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COLORADO DEPARTi6fENT OF PUBLIC HEALTH AND E~WIRONMENT, Water Quality Control Division Rationale -Page 14, Permit No. CO-0045161 a/ !f a visible sheen is noted, a grab sample shall be collected and ana[y'zed for oil and grease. The results are to be reported on the DMR under parameter 03582. Table VI-~ -Monitoring Requirements for Outfa7ls OOlb, 004b, 007b, 008b, 009b, OIOb Parameter tlleas¢rementFrequency Sample Type ~. Flow, MGD Instmtutneous or Continuous Total Suspended Solids, mg/P Grab Total Recoverable Iron, mg/P ' (:rnh Potential discharges from these outfalls shall be sampled in the oit for TS'S and TR Fe to confirm compliance prior to every dischar¢e to the respective sedimentation ponds. Additiormlly, because of the time lag between sample collection and analysis and the time pumping would commence, t§ere is na certainty that the discharge quality is the same as the quality of the prior" sample. Until such time as the permitree can demonstrate to the Division's satisfaction that the water discharged from these points is the .came or better quality as that sampled prior to pumping, it will be necessary to sample rice discharge also. At roar time, discharge flow shall also be measured. This is not expected to be a burdensome requiremem in light of the infrequency of discharge of pit water. The results of the samples prior to discharge and those during discharge shall 6e reponed on the appropriate Discharge Monitoring Reports (DMR). An example of how ro report these results follows. Assume one discharge occurred from a "b" poim during a calendar quarter. The dis=barge may last far more than one day, this is not important for this example. However, the flow is continuous from commencement to end. A sample was collected and analyzed prior to discharge. A second sample was collected and analyzed roughly in the middle of the discharge event. The two TSS and the two total recoverable iron results shall be reported in this manner: for the 30.day average value for the DMR, the average of the two samples shall be reponed; for the daily maximum value, the higher of rite two results shall be reported. If pumping occurred on two separate occasions during the quarter and duri~ the same calendar month. till four results would be averaged and the average reponed as the 30.day average value on the DMR, the highest of the four results would be reported art the DMR. If two discharge episodes occur during one calendar quarter, but on separate months the prior" and "during" results for one episode would be averaged and the prior" and "during" results for the other episode would be averaged. The higher of the two averages would be reported as the 30-day average value on the DMR. The highest of all four values would 6e reported as the daily maximum value ors the DMR. If the permittee sampled the pit water prior to discharge and found it did not meet effluent limitations, so discharge did not occur, these results would nor be reported ar all and the oermittee would report "no discharge" for the outfall, assuming a discharge did not occur later in the quaver. If a discharge occurs later in the quarter, it will be treated as a single episode. The permiaee will be required to report "minimum" results on the DMR as well as "30.day average" and "daily maximum" so that the Divrsion can compare the prior" and "during" results easily. If additional questions come up at a later date regarding monitoring and reporting, the permittee can contact the Division for guidance. 2. Additional Monitoring: Because of the potential for discharge of poflutants from fuel and other vehicle sources from the vehicle wash operations through outfall 0026, the outfall from the Washbay Pond to the Work Area Pond, from which discharge occurs to Taylor Creek, the permiaee will be required to perform athree-rime analy ' for BEIX (the combination of benzene, ethylbenzene, toluene and xylene). Zhree samples are being required because the quality of such flows is variable, dependent on specific vehicle cleaning operations. One sample would not demonstrate the overall discharge quality variability. It is believed that three samples are Iikefy to provide an adequate demonstration, however, if three samples do nor give a full picture' of the discharge quality, additional samples may be required. Grab samples shall be collected at oulfall 002b, prior ro entering the Wark Area Pond, once each consecutive discharge episode from autfall 0026 until three samples have been collected. regardless of whether discharge occurs at the time from the Work Area Pond (outfall 002a -the discharge ro Taylor Creek). The permiaee shall submit the results of each sample set within 45 days after the sample dattr.