State officials took a plan to dredge Silver Lake to Cape Henlopen school board Dec. 13, asking permission to use school property to store dredge spoils.
The Department of Natural Resources and Environmental Control intends to dredge a narrow part of Silver Lake that adjoins Rehoboth Elementary School to remove sediment and improve water quality, said Frank Piorko, director of watershed stewardship for DNREC. The work will also improve aquatic habitat, reduce nutrients that cause algal blooms and improve the aesthetics to the lake, Piorko said during a power point presentation to the school board.
Sediment dredged from the lake would be pumped into 10 Geotubes – completely enclosed synthetic containers that are 100-feet long and 35-feet in diameter.
Chuck Williams, project manager for the division of soil and water conservation, said sediment is pumped into the tubes through a pipe; another pipe returns filtered water from the tubes to Silver Lake. Dried sediment is then removed by truck to be used for fertilizer or landfill elsewhere, he said.
"It's going to be pumped into containers and not run over the property," Williams said.
The process of removing lake sediment, drying it out and hauling it away takes several months, so work would revolve around the school schedule, Piorko said.
"Nothing is planned when school is in session," he said.
Piorko said DNREC would complete the dredging over the summer; the tubes then would sit in a fenced in area on the southside of school property near the baseball fields.
The dried material would be removed in the summer of 2014 when students are on summer vacation, Williams said.
Rehoboth Elementary Principal Trish Mumford said she was concerned how the work would affect the school day. However, she said she was satisfied that the project will not interfere with school.
"They seemed to be able to work around whatever schedule I require," she said.
The proposed dredging project at Silver Lake is the same as what was done in Henlopen Acres recently when its marina was dredged. Geotubes currently sit in a parking lot there as water slowly drains back into the marina. When the sediment dries, it will be hauled away to another location.
Board President Andy Lewis questioned whether a lab report dated 2011 had the latest information about contaminants in Silver Lake. DNREC officials said material to be dredged from the lake does not contain contaminants at levels expected to result in health risks.
In addition, Williams said, all lake materials would be enclosed in the Geotubes; no material will seep onto school property.
When the project is complete, Piorko said, school property would be returned to the way it was before the project began and could even be improved.
Cape school board will discuss the dredging project during its January meeting when it could vote for approval.