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PART I Page xi Permit No. CO-0038024 DEFINITIONS OF TERMS 7. 'Iasmntaneous' measuremmt is a single reading, observation, or measurement performed on site using existing monitoring facilities. 8. 'Quarterly :.tasure~^--t frequency' means samples may be collected at any time during the calendar quarto if ^ continual discharge ocean. If the discharge is intermittent, then samples shall be collected during the period that discharge occurs. 9. 'Scum (~ day average' means the arithmetic mean of all samples collected in a scum (7) consecutive day period. (For fecal caliform, see the defmitioa for 'thirty day avenge'.) Such scum (7) day averages shall be calculated for all calendar wedu, which are defined u beginning oa suaday and ending on Saturday. If the calendar week overlaps two months (i.e. the Sunday is in one month and the Saturday is the following month), the scum (7) day avenge calculated for that calendar wcek shall be associated with the month that contains the Saturday. Samples may not ba used for more than one (1) tePorung Period. 10. 'Thirty (30) day avenge' means the arithmetic mean of all samples collected during a thirty (30) coasecrttive-0ay period. The petmittee 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 coon than one (1) reporting period. For fecal coliform bacteria concmtntiom, the thirty (30) day and scum (7) day avenges shall be determined based an the geometric mean 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. a.w eM thod 1: Geometric Mean = (a~b'c'd~.. J '"' -means multiply • eM t6ad 2: Geometric Meaa = aatilog ([log(a)+log(b)+log(c)+lag(d)+...]/n) Graphical methods. even though they mey also employ the use of logarithms. may introduce s;grtificaat error and may not be used. Ia calculating the geometric mean. for those individual sample results that an reported by the analytical hdtontory 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 the result is 'less then ~2', ttse a value of 1 in the calculations. If all individual analytical trstlts for the swath arc reported to be less than numeric values, then report 'less than' the largest of those numeric values oa the monthly DMR Otherwise, report the calculated value. For any individual analytical result of 'too numerous w count' (TNTC), that amlysis shall be considered to be invalid and another sample shall be promptly mllxted 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 ie requited, etc.), then the following procedures apply: i) A minimum of two samples shall be collected for coliform amlysis within the next sampling period. ii) If the semoliae freguencv is monthly or less ftmuent: For the period with the invalid sample results, leave the spaces on the corresponding DMR for reporting coliform results empty and attach to the DMR a letter noting that a result of TNTC was obtained for that period, and explain why soother sample for that period bad not bees collected. If the samolin¢ freeumcv is more freaumt than monthly Eliminate the result of TNTC from any further calculations, sad use all the other results obtained within that month for reporting Purposes. Attuh a letter noting that n result of TNTC was obtained, and list all individual analytical results and corresponding sampling dates for that month. •