Short-term increases in suspended sediments and nutrients result from 

 construction activities. Longer term increases resulting from erosion of 

 the ring levee are of minor consequence. Neither the short-term nor the 

 long-term increase has a large effect on the surrounding area, especially 

 if the levee surface revegetates quickly. 



The ring levee may influence water flows by isolating/filling depressions 

 or blocking small drainages. For a single wellsite, the effects are 

 usually localized and limited when compared to (1) the remaining unaffec- 

 ted marsh and (2) the effects of road construction. The exterior borrow 

 pits can affect a larger area of marsh than the ring levee. The zone(s) 

 affected depends upon the placement pattern, depth, and surface area of 

 these pits. They may remain as isolated ponds of standing water which 

 collect runoff via intercepted drainage, or they may become intercon- 

 nected due to drainage channels and/or consumer use (compaction of 

 pathways between ponds). The drying effect upon the marsh soil of this 

 increased drainage may or may not lead to vegetation changes in adjacent 

 lands. However, unless major drainages are involved, the total area 

 affected is little more than the construction site, and the impacts on 

 the functioning of the ecosystem are small. 



Replacement of marsh vegetation and soil by deep borrow pits results in 

 increased habitat for species preferring deeper aquatic areas. However, 

 net production of organic material per unit area declines with loss of 

 rooted marsh plants. Alligators, waterfowl, and wading and shorebirds 

 may increase their use of these ponds if human activity is minimal, 

 turbidity is low, and production of primary consumers is high. At the 

 ecosystem level of organization, however, these changes are small and of 

 little consequence. 



During this phase of operations (one to three months), the water and soil 

 systems are exposed to a wide variety of pollutants from drilling mud, 

 sump discharge, and vehicle and equipment waste (exhausts, oil, grease, 

 gasoline). The kinds and amounts of these materials and the number of 

 site-specific variables involved make prediction of their effects 

 difficult. Spills and cleanup operations are treated in a later phase of 

 this discussion. 



Unlike the previous phases of activity, the preparation and operation of 

 a wellsite involves continuous movement, noise, and long-term distruption 

 of sensitive wildlife species. Consequently, the activity extends the 

 effects of the project beyond the boundaries of the immediate site and 

 for a protracted period. 



Key attribute alterations 



They key attribute alterations include direct removal of vegetation and 

 consumers, localized changes in land elevation, and introduction of 



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