has a line of foundation-mattresses along 300 feet of its east side, and on its west side above dam No. 3. Mattresses are inclined against the west side of this upper part of the T-head. The two T-heads are 800 feet apart, and form an entrance to the South Pass. In the latter part of September dredging was begun to make a cut through the shoal water between the two T-heads. The cut is now about 2,000 feet long, from 30 to 90 feet in width, and 183 feet of water can be carried through it from the main river into the South Pass. An apron of mattresses has been put across the Southwest Pass to prevent scour. It runs from the west shore to a point near the upper end of the west T-head. A line of piles was driven and mattresses were then sunk against its upper side. Nearly all of these mattresses are 70 feet long, and are sunk side by side, so as to make the apron 70 feet wide. After the mattresses were sunk the piles in the middle of the pass were pulled up to give a passage-way to vessels. Where the water was about 30 feet deep it was found necessary to use piles 60 or 70 feet long to make them stand. In wing-dam No. 1 the inclined mattresses, like those in the spur-dams at the mouth of the pass, have settled down, letting the water pass through the piles. Accordingly another dam (No. 5) has been built from the lower part of the island across this east entrance to South Pass. In its construction a line of piles 10 feet apart was first driven across the entrauce, a waling-piece put on them, and alternate piles were braced from a second row 15 feet farther down stream. Inch boards in two layers, breaking joints, were then inclined against the waling-piece of the upper row. The statement in my last report as to the minimum number of men employed was in error, from omitting a stone-gang and some others, amounting to 30 or 40 men. Three sheets of tracings are forwarded herewith, giving— 1. Soundings at mouth of South Pass; 2. Sections of mattress-work there; and— 3. A plan of works at head of pass. To avoid delay, the soundings of sheet No. 1 have not been carried far into the Gulf of Mexico. RECAPITULATION. In recapitulation, it may be said that between August 17 and November 18, 1876, the work at the mouth of the South Pass has been small in amount, consisting mainly in bringing the sea-end of the east jetty up to average flood-tide, in adding stone to both jetties, and constructing eight new spur-dams. On the whole, there has been little change in the depth of water through the jetties at the mouth of the pass. On November 14, 20.3 feet could be taken through. At the head of the pass wing-dam No. 2 has been completed and a T-head put on it. Another T has been built out from near the lighthouse, with a head parallel to that of wing-dam No. 2 and 800 feet from it, these two T-heads forming an entrance to South Pass. Between them a cut of about 2,000 feet long, from 30 to 90 in width, has been dredged, through which 183 feet of water can be carried from the river to the pass. A mattress apron 70 feet wide has been put across the bottom of Southwest Pass. An additional dam has been built across the east entrance to the South Pass. The wing-dams Nos. 1, 2, and 3 at the head of the passes, well as the spur-dams between the jetties at the mouth of the pass, at present temporary structures, although they might be utilized needed in making more permanent ones. The force employed at the South Pass by James Andrews & Co. has en about seventy men besides the crews of the steamers. This does t include about thirty men employed by subcontractors in making ttresses, nor other men employed elsewhere in quarrying stone, &c. Very respectfully, your obedient servant, Hon. J. D. CAMERON, C. B. COMSTOCK, Secretary of War, Washington, D. C. |