3. Attribute alterations 



As was previously discussed, attribute alterations associated with line 

 installation may vary widely, depending on the type and size of line, 

 site location, and placement method. Two general categories of lines, 

 segregated according to the similarity of ecological effects, are des- 

 cribed: (1) surface lines to supply drilling sites with water and gas 

 and (2) permanently buried lines, which includes utility lines (electri- 

 cal, water, gas, and telephone), flowlines (for brine disposal or 

 hydrocarbon transport to treatment facilities), and gas/oil pipelines 

 (for transport of product to distribution or additional processing 

 centers). Surface lines and permanently buried utility lines or flow- 

 lines usually follow the levee alignment where maintenance and repair are 

 easily accomplished. Surface line installation involves laying the pipe 

 or cable segments directly on the surface. Vegetation in the activity 

 area is crushed and trampled; the areal extent, however is limited to a 

 few meters on either side of the line. If the line is buried, a contin- 

 uous- strip about 3 m (10 ft) wide is disturbed during the digging, line 

 placement, refilling, and dressing stages. The entire process is usually 

 quite rapid (requiring only a few days) and is typically restricted to 

 the top of the levee. Vegetation recovery in coastal areas is usually 

 completed within one growing season as the dominant life forms are 

 normally rapid-growth grasses mixed with various herbaceous forbs or one 

 or two characteristic woody composites ( Baccharis spp. and Iva spp. ). 

 Since these ecological alterations are typically small in magnitude, wery 

 localized in areal effect, and usually occur on previously altered or 

 reworked sites, such alterations are considered to be of minor conse- 

 quence to the ecosystem. Other activities usually associated with levees, 

 such as access roads, are capable of generating similar changes, but 

 larger in magnitude, which have the potential for causing basic ecosystem 

 alterations (see the discussion "Access to site" in the coastal uplands 

 section of this chapter). 



Gas and oil transport pipelines, the primary component of concern, are 

 also included within the class of permanently buried lines. The altera- 

 tions associated with this group of lines are usually more extensive, but 

 basically similar, to those associated with buried utility lines and 

 flowlines. The operational scale in all respects, however, is much larger 

 and as a result, several formerly unimportant alterations subsequently 

 require renewed consideration. A typical pipeline easement may be approx- 

 imately 45 m (150 ft) wide, which would result in direct habitat 

 alterations of 4.5 ha per km (18.2 acres per mi) of easement if the pipe- 

 line alignment followed the levee alignment. However, since the pipeline 

 alignment Usually follows a straight-line orientation between two points 

 and the complex of levees and spoil banks is generated in a haphazard 

 fashion, the amount of levee area affected by any particular pipeline 

 operation is usually limited to one transect no wider than the construc- 

 tion easement width. Unless a particular levee exists in a high-density 

 pipeline area, disturbed locations will be infrequent and widely spaced. 

 The relative effect of this disturbed area with respect to the entire 

 levee ecosystem is comparatively minor, since the pipeline simply goes 

 through a small segment of the levee. Adjacent levee areas, which are 



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