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South Tampa drainage project relies on tunnels, not trenches

SOUTH TAMPA — Two years ago Palma Ceia residents successfully fought city plans to route a stormwater pipeline through their leafy neighborhood.

Now the city is launching a new effort to relieve the flood-prone intersection of S Dale Mabry and Henderson Boulevard.

Rather than digging up streets to place pipelines in a trench, the city proposes tunneling 30 to 40 feet below streets to avoid disrupting residents or jeopardizing trees.

"All of it will be in the right of way; it is not going to be under anyone's house," said Stephen Daignault, the city's public works and utility services administrator.

Pipelines would carry stormwater west to Old Tampa Bay, rather than east to Hillsborough Bay, as in the 2007 plan.

Stormwater would be discharged below the surface of a canal on the north side of Culbreath Isles, rather than cascading from a visible outfall pipe.

Daignault said sediment traps near West Shore Boulevard would remove about 90 percent of the dirt and other debris that typically flows into the canal.

The proposal calls for up to three pipelines from Dale Mabry to S Manhattan Avenue. Engineers still must determine whether pipelines would be tunneled beneath W Morrison Avenue, W Watrous Avenue, W Neptune Street, or all three streets, Daignault said.

From Manhattan west to the bay, the proposal calls for funneling the stormwater into an approximately 8-foot-diameter pipeline located parallel to, or below, Watrous.

The tunneling would require up to six pits for storing dirt until it is trucked away.

City officials are set to brief neighborhood leaders from the west of Dale Mabry about the project on Feb. 16. The city also plans to meet with Palma Ceia residents four days earlier to assure them the 2007 proposal is not coming back to life.

"With the information I've seen so far I'm pretty excited about the project," said council member John Dingfelder. "It looks like it's going to solve a long-term problem with minimum disruptions."

The project's estimated cost is $27 million, about $3 million more than the 2007 proposal. Under the new proposal, the city won't incur the costs of replacing streets or trees that would have been damaged under the old proposal.

Daignault said the city has about $9.8 million in grants on hand for the project, with the balance coming from capital improvement funds.

The council is likely to consider next month whether to move forward with seeking more detailed engineering plans.

South Tampa drainage project relies on tunnels, not trenches

01/29/09 [Last modified: Thursday, January 29, 2009 3:30am]

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