A trenching machine including a digging boom rotatably attached to a tractor and a digging chain rotatably mounted on the digging boom wherein a crumber assembly is provided that is rotatable between work and transport positions. The crumber assembly includes a support boom attached to the digging boom, a crumber rotatably attached to the support boom, and an actuator for rotating the crumber. The crumber may be folded toward the support boom so that the digging chain of the trenching machine can be moved into close proximity with a vertical wall, such as a building foundation, thereby minimizing or eliminating the need for manual excavation adjacent to the wall.