The permittee shall report all planned initial use of flocculanta or other <br />chemical treatment of discharge (excluding •chlorine) to the Division at <br />least 30 days prior to use. Material Safety Data Sheets for each chemical <br />shall also be submitted, as well as the intended dosage level. The <br />Division shall decide upon whether or not a permit amendment is needed in <br />order for this chemical(s) to be used, based upon consideration of the <br />potential impacts on the receiving waters. This notification applies to <br />the first use of each such chemical only. <br />I. Biomonitoring <br />Biomonitoring is not a requirement of this permit due to Division policy, <br />• which exempts amendments to permits as a reason for adding it. However, <br />the Division reserves the right to reopen the permit to include <br />biomonitoring, should Division policy or facility conditions change. <br />J. Change in Definition of Average Limitations <br />The definition of the 30 day average limitation has changed. In the past <br />it was necessary to have 3 samples in a 30 day period is order to <br />demonstrate compliance or noncompliance with a 30 day average limitation. <br />The new definition, which satisfies 40 CFR 122.2 and Section 10.1.0 of 5 <br />CCF 1002-3, represents an arithmetic mean of all samples collected Sn a 30 <br />day period. The arithmetic mean is calculated as the sum of all samples <br />measured during the month divided by the number of samples measured during <br />the month. The significance of this is that if only one sample is <br />collected during a month the results must satisfy the 30 day average <br />limitation or the permit is violated. If the initial result is high, the <br />permittee is encouraged to perform additional sampling in an effort to <br />lower the arithmetic mean, but the monthly average reported must be based <br />on all sampling results, and must utilize all additional data regardless <br />of the result. The preceding is similarly true for the 7 day average <br />limitations. <br />K. Reopener Clause <br />This permit may be reopened and modified, as discussed in Part II.B.S, if <br />there is a significant change in state or federal water quality <br />• regulations, a significant change in operation at the facility, or at the <br />request of the permittee. <br />