advantages include fewer adverse envi- 

 ronmental impacts and ease of removal if 

 so desired. Open-pile structures are 

 also advantageous where substrate con- 

 ditions are unstable. Adequate spacing 

 of piles is important to prevent inter- 

 ference with water and sediment move- 

 ment (Bauer 1973). 



Site characteristics should influ- 

 ence the design of a pier. According 

 to the Coastal Plains Center for Marine 

 Development Service (1973), floating 

 piers can affect beach sand movement. 

 They recommend open pile piers in the 

 areas of significant littoral transport 

 and longshore currents. Floating piers 

 are suggested for areas where visual 

 impacts should be minimized and where 

 boat traffic would not be hindered by 

 their presence. 



Another factor to consider is tidal 

 range. Where the tidal range is above 

 4 ft (1.2 m), floating piers are recom- 

 mended because they provide easier ac- 

 cess to boats throughout the tidal cycle 

 (Ayers and Stokes 1976). Floats can be 

 removed in the winter to avoid ice dam- 

 age (Carstea et al. 1975a). 



During the life span of pilings or 

 a pile-supported structure, several 

 changes usually occur which should be 

 considered in the design. These changes 

 alter the impact of forces acting on the 

 structure. As marine growth increases 

 on the pile, the diameter, roughness, 

 and concomitant drag coefficient will in- 

 crease. Scouring at the base of the pile 

 will decrease pile support. Also, as 

 piles are attacked by wood borers or as 

 they corrode, structural damage will de- 

 crease pile strength. (See U.S. Army 

 Corps of Engineers 1973b for further 

 information and calculations). 



The type of wave force occurring 

 in the area should also be considered in 

 the design. For example, breaking 

 waves create a greater force on the pile 

 than do nonbreaking waves. (U.S. 

 Army Corps of Engineers 1973b should 

 be consulted for further information and 

 calculations.) The size, number, and 

 placement of piling should be correlated 

 to the various energy zones in which 

 the pier is located. 



Socioeconomic . The number and size 

 of pile-supported structures and piers 

 should be minimized in a given area. 

 The use of over-water locations for non- 

 water-dependent structures should be 

 discouraged (Carstea et al. 1975a). To 

 limit the number of piers.it is suggest- 

 ed that single piers be used coopera- 

 tively by the community. This is par- 

 ticularly stressed for subdivisions, 

 motels, and multiple dwellings (South 

 Carolina Marine Resources Division 

 1974). Structure size should be re- 

 stricted to that which is necessary for 

 designated purposes. Piers should not 

 hinder public use of the water, 

 navigation, or adjacent shoreline. Ex- 

 tension of the structure beyond the mean 

 high water line should be avoided (Car- 

 stea et al. 1976). The socioeconomic 

 impacts of public, private, or joint use 

 of a pier should be considered. 



Biological. During construction, 

 turbidity should be kept to a minimum 

 and turbidity control devices should be 

 used when necessary. Alterations of 

 shoreline and littoral habitat should be 

 avoided (Florida Game and Freshwater 

 Fish Commission 1975). The placement of 

 the structure relative to the sun, as 

 well as the height and width of the 

 deck, are important factors to consider. 

 The structure should be placed high 

 enough above the water or marsh surface 

 to prevent shading. A narrow pier ex- 

 tending from north to south would not 

 produce as much shade as a wide pier 

 running from east to west(Gifford 1977). 

 The damage to wetlands can be minimized 

 by constructing an elevated boardwalk to 

 provide access to the dock or pier (En- 

 vironmental Quality Laboratory Inc. 

 1977). The size, number, and placement 

 of piling should be evaluated relative 

 to the various biological zones over 

 which the pier will extend. 



Construction Materials 



Piers, pilings, and structure sup- 

 ports are generally constructed of wood, 

 concrete, or steel. Decking, stringers, 

 bents, and caps are made from wood, 

 steel, or concrete members of various 

 sizes (Figure 44). Construction materi- 

 als that do not release toxic substances 

 are preferred. 



85 



