If all goes as planned, a new piece of public art will be installed on the Bangor waterfront by the end of the year, to hide a huge concrete, iron and steel exhaust pipe that’s part of the city’s new sewage and stormwater tank project. As the nearly 30-month project to install the 3.8-million gallon tank on the Bangor waterfront draws to a close, construction crews have been working on the finishing touches — including a standalone, above-ground, 24-foot-tall stack and exhaust pipe, to allow for the release of any gasses that might accumulate in the tank below. That stack and pipe was supposed to be attached to a nearby maintenance building, until contractor S.E.