A timeline of the legal battles to get Homer City Generating Station to clean up its pollution:
--June 2008: EPA files violation notice alleging that beginning in 1988 Homer City made modifications without installing pollution controls.
--July 2008: U.S. court strikes down rule adopted by Bush administration to control pollution from power plants that contributes to unhealthy air downwind.
--December 2008: The court directs EPA to work on new rule, while leaving the Bush-era rule in place.
--May 2010: Homer City receives second violation notice from EPA, which says power plant failed to follow federal law and obtain pollution permit before making modifications in the 1990s that increased pollution.
--July 2010: New York and Pennsylvania file 60-day notice to sue Homer City over uncontrolled pollution. EPA under Obama administration proposes new rule to reduce downwind pollution.
--November 2010: EPA issues third notice of violation to Homer City for failing to install pollution controls as required by Clean Air Act.
--January 2011: EPA files suit against Homer City for two decades of Clean Air Act violations. New York and Pennsylvania also file lawsuit, as well as local citizens.
--February 2011: New Jersey joins lawsuit against Homer City saying plant operated "without limiting emissions of sulfur dioxide."
--April 2011: Homer City's operator files to dismiss both EPA and local citizen cases.
--July 2011: EPA finalizes rule to reduce sulfur dioxide and nitrogen oxides from power plants that contribute to air pollution downwind.
--August 2011: Homer City operator files petition for review of and motion to stay EPA rule.
--September 2011: States and other power producers also start filing lawsuits challenging EPA over downwind pollution rule. Courts consolidate cases under EME Homer City Generation vs. EPA.
--October 2011: Homer City plant files for permit in Pennsylvania to install scrubbers on its two uncontrolled units. Federal district judge dismisses lawsuits brought by EPA, states and local citizens.
--April 2012: Pennsylvania approves plans by Homer City to install scrubbers on uncontrolled units.
--May 2012: Sierra Club appeals state permit, saying it approved pollution quantities that would violate standards for sulfur dioxide.
--August 2012: U.S. Court of Appeals vacates Obama administration's downwind pollution rule. Says rule crafted under Bush will remain in effect.
--December 2012: Sierra Club settles with Homer City's owner over permit conditions for new scrubbers, requiring plant to verify it will meet emissions limits.
--April 2014: Supreme Court reverses Court of Appeals decision, reviving Obama's approach to curtailing downwind pollution from power plants.
Sources: AP research
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