PART 4 - POTENTIAL DISTURBANCES OF STANDARD SUBPROJECTS 



This part reviews the major construction and operation activities 

 associated with OCS-related projects and describes the ecological 

 disturbances that arise from them. The material is presented under 20 

 standard subprojects, which are the basic engineering work units involved 

 in implementing the variety of OCS-related projects described in Part 3. 

 In addition to the effects of primary OCS facility development, the 

 subprojects cover a wide range of effects on coastal communities from 

 secondary development ranging from roadways, to beach protection, to 

 mosquito control. Specific sources of the material for the subprojects 

 are cited in the text except for that which came from The Conservation 

 Foundation's guidebook Coastal Ecosystem Management (John Wiley and Sons 

 Interscience, New York, 1977) [61]. 



4.1 NAVIGATION IMPROVEMENT - SUBPROJECT 1 



Marine navigation improvement, as treated here, applies to existing 

 navigable waters of the United States, and includes: the widening, 

 deepening, or straightening of natural channels; the excavation of new 

 channels in navigable areas; and other improvements (such as navigation 

 aids). Navigation improvement is a major subproject of many onshore 

 OCS facilities projects, involving navigation channels, turning basins, 

 berthing spaces, harbors, canals, and marinas. It does not encompass 

 excavation of waterways in presently non-navigable areas (i.e., canals 

 cut through the lands) or those dug primarily for real estate development 

 (see Subproject 7, Artificial Waterways). 



4.1 .1 Summary 



Most navigation improvement work is done with marine dredges. The 

 dredged material, or dredge spoil, is barged or piped to a disposal area 

 or, infrequently, temporarily stored aboard for later disposal. Navigation 

 improvement projects range from a few cubic yards, excavated by dragline, 

 to a long deep channel producing millions of cubic yards of spoil, 

 excavated by ocean-going hopper dredges. Considerable differences are 

 imposed by type of equipment as well as scale and season of the work. 



Plans for new navigation projects should recognize the potential need 

 for periodic maintenance dredging (throughout the project life) after 

 completion of the initial work on the project. In many cases the require- 

 ment of maintenance dredging will place a limit on the feasibility of the 

 original project, because of the expense or difficulty anticipated in 

 locating adequate spoil disposal areas. 



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