Stormwater Policy Objective: Restore Hydrologic Processes and Water Quality in Areas Where Development Has Caused Harm

When significant projects are undertaken on sites which have lost most of their natural hydrologic functions, efforts should be made to restore those functions to the greatest extent possible.  A “significant” project is one in which a pre-defined threshold is crossed, for example the construction costs represent 50% of the current value of the property.  These projects should be required to meet the standards for new construction set in Section B above unless this is impossible due to site constraints.

 This approach is necessary to meet the Puget Sound Partnership healthy Sound by 2020 goal.  This goal could be achieved by placing retrofit requirements on all redevelopment as well as through publicly financed retrofits.  Prioritize projects through basin planning program and establish major new sources of revenue to accomplish this goal.

Much existing impervious area is unnecessary and should be removed. For example, many side streets can be narrowed to allow for rain gardens. Most existing impervious area could be disconnected from surface water by repaving, using pervious materials or bordering with bioretention facilities or both. 

The state should develop a program of prescriptions and incentives to reduce existing total and effective impervious area.

Pilot projects like City of Seattle “SEA Street Project” provide a useful model.  Existing roads should be retrofitted, where safe and possible, to remove impervious surfaces, remove curb and gutter systems, and install rain gardens to capture runoff.  Piloting of these techniques has shown that they can be conducted in such a way as to accommodate emergency vehicles, facilitate vehicle parking, and overcome other potential “barriers” to their use.

Click on the links below for further discussions of individual objectives:

Preserve Natural Hydrological Processes on a Landscape or Watershed Level

Prevent Impacts from New Development on a Site-Specific Scale

Source Control

Mitigate Fully for Any Loss of Hydrologic Functions which Result from New Development

After Maximizing Prevention and Source Control Strategies, Use Best Management Practices to Reduce Impacts Until Restoration is Possible

Overarching Mechanisms to Achieve Objectives

To comment or for more information, contact Bruce Wishart, (360) 754-9177.