required wherever a canal intersects another waterway. Whenever open 

 water is traversed, the same equipment is used, although only a trench 

 will be dredged. If a hydraulic dredge is used, spoils may be pumped to 

 nearby land, dispersed over the adjacent area, or piled upon in a spoil 

 island. Normally, flotation canals are not backfilled due to their large 

 size. Straight open-water canals flanked by low spoil levees are the 

 final product of the flotation method. 



Inland fresh marsh sites too small or shallow to permit use of barge- 

 mounted dredges may require the use of a tracked dragline moving over 

 wooden mats or a marsh buggy dragline. A marsh buggy dragline consists 

 of a dragline mounted on a marsh buggy carriage similar to that used to 

 carry seismic equipment. It is a motorized tracked vehicle equipped with 

 large flotation pontoons. A ditch is cut for floating in the pipe, thus 

 eliminating the necessity for dredging a full-scale canal to accommodate 

 a pipeline laying barge. While this type of operation produces far less 

 spoil, marsh buggy tracks often cause pronounced changes in the marsh 

 surface. 



Once pipelines are pressure checked and operating, they are periodically 

 inspected for leaks; boats, marsh buggies, or aircraft may be employed. 

 The inspection equipment utilized and traffic frequency depend on the 

 nature of the pipeline, its size, and the local marsh conditions. 



Primary ecological alterations 



2.1 Partial vegetation loss within line easement due to trampling and 

 crushing effects of construction machinery 



2.2 Complete loss of vegetation within a canal zone 10 to 100 m (30 to 

 300 ft) wide and on disjunct spoil disposal areas 



2.3 Partial or complete removal of consumer groups, depending on the 

 type of line placement methodology utilized 



2.4 Increased concentration of suspended sediments and dissolved nutri- 

 ents 



2.5 Blockage or alteration of normal waterflow pathways 



2.6 Alteration of surface elevation 



253 



