3. Attribute alterations 



Attribute alterations associated with line installation vary widely and 

 depend on the type and size of line, site location, and placement methd- 

 ology. Three general categories of lines, segregated according to the 

 similarity of ecological effects, are described: (1) surface supply and 

 flowlines, which provide drilling sites with water and gas or transport 

 well products to treatment or disposal facilities; (2) permanent overhead 

 electrical lines to supply electrical and phone service to production, 

 treatment, and pump station facilities,; and (3) permanently buried gas 

 and oil pipelines, which transport products to distribution or additional 

 refining centers. 



In many instances, surface supply lines and flowlines and overhead 

 electrical lines flollow existing leveed roadways or access canals. 

 Maintenance and repair are thus facilitated. Associated ecological 

 alterations (trampling of vegetation, localized water turbidity, etc.) 

 are typically small in magnitude, ^^ery localized in effect, and occur in 

 already altered locations. Effects attributable to line installation 

 that exceed or significantly contribute to the effects of leveed roads or 

 canals are few. Thus, when such lines closely parallel existing marsh 

 roads or dredged access canals, the installation alterations are consi- 

 dered to be of minor consequence to the ecosystem as compared to the 

 effects produced by prior access-associated activities. 



However, when surface flowlines or supply lines require overland routes 

 through unmodified fresh marsh, the magnitude of attribute alterations 

 increases. Where the marsh is fairly shallow, marsh buggies transport 

 work crews and supplies along the line. Emergent vegetation is trampled 

 and crushed as the surface lines are connected and laid. Depending upon 

 soil moisture conditions and the number of vehicle traverses (typically 

 restricted to two or three trips), the vegetation may be completely up- 

 rooted and destroyed in some localized areas. An immediate loss of 

 wildlife food and cover resources results, but such small losses represent 

 relatively minor alterations for most mammalian and avian species due to 

 the restricted area! extent of the line as compared to adjacent unmodified 

 areas. The effects on the detrital cycle and changes in the waterflow 

 regime produced by the vehicular traffic are considered to be of minor 

 consequence to the ecosystem for similar reasons. Heavy vehicular traffic, 

 however, may increase waterflow alterations such that subsequent vegetative 

 changes occur. 



A relatively small amount of dredging may be necessary where small sur- 

 face lines cross existing watercourses. The concentrations of suspended 

 nutrients and sediments are temporarily increased in areas near the site. 



When large open-water marsh areas are encountered, it is less expensive 

 and usually easier to route small surface flowlines around such natural 

 features. This is accomplished by using existing road and/or canal 



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