The discovery of a new bottom layer of sludge at Boat Harbour is being blamed for delaying Northern Pulp's cleanup of the effluent treatment facility in Pictou County. The pulp mill said an independent assessment this summer detected a previously unknown layer of 194,000 cubic metres of sludge at the bottom of the aeration stabilization basin — a series of lagoons where mill effluent has been churned for decades. "This discovery and additional sampling delayed our original fa