the operation of dredging is greatly retarded by the presence of innumerable snags, one of which (recently excavated) measured six feet in diameter by forty feet in length. The time occupied in removing one of these snags would be sufficient to excavate upwards of one thousand cubic yards of sand; it also causes an additional expense by incurring numerous breaks in the machinery of the dredger, which, were it not for the snags, would probably not occur. From the fact that these snags are at the lower end of Swan Island Bar, and embedded at this depth, and also from the fact that some of them have copper attached, (probably from some vessel having scraped over them years ago,) I am inclined to think that the lodging of these snags at this locality was the cause of the formation of Swan Island Bar. It may be that as we progress with the excavation further up the river these snags will disappear; it is probable that such will be the case, but should it be otherwise, it will be nearly impossible to estimate, with any degree of correctness, what it will cost to excavate Swan Island Bar to eighteen feet of water. It is certain, however, that unless these snags soon disappear the work cannot be completed during this fiscal year, and an additional appropriation will be required. At this date, there is available to prosecute the work $16,788 88, which will be sufficient to work for about five months longer, and allow us to attain a depth of seventeen feet of water over the bar, providing that portion of the bar between the references fifteen feet and seventeen feet be ordinary material, as sand and clay, but should this mass contain many snags, then the amount available will be insufficient to complete the work to that depth. An annual appropriation is or will be required to keep the channel at the mouth of the Willamette River open. To fopen a channel, giving seventeen feet of water at the mouth, has cost the United States, in round numbers, $13,000. It is probable that this channel will partially refill during the summer freshet, but in all probability two months dredging will again open it. This will cost about $6,000. This amount annually appropriated would probably suffice to keep the channel at the mouth of the river open. As it is proposed to dredge Swan Island Bar to eighteen feet of water, I think it would be advisable to request that an additional appropriation of $25,000 be asked for; this, together with one of $6,000 for the mouth of the river, would enable us to work until June 30, 1871, and would probably complete a channel of eighteen feet of water in the Willamette River from Portland, Oregon, to its mouth. I have the honor to be, very respectfully, your obedient servant, Bvt. Lieut. Col. R. S. WILLIAMSON, U. S. A., Lieut. of Engineers. Major of Engineers. ▼ 2. SAN FRANCISCO, February 13, 1869. GENERAL: In compliance with orders from headquarters Corps of Engineers, dated at Washington, September 5, 1868, I proceeded to San Pedro or Wilmington, California, and made an examination of the harbor at that locality. Having been kindly furnished from the Coast Survey office at this place with a tracing of the Coast Survey chart, scale 10006, of the hydrography of the harbor and its approaches, a new survey was not necessary, as the chart, together with the information I obtained from personal examination of the harbor, has been sufficient to enable me to report fully on the wants of commerce at the locality, and prepare a project for such improvements as may be called for. From an examination of the inclosed chart, it will be seen that the harbor or bay is formed by Rattlesnake Island and a sand bank to the south of it, from which they are separated from the main land by a narrow but deep bay or channel, the depth of water in which is, for two miles from its entrance, ten feet at low water in the shoalest place, and in many parts of it much deeper. Between this deep water and Wilmington, which is three miles from the entrance to the harbor, the water is more shallow, the chart showing in some places a depth of but three or four feet. Át the entrance is a shoal or bar, the consequence of which is that steamships or other large vessels are compelled to lay off Deadman's Island, nearly a mile from the shore, and some four miles from Wilmington, and all passengers and freight in coming to this port must be transferred to lighters in order to pass over the bar. As soon as this is passed the water deepens to from ten to eighteen feet, and so continues to within a mile of Wilmington. A railroad is in process of construction from the city of Los Angelos to Wilmington, and it is contemplated that it shall terminate on Rattlesnake Island, at the point above referred to as being about a mile below Wilmington. The object of the proposed improvement is to so remove the shoal at the entrance that sea-going vessels can reach contemplated wharfs at the railroad depot. An examination of the harbor shows that Rattleshake Island, though of low elevation, is not subject to overflow. At its southern extremity are a couple of sloughs with water from seven to twelve feet in depth, and then comes a broad flat, bare at low water, in length about three thousand feet to the bar at the entrance. The plan proposed for the improvement is to close these two sloughs, and to build up, from the southern end of Rattlesnake Island to the point off the bar, an artificial bank, so as to partially or totally confine the water of the bay (much of which now runs through the sloughs, and as the tide rises overflows the flat) to the channel between the islands and the main land. It is supposed that when this is done the increased velocity given to the receding tide will partially remove the bar or shoal at the entrance. It is possible, though scarcely to be expected, that the deepening will be sufficient to admit into the bay vessels drawing eight or ten feet of water at low tide. If, however, the effect should prove not sufficient to give the required depth of water, then it will be necessary to continue the artificial bank as far as Deadman's Island, to the south of which the water is much deeper. The bank is to commence at A, (see line colored red on the chart,) and continue eighteen hundred feet to D, where the sand bank comes again above high water, forming an island about three hundred feet in width. From the southern end of this island, at E, the bank should be constructed in a right line, or perhaps better, in a curve parallel, to the channel, two thousand feet to the point B, opposite the bar. This will form the first section of the proposed work. The second section of the bank, should its construction be found necessary after the effect of the first section is proved insufficient, will terminate at Deadman's Island, as shown on the chart at C. A profile of the two sections is also inclosed. These being the general features of the plan for this improvement, it only remains to consider its details and the materials to be used. I presume it will be admitted without question, that the best material for this purpose to secure a permanent work is granite in large masses. It appears to me also that, as the success of the plan depends upon the scouring effect of the confined water of the bay, and as it is well known that such effect is produced almost entirely from half to low-water of the receding tide, and as the rise and fall of the tide does not exceed eight feet, I consider it will be sufficient to build the bank but six feet high above low water. Moreover, as the force of the waves will have been greatly diminished before the waves reach the shoal water on the line of the proposed improvement, I consider that it will be sufficient to construct the bank with a width at top of fourteen feet, and with a slope of one to one on both sides in the first section, where, for the most part, it is naturally bare at low water, while in the second section it should have a seaward slope of one vertical to four horizontal. There is no granite or other first-class material for the proposed construction, in the vicinity of San Pedro or Wilmington, and, therefore, if such material is to be used it must be brought there in vessels. Granite of good quality and of easy access to the coast is found at a quarry some six miles south of Monterey, and I find that it can be delivered at a wharf, ready for shipment, for $2 per ton in coin. I also find that it will cost $4 50 per ton in coin to transport it from the wharf to the immediate vicinity of the place where it is to be deposited, and allowing $1 per ton more for placing the blocks in position, I have the following as an estimate of the cost of the proposed improvement in coin. ESTIMATED COST OF FIRST SECTION FROM A TO B. Cost of 36,673.5 tons of granite, at $2 per ton $73,347 00 Transportation from quarry to San Pedro, at $4 50 per ton 165,020 75 Placing same in position, at $1 per ton... Contingencies, ten per cent.... 36, 673 50 Total cost of first section in coin.... 275, 051 25 27,505 12 302, 556 37 ESTIMATED COST OF SECOND SECTION FROM в TO C. Cost of 63,958 tons of granite, at $2 per ton. Contingencies, ten per cent Total cost of second section.. ... ... Estimated total cost of both sections in coin... $125, 916 00 283, 311 00 62, 958 00 472, 185 00 47, 218 50 519,403 50 891, 959 50 I consider that, by the use of large rough blocks of granite, the improvement can be made in a more durable manner, and with more certainty of success, than in any other way. It has been suggested, however, by others that the same end may be secured with less cost by a bank of materials of sufficient durability to last two or three years, because, when the bank is once made, it will be strengthened and increased in size by the natural accumulation of materials brought against its seaward face by the waves. Mr. Ed. A. Flint, a civil engineer, now in charge of the Wilmington and Los Angelos railroad, has suggested such a plan, which I consider worthy of careful consideration. I have requested him to give me a written description of his project, which he has done, and I respectfully submit it in an appendix to this report, marked A. His estimate is $117,000 less than mine for the two sections. The cost of the first section in currency will be about $400,000 if granite is used, or $360,000 if Mr. Flint's plan is adopted. I respectfully suggest that should this construction be decided upon, a sufficient amount be first appropriated to complete the first section. Even should the result not fully secure the depth of water necessary to admit large sea-going vessels, it would certainly deepen the water to some extent, and so far prove a permanent benefit. I inclose, in Appendix B, a letter from Mr. P. Banning, of Wilmington, giving statistical information of the resources of the country in its vicinity. I have the honor to be, very respectfully, your obedient servant, Bvt. Lieut. Col. U. S. A., Major of Engineers. Gen. A. A. HUMPHREYS, WILMINGTON, LOS ANGELES COUNTY, CAL., January 2, 1869. COLONEL: I have the honor to inform you, in reply to your esteemed favor of December 23, that there is at least one large steamer arrives at this port every week, and there are about ten sailing vessels irregularly employed in bringing merchandise and lumber to and from this place. For the past year the freight has amounted to a little over fifty thousand tons, or about four thousand tons per month. The number of passengers is about eight hundred per month. The railroad from Wilmington to Los Angeles will be finished by July next, and it is proposed to continue it from there to San Bernardino. The land in this and San Bernardino County is, as you are aware, the richest in the United States, and annually produces tens of thousands of tons of corn, barley, oats, and wheat. Over one million gallons of wine were manufactured last year, and double this amount will very soon be made annually. The cost of lighterage from Wilmington to the anchorage (distance about six miles) is so great that farmers are now unable to ship their corn to a market. Nearly all the troops and a portion of the supplies for Arizona are landed here. In conclusion, permit me to assure you that there never can be any permanent prosperity in this portion of our State until we have a good harbor. Very respectfully, your obedient servant, Col. R. S. WILLIAMSON, PHINEAS BANNING. United States Engineer Corps, San Francisco, California. WILMINGTON, February 3, 1869. DEAR SIR: I have to thank you for your favor of January 16, and for the opportunity it affords me for further search for material to construct the breakwater at this port. I was unable when I last addressed you to enter into details, but am in hopes to partially supply the deficiency in this letter. Starting at Rattlesnake Island and following the line of location sketched by General Alexander, we find the first five hundred feet bare at low tide, followed by two channels, separated by a ridge of sand about one hundred and fifty feet in length, also bare at low tide, which have a depth of water at low tide from seven and one-fourth to eleven and one-fourth feet. After leaving these channels we again come to a strip of land about three thousand feet in length of firmly packed sand, evidently formed by the sea wash from the east, and through its whole length laid bare at low water. From this point to Deadman's Island we have another stretch of three thousand feet, which has a depth of water varying from two to four feet at low water. These distances and depths of water are taken from the Coast Survey map of 1859. Since that time the sea appears to have altered very considerably the profile of that line just described, particularly along that portion represented on the Coast Survey map as being exposed at low water. At present writing a part of it is exposed even at high tide, showing that in ten years a very considerable quantity of sand and gravel has been washed in by the sea, and leading to the conclusion that if nature could be assisted by some description of breakwater the deposit would increase much faster on the east side than it has done, and in a few years not only cover the breakwater itself, but also form new land to such an extent that the decay of the breakwater would be no detriment to the value of the harbor. Along a portion of the line above described, we have seen that the sea has deposited from six to eight feet of material in ten years, and assuming that, with the assistance of a breakwater, at least an equal amount of deposit could be expected in the next ten years, it would then only be necessary to raise a structure of such material as would exist for that length of time. I have been unable as yet to find any quarry where suitable stone can be found. A sufficient quantity of boulders, washed round by the sea, are easily obtained and could be used in timber cribs. Owing to their shape it would be impossible to use them without confining them in some way. They are in a very convenient position for the work, being located on the shore beyond the present San Pedro landing at the south, and the size of the stone ranges from five to fifty pounds. It would be necessary, however, in order to move them to advantage, to build about two miles of railroad, and a wharf, about eight hundred feet in length, out to such depth of water as would enable a tug-boat with lighters to come alongside. Probably the best timber for cribs would be the California red wood, impregnated with coal tar, by placing the wood in an air-tight cylinder, exhausting the air and allowing the hot liquid to flow in and fill the vacuum. This would secure at least ten years' life for the wood, from all destructive agencies except the Teredo navalis, and this little creature would have but little chance to attack it after the first year, as it would probably be covered above the level of low water by that time. In the following sketch for a crib breakwater, I have allowed very liberally-for settling of cribs into the sand, probably much more than would actually take place, but it has been my endeavor to err on the safe side. At the two channels, south of Rattlesnake Island, I have |
