the affected area is close to the estuary, the frequency of inunda- 

 tion and detritus export may remain unchanged. However, the depres- 

 sions allow faster movement of water in both directions. This 

 results in an increase of turbidity and a decrease in the efficiency 

 of the detritus-filtering mechanism of the salt marsh. Thus, a net 

 increase of exported detritus could result. Net amounts of nutri- 

 ents and sediment probably would not change significantly. 



If the affected area is further removed from the estuary where 

 isolated ponds may exist, intramarsh circulation could be affected. 

 Depressions could connect individual water bodies and increase the 

 intermixing of their contents. Waterfowl and wading bird use would 

 be expected to increase in these new deprestions with standing water. 

 At the ecosystem level, however, this increase is slight. 



Disturbance factors should be recognized as an important considera- 

 tion because they extend the effects of the project beyond the 

 boundaries of the immediate site. 



Key attribute alterations 



The significance of vegetation and consumer losses due to the spill 

 per se is proportional to the size of the spill, the area covered, 

 and the chemical composition of the petroleum. The extent of this 

 alteration cannot be predicted. The alteration which potentially 

 leads to the most long-lasting impacts on the ecosystem is the 

 creation of depressions in the land surface. Effects which are 

 large in areal extent and long-term may result from induced changes 

 in waterflow regimes. As discussed earlier, the total area affected 

 (and thus, the kinds and numbers of vegetation and consumers) is 

 site specific. 



Site shutdown and restoration. 



1. Activity sequence 



The activities of site shutdown and restoration are inherently 

 similar to those of site access and site preparation. Termination 

 of production at the wellsite involves the pulling of all tubing and 

 downhole equipment. This requires a small rig. It will be barge- 

 mounted for marine sites and truck-mounted for road-accessed sites. 

 Dredging may be necessary at a marine site to accommodate barge 

 traffic. Precautions are necessary during all activities to control 

 waste liquids associated with equipment removal. The bore is filled 

 with mud and capped with cement; this material is trucked or barged 

 to the location. Casing is cut well below ground level, and the 

 wellhead area is filled. Some surface equipment may be reconditioned 



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