Small vessels, crew boats, supply boats, and tugs may move to the 

 dredging site daily. Alternatively, marsh buggies may be used for 

 such functions. After the wellsite location is dredged (usually 50 

 by 115 m or 150 by 350 ft), all equipment moves out of the area. 

 Redredging may be necessary once e'jery six months to once ewery five 



yr. 



2. Primary ecological alterations 



2.1 Creation of ruts or depressions in land surface (marsh buggy 

 tracks) 



2.2 Loss of vegetation along canal route due to excavation and 

 covering by spoil during initial dredging and maintenance 



2.3 Creation of pathway about 3 n (8-10 ft) deep for increased 

 saltwater inundation 



2.4 Increases in concentrations of suspended sediments and dis- 

 solved nutrients 



2.5 Blockage of normal surface-water runoff pathways 

 3. Attribute alterations 



Surveyors and their equipment trample and crush vegetation outside 

 the zone to be excavated, but the area involved is small. Further- 

 more, much of this trampled area may be covered by spoil as the 

 dredging proceeds. A more significant vegetation loss occurs during 

 excavation of a 23-m (70-ft) wide canal and a 0.58-ha (1.2-acre) 

 wellsite and burial of a considerable portion of bordering marsh by 

 spoil. The area of the latter zone is dependent upon the type of 

 spoil dis'posal technique, but the total area of marsh affected may 

 be as much as five times the width of the canal itself. This direct 

 loss results in an immediate decrease in food and cover for the 

 consumers in the area. For a single canal through a salt marsh, the 

 total area affected may be small in comparison to the remaining 

 productive vegetation, and the impacts on animals, nitrogen fixation, 

 and detritus export can be minor. Relative effects depend on the 

 size of salt marsh; as each new canal and wellsite is excavated, the 

 carrying capacity of the intact salt marsh is decreased. Cumulative 

 effects are unknown, and the threshold point (where one additional 

 well will significantly affect the marsh) is obscure. 



184 



