Page images
PDF
EPUB

The (stone) dock proper at Esquimalt, B.C., cost about $1,500 per lineal foot, which included land, coffer-dam, unwatering, caisson, valves, pumping machinery, buildings, etc., and when called upon to estimate the cost of extending that dock a length of 100 feet, the writer placed it at $1,000 per foot, that being the actual cost of constructing one foot of the body of that dock.

It is extremely questionable whether a wooden dock at a cost of $975 per foot can claim any character for cheapness when compared with the dock at Esquimalt, where labor and materials are higher than on the Atlantic coast; and certainly on the score of permanency, maintenance and repairs, the stone structure has the pre-eminence, and thus the claim for cheapness falls to the ground.

On this point it is well to quote from the report by Mr. Keating, referred to herein. "It is claimed for wooden docks that their comparative cheapness should outweigh all other considerations. The American patentee claims that the original cost is less than one-tenth that required for a permanent stone dock,' and if this, or even a much higher value had been fixed as their true worth, there would be no need for further argument in their favor. An examination into the facts, however, shows that in some cases at least, their actual cost has not fallen short of a fair price for a similar stone structure in a favourable locality. The two wooden docks at Brooklyn are reported as having cost as they stand to-day $1,283,356 (exclusive of interest), or say $640,000 each, although they are both operated by the same set of pumps; and in the case of St Johns, if the value of the land and the remitted duties be added, it will be found that the actual cost of the dock at that port has been about the same sum, A carefully designed permanent stone dock with all its appendages, under similar favorable circumstances, and suitable building materials within a reasonable distance, would not in my judgment prove any more expensive."

Thursday 9th May,

P. A. PETERSON, Vice-President, in the Chair.

Paper No. 31.

THE ESQUIMALT GRAVING DOCK WORKS, BRITISH COLUMBIA,

By W. BENNETT, M.CAN. Soc.C.E.

These works, which were fully illustrated in "Engineering" of the 20th and 27th of July, 1888, were originally commenced by the Government of British Columbia, and have been completed at the cost of the Dominion of Canada, the Imperial Government contributing £50,000 thereto, in consideration of which, any of H.M. ships have priority of entry and free dockage for 15 years, on payment of working expenses only. The works were designed by Mr. Kinipple, the senior member of the late firm of Kinipple & Morris, Engineers in Chief for the whole of the works.

The outer or Cofferdam works (Figs 1 and 2, p. 221), were commenced in September, 1876, and the inner or Dock works some four years later. The Earl of Dufferin, then Governor General of Canada, was present when the first pile of the dam was driven. The Dock was opened on 20th July, 1887, H.M.S. "Cormorant" being the first to enter, and followed, when her repairs were completed, by H.M.S. "Caroline."

The progress of the outer works was to a certain extent hindered by the fact that at Esquimalt the range of tide, which was supposed to be about 10 feet, is very uncertain, the tide remaining frequently at almost H.W. level for days together, which thus prevented the wales and struts of the dam being placed in their respective positions. The original drawings had therefore to be somewhat modified in order to prevent further delays in the completion of this portion of the work.

In January, 1876, the contract for the Cofferdam was given to Messrs. Reed Brothers, of Tokenhouse Yard, London, by the British Columbian Government, for the sum of £12,311. Owing, however, to the non-fulfilment of their contract in the specified and extended time, the Government, in June, 1879, after the contractors had ceased work altogether, took possession of the Cofferdam works, and completed

them in the following October, under the superintendence of their Resi

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small]

When the water was pumped out from the area on which the Graving Dock was to be constructed, the dam was found to be perfectly tight in every respect, although for fully one-third of its total length, of upwards. of 500 feet, at the shore ends, the sheeting piles had to be planted on a very uneven foundation of rock, overlaid with sand, shells, and boulders, all of which, of course, had to be removed. Some of the holes for the rock pile shoes were drilled in 25 feet of water. The dam did not show the slightest strain when the full pressure, due to a head of nearly 30 feet, was brought against it, and remained intact until it was removed on the completion of the Dock in 1887. Although the dam was not removed for 7 years after its completion, no pumping whatever was required during that time beyond that which was due to percolation through the strata, or to rainfall.

The three sluices through the Cofferdam were not constructed as shown on Figs. 5, 7, and 8, so much on account of the tidal difficulties already referred to as for the avoidance of leakage, and in lieu thereof one sluice, equal in capacity to the three proposed, was built in the channel way at the back of Thetis Island (Fig. 1), and by its means the Dock was flooded at the testing of the caisson against the meeting faces.

The greater portion of the Portland cement used in the construction of the Dock was supplied by Messrs. Gibbs & Co., of Gray's Essex, and the remainder by Messrs. Robins & Co., and other well known English makers.

In June, 1875, tenders were ordered to be obtained for the Dock pumping machinery, and Messrs. James Watt & Co., of Soho, Birmingham, secured the work at the contract price of £6300. This contract included the boilers, engines, caisson hauling gear, sluices, pumps, &c. The boilers (3 in number, one spare) are of the cylindrical and multitubular type, each 15 feet long, and 63 feet in diameter, having 2 flues 4 feet 6 inches long, 2 feet 3 inches in diameter, a large combustion chamber, and 120 tubes 2 inches in diameter, 5 feet in length. (Fig. 27). The boilers were tested to 120 lbs. per square inch, the working pressure being estimated at 60 lbs. The main pumping engines are capable of raising 907,000 cubic feet of water in 6 hours, with an extreme lift of 35 feet, and a mean lift of 17 feet 6 inches. These engines are of the low pressure condensing horizontal description. The cylinders, 2 in number, are 27 inches in diameter, with a stroke of 4 feet. The main pumps are 4 feet in diameter, and 5 feet stroke, the working barrels (Fig. 24) of which are lined with brass; the pump buckets are also of brass, with india-rubber valves, and designed to discharge from 15,000

to 18,000 gallons per minute. The auxiliary engine is of the vertical direct acting description, having a cylinder 14 inches diameter, and a 12 inch stroke. This engine is used both for working the auxiliary pumps and the caisson hauling gear. The auxiliary or drainage pumps, 2 in number, 10 inches in diameter, with a 2 feet stroke, are jointly capable of raising 600 to 800 gallons per minute, 50 feet high, (Fig. 26).

The whole of this machinery was delivered at Esquimalt in 1876, and stored, with the exception of the auxiliary pump, which was used to pump out the area behind the Cofferdam, and also to keep down the surface drainage during the whole period that the works were under construction; thus the necessity of obtaining special pumps for this purpose was obviated.

On the 5th of September, 1879, tenders were advertised for the main works, and Messrs. F. B. McNamee & Co., Montreal, were the successful contractors.

The works, however, were not commenced before the 13th of September, 1880; but progress was slow, and in April, 1882, the contractors stopped work, and consequently, in June, 1882, possession of the works was taken by the Government of British Columbia. The works were carried on for the following 12 months by day labor, and again under the direction of their Resident Engineer. On the 24th of August, 1883, the works were handed over by the Government of British Columbia to the Dominion Government, under the terms of the Settlement Bill, one of the terms of which Act provided for the repayment of all sums expended on Dock account by the Federal to the Provincial Government.

The Dominion Government thereupon advertised for tenders for completion of the works, but it was not until November, 1884, that the tender of the well-known firm of Messrs. Larkin, Connolly & Co., of Quebec, was accepted, and they afterwards prosecuted the works to completion with great energy and ability.

The Dock is 450 feet in length (Fig. 9) from the inner face of the caisson, when in its ordinary berth, to the base of the circular head, and has a width at the entrance of 65 feet. (Fig. 10.)

The walls of the Dock are parallel for the entire length, and the width across the floor is 41 feet. The top inside width of the Dock at coping level is 90 feet, and the depth on sill at ordinary H.W. is 263 feet. Occasionally, however, the tide rises from 2 to 3 feet higher.

The excavation for the Dock, which was commenced in 1880, was mostly in sand and shells for a depth of about 3 feet over the entire area of Thetis-Cove. Below this level very stiff brown and blue clay

« PreviousContinue »