PWD's Watersheds blog closes out the year with a list of 11 green missions accomplished in 2011, from innovative stormwater management projects and stream restorations to groundbreaking policy agreements and energy-generating solar arrays.

In April, the City of Philadelphia unveiled its first solar photovoltaic system (above), located at PWD's Southeast Water Pollution Control Plant. The 250-kilowatt solar array consists of more than 1,000 panels covering 60,000 square feet, and its electricity will help power the energy-intensive task of water treatment. In October, the Mayor's Office of Sustainability reported that the solar array had already generated enough electricity to power 2.7 houses for a year.