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Based on measurements of stream flow at reference point A-72 from 1991-1995, <br /> flow conditions at this point on the Animas consist of three classes: <br /> Low Flow (stream flow < 100 cubic feet per second) <br /> Intermediate Flow (100 cfs < stream flow < 300 cfs) <br /> High Flow(stream > 300 cfs) <br /> Each of these classes of flow conditions represents a physical response to the <br /> complex factors that may govern interactions between meteoric water and the <br /> geology. It is appropriate to evaluate water quality separately for each of the three <br /> classes. <br /> A-3 Method for Evaluating Water Quality with Respect to Reference Conditions Dunng the <br /> Project Period <br /> (a) Each month during the project period, SGC will collect a water-quality sample at Station <br /> A72. Analyses shall be conducted according to test procedures approved under 40 CFR <br /> Part 136, unless.other test procedures have been approved by the Division. SGC will <br /> obtain the stream-flow datum that applies to the relevant sampling event from the USGS <br /> data collection system. In the event that the stream gage at A-72 is frozen and/or <br /> inoperable yet a water sample is obtained, flow may be estimated. <br /> (b) SGC will report the flow value and the dissolved zinc value in a written submittal to <br /> WQCD. The submittal will be presented together with the next monthly Discharge <br /> Monitoring Report that is due to WQCD following receipt by SGC of the laboratory <br /> report for the dissolved zinc value. Records of monitoring information shall include: <br /> I. The date, exact place, and time of sampling or measurements; <br /> 2. The individual(s) who performed the sampling or measurements; <br /> 3 The dates the analyses were performed; <br /> 4 The individual(s) who performed the analyses; <br /> 5. The analytical techniques or methods used; and <br /> 6. The results of such analyses. <br /> (c) In addition to reporting the data, SGC will calculate and report an analysis of the data in <br /> the following form: <br /> Each month, SGC will calculate an index value representing relative number of <br /> standard deviations of the observed value of dissolved Zn from the mean value of <br /> dissolved Zn for the appropriate flow class in the reference water-quality set. The <br /> index number is calculated as: <br /> 12312-1 _„?Nd 2.a <br />