The principal impact of wharves and piers is loss of intertidal habitat. This 

 impact is significant in developed harbors, such as Portland (region 1), 

 Boothbay (region 2), Rockland (region 4), Lubec (region 6), and Eastport 

 (region 6) , where relatively large areas of the intertidal zone may be covered 

 by such structures. Piers can change local current patterns and may affect 

 the benthic fauna adversely by changing sediment distribution and types. 



An additional impact of piers and wharves is lowered productivity of benthic 

 algae due to the shading of bottom sediment. Reduction in the productivity 

 of benthic algae may cause a local reduction in some species. Impacts of 

 waste water discharge associated with piers and wharves are discussed under 

 "Population and Industry" below. Dams and wharves may provide additional 

 substrata for epilithic algae, which may increase productivity locally. 



Dredging 



Dredging is the removal of land or bottom materials from wetlands, open water, 

 or other coastal habitats (1) to obtain sand, shell, or gravel deposits, (2) 

 to establish a commercial, industrial, or residential facility, or (3) to 

 create or maintain channels (Metzger 1973). Most of the dredging in Maine is 

 associated with the maintenance of commercial navigation channels and is 

 regulated by the U.S. Army Corps of Engineers. 



The areas most frequently dredged during the past 20 years are Portland 

 Harbor, the Kennebec River, the Penobscot River, Rockland Harbor, and the 

 Royal River. Periods between dredging operations vary from 2 to 23 years. 

 Locations and dates of dredging projects, the cubic yards of material removed, 

 and locations of disposal sites are given in table 3-4. Other disposal sites 

 for private dredging exist (permits are required) and the specific coordinates 

 of these can be found in files of the regulatory branch of the U.S. Army Corps 

 of Engineers, Waltham, MA. Atlas map 3 depicts dredge removal and disposal 

 sites in coastal Maine. Disposal sites in Maine are usually deep oceanic 

 areas but are not restricted to such areas. Other disposal sites include land 

 areas, beaches, bays, and channels in estuaries and rivers. 



The basic modes of dredging are mechanical and hydraulic. Mechanical dredges 

 generally employ a crane and a large bucket or a large power shovel to remove 

 sediment. The spoil is dumped overboard or into a barge that is then towed to 

 a disposal site. Hydraulic pipeline dredges pick up material by cutterhead 

 and transport it by suction-pipe to the disposal site (Clark 1977). Dredge 

 material (spoil) in Maine usually consists of sand, soft mud, and a small 

 amount of rock. In Maine mechanical dredges usually are employed in Maine due 

 to the relatively coarse nature and low volume of materials that are dredged 

 there. 



The impacts of dredging operations can be classified into two major groups: 

 (1) those that are the result of the removal of material and (2) those that 

 are the result of material disposal. Impacts of material removal include the 

 loss of natural habitat, alterations of water circulation patterns, increased 

 turbidity, the release of trapped pollutants and organic matter, and the loss 

 of beach sediment supplies. Disposal of some dredged material (e.g., sand and 

 rock) results in new barren habitats in upland areas and increased 

 sedimentation on down-current substrates in open water. 



3-15 



10-80 



