The 2011 Highway Runoff Manual is the guidance that WSDOT, engineering consultants, and many local agencies use to design stormwater systems for transportation projects. Together with WSDOT's Hydraulics Manual, (pdf 11.06 mb) the HRM provides tools for designing effective stormwater collection, conveyance, and treatment systems for highways, ferry terminals, park and ride lots, and other transportation-related facilities.
The Highway Runoff Manual represents years of extensive research, collaboration, and negotiation by an interdisciplinary technical team of water quality, stormwater, and erosion control specialists; designers; hydrologists; geotechnical and hydraulics engineers; landscape architects; and maintenance staff. The technical team also includes several county representatives and benefits from a close working relationship with Washington State Department of Ecology (Ecology) staff, with work also contributed by consultants and outside reviewers. The technical team recognized that it is inefficient, and in some instances ineffective, to try to emulate how local jurisdictions manage runoff from residential, commercial, and industrial land uses. Consequently, their approach to developing the HRM takes into consideration that WSDOT:
- Needs a statewide approach for managing stormwater that recognizes the differences in climate, soils, and land uses.
- Has limited control of pollutants entering its right of way (including pollutants generated from atmospheric deposition, vehicle operation, litter, organic debris, and surrounding land uses).
- Highway projects are linear in nature and, as such, are faced with practical limitations in terms of locating and maintaining stormwater treatment facilities within state-owned right of way.
- Lacks funding mechanisms (such as stormwater utility fees) and land use controls (zoning and land use ordinances) available to local governments.
- Must be accountable to taxpayers to provide cost-effective stormwater facilities.
The HRM receives periodic updates to enhance content clarity as well as reflect changes in the regulatory landscape, advancements in stormwater management, and improvements in design tools.
Comments and suggestions for improving the HRM should be e-mailed to:
email@example.com or mailed to:
Highway Runoff Manual
Attention: HRM Program Manager
PO Box 47329
Olympia, WA 98504-7329
2014 Highway Runoff Manul Revision
The Highway Runoff Manual (HRM) is an integral part of the WSDOT NPDES municipal stormwater permit (Permit). The Department of Ecology expects to reissue the Permit, in March 2014. WSDOT revised the HRM to maintain equivalency with the Department of Ecology’s Stormwater Management Manuals.
Two versions of the revised HRM appear below. The 2014 Draft HRM Version with Revision Marks represents a “clean copy” of the draft 2014 HRM which include sidebars and underlines to indicate changes; however, it does not show deleted sections. (Please note, Chapter 5 was updated on November 7th to include a link to CAVFS LID Calculator that was inadvertently left out during the revision process. The 2014 Draft HRM Version with Tracked Changes depicts all the tracked changes. Please download this version if you want to go back and compare the 2014 version to the 2011 version. Both versions are zip files that include all the manual’s chapters and appendices.
A file called Summary of Changes to the 2014 HRM that summarizes the changes to the 2014 manual in table format is also available to download.
LID feasibility checklist (xls, 45kb)
CAFVS LID Calculator (xlsx, 23kb)
MGSFlood modeling input
Basic and wet biofiltration swale design (xls, 2mb)
Continuous inflow biofiltration swale design (xls, 4mb)
Media filter drain (MFD) underdrain design (xlsx, 12kb)
Slotted pipe flow spreader design (xlsx, 1mb)
The major changes to the 2014 Draft HRM include:
- Adding language and flow charts to meet the reissued permit’s low impact development (LID) requirements
- Editing to enhance the manual’s use as a design manual
- Revising some best management practices (BMP) to reflect changes approved by Ecology since the last HRM revision
- Replacing Chapter 6 with a new manual called Temporary Erosion and Sediment Control Manual (TESCM). Chapter 6 now introduces the TESCM and provides a web link to this new standalone manual.
The public comment period for the NPDES permit and the HRM lasts until January 10, 2014.
WSDOT staff should submit written comments regarding the HRM to Mark Maurer at firstname.lastname@example.org by December 23, 2013 using the 2014 HRM Comment Form.
WSDOT staff should submit comments regarding the TESCM to Elsa Pond at email@example.com by December 23, 2013 using the TESCM Comment Form.
WSDOT staff should submit comments regarding other aspects of the permit to Larry Schaffner at firstname.lastname@example.org no later than December 23, 2013.
Non-WSDOT staff should submit comments directly to Ecology per the instructions provided at: http://www.ecy.wa.gov/programs/wq/stormwater/municipal/wsdot/2014permit.html
Post Publication Updates to the 2011 HRM
Below are the post publication updates for chapter 5 of the 2011 Highway Runoff Manual. There are two files, one with track changes as well as the final document.
Upon issuance of the WSDOT Municipal Stormwater Permit in February 2009, WSDOT and the Department of Ecology adopted an implementing agreement (pdf 309 KB) calling for WSDOT to apply the June 2008 version of the Highway Runoff Manual throughout Washington State.
Stormwater Retrofit Guidance for WSDOT Projects in the Puget Sound Basin
The February 2009 permit was appealed and the settlement directed WSDOT to retrofit existing pavement, if feasible and cost effective, on projects within the Puget Sound Basin that add more than 5,000 square feet of new impervious surface.
HRM Section 3-4.1 gives guidance on this stormwater retrofit requirement. The Retrofit Cost-Effectiveness and Feasibility (RCEF) document gives the designer detailed instructions on how to perform the analysis. The designer must use the guidelines contained in RCEF along with the information in HRM Section 3-4.1 to complete the analysis. Include the completed RCEF analysis in the project’s hydraulic report.
Training on the analysis methods used to design stormwater runoff treatment and flow control facilities has been incorporated into the HQ Hydraulics Section's curriculum. Training on guidance and procedures for temporary construction-related erosion and sediment control facilities has been incorporated into the Environmental Services' erosion and sediment control program curriculum. Training for applying other elements of the HRM is under development. All consultants who prepare Hydraulics Reports for WSDOT must have completed the 2008 Highway Runoff Manual training course. 2008 HRM training is required for WSDOT staff who write Hydraulics Reports.
To receive e-mails announcing updates, training opportunities, and improvements in design tools, please subscribe to the Stormwater Issues listserve.
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To receive announcements for updates to the HRM, please subscribe to the HRM Update listserve.
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Frequently Asked Questions (FAQs)
The HRM FAQs page answers a variety of questions about the Highway Runoff Manual.