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RON MATUSIf the devices work well, officials might face another problem: how to pay for enough of them to be used citywide.
The big concrete cylinders snag the grit that surfs off city streets.
They're called sediment traps. City contractors are installing nine of them on the ends of stormwater pipes - six at Epps Park along the Hillsborough River and three in Beach Park.
The traps, part of a city pilot project, are supposed to catch most of the sediment carried by stormwater and prevent it from smothering native habitat and clogging canals.
If the traps work as well as expected, the city will have to worry about another problem: How to pay for enough of them to effectively deal with stormwater sediments citywide.
"There are over 500 stormwater outfall pipes in the city limits that outfall into either the river or the two bays," said Steve Seacrist, project engineer with the city's stormwater department. "That's a lot."
And the devices don't come cheap.
The first nine cost $449,000 to buy and install. Sixteen more are slated to go in by early next year.
Some stormwater pipes are so massive - one culvert in Epps Park is 8 feet wide and 4 feet tall - the sediment traps won't fit on them. Instead, they must be placed on the ends of feeder pipes, which means some lines need several devices each. At that rate, putting a trap on every pipe that needs one could cost the city tens of millions of dollars.
"It's a problem that will have to be chipped away at," Seacrist said.
The devices look like giant concrete barrels, ranging from 6 to 10 feet in diameter and as much as 5 feet deep.
As water pours through a stormwater pipe into the trap, it strikes a tiny dam, which forces sediment to fall and collect in the bottom. The water continues through the pipe.
For the traps to be effective, sediment must be removed about every six months, Seacrist said.
The South Tampa devices will be installed in March near Neptune Way, Shorecrest Drive and Bayside Drive.
For the next round, 13 of 16 devices will be installed in the South Westshore area.
The cost: about $1.2-million. The city's share is $750,000, with the rest of the money coming from county and state agencies.
In a related pilot project, city contractors recently installed other concrete devices - called sediment sumps - in the bottom of creeks near North Dundee Street and Woodmere Road. Shaped like coffins, the sumps work like the sediment traps, except they capture sediment when water flows over them. That project cost about $99,000.
The traps and sumps are part of a settlement reached last year with the Environmental Protection Commission regarding the South Westshore area.
Residents have complained for decades that the buildup of sediments in area canals has been unsightly and made it difficult to navigate boats. The traps and sumps won't do much - considering how much sediment has accumulated - but they're a start, the residents say.
"The intention is there," Sunset Park activist Ellie Montague said.
- Ron Matus can be reached at 226-3405 or matus@sptimes.com