The water-filled shell mining pit once was a stagnant dead zone, home to pea-green algae blooms that killed everything that swam.
These days it is a thriving lake, home to fish and birds, including roseate spoonbills, glossy ibis and tricolored herons. A bald eagle nests nearby.
"I can't believe there's mangroves popping out in here," county conservation services manager Ross Dickerson told a colleague during a tour last week. "That's awesome."
That rebirth is possible only because Hillsborough County spent $3-million buying more than 1,000 acres on Cockroach Bay through the Environmental Lands Acquisition and Protection Program.
And supporters of ELAPP hope to see more projects like it. Hillsborough County voters will decide whether to renew the program and authorize it to borrow up to $200-million for future environmental purchases.
The debt would be repaid through the continuation of an existing property tax the county collects just to buy and preserve land. The referendum is Nov. 4, though early voting goes from Monday through Nov. 1.
Since its creation in 1987, the ELAPP tax has made possible the purchase of 44,700 acres of beaches, woods, swamps and grasslands throughout Hillsborough County.
Those purchases totaled $204-million. Of that, the county paid $128-million. The other $76-million came in matching grants from the state and other sources.
But advocates say the program has identified another 44,000 acres in Hillsborough eligible for purchase. Preserving the land, supporters say, protects drinking water, improves water quality and safeguards habitats for wildlife.
With real estate prices dropping and the county's population expected to nearly double by 2050, they say now is the time to save irreplaceable habitats.
"Right now, all you have to do is turn on your TV and see there are a lot of willing sellers out there," said former Hillsborough County Commissioner Jan Platt.
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Along with former Gov. Bob Martinez, Platt is co-chairing the campaign to extend the ELAPP tax. That's fitting, because she pushed for the program in the first place.
The tomboy daughter of a guy who loved the outdoors, Platt, 72, grew up fishing all over Tampa Bay.
Now she mourns the loss of the bay she knew. She recalls watching otters frolic in Town 'N Country's Sweetwater Creek - the site of a 1.8-million-gallon sewage spill last week - and once spotted a prehistoric-looking sawfish in the bay.
"I don't know what happened to those sawfish, but they're not in Tampa Bay anymore," she recently told a downtown meeting of the Kiwanis Club.
As a county commissioner in 1987, Platt worried about the fate of the old farmland and shell mines near Cockroach Bay. Tampa Electric Co. was talking about building a power plant on the shore. Development seemed likely.
The only way to protect wild land, Platt concluded, was for government to buy it.
So she proposed creating a tax to buy preservation land. More than 70 percent of voters said yes. In 1990, a similar margin of voters agreed to extend the tax.
Anyone can nominate a piece of property for an ELAPP purchase. A citizen's committee reviews the nominations, and the program is audited annually.
"There's never been any hanky-panky going on with this program because the citizens have kept a sharp eye on it," Platt said.
The tax is scheduled to expire in 2011, but supporters decided to bring it up for renewal now. That way, if voters reject the tax, it can be brought back for another vote in 2010.
So far, public opposition has been limited to a few letters to the editor.
One of those writers, Daniel Rich of Apollo Beach, said he plans to vote against the tax because ELAPP's impact is not as simple as it seems. Purchased land is taken off the tax rolls, he said, so other taxpayers have to make up the difference.
"You have to go out and maintain it," said Rich, 57, a general contractor. "That means you have to have more manpower and equipment. You have to have insurance, which is expensive."
That there aren't more people like Rich speaking up has supporters hopeful, though they worry voters might not find it at the end of their ballot.
"We really don't have any organized opposition, which is a good thing," said Heidi McCree, president of the nonprofit Tampa Bay Conservancy. "The biggest challenge we have is that people don't even know it's on the ballot."
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One of ELAPP's main selling points is that this is not a new tax, but the renewal of an existing one, supporters say.
For the county's 2008-09 budget year, which started Oct. 1, the ELAPP tax rate is about 0.06 mills. That's $12 a year for a homeowner whose tax assessment is $200,000 after homestead exemptions.
"The tax itself is a continuation and is just a pittance in the scheme of things," Platt said.
Another selling point in the past was that the tax is capped at a quarter of a mill, or 25 cents in taxes for every $1,000 of assessed, nonexempt property value.
But if the referendum passes, the cap would go away.
The reason: the skittish bond market.
Even before this fall's global financial crisis, investors were increasingly wary of putting their money in tax-supported bonds with limits on how much the county could raise through the tax.
Still, officials don't expect to have to raise the tax above the current cap to repay the $200-million in bonds.
"I think realistically (the tax rate) would not exceed a quarter-mill anyway," said Michael Merrill, the county's debt management director.
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At Cockroach Bay, ELAPP's purchases took place over 17 years. They included not only the old shell mine, but farmland and shoreline.
Counting the state-protected submerged areas just off shore, the Cockroach Bay Aquatic Preserve encompasses more than 8,500 acres of critical aquatic habitat.
The preserve is open, like other ELAPP properties, to the public for fishing, canoeing, hiking, picnicking and other passive recreation.
The county's land has been restored through an ambitious series of partnerships with other agencies. New marshes and woodlands were created. A ditch now connects the old shell pit to other waterways, improving its circulation.
The goal: to create migratory bird habitats.
It worked. Preserve manager Richard Sullivan gives bird-watching tours of the property. He didn't do that when he started nine years ago because there weren't as many birds.
The preserve also attracts scientists.
"We have two professors from Eckerd College doing research," said Dickerson, the county's conservation services manager. "One's doing a study on fiddler crabs. One's doing a study on snails. It's a researcher's dream out here."
On Wednesday, bird experts from Quest Ecology and the county teamed up to see what migratory birds were passing through on their way south for the winter.
Their finds included an ovenbird and an American redstart, two of 40 species they've found so far.
"Both of these birds are forest-dwelling," Quest ecologist Lauren Deaner said. If Cockroach Bay hadn't been preserved, "they would not have stopped."
Times photographer Lara Cerri and researcher John Martin contributed to this report. Richard Danielson can be reached at Danielson@sptimes.com or (813) 269-5311.
Notable ELAPP preserves
BALM-BOYETTE SCRUB NATURE PRESERVE
Location: Lithia, off of Balm-Boyette Road.
Features: Hiking trails, 18 miles of mountain bike trails, and is adjacent to the Triple Creek Nature Preserve, which has more trails.
BROOKER CREEK HEADWATERS NATURE PRESERVE
Location: Lutz, east of Gunn Highway between Lutz-Lake Fern and Van Dyke roads.
Features: An important aquifer recharge area, the preserve is 60 percent wetlands, but is open to hikers.
CYPRESS CREEK NATURE PRESERVE
Location: Lutz, off Livingston Avenue, just south of the Pasco County line and west of Interstate 275.
Features: Cypress Creek, a tributary of Hillsborough River, diverse wildlife. No trails, but hiking allowed on internal roads.
Still on the wish list
Location: Bloomingdale, on the Alafia River, south of Bloomingdale Avenue near Watson Road.
Owner: Mosaic Fertilizer LLC.
Location: On the Alafia River, near Lithia Springs Road.
Owner: Mosaic Fertilizer LLC.
Location: Lutz, at the southwest corner of Van Dyke Road and N Dale Mabry Highway.
Owner: city of St. Petersburg.
Location: Odessa, south of N Mobley Road and west of Gunn Highway.
Owner: city of St. Petersburg.