Carmans River has considerable sediment buildup in multiple locations downstream from Lily Lake. The Town of Brookhaven’s management plan outlines a dredging process to decrease high turbidity levels.
So far, over three-quarters of Lily Lake is currently drained, however, no work will be done in the near future, to allow for the brook trout spawning season to not be affected.
New York State Department of Environmental Conservation issued a permit modification to the town to remove sediment from a pool below the spillway of the Lily Lake dam with a portable trash pump and a vacuum truck. It is estimated that there is 600 cubic yards of sediment below the spillway, said Anthony Graves, Brookhaven’s chief environmental analyst.
The majority of large accumulations of sediment identified are located between the spillway and the underpass of the Long Island Railroad — a 0.65-mile stretch. Most of these accumulations, however, lack vehicle access.
“We’re looking at different methods for areas where we don’t have vehicle access, and we’re not there yet as far as a methodology goes,” Graves said at the Wertheim National Wildlife Refuge Visitors Center in Shirley on Friday.
Brookhaven Town went forth in beginning to drain Lily Lake on Aug. 20, in which levels of boards were incrementally removed from weirs in an attempt to rid the impoundment of invasive plant species, primarily cabomba and leaf-variable milfoil. As the water lowered, however, it became increasingly cloudy with suspended sediment.
“The thinking at that point was that the very light sediment was going to go through the system and not stop anywhere and that if we did things slowly, you wouldn’t see accumulations downstream,” Graves said. “Hindsight being 20-20, we know that was not the case.”
After more instances of accumulation became evident, the DEC advised the town to begin reinstallation of boards in the weir to stop flow and to stop more sediment from going downstream. The first level of boards were replaced on Oct. 1.
The following day, the town directed PW Grosser, the hired environmental engineering consulting firm, to draft a plan to keep the water flow going through the lake bed from contacting the sediment. The consulting firm is also working with Suffolk County on the Canaan Lake restoration project in North Patchogue, which is a similar approach but warrants different considerations, as it is within a different watershed.
A second level of boards were then removed on Oct. 7 as turbidity levels remained unacceptably high. Instruments that measure turbidity are installed at three locations downstream, and the locations farther downstream continued to record levels above what the Clean Water Act permits, while the measure near the spillway lowered.
“We inferred that there was a slug of sediment going down the river that had already been discharged,” Graves said. “So we stopped any new sediment, but there was sediment in the river that was moving downstream.”
That inference led to the permit modification administered by the DEC allowing the town to pump sediment from below the spillway. There has been no known analysis conducted on this procedure’s impact on the spawning of brook trout, Graves said.
The Town of Brookhaven was also issued a permit from the Suffolk County Department of Public Works, as the dam and Yaphank Avenue, directly above, are both county-owned, Graves explained. When asked by George Costa of Art Flick Chapter Trout Unlimited if the town has removed sediment downstream with a fishing boat and a pump, Graves said that he would not answer the question.
“I heard that the town had possibly taken a little boat, gone down the river, and with a pump tried to scoop [sediment] out and dump it into the surrounding vegetation,” Costa said.
Biologist Kevin McAllister, founder and president of Defend H20, said he shared concerns that if this instance occurred, sediment was being discharged into the surrounding wetlands.
“It could be impacting another area,” McAllister said. “You can’t do this without permits.”
Environmentalist group representatives attending the annual Carmans River Partnership meeting together with Carmans River Management Plan Performance Committee, like McAllister, opposed the planned dredging and expressed the consideration of dam removal at Lily Lake instead.
“Seeing the impacts here, it behooves us to rethink the drain-and-dredge of the impoundment itself,” McAllister said. “It’s going to be a mess when the excavation machinery actually gets in there. We could very well see a repeat and many more damaging impacts of what we’re dealing with right now.
“There hasn’t been a good enough effort to educate the community on the real benefits to removing those dams,” McAllister added. “Instead, we keep treating the symptoms as opposed to the ill. The ill is the dams, and the symptoms are the cabomba and the buildup of the muck.”
The consideration of a gatekeeper group was raised by Karen Blumer of the Open Space Council at the meeting on Friday to interact with the Town of Brookhaven and the DEC regarding the Carmans River restoration project.
“We have a room full of fishermen and other biologists, who have lived on this river most of their lives, and they know the spawning,” Blumer said. “The fact that there were no sediment controls is inexcusable. We really need somebody to be working with the town and with DEC to come to some kind of informed alternatives as we go forward to correct this in some way.”
McAllister agreed with Blumer that a group of such nature would be beneficial for the involvement of interested parties in a course of action.
“We have to take the management of the river out of the hands of the politicians, and that’s where it has lied for years,” McAllister said. “Let’s get back to the table and start talking about dam removal in a very strategic way. Bring in the expertise that can help guide the appropriate approach.”
According to Romaine, the town has worked with the groups over many years to protect and restore areas within the Carmans River watershed. The upper river, lower river, lakes and tributaries span many different communities and there are often voices that speak for one or more areas, but not for the whole river. The town is interested in remaining able to hear all of the voices involved without giving extra weight to any one voice.
Graves said he will relay Blumer’s request to Brookhaven Town supervisor Ed Romaine and invited other parties interested in such to contact the supervisor’s office.
The timetable, he said, which has been delayed by problems with project design, was originally to drain the lake by Sept. 15 to allow sediment to dry until February, remove sediment and invasives from the lake bed in March and April and have the lake filled by June 2019.