The Florida Department of Transportation has come up with a unique solution to help restore water quality and habitat in Tampa Bay: removing over 200 feet of a land bridge known as the Courtney Campbell Causeway.
The Old Tampa Bay Water Quality Improvement Project – which involved cutting out a portion of the 86-year-old causeway and replacing it with a new water channel and bridge – is already showing beneficial results, according to Daniel Lauricello, District Roadway Engineer, and Virginia Creighton, Environmental Permits Coordinator with the Florida Department of Transportation, District 7.
Completed in November 2018, the project used a whole-system approach. By focusing on the whole watershed rather than project-by-project solutions, FDOT was able to leverage the benefits of the causeway project to address requirements for stormwater management and sea grass mitigation from a related project. This provided the opportunity to accomplish more while also saving money in the long run, according to Lauricello.
The Courtney Campbell Causeway has been in place across Tampa Bay since 1934. Over the decades, Tampa’s population has continued to grow, resulting in an increase in pollutants such as nitrogen being discharged into the bay. Florida has designated Tampa Bay as an impaired water body.
Growth also requires that FDOT maintain and improve the transportation system. The Howard Frankland Bridge, which traverses Tampa Bay just south of the Courtney Campbell Causeway, is part of that system and is scheduled for reconstruction. FDOT estimated that it would need to spend about $60 million to purchase additional right-of-way for stormwater management, plus another $3.4 million for sea grass mitigation, as compensation for the bridge project.
Stormwater retention and detention ponds are commonly used for containing runoff before it can reach the bay. In highly urbanized areas such as Tampa, however, there are very few undeveloped parcels on which large stormwater management facilities can be built, and FDOT would pay a premium to purchase the right-of-way.
The solution developed by FDOT and its partners was to strategically excavate 229 feet of the causeway and replace it with a bridge. Opening the causeway has reestablished tidal circulation around the eastern end of the causeway, improved water quality, and is anticipated to support sea grass growth while helping FDOT meet its stormwater management commitments.
The Old Tampa Bay Water Quality Improvement Project cost approximately $12 million but has provided a $50 million net benefit due to the significant reduction of stormwater management for the Howard Frankland Bridge project. “The project is expected to ultimately save as much as $100 million in stormwater right-of-way costs for future projects in the Tampa Bay Area, while accelerating delivery of future projects with available water quality compensatory treatment and sea grass mitigation credits. The project does not eliminate stormwater retention and detention ponds, but significantly reduces their size,” Lauricello said.
The impairment classification of Tampa Bay means that transportation projects in the area also must find ways to improve water quality.
The bay overall has improved over the last 20 years, thanks to the work of the Tampa Bay National Estuary Program and a consortium in the municipalities surrounding the bay. The consortium, known as the Tampa Bay Nitrogen Consortium, has developed a number of programs to reduce polluted runoff, such as constructing stormwater treatment facilities and restoring natural wetlands. However, the Old Tampa Bay segment, where the Courtney Campbell Causeway is located, continued to have poor water quality due to decreased tidal circulation.
“Causeways sever the natural circulation of the water bodies that they pass through,” Lauricello said. This one created areas of poor sea grass growth, elevated nitrogen concentrations, and high salinity. Opening the causeway appeared to be an optimal solution.
Sea Grasses and Marine Life
To plan for the project, a team lead by Virginia Creighton studied water quality and hydrodynamics of the bay waters surrounding the causeway. “That provided us with the best location to truly restore the historical flushing of the area,” Lauricello said.
The studies were an investment in up-front research and proof of concept. For example, they predicted that sea grass populations would recover with improved water circulation. Sea grasses are important to the overall health of the bay. They stabilize the bay bottom, trap fine sediments, shelter small sea life, and provide food for larger animals such as manatees.
When the causeway removal was completed, water quality improved almost immediately. Studies about a month after it was finished showed that tidal flows were restored, and ongoing water quality monitoring has shown very positive results. The benefits were sufficient to allow FDOT to receive the stormwater treatment credits for the Howard Frankland Bridge project, which is set to begin construction in 2020.
“The project was broadly embraced by the Tampa Bay environmental community,” Lauricello said. Fishing has improved and marine life has been observed passing through the new channel. FDOT will monitor the recovery of sea grass in the area for the next few years.
Causeway removal projects have been implemented elsewhere in Florida—in Pinellas and Volusia counties and on Key Largo—with positive results.
The project demonstrated the importance of having an atmosphere of innovation, prudent risk taking, and systems thinking, according to Lauricello. It is an outcome of a departmental initiative known as “Environmental Look Arounds,” an initiative to get the right people together to find creative solutions.
Also, FDOT developed a new statewide stormwater management process that encourages collaboration, breaks through regulatory constraints, and motivates FDOT staff to pursue stormwater joint ventures with others while balancing social, environmental, and economic objectives.
“The project shows that systems thinking really does work,” Lauricello said.
Additionally, support from leadership is critical to these kinds of successful projects. FDOT approved the spending on the proof-of-concept studies and supported the necessary investments of time and funds to develop new solutions that ultimately are saving money and providing results.
Lauricello recommends that other DOTs consider causeway removal as a viable water quality tool. “In the right conditions, with the right study and proof of concept, this is a definite benefit to the environment,” Lauricello said.
FDOT has issued a state-wide guidance for developing stormwater management practices that features the Old Tampa Bay Water Quality Improvement Project and other similar innovative approaches as best management practices and viable options over more traditional stormwater management approaches.
The project received a 2019 Environmental Excellence Award from the Federal Highway Administration, along with the 2017 Florida Institute of Consulting Engineers/FDOT Outstanding Environmental Project, the 2019 American Society of Civil Engineers Florida Project of the Year Award, and the Tampa Bay Regional Planning Council Natural Environment Award (2019).