City crews plan to cut down trees and thick overgrowth near a section of the Bangor waterfront that has long provided obscurity and shelter to a sprawling homeless encampment, city officials said. The work, which begins Wednesday morning, is aimed at dismantling a longstanding camp of about 40 people that in recent weeks has erupted in a series of violent assaults, arsons and, most recently, a stabbing Friday night, according to city officials and police. “It just gets to a point where it gets too dangerous and you just have to do something,” said Dana Wardwell, Bangor’s director of public works. The camp is located along a trail between lower Dutton Street and the I-395 bridge. In the past, after repeated acts of violence, the city cleared out the people living in the encampment, but before long, they moved back in.