2.4 Increases in concentrations of suspended sediments and dissolved 

 nutrients" 



2.5 Introduction of toxic materials to water and soil systems 

 3. Attribute alterations 



The attribute alterations which occur during placement and operation 

 of production facilities are primarily dependent on the location of 

 the facilities. The alterations are similar in scope, but smaller 

 in scale, than those associated with wellsite preparation and opera- 

 tion. Alterations due to placement and operation of units at well- 

 heads are relatively minor and are very similar to those at the 

 centralized production facilities. Therefore, they will not be 

 considered further. 



Vegetation is trampled and perhaps removed in a small area during 

 installation of the centralized production facility. Insects, 

 periwinkles, and meiofauna are also eliminated in this 0.4-ha (1-acre) 

 zone. This removal represents a loss of food and cover for all the 

 remaining consumer groups - waterfowl, wading and shorebirds, mammals, 

 aquatic invertebrates, and fish. However, these losses are insig- 

 nificant at the ecosystem level. 



Short-term increases in suspended sediments and nutrients result 

 from construction activities. 



Although care is taken to avoid large-scale spills at the central- 

 ized facility (specialized drain structures on platform floors, 

 dikes, checking and maintaining equipment), small amounts of toxic 

 materials are released to the water and soil systems over a long 

 time period. These materials may include oil, gas, grease, gasoline, 

 exhausts, herbicides, and a variety of other chemicals used in the 

 operation of equipment. If brine is discharged into an area of 

 moving salt water, little or no effects are expected. The particu- 

 lar kinds and amounts of these substances, and hence their effects, 

 are site specific. Consequences may involve vegetation and/or 

 consumers over a long period of time, and could therefore range from 

 insignificant to highly significant. Major spills and cleanup 

 operations are treated in a later phase of this section. 



The constant traffic necessary for monitoring, maintaining, and 

 adjusting the units at the wellhead and the centralized facility 

 causes an increase in water turbidity, especially when boats are 

 used in canals. The extent of this effect on primary production and 

 the benthos is directly proportional to traffic flow. 



198 



