cost as smaller overlay stone. Since W50 is proportional to H^, 

 the 600-pound median weight stone overlay should be stable for waves 

 with a significant height up to 4.7 feet (1.43 meters). 



The Mobridge upgrade stone overlay specifications for repair of the 

 railroad embankment riprap were: 



Weight of Pet smaller 

 individual stones by weight 

 (lb) 



1,200 



100 



600 



35 to 50 



300 



6 to 10 



Overlay coverage was to be 50 tons per 1,000 square feet above water and 

 65 tons per 1,000 square feet below water (U.S. Army Engineer District, 

 Omaha, 1971) . 



The stone overlay on the railroad embankment was constructed in 1971 

 (Fig. A-6) , and to date has performed satisfactorily without the need for 

 additional repair work. 



