252 REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.


 The Gamboa dam site, less than half a mile away, makes it all but certain that a good rock foundation line will be found at about sea level, and just as good hill abutments exist on either side of the Chagres at Santa Cruz and El Hato as at Gamboa.

 SANTA CRUZ DAM AND BY-PASS.

 This dam, but 2,000 feet long, may be of the solid type or of the under-sluice Assuan design.
 The Santa Cruz by-pass would be solidly closed in the case of adopting the latter and not used. It could be employed with the main dam of th-, solid form and provided with an undersluice regulating barrage. The main dam will enjoy the advantages of the nt-head system.
 SANTA CRUZ LAKE.

 The lake by this barrier would extend to kilometer 46 along the canal and up the Rio Obispo to the westward and nearly to the junction of the Pequeni and Chagres above Alhajuela.
 DAM ABOVE ALHAJUELA.

 The Assuan under-sluice dam should be built at a suitable site below the junction so as to incorporate for flood regulation the empty basin principle.

 SSANTA CRUZ LOCK .

 Santa Cruz Hill affords a good location for one or several twin locks, without any material departure from the old alignment, and the change involves but little excavation on accouht of the lakes.
 One lock will raise the summit level to 138.5 feet and vastly reduce the quantities of the divide cut, as shown on the profile herewith.

 CHAGRES FLOW AND REGULATION.

 Precisely the same principles as are set forth in the main exposition of project A,,B, and B3' will govern the river, and its flow will likewise be sent to both oceans.
 ALTERNATIVES.

 Although the French condemned the San Pablo location for a high-head dam, nevertheless, by using the net-head system and a Morison type of design, it is feasible to plan still another dam, lock, and by-pass above San Pablo and by means of the Santa Cruz dam raise the summit level to 173.5 feet above the sea. This would lead them to a ten-lock canal and leave very little excavation in the Emperador-Culebra section summit, except on the upper terraces.
 If a multilock canal be admitted these dispositions create the best conditions for the service of navigation and the regulation of the river.

 FUTURE ELIMINATION OF LEVELS.

 The. French 130-foot high-level multiple-lock scheme proposed a dam at Gamboa and locks from the upper canal level into the lake above Gamboa for the disposition of spoil from Culebra. By a dam at Santa Cruz these locks are eliminated and material may be disposed in the lake or behind debris dams without their intervention. Such spoil locks are obviously superfluous.
 The high-level scheme has no monopoly of the academic possibility of eliminating levels without interruption of navigation, as any level in any plan may be eliminated if there be no regard for cost and time.
 But submerged-rock excavation, where blasting is requisite, costs, according to all past experience, far more than the excavation of such material in the dry or where it may be shattered in situ without the use of under-water drilling, loading, and blasting.
 The unit prices universally current for submerged-rock excavation are from five to ten times those for handling rock where it can be readily gotten at.I


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