Comment submitted by Eladio M. Knipping, Ph.D., Naresh Kumar, Ph.D., Stephanie L. Shaw, Ph.D., Electric Power Research Institute (EPRI)

November 9, 2009 U.S. Environmental Protection Agency Office of Environmental Information (OEI) Docket Mail Code: 2822T 1200 Pennsylvania Avenue, NW Washington, DC 20460 Re: Particulate Matter Urban-Focused Visibility Assessment, External Review Draft, Docket ID number EPA-HQ-OAR-2007-0492 Submitted electronically The Electric Power Research Institute is pleased to provide the attached comments on the External Review Draft of the Particulate Matter Urban-Focused Visibility Assessment. The Electric Power Research Institute, Inc. (EPRI) conducts research and development relating to the generation, delivery and use of electricity for the benefit of the public. An independent, nonprofit 501(c)(3)organization, EPRI brings together its scientists and engineers as well as experts from academia and industry to help address challenges in electricity, including reliability, efficiency, health, safety and the environment. EPRI also provides technology, policy and economic analyses to drive long-range research and development planning, and supports research in emerging technologies. EPRI supports a robust program on air quality issues including research on visibility and regional haze, and our research results are published in the peer-reviewed literature. Sincerely, Naresh Kumar, Ph.D. Senior Program Manager Air Quality Research Area Attachments