2018-10-22_REVISION - M2008078 (12)

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Appendix C Page 62 of 67 Permit No.:COG500000 16. "Good Engineering, Hydrologic and Pollution Control Practices"-methods, procedures,and practices that a)are based on basic scientific fact(s);b)reflect best industry practices and standards; c)are appropriate for the conditions and pollutant sources; and d)provide appropriate solutions to meet the associated permit requirements,including all effluent limitations. 17. "Grab"sample,is a single"dip and take"sample so as to be representative of the parameter being monitored. 18. "IC25"or"Inhibition Concentration"is a point estimate of the toxicant concentration that would cause a given percent reduction in a non-lethal biological measurement(e.g.growth or reproduction)calculated from a continuous model (i.e. interpolation method). IC25 is a point estimate of the toxic concentration that would cause a 25-percent reduction in a non- lethal biological measurement. 19. "Impaired Water"(or"Water Quality Impaired Water")—A water is impaired for purposes of this permit if it has been identified by a State or EPA pursuant to Section 303(d)of the Clean Water Act as not meeting applicable State water quality standards (these waters are called "water quality limited segments"under 40 CFR 30.2(j)). Impaired waters include both waters with approved or established TMDLs,and those for which a TMDL has not yet been approved or established. 20. "Inactive mining operations"—Regulation 61.3(2)(e)(iii)(C)identifies that"inactive mining operations"are mining sites that are not being actively mined, but which have an identifiable owner/operator; inactive mining sites do not include sites where mining claims are being maintained prior to disturbances associated with the extraction, beneficiation,or processing of mined materials, nor sites where minimal activities are undertaken for the sole purpose of maintaining a mining claim). This term includes the following types of facilities that have an identifiable owner/operator: • mineral mining and/or milling occurred in the past but is not covered by an active mining permit issued by DRMS; • operations are limited seasonally(i.e., intermittent operations),consistent with DRMS requirements for notification, only during the portion of the year when the facility is not active;or • operations cease for 180-days or more for reasons not associated with intermittent status,and still has reserves (consistent with temporary cessation status as defined by DRMS),only during the time period the facility is not active; or • exploration or extraction activities have ceased permanently. 21. "Industrial Activity"—for this permit means those activities identified by the SIC codes described in the applicability section of the permit. 22. "Industrial Stormwater"-stormwater runoff from industrial activity. 23. "In-situ" measurement is defined as a single reading,observation or measurement taken in the field at the point of discharge. 24. "Instantaneous" measurement is a single reading,observation,or measurement performed on site using existing monitoring facilities. 25. "LC50"or"Lethal Concentration"is the toxic or effluent concentration that would cause death in 50 percent of the test organisms over a specified period of time. 26. "Maximum Weekly Average Temperature(MWAT)"is defined in the Basic Standards and Methodologies for Surface Water 1002-31,as an implementation statistic that is calculated from field monitoring data. The MWAT is calculated as the largest mathematical mean of multiple,equally spaced,daily temperatures over a seven-day consecutive period,with a minimum of three data points spaced equally through the day. For lakes and reservoirs,the MWAT is assumed to be equivalent to the maximum WAT from at least three profiles distributed throughout the growing season(generally July-September). The MWAT is calculated by averaging all temperature data points collected during a calendar day,and then averaging the daily average temperatures for 7 consecutive days. This 7 day averaging period is a rolling average,i.e.on the 8`day,the MWAT will be the averages of the daily averages of days 2-8. The value to be reported on the DMR is the highest of all the rolling 7-day averages throughout the month. For those days that are at the end/beginning of the month,the data shall be reported for the month that contains 4 of the 7 days.