It is of great importance that the draining system is working properly, hence regular checks (e. g. Fig 13.44) and maintenance are required. Every drainage system should be designed to ensure that inspection and maintenance operations are possible and accessible. Usually, the cleaning of the drainage system should be done at the end of the summer, but inspections could be intensified in periods of high precipitation. However, at least every 5 years it is fundamental that there is a proper inspection of every part of the drainage system.
The problems that practitioners encounter are manifold. In the WATMOVE questionnaire survey (see www. watmove. org) the following issues were mentioned:
• The drainage system becomes clogged with fine materials,
• Crushed pipes,
• Poor outlet conditions, i. e. outlets have negative slopes,
• Root penetration,
• Generation of ferrous hydroxide and calcium carbonate,
• Insufficient capacity,
• Inadequate water velocity,
• The (plastic) cover of the inspection well at the slope may be damaged (sometimes due to snow clearance of the road).
An earlier study by Dunnam & Daleiden (1999) revealed similar problems as well as blockages by vegetation and animal nests.
In order for maintenance works to take place and to ensure a long life for the road, it is essential to plan a maintenance programme, based on a series of procedures, measures, actions and practices. The establishment of maintenance actions, of a systematic nature, and emergency actions should be part of that intervention plan.
The systematic plans, i. e. those used in normal conditions, aim to guarantee that the drainage systems remain in a good working condition. These plans will comprise, at least, inspection actions, vigilance and cleaning (which include the removal of sediments), clearance of channels and ditches and the removal of vegetation.
Inspections could be visual or by video surveillance of pipes, depending on pipe diameter. Close-circuit TV cameras are available, mounted on the end of umbilical cables and incorporating lighting, to achieve down-pipe inspections (Dunnam & Daleiden, 1999; Fleckenstein & Allen, 1996; FHWA website).
The intervention plans, for accident/emergency situations, requires fast intervention of maintenance teams, to mitigate the negative impacts on personal safety and environmental contamination. To do so, a sequence of procedures should be established and adapted for different scenarios. These will require prior surveys, covering:
• The boundaries of water areas and environmental compartments;
• aquifer vulnerability;
• sensitivity of each compartment;
• existing drainage systems;
• the assessment of potential hazard sources (including industrial areas); and
• transportation requirements for dangerous substances.
In order for these plans to fully work, one must ensure proper management of the road infrastructure with maintenance programs, specialist human resources and operational and logistical support.
