Benefits of Alternative Criteria for Scheduling Dewatering Events at Navigation Locks and Repairing or Replacing Lock Components

Abstract

The failure of critical components at navigation locks can cause unscheduled outages that impose high costs on shippers. Presently, the USACE requires that each hydraulic steel structure be inspected at least once every 25 years. At navigation locks, this requires dewatering because several critical components are located under water. Where budgets are limited, this may devolve into the practice of dewatering once every 25 years unless the failure of a critical component causes an unscheduled outage. Nine alternatives to the current practice were evaluated by comparing their costs over a 50-year planning horizon. An empirical transition matrix was used to simulate the degradation and failure of lock components, their repair or replacement, and the occurrence of scheduled and unscheduled outages. The optimal alternative minimizes the present value of lock dewatering cost, component repair and replacement cost, and shipper carrier cost. Results show that, in waterways where the ratio of scheduled to unscheduled shipper carrier cost is low, probabilistic scheduling criteria and structural health monitoring are optimal. These results demonstrate that preemptive maintenance strategies are cost effective.