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Marion staff and HDR identify maintenance needs at top 10 city detention basins
Summary
Consultants and city staff inspected 10 city-owned detention basins and found three — Prairie Ridge No.1, Talby Park and English Glen No.1 — with near-term maintenance needs; a final report with recommendations and an operations-and-maintenance plan will follow.
City staff and consultants presented the results of a detention-basin condition assessment at the Marion City Council work session Tuesday, identifying near-term maintenance needs at several basins and asking council to review stormwater criteria used to prioritize future projects.
Consultants from HDR and Marion Stormwater Coordinator Steve Cooper told the council the team inspected the city-owned basins on Aug. 31 and prioritized the top 10 that staff and model results suggested may not meet current design standards. The city owns about 60 detention basins; the study focused on the tier-1 group of 10.
HDR said field inspections used six categories — inlets, main storage area, embankment, outlet structure, auxiliary spillway and miscellaneous access/fencing — and that findings from the August visits will be summarized with photographs and recommendations in a final report. Basin conditions were categorized as outstanding, satisfactory (preventive maintenance suggested) or needs improvements (near-term work suggested).
The consultant identified Prairie Ridge No.1, Talby Park and English Glen No.1 as the three basins with several maintenance needs, mainly related to embankments, auxiliary spillways and outlet structures. Examples offered at the meeting included vegetation growth on a spillway at English Glen that could impede flow and a blocked inlet producing a foot of standing water; at Talby Park staff observed a clogged outlet that routinely requires maintenance; and at Prairie Ridge No.1 inspectors found heavy sedimentation at the outlet and debris blocking inlets.
Cooper and HDR staff said the findings have already been passed to city maintenance staff and that an operations-and-maintenance component of the stormwater master-plan project will identify actionable near-, mid- and long-term maintenance activities. Staff also asked council members to complete a stormwater-criteria ranking survey by Sept. 23 to guide project prioritization in four identified complex solution areas.
The consultants emphasized the report is a summary of field observations and that specific repair scopes and cost estimates will appear in the final deliverable.
Council members asked how the 10 basins were selected; HDR said the selection used several criteria including age, modeled performance versus current design standards and human-risk factors downstream. Staff confirmed that some of the identified maintenance items were already known to operations crews.
