A collection tank for a mobile vacuum excavator includes a front with a closed end, a rear with an open end, a door configured to be closed over the open end, and a linkage assembly having a first end attached to the door and a second end attached to the body. A first pivotal movement drives the first end and second end away from each other, and a second pivotal movement moves the first end and the second end toward each other. An actuator is attached to the first arm and to the second arm so that actuation of the actuator in a first direction drives the first pivotal movement and actuation of the actuator in a second direction drives the second arm the second pivotal movement.