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Environmental Concerns 



Coastal projects may benefit one or more components of the ecological 

 system while adversely impacting others. As in most projects, an evaluation 

 of the environmental impact of a project must be conducted. From prototype 

 experience, detached breakwaters are generally known to have minimal 

 impacts on the environment, although each proposed breakwater site is unique 

 and must be examined relative to potential negative impacts to the ecological 

 system. An example ecological analysis and Environmental Impact Statement 

 can be found in USAED, Buffalo (1980). 



Water quality and aquatic habitat concerns 



Potential water quality degradation due to reduced circulation has been an 

 environmental concern associated with detached breakwater projects, and has 

 been a notable problem in some foreign projects. Some water quality 

 problems may occur during construction due to increased turbidity and the 

 presence of construction equipment; however, these effects generally do not 

 pose significant risk to most biological resources in naturally turbid estuarine 

 or coastal waters. If breakwater construction occurs in a clear water 

 environment such as in the vicinity of coral reefs or seagrass beds, precautions 

 should be taken to minimize the amount of suspended sediments (EM 1110-2- 

 1204). Long-term effects of the structure may involve indirect impacts on 

 water quality due to changes in the hydrodynamic regime. If proper water 

 exchange does not occur over, through, or around the structures, water can be 

 trapped in the lee and become stagnant and polluted. Water quality should 

 especially be a concern in areas with poor pre-project water quality or limited 

 water level fluctuations. Increased wave transmission and/or wave 

 overtopping, and more numerous gaps with increased widths can improve 

 water circulation and avert water quality problems. 



Over the long term, some aquatic habitat will be lost due to breakwater 

 construction, but rock structures are known to increase the habitat for some 

 marine species and may actually provide greater diversity and productivity 

 than pre-project conditions. The trade-off associated with replacing soft 



Chapter 5 Other Design Issues 



