Document 6brXgMOoKBqz2Jg8jgabOgep1

tunnel, the stack lids arc opened and natural thermal buoyancy draft up the height of the stack restores the negative pressure. Additionally in case of loss of power, the stack lids arc opened by passive counterweights. In any case, the oven's negative pressure is maintained by passive lid opening and passive draft and does not require active measures. The negative pressure keeps the volatile organic compounds (VOCs) inside the oven and protects nearby personnel from fire and chemical exposure. Further, the negative pressure continues to draw in air to fully combust the VOCs and protects the environment from IIAP release and protects the downstream equipment from potential gas build up to explosive concentration levels. The key operating principle to the Bypass Vent Stack is the passive draft. If any HAP control equipment is installed on the Bypass Vent Stack, then the pressure drop associated with the control device will interfere with the passive draft and necessitate installation of a booster flue gas fan which then negates the passive safety purpose of the Bypass Vent Stack. The mass rate emission of HAP from a Bypass Vent Stack can be reduced by improved up-time of the downstream systems (HRSGs and flue gas ciesulfurization system (FGD)), but the concentration of HAP in the stream cannot be reduced in a vent stack flue gas. Bypass Stacks are used only when emissions cannot be vented through the Main Stacks. Therefore, the only appropriate limit on a Bypass Vent Stack is a work practice standard on upstream HRSGs and 12GD, which EPA did not consider. More generally, as described in Section I.B.4, EPA must reconsider whether work practice standards or surrogacy determinations are more appropriate for emissions of unregulated IIAP from Bypass Vent Stacks. Work practice standards and surrogate emission limits were raised by EPA in the Final Rule, which prevented SunCokc from commenting on this point during the public comment period. EPA should reevaluate and revise these MACT floor limits, including addressing the issues described in this section. Establishing appropriate MACT floor emission limits is of central relevance to the rulcmaking. 7. If LPA does not revise the final MACT.floor emission limits, it should offer a site-specific alternative standard consistent with its determination that no controls are required. As described in the sections above, there is data demonstrating that the new MACT floor emission limits cannot be met with existing controls, which is the foundation for EPA's rulcmaking. If EPA will not revise the final MACT floor emission limits (by using all appropriate data, distinguishing between different sources with different operations and emissions, and evaluating the appropriateness of work practice versus surrogacy determinations versus numeric emission limits), EPA should take the protective steps of allowing regulated entities to apply for an alternative limit if the new MACT floor emission limit cannot be met with existing controls. An alternative limit was allowed in the Surface Coating of Metal Furniture MACK at 40 C.F.R. 63.4890(b), and a suitable model could be developed for FINR emissions sources. In the alternative, EPA must reconsider whether the limited number of sources, limited data, differences in operations, variability of coal, and other factors, warrant revising the new MACT floor limits upwards to ensure that the limits can be met with existing controls. - 13 - Sierra Club FOIA 2025-EPA-04883 ED_018388_00000109-00073 SC_EVERSPLIT0005747