- The width can be reduced to 20 percent of the 

 recommended minimum at the downstream end of the 

 pit 



- The height of the buffer should be at least as 

 high as the water level during a 20-year flood 



iv) Flood-flow buffers should be designed on a site-specific 

 basis following the guidelines presented in Appendix A 

 under any of the following conditions: 



• The material site is on a very large river (e.g., 

 Yukon River, Kuskokwim River, Tanana River, and 

 Co I V i II e R i ver ) 



• The available space does not allow for a buffer of 

 recommended width 



• Buffer height is lower than the recommended design 

 height 



• The active channel is angled into the bank at an angle 

 greater than about 30 degrees 



• Channel aufeis occurs in the river adjacent to the 

 s i te 



• Banks consist of primarily sands, are sparsely vege- 

 tated, or are ice-rich permafrost material 



• Evidence of active bank erosion is found during the 

 site visit 



4. Temporary dikes should be constructed around the site if the site 

 will be inundated during operation (Figure 7). Refer to Appendix 

 C discussing river-training structures. 



40 V. SITE PREPARATION 



