The ring levee may influence water flows by isolating/filling depres- 

 sions or blocking small drainages. For a single leveed site, the 

 effects are usually localized and small when compared to (1) the 

 remaining unaffected marsh and (2) the effects of road construction. 

 The exterior borrow pits can affect a larger area of marsh than the 

 ring levee. The zone(s) affected depends upon the placement pattern, 

 depth, and surface area of these pits. They may remain as isolated 

 ponds of standing water which collect runoff via intercepted drain- 

 age, or they could become interconnected due to drainage channels 

 and/or consumer usage (compaction of pathways between ponds). The 

 drying effect of this increased drainage may or may not lead to 

 vegetation changes in adjacent lands. The total area affected may 

 be several times the wellsite area; the frequency of inundation is 

 usually not affected. Hence, impacts on the functioning of the 

 ecosystem by a single wellsite are usually limited. 



The borrow pits around the wellsite levee create a new habitat that 

 favors phytoplankton and consumers associated with deep standing 

 v;ater bodies. Alligators may be attracted to these ponds and may 

 cause their interconnection due to the trails they leave when moving 

 from one pond to another. Waterfowl and wading shorebirds may be 

 attracted if populations of small fish and invertebrates inhabit the 

 borrow pits, though their presence will increase only when human 

 disturbance is minimal. 



The total net primary production will decrease in the borrow pits 

 since the marsh plants are removed (Darnell, 1976). The biomass of 

 consumers in the pit area may decrease or increase depending upon 

 whether the original marsh had standing water upon it or was rela- 

 tively dry. Comparisons of biomass between marsh areas and canals 

 have generally shown biomass decreases in the newly created aquatic 

 systems (Trent et al., 1972). These changes are usually limited to 

 the borrow pits themselves and the immediate adjacent areas of 

 marsh. 



During this phase of operations (one to three months), the water and 

 soil systems are exposed to a wide variety of pollutants, from drill- 

 ing mud, sump discharge, and vehicle and equipment waste (exhausts, 

 oil, grease, gasoline). The kinds and amounts of these materials, 

 and hence their effects, are site specific. Consequences may 

 involve vegetation and/or consumers (over a short or long period of 

 time) and, therefore, could range from insignificant to highly 

 significant. Spills and cleanup operations are treated in a later 

 section of this report. 



Displacement due to activity and noise during construction is short 

 term since the operation takes only 10 to 14 days. However, subse- 

 quent activities, drilling and production, may continue for months 

 or years, and the area affected extends considerably beyond the 

 leveed site and borrow pits. 



220 



