New criteria and procedures have been developed for planning, execution and analysis of underwater inspections. The high cost of conducting inspections on the underwater portion of facilities makes it economically infeasible to consider a complete survey of every structural element. The results of the inspection however must be adequate to give an accurate indication of the overall condition and magnitude of maintenance and repair requirements. This paper presents the results of a research project to develop a statistical sampling procedures that allow inspection of a minimum number of elements to produce condition assessments with a predefined precision and level of confidence. This work is based on theoretical studies and results of actual on-site inspections.
More than two-thirds of the facilities of the Naval Shore Establishment are over 35 years old (nearly twice their original design life) and require increasing amounts of maintenance and repair in order to remain operational. The high cost of conducting underwater inspections makes it economically infeasible to consider a complete survey of every structural element in a waterfront facility during preliminary .Inspections intended to assess the average condition and possible need for maintenance and repair. The extent of these preliminary underwater inspections should be a function of the degree of deterioration present. In the structural elements. The data obtained from such an inspection must be capable of determining the condition of the facility within a predefined accuracy and level of confidence.
The objective of this project was to develop criteria to determine the minimum number of data samples required to make an accurate condition assessment of waterfront structures based on construction material, mission requirement, and present condition. The development of these criteria was also to consider the practical procedures for applying the sampling criteria to actual waterfront inspections, taking into consideration such factors as time, cost, and movement of dive station equipment and personnel. This paper presents the results of the study to develop criteria and procedures for determining the optimum data sample size for underwater inspections.
Prior to undertaking the formal development of statistical sampling criteria, a survey was conducted to determine what procedures, if any, commercial port authorities used as criteria for scheduling and conducting underwater waterfront facility inspections. This report (Ref 1) was to determine what criteria were used for sampling and how they determined the inspection frequency. It was found that there have not been any formal cost/benefit analyses made regarding these objectives. Most inspections were done if there was suspicion of damage or on a periodic schedule that was "based upon past experience and the availability of funds". There were no inspection programs that used any statistical sampling as a projection of facility condition.
The lack of criteria and procedures from commercial sources and concerns about the adequacy of current Navy inspection procedures prompted the establishment of the project at NCEL to develop criteria for preliminary inspection of waterfront facilities.