SEMINOLE — Environmental experts, always concerned about the water quality of Lake Seminole, are assessing how much Hurricane Irma may have stirred up the nearly 1 million cubic yards of muck that lay on the bottom.
"There are so many nutrients stored in those sediments," Pinellas County Environmental Management division director Kelli Levy said. "Every time they get stirred up, it's like releasing fertilizer into the water column that speeds up algal bloom."
This latest concern regarding the 684-acre lake comes two months after Pinellas County commissioners agreed to move forward on a $19 million dredging project, half of which will be paid for by the Southwest Florida Water Management District, that will remove 416 tons of nitrogen and 77 tons of phosphorus from the lake.
While design and permitting are under way, actual dredging is not expected to begin until next August and will not be completed until 2023.
County Commission chairwoman Janet Long, whose history with the lake dates to her tenure as a Seminole City Council member, said she is pleased that a resolution finally is in sight.
"We expect this project will return the lake to a condition where it will support recreational and commercial use,'' Long said.
The county has been wrestling with how to improve the lake's water quality for more than two decades. The seeds of the dilemma were sown in the mid 1940s, when commissioners decided to create a freshwater lake on the arm of Long Bayou that would serve as a source of irrigation for citrus groves as well as for recreation.
"It was doomed from the day it became a lake," Levy said. "We took a saltwater system and converted it into a freshwater system that has no source of water other than rainfall. Basically, we ended up with this big bowl of water sitting on top of muck."
Construction of the Seminole Bypass Canal along Long Creek basin in the late 1970s alleviated flooding but created what experts call hydrologic isolation. An outfall pipe was built to provide flow into the lake to prevent stagnation, but in the meantime, the decreased flow of fresh water caused changes in water quality that contributed to algae bloom.
As the land surrounding the lake was developed, storm water carrying lawn fertilizer and motor oil washed into the lake, creating an overabundance of nutrients, further feeding algae bloom.
Tom Champeau, a director with the state's Division of Freshwater Fisheries Management, likens the situation to what happens when a person overeats.
"A good thing can go too far," Champeau said. "If you don't curb your appetite, you get obese. If the supply of nutrients isn't curbed, a body of water gets overly fertile with green algae."
Amid complaints that the water was turning green and that there were fewer fish, the county developed a plan in 1989, but water quality and fish reproduction continued to deteriorate drastically over the next eight years.
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The county hired a consultant in 1998 who found 4.9 million cubic yards of loose sediment in the lake and recommended that 850,000 cubic yards be dredged. Cost of the project was estimated at $6 million.
But finding a suitable place for the dredged-up sediment proved a challenge. Largo city leaders balked at the county's plan to pump it to a landfill near East Bay Drive where it would be treated, citing odor from the drying sediment and heavy traffic from trucks transporting it.
Over the next two years, county staff found an alternate site for the sludge — 15 acres of county-owned land in an industrial area south of Ulmerton Road — but by that time, the amount of sediment had increased to 930,000 cubic yards, and the cost to remove it had risen to $9.7 million.
The county continued to pursue other remedies proposed by the Southwest Florida Water Management District, known as Swiftmud, for improving water quality, spending $7 million in 2005 to lower the lake and scrape muck from areas near the shore. In 2008, the county embarked on a $6.5 million project to clean storm water on its way to the lake, including construction of a stormwater treatment plant.
Champeau describes the county's strategy as a two-fisted approach to both head off and eradicate the ever-encroaching sediment, which he compares to sludgy chocolate milk.
By 2010, in the wake of projects totaling more than $30 million funded by Penny for Pinellas dollars, Swiftmud and federal and state sources, county commissioners expressed frustration that water quality in Lake Seminole still was not up to par. They turned their attention once again to dredging, budgeting $16.7 million for the project.
This time around, the challenge was finding a company that could complete the job within the budgeted amount. One bid came in at nearly four times the estimated project cost, and a second exceeded the engineers' estimate by $10 million.
Fast forward to 2017, when dredging technology has advanced to the point where processing the sediment requires a much smaller footprint and can be accomplished at a more manageable cost.
When dredging begins next summer, the muck will be pumped out of the lake and will remain in the park in a "designated management area" just south of 102nd Avenue rather than being transported to an industrial site.
"That area will be built up, seeded over and grassed," Levy said. "It will be a big dirt pile about 15 acres wide and about 20 feet tall that will settle out over a period of about five years."
Eventually, the berm-like area could be used as a soccer field or for disc golf, Levy said.
But, she cautions, regardless of how much effort the county and other agencies expend, there is no perfect fix for the lake.
"When all is said and done, Lake Seminole will not be a crystal clear lake," she said, adding that the goal is to bring it to a place where it supports healthy native vegetation and native fisheries — without needing to be dredged again "for many lifetimes."