The canals often collect pollutants and become foul particularly from 

 septic tank effluents. 



Artificial lakes often act as accumulation basins for septic wastes 

 and organic material, causing depressed oxygen conditions to prevail [74]. 

 Water quality degradation in these man-made lakes typically increases over 

 time, often accelerating as adjacent lots are occupied. The lakes gradually 

 accumulate pollutants and sediments and can become grossly polluted if not 

 properly designed and maintained. 



All artificial basins should be surrounded by a buffer strip of 

 vegetation to maintain runoff water quality. Furthermore, the edge 

 configuration of lakes should provide for acceptable wildlife habitat 

 with growth of cattails [74]. 



4.7.4 Drainage of Land 



Canals and ditches are often excavated to facilitate drainage of low- 

 lying coastal lands for a variety of development purposes. Such projects 

 vary greatly in form, dimensions of the cut, disposal of excavated 

 materials (spoils), and ecological effects. Onshore development of OCS 

 facilities may require drainage of sites in some situations as may 

 secondary development of surrounding communities and support facilities. 

 Drainage projects may dramatically upset the natural shorelands water 

 system with serious adverse effects on terrestrial ecology, as well as 

 the estuaries that benefit from the natural flow of land runoff. 



Canals that convey fresh water to coastal areas also function in 

 the reverse, that is, to convey salt water inland. The intrusion of 

 salt water upstream in artificial canals often has serious adverse effects 

 on inland systems, rendering the water unsuitable for freshwater fish and 

 wildlife. Seawater encroachment can contaminate human and agricultural 

 water supplies, necessitating costly treatment for relocation of intake 

 points. Increased salinity also results in increased corrosion and shorter 

 life expectancy for engineered structures [61]. 



As a general rule, excavation of canals and ditches in wetlands 

 should be avoided because the wetland function is seriously disrupted, 

 vegetation is lost, water flow is disrupted, soil layers are destroyed, 

 pollutable catchments are formed, and the drainage and drying out of wet- 

 lands is facilitated. 



4.8 ROADWAYS AND BRIDGES - SUBPROJECT 8 



This subproject addresses roadways and bridges built in the coastal 

 shorelands, along the edges of water basins, or across the basins. In 

 the absence of environmental safeguards, coastal roadways and bridges 

 have a potential for disturbance, including alteration of fish and 

 wildlife habitat, disruption of water flows and a reduction in the 



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