A major area of work performed by the UCTs is related to the maintenance and repair of facilities in the marine environment. Typical tasks involve maintenance and repair of cables, pipelines, fleet moorings, pile and sheet pile structures, cathodic protection systems, and scour protection. Maintenance consists of checking and keeping in good repair the various systems or combinations of systems designed and installed to protect a facility when it was originally built. Repair consists of restoring die facility to its original condition, or a predetermined lesser condition, after deterioration has taken place, or restoring or replacing the original protection system.

General techniques for most of the maintenance and repair operations with which the UCTs would be tasked are described in this chapter as follows:

• Section 5.2 - underwater cables

• Section 5.3 - underwater pipelines

• Section 5.6 - steel sheet pile structures

• Section 5.8 - concrete sheet pile structures

• Section 5.10 - timber sheet pile structures

• Section 5.11 - cathodic protection systems

• Section 5.12 - scour protection

Remember that each maintenance and repair task can vary from those described in the above sections and may impose unique circumstances. Therefore, the final techniques used must be determined by the personnel familiar with the particular operation on a case-by-case basis.

For each of the maintenance and repair tasks described in this chapter and normally carried out by the UCTs, a table is provided that presents specific characteristics of:

• Any special training the crew may require

• Expected productivity of the crew

• Equipment required

• Materials required

• Potential problems that may be encountered.

The "Description of Task" presented at the top of each table describes the characteristics of a typical unit of work within a major maintenance or repair project. It is intended to cover the "worst case" (i.e., a situation where the full range of materials and equipment will be required). In actual practice, a particular task may not require some of the materials and equipment listed. For example, for the repair of a steel pile by concrete encasement, the task description in the table states that the pile will be encased from 1 foot above the high waterline to 2 feet below the mudline. If the actual task did not require the encasement to extend below the mudline, a jetting pump would not be required and the productivity of the crew would be somewhat higher.

As for the personnel requirements, Section l.S describes the assumptions made regarding the size and training of the crew. The productivity of the crew is based on a UCT detachment with average experience and capability working under good conditions and the assumption that the described task is a typical one in a project that requires a number of the same tasks.

The tables include a list of potential problems to show the need to be prepared for contingencies. The lists contain only those problems, related direcdy to the task, that have been experienced and reported in the past; they do not completely list all problems that may arise. The UCT detachment must be prepared to cope with all contingencies, particularly when at a remote site.

For successful operations, it is essential for the UCT detachment to be prepared for specific site conditions. Section 1.4 lists the information about the site that should be obtained before deployment. Other useful information is provided in Appendix C.

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