Pitkin County engineers advance Redstone South Bridge replacement; public outreach begins

County engineers presented a preliminary design and schedule Tuesday for replacing the Redstone South Bridge in Redstone, saying the structure is at the end of its service life and should be replaced before an emergency repair is required. The county has progressed the project to roughly 30% design and is beginning public outreach this month ahead of further design and permitting work.

The project team reported the existing bridge was built in 1947 and is the oldest structure on the county inventory. Engineers told commissioners the structure has received previous scour mitigation but continued hydraulic and foundation concerns prompted the recommendation to replace it rather than pursue extended repair. County staff said the design eliminates the center pier to reduce debris snagging and scour, increases the bridge length to open the Crystal River channel, and adds a 10-foot sidewalk on the north side.

Why it matters: the bridge is a local route into Redstone and a frequent constraint on the State Highway 133 corridor. Staff emphasized preserving traffic redundancy for the community during construction and reducing long-term maintenance costs by selecting a low‑maintenance prestressed concrete box girder structure.

Key design and schedule points

- Alignment: staff and the SGM consulting team evaluated an alternate north alignment that would allow the existing bridge to remain open during construction but concluded the alternate alignment would cause substantially greater wetland disturbance, require more fill and roadway tie-ins, lead to a longer schedule and higher cost, and be less compatible with future State Highway 133 acceleration-lane plans. The project team recommended replacing the bridge in essentially the existing alignment and demolishing and rebuilding in place, with a slight northward shift to accommodate a full-width sidewalk.

- Bridge geometry and safety features: the proposed inside‑of‑rail width is about 34 feet (existing is about 28 feet), with a single 10-foot sidewalk on the north side. The proposed bridge length is roughly 93 feet versus the existing nearly 83 feet; the design removes the center pier and places the structure on deep foundations and modern crash‑tested railings to meet current safety standards.

- Environmental and permitting: designers completed field survey work (topographic, wetlands delineation, cultural resources). Army Corps of Engineers permitting will follow a Nationwide Permit 14 path once the design is more final; the County will also need a Colorado Department of Transportation special‑use/structure permit for work that ties into Highway 133. Staff flagged known site issues including coal‑slag/coke‑oven material adjacent to the bridge and lead paint on existing girders; the team plans testing and contractor guidance for safe handling and disposal.

- Schedule and cost: staff said the project is at a 30% design milestone, with public engagement in February–March, a 90%/FOR design and additional outreach planned in August–September, and a goal to produce a shovel-ready package in fall for potential 2026 construction. The consultant offered a planning‑level cost estimate of about $4,000,000 at 30% design; contingencies will be refined as the design advances and final costs will depend on bids.

Next steps and outreach

County staff said they will continue public engagement in Redstone (outreach events scheduled for February–March), refine the design to 90% for additional outreach later in the year, finalize permit submittals (Army Corps, CDOT) and pursue grant opportunities that could offset project cost. Commissioners asked staff to track any additional time or expense introduced by the Crystal River wild-and-scenic eligibility process and to report back on permitting timelines. Staff also committed to continue coordinating with local fire districts and open‑space/trail planners (the proposed sidewalk ties to the Carbondale–Crested Butte Trail alignment and open‑space staff have offered a potential funding contribution).

Commissioners and project staff said they would present updated designs and outreach materials at upcoming public meetings and that staff would return with permit timelines and updated cost/budget figures as the project advances.