DEP Proposes New Approach to Visible Emissions (Opacity) Regulation

The Maine Department of Environmental Protection (DEP) recently proposed extensive changes to its Visible Emissions Regulation (Chapter 101) that may impact a facility’s ability to remain in compliance. For decades, virtually all visible emissions (aka opacity) standards contained exemptions to account for sporadic, short periods of elevated opacity. For example, fuel-burning equipment firing No. 4, No. 5, or No. 6 fuel oil was subject to a 30% opacity standard except for no more than two 6-minute block averages in a 3-hour period. Boilers firing No. 2 oil have been subject to an opacity limit of 20% except for no more than one 6-minute block average in a 3-hour period. The DEP’s proposal would eliminate such exceptions.

The DEP has not, for the most part, proposed to change the opacity percentage limits. But its proposal to eliminate existing exemptions and, in lieu thereof, provide an exemption for periods of startup, shutdown, or malfunction is significant. As an illustration, the practice of soot blowing is not considered a period of startup, shutdown, or malfunction. If your boiler exceeds the opacity percentage limit during a 6-minute block average, there will no longer be an exemption available for that incident under DEP’s proposal. For boilers that must undertake periodic soot blowing as part of normal operations, this proposed new approach could prove problematic.

The DEP also is proposing to reduce the percent opacity limit for biomass-fired boilers from 30% to 20%. Additional proposed changes would affect sources that have multiple units emitting through a shared or common stack. For such common stacks, the opacity limit remains at 30% on a 6-minute block average. However, exceptions allowing 2% of 6-minute blocks to be up to 40% opacity on a quarterly basis, and 0.5% of all block averages to be above 40% opacity on a quarterly basis, would be eliminated. Instead, only those exceedances due to startup, shutdown, and malfunction would be allowed.

We recommend each facility closely review the proposal and determine the potential impacts on compliance with this regulation. Maine DEP is accepting comments on its proposed rulemaking until 5:00 pm on August 17, 2018.

If you have any questions about the potential impacts on your facility or need assistance preparing comments to DEP, please contact Brian Rayback (207.791.1188) or Lisa Gilbreath (207.791.1397).