ITEMS FOR ADDITIONAL DISCUSSION: Summary of Interagency Working 

Comments on Draft Language under EO12866/13563 Interagency Review. 

Subject to Further Policy Review.

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Environmental Protection Agency (EPA): Proposed Rule 

Protection of Visibility: Amendments to Requirements for State Plans 

RIN 2060-AS55 

General Comments: 

9) Reviewer recommends providing additional information for when the guidance 

document is planned to go out related to this rulemaking and general timelines for the 

draft and final version of the guidance. Is it possible to align the draft guidance with the 

proposed rule or to have overlap within the comment periods? 

14) Reviewer does not believe that you need to make this distinction between haze and 

impairment; haze is a relatively uniform distribution of pollutants that affects visibility. 

Contributions to haze are both natural and anthropogenic. Impairment is the relative 

contribution of anthropogenic haze to total haze. When expressed as a change in 

deciview levels, “impairment” is defined as the difference between total haze and natural 

haze. 

17) Reviewer recommends clarifying the process for non-Class I states that have sources 

that affect downwind states with Class I areas. 

19) Reviewer recommends taking comment on specific time frames such 120 days, to 

consult the FLM prior to a public hearing that would be de facto enough time for FLM 

input. It is unclear what enough time would be for a state to provide an FLM. 

20) Reviewer recommends providing timeframes for how long the assessment by EPA on 

progress reports would take and what the procedures would be for the assessment. Also, 

reviewer recommends providing a negative informal consent that any modifications or 

additional steps by the state would not be required after a certain date after submittal of 

the progress report. 

Specific Comments: 

9) Page 50 – Reviewer recommends explaining the criteria that would be used to evaluate 

the proposed state methods [for selecting the 20 percent most impaired days] 

understanding that further guidance will provide additional information. 

21) Page 88, § 51.301 – Reviewer recommends revising the language to state: 

a. Haze Index Deciview index means a value, expressed in deciview (dv), for a day 

that is derived from calculated or measured light extinction, such that uniform 

increments of the index correspond to uniform incremental changes in perception 

across the entire range of conditions, from pristine to very obscured. The deciview 
ITEMS FOR ADDITIONAL DISCUSSION: Summary of Interagency Working 

Comments on Draft Language under EO12866/13563 Interagency Review. 

Subject to Further Policy Review.

2 | P a g e

haze index is calculated based on the following equation (for the purposes of 

calculating deciview haze index using IMPROVE data, the atmospheric light 

extinction coefficient must be calculated from aerosol measurements and an 

estimate of Rayleigh scattering): 

Deciview Haze index (dv) =10 lne (bext/10 Mm−1).

34) Page 109, § 51.308(i)(2) – Reviewer recommends revising the section as follows: 

a. The State must provide the Federal Land Manager with an opportunity for 

consultation, in person at a point early enough in the state’s technical and policy 

analyses of its long-term strategy emission reduction obligation and prior to 

development of reasonable progress goals planning the development of its longterm strategy so that information and recommendations provided by the Federal 

Land Manager can meaningfully inform the State’s development of the long-term 

strategy and at least 60 120 days prior to holding any public hearing or other public 

comment opportunity on an implementation plan (or plan revision) or progress 

report for regional haze required by this subpart. This consultation must include the 

opportunity for the affected Federal Land Managers to discuss their: