occur location should be selected so that view of the site is blocked from 

 vantage points. For example, the Tanana River-Downstream pit, which is large 

 and contains very clear water, is in a floodplain where the river channels 

 are highly turbid, thus, offering a dramatic visual contrast. However, the 

 site is situated on an island completely surrounded by a heavily wooded 

 buffer zone which blocks view of the site from the Richardson Highway. The 

 pit is visible only from the air. 



Pits are often excavated with angular perimeters that ignore natural 

 land contour. Since angularity is not characteristic of naturally formed 

 aquatic systems the usual pit site offers some contrast even in areas where 

 lakes and ponds occur natural ly. Excavating these sites with perimeters that 

 blend with natural land contours, such as in abandoned river channels, de- 

 creases the visual diversity that will result from development of pit sites. 

 The West Fork Tolovana River and Tanana R i ver-Upstream sites are excellent 

 examples of this management technique (refer to Figures 63 and 70). 



Pit sites require considerably less area to obtain a given amount of 

 gravel than do areas that are surface scraped. Because of the depths nor- 

 mal ly required, subsurface waters are exposed, usual ly fill ing the pit 

 during site operation. This water poses problems for the efficient extrac- 

 tion of materials but, since draglines or backhoes are usually used for 

 excavation, the presence of water does not prevent the removal of gravels. 

 Pumping is the only method used to eliminate the water but even this is 

 impossible in some systems because of the volume of subsurface flow through 

 floodplain gravels. During mining, the water in a pit is usually highly 

 turbid and should not be pumped into adjacent channels. 



In summary, there is little doubt that the excavation of a pit materi- 

 al site creates significant change in a floodplain environment (Table 41). 

 If situated and operated properly, the hydraulics of the river system are 

 little affected whereas significant changes occur to the terrestrial system 

 and the scenic quality of the area. Differences in water quality and aquatic 

 biota can be expected between a pit and the adjacent channel regardless of 

 whether they are connected. The increase in both aquatic and terrestrial 



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