alignment. The secondary effect is the associated long-term gradual 

 changes in nearby biota that result from subtle microenvironmental 

 alterations of soil structure, surface water hydrology, partial 

 vegetation removal, and disturbance factors. Changes are expressed 

 as altered plant assemblages which are effected through competitive 

 mechanisms. The species composition and population levels of the 

 consumer groups may or may not respond to secondary habitat altera- 

 tions. 



Response is a function of the area! extent of the change, the size 

 of the consumer's resource base, and the sensitivity of the consumer 

 to altered habitat conditions. Sensitive wildlife species may 

 abandon otherwise favorable habitats because of road-associated 

 disturbances. Conversely, other wildlife species may be attracted 

 to roadsides because of the presence of favored food items that have 

 appeared. 



Wellsite preparation and operation. 

 1. Activity sequence 



Basically the same construction techniques and equipment employed in 

 road construction are used in wellsite preparation. The survey 

 crew enters and stakes the site. Trees or other dense vegetation 

 are removed by clearing crews. Heavy machinery clears the remaining 

 vegetation, then grades and levels the site to plan specifications. 

 Retaining pits, low earthen levees, and other internal earthworks 

 are excavated and shaped. Typical site dimensions are 97 by 122 m 

 (320 by 400 ft). The pad site is surfaced with shell or crushed 

 rock and compacted. Drilling equipment and support facilities 

 arrive, are set up, and exploration commences. Auxiliary equipment 

 and supplies are stored nearby for later use. Vehicles provide 

 transportation. Drilling continues (averages one to three months) 

 until a determination is made whether the well is productive. This 

 decision determines whether the site is placed into production or 

 abandoned. 



2. Primary ecological alterations 



2.1 Creation of an unvegetated wellsite complex typically one to 

 two ha (approximately three to five acres) in area 



2.2 Removal of consumer groups within the wellsite area 



2.3 Loss of soil structure within the pad site due to movement of 

 heavy machinery and construction activities 



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