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General Minimal Discharge Peru Rationale • Permit No. COGti00000 Page 13 V. TERMS AND CONDIITONS OF PERMIT B. Water Ouality Standard Based Effluent Limitations 2. Fecal Coliform Bacteria : (cont.) For fecal coliform bacteria concentrations, the rhirry (30) day and seven (~ day averages shall be determined as explained in LD.lI. and LD.10. of the permit, 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 rs the total number of samples. Method l: Geometric Mean = (a•b•c•d•...)r'^'~ "•' -means mulliply Method 2: Geometric Mean = anti[og ([log(a)+log(b)+log(c)+log(d)+...J/n ) • Graphical methods, even though they may also employ the use of logarithms, may introduce significant error and may not 6e used. In calculating the geometric mean, for those indivrdual sample resulu that are reported by the analytical laboratory to be "less than' a mtmeric value, the numeric value shall be used in the calcularions unless the result is' "less than 2.2". If the result is 'less than 2.2 ", use a value of I in the calculations. If all individual analytical results for the month are reported to be less than numeric values, thm report 'less than' the largest of those maneric values on the monthly DMR. Otherwise, report the calculated value. Ste the individual ctrrificatian jot the actual limit the facility will be required to meet. 3. Temoerature Maximum temperatures shall be 20 °C (68 °F) for waters classified as Class 1 Cold Water Biota, and 30 °C (86 °F), for Class 1 Watm Water Biota. Class 2 Waters shall be determined by the Division on a case by case basis. 4. Other Water Quality Standard Based Parameters: pli, and Iron are also regulated by the Water Quality Standards. C. Regulations for E/flutm Limitations: The 'Regulations for Effluent Limitations' (Ref. B), apply to the conventional pollutants. For this permit, the limitations for TSS, BODY mrd Oil and Grease are based on this regulation. •