The degree and significance of wildlife displacement resulting from 

 gravity-meter surveys are slight. This is because of the small number of 

 people and short period of time required to complete a survey (less than 

 a week), as well as the lack of noise. 



4. Key attribute alterations 



The potential alteration which could lead to a significant impact 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 of adjacent systems (if levees are breached). 

 These effects, of course, can occur only if trucks, buggies, or other sur- 

 face vehicles are used. The total area affected (and thus, the kinds and 

 number of consumers) is site specific. 



Site access 



By road . Existing natural or man-made levees or spoil banks must meet at 

 least two criteria in order to be realistically considered as sites for road- 

 ways to wellsites: (1) they must be well aged so that the degree of compaction 

 is sufficient to accommodate heavy equipment and (2) they msut be aligned such 

 that they approach the wellsite location. In a restricted number of cases, 

 these criteria may be met. If so, the levee will be "improved" in order to 

 convert it to a usable roadway. Excavation of borrow pits, piling of spoil, 

 creation of ruts, and additional construction activities/ impacts are not 

 necessary. Hence, conversion generally involves the placement of boards 

 and/or additional surfacing on top of the levee. In some cases it may be 

 necessary to widen or reinforce narrow portions of the levee. 



The conversion activities will remove a stirp of vegetation about 10 m 

 (30 ft) wide along the top of the levee. An additional alteration involves 

 displacement of wildlife along the route. There may be effects on adjacent 

 ecosystems during the construction/conversion activities, but these impacts 

 are too site specific to be predictable. Further consideration of this possi- 

 bility is not warranted. For a complete discussion of typical road-building 

 alterations, see "Site access by leveed road" in the brackish marsh and 

 coastal uplands sections of this chapter. The latter section would be more 

 applicable to road building on a broad terrace or chenier. 



By canal . The occasions when this phase of oil and gas operations will 

 affect levee/spoil systems fall into two categories. The first category 

 includes cases where a natural levee, a man-made levee, or a small/narrow 

 spoil deposit is completely breached by an access canal. In this situation 

 the affected area on the levee system is confined to a 23-m (70-ft) wide strip, 

 which is replaced by a canal. Unless a particular levee exists in an area 

 having a high density of wells, disturbed locations will be infrequent and 

 widely spaced. Since the objective is to go through the levee, the absolute 

 amount of lost habitat is generally small. However, the relative importance 



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