2.4 Increased concentration of suspended sediments and dissolved nutri- 

 ents 



2.5 Blockage or alteration of normal waterflow pathways 



2.6 Alteration of surface elevation 

 Attribute alterations 



Attribute alterations associated with line installation vary widely 

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

 methodology. Three general categories of lines, segregated according to 

 the similarity of ecological effects are described: (1) surface flow- 

 lines, and occasionally some supply lines, which transport well products 

 to treatment or disposal facilities, as well as bring some water and gas 

 to drilling or production sites; (2) permanently buried gas and oil pipe- 

 lines which transport products to distribution or additional refining 

 centers; and, on rare occasion, (3) permanent overhead electrical lines 

 to supply electrical and phone service to production, treatment, and pump 

 station facilities. 



In many instances surface supply lines and flowlines and overhead elec- 

 trical lines follow existing natural ridges or access canals where 

 maintenance and repair are 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 significantly contribute to canal -associated effects are 

 considered negligible. Thus, when such lines closely parallel existing 

 marsh roads or dredged access canals, the associated alterations are con- 

 sidered 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 marsh, the magnitude of attribute alterations increases. 

 Whre 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 uprooted and de- 

 stroyed in some localized areas. An immediate loss of wildlife food and 

 cover resources results, but such small losses represent a relatively 

 minor alteration for most mammalian and avian species due to the restric- 

 ted areal extent of the line as compared to adjacent unmodified areas. 

 The effects on the detrital cycle and changes in the waterflow regime as 

 a result of surface changes produced by the vehicular traffic are consi- 

 dered to be of minor consequence to the ecosystem. Heavy vehicular traffic, 

 however, may increase potential waterflow alterations such that 

 subsequent vegetative changes are effected. 



280 



