Readers were stumped by a Patch story that showed a cage floating on the surface of Greenbelt Lake, but Lesley Riddle, assistant director of , has solved the mystery.
Before she started as assistant director in 2007, the City of Greenbelt tried sinking and caging in barley bales to reduce algae. The picture shows one of the cages, which has come loose and floated to the surface, Riddle explained.
Creating a barley filtering system is no longer the city's practice, though, because it would have required an exponential amount of bales, Riddle said. No one knows knows why barley works, but they do know it works occasionally, according to Riddle.
Today, Greenbelt Lake relies on a good buffer that helps filter out surface pollutants and any nutrient load as water enters the lake, Riddle said. The buffer consists of the woods off Crescent Road, grasses on the sides of the lake, and all the vegetation.
"Every green plant you see out there is a buffer to storm water," Riddle said.
Still, if we have a hot, dry summer and not a lot of water, there will be many nutrients; of particular concern are nitrogen and phosphorous. Under these conditions, the algae and hydrilla get worse.
"We hope for a lot of rain," Riddle said.
Greenbelt could use chemicals in an effort to rid the lake unwanted growth, but not without impacting the birds, fish and soil. Riddle is afraid the long-term impact wouldn't have the desired results but would be tough on the environment.
Our desire is to have a lovely, crystal clean lake, but we have to have realistic expectations, Riddle said. Greenbelt does not have a glacial lake with deep waters, it's man-made, she added.
"It is what it is," Riddle said. "You're not going to find perfect ever again."
But given the lower depth of a man made lake, this is an excellent storm water management entity — it does what it's supposed to do, Riddle said. The water coming out of the lake over the spillway is not bad, according to Riddle.
Sometime after Memorial Day, Public Works plans to remove the cage that has surfaced; there's a danger of hypothermia before then if the waters are too cold. Riddle projected that they would send the boat out for it around the end of May.
There are probably other submerged old barley cages as well, but Public Works plans to leave them alone. Disturbing them might cause more problems than it does good, Riddle said. But the city plans to remove them as they become present.