Attribute alterations 



Attribute alterations associated with line installation varies 

 widely depending on the type and size of line, site location, and 

 placement methodology. Three general categories of lines, segre- 

 gated 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 follow existing leveed roadways or access canals 

 where maintenance and repair are easily 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. Distinguishable 

 effects attributable to line installation that exceed or signifi- 

 cantly contribute to effects associated with leveed roads or canals 

 are considered negligible. Thus, when such lines closely parallel 

 existing marsh roads or dredged access canals, the associated alter- 

 ations are considered to be of minor consequence to the ecosystem as 

 compared to the effects produced by prior access-associated activi- 

 ties. 



However, when surface flowlines or supply lines require overland 

 routes through unmodified brackish marsh, the magnitude of attribute 

 alterations increases, f'^rsh buggies transporting work crews and 

 supplies along the line trample and crush vegetation. Depending 

 upon soil moisture conditions and number of vehicle traverses 

 (typically restricted to two or three trips), the vegetation may be 

 completely uprooted 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 areal extent of 

 the line as compared to adjacent unmodified areas. The effects on 

 the detrital cycle and waterflow regime (as a result of little tidal 

 amplitude and only a limited number of vehicular trips) are con- 

 sidered to be of minor consequence to the ecosystem. 



A relatively small amount of dredging may be necessary where these 

 small lines cross existing watercourses. The concentrations of sus- 

 pended nutrients and sediments are temporarily increased in local- 

 ized areas near the site. 



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