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PART I Page xi Permit No. CO-0000396 C. DEFINITIONS OF PERMS 7. 'Insteataaeous' meaalrroment is ^ single reading, observation, or measuremwt performed on site using existing monitoring facilities. S. 'Quarterly ~^°°~~~meat frequency' means samples may be collected at any time during the calendar quarter if e continual discharge occurs. If the discharge is intermittwt, then samples shall be collected during the period that discharge occurs. 9. 'Seven (7) day average' means the arithmetic mean of all samples collected in a seven (7) wnsecutive day period. (For fecal coliform, see the defuritioa for 'thirty day averege'.) Such seven ('1) day averages shall be calculated for all calendar weeks, which are defmad as begiming on stmday and eading on Saturday. If the calendar week overlaps two months (i.e. the Sunday is in one month and the Saturday in Ute following month), the seven (7) day average calculated for that calendar week shall be associated with the month that contains the Saturday. Samples may not be used far more than ooe (1) reporting period. l0. 'Thirty (30) day average' means the arithmetic mean of all samples collected during a thirty (30) consecutivo-day period. The permittee shall report the appropriate mean of all self-monitoring sample data collected during the calendar month on We Discharge Monitoring Reports. Samples shall not be used for more than one (1) reporting period. For fecal coliform bacteria concentrations, the thirty (30) day and seven (7) day averages shall be determined based on the geometric mean instead of the arithmetic mean. The geometric mean may be calculated using two difkrent methods. For the methods shown, a, b, c, d, etc. are individual sample results, and n is the total number of samples. ulw Method l: Geometric Mean = (e~b~'c~'d~...) '*' -means multiply Method 2: Geometric Mean = antilog ([log(e)+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 then 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 month are reported to be less than numeric values, they report 'less then' the largest of those numeric values on the monthly DMR. Otherwise, report the calculated value. For any individual analytical result of 'too numerous to count' (fN'fC), 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.), then the following procedures apply: i) A minimum of two samples shall be collected for colifotm analysis within the next sampling period. ii) if the samolin¢ freguencv 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 to 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 been collected. if the samolin¢ frequency is more frequent than monthly: Eliminate the result of TNTC from any further calculations, and ttse all the other results obtained within that month for reporting purposes. Attach a letter noting that a result of TNTC was obtained, and list all individual analytical results and corresponding sampling dates (or [hat month. INDIIP ~NAI