Citing an earlier proposal to eliminate the silt and vegetation by introducing algae-eating bacteria — a plan considered but never enacted after questions arose about its effectiveness — Gravel said, “I hope this one isn’t a science experiment like the last one.”
The plan now proposed by GZA, however, supposes that the biggest expense involves finding a place to put all of the material dredged from the lake and pond. In years past, it was theorized that much of the goo at the bottom of the water got there as a result of development in the vicinity, with lawns and homes creating runoff that made its way down to the ponds.
GZA cited prior studies showing 60,000 cubic yards of sediment now in Crystal Lake and 30,000 cubic yards in the adjacent Elginwood Pond.
But removing the material involves finding a place to put it, Sinewitz explained, and then removing all the water it has sponged up over the years. To do that properly will require the introduction of “flocculating agents” capable of separating liquid from solid. (The report cites a Connecticut project that judged these agents “environmentally benign to aquatic life.”)
The plan calls for a protective berm to be constructed around the lake. The dredged material would be sent to gravel pits off Taylor Street, where water would be separated and then returned to the lake and pond. The material in the lake and pond is 80 percent water now, Sinewitz said.
The language of the report gives a hint at the scale of the task: “While in operation, a suitably sized dredge for this project would discharge to the basin a flow of 2,000 to 3,000 gallons per minute, a rate of flow which must be matched by the return discharge to the pond.”
The task also would involve a lengthy permitting process, involving the city, the state and the federal government.
The belief that the material dredged from the lake would be useful as growing soil has proved to be erroneous, Sinewitz said. To the contrary, he’s been told it has little value.
GZA declined to answer questions.
Staff writer Alan Burke can be reached at email@example.com.