Summer algae growth in stormwater ponds throughout the Lowcountry are a sign they're doing their job: absorbing runoff containing gasoline, oil, pet waste, fertilizer, garbage and varnish.
Controlling pond algae
There are a number of steps homeowners can take to keep the algae in check in the ponds:
Test soil to prevent over-fertilizing, and blow fertilizer off roads and driveways into the grass to prevent it washing into the ponds.
Don't throw grass clippings or yard waste in ponds or ditches.
Pick up pet waste and throw it in the trash.
Don't wash cars in driveways.
Don't feed fish, turtles or waterfowl; the food essentially fertilizes the pond.
Plant pond shorelines with wetland plants to filter run-off.
Install floating wetlands to use up nutrients in the pond.
Consider aquatic dyes to suppress some algae growth.
Source: Clemson Extension Cooperative Service.
Algae forms from the nutrients the runoff brings, helping to absorb the pollutants to keep them out of the creeks and streams. Except that makes more algae, which can end up coating the pond with slime and killing everything else in it. Keeping that from happening takes ongoing maintenance - killing enough algae to keep down the scum without killing it all off, aquatic specialists say.
That's an ongoing cost for homeowner associations scraping by on regime fees. And the build-up of toxic sediment in the pond is a high-dollar hazardous substance removal job waiting to happen.
And those are not even Ted Yeager's immediate problems. Yeager is treasurer for the Bridgepointe Homeowners Association in West Ashley, a circle of 32 duplexes that are bordered on one side by two connected, algae-scummed ponds. The association had treated the ponds, paying $140 per month out of fees, Yeager said. Then a records check dumfounded him: The association doesn't own either one.
One pond is owned by an adjoining association; the other by a private absentee owner, who apparently bought it even though it's not developable.
"We'd been treating it for years, but legally we had to stop," Yeager said.
Stormwater ponds, like their problems, are endemic. The ponds have become the standard for handling rain runoff at residential and commercial developments in the past quarter-century. Nobody has a firm total on the number of the ponds in the Lowcountry today, but there were more than 8,000 built just along the South Carolina coast east of U.S. 17 by 2005, when the S.C. Department of Health and Environmental Control did a survey for a review of management rules. Charleston officials say there are now more than 800 of the ponds in the city's jurisdiction alone.
They cause problems from chronic toxic algae blooms to what DHEC in 2005 described as $500,000 community cleanups. The pollutants leach into the groundwater. They settle layer upon layer across the bottom until the ponds have to be dredged and the sludge removed, according to DHEC.
"Frankly, (stormwater) retention ponds are almost a necessary evil," said Charleston Councilman Dean Riegel, who is a public water commissioner for the city. "You have to mitigate runoff. But with petrochemicals, herbicides and pesticides and who knows what else running off into those ponds, it's a witches' brew. That's a real risk."
How well the ponds are kept up varies. At least a small percentage are owned individually rather than by a homeowners association.
Yeager said property owners see the scum as unsightly and trouble for property values, but tend to assume the upkeep is somebody else's job.
"You know people don't pay a lot of attention (to details)," he said.
The city regularly gets calls about cleaning up the ponds from residents who believe they are public property because they provide public drainage, Riegel said. But by and large the city holds only drainage easements in the ponds, and is responsible mostly just to make sure they drain.
"It's been a thorn," Riegel said about the extent of the problems.
On top of that, the algae itself can be or can become toxic - enough of a risk that Clemson University Cooperative Extension Program cautions homeowners to be careful handling it or its cleanup. The general recommendation is to hire professionals to do the work, Riegel said.
The ponds are more than just problems. Algae lives in every drop of pond water, Clemson Extension notes. It produces oxygen and the base line food for animals that live in the water. In other words, it can be the difference between an ecosystem that's full of fish, turtles and aquatic plants, and one that's dead. Even as Yeager said on a recent morning that the subdivision pond looks dead, turtles swam in it.
Algae maintenance doesn't always mean herbicides, said Laura Cabiness, Charleston Public Service director. Other methods include introducing plants and animals such as sterile carp.
"The ponds don't have to be an eyesore. They can be an asset. But they do take maintenance," said Laura "You have to control the right levels of all the life in the pond. It's a balance and there's a number of companies that have been certified by DHEC. It's cost effective, so long as people keep up with it."
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The surface of a pond near the Bridgepointe neighborhood in Shadowmoss Plantation is filling with algae since the neighborhood association that used to treat it discovered it could no longer continue.×
Ducks swim in with the algae coating in a pond near Bridgepoint in Shadowmoss Plantation.×