The canal enters Lake Nicaragua, an inland sea, 40 miles wide, and over 90 miles long, which forms its summit level, and with the Chontales Mountains on the left, the route is continued to Fort San Carlos at the outlet of the lake into the Rio San Juan. Throughout this distance of 56½ miles, 28 feet of water can be carried to within 2400 feet of the mouth of the Lajas on the west shore of the lake, and within eight miles of Fort San Carlos on the south-eastern shore. In the former distance some dredging and rock excavation under water will be necessary, and in the latter, dredging in soft mud to an average depth of 3½ feet. From Fort San Carlos the route proceeds 64 miles down the San Juan river, which, with the exception of the 28 miles from the lake to Toro Rapids, has a depth varying from 28 feet to 130 feet, to the dam thrown across the river at Ochoa just below the mouth of the Rio San Carlos. Throughout this stretch of river, the only work to be done is dredging in mud and gravel, and some rock excavation under water to an average depth of four feet along a distance of 24 miles, below Fort San Carlos, and light excavation above water on some points in the lower river in order to flatten the bends. The dam just mentioned is located between two steep, rocky hills, at a point where the river is 1133 feet wide between the banks, with an average depth of 6·6 feet. Its length on the crest will be 1255 feet, its height 52 feet, the depth of foundations 20 feet below present water level, and it is to be constructed entirely of concrete, with timber-lined crest, front, and apron, and rip-rap protected back, forming a monolith wedged between rock abutments. This dam will back the water of the river the entire distance to Fort Carlos and into the lake, maintaining the water of the latter at the proposed level of 110 feet, and will convert the upper San Juan into an extension of the lake, with a fall of ¾ inch per mile.