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PART I Page 15 Pernut No. CO-0038776 C. DEFINITIONS OF TERMS S. 'Grab' sample, is a single 'dip and take' sample so as to be representative of the parameter being monitored. 6. 'In-sin' measurement is defined as a single reading, observation or measurement taken in the field at the point of discharge. 7. "Instantaneous" measurement is a single reading, observation, or measurement performed on site using existing monitoring facilities. 8. "Quarterly measurement frequency' means samples may be collected at any time during the calendar quarter if a continual discharge occurs. [f the discharge is intermittent, them samples shall be collected during the period that discharge occurs. 9. "Seven (7) day average' means, with the exception of fecal coliform bacteria, the arithmetic mean of all samples collected in a seven (7) consecutive day period. For fecal coliform bacteria, it is the geometric mean of all samples taken in a seven (7) consecutive day period. Such seven (7) day averages shall be calculated for all calendar weeks, which are defined as beginning on Sunday and ending on Saturday. If the calendar week overlaps two months (i.e. the Sunday is in one month end the Saturday in the 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 for more than one (1) reporting period. 10. "Thirty (30) day average" means, except for fecal coliform bacteria, the arithmetic mean of all samples collected Burin" a thirty (30) consecutive-day period. For fecal coliform bacteria, it is the geometric mean of all samples collected in a thirty (30) day period. The permittee shall report the appropriate mean o(all self-monitoring sample data collected during the calendar month on the Discharge Monitoring Reports. Samples shall not be used for more than one (1) reporting period. I I . "Total residual chlorine" monitoring shall be required only if chlorine or other halogens are used at the facility and may be in the effluent stream. 12. "Visual" observation is observing the discharge to check for the presence of a visible sheen or Floating oil. 13. "Water Quality Control Division' or "Division" means the state Water Quality Control Division as established in 25-8- 101 et al. 14. For fecal coliform bacteria concentrations, the thirty (30) day and seven (7) day averages shall be determined as explained in definitions 9. and 10. 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, h, c, d, etc. are individual sample results, and n is the total number of samples. Method 1: t t /oI Geometric Mean = (a*b*c*d*...) "*" -means multiply Method 2: Geometric Mean = anlilog ([log(a)+log(b)+log(c)+log(d)+...]/n) Graphical methods, even though they may also employ the use of logarithms, may introduce significant eror and may not be used. INI)nl' a/9/93