Biological impacts of construction 

 and existence of groins, bulkheads, re- 

 vetments, and large breakwaters are 

 discussed in those sections of this re- 

 port. Data at hand afford no indication 

 of the possible impacts of sandbag sill 

 placement, but some inferences may be 

 made as to type and degree of probable 

 effects. 



Sandbags sills are long polyvinyl- 

 chloride-coated nylon bags (Dura-bags) 

 filled with sand. Their dimensions are 

 13 ft (4 m) long, 5 ft (1.5 m) wide, 

 and 2 ft (0.6 m) high. They are plac- 

 ed in the intertidal zone, usually less 

 than 5G ft (15 m) channelward of the 

 mean high waterline. When filled, each 

 bag weighs 4 tons (3.6 metric tons), 

 which is more than waves in the bay 

 can move. Cost is reported as varying 

 from $50 to $150 depending on whether 

 professional help was obtained (Greer 

 1976). 



No data on the construction effects 

 were found. Placing the sill breakwaters 

 amounts to pumping them full of sand 

 and locating them parallel to the erod- 

 ing shoreline. The area directly beneath 

 each bag would be lost as habitat and 

 the source of sand cculd cause some de- 

 pletion elsewhere. Without specific in- 

 formation on construction methods, no 

 further impacts can be predicted. 



Once placed, sandbag sills have 

 shown themselves to be very effective 

 in rebuilding beaches in the Chesapeake 

 Bay. In one case a beach was doubled 

 in width in three weeks (Greer 1976). 

 How this local accretion affects adjacent 

 beaches is not stated. The U.S. Army 

 Engineer District, Norfolk (1977e, un- 

 dated b), predicts no adverse effects 

 due to flood height and drift, reduction 

 of erosion, or accretion on beaches. 

 They also expect no adverse effects on 

 water quality, water supply, or aesthet- 

 ics. Warning signs are recommended to 

 prevent boaters from hitting the sills, 

 which are submerged at least during 

 high tide. 



Prevention of the shoreline erosion 

 should have beneficial effects on the 

 biological resources of the area. Upland 

 vegetation loss would be reduced and, 



thus, loss of wildlife habitat would be 

 slowed (U.S. Army Engineer District, 

 Norfolk undated b). The effects on in- 

 tertidal biota would depend, in part, on 

 the amount of sand deposited, and how 

 rapidly deposition occurred. Since ero- 

 sion and accretion are natural process- 

 es, many intertidal organisms can adapt 

 to changing bottom levels. Fish should 

 be little affected except that reduced 

 turbidity might prove beneficial. With 

 no action, erosion might continue. The 

 dredging for beach nourishment is a 

 biologically more harmful alternative, as 

 well as being costly. 



Additional information is being de- 

 veloped from ongoing studies at Virginia 

 Institute of Marine Science concerning 

 sandbag sills in Chesapeake Bay. 



CASE HISTORY - PIERS, PILINGS, 

 AND OTHER SUPPORT STRUCTURES 

 IN COASTAL REGION 7 - NORTH 

 ATLANTIC 



The literature contains very little 

 information on piers and pilings in the 

 Coastal Region 7. Carstea et al. (1975a) 

 present a theoretical case study of a 

 200-ft (61-m) timber pier in the north- 

 eastern United States. A developers' 

 handbook which contains some informa- 

 tion on this topic for Connecticut is 

 presented by Carroll (undated). 



The construction of a timber pile 

 pier is usually of short duration. For 

 example, Carstea et al. (1975a) estimate 

 construction time of a 50-ft (15-m) long 

 pier at 2 to 4 days, using trucks for 3 

 hr, a piledriver for 1 hr, and a crane 

 for 10 hr. A slight increase in water 

 turbidity and sedimentation may result. 

 Increased noise and air pollution levels 

 are usually not excessive. 



This region is characterized by 

 numerous types of environments (Vir- 

 ginia Institute of Marine Science 1976). 

 Consequently, impacts on the environ- 

 ment due to a specific type of structure 

 will vary from place to place. Effects of 

 a pier on areas such as wetlands, tidal 

 flats, grassbeds, breeding nurseries, 

 wintering and feeding areas, and migra- 

 tion pathways are the most significant 

 (Carstea et al. 1975a). Productivity 



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