Watertight Box Culverts Submitted by ed on Mon, 08/19/2013 - 11:54 In New England they are called "Tunnel Tanks" in other states "Box Culvert Style Tanks" Often used to store water, or as a large commercial septic tank. They cannot leak. Tags: Tunnel TankBox Culvert Style TankBolt Pocketprimed JointButyl Gasket