Airports
Trench drain systems at airport facilities cover a broad spectrum. Trench drain is usually used in the taxiways and in front of the hangar doors of county airports that support small single and twin prop aircraft. These drains tend to be a 4 inch wide pre-sloped system with ductile or cast iron slotted grating because surface areas are relatively small and the loads are light (Class D).
Municipal airports are a little bigger and the aircraft using the runways may contain some light commercial crafts. Hangar doors will commonly see 4 inch wide trench drain and some slot drain systems. Along the taxiways, 8 inch and 12 inch wide pre-sloped drains with Class D and E grating will be found.
International airports are dealing with big equipment and acres of concrete surfaces that need to be drained quickly in the event of a storm. Trench drain systems generally have Class E and F load ratings. With grates that have 3-point lockdown systems, the high percentage of open area of the grates along with the trench dimensions are designed for large flow capacities. Of course, the trench size will depend on the surface to be drained, but, it is not uncommon to see 12 inch wide trenches that reach 3-to-4 feet deep.
Truck Terminals & Loading Docks
Truck terminals and loading docks see a lot of tractor trailer and forklift traffic. Inside the terminal building where the fork truck traffic is concentrated, 4 inch wide trench drain with cast or ductile iron frame and grates (Class E and F) is common. Here, wheel loads are high but the flow requirements are low.
Outside in the bay area, drain widths are designed according to the size of the watershed it will support. Lowe’s Home Centers, which have 40 feet wide truck ramps that see only a small amount of run-off water, need only a 4 inch wide pre-sloped polymer concrete trench drain to have adequate drainage. As the watershed of the bay area increases, so does the width of the drain. Generally speaking, as the drain design reaches 8 inches and wider, trench forming systems and cast-in-place trench drains become a more frequently specified product due to material costs and flow requirements.
Bus Garage/Railroad Station
Bus garages, bus washing facilities and light rail stations are big users of trench drain. 4 inch wide pre-sloped polymer concrete systems with cast iron frames and slotted grates are commonly seen in the garage and maintenance areas to handle the residual water and snow brought in by the heavy buses. In the washing stalls, wider drains and sand traps are used to catch the wash water. As the grating may not actually see load from the vehicle, steel or fiberglass bar grating can be used in these areas.
Light rail passenger stations are usually covered and see little direct storm water. Trench drain systems in these applications can be narrow but need to be pedestrian friendly. Heel proof and ADA approved grating is often used. Architectural and decorative grating options are available to complement the station aesthetics.
Cargo Loading/Ocean Container Terminals/Port & Intermodal
Conditions for trench drains at ports and seaside terminals are harsh, with salty water and air combining to form a corrosive effect on equipment, especially the trench drain. Drains have to withstand the weight of heavy container handling machinery while managing heavy water flow. Wide polymer concrete trench drains with a Class F, bolt-down frame and grate are the standard choice for these applications. High volume slot drains are also a common feature at the port to help keep the loading areas free of excess water.
Roadway Drains
Trench drain systems for highway use need to be approved by the Department of Transportation of the local State. The approved products from state to state are similar and have a few similar properties.
- High Strength Grating – Class F load requirements are a standard specification.
- High Percentage of Open space in the grating – The more open space which a grate has, the more water that drain can handle until the channel physically reaches its capacity.
- High flow or High water capacity – The first criteria in designing a trench drain system is to determine what capacity is required to handle a large storm. For large watershed surfaces, large capacity drains are required.
Roadway trench drain can be used to cross a road to keep run-off water from entering another section of the road (such as a toll booths and weigh stations). However, a large percentage of trench drains that are installed in roadways are running parallel to the direction of traffic. Catch basins are commonly used for highway drainage. However, in cases where the road is flat and provides little natural drainage slope, trench drains are used in the median and shoulder areas.
