Truck docks are often below the grade of the rest of the site and therefore require a drainage system. A trench drain is the most logical solution and simplifies the concrete construction. Traditionally these drains have been 12" wide cast in place trench drains. This size was common because it was easy to construct wooden forms of this size. With the speed and availability of prefabriacted trench drain systems, they are not the preference and are becoming more common. In many cases the size of the trench can be reduced, unless large flows or high levels of debris are expected.
The grates on these systems should be capable of handling vehicular loading if they will be far enough from the dock where trucks can get their wheels on them. Often times the drains can be placed where the truck wheels will never reach the drain allowing for lighter duty systems to be used.