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Utilities present 90% design for South Boulder Creek detention and CU South restoration; trustees press for public outreach and closure plans
Summary
Utilities staff presented 90% design plans for a regional detention project on South Boulder Creek that include an earthen embankment, a concrete spillway along U.S. 36, an outlet tunnel and a 19‑acre ecological restoration area on the future CU South open‑space parcel.
City Utilities staff presented the 90% design for the South Boulder Creek flood‑mitigation project that would detain floodwaters upstream of U.S. 36 to reduce over‑topping and downstream flooding. The project combines an earthen embankment, a concrete spillway/flood wall paralleling U.S. 36, an outlet tunnel under the highway, and a 19‑acre ecological restoration area on the CU South (future open space) parcel.
Staff said the project is a regional detention approach intended to prevent the life‑safety failures caused by prior floods and U.S. 36 overtopping in 1969 and 2013. The restoration plan calls for removing an existing levee on the CU South parcel, restoring historical floodplain topography, creating about 32 acres of wetlands and enhancing habitat for Preble’s meadow jumping mouse and Ute lady’s‑tresses orchid according to permitting needs and city objectives.
Design changes since 60% included additional geotechnical borings to determine groundwater and soil conditions, refinements to grading and planting plans, and proposed irrigation and water‑control structures tied to Dry Creek Ditch Number 2. Staff said they intend to exceed mitigation requirements in many habitats and will reissue a portion of water rights to operate wetland features.
Trustees asked about construction‑period public access and closures, possible dispersal of users to nearby trailheads, and the need for proactive communications. Utilities staff said a formal closure plan will be developed and the department will coordinate with Open Space, CU and communications staff; they also said construction is expected to begin in late third quarter 2025 and that permitting and contract bidding are ongoing.
Trustees recommended the project include visible opportunities for the public to observe restoration work (time‑lapse cameras, interpretive viewpoints) and requested early community outreach so neighbors do not mistake heavy equipment and earthmoving for other development uses. Staff agreed to explore cameras and interpretive opportunities and to plan outreach and signage for construction and restoration phases.
