Kaumalapau Harbor, Hawaii, Breakwater Repair

Abstract

Abstract : Cumulative damage to the Kaumalapau Harbor breakwater over years resulted in nearly total failure of the breakwater armor layer both above and below the waterline. Breakwater repair incorporated use of largest CORE-LOC(registered trademark) concrete armor units (35 ton) ever placed on a USACE structure. Four aspects of this rehabilitation were monitored. Lessons learned include: 1. Armor unit material strength and breakage due to movement: (a) Standard methods of specifying concrete strength are not necessarily applicable to coastal structures composed of concrete armor units more research and development is needed; (b) Construction methods are an integral part of concrete armor unit stability, and variability of methods may contribute to armor layer vulnerability; (c) Small-scale post-construction armor unit movement will not necessarily lead to armor unit breakage. 2. Breakwater structure and armor layer settlement: (a) T-LiDAR is an accurate and comprehensive method for monitoring changes in complex coastal structures such as those with concrete armor units; (b) Maintaining packing density around bends in structure and structure head as much as possible may limit the amount of unit movement and/or damage following construction; (c) Minor settlement and movement of armor units following construction does not affect the integrity of the structure. 3. Concrete breakwater cap: (a) Small-scale post-construction armor unit movement will not necessarily lead to concrete cap settlement or damage; (b) Stability of concrete cap can likely only be field-verified if a wave event causing overtopping of the structure is experienced. 4. Armor layer toe stability: (a) Cannon and straddled orientation of the first and second rows of CORE-LOC toe units appears to be a successful placement scheme in this case; (b) Combination of traditional high-density survey methods augmented by visual observation techniques provided thorough evaluation of underwater structure condition.