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States is the 13.7-kilometer-long (8.5-mile) Los Angeles-Long Beach breakwater complex built between 1899 and 1949. Other U.S. offshore breakwaters are listed in Table 5-3 of Chapter 5. 2. Segmented Offshore Breakwaters. Depending on the: desired function of an offshore breakwater, it is often advantageous to design the structure as a series of short, segmented break- waters rather than as a singular, continuous breakwater. Segmented offshore breakwaters can be used to protect a longer section of shoreline, while allow- ing wave energy to be transmitted through the breakwater gaps. This permits a constant proportion- of wave energy to enter the protected region to retard tombolo formation, to aid in continued longshore sediment transport at a desired rate, and to assist in maintaining the environmental quality of the sheltered water. Additionally, the segmented breakwaters can be built at a. reasonable and economical water depth while- providing storm protection for the shoreline. Figure 6-66 illustrates the structural details of the segmented rubble- mound breakwater at Lakeview Park, Lorain, Ohio, which is on Lake Erie. This project, which was completed in October 1977, consists of three detached rubble-mound breakwaters, each 76 meters long and located in a water depth of . -2.5 meters (-8 feet) low water datum (LGTD) . T'ne breakwaters are spaced 50 Haters (160 feet) apart and are placed about 145 meters (475 feet) offshore. Bey protect 460 meters of shoreline. The longer groin located there was extended to 106 meters (350 feet), and an initial beach fill of 84,100 cubic teeters (110,000 cubl~ yards) was placed. A primary consideration in the design was to avoid the formation of tombolos that would interrupt the ~ongshore sediment transport and ultimately starve the adjacent beaches. Immediately after construction, the project was monitored for 2 years. ~.ndings indicated that the eastern and central breakwaters had trapped ~.ittoral material, while the western breakwater had lost material (Walker, mark, and Pope, 1980;. The net project gain was 3800 cubic meters (5,000 ~bic yards) of material. Despite exposure to several severe storms from the .-rst during periods of high lake levels, there had been no damage to the ~eakwaters or groins and no significant erosion had occurred on the lake j ~ttom between the breakwaters. f X. CONSTRUCTION MATERIALS AND DESIGN PRACTICES i The selection of materials in the structural design of shore protective marks depends on the economics and the environmental conditions of the shore . area. The criteria that should be applied to coffiznonly used materials are I scussed below. ~ I Concrete. i The proper quality concrete is required for satisfactory performance and ~ r=rability in a marine environment (see Mather, 1957) and is obtainable with concrete design :snd construction practices. The concrete should have low se~eability, provided by the water-cement ratio recommended for the exposure :_=xlitions; adequate trength; air entrainment, which is a necessity in a 6-95