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Appendix B Page 50 of 56 Permit No.: CO0032115 APPENDIX B - Definitions 1. "Acute Toxicity" - The acute toxicity limitation is exceeded if the LC50 is at any effluent concentration less than or equal to the IWC indicated in this permit. 2. "Antidegradation limits" - See "Two (2) - Year Rolling Average". 3. "Applicable water quality criterion (AWQC)" is the quantitation target level or goal. The AWQC may be one of the following: Where an effluent limit has been established, i. The AWQC is the effluent limit. Where an effluent limit has not been established, the AWQC may be i. An applicable technology based effluent limit (TBEL); ii. Half of a water quality standard; iii. Half of a water quality standard as assessed in the receiving water, or potential WQBEL; or Half of a potential antidegradation based effluent limitation, which can be an antidegradation based average concentration or a potential non -impact limit. 4. 'Best Management Practices (BMPs)" - schedules of activities, practices (and prohibitions of practices), structures, vegetation, maintenance procedures, and other management practices to prevent or reduce the discharge of pollutants to state waters. BMPs also include treatment requirements, operating procedures, and practices to control plant site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage. See 5 CCR 1002-61.2(9). 5. "Chronic toxicity", which includes lethality and growth or reproduction, occurs when the NOEC and IC25 are at an effluent concentration less than the IWC indicated in this permit. 6. "Composite" sample is a minimum of four (4) grab samples collected at equally spaced two (2) hour intervals and proportioned according to flow. For a SBR type treatment system, a composite sample is defined as sampling equal aliquots during the beginning, middle and end of a decant period, for two consecutive periods during a day (if possible). 7. "Continuous" measurement, is a measurement obtained from an automatic recording device which continually measures the effluent for the parameter in question, or that provides measurements at specified intervals. 8. "Control Measure" refers to any BMP or other method (including effluent limitations) used to prevent or reduce the discharge of pollutants to waters of the state. 9. "Daily Maximum limitation" for all parameters (except temperature, pH and dissolved oxygen) means the limitation for this parameter shall be applied as an average of all samples collected in one calendar day. For these parameters the DMR shall include the highest of the daily averages. For pH and dissolved oxygen, this means an instantaneous maximum (and/or instantaneous minimum) value. The instantaneous value is defined as the analytical result of any individual sample. For pH and dissolved oxygen, DMRs shall include the maximum (and/or minimum) of all instantaneous values within the calendar month. Any value beyond the noted daily maximum limitation for the indicated parameter shall be considered a violation of this permit. 10. "Daily Maximum Temperature (DM)" is defined in the Basic Standards and Methodologies for Surface Water 1002- 31, as the highest two-hour average water temperature recorded during a given 24-hour period. This will be determined using a rolling 2 -hour maximum temperature. If data is collected every 15 minutes, a 2 hour maximum can be determined on every data point after the initial 2 hours of collection. Note that the time periods that overlap days (Wednesday night to Thursday morning) do not matter as the reported value on the DMR is the greatest of all the 2 -hour averages. This would continue throughout the course of a calendar day. The highest of these 2 hour averages over a month would be reported on the DMR as the daily maximum temperature. At the end/beginning of a month, the collected data should be used for the month that contains the greatest number of minutes in the 2 -hour maximum.