By December 31, 2016, Burien is required to adopt a new stormwater design manual that is equivalent with the 2012 Dept of Ecology Stormwater Management Manual for Western Washington. Staff is proposing to adopt the 2016 King County Surface Water Design Manual this fall.
When adopted, the new manual will become effective on January 1, 2017, and will apply to all new development and redevelopment projects submitting applications for permits after that date. Vesting into the 2009 manual will be allowed for projects that have submitted complete permit applications prior to December 31, 2016.
The most significant change to the new King County manual is the addition of Low Impact Development (LID) BMPs (called Flow Control BMPs in the manual), which will be required for nearly all development projects within the City. These BMPs include facilities such as bioretention (AKA rain gardens), permeable pavements, dispersion, and onsite infiltration.
More information on the new King County manual is available here:
2016 King County Surface Water Design Manual
Also, the Summary of Changes from the 2009 manual to the current one is available here:
2016 Summary of Changes