Flood District Outreach Project

City Park Channel is part of a mapped floodplain regulated by the Federal Emergency Management Agency (FEMA). A Conditional Letter of Map Revision (CLOMR) will be developed and submitted to FEMA before construction starts on the project. The CLOMR was submitted in early Summer 2023 and approved in March 2025. A final Letter of Map Revision (LOMR) will be prepared and submitted to FEMA after Phase 2 is constructed. When approved, the LOMR will result in the remapping of the City Park Channel floodplain and floodway from US 287 to just downstream of Main Street.

Project Overview

The conceptual plans for the Channel between US 287 and Main Street cover a large area. To complete the improvements, the project will need to be phased as capital improvement funds are allocated. A Phase 1 project was identified to progress to final design and construction. Phase 1 improvements will extend approximately 300 feet to the East and West of Main Street along City Park Channel. Improvements will center around an enlarged concrete box culvert under the roadway for the channel and will add a pedestrian crossing under Main Street. The enlarged crossing for the drainageway will allow the 1% annual chance storm event (100-year storm) to be conveyed completely under the roadway and will no longer overtop Main Street. To accommodate the pedestrian undercrossing, the invert of the channel will be lowered by approximately 4 feet, and the roadway will be raised by approximately 1.5 feet in the immediate vicinity of the drainageway. To accommodate the channel lowering, a sculpted concrete drop structure will be added to the drainageway to the west of Main Street. To accommodate the improvements, the existing irrigation culvert for the Harry Brown Ditch will be reconfigured. Multimodal improvements will include the pedestrian undercrossing that will meet ADA criteria and the reconstruction of the bike lanes on Main Street. The existing at-grade pedestrian crosswalk with a signalized light will be replaced with a High-intensity Activated Crosswalk (HAWK) pedestrian crossing beacon.

In the Spring of 2022, conceptual construction drawings were completed for the City Park Channel between US 287 and Main Street. A Phase 1 project was identified from the conceptual design to progress to preliminary and final construction plans. With coordination for the Broomfield Town Square development, Phase 1 was revised to include the channel upstream and downstream of Main Street and the pedestrian underpass at Main St. Preliminary construction plans were completed in 2024 and will continue to final construction plans by late Summer 2025. Additional field data collection was completed before the development of the preliminary plans including expanded limits for Survey and Subsurface Utility Engineering (SUE), which is necessary for the design to be complete. Early utility relocation is underway as of Spring 2025. Geotechnical information was also gathered to analyze the soils in the area to inform structural and pavement designs. Staff will continue to coordinate with the Mile High Flood District (MHFD), and internal stakeholders, including Parks & Recreation, Public Works, and Transportation as well as with the Broomfield Town Square development

The Mile High Flood District held a public information meeting on April 13, 2022.