THE REPUBLIC OF PANAMA. 823 



dam, the Commission recommended a plan of construction In- which a 

 masoni\v core wall 3<t feet thick at the bottom and 8 feet at the top 

 w^ould be built up from the rock beneath the bed of the river to the 

 top of the dam, thus efficiently preventing- all leakage of water through 

 the porous sand and gravel, of which large portions of the substrata 

 beneath the river bed are composed. 



As the top of this daui would have an elevation of lot) feet above 

 the sea, and as the highest water in Lake Bohio would l)e S feet lower 

 than that elevation, no water would ever overflow this dam, but the 

 surplus of flood waters of the ('hagres River would be discharged over 

 a masonrv spillway about 3 miles from the dam. The spillway weir 

 would be of masonry' and about 2,000 feet long. Its location is in a 

 notch or depression in the ridge between the headwaters of a small 

 tributarv of the Chagres called the Gigante and the valley of the C'ha- 

 gres River. The crest of this 2,000-foot-long overflow would be 8.5 

 feet above sea level. It is estimated that with the greatest flood pos- 

 sible in the Chagres River the depth of water on the overflow weir 

 would not be greater than T feet. During a great flood, therefore, 

 the river would discharge into this lake, and its waters would accumu- 

 late there until deep enough to run over the masonry spillway. With 

 the flood in a rising stage, the amount flowing over the spillway would 

 increase up to the greatest flood height, after which the rate of dis- 

 charge over the spillway would decrease. This regulation of the 

 Chagres floods, therefore, takes care of itself. It requires no atten- 

 tion. After discharging over the spill wa}", the flood waters would 

 flow through an artiflcial channel down into the Chagres River beyond 

 any of the canal works and where no damage would be done. 



About 10 miles up the Chagres from Obispo, at a point called Allia- 

 juela, there is an excellent site for a dam. It has been proposed to 

 build at this Alhajuela site a great masonry dam for the purpose of 

 impounding flood waters of the Chagres River to the extent of the 

 storage capacity behind the dam, and so reduce the flood eft'ects in 

 Lake Bohio. This storage reservoir would also act as a source of feed 

 water for the canal, should the traffic on it in the future become so 

 large as to require this additional supply. 



CULEBRA CUT. 



From C)l)ispo, oO miles from Colon, the canal line runs toward the 

 southeast through tlu> continental divide^ in a direct course toward 

 Panama, and for nearly 7 miles fi'oni Obispo a great cut has to be 

 made through the high ground forming that divide. For a distance of 

 about 5 miles from Obispo this is known as \ho Emperador Cut, 

 beyond which lies a mile and a half known as the Culebra Cut. The 

 greatest depth of this cut at Culebra is al)()ut 250 feet, and the amount 

 of material to be removed in this stretch of 7 miles of canal excava- 



SM ltt03 53 



