You think maintaining compliance with opacity standards is a challenge now – just wait. As anyone who has started a campfire knows, opacity (the density of the smoke) tends to be high when starting and ending fuel burning, as well as during adjustment of the fuel. Thus, the potential changes to the opacity exemptions may be of concern.

On June 12, 2015, U.S. EPA promulgated a regulation that required Maine to update the version of Chapter 101 in Maine’s EPA-approved State Implementation Plan (SIP). Specifically, EPA said that Maine DEP must amend Maine DEP’s Visible Emissions Regulation to eliminate startup and shutdown exemptions and eliminate exceptions (e.g., “except for three 6-minute block averages in a 3-hour period”). In response, Maine DEP provided a pre-rulemaking draft and solicited public input at a workshop on January 13, 2017. Maine DEP has asked that any written comments of the draft be submitted by January 27, 2017.

The more significant changes proposed in the draft of Chapter 101 are as follows:

  • Categorical opacity limits listed in Chapter 101 would apply based on the primary fuel being fired, instead of the primary fuel that a unit is licensed to utilize.
  • When firing primarily oil, the opacity limit would be 20%, except for two 6-minute block averages in a 3-hour period that cannot exceed 80%.
  • When firing primarily natural gas, the opacity limit would remain at 10%, however, the exception for one 6-minute block average in a 3-hour period would be eliminated.
  • When firing primarily biomass, the opacity standard would be reduced from 30% to 20% and the excepted two 6-minute blocks in a 3-hour period must meet 80% opacity.
  • Recovery boilers would stay at a 20% opacity limit. However, the 2% (quarterly) and 1% (four consecutive quarters) exemptions would be eliminated and replaced with an exception allowing one 6-minute block in a 3-hour period not to exceed 50% opacity.
  • General process sources not otherwise listed would be limited to 20% opacity with no exceptions.
  • Combined stacks would still be limited to 30% opacity, but the exception for three 6-minute blocks in a 3-hour period would be limited to 50% opacity, or a 2% quarterly exception during which all 6-minute blocks could not exceed 80% opacity.
  • Stationary internal combustion engines would still be limited to 20% opacity, but the exception for no more than two 6-minute block averages in a 3-hour period would be eliminated.
  • There would be a new opacity limit for boilers rated between 3 MMBtu/hr and 30 MMBtu/hr of 20% opacity, except for no more than two 6-minute block averages in a 3-hour period that could not exceed 50% opacity.
  • Language in Chapter 101 regarding the “old” 4-hour startup and shutdown exemption and the reference to the Department’s authority to establish exceptions for startups and shutdowns would be eliminated. This would be replaced with language stating that sources may apply to the DEP to amend their licenses to establish alternative emission limits for startups and shutdowns.

If you have concerns about how this regulation might affect your facility, you should consider submitting comments. The Department has indicated a desire to hear from sources regarding the potential impacts of the proposals on their operations.