Mill Creek outlines stormwater fixes, inspections and outreach to meet state NPDES requirements

Mill Creek staff told the City Council on Jan. 7 that the city is on track to resolve deficiencies tied to its Phase 2 municipal stormwater permit under the National Pollutant Discharge Elimination System (NPDES), but that addressing the issues will require sustained operations and an expanded education program.

The city’s stormwater presenter, Reese (stormwater staff), said Mill Creek has been in regular contact with the Washington State Department of Ecology and is negotiating an agreed order that sets deadlines and reporting steps. "The city is working with the Department of Ecology to enter what's called an agreed order," Reese said, describing the back-and-forth needed to align deadlines and to document measures the city has already completed.

Why it matters: The NPDES Phase 2 permit implements Clean Water Act requirements for small municipal separate storm sewer systems. Failure to meet Ecology's deadlines can expose the city to civil penalties and requires the city to put in place systems and procedures to prevent future violations.

City staff told the council the bulk of the compliance work falls into five categories: illicit-discharge detection and elimination; inspection and maintenance (including catch-basin cleanouts); system design documentation; source-control inspections of businesses; and public education and outreach. Many corrective items are procedural — standard operating procedures (SOPs), documentation and electronic recordkeeping — but inspections have also identified physical repairs that will require funding and contractor work.

Reese described the inspection program and results. City-contracted inspections have produced roughly 3,128 recorded catch-basin inspection data points since Reese began tracking them. Staff reported 2,039 basins with structural issues overall; of those, 736 were identified as needing maintenance (a mid-level severity), and four were identified as immediate, high-severity repairs for which work has begun or is underway. Reese said the city has set up electronic inspection forms that attach photos, timestamps and geolocation data to each record to make reporting and future tracking easier.

On privately owned facilities — such as stormwater ponds or basins on HOA-maintained streets — Reese said those properties are not required by the permit to submit inspection reports to the city but that staff will engage owners when inspections find private facilities out of standard. "If an HOA sent me a report, like, I got the maintenance report from MCCA. Very happy I got it. It was really helpful. It's not required," Reese said.

Public education is also a permit requirement and will be expanded. Reese said the previous outreach program met minimal requirements but the new permit requires a behavioral-change campaign grounded in social-marketing principles. Staff are working with city communications and marketing to design a program focused on pet-waste stewardship because local walking trails and the city’s TMDL (total maximum daily load) priorities for North Creek make pet waste an appropriate, measurable target.

Timing and costs: Many corrective elements have March 31, 2025, reporting deadlines tied to annual permit reporting. Reese said most items that remain are SOP write-ups, final database organization and follow-up scheduling for structural repairs. For the larger maintenance items (beyond simple mortar or grate replacement), staff expect contractor costs to be larger but said the majority of identified problems are relatively small fixes if addressed before they worsen.

Reese also told the council that Ecology provided the city with a list of issues Ecology considered corrected and that the agreed-order negotiation is intended to formalize required deadlines. When asked by the City Manager about potential penalties, Reese said Ecology "didn't have a total number, but it was $10,000 per day per fine," and added that in his discussions that could be presented as a much larger exposure if noncompliances were left unresolved.

What councilmembers asked: Councilmembers pressed staff on engagement with HOAs and private-property owners, the role of existing staff versus contractors, and where funding for maintenance would come from. Reese said much of the corrective documentation work is being done in-house, while larger inspections and cleanouts have been contracted out to preserve staff capacity for SOPs and public outreach. The city manager and other councilmembers thanked Reese and operations staff and said they will budget for maintenance and consider long-term staffing versus contracting.

Next steps: Reese said staff will finalize SOPs, complete remaining inspections and photo verifications, develop recommended maintenance actions and cost estimates for required repairs, and continue the biweekly Ecology meetings. The city manager and council indicated staff should return with a cost estimate and a timeline for remediation and planned maintenance, and Reese said a directional cost estimate for the basin repairs should be available in the next quarter.

Ending: Councilmembers thanked staff for the work to date and for the increased inspection and documentation capacity. The city will continue to work with Ecology to finalize the agreed order and to complete required work before permit reporting deadlines.