THE PANAMA CANAL 



201 



MAP OP GAT UN DAM, SPILLWAY, AND LOCKS (SEE PAGES 1 77 AND 1 79) 



a total of 1,312,200 cubic yards of con- 

 crete to lay for these locks, of which 

 7 per cent is already done. 



The Cocoli River, a tributary of the 

 Rio Grande, crosses the site of the Mira- 

 rlores locks from the west, and is such 

 a formidable stream in times of heavy 

 freshets that the protection of the locks 

 against its floods during construction and 

 after completion is necessary. A diver- 

 sion channel through the hills to the west 

 with a dam across the river valley would 

 accomplish the desired end ; but, as a 

 dam at the head of and to the west of 

 the locks is also necessary to impound 

 the water for the pool above, the solu- 

 tion finally adopted was the construction 

 of a dam extending from the head of the 

 locks to Cocoli Hill, with a direction 

 nearly parallel to the axis of the locks; 

 by this arrangement the Cocoli River will 

 discharge into the upper pool. 



The dam is of earth, 2,300 feet long, 

 top width 40 feet at reference 70, and 

 the side slopes approximately 12:1. The 



average head to which the dam will be 

 subjected is 30 feet, the maximum 40 

 feet. It is being constructed like the 

 Gatun dam, and is 43 per cent complete. 

 The east dam will be of concrete, ap- 

 proximately 500 feet long, provided with 

 regulating works similar to and of the 

 same dimensions as those at Gatun, the 

 crest in this instance being at elevation 

 39, with seven openings, permitting a dis- 

 charge of 7,500 cubic feet per second. 



For a distance of one and one-half 

 miles south from the Miraflores locks 

 rock is found in the channel, to be ex- 

 cavated at an average elevation of minus 

 30. The estimated quantity to be re- 

 moved is 1,503,260 cubic yards, which is 

 covered by 8,158,133 cubic yards of al- 

 luvial material, averaging 38 feet in 

 depth. It was not practicable to remove 

 the earth and rock by dredging and sub- 

 aqueous methods, as the requisite plant 

 could not have been assembled to com- 

 plete the work in the allotted time. 



An hydraulic excavating plant was, 



