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Creve Coeur considers wetland alternative as option to dredge Conway Park lake
Summary
City staff presented two rehabilitation options for Conway Park lake — dredging to create a deeper open-water pond or converting to a pocket wetland — and council members expressed a general preference for a well-designed wetland while raising questions about cost, maintenance and fish habitat.
Creve Coeur city staff on Monday presented two design options to address sedimentation and recurring algae issues at Conway Park lake: dredging to restore deeper open water or converting the site to a pocket wetland.
City engineer Steve Perez told the council that the pond, constructed in the mid-1980s, has largely filled with sediment and that one of the two existing control structures is not functioning. Perez outlined a deep-water pond design with a 12-foot deep hole and other areas 6 feet deep, forebays to trap sediment, and on-site dewatering where excavated material would be spread and regraded and then covered with native plantings. He said staff had an initial construction budget figure “around $410,000” but that a separate deep-water dredge estimate was “closer to over a million with contingencies.”
Tim Dean of Intuition and Logic Engineering told the council that wetlands and wet ponds work similarly for pollutant removal but that “they tend to have a little bit higher pollutant removal efficiency” because of additional plant material. Dean said wetlands can help reduce algae by taking up nitrogen and phosphorus and that designing some deeper threads (deeper channels) can preserve fish habitat. He described a pocket wetland alternative that would require less excavation, use multiple forebays to collect silt and limit the need for frequent dredging.
Council members asked technical and aesthetic questions about the two approaches. Members sought clarity on whether motorized scooters and other equipment would be affected by park regulations, asked about long-term maintenance and how the forebays would reduce future sediment accumulation, and whether a wetland would appear “unkept.” Staff and consultants said plant selection and intentional planting groupings could create a formal appearance and that forebays would concentrate silt in maintainable locations.
Staff discussed alternative lower-cost options, including converting the existing structure into a dry detention basin and reusing previously excavated spoil material from a nearby hillside to fill portions of the pond. A staff member noted that converting to a dry detention basin would require coordination with MSD (Metropolitan St. Louis Sewer District) to ensure the feature continues to meet water-quality benefit requirements.
Several council members said they prefer a wetland if it is designed and planted intentionally; one council member specifically referenced Millennium Park’s earlier dry detention basin experience as a cautionary example of a feature that took years to naturalize. Staff said they will solicit input from the Parks and Historic Preservation committee and other stakeholders and continue design work; no final vote was taken at this meeting.
The council flagged cost estimates and program details as questions for follow-up, and staff said they would return with refined numbers and recommended final designs at a later meeting.
