timber. Tie rods (sometimes referred 

 to as tie backs) when made of steel 

 cable should be coated or wrapped to 

 prevent corrosion (Collier 1975). Tie 

 rods function to prevent seaward tip- 

 ping of the bulkhead and must be se- 

 curely anchored. Anchors typically are 

 deadmen (horizontally placed timbers), 

 anchor piles, or concrete anchor blocks. 



Construction materials used for toe 

 protection and filters are similar to 

 those used for revetments. 



Expected Life Span 



The expected life span of bulk- 

 heads ranges from 10 yr to approximate- 

 ly 30 yr. Life span is site specific and 

 will depend upon location of the struc- 

 ture on the beach, design wave height 

 and period, construction materials, and 

 climatic conditions. 



Timber and steel sheet pile bulk- 

 heads have shorter life spans in warmer 

 climates. Deterioration of wooden struc- 

 tures from decay, insects, and marine 

 borers is accelerated, as is the corro- 

 sion of steel structures. Collier (1975) 

 related one instance in Florida where a 

 temporary wood work trestle, built from 

 450 untreated pine piles, was rendered 

 unsafe for work after only 3 mo of ser- 

 vice due to shipworms. The life span 

 of steel structures may be less than 10 

 yr in warm marine environments if the 

 steel is not coated or of a resistant 

 chemical composition (Collier 1975). 



Very little data are available to 

 assess the actual durability of various 

 bulkhead types. However, several au- 

 thors have pointed out that bulkheads 

 do not provide a long-term permanent 

 solution to shoreline erosion because the 

 beach will continue to recede (Coastal 

 Plains Center for Marine Development 

 Service 1973, U.S. Army Corps of Eng- 

 ineers 1964, 1971b). This recession may 

 even be accelerated as a result of wave 

 reflection from the bulkhead(Figure 28). 



S ummary of Physical and Biological 

 Impacts 



Construction effects . Construction 

 of sheet pile bulkheads involves trans- 

 porting materials to the site, driving or 



jetting piles and sheet piles, placing 

 and securing tie rods and anchors, and 

 backfilling behind the bulkhead. These 

 activities require a truck for material 

 transport, a bulldozer, a pile driver or 

 pile jetting equipment, a crane for lift- 

 ing heavy piles, anchors, and walers, 

 and dredging equipment if fill material 

 is obtained by dredging. Other types of 

 bulkheads require similar equipment. 



This heavy equipment causes noise 

 and air pollution at the site. Carstea 

 et al. (1975a) maintain that air pollu- 

 tion, resulting from construction of a 

 150 ft (45 m) timber bulkhead, should be 

 well below Federal air quality standards 

 and that noise will have an effect on 

 areas within about 200 ft (61 m) from 

 the site. However, construction noise 

 may be sufficient to disrupt waterfowl 

 which may be nesting or resting at or 

 near the site. 



Fish and wildlife habitat is dis- 

 rupted and/or lost due to construction 

 activities. Damage to fish and wildlife 

 resources depends upon the type of hab- 

 itat in the area prior to construction, 

 where the structure is placed on the 

 shoreline, its size, and construction 

 methods. The bulkhead and associated 

 backfilling bury established terrestrial 

 and intertidal flora and fauna. The 

 heavy equipment used during construction 

 disturbs vegetation behind the structure 

 (Knutson 1977). In areas where bul knead- 

 ing and backfilling are used to create 

 shorefront real estate, bulkhead con- 

 struction impacts represent the first 

 step in a chain of events which lead to 

 larger losses due to land development 

 behind the bulkhead. Benthic habitat, 

 in addition to terrestrial and inter- 

 tidal habitat, is also lost if dredging 

 is used to obtain fill material or to 

 create a channel up to the bulkhead. 



Construction activities will cause 

 local erosion and new sediment deposits 

 in the vicinity of the bulkhead due to 

 disturbance of bottom sediments during 

 dredging, pile driving or jetting, and 

 backfilling. New sediment deposits are 

 often silty and can destroy spawning 

 areas, smother benthic organisms, and 

 reduce bottom habitat diversity and food 

 supply (Carstea et al. 1975b). 



53 



