Plenty of trash can accumulate on 2,400 acres of urban land. That's the size of the watershed — almost 4 square miles — that flows into Clam Bayou. And, right now, most of its trash and pollutants flow practically unabated into the bayou, an estuary on Boca Ciega Bay that borders Gulfport and St. Petersburg.
Soda cans, plastic bottles and other pieces of trash that have washed down become lodged in the mangrove trees and other vegetation growing in the bayou. The trash flows through the estuary on moving water or deposits itself on the banks of retention ponds during low tide. It turns a place of beauty into a junkyard.
But all that is about to change.
A yearlong project is under way to restore the bayou and to treat the stormwater that runs into it.
Partners in the project, which began in May, include Gulfport and St. Petersburg, the Southwest Florida Water Management District and the Florida Surface Water Improvement and Management Program.
When it's done next May, 24 acres of coastal habitat will be restored and 20 acres of ponds will be built to help filter pollutants in stormwater runoff.
Brandt Henningsen, SWIM environmental scientist, and Janie Hagberg, SWIM engineer, recently checked out the progress at Clam Bayou.
They said the project is moving along on schedule.
The first of seven project areas has been completed. Spoil mounds on the northern end of the bayou have been leveled and non-native vegetation growing on them removed to improve water flow in the bayou. Spoil mounds are simply piles of dredged matter from past work on the bayou. Non-native vegetation — mostly Brazilian pepper trees — sprouts on them, hindering water flow.
These particular spoil mounds were made in the 1950s when all of Florida was digging mosquito ditches in an attempt to make paths that would entice fish to come and eat the mosquito larvae, Henningsen said. It seemed like a good idea at the time, he said, but it didn't work.
Work has moved to the second project site, where bulldozers and backhoes are enlarging and reconfiguring a retention pond on the north end of the bayou.
Hagberg, the project's engineer, explained that the pond had to be bigger and deeper to handle the water flowing into the bayou from the north and the east.
"The ponds will reduce floatable objects by 99 percent," Hagberg said. The outflow area of the ponds will be fashioned in such a way that trash gets hung up there to then be picked up by workers.
"You will immediately be able to notice the lack of trash. Water quality improvement takes a little time," Hagberg said.
The ponds allow the pollutants to sink to the bottom. Dredging about once every five years, Hagberg said, will remove them.
As these projects continue, Henningsen and Hagberg look toward the next steps. They are:
• Construction of a central stormwater retention pond. This is to be built on the eastern edge of Clam Bayou, near 38th Street S. The pond will collect stormwater to cleanse it before it is deposited in a new intertidal lagoon and then into the bayou.
• Construction of a south stormwater retention pond near 32nd Avenue S. This pond will also function as a freshwater wetland.
• Channel restoration. This project will reconfigure a drainage ditch and spoil berm in the center of the bayou. It is covered with non-native vegetation that will be removed to create a tidal channel that will provide a habitat for bayou marine life.
• Central restoration. Fill material and non-native vegetation will be removed in this area in the middle of the bayou near 32nd Avenue S. Upland islands, tidal passes and an open-water lagoon will be created. It is hoped that this will take the place of the open-water habitats that used to be present in the bayou.
• Southern restoration. Non-native vegetation will be removed and a new tidal lagoon created. It is hoped that this area with its freshwater runoff will be a place for fish to spawn.