In my monthly column in The Legal Intelligencer/Pennsylvania Law Weekly, I examine two recent Pennsylvania Environmental Hearing Board appeals which address aggregation of air emission sources under the Clean Air Act and the Pennsylvania Air Pollution Control Act.  The cases, Group Against Smog and Pollution v. Department of Environmental Protection, EHB Docket No. 2011-065-R, and Clean Air Council v. Department of Environmental Protection, EHB Docket No. 2011-072-R, consider whether, and how, air emissions from natural gas wells, gathering systems and compressor stations should be aggregated.