Design & Construction Standards Update

At the April 2, 2019 Board meeting, the Board of Directors adopted an update to the Design & Construction Standards, which included revisions to stormwater requirements to address the effects of hydromodification. The revisions to these Standards were developed to meet requirements of CWS’ Watershed-Based permit and become effective on April 22, 2019. The Board also previously adopted an Implementation Policy (PDF, 336KB) which outlines the effectiveness dates that will apply for projects that are already in process.

A redline version of the adopted revisions are available for review below, and a finalized clean version of the adopted Standards will be available in the coming weeks.

At the April 2, 2019 Board meeting, the Board also directed staff to continue to look at the possibility of expanding the use of Fee-In-Lieu for a broader range of projects. Staff will be working with the Board to determine a schedule and process over the next couple of weeks. 

We encourage partners and members of the public to participate and stay informed. Sign up to get updates direct to your email.

Adopted Revisions to the Design & Construction Standards

Information added April 4, 2019

Updates to the standards are focused on incorporating requirements for development to address the effects of hydromodification. As such, proposed changes to the standards are focused on incorporating and updating relevant definitions in Chapter 1, engineering plan submittal requirements in Chapter 2, and inserting hydromodification requirements into Chapter 4. No changes have been made to the other chapters. 

CWS encourages interested stakeholders to review the following documents and tools:

The following documents, released in January, remain applicable:

Submit comments to DnCUpdate@cleanwaterservices.org

Design and Construction Standards Update Implementation Policy

On November 27, 2018 the Clean Water Services Board of Directors adopted an Implementation Policy (PDF, 336KB) 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.

Commonly Asked Questions

Why is CWS updating the Design and Construction 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.

When will the new standards take effect?

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, 336KB) 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:

  • Development and construction permit applications for projects that make application for land use approval prior to the effective date of the new Standards and for which land use approval is granted based upon such application, and for all development, construction and building permit applications made pursuant to the original land use approval and any valid extensions thereof, unless specifically requested by the applicant to use the new Standards.
  • Development and construction permit applications for projects that are not required to obtain land use approval provided application for construction permits is made within 180 days of the effective date of the new Standards and construction has started pursuant to the local jurisdiction’s  permit, but no more than two years from the construction permit date.

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.

What is hydromodification?

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).

Archived Documents and Context

Information issued March 29, 2019

CWS has developed additional language changes to address two areas in which the Board expressed interest during the March 26 public hearing. Those two areas are:

  • Impervious Surface Area to be used in calculating facility size serving developments with lots 3000 sf or smaller
  • Evaluation Criteria for requests to allow a pond depth greater than 5 feet

Additional Staff-Recommended Language Changes to Sections 4.08.1 and 4.09.2 (PDF 140KB).

Information issued March 27, 2019

During the March 26, 2019 Board meeting, staff recommended making several minor changes to the Proposed Chapter 4 that was posted on March 14, 2019.  These revisions included:

  • Infill Exemption Analysis (Section 4.03.7.a.5.D): clarify exclusions of “remaining developable area”
  • Allow for street trees to get Stormwater Tree credit (Section 4.09.15.c.3)
  • Clarify Impervious Area used for remodels, additions, etc. on existing single family lots (Section 4.08.1.b)
  • Pond Orifice Sizing: address possible conflict between co-implementer standards (Sections 4.09.2.c.8, 4.09.5.b.6, and 4.09.6.b.5)
  • Underground Detention
    • Add inspection ports and manholes (Section 4.09.3.c.2.d)
    • Require approval by road owner and maintainer (Section 4.09.3.c.3)
  • Vegetated Swale: 3’ max. ponding depth (Section 4.09.3.c.3)
  • Fix copy/paste error in Section 4.03.2

The Board directed staff to make these changes and post them for public review. 

Proposed Chapter 4, including revisions directed by the Board at the March 26 Public Hearing (PDF 468KB).

Information issued March 22, 2019

Since the release of the Preliminary Drafts of Chapters 1 and 4 on February 14, 2019, CWS has received many comments, suggestions and questions regarding the proposed changes. Staff has worked diligently to incorporate these comments into a Proposed Draft of the Design & Construction Standards. Updates to the standards are focused on incorporating requirements for development to address the effects of hydromodification. As such, proposed changes to the standards are focused on incorporating and updating relevant definitions in Chapter 1, engineering plan submittal requirements in Chapter 2, and inserting hydromodification requirements into Chapter 4. No changes have been made to the other chapters. Also included in this release is a memo describing CWS’ proposed approach to addressing the Stormwater Management Fee-in-Lieu charge. While adoption of the Fee-in-Lieu charge is not part of the Design & Construction Standards Update, it is relevant to the Base Strategy. The Fee-in-Lieu charge will be included with the proposed update of the CWS Rates and Charges, scheduled for the Board in June 2019.

CWS encourages interested stakeholders to review the following documents and tools:

The portions of the Complete Proposed Draft of the Standards with redlines are also posted as individual chapters to make review of proposed changes easier:

  • Proposed Draft Table of Contents (PDF, 23KB)
  • Proposed Draft Chapter 1 – General Requirements and Administrative Provisions (PDF, 190KB): added and revised definitions in Section 1.03
  • Proposed Draft Chapter 2 – Administrative Procedures (PDF, 191KB): Updated submittal requirements
  • Proposed Draft Chapter 4 – (March 14, 2019, version) Runoff Treatment and Control (PDF, 462KB): addition of hydromodification standard, and revisions to sizing criteria, infiltration criteria, and design criteria for specific facility types
Information issued February 14, 2019

Documents and tools:

Information issued January 16, 2019

Draft Hydromodification Base Strategy and Methodology

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 (PDF, 2.3MB) 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.

Contact

For meeting announcements and updates join our email list

Send questions or comments to dncupdate@cleanwaterservices.org

Damon Reische
Planning & Development Division Manager
503.681.5106
reisched@cleanwaterservices.org

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