Client: FDOT District 3
Location: Okaloosa County
Project Description:
SR 4 crosses the Blackwater River about 4 miles northwest of the town of Baker in Okaloosa County, FL, and it is a heavily traveled road that is used for commuting and for area agricultural/silviculture industries. Replacement of the Blackwater River Bridge (No. 570033), a Federally-funded project, included an 800’ bridge with approximately ¾ of a mile of approach roadway, was critical for the livelihood and safety of the local residents and industries. The Blackwater River is designated an Outstanding Florida Waters (OFW). The Blackwater River is a State Designated Paddling Trail, and the site is within the Blackwater River State Forest.
The water levels in the river have extreme fluctuations, as much as 12 feet of rise in less than 12 hours. The river is used recreationally, and the site is immediately adjacent to the Cotton Bridge Park where access had to be maintained during all phases of construction.
Prestressed concrete piles (with Test Piles lengths between 100 and 130 feet) were used. The loading demands and geotechnical conditions required the design of deep minimum pile tip elevations. The piles had relatively high cutoffs above ground. Elastic pile rebound conditions made pile drivability challenging for reaching the required penetrations and load bearing capacities while keeping the driving stresses within tolerable limits. A hydraulic hammer with continuously adjustable stroke and energy was used in order to accommodate the challenging conditions and achieve satisfactory pile installations.
Based on the history of the main channel migrating over the past 70+ years, the construction accounted for the potential for future channel migration without compromising the integrity of the bridge and surrounding areas. The work trestle improved safety, mitigated the risk of having equipment wash downstream, minimized impact to the traveling public and potential environmental impacts.
To reduce wetland impacts and to reduce construction costs, the bridge was built in stages rather than using a traditional ACROW bridge with temporary roadway alongside the original bridge. Traffic was maintained on the existing bridge while the new bridge was constructed. Then traffic was moved to the new bridge so the old bridge could be removed. With no temporary ACROW bridge and throw-away temporary pavement and fill, there was a significant reduction in wetland impacts. The staged construction also allowed the public park to remain open during construction as well as the paddling trail.
Because the new bridge was built higher and longer than the original bridge, the bridge is less likely to incur impacts from tropical events or hurricanes and other potential disasters. The bridge was constructed to provide a minimum of 75-year design life. This project will serve the local communities and commuters well into the future.
The project received a 2023 ACEC-FL/ FDOT Outstanding Project Award (Bridge).
Services Provided:
Construction Management & CEI
Construction Administration
QA/QC
Planning & Scheduling
Public Outreach
Performance Dates:
April 2019 to December 2022
Construction Cost:
$10.2 million
