Stormwater Management Plan & Monitoring Plan (MS4)

The City is revising the Stormwater Management Plan (SWMP) and Monitoring Plans. These plans were available for public comment for a 30-day period from October 17 through November 14, 2022. Thank you for sharing your comments! The Plans were finalized and are awaiting DEQ approval.  

What is the Stormwater Management Plan?

The SWMP is the City's comprehensive plan to keep the rivers and streams in Lake Oswego clean and healthy.  The plan is a requirement of the City's National Pollutant Discharge Elimination System (NPDES) Municipal Storm Separate Sewer System (MS4) permit.  There are seven minimum measures under the MS4 permit from which the City crafts strategies and implements policies.  Specific and measurable goals (tracking measures) are created from the strategies and policies, which provide information that is collected from departments throughout the City, collated, and sent to the Department of Environmental Quality (DEQ) each year in the form of a report.

Monitoring Plan

The Monitoring Plan describes the City's monitoring objectives, strategy, and procedures for collecting and analyzing stormwater and surface water samples.  The Monitoring Plan is also a requirement of the City's MS4 permit.  As part of the permit, the City is required to characterize the water quality of its streams and stormwater.  The City monitors water quality at six sites located at Ball Creek, Carter Creek, Springbrook Creek, Nettle Creek, Lost Dog Creek, and at Lamont Springs.  It also characterizes stormwater at two sites during two rain events per year.  The results are summarized in the annual report due to DEQ every year. 

Why is the City updating these plans?

On October 1, 2021, the Oregon Department of Environmental Quality (DEQ) renewed the Clackamas County NPDES MS4 permit.  The County's permit encompasses twelve jurisdictions, including the City of Lake Oswego.  The plans were finalized and submitted to DEQ for review on November 18, 2022.