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water is concerned. But one of the defects of the system of narrow chutes and deflecting dams is already shown in the fact that the velocity of flow through some of them is so great as to make it difficult for the small steamboats plying on the Susquehanna to ascend them, while to open them to a greater extent would lower the pool above, and consequently increase the slope of the next rapid.
In case of future appropriation for this work, I would recommend that the subject be thoroughly considered in reference to the extent of river to be improved and the low-water depth to be secured.
Total appropriations to June 30, 1882.
July 1, 1881, amount available.
July 1, 1882, amount expended during fiscal year, exclusive of
outstanding liabilities July, 1, 1881
July 1, 1882, outstanding liabilities
July 1, 1882, amount available....
Amount appropriated by act passed August 2, 1882
Amount available for fiscal year ending June 30, 1883..
20, 255 38
Abstract of proposals (informal) received August 4, 1881, for dredging in Susquehanna
Abstract of contract entered into by Capt. William Ludlow, Corps of Engineers, Breret Lieutenant-Colonel, U. S. A,, during fiscal year ending June 30, 1882, for improvement of Susquehanna River, Pennsylvania.
Name and residence of contractor.
Dredging, price per cubic yard.
Date of contract.
Robt. C. Mitchell, Wilkes-Barre, Pa.. 90 cents through Gas-House Riff, 75 September 6, 1881. cents through other shoals.
CONSTRUCTION OF PIER IN DELAWARE BAY, NEAR LEWES, DELAWARE. The river and harbor act of March 3, 1881, appropriated $10,000 for continuing the construction of this work. The appended report by Mr. Stierle, assistant engineer, shows the application of the funds and the condition of the works at the end of the fiscal year 1881-'82, and submits an estimate of the additional amount necessary to complete it.
The deterioration of the timber superstructure, to which attention has been invited in repeated annual reports, has progressed rapidly during the past year, and has at this date assumed such proportions as in effect to compel the rebuilding of about three-fourths of the dock.
The last annual report estimated the cost of completion at $13,000. The progress of deterioration, as hitherto reported, and additional defects discovered in the course of rebuilding, necessitate increasing this estimate by nearly 50 per cent., to $19,000.
It is urgently recommended that such amount as may be essential to complete this work be appropriated, since the annual deterioration and the cost of maintenance represent a large percentage of the total required.
The tests of creosoted timber submerged in the harbor and exposed to the teredo, which were reported on pages 818 and 819 of the annual report for 1880, have been continued.
The couples, consisting each of a creosoted and an untreated block, were again submerged April 30, 1881, and allowed to remain until November 11, 1881, when they were taken up for the winter.
In May, 1881, when I had an opportunity to examine them, the nat ural blocks were thoroughly perforated, and had lost over 50 per cent. of their weight; the creosoted blocks were unchanged either in appearance or weight.
New blocks of natural timber were prepared and the couples again immersed in the water, near the end of the pier, where they still remain.
This work is in the collection district of Delaware, the nearest port of entry being Wilmington, Del.
Fort Delaware is the nearest fort, and the Breakwater light is the nearest light
July 1, 1881, amount available
July 1, 1882, amount expended during fiscal year, exclusive of out
standing liabilities July 1, 1881.
July 1, 1882, outstanding liabilities
July 1, 1882, amount available.
Amount appropriated by act passed August 2, 1882.
Amount available for fiscal year ending June 30, 1883..
6, 000 00
Amount (estimated) required for completion of existing project
"Amount that can be profitably expended in fiscal year ending June 30, 1884. 6,000 00
Abstract of contract entered into during fiscal year ending June 30, 1882, for construction of pier in Delaware Bay, near Lewes, Del.
REPORT OF MR. A. STIERLE, ASSISTANT ENGINEER.
PHILADELPHIA, PA., July 2, 1882. SIR: I have the honor to submit the following report upon the construction of the pier in Delaware Bay, near Lewes, Del., for the fiscal year ending June 30, 1882. The proposed work for the season was: To drive the remainder of the fender-piles, and connect them with the superstructure, and to replace decayed stringers, crossbeams, and floor-joists in the pier-head with new material.
By September 1, all the fender piles, except one, were in place, including the two isolated clusters of piles, of 9 piles each, at the outer corners of the pier. The last fender-pile was subsequently settled with the force-pump-the proximity of the freight house, built across the shoulder of the pier, preventing the use of the pile-driver.
The number of piles driven during the fiscal year was 107, making a total in place
During the months of September and October the fender-piles and the intervening wale and chock pieces were connected to the pier, the heads of the piles were cut down to a uniform height, the two clusters at the end of the pier were securely bolted and chained, and the machinery was dismantled.
The partial reconstruction of the superstructure of the pier-head was then proceeded with. The 4 by 9 inch floor-joists of the seventeen bays, between the fifty-fifth and seventy-second rows of piles, were taken up and carried ashore, to be replaced at the proper time by pieces of larger dimensions. The 12 by 12 inch stringers of this section of the pier becoming thus more exposed, close inspection revealed the fact that a greater number of them than had been anticipated were in a more or less advanced state of decay. The 9 by 9 inch cross-beams were in no better condition. Seventeen of the former and twelve of the latter were subsequently taken out and replaced by new pieces. The remainder of the decaying pieces cannot be removed until new lumber has been contracted for.
All the lumber that could be profitably used at the time having been put in place, the work of replacement was discontinued.
During the rest of the season heavy chock-pieces of yellow pine were fastened to the wale-pieces with long drive-bolts and between the heads of the fender-piles, to brace the piles laterally. This was accomplished by the 15th of February, when
work closed for the season.
It was expected that $13,000, the amount asked for in the last annual report for the completion of the pier, would be sufficient for that purpose. A recent examination and an estimate based thereon show, however, that this amount must be increased to $19,000. This increase of the estimate is solely due to the rapid deterioration of the lumber already laid in the pier and of that originally purchased and piled upon the beach. Attention has been repeatedly called to this matter, which has now assumed such proportions that a practical rebuilding of the superstructure, from the shore to the seventy-second row of piles, will be necessary.
Many of the pieces marked to be removed are but slightly affected by decay; it is certain, however, that they cannot last much longer, and their removal can more advantageously take place now while the general overhauling is progressing. Thus 70 per cent. of the stringers and 51 per cent. of the cross-beams will have to be removed in the pier-head. In the narrow part of the pier several stringers, 49 per cent, of the cross-beams, and all of the floor-joists must be removed and replaced.
Instead of using the old planks as decking for the pier-heads, new planking has been estimated for, as the former will be nearly worthless when the time arrives to lay them. The cost of removing so much finished work, in order to reach the pieces that are to be replaced, adds materially to the increase of the estimate.
The state of the pier at the end of the fiscal year is as follows: The substructure is finished. The superstructure of the narrow part of the pier is laid as originally planned, but must be rebuilt; that of the pier-head is in great part removed, awaiting reconstruction. All the fender-piles are in place and connected to the pier.
If sufficient appropriation be made, it is proposed during the coming season to continue the renovation of the older portions of the superstructure.
During the fiscal year ending June 30, 1884, it is proposed to finish the pier according to the original plan, if the necessary amount shall be appropriated as a whole. This work is in the collection district of Delaware, the nearest port of entry being Wilmington, Del.
Fort Delaware is the nearest fort, and the breakwater light is the nearest light-house. The original estimated cost of the pier was.
Which was reduced previous to 1878 by various revisions to..
Total amount appropriated to June 30, 1882
Total amount required July 1, 1882, for completion of pier according to the latest revised estimate..
360, 000 00 374,500 00 355,500 00
A. STIERLE, Assistant Engineer.
Col. WILLIAM LUDLOW,
Captain, Corps of Engineers, U. S. A.
ICE-HARBOR AT THE HEAD OF DELAWARE BAY.
The original preliminary report upon this harbor, given on pages 612 and 613 of the annual report of the Chief of Engineers for 1880, suggested that if it should be finally determined to build the harbor, detached from the shore in the bay between Liston's and Reedy Island, a structure consisting of lines of piers with a decking above high-water, resting upon iron piles, promised certain advantages over the solid detached stone piers, of which the other ice-harbors in the Delaware are built. These advantages may be summarized as follows:
The work once begun may proceed in almost any weather; the harbor is capable of indefinite extension as may be found desirable; the open character of the substructure, while the flow of ice is prevented, offers no obstruction to the free passage of the tidal currents, and the harbor will therefore require no dredging to maintain its depth. It affords continuous passage for sailers from end to end, and as many points of mooring as may be required.
The cost of an iron and timber structure of this character will not exceed that of the stone piers, and will probably be less.
The stone piers are necessarily somewhat widely separated and present comparatively few points for mooring; they interfere with the flow of water and create powerful eddies; they are reached only by boat, and access to them is frequently difficult or even impossible at the very time when, from the pressure of running ice, their shelter and support are most needed. The construction of the timber foundations to low-water and the laying of the stone work above is tide work, and therefore tedious and uncertain. Operations can only proceed during favorable weather, and the pier, until completed well above high-water, is a danger to shipping.
It might furthermore be stated that the lines of pier, having a continuous deck, afford opportunities for the placing of lights accessible one from the other, and of storing temporarily, wholly or in part, the cargo of a vessel, if necessary. Other conveniences, such as supplies of coal and provisions, suggest themselves..
The preliminary estimate of cost at prices then ruling was $250,000. The greater present cost of labor and material add to this.
The last annual report of the Chief of Engineers, for 1881, page 847, states as follows:
Consultation with those interested in the navigation of the Delaware discloses a predominating weight of opinion in favor of the vicinity of Liston's over Reedy Island as the proper location for the harbor. The construction will depend partly upon the location, but it may be said that subsequent investigation tends to confirm the conclusion suggested in Colonel Ludlow's report of January 24, 1880, namely, that the structure should be entirely detached from the shore, and be built of iron piles rather than stone piers.
The most advantageous position indicated by the chart seems to be in the vicinity of the intersection of the Finn's Point Ranges with the Port Penn Ranges.
These ranges make such an angle with each other as to compel vessels to haul nearly five points to eastward to pass from one course to the other. Sailing vessels in winter consequently get as far as Liston's, even with a northeast wind, and are frequently unable to get further, both by reason of the change of course and the masses of drifting ice encountered near the head of the bay.
Placing the ice-harbor outside and to the westward of the ranges avoids any possible interference with vessels pursuing their voyages, while it would be perfectly accessible to such as require its protection, whether on the outward or inward passage.
After further consultation with the maritime interests, studies have
been made during the past year in the direction above indicated of the most suitable plan and details of construction.
The simplest form of harbor protected against both flood and ebb tides would be one inclosed between two straight parallel lines of pier, which, with a length each of 1,008 feet and a distance apart of 600 feet, would define a harbor space of about 13.8 acres. Each line of pier would stand upon sixty-four trestles, about 16 feet apart, composed each of four iron or steel piles, with a timber deck, fender piles, and mooring facilities.
Red harbor lights at the four ends of the piers would mark the entrance.
Further consideration leads to the belief that it would be better to build the two lines of pier, so that each should consist of two lines, making with each other angles looking respectively up and down stream. This form, with the same width of opening at the east and west ends of the harbor, gives more harbor space or conversely allows of the partial closing of these openings without loss of area.
Moreover, the angle made by the lines of pier with the currents admits of the more ready flow of ice past the harbor on the exterior without admitting it. The addition to the cost of the works in consequence of this change is about 8 per cent.
In considering what should be the dimensions of parts and other details of the proposed structure, it became necessary to inquire as to the strains to which it might be subjected. Aside from the chance of collisions, against which it is impossible to fully protect a structure of any character, the most dangerous pressures to which the harbor would be exposed are those due to the ice moving in the bay at certain seasons under the influences of wind and tide. An attempt to compute the total possible thrust of a field would be useless, since practically no limits could be set to its area and weight.
Considering, however, the comparatively open character of the structure, it becomes evident that the greatest resistance to be required of the piles would only be that sufficient to crush the ice in motion against them; in other words, that the ultimate pressure would be limited by the crushing strength of the ice, and that if the piles were able to withstand this the structure would be reliably stable.
As a matter of fact, this degree of resistance, if computed from the pressure of a field of solid, clear ice, would never be demanded of the piers, for the reason that the ice, in floating about, is broken into blocks of various sizes, and, from the softening action of the air and sun and the saltness of the water in which it is immersed becomes rotted and disintegrated.
After diligent search for data as to the crushing strength of ice through all the engineering records available, it became evident that no information of practical value could be found. Numerous examples are recorded of the destructive effects of ice, but little or no attempt had apparently been made to analyze and classify the forces in action. The only discussions found are as follows:
In 1845 a Board of Engineers (report on file in office of Chief of Engineers, U. S. A.), considered the effect of an acre of ice, 12 to 15 inches thick, in motion, with a velocity of 3 feet per second, impinging against a breakwater, and estimated that every foot front of the field would exert a pressure of 27.11 tons against each foot front of the structure. After careful reading of the report, and of the comments thereon by Col. T. J. Cram (page 231, Report Chief of Engineers, 1868), I am