B. The maintenance programme

All structures and facilities are subject to deterioration in varying degrees over time. Regular inspection therefore is necessary to detect and correct potentially unsafe or unsatisfactory conditions as they develop. Cracks in concrete or masonry, general erosion behind structures or settlement of an embankment can result in major failures if the cause is not identified and corrected or repaired without delay. Many problems that develop may not be of such a serious nature. In channels, the control of weeds, storm erosion of banks, seepage of water through banks and base, silting and accumulation of debris or solid waste may be less serious than structural failures, but they still require regular attention if efficiency of the system is to be maintained. Frequently these latter problems are more time-consuming and costly over the years and are more frequently neglected since they accumulate slowly.

The use of appropriate materials and methods for repair or replacement is important. This can include adequate attention to the quality of the concrete aggregate and cements used, and the characteristics of protective coatings used to meet environmental requirements. Staff responsible for drainage system operation and maintenance should always be alert to the development of new materials and products and their possible adoption for the solution of maintenance problems.

The application of the agreed maintenance procedures requires close supervision and the development of a range of skills in the maintenance workforce.

To accomplish the required maintenance, questions arise concerning the use and protection of materials, the need for lines of communication and access, and the personnel requirements to accomplish the work. Regular inspections and records of complaints will identify any components in the drainage systems which are not meeting the design criteria. If it is found that a structure or facility does not perform the purpose for which it was designed, the designer should be advised. In this regard, experienced operation and maintenance personnel can be of key assistance if they are given the opportunity to review system designs before a facility is constructed. In carrying out such reviews, they should consider designs and construction that will require the least maintenance consistent with budgetary constraints.

Obtaining the longest life and greatest use of drainage facilities can best be accomplished by providing good maintenance and a programme of systematic improvements and replacements. In many instances, it is hard to determine the point at which good maintenance ends and replacement begins. Good maintenance, for example, may necessitate the replacement of a gate leaf, later a gate shaft, and perhaps later still the lifting device itself.

As drainage works advance in age, a programme to replace worn out and obsolete structures is necessary to extend the useful life of the system. The essential requirement is to have a maintenance plan and programme.