Skip to Main Content
City of Lake Oswego

Stormwater Program

Showing the need for stormwater management

The City's new stormwater code and the Lake Oswego Stormwater Management Manual are now in effect. Manual files are available using the links below.

Missed our March 11 briefing on the new stormwater requirements for development and other construction projects? The presentation is here.

In the early 1990's, the Federal Clean Water Act was amended to require select urban areas to have a municipal stormwater (or MS4) permit. In Oregon, this program was delegated to the Oregon Department of Environmental Quality (DEQ). Clackamas County was one of the jurisdictions required to obtain an NPDES permit, and the City of Lake Oswego is one of the 13 co-permittees on the Clackamas County permit. The City of Lake Oswego received their NPDES stormwater permit from DEQ in 1995. The NPDES Permit has subsequently been renewed in 2004 and in 2012, and is due for renewal again on March 1, 2017.

The permit requires the City to:
1. Manage stormwater at City facilities and on the City right or way
2. Require stormwater management on private parcels as they develop or redevelop
3. See that stormwater facilities are properly operated and maintained
4. Provide additional oversight for high pollutant-load generating areas (industrial & commercial)
5. Control erosion from construction
6. Control non-stormwater discharges to the storm drainage system
7. Provide public and staff education and outreach around stormwater best practices
8. Provide opportunity for public involvement and participation, particularly at the time of permit renewal
9. Undertake targeted evaluations of specific issues as required by DEQ
10. Monitor the stormwater system; and
11. Report annually on City activities related to the permit. (Recent annual reports are available here.)

Stormwater Management Manual

Changes to City Code and adoption of a stormwater manual are permit requirements under item 2 above. The City Council approved the code amendments on February 16, 2016.  The December 2015 draft of the Lake Oswego Stormwater Management Manual is undergoing a final polish before adoption in time to support the new code, which becomes effective March 17, 2016. FAQs on the Code and Manual are here. This draft includes modifications since the July 2015 draft proposed during the fall 2015 land use review public process.

This Manual, and related amendments to the City’s drainage and surface water utility codes, is a requirement of our current NPDES stormwater permit (part of Item 2 in the list above). The Manual emphasizes the use of infiltration-based approaches to stormwater management where possible, along with other low-impact development (LID) techniques to minimize runoff from roofs, streets, driveways, and other impervious surfaces. The manual will apply to the design of newly developing and re-developing sites, and has requirements based on different thresholds of impervious surface area. The City Council approved the stormwater code amendments on February 16, 2016. The new Manual document, with appendices, is available at the links below.

For those of you wanting more information on Low Impact Development (LID) Techniques for stormwater management work, check out this video: Reduce Runoff: Slow It Down, Spread it Out, Soak It In [8:43 minutes]