Sludge estimates at Marion wastewater lagoon continue to climb
MARION — The amount of sludge at the bottom of one of Marion’s Wastewater Treatment Plant lagoons is now estimated to be over 1,000 tons and counting — topping previous estimates which put the figure between 850 and 1,000 tons.
Department of Public Works Director David Willet updated the Water and Sewer Commissioners — which comprises the town’s Selectmen — on the project to clean up the lagoon at a Jan. 28 meeting.
Willet said that until the sludge begins to be removed from the lagoon, there’s no way of knowing how much sludge is at the bottom of the lagoon, exactly.
The project to clean up the lagoon follows a lawsuit from the Buzzards Bay Coalition which claims that runoff from the lagoon was seeping into the ground and into the nearby Aucoot Cove. The town denies this claim.
The $9.5 million project involves draining the lagoon, removing the biosolid waste from the bottom, and relining with an impervious liner. Originally, it was estimated by Camp, Dresser and McKee, Inc. that there was around 350 tons of sludge at the bottom. That number has since gone up twice, currently estimated at over 1,000 tons.
Willet said part of the problem with misestimation of the amount of sludge in the lagoon came from a lack of knowledge about the biowaste’s density.
For a few months, the DPW director said, trucks were hauling out around eight tons of sludge at a time — but eventually the loads grew up to 12 tons. Willet said the increase in load reflected an increase in density as the town dug closer to the bottom of the layer of sludge.
Another issue with the estimation, according to the DPW director, was that rainwater would sometimes cover the solid waste, obscuring how much of it there really was.
Willett said that the added cost of removing the remainder of the sludge is unclear, but that an estimate would be put together for Town Meeting. The town is also looking into switching contractors for the remainder of the removal in order to decrease the price.