MacDill Wages War on Stormwater Pollution

The year was 1939. War was raging across Europe and US officials feared that Nazi submarines could attack shipments of war goods to England. Of particular concern were oil tankers in the Gulf of Mexico, carrying fuel from refineries in Texas and Louisiana. To help protect them, MacDill Air Force Base was constructed, with hundreds of troops living in a mosquito-infested tent city while the first barracks were being built.

Like nearly all development in Florida at the time, the primary consideration was getting stormwater off the low-lying land as quickly as possible. A straight-shot canal was dug from the main part of the base with its massive runways directly to Tampa Bay, and mosquito ditches crisscrossed the mangroves at the southern tip of the base to make life more comfortable for the troops stationed there.

Fast-forward 60 years, and MacDill officials are rethinking those long-ago decisions and rebuilding their waterways to function more naturally.  Instead of moving water as quickly as possible, they’re restoring natural systems where stormwater meanders through man-made lakes and mangrove forests so nutrients are removed before they hit the bay. This also provides the low-salinity habitat that’s necessary for many fish species to survive.

The base’s two golf courses located at the southern tip of the Interbay Peninsula – one of the region’s most densely populated areas – offered unique opportunities for habitat restoration, notes Jason Kirkpatrick, natural resources program manager at the base. “With seven miles of shoreline, there aren’t many open spaces like this directly on the bay,” he says.

[easy-media med=”324″ size=”250,250″ align=”right” style=”transparent”]In partnership with the Southwest Florida Water Management District’s Surface Water Improvement and Management (SWIM) program, the third phase – and by far the largest – of a multi-year project was recently completed. Covering much of the southeastern portion of the base, the latest work focused on opening tidal flows, removing dense stands of Brazilian pepper and reshaping existing ponds to expand habitat for birds and small fish.

All together, the construction footprint spanned 100 acres, including the restoration of 9.6 acres of wetlands, the creation of 22 acres of new wetlands and 16 acres of enhanced surface waters. Most of the funding came from SWIM’s $1.8 million contribution, with additional funds from the Estuarine Restoration Council for the 1997 Mulberry Phosphates/Alafia River spill ($250,000), the National Fish & Wildlife Foundation ($200,000), and the Department of Defense ($350,000).

The golf courses and Lewis Lake – a permitted stormwater pond – were redesigned to enhance habitat for wildlife and remove nutrients from stormwater. On the south course, new tidal connections created more than 10 acres of low-salinity habitat connected to the base’s wastewater treatment ponds, including two newly lined ponds to help ensure that freshwater is available year-round.

Existing ponds also were improved with new tidal connections and wider littoral shelves where native plants absorb pollutants. The wider shelves also provide enhanced habitat for small fish and the birds that feed on them.

“Before construction began, you could look across the entire lagoon and not even see water because the Brazilian pepper was so dense,” notes Nancy Norton, the engineer who directed the restoration for SWFWMD. “There were a few stands of native Sabal palms which we were able to transplant, but it was mostly a solid forest of Brazilian pepper.”

Across the board, the project was strongly supported by Air Force officials, golf course management and even golfers who had to play around construction sites, Norton adds.

“We knew we could make a difference from an ecosystem perspective, but the response from people who use the course has been great,” Kirkpatrick said. “We had one golfer tell us what spectacular views it has now that it’s opened up.”

Work on the south course primarily focused on restoring 34 acres of degraded mangrove estuary which had been cut off from tidal flow when the golf course was originally constructed. Along with re-opening the tidal connection, thousands of overgrown Brazilian peppers were removed and pond edges replanted with native marshgrasses.

On the north course, stormwater that once flowed directly into Tampa Bay is diverted through a series of freshwater and low-salinity ponds. “Slowing the water down increases retention time and provides longer contact with the aquatic plants that naturally absorb pollutants from the stormwater,” Kirkpatrick notes.

A larger Lewis Lake also benefits both ecosystems and the people who use them. Its shape was modified so that water stays in the lake longer and the creation of land bridges and fingers increases fishing opportunities in the popular spot.

MacDill’s seven-mile shoreline, which is off-limits to most recreational boaters for security reasons, also serves as a testing ground for other restoration initiatives. Tampa Bay Watch, working with MacDill personnel and their families, has installed nearly 8,000 domes to limit erosion and provide habitat along with more than 1,120 feet of oyster shell reef.

Another ongoing study along MacDill’s shoreline looks at the impact of longshore bars on seagrass recruitment, particularly along the shoreline where the wakes of large ships increase wave action. Researchers hope to see increased seagrasses behind the bars where the bars provide protection from heavy wave action.

“There has been some natural recruitment of seagrasses but we’re not able to see a strong correlation between the bars and the seagrasses,” notes Lindsay Cross, environmental science and policy manager at the Tampa Bay Estuary Program. “We do see a lot of fish and crabs using the bar, as well as many birds.”

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This is part of a series of stories called “Elephant Bites,” that looks at innovative designs local governments and developers are using to capture nutrients before they enter surface waters. Learn more here.

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