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C. DEFINITIONS OF TERMS . <br />• <br /> <br />PART I <br />Page 10 <br />Permit No. CO-0044776 <br />9. "Thirty day average" means, except for fecal coliform bacteria, the azithmetic mean of all samples collected during <br />a thirty consecutive-day period. For fecal colifotm bacteria, it is the geometric mean of all samples collected in a <br />thirty day period. The permittee shall report the appropriate mean of all self-monitoring sample data collected <br />during the calendaz month on the Dischazge Monitoring Reports. Samples shall not be used for more than one <br />reporting period. <br />10. "Visual" observation is observing the discharge to check for the presence of a visible sheen or floating oil. <br />I1. "Water Quality Control Division" or "Division" means the state Water Quality Control Division as established in 25- <br />8-101 et al.) <br />12. For fecal coliform bacteria concentrations, the thirty day and seven day averages shall be determined as explained in <br />definitions * and * above, respectively, except that the geometric mean shall be used instead of the arithmetic mean. <br />The geometric mean tray be calculated using two different methods. For the methods shown, a, b, c, d, etc. aze <br />individual sample results, and n is the total number of samples. <br />Method l: <br />oiw <br />Geometric Mean = (a*b*c*d*...) "*" -means multiply <br />Graphical methods, even though they may also employ the use of logarithms, may introduce significant error and <br />may not be used. <br />Geometric Mean = antilog ([log(a)+log(b)+log(c)+log(d)+...]/n ) <br />In calculating the geometric mean, for those individual sample results that aze reported by the analytical laboratory <br />to be "less than" a numeric value, the numeric value shall be used in the calculations unless the result is "less than <br />2.2". If the result is "less than 2.2", use a value of 1 in the calculations. If all individual analytical results for the <br />month aze reported to be less than numeric values, then report "less than" the lazgest of those numeric values on the <br />monthly bMR. Otherwise, report the calculated value. <br />For any individual analytical result of "too numerous to count" (TNTC), that analysis shall be considered to be <br />invalid and another sample shall be promptly collected for analysis. If another sample cannot be collected within the <br />same sampling period for which the invalid sample was collected (during the same month if monthly sampling is <br />required, during the same week if weekly sampling is required, etc.), then the following procedures apply: <br />i) A minimum of two samples shall be collected for coliform analysis within [he next sampling period. <br />ii) If the samoling frequency is month).v or less fre uq ent: For the period with the invalid sample results, leave the <br />spaces on the corresponding DMR for reporting coliform results empty and attach to the DMR a letter noting <br />that a result of TNTC was obtained for that period, and explain why another sample for that period had no[ been <br />collected. <br />Amendment No. 1 Issued ~~'l~~'~' ' ~ ` ' ' Effective a~~ n ~ ~~~~ <br />