Stormwater Code Revision & Design Manual Update

Point and Non-point Pollution Sources
The goal of stormwater management is to improve the quality of the stormwater runoff before it enters a water body.  To properly manage stormwater pollution it is important to understand the two different sources of stormwater pollution: point sources and nonpoint sources (NPS).

A point source is a single identifiable localized source of pollution, such as a municipal sewage treatment center, which are tightly managed by national standards including the National Pollution Discharge Elimination System permit program of the Clean Water Act.

Non-point sources (NPS) of pollution are the Nation's largest source of water quality problems, according to the EPA.  Non-point pollution occurs when rainfall, snowmelt, or irrigation runoff collects pollutants and carries them into area rivers, lakes, or ground water.  Runoff can collect debris, chemicals, sediment or other pollutants that could adversely affect water quality if the runoff is discharged untreated.  Nonpoint sources are also called “urban nonpoint sources” because urbanization increases the variety of pollutants and likelihood of stormwater collecting pollutants before re-entering water bodies.  This is due to the increase in impervious surfaces, buildings, and pollution-causing activities that can be found in urban and suburban areas.

The following Common Non-Point Pollution Sources are being considered in the Lake Oswego Stormwater Code and Design Manual update:

  • Sediment
  • Oil, grease and toxic chemicals from motor vehicles
  • Pesticides and nutrients from lawns and gardens
  • Viruses, bacteria and nutrients from pet waste and failing septic systems
  • Road salts and sand
  • Heavy metals from roof shingles, motor vehicles and other sources
  • Thermal pollution from dark impervious surfaces such as streets and rooftops
Project Background / Summary: 

The Stormwater Code/Design Manual Project will establish requirements to protect and improve Lake Oswego's water resources (including Oswego lake, Springbrook Creek, the Willamette River, Tryon Creek, and the Tualatin River), meet regulatory requirements, and ensure transparency and consistency in how stormwater requirements are applied and enforced.

The project will:

  • Protect and improve Lake Oswego's water resources: The community recently established a vision through the We Love LO process. It says, "We are good stewards of our environment.  Our urban forest, natural areas and watersheds are valued and cared for as essential environmental, economic and cultural assets by the Lake Oswego Community." This project is one very specific way that the City will work to achieve that long-term goal.
  • Meet regulatory requirements required as part of the Clean Water Act and Safe Drinking Water Act.
  • More clearly explain stormwater requirements.
  • Assure consistency in how stormwater requirements are applied and enforced so the community remains business-friendly and supportive of the needs of existing and future residents.

Outcomes: The process will result in three products, described briefly below.

  1. Stormwater and Surface Water Utility Code Update: An update of the stormwater municipal code will eliminate redundancies and inconsistencies, improve clarity and readability, and ensure that our code meets applicable legal requirements.
  2. Stormwater Design Manual: The updated stormwater design manual will contain design guidance for traditional stormwater technologies as well as newer approaches using Low Impact Development and Green Infrastructure that include rain gardens, green roofs, and swales. The purpose is to ensure that stormwater facilities are attractive amenities that perform well over time, protect our water resources and incorporate landscaping and features that reflect our community needs and values.
  3. Policies and Procedures Guidance: A new policies and procedures guidance document will outline administrative procedures for the stormwater plan review, inspections, and maintenance process. This will streamline the review of development/redevelopment projects in the City and ensure transparent and consistent enforcement of requirements.
Project Updates: 


Work is well underway to update the City’s stormwater code and design manual.  The Project Team has been reviewing regional stormwater codes and manuals including those from the Clackamas County,  City of Portland, Clean Water Services, City of Seattle, City of Gresham, City of Eugene and the City of Salem. 

A big area of focus is promoting low impact development as a best management practice (BMP). To make sure that vegetated BMPs, such as rain gardens, reflect community aesthetics, treat stormwater effectively, and thrive, members of the Project Team have met with City maintenance staff. We are also talking to local nurseries about plant availability.  This will provide an opportunity for nurseries to respond to the growing need for particular plants.

This update will result in a code that easier to understand and meets the intent of State/Federal law. The updates to the Design Manual will provide clear guidance on how stormwater management facilities (e.g., swales and rain gardens) should be selected, sited, designed, constructed and maintained.

The first Project Advisory Committee meeting was held on October 12 with the next being on November 30.  All meeting materials and project information can be found on the project advisory committee page.

10/31/2011 - Stormwater Code and Design Manual Open House

The City of Lake Oswego held an outreach event held Saturday, October 22, at Hazelia Field to promote public understanding, education and enthusiasm of watershed issues and the current Lake Oswego stormwater code and design manual update project.  The event ran from 10:00a.m. – 1:00p.m. and featured informational stations and activities for participants to engage in and learn about stormwater issues in Lake Oswego.  These stations included information about:

  • Ways to protect streams and waterways;
  • Technologies that encourage watershed health including low impact development facilities and native plants;
  • Lake Oswego watershed maps;
  • Information about the Lake Oswego watershed code update project;
  • A fun pumpkin decorating station.

This event attracted several members of the Lake Oswego community who came specifically to learn about the project.  Because the convenient location, several other visitors stopped by while visiting Luscher Farm on the day of the event as well.

If you missed the event, the informational posters are available below.

Wet Leaves photo
Kids photo
Project Details
Project Contact: 
David Gilbey Water Quality Program Coordinator/Project Manager City of Lake Oswego, OR 503.675.3999
Related Meetings

May 2 2012 - 6:30pm

Feb 29 2012 - 6:30pm

Nov 30 2011 - 6:30pm

Oct 22 2011 - 10:00am

Oct 12 2011 - 6:30pm

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