Highway Runoff Manual
The Highway Runoff Manual (HRM) provides guidance to direct the planning and design of stormwater management facilities for existing and new Washington State highways, rest areas, park-and-ride lots, ferry terminals, and highway maintenance facilities throughout the state. The HRM establishes minimum requirements and provides uniform technical guidance.
Revision History
M 31-16.05 April 2019
Supplement February 2016
M 31-16.04 April 2014
M 31-16.03 November 2011
M 31-16.02 May 2010
June 2008
M 31-16.01 March 2007
2006 October
2006 May
2004 March
1995 February
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