Groundwater Table. It is important to establish the depth to the ground- 

 water table together with spatial and temporal variations in this parameter. 

 Groundwater conditions may vary widely throughout the year in response 

 to changing river levels, thus, several measurements are preferable. The 

 date of measurements should be carefully recorded. 



Extent of Permafrost. Although permafrost occurrence in the vicinity of 

 rivers and streams can be highly erratic, it should be anticipated in arctic 

 and subarctic regions. The presence or absence of permafrost can be an 

 important factor in developing a gravel removal site. 



Field Techn i ques 



Both borings and test pits can be used for geotechnical exploration. 

 Test pits are generally preferred in granular soils because of the diffi- 

 culties of drilling and sampling in sma I I -d i ameter borings. However, borings 

 can provide a good indication of overburden thickness, water table, perma- 

 frost conditions, and presence and extent of unacceptable (e.g., silty) 

 materials. These borings or test pits should extend to the depth of the 

 anticipated gravel removal. The number of pits or borings would depend upon 

 the size and variability of the site. 



Laboratory Testing 



The required laboratory testing effort varies. Sieve analyses are 

 needed, as a minimum, to classify the material and establish its suitability 

 for its intended use. For these tests, rather large (50 to 100 kg) bulk 

 samples are desirable. Other tests that may be needed include hydrometer 

 tests (if frost-susceptibility is a concern) and compaction tests if the 

 gravel will be used to support structures. 



FINAL SITE SELECTION 



The final site selection is based upon the criteria analysis of the 

 alternative sites. This analysis compares the characteristics of the ma- 



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