The state Department of Ecology announced the new "low impact development" requirements on Wednesday, which will be phased in over the next few years in an attempt to minimize the fiscal impact on local governments.
The requirements will be in use by June 2015 in Seattle, Tacoma as well as King, Snohomish, Pierce and Clark counties. Other communities will see the requirements kick in a few years after that.
Rain gardens are planted depressions that allow rainwater runoff to be soaked into the ground. Pervious pavement also allows runoff to be filtered underground.
Rain runoff that's not absorbed tends to pick up pollutants as it makes its way into streams.
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