C. Multiply the midpoint of each l-m depth interval (d) by the percentage 

 of area composed of that interval [(i.e., d x s = (0.5) (0.35); (1.5) 

 (0. 10) ,. .. , (d ) (s ) ]. 



0. Wean depth = sum of all products in C. [i.e., mean depth = r ds = 



(0.5)(0.55) + (I.5)(0.I0) + ... + (d )(S ]. 



n n 



The Table below contains example calculations of mean depth of the pit 

 shown in Figure D-l. The letters refer to the four steps listed above. 



Contour 

 i nter va I 

 (m) 



Surface area 



( ha or 

 other unit) 



(%) 



Wi dpoi nt 



of contour 



i nterva I 



(m) 



Product of 

 midpoint and 

 percentage area 



(m) 



0-1 

 1-2 

 2-3 

 3-4 

 4-5 



Total 



3.82 



100 



0. 17 

 0.26 

 0.35 

 0.98 

 0.36 



2.12= mean depth 



130 



