The owner or operator shall observe the exhaust stack of each bypass or waste heat stacks once each week that exhaust is emitted through each stack continuously for more than an hour. The observation shall be made when exhaust is being emitted through the bypass or waste heat stack to determine if opacity, as a 6-minute average measured according to EPA Method 9 in appendix A-4 to 40 CFR part 60, exceeds 20 percent opacity. The owner or operator shall record the results of each observation. If a bypass event does not occur during a week or does not exceed one hour in duration, then no measurement is required for that week. If exhaust is emitted through any bypass or waste heat stack continuously for more than an hour during a week and no opacity measurement has been performed, the owner or operator shall record in the operating record the reason why conditions did not permit an opacity observation. If opacity greater than 20 percent opacity is observed during any weekly measurement, the owner or operator must:

(a) Take corrective action to reduce the emissions contributing to the opacity;

(b) Record the cause of opacity exceeding 20 percent and the corrective action taken; and

(c) Report opacity exceedances in any HNR HRSG bypass or HNR waste heat stacks in the quarterly semiannual compliance report required by § 63.7341.