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PART I Page No. 10 Permit No. CO-0044776 C. DEFINITIONS OF TERMS "Seven day average" means, with the exception of fecal coliform bacteria, the arithmetic mean of all samples collected in a seven consecutive day period. For fecal coliform bacteria, it is the geometric mean of all samples taken in a seven consecutive day period. Such seven day averages shall be calculated for all calendar weeks, which are defined as beginning on Sunday and ending on Samrday. If [he calendar week overlaps two months (i.e. the Sunday is in one month and the Saturday in the following month), the seven day average calculated for [ha[ calendar week shall be associated with the month that contains the Samrday. Samples may not be used for more than one reporting period. (Not applicable to fecal coliform determinations.) 8. "Thirty day average" means, except for fecal coliform bacteria, the arithmetic mean of all samples collected during a thirty consecutive-day period. For fecal coliform bacteria, i[ is [he geometric mean of all samples collected in a thirty day period. The permittee shall report the appropriate mean of all self-monitoring sample data collected during the calendar month on the Discharge Monitoring Reports. Samples shall not be used for more than one reporting period. 9. "Visual" observation is observing the discharge to check for the presence of a visible sheen or floating oil. 10. "Water Quality Convol Division" or "Division" means the state Water Quality Control Division as established in 25- 8-101 et al.) 11. For fecal coliform bacteria concentrations, the thirty day and seven day averages shall be determined as explained i^ definitions * and * above, respectively, except that the geometric mean shall be used instead of the arithmetic mean. The geometric mean may be calculated using two different methods. For the methods shown, a, b, c, d, etc. are individual sample results, and n is the total number of samples. Method l: ui~t ' Geometric Mean = (a*b*c*d*...) "*" -means multiply Method 2: Geometric Mean = antilog ([log(a)+log(b)+log(c)+log(d)+...]/n ) Graphical methods, even though they may also employ the use of logarithms, may introduce significant error and may not be used. In calculating the geometric mean, for those individual sample results that are reported by the analytical laboratory to be "less than" a numeric value, the numeric value shall be used in the calculations unless the result is "less than 2.2". If [he result is "less than 2.2", use a value of 1 in the calculations. If all individual analytical results for the month are reported to be less than numeric values, then repott "less than" the largest of [hose numeric values on dte monthly DMR. Otherwise, report the calculated value. For any individual analytical result of "too numerous to count" (TNTC), that analysis shall be considered to be invalid and another sample shall be promptly collected for analysis. If another sample cannot be collected within the same sampling period for which the invalid sample was collected (during the same month if monthly sampling is required, during the same week if weekly sampling is required, etc.), [hen the following procedures apply: i) A minimum of two samples shall be collected for coliform analysis within the next sampling period. ii) If the sampling frequency is monthly or less frequent For the period with the invalid sample results, leave the spaces on the corresponding DMR for reporting coliform results empty and attach [o the DMR a letter noting that a result of TNTC was obtained for that period, and explain why another sample for that period had not bee^ collected.