Runoff, yard waste choking Lake Gerar

The head of Rehoboth Beach's environmental consulting firm says runoff and overgrown vegetation have caused Lake Gerar to fill up with organic material, decreasing the water depth of the lake.

Todd Fritchman, head of Envirotech, said sediment is building up in Lake Gerar in the area near Rehoboth's City Hall complex. He said that end of the lake has lost its water storage capacity, mainly due to construction runoff and lakeside homeowners dumping yard compost into the lake.

Fritchman said it's a problem because Lake Gerar serves as a stormwater basin for the city.

"Anything that goes into the lake - oil, gas, antifreeze, droppings, silts and sediments, dog feces, the organic materials - whatever travels down into this lake becomes nutrient," he said "It's a nutrient sink to hold that material before it goes out into the ocean."

The mix of algae and bacteria that grows in the nutrient is a negative because it can lead to fish kills, Fritchman said, doubly discouraging because Lake Gerar has become a good fishing spot since its restoration 10 years ago.

Commissioner Stan Mills said, "The depth seems to be getting shallower. You can see fish in the summertime swimming through the mud with their fins sticking out. If we let it continue this way, would the vegetation fill in the buffer where the storm drain pipe goes in?"

Fritchman said material going into the lake has formed layers upon layers on top of one another, forming a peat bog, which Fritchman described as partially decomposing organic material. In addition, vegetation installed as a buffer, intended to stabilize the lake shoreline, is overgrown and now sprouting into the lake.

"In a natural world, that's not a bad thing because you're creating habitat, but this is another contributing factor that never ends for that organic material going in there," he said.

Fritchman said the overgrown buffers can easily be corrected by spray treating. That will only improve the aesthetics, he said, but not the water depth. "This will have to be dewatered and dredged out," he said

He said the water quality of the lake is good, thanks to protections installed 10 years ago, including diffusers to break up bacteria and algae, and herbicides applied to keep out invasive species like phragmites.

In an aside, Mayor Sam Cooper said at one time Lake Gerar served as a trash dump for the city's maintenance garage, on Olive Avenue at the time.

"In those days, they thought they were doing something good. They thought they were filling in an area that would be useful someday," he said

"Back in the olden days, wetlands were considered wasteland, and it was common practice to dispose of things. Out of sight, out of mind," Fritchman added.

The city commissioners have tasked Fritchman and City Manager Sharon Lynn to come up with a plan to treat the vegetation that has grown into the lake, to improve the aesthetics in the short term. Long-term, Mills said, the ultimate solution is likely to be dredging the southwest end of the lake, similarly to how the western finger of Silver Lake was dredged in October.