Stormwater retrofits are a diverse group of practices that provide pollution reduction from existing development that is either currently untreated or is inadequately treated by an existing stormwater practice.  Retrofits work by temporarily capturing polluted runoff, reducing flow and improving water quality treatment through physical and biological processes.  Examples of retrofits include wet ponds, swales, permeable pavement, and bioretention.  The Chesapeake Stormwater Network provides a variety of resources on urban stormwater retrofits to help state and local government staff and other stormwater professionals fulfill their responsibility of implementing the green infrastructure and urban restoration practices needed to comply with the Bay TMDL and MS4 permits.  Resources include the Chesapeake Bay Program Approved Expert Panel Report on Stormwater Retrofits, a webcast, and an easily digestable Fact Sheet.