In a very unusual move, NYC’s DEP brought in a privately-owned sludge tanker barge, the Lisa, to move residual solids from the North River water treatment plant to the Passaic Valley plant in Newark for dewatering on Tuesday, with the tug Vinik No. 6 moving her. The city normally relies on its own fleet of five tankers for this work, but a number of these tankers have been out of service lately: the Hunts Point has been tied up at Wards Island since a fatal explosion several months ago, the old North River tanker has been out of service all year, and, until recently, the tanker Rockaway was getting work done at GMD in Brooklyn Navy Yard. The Lisa has serviced the North River plant in the past but not, as far as I know, for many years and I don’t know why she was brought in this week. Please feel free to reply in the comments if you know more.