What is drainage?
How water is led out of the structures that hold airfield lighting and into the civil drainage system, so cables, connectors and transformers are not left standing in it.
Drainage, at the AGL civil interface, is the arrangement that carries water out of base cans, transformer pits, handholes and cable ducts to an outlet in the airfield drainage system. It normally means a drain hole and free-draining sump at the low point of each structure, pipes and ducts laid to a fall, and an outlet such as a drain line or soakaway, all as the design shows.
It is a civil interface because the water has to go somewhere that belongs to the civil works. The route, levels, falls and outlet come from the civil drainage design and must be agreed with the AGL team before trenches are cut and bases are set. A cable trench or duct bank must not cut across, block or short-circuit an existing drain, and it should not become an unplanned drain itself. Water left standing around connectors and transformers can cause insulation faults, corrosion and earth faults on the series circuit. Keep drain openings clear of grout and spoil, treat any cable as live until it has been isolated, locked out and proved dead, and work to the airport’s permit-to-work.
The whole route from AGL structures to an outlet, agreed with the civil drainage design.
The drain hole, sump and pipe serving one light base can.
Frequently Asked Questions
Q1What is drainage in airfield ground lighting?
The arrangement that carries water out of the structures that hold airfield lighting, such as base cans, transformer pits, handholes and cable ducts, to an outlet in the airfield drainage system. It normally means a drain hole and free-draining sump at the low point of each structure, pipes and ducts laid to a fall, and an outlet such as a drain line or soakaway, all as the design shows.
Q2Why is drainage a civil interface?
The water has to go somewhere that belongs to the civil works. The route, levels, falls and outlet come from the civil drainage design, so the AGL team must agree them with the civil designer before trenches are cut and bases are set.
Q3Why does water in an AGL structure matter?
Seals and joints are never perfect, so some water gets in. If it cannot drain, it stands around the isolating transformer and connectors and can cause lower insulation resistance, corrosion and earth faults on the series circuit.
Q4How are ducts and pipes arranged to drain?
They are laid to a fall toward a handhole, pit or outlet as the design shows, with no sags or low spots where water can sit. Handholes and pits normally have a free-draining sump or drain connection at their low point.
Q5Can a cable trench or duct affect site drainage?
Yes. A trench or duct bank can cut across a pipe, subdrain or edge drain, and its backfill can carry water along the trench like an unplanned drain. Check the drainage drawings before digging, reinstate anything disturbed to the civil designer's detail, and agree any crossing with the civil team.
Q6How is drainage checked and kept working?
Protect drain openings from grout, spoil and debris during construction, then flow test by pouring water in and confirming it leaves steadily. Record the result. In service, clear silt and debris from drain holes, sumps and outlets, and check them after heavy rain.
Q7Where are the requirements defined?
FAA AC 150/5340-30 covers design and installation of airport visual aids, AC 150/5320-5 covers airport drainage design, and ICAO Doc 9157 Part 5 covers electrical systems. Confirm against the current edition, the design drawings and the manufacturer's data.
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