FDOT moving ahead with new solution to stormwater pollution

Image courtesy ESA. Map depicts current seagrass abundance in the section of Old Tampa Bay.

Work on a “look-around” solution to water quality continues at the Florida Department of Transportation where nearly all necessary permits have been completed for a 239-foot bridge that will enhance tidal flow to the bay section north of the Courtney Campbell Causeway.

Originally proposed as part of the Tampa Bay Express project, the bridge is expected to lead to water quality improvements and the anticipated seagrass gains will now be used as mitigation for multiple FDOT projects across the region.  The $10.5 million project will be less expensive than the traditional go-to retention pond solution to stormwater management in a region where available land is growing scarcer – and more expensive.

“We expect this to reduce the cost of stormwater ponds by about 40%,” said Virginia Creighton, permit coordinator for FDOT District 7. “Nitrogen removal is very difficult in areas with high water tables and we cannot increase nitrogen above background levels.”

Water quality and composition of seagrass species will be compared in the area furthest west (now mainly red) with the area south of the causeway to access the impact of the new bridge. Image courtesy ESA.

FDOT consultants expect it to have a significant impact on the water quality in the area north of the causeway where seagrasses species are limited because of low salinity. The cut in the bridge is expected to nearly double tidal flows to the section of Old Tampa Bay north of the Courtney Campbell Causeway, increasing the potential for other seagrasses to recruit into what is currently a monoculture of wigeon grass (Ruppia maritima), a pioneer species more tolerant of lower salinity but a less extensive root system.

Drivers traveling across the scenic Courtney Campbell Causeway may not notice the new bridge structure, which will be just west of the Ben T. Davis Beach. The new structure will be even with the existing roadway, so the opening will not be navigable for boaters to go between bay sections. Success will be measured by seagrass recovery and comparing species composition to an area south of the causeway where man-made structures have had less of an impact on tidal flow, notes Creighton. All lanes on the causeway, as well as Courtney Campbell trail, will be open during the entire period of construction, she added. Users of the trail will be able to check out educational signage which will be in place during the construction.

FDOT is currently in the process of hiring a design-build contractor with construction expected to begin this fall. Stay tuned to Bay Soundings as this exciting project progresses!

Learn more about the project at http://baysoundings.com/out-of-the-box-mitigation-efforts-may-include-a-bridge-not-a-stormwater-pond/.

Share this page →Share on FacebookShare on Google+Share on LinkedInEmail this to someoneTweet about this on TwitterPin on PinterestShare on Tumblr