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Tumwater staff outline how city will meet NPDES stormwater permit requirements
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Summary
Tumwater water-resources staff briefed the Public Works Committee on NPDES permit obligations, describing education, mapping, IDDE, inspections and retrofit projects (including a Beehive retrofit) that collectively exceed the city’s 4.2 equivalent-acre requirement and support TMDL work on the Deschutes River and Budd Inlet.
David, a water-resources staffer, told the committee that the city’s National Pollutant Discharge Elimination System (NPDES) permit, administered under the Clean Water Act by the Washington Department of Ecology, requires a citywide program of planning, mapping, monitoring and enforcement to protect state waters. The current permit runs from Aug. 1, 2024, to July 31, 2029.
David said the permit’s requirements reach across departments and include stormwater planning (tree canopy and site-review goals), illicit discharge detection and elimination (IDDE) and stormwater pollution prevention plans (SWPPPs) at facilities that store chemicals or equipment. "It is administered through the Department of Ecology through, through the Clean Water Act," he said, describing ecology’s role in the program.
Staff highlighted public-education and stewardship efforts including a regional stream team, Habitat at Home natural-yard-care workshops (in partnership with Thurston County Fish and Wildlife) and volunteer restoration events at Sap Road Park and Palermo Wetlands. David said these outreach and volunteer efforts feed into permit compliance and behavior-change goals.
On mapping and inspections, David credited GIS staff with tools and an app that help crews prioritize work. He said the city is required to screen a portion of outfalls in dry weather; the permit requires 12% annually and Tumwater performed almost 15% last year. He explained the field work: catch basins in neighborhoods feed pipes that terminate at outfalls in rivers, wetlands or other receiving waters, and staff follow up on unexpected dry-weather flows through source tracing.
The presentation included operations metrics: the city maintained 52 of 92 known treatment facilities last year; inspected almost 1,600 of nearly 4,000 catch basins; cleaned or repaired 672 catch basins; and removed 775 tons of material via sweeping and catch-basin cleaning. David said a dashboard and mobile survey app have increased inspection and cleaning productivity.
David described a new permit requirement — stormwater management for existing development — that assigns points by "equivalent acres" to encourage retrofits and land-management strategies. Tumwater’s assigned requirement is 4.2 equivalent acres. To meet that, staff are pursuing several projects: the Beehive stormwater retrofit (designed with Fuller Designs) is approaching 90% design and will provide 51.64 equivalent acres; Sap Road Park restoration and Pioneer Park bank stabilization together bring total equivalent acres to about 53.02, far exceeding the requirement. "We’re blowing it out of the water, for our requirement," David said of the combined projects.
The city is also addressing two Total Maximum Daily Load (TMDL) obligations: Deschutes watershed temperature reduction (work at Pioneer Park, tree planting and stream shading) and nutrient reductions for Budd Inlet (enhanced maintenance, targeted sweeping and strategic outreach). Staff are developing a nutrient-reduction enhanced maintenance plan with consultant Herrera and have purchased a deep-channeled aerator for the Tumwater Valley Golf Course to reduce runoff.
Looking ahead to 2027, David said Ecology will ask for detailed annual expenditures and a capital projects list; the permit will add new SMAP (stormwater management action plan) requirements; the city will refine its equity-index method for identifying overburdened communities; continue tree canopy mapping; conduct tributary-basin assessments; and update the drainage design and erosion-control manual and any related ordinances. The briefing was informational only and no committee action was required.
