"NEW SECTION.  Sec. 2   A new section is added to chapter 90.58 RCW to read as follows:
     (1) New or amended master programs approved by the department on or after September 1, 2011, may include provisions authorizing:
     (a) Residential structures and appurtenant structures that were legally established and are used for a conforming use, but that do not meet standards for the following to be considered a conforming structure: Setbacks, buffers, or yards; area; bulk; height; or density; and
     (b) Redevelopment, expansion, change with the class of occupancy, or replacement of the residential structure if it is consistent with the master program, including requirements for no net loss of shoreline ecological functions.
     (2) For purposes of this section, "appurtenant structures" means garages, sheds, and other legally established structures. "Appurtenant structures" does not include bulkheads and other shoreline modifications or over-water structures.
     (3) Nothing in this section: (a) Restricts the ability of a master program to limit redevelopment, expansion, or replacement of over-water structures located in hazardous areas, such as floodplains and geologically hazardous areas; or (b) affects the application of other federal, state, or local government requirements to residential structures."