Clean Water Services is proposing an update to the Design & Construction Standards, which will result in revisions to stormwater requirements to address the effects of hydromodification. In order to comply with the Watershed-Based permit, CWS is required to implement the updated development standards by April 22, 2019. In order to meet this requirement, a hydromodification “Base Strategy” has been proposed. This Base Strategy builds on the existing Design and Construction Standards and addresses the management of runoff volume. CWS is also actively developing more detailed Sub-Basin Specific Strategies to identify region-specific stormwater management approaches based on analysis of local stream and watershed conditions.
We encourage partners and members of the public to participate and stay informed. Sign up to get updates direct to your email. For additional background information check out this Fact Sheet (PDF, 2MB), updated October 25, 2018.
CWS is proposing a variety of stormwater management approaches that can be used at different scales to address the effects of hydromodification including stream enhancement, Low Impact Development Approaches (LIDA) and detention. The combination of approaches used would be based on landscape setting, historic and anticipated development patterns, project size, and stream condition.
A draft Base Strategy and Methodology (PDF, 1.6MB) document was created as a proposal and released January 4, 2019. It demonstrates how applicants can determine what approaches to addressing hydromodification impacts are expected to apply to a development site The Base Strategy utilizes the Hydromodification Planning Tool Web Map to identify key conditions that factor into determining the preferred approach for a particular development site. The methodology document also discusses tools and methods for designing different approaches.
This Base Strategy builds on the existing Design and Construction Standards and addresses the management of runoff volume. A document was created for determining which approaches are expected to apply under the Base Strategy and what tools are available for applicants. CWS is also actively developing more detailed Sub-Basin Specific Strategies to identify region-specific stormwater management approaches based on analysis of local stream and watershed conditions. Examples of Sub-Basin Specific Strategies are those currently available in the North Bethany development area in an unincorporated part of the County north of Beaverton and River Terrace in Tigard.
Since the release of the Base Strategy and Methodology on January 4, there have been several updates and additions, including:
CWS encourages interested stakeholders to review the following documents:
Submit comments to DnCUpdate@cleanwaterservices.org. Initial feedback on this topic is requested by January 23, 2019, though comments are welcome at any time.
On November 27, 2018 the Clean Water Services Board of Directors adopted an Implementation Policy (PDF, 60KB) for upcoming revisions to the Design and Construction Standards. The Implementation Policy outlines the effectiveness dates that will apply for the storm and surface water management portions of the upcoming standards.
Clean Water Services works with our community and partners to provide cost-effective and environmentally sensitive management of water resources for the Tualatin River Watershed. Part of that work is to provide Design & Construction Standards for sanitary sewer and surface water management that are periodically revised. The update process is necessary to incorporate changes in the watershed-based permit, and to reflect new technologies, approaches and development patterns.
This update process will:
These updates will be developed with stakeholder input and proposed for Board adoption in spring 2019.
CWS anticipates that the new Design and Construction Standards will take effect on April 22, 2019, except as otherwise determined by the Implementation Policy (PDF, 60KB) adopted by CWS Board of Directors on November 27, 2018. Under the Implementation Policy the following development and construction permit applications will be reviewed using the current Runoff Treatment and Control Standards adopted by RO 17-5:
The new Standards in effect at the time a development or construction permit application is made to CWS will apply to all projects which do not meet the explicit criteria listed above. The effectiveness dates above will only apply to the storm and surface water management portions of the new Standards and all projects are required to comply with all other aspects of the new Standards in effect at the time application is made for development, construction and building permits.
District staff held a kickoff meeting at the Hillsboro Civic Center on August 8, 2017. View the slides (PDF, 3.3MB) from this presentation to learn more.
When rain falls on traditional parking lots, sidewalks or driveways, it flows across the surface to the nearest storm drain, and immediately to the nearest stream or river. After all, the drainage system was designed to concentrate surface water flows and efficiently send them downstream.
Nearly every time it rains, urban streams rise rapidly, flowing faster and faster. This “flashiness” cuts away stream banks and disrupts the physical and biological systems that support fish and other aquatic organisms. Preventing stream flashiness is an important strategy to protect and restore our urban streams and wetland systems.
Learn more about hydromodification, and find some techniques used to minimize its effects in this Fact Sheet (PDF, 2MB).
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Planning & Development Division Manager