Long Beach Breakwaters Suffered Damage
Los Angeles-Long Beach Harbor, located approximately 25 miles south of downtown Los Angeles in San Pedro Bay, is protected by three breakwaters: San Pedro Breakwater, Middle Breakwater, and Long Beach Breakwater. Two high-use ports are located within the harbor: the Port of Los Angeles and Port of Long Beach.
On or about August 26, four days of heavy waves generated by hurricane-force winds from Hurricane Marie in Mexico crushed onto the three breakwaters. As a result, all three breakwaters suffered damage and are in need of emergency repair. The most significant damages were to a portion of the Middle Breakwater.
The Middle Breakwater is an 18,500 foot long, detached breakwater functioning as a major structure that protects the Port of Long Beach. Hurricane Marie caused eleven major damage areas (breaches or near-breaches) and 39 other areas of significant or moderate damage. In total, it is estimated that 1,550 feet of breakwater needs to be repaired for the major damage areas, 850 feet for significantly damaged areas and 1,725 feet of moderately damaged areas.
The District dispatched coastal engineers between August 29 and September 4 to inspect the breakwaters by boat, air and foot. Based on these inspections the most significant damages appear to be the eleven areas in the Middle Breakwater.
The majority of the damage from the storm waves was concentrated on the Middle Breakwater. The immediate concerns are focused on the breached breakwater and areas of significant damages.
Two factors need to be considered:
1) the functionality of these structures and;
2) the structural integrity of the breakwaters.
The structural integrity of the breakwaters has been compromised, especially at the Middle Breakwater. As with all these types of structures, once they start to come apart they are very susceptible to greater damage following any additional significant wave event. Breaches of the breakwater will allow greater transmission of wave energy into the inner portions of the harbor.
The breakwater in its current condition remains functional with average daily wave condition remains functional. However, with any significant wave or storm event in the area, its functionality has been compromised and will decrease as wave height increases.
The probability of strong wave conditions is expected to increase in the next few months, increasing the risk of storm damages to harbor infrastructure and possibly impacting/delaying port operations. The hurricane season still has two months to go and will be followed directly by the winter storm season. Therefore, repairs to breached areas should be made immediately. The cost of potential loss of operations, should a future significant wave or storm event strike the breakwater, given its damaged state, has not been determined.
Based on the District’s assessment, the eleven major damaged areas on the Middle Breakwater need to be fixed immediately. There are eight significant areas that are classified in the same category as the breaches, due to the fact they only have one layer of rock without any interlocking. These areas would be the next to potentially fail.
Since the breakwater is not accessible by land, the method of repair will involve water-based equipment, consisting of a crane and rock barges. The proposed repair of these areas will entail stone replacement with new rocks and shifting existing rocks so that a proper interlocking can be achieved. The goal is to repair these sections back to their authorized dimensions, with an elevation of +14′ Mean Lower Low Water. Rocks for the breakwater will be obtained from a quarry to be determined by the contractor according to contract specification.
No excavation is expected to be needed for the repairs, as the water depths in the area are adequate. It is expected that temporary, minor impacts to the water quality would occur from an increase in turbidity from moving existing and placing new quarry stones on the breakwater during the construction period. Disturbance to marine mammals and seabirds caused by the breakwater repairs is expected to be short-term as animals are expected to acclimate to this non-threatening construction noise. Proper NEPA process and related environmental concerns will be addressed, and proper contracting law will be followed as well for this repair.
The current estimated cost of the repair of the eleven major damaged areas on the Middle Breakwater is approximately $20 million. The cost to repair the remaining 32 areas of major and significant damages on all three breakwaters is currently unknown.
The District is looking into different funding options for executing this work.