This is the second public comment period for this revision of the SWMM. The first public comment period was open from July 15 to August 19, 2024. The proposed changes for this public comment period differ from those shared for the earlier public comment period.
Below is a summary of the comments and responses from the first public comment period.
What changes are being proposed for this comment period?
Water quality storm event infiltration requirements (Chapters 1, 2, 3, and 4)
2020 SWMM: No discussion about a performance standard for infiltrating the water quality storm event. Requires water quality treatment and flow control for areas that drain to the separate storm system.
Previous public comment draft: Require, when feasible, infiltration of the water quality design storm event for sites with at least 0.5 inches per hour infiltration rate in areas that drain to upland streams.
Current public comment draft: Give projects designed using the Presumptive or Performance Approach the option to infiltrate the water quality design storm instead of meeting water quality treatment and flow control for hydromodification standards for any site that drains to the separate storm system.
- Details: Remove the following details from the SWMM
- SW 101. Unlined Basin, Infiltration < 2 in/hr
- SW-151. Unlined Planter, Infiltration < 2 in/hr
- SW-171. Unlined Sand Filter, Infiltration < 2 in/hr
- SW-181. Soakage Trench with Overflow for Infiltration < 2 in/hr
Reason for the changes: Sites that discharge to the separate storm sewer system that do not have 2 inches/hour of infiltration can be found in parts of the city with tight soils and steep slopes. Presumptive and performance design approaches require licensed design professionals, which will ensure a thorough analysis of the feasibility of onsite infiltration for these more complex sites. Making infiltration an option instead of a requirement will provide more flexibility for balancing site design considerations, including land use, site grades, and access to an offsite connection for stormwater.
Right-of-way applicability and exemptions (Chapter 1)
2020 SWMM: Exemptions for pavement replacement included maintenance activities where soil is not exposed, trench repair for utility trenching, and pavement restoration when no more than 50% of the street width is repaved.
Previous public comment draft: Exemptions for pavement replacement provided additional specificity for maintenance activities, set exemptions for stand-alone utility trench and base repair for repaving projects when no more than 50% of the street is repaved and exempted structural pavement repairs when less than 40% of the street is repaved.
Current public comment draft: The policies are similar to the previous public comment draft, but the language has been rearranged to improve clarity. Figure 1-1, which defines the difference between maintenance and redevelopment, is moved from the exemptions to the applicability section. It now serves as the basis for determining if an activity is considered redevelopment and triggers the SWMM. New stand-alone exemptions have been added for in-kind replacement of pedestrian-only areas, and installation of curb ramps. The exemption for structural pavement repairs when less than 40% of the street is repaved remains but has been reworded.
Reason for the changes: The policies are similar to the previous public comment draft but improve clarity. The 2020 SWMM exemption for projects that perform base repair that is less than 50% of the road width means that when some part of the project crosses the centerline, SWMM compliance is required. The new exemption for base repair that is less than 40% of the road width is based on the total road area. This requires projects that are repaving a significant fraction of the road width to comply with the SWMM. In addition, the revision adds a new exemption for the installation of curb ramps that replace existing corners. Curb ramps that do not include a curb extension or bulb-out are exempt from the SWMM.
Operations and maintenance form, plan, and recording requirements (Chapters 1, 3, 5, and 9)
Property owners are responsible for ongoing operations and maintenance (O&M) of stormwater facilities built to comply with the SWMM. This responsibility is established by recording O&M information on the property deed.
2020 SWMM: Applicants are required to submit an O&M form, an O&M plan, and a site plan. This submittal package requires a notarized signature. The applicant is required to record the full package against the property deed at the relevant county recorder's office.
Previous public comment draft: The O&M form was simplified, including removing the requirement for a notarized signature. The language now allows the City to complete a recording of the O&M form with the county for the applicant and to charge a pass-through fee for this service.
Current public comment draft: Additional edits are made to the O&M form to streamline the legal language, remove the requirement to attach standard O&M plans, and include a separate site plan. The form instead refers to and relies on O&M plans in the SWMM and permit records filed with the City as part of the permit review process.
Reason for the changes: Overall, these changes simplify and streamline O&M submittal and review processes. Having the City record the O&M form on behalf of the applicant should reduce the number of review cycles (checksheets) for permits. The changes presented in this draft simplify the submittals and forms even further.
Public works green street planting and 2-year warranty period maintenance (Chapter 6)
Public works permit projects that construct green streets or other vegetated stormwater facilities are required to plant and provide vegetation maintenance during the 2-year warranty period.
2020 SWMM: Public works permit project permittees can choose to plant and maintain vegetation during the 2-year warranty period themselves or enter into a voluntary agreement with Environmental Services to provide those services.
Previous public comment draft: Require public works permittees to pay a fee and change the responsibility of planting and maintenance of vegetation during the warranty period from the permittee to Environmental Services.
Current public comment draft: Retain the current requirements and options in the 2020 SWMM for planting and 2-year vegetation maintenance. Environmental Services will require a fee for this service once a fee is adopted by City Council in the future.
Reason for the changes: Switching to a fee for planting and 2-years of vegetation maintenance will improve outcomes for green streets; reduce permittees' maintenance responsibilities during the 2-year warranty period; provide permittees certainty about the costs associated with green street inspection, planting, and establishment; and improve predictability of timelines for completing public works projects. However, to implement this, City Council needs to adopt a fee. The 2025 SWMM will reflect requirements prior to and after the adoption of a fee.
Drainage Reserve Channel and Buffer Encroachment Categories (Chapter 7)
Drainageways are protected by drainage reserves in the SWMM. Drainage reserves are typically 30 feet wide and centered on the drainageway channel. Encroachments into the drainage reserve are permitted through development review, and the level of review is based on the impact of the encroachment and the location of the encroachment. Encroachment areas are delineated as buffer (the outer portion of the drainage reserve) and channel (the area closest to the channel). Encroachments into the channel area require additional engineering analysis to evaluate impacts on conveyance capacity.
Previous public comment draft: The channel encroachment area is delineated as 10 feet from the center of the channel on either side (20 feet total).
Current public comment draft: Reduce the width of the channel encroachment area to 7.5 feet from the center of the channel on either side (15 feet total). The overall typical drainage reserve width of 30 feet is maintained.
Reason for the changes: A 15-foot-wide channel encroachment area aligns with Section 24.50.050 Flood Hazard Area requirements for unidentified watercourses. Additional engineering analysis for encroachments in the 15-foot channel area would apply when both regulations are triggered. The purpose of this change is to help streamline permit requirements when regulations from multiple bureaus are required for development. Environmental Services has the authority to protect drainageways with wider reserves, and therefore, analysis of conveyance capacity impacts can be required in cases where the 15-foot standard channel encroachment area is not large enough.
Complete documents of proposed SWMM changes
The documents below contain all of this comment period's proposed SWMM changes. Changes are shown as track changes compared to the first public comment draft, not the published 2020 SWMM.
Chapters
Forms
Environmental Services is updating the forms to align with proposed changes to the SWMM, which simplifies processes and reduces submittal requirements.
Public comment period is closed
Environmental Services accepted public comment on the proposed changes from 8 a.m. December 4, 2024, through 5 p.m. January 10, 2025.
Public Hearing Request
Environmental Services did not receive a request to hold a public hearing by 5 p.m. Tuesday, December 10. The hearing has been canceled.
When will the changes take effect?
The updated SWMM is planned to take effect on March 1, 2025. There will be a three-month period during which the 2020 SWMM can also be used. Starting three months after the effective date, the requirements of the 2025 SWMM will apply except for City-initiated and public works projects at or past 60 percent design and building permits that are deemed complete.
For more information or questions, contact Adrienne Aiona at bescoderule@portlandoregon.gov or 503-823-2051.