Des Moines Environment Committee reviews 2024 NPDES work, outlines 2025 stormwater priorities

The Environment Committee of the Des Moines City Council heard a review of the city's actions under its National Pollutant Discharge Elimination System (NPDES) permit and a preview of the 2025 Stormwater Management Program on March 13.

Surface Water Manager Tyler Beakley introduced the presentation and Michael Caposi, the city's NPDES coordinator, gave the overview of 2024 accomplishments and planned work for 2025. Caposi said the city moved from the 2019'2024 permit cycle into the 2024'2029 cycle on Aug. 1 and described the program's eight categories, including stormwater planning, public education, illicit discharge detection and elimination, and operations and maintenance. "NPDES stands for the National Pollutant Discharge Elimination System," Caposi said.

Caposi summarized key 2024 figures and activities: the city has 5,095 known public catch basins; staff inspected basins and other facilities and identified maintenance needs; the civil engineer reviewed 97 development plan sets and the surface water inspector conducted 111 erosion-control inspections with 45 enforcement items arising; the surface water maintenance crew of six inspects and maintains 235 public stormwater facilities; and the city responded to 48 reported spills last year as part of its illicit-discharge program. He said the city's Adopt-a-Drain volunteer program added 41 volunteers in the prior 12 months and that the Highline Storm Fest engaged about 1,200 students over three days in June.

The committee discussed tree-canopy mapping and a new Ecology credit program that allows jurisdictions to earn permit credit by protecting or acquiring forested parcels. Beakley said the permit requires mapping trees on public land for Ecology reporting but the Ecology contract will also map private lands, giving the city a full canopy inventory at the consultant's contract completion. "The permit requirement is to map trees on public land," Beakley said. He and committee members discussed whether local policy should be expanded later to address private trees or replacement requirements; Beakley said staff and a consultant will provide recommendations and that any policy changes would come back to the council.

Staff said the city is expanding source-control inspections for businesses (formerly performed by a contractor) and will bring those inspections in-house this year; three staff members have been trained. The city will send informational letters to the 40 businesses identified for inspection and plans to present results in November. City staff also plan street-sweeping mapping, berm-and-curb mapping for prioritization, and an updated software platform for field reporting (moving from City Works to Respond).

Committee members asked about monitoring for emerging contaminants. Caposi and Beakley said the city is beginning to look at PFAS and PCBs as potential monitoring priorities, noting PFAS concern near airports because of historical firefighting-foam use. Caposi said Des Moines does not use PFAS-containing firefighting foam and that staff are coordinating with South King Fire on inventory and disposal options.

Committee members asked for additional clarity on inspection statistics and enforcement. Staff said the 111 inspection visits can include return visits to ongoing sites and that many recorded "enforcement items" are minor repairs (for example, re-erecting silt fence) rather than large washouts; the threat of penalties has been effective in obtaining compliance. On basin inspections, staff said they follow the King County maintenance manual and perform physical checks (pull lids, probe for sediment, check cracking) but do not perform chemical testing as part of routine basin inspections.

Staff highlighted 2025 calendar items: public comment for the 2025 Stormwater Management Program is open through March 31; the Highline Storm Fest is planned for June 10'12 at Beach Park with an anticipated 1,200 student participants; and staff will present a mid-year update in July and a business-inspection report in November. Committee leadership also announced the April Environment Committee meeting will be canceled and asked staff to provide monthly check-ins to maintain continuity on complex stormwater matters.

The committee approved the minutes from the prior meeting at the start of the session. No formal ordinance or rule-making actions were taken at this meeting; staff were directed to continue work on mapping, consultant analysis for tree policies, in-house source-control inspections and monitoring guidance for PFAS and PCBs.