Opinion ID: 186114
Heading Depth: 2
Heading Rank: 3

Heading: Opacity-Based Emission Standard

Text: 45 During the copper smelting process, some HAP emissions evade the capture systems and are released into the atmosphere through roof-top vents spanning the length of the converter building or through exhaust fans. EPA addressed these emissions — the fugitive HAP emissions — by imposing a four percent opacity limit at building vents. Sierra Club objects that (1) opacity is not a surrogate for HAPs, and therefore EPA has failed to establish an emission standard for roof vents and exhaust fans, and (2) the opacity standard cannot be defended as a work practice or operational standard under 42 U.S.C. § 7412(h)(1), because EPA has failed to meet the statutory prerequisites for imposing such a standard in lieu of an emission standard. 46 EPA's decision to use an opacity-based standard for fugitive HAP emissions is reasonable. Sierra Club focuses on a portion of EPA's response to public comment on the opacity-based standard — we are using the opacity ... as an indicator of converter capture system performance, EPA Background Document, at 3-1 — to argue that EPA itself regarded the opacity limit as an operational standard, not an emission standard. Reading the entirety of the response, EPA's reasoning is clear: 47 Given that opacity is an indicator of the level of particulate matter emitted, designing and operating a copper converter capture system to minimize the visible emissions from the building will increase the amount of particulate matter captured and vented to a control device. Given that metal HAP emissions from copper converters behave as particulate matter, increasing the level of particulate matter emissions control will increase the level of metal HAP emissions control. 48 Id. at 3-2. Opacity measures PM and limiting PM reduces HAP emissions. In addition, limiting fugitive HAP emissions through opacity-based standards further controls HAP emissions by ensuring that the converter capture system is working well enough to make the PM standard meaningful — there is no sense focusing on the primary exhaust streams if most of the emissions go out the roof. See id. at 3-1. We have already accepted EPA's contention in another case, in response to an objection by Sierra Club, that opacity monitoring promotes good operation and maintenance, which in turn reasonably ensure compliance with the PM standard. National Lime, 233 F.3d at 635. We have no reason to question it here. 49 EPA established the opacity-based standard according to the approach mandated by statute, basing it on the average of the test data for the five best performing sources. Final Rule, 67 Fed. Reg. at 40,485. EPA's opacity-based standard is an emission standard that is accordingly both reasonable and lawful.