water as related to the depth of the floating breakwater system. As with 

 fasteners, a prudent inspection and maintenance schedule is mandatory. 



(3) Revetments . If the tires or modules of tires can be securely 

 anchored to the bottom of the natural slope they can serve as revetments. 

 With a specific gravity of only 1.2 they cannot be expected to stay in 

 place of their own weight. They do not act as a revetment in the same 

 manner as rock rubble; i.e., by completely absorbing or reflecting wave 

 energy before it reaches the native bank material. The rubber tire revetment 

 will only partially reduce the energy of the waves and, under persistant 

 attack, increased turbulence may even accelerate the erosion of the native 

 material. It may be feasible to use the rubber tires in conjunction with 

 underlayers of rock to act as a revetment, providing the tires are securely 

 anchored in place. 



(4) Bottom Stabilizers . Rubber tires are being used in parts of 

 the Chesapeake Bay where waves are small and erosion is slow or intermittent; 

 they apparently function by encouraging the growth of marsh grasses and 



the resultant increase in an accumulation of mud to stabilize the entire 

 mass. 



Some success in use of tires to control littoral drift has been reported 

 in areas of low turbulence by simply anchoring rubber tires to the seabed 

 to slow the bedload movement of sand either by currents or wave- induced 

 movements in the littoral zone. This is obviously not feasible in the 

 breaker zone of the open coast and the entrapment of sand outside the 

 breaker zone would be slow and of minor quantities. This application may 

 have particular merit in lakes, reservoirs or bays where surf is not severe. 



(5) Fishing Reefs . Modules of rubber tires, placed in deep water 

 will, because of added surface and the many voids and crevasses, encourage 

 the growth of marine plants and animals. The modules must be anchored in 

 place but this is not as difficult as when used for floating breakwaters or 

 revetments . 



7. Uses in Coastal Construction . 



a. General . The use of recycled materials is very sensitive to the 

 degree of emergency or lack of availability of new materials, the availa- 

 bility of the recycled materials, and the suitability of the materials to ' 

 accomplish the desired design objectives. In some cases such as floating 

 breakwaters, the recycled material, in this case rubber tires, may actually 

 be the preferred material. In every case, the conditions peculiar to the 

 project determine the usability of recycled materials. When suitable, 

 recycled materials can be used in the following types of coastal structures. 



b. Offshore Structures . 



(1) Breakwaters . Concrete rubble and salvaged asphaltic concrete 

 can be used as a substitute for stone underlayers or cores but their lower 

 densities must be considered when making the substitution. Crushed concrete 

 can be an effective core material. Concrete blocks and brick can also be 

 used as rubble in place of stone underlayer or core allowing for their 

 lower densities. Crushed, these materials can be used for core material. 



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