First Creek Stream Restoration at 26th Avenue

Project Overview

This channel improvement project involved partnership with a private site developer and the Mile High Flood District to construct drainageway improvements at a property located in the regulatory floodplain. Prior to the project, the First Creek channel had poor definition and the floodplain spread across thousands of feet of open field, overtopping 26th Avenue for any event greater than 5-year flows due to an undersized crossing structure.

Significant coordination with the developer’s engineer was necessary as they were designing the private site improvement as well as changes to the 26th Avenue roadway corridor. ICON also coordinated stream design with a second developer for other private roadway downstream of 26th Avenue. Ultimately, the project involved thoughtful design of nearly 3000-LF of channel restoration and floodplain enhancement that included multi-stage terraces, riffle-pool sequences, bankfull, and drop structures to allow regular base flows.

The last major elements of the design included concrete arch roadway crossings at 26th Avenue (204’ length x 61’ width) and at private  land within the development. During construction, ICON provided full time construction management support; and ICON coordinated as-built survey and completed a LOMR upon construction completion.

Project Outcomes

• 3,000 LF of stream restoration and floodplain enhancement
• Multi-stage design with inner berm, bankfull, and flood terrace within a 300-ft wide floodplain
• 5.5-ft drop structure with grouted boulders
• Sculpted concrete low flow channel
• 204-ft x 61-ft Concrete arch roadway crossings
• Connection to an existing headcut at the downstream end of the project