will increase. The magnitude of adverse 

 impacts may be dependent on the char- 

 acteristics of the site and on the type 

 of structures in the area. Open pile 

 structures do not impede water or sedi- 

 ment movement unless the pilings are 

 spaced very closely. Sediment deposits 

 will build up if too many pilings are lo- 

 cated in a poorly flushed area or in one 

 of slow water flow. The shoreline will 

 stop littoral drift, fillinq with sediment 

 (Carstea et al. 1976). 



The impact from shading increases 

 as the area being shaded increases in 

 size. Water temperature modifications 

 and reduced primary productivity may 

 have an adverse impact on the food 

 chain. The absence of algae and grass- 

 es eliminates hiding areas for fish and 

 other organisms, but this may be offset 

 by the new habitat created on the sub- 

 merged structures (Figure 45). 



Structural and Nonstructural 

 Alternatives 



The commonly noted function of a 

 pier is to serve as a landing place for 

 vessels. Piers, due to their open struc- 

 ture, disrupt water circulation and bot- 

 tom dwelling species much less than al- 

 ternative solid structures, such as walls 

 or sheet pile caissons. 



The most common alternatives for 

 piers are: 



o For mooring vessels, an anchor or 

 mooring buoy could be used. This 

 is more common in New England 

 and areas of extreme tidal range. 



o For mooring vessels and providing 

 access to the shore, a floating pier 

 could be used. This alternative 

 might be aesthetically more desir- 

 able but will probably cause in- 

 creased shading and affect littoral 

 transport. 



If the objective is to eliminate the 

 pier, there are two nonstructural alter- 

 natives available: 



o Combine the purpose of the pro- 

 posed pier with that of piers in 

 the vicinity to reduce the overall 

 number of piers. 



o Use the launching ramps or other 

 launching structures. Provide up- 

 land storage of vessels. This, 

 of course, is limited to smaller 

 size vessels which can be conven- 

 iently removed and transported on 

 dry land. 



o Forrp community marinas to elimi- 

 nate single piers at each water- 

 front lot. 



Aside from the aesthetic consider- 

 ations, loss of navigable water area, 

 and-in rare instances-interference with 

 sand movements, the impacts of open pier 

 structures are minimal. Solid pier 

 structures are generally less desirable 

 and more costly. Elimination of piers 

 by multiple use of existing piers or 

 launching facilities appears to be the 

 best alternative. 



Regiona l Considerations 



Very little information was found 

 regarding regional specific aspects of 

 piers, pilings, and other support struc- 

 tures. The types of materials utilized 

 will vary according to availability 

 within each region. The length of piers 

 may vary depending on the distance to 

 deep water which is generally quite dif- 

 ferent on the Gulf coast (Coastal Region 

 3) and in the Chesapeake Bay (Coastal 

 Region 6) as compared to areas in Puget 

 Sound (Coastal Region 1) and in New Eng- 

 land (Coastal Region 7). The length of 

 piles may also vary depending on the na- 

 ture of sediments encountered in a re- 

 gion. In areas where bedrock is close to 

 the water body floor, piles would be 

 shorter. The length of friction-type 

 piles will also be affected by sediment 

 characteristics. 



Infestation of piles by marine bor- 

 ers tends to vary geographically. Grib- 

 bles (L imnoria ) breed only in tempera- 

 tures above 57°F (14°C) and are preva- 

 lent in southern California (Coastal Re- 

 gion 2) and from the Gulf coast to the 

 middle Atlantic (Coastal Regions 3, 4, 

 5, and 6) (Lindgren 1974). The abundance 

 and growth rate of shipworms ( Teredo ) 

 also varies geographically. Within a 

 region, factors other than temperature 

 affect marine borer populations. Heavily 

 polluted areas may not be habitable by 



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