This report has been reviewed by the 

 Bureau of Land Management and approved 

 for publication. The opinions expressed 

 in this report are those of the authors 

 and not necessarily those of the Bureau 

 of Land Management, U. S. Department of 

 the Interior. The use of trade names or 

 identification of specific products 

 or equipment by manufacturer does not 

 constitute endorsement or recommendation 

 for use. 



