moisture and soil air characteristics. Dissimilar substrates (in 

 salinity, texture, structure, fertility) alter microenvironmental 

 conditions such that subsequent plant assemblages different from the 

 original flora may result. The significance of such abiotic alterations 

 upon biotic components is a function of the lateration's areal extent, 

 existing site conditions (whether natural or impacted), and future site 

 uses. 



Wildlife displacement will probably be temporary, lasting only as long as 

 is necessary to clean up the site and repair equipment. Cleanup activi- 

 ties concentrated within an existing use area generate few additional 

 disturbances. In some instances displacement actions may need to be 

 deliberate to scare wildlife and waterfowl away so they will not come in 

 contact with noxious materials. 



4. Key attribute alterations 



The primary alteration is the complete or partial removal of vegetative 

 components resulting from several aspects of the cleanup procedure. 

 Removal produces community disruptions which require reestablishment of 

 new equilibrium conditions through competitive biotic processes. Domina- 

 ting influences of soil moisture and solar energy are reordered such that 

 resource availability is increased, at least temporarily, allowing sup- 

 pressed flora or earlier serai stages to appear. Consumer response varies 

 by species, size of the area affected, and the extent of the floristic 

 change. Cleanup methodology determines site alterations that occur, and 

 whether subsequent biotic changes are temporary or long term. 



Insufficient data exist to facilitate accurate evaluation of whether 

 greater detrimental effects result from the introduction of petro- 

 chemicals into levee systems or from the cleanup efforts (cutting, 

 burning, soil extraction) directed at their removal. 



Unless a levee is fairly extensive and has a primary pipeline or flowline 

 rupture on it, spills are going to be of little consequence to this system. 



Site shutdown and restoration. 



1. Activity sequence 



Completion of exploratory drilling, removal of production facilities, pipe- 

 line installation and trench backfilling, spill cleanup, or road abandon- 

 ment usually signals initiation of the shutdown and site restoration phase. 

 Structures, equipment, concrete foundations, pipes, wellcasings, drilling 

 mud, and other artifacts of oil production are removed if they possess 

 salvage or reuse value. Otherwise, only as much attention is paid to 



313 



