Philadelphia and the U.S. Environmental Protection Agency signed an agreement in April that paves the way for $2 billion in green infrastructure investment over the next 25 years for controlling combined-sewer overflows, or CSOs, and managing stormwater more sustainably.

The U.S. Environmental Protection Agency on April 18 finalized standards under the Clean Air Act to reduce air pollution associated with oil and natural gas production through hydraulic fracturing.

The controversial Keystone XL oil pipeline has suffered a major setback, with President Obama's Jan. 18 announcement that the State Dept. denied a permit for the $7-billion project.