Photo: Parsons Brinckerhoff

The new structure provides high-level clearance over the Intercoastal Waterway, which transitions into a low-level span over Lake Surprise. The bridge features one travel lane in each direction with a median barrier wall to prevent head-on collisions, a shoulder in both directions and new ramps providing access to local businesses.

The project’s design-build delivery allowed for innovations. For example, Granite Construction teamed up with geotechnical firm Hayward Baker to provide a solution to managing the organic soils encountered on site. The pre-existing northbound roadway was built on top of muck, a soft and compressible soil, consisting of silt, clay and plant matter. The soil stabilization process employed on this project is the first time it has ever been used in the United States.

Instead of demucking, which entails hauling muck off site and backfilling with good fill material, the contractor utilized a relatively new Swedish technology called soil mixing. The contractor injected the in-situ muck material with a mixture of 25% cement and 75 % slag, building a solid foundation anchoring the base to the caprock below. The resulting substrate provided a stable base for the roadbed to be built upon. Use of this method also eliminated the need for large fleets of dump trucks entering and leaving the highway that would have been necessary otherwise.

The project team also used specially coated stay-in-place forms that provided additional corrosion protection to the underside of the roadway in a highly corrosive environment. The Jewfish Creek Bridge project was one of the first applications of this product in a coastal marine environment.

The 18-mile stretch of U.S. 1 from Key Largo to Florida City has a long history of safety concerns due to speed, traffic volume, and a higher-than-usual number of crashes, including head-on collisions and vehicles running off the road. The roadway was reconstructed with one travel lane in each direction, divided by a concrete median barrier wall to prevent head-on collisions, and extra wide shoulders.

The reconstruction also has improved hurricane evacuation. The newly constructed 10-foot wide northbound shoulder enhances hurricane evacuations by allowing two lanes of traffic to travel north during these emergencies.

Another contribution to the community is the environmental enhancements incorporated into the project including: installation of storm water runoff treatment/retention facilities, and wetlands mitigation, including sea grass, mangrove and freshwater emergent restoration. As a component of the Comprehensive Everglades Restoration Program, this project has helped restore original water flow in the Everglades and North Key Largo.

Key Facts:

Owner: Florida Dept. of Transportation
Location: Key Largo, Fla.
Cost: $149 million
Construction Manager: Parsons Brinckerhoff, Miami
General Contractor: Granite Construction Co., Tampa
Design Firm: Jacobs Civil, Pasadena, Calif.