burial of toxic substances, refilling of all pits, knocking down or 

 breaking earthen levees, leveling the site, and plugging or filling 

 ditches. 



It is unusual for permittees to fill access canals. Since these canals 

 are often used for decades (as long as wells or whole fields are active), 

 there may be a considerable amount of bank erosion, spoil compaction, and 

 subsidence. Usually there is not enough fill material from excavation 

 and maintenance to refill the canal. In most instances fill material 

 would have to be barged to the site, which is often economically unfea- 

 sible. Consequently canals are often simply abandoned, though in places 

 where significant canal water movement posed problems, canal plugs have 

 sometimes been constructed. 



Natural processes are typically relied upon to reestablish vegetative 

 ground cover. If major earthwork is required, heavy construction machin- 

 ery, barges, and/or marsh buggies are employed in a manner similar to 

 that described for site access and site preparation. 



Primary ecological alterations 



2.1 Temporary loss of producer biomass along flowlines, vegetated levees, 

 and pad sites 



2.2 Loss of consumer biomass in access canals and pipeline canals due to 

 refilling procedures 



2.3 Increase in producer biomass on formerly barren sites due to revege- 

 tation 



2.4 Increase in suspended sediments and dissolved nutrient concentrations 



2.5 Alteration of midofied circulation patterns as a consequence of 

 reestablishing former marsh flow regimes 



Attribute alterations 



Procedures which reestablish the original marsh surface contours, either 

 through the reworking of altered substrates or by counteracting subsidence 

 effects, are most beneficial in restoring the integrity of the site and 

 ecosystem. Flow patterns interrupted by levees and diversion canals are 

 reestablished. Backfilling, canal plugging, levee removal, and levee 

 breaching procedures remove or alter such obstructions to facilitate 

 restoration of the original flow patterns. Average water depth and sus- 

 pended sediment load determine the nature of the dominant vegetation by 



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