upstream from the confluence with the Settles River and Snowdon Creek, 

 respectively, and 8 km from the upstream site. 



The upstream site was excavated in an al luvial gravel deposit within 

 the active f I oodp I a i n of the Dietrich River. Between late summer 1974 and 

 early 1977, 631,000 m of gravel was removed from the 35-ha site for con- 

 struction of the Trans-Alaska Pipeline. A dike was constructed across an 

 intermittent channel north of the gravel removal area to divert active flow 

 or seasonal ly high water away from the material site. 



Two methods were used to remove gravel. Most of the site was scraped 

 to an average depth of 3 m while a pit was excavated by dragline in the 

 southern end of the work area. This pit is approximately 240 x 90 m and 

 was excavated to an average depth of an additional 2 m below the scraped 

 portion of the gravel removal area. Within this pit two deeper holes approxi- 

 mately 9 m deep were excavated. Ground springs were encountered during the 

 scraping operation. The ground springs have been diverted through two chan- 

 nels into the deep pit. Aufeis formation was a natural occurrence in this 

 area before gravel removal and was observed downstream from the pit drainage 

 channel during the first winter following excavation. 



A screening-crushing operation was used to produce pipeline padding and 

 bedding material; stockpiled processed material also was stored at this 

 location. The material site was utilized as a concrete fabrication area 

 in August 1975 to produce cement castings of pipeline weights. 



In the summer of 1977 the area was sloped and contoured to drain water 

 into the gathering channels leading to the deep pit. The southern and north- 

 ern portions were then reseeded with annual grasses. The central portion was 

 left open for access to stockpiled maintenance and operation gravel for the 

 Trans-Alaska Pipeline. 



The Dietrich River-Downstream site was worked by shallow excavation 

 of a gravel deposit within the active floodplain of the Dietrich River. 

 Gravel was removed from the 7.5-ha site with 128,590 m of material ex- 



54 



