|Stormwater Drainage and Land Reclamation for Urban Development (HABITAT, 1991, 94 p.)|
The importance of an adequate system for maintenance of the drainage system cannot be overemphasised if the system is to operate at its design capacity. If rubbish and silt are allowed to accumulate in channels and rivers, these facilities will not be capable of satisfactorily fulfilling their primary function - the removal of stormwater run-off. If the inlets into the drainage system from roads are not regularly cleared, they will become blocked and stormwater will be prevented from entering drains, so causing local flooding. The objective of a maintenance programme should, therefore, be to keep the drainage system operating dependably, at its design capacity, without breakdowns.
Protection of the capital investment in the drainage system necessitates a planned programme of inspection and routine clearing. Periodic, thorough and competent inspection while cleaning will reveal points at which damage begins to take place. Adequate financial and labour resources must be allocated to ensure successful drainage operation and maintenance. It is therefore necessary for drainage authorities, usually the local government, to ensure that maintenance is accorded a sufficiently high priority in the allocation of funds in annual budgets.
The objectives of carrying out the maintenance programme should be to:
(a) Keep the system operating at design standard at all times;
(b) Obtain the longest life and greatest use of the systems facilities by providing adequate maintenance and timely repairs;
(c) Achieve the foregoing two objectives at the lowest possible cost.
The history of drainage is full of examples of the difficulties which can occur when maintenance is neglected. Even the best constructed system will eventually fail if adequate maintenance is not undertaken.
Maintenance activity should begin the day the system is placed in operation or, under some circumstances, prior to completion of a system and before the system is placed into operation. Keeping maintenance work current on all facilities in a system is the keystone to any successful drainage enterprise.
There are two primary concepts of maintenance of public property, and most maintenance operations can be readily classified into one of these categories:
(a) Maintenance by necessity;
(b) Preventive maintenance.
Maintenance by necessity refers to the practice of fixing it when it breaks down. Under this approach cleaning of drains is confined to the minimum necessary to satisfy complaints. Likewise, repair work is undertaken only when a condition becomes so bad that it must be corrected or repaired to restore service or for safety reasons. Unfortunately, this approach is all too common in rapidly growing cities where the funds for routine maintenance are inadequate.
Preventive maintenance is represented by a systematic programme of inspection, cleaning and repair that reduces breakdowns and complaints to a minimum. Preventive maintenance not only pays dividends in economical operation; a smooth working system also means uninterrupted removal of water at lower cost with reduced risk of damage from flooding as a result of design storms.
Preventive maintenance also has other distinct advantages:
(a) It can be scheduled and performed on a regular basis at times that least disrupt other operations functions;
(b) Pre-ordered parts can be made more readily available; they may not be so readily available under emergency conditions;
(c) Work can be carried out during normal working hours with less emphasis on extension of hours and weekend work;
(d) More experienced personnel can be used if the work is scheduled; they may not be available in emergencies;
(e) Special tasks of preventive maintenance may be contracted out to reduce the need to carry a specialist workforce.