Council hears storm drainage master plan update that lists 20 projects, $51M estimate

City staff and consultants presented an updated storm drainage master plan that identifies a set of capital projects to address flooding, aging infrastructure and projected increases in impermeable surfaces.

“Overall, the recommendations are to implement the capital facility plan, continue to maintain and clean the system, continue the video inspection periodically ... and then monitor that watch list,” consultant Kai Krieger of Hansen Allen Lewis Engineering told the council during an Aug. 12 presentation. Krieger said the plan divides the city into subbasins, models runoff using satellite imagery, lidar and NOAA rainfall data, and identifies where pipe capacity and outlets will need upgrades.

Krieger said the analysis produced about 20 discrete capital projects and a separate watch list of likely problem areas. “The total cost ... comes out to about $51,000,000,” he said when asked by councilmembers for a cost estimate. He added the watch-list projects are areas the firm recommends monitoring in future storms rather than moving immediately into the capital plan.

Councilors pressed staff on whether the city’s current revenue streams could support the plan. Corby Talbot, who introduced the consultant, said he did not have that fiscal analysis available at the meeting. Krieger said the plan is intended to guide future design work and be revised as needed: major projects would undergo further design and verification before construction, and the plan is to be a “living document.”

Following questions about modeling data, metering and contingency planning for measures that don’t perform as expected, Councilmember Sharla moved to place the stormwater master plan on the Aug. 26 agenda under unfinished business for additional review. The motion carried by roll call. No funding decisions or ordinance adoptions were made at the Aug. 12 meeting.

Implementation details the consultant cited include using video-inspection to identify pipe issues, allowing limited roadway conveyance during overflow conditions, and revisiting designs when monitoring shows a problem. The plan identifies both near-term projects and items scheduled 15-plus years out; specific project schedules and funding sources will be discussed at the follow-up meeting.