THE HARBOR BOARD.

Evening Star, Issue 7473, 17 March 1888, Page 2

THE HARBOR BOARD.

The following is the Engineer's report for the past year : Victoria Channel.—The dredging done in the Victoria channel has been considerably leas than in any previous year since the beginning of the work. The parts operated upon were 0£ mile to 1J miles; from 2| to to 3£ miles; and at 5£ miles. On the extent between the swinging basin opposite the Victoria wharf to 0| mile no maintenance dredging has been necessary since it was cut down in 1885. On three different occasions in 1887 the Vulcan has been at work upon the section between OJ mile and 1£ miles. The total quantity removed was 33,072 cubic yards, so that the amount of time occupied in shifting anchors was large in proportion to what was dealt with. The length between 2\ and 3)j miles is that portion of the channel where the excavation was the deepest in the original cut, and where the mobile character of the sand renders it impossible to maintain the side slopes until they have been reduced to a very flat condition. The other part at 5J miles was a cut through a projecting bank near Kilgour Point, which had not previously been touched, and which, in its natural condition, involved a sharp turn by vessels passing. The following table will Bhow in a general manner the comparative conditions of the channel in January of the years 1887 and 1888. It is to be observed now, as previously, that these depths are along the line of deepest water, "which in Bome cases inay i be different from the line which would be taken by vessels:— I Dunns in Victoria Channkli, January, 1887 and 1883, as in the Line of Deepest Water. All at Low Water of Spring Tide. Hlbo Cft (iiu. Ol K". CO 10 H» W S 2 . : . : g: g <f> o o o o o 3. < o. a *. w is gt> B B. q a m «• > r, <* O C ?«:::: * 3 o a a a « s. « 2 a o 1.1... 2. 5' • M 5 S O S Ol rf 1887. M jft-__*t; * _*_: —. _ m & 3 g £ r . IBBB- " 1 I " M * I 3 Increase. | ». «hj I I I *. P Deoreose. ro W H-* ro >-» M Iflft7 2? a O 00 IK t(5 00 f» «>OI. pj tO tO M N> >-■ M "i I 1000 3 CI O <0 *■ *£ M 1» j 1 00 3' H w. I **> «- I | 2 Inorease. y ; | I 1 I I I w 5 Docreaae. J M m M ►-* •"* *-• M CD (Om--ISDOO- ; IW 10Q7 en b " B b - ► oo P P° r> P -' 5» 2 1883. a to to ~* o> <*> M F* m 0 | to <* *> i| I I P Inorease. Ej hj | | I I "" 3 J» Decrease. j a v, o a - : 0 op o ««o <$ O 2 Q. _► 2 c g"c » t 3 ° » OS.O g 2- 'B. "** a - a- w 5 3 J - b 3 5 ~ ! -> o «• S ■ S «' 01 rfc» T. - 0 —?" : The minimum of 15J in tlie first line occurs at the corner of the steamers'basin and the main channel, and does not interfere with the approach of a deep draught vessel to the Victoria wharf. T"he Turakina, drawing 19ft Sin, was brought up to Dunedin on the 4th January of this year without trouble. Steamers' Basin. Dredging _ in the steamers' basin has been the principal part of the Vulcan's work in 1887. That area, with the exception of a part of the bank at the south-eastern corner, has been excavated to depths between 15ft and 20ft of low water according to locality. Seventeen feet is the ruling depth in the main area of the basin, 15ft at parts of the old wharves where deeper dredging was not safe, 17ft at places where this could be done, and 20ft at the Tongue wharf and part of Jetty street whar which was re-piled in front. The material excavated during 1887 was 164,232 cubic yards, composed in great part of stiff clay. Swinging Ijerth at Victoria Wharf.— Dredging has been done in extending the basin in front of the Victoria Wharf, as it was found that the area of deep water was too limited for the convenient handling of the larger vessels now frequenting this port. A dolphin was also constructed to facilitate the departure of vessels during a N.E. wind and flood tide. The quantity of material removed in the execution of this improvement was 19,092 cubic yards, mostly by the Vulcan, but to the extent of 660 cubic yards by the side dredge. This latter quantity was disposed of to Mr J. M'Donald for use in the manufacture of cement. Miscellaneous Dredging. Dredging has been done by the side dredge at the approach to the Stuart street wharf, and at site of floating dock, to a total quantity of 12,252 cubis yards. Reclamation of Board's Endowments.— With the exception of the small portion of the dredged material disposed of to Mr J. M'Donald already mentioned, the material raised by the Vulcan and side dredge has been deposited on the Board's endowments in Dunedin. The stuff has been placed upon the Rattray-Stuart street block, the block north of Stuart street, and the block south of Jetty street. The system of Bmall contracts for the distribution of the material has been continued where necessary; but by the removal of derrick No. 4, and by the placing of two derrick cranes upon punts, the material has been placed, in great part, upon areas where it could spread without further handling after it had left the boxes of the cranes. Rubble Walling.—The half-tide walls in the channel have oeen maintained, and also a considerable portion of wall has been constructed on the southern boundary of the large dock to enable the reclamation of the Stuart street area to be completed. The walls south of Jetty street and at Blanket Bay have also been repaired. The stone was got partly from old walls, which became unnecessary by the extension of the reclamation at other ports, but principally from Goat Island, where the quarrying served the double purpose of improving the view along the channel and of supplying stone for necessary works. Wharves and Sheds.—A wharf known as the tongue wharf, extending into the steamers basin, has been constructed by Messrs M'Kenzie and Sons. The length is 372 ft, and the width 90ft, or along the oblique end 127 ft. This affords berthage for vessels upon two sides and at the end. Provision has been made for three lines of rails and traversers. Two sheds are now being erected on this wharf. A shed for wool dumping and general purposes was built at the extreme end of the Victoria wharf, with a length of 100 ft' and width of 50ft. Two wool presses (by ; Messrs Morgan and Cable) and four pumps ' (by Messrs Anderson and Morrison, from the j designs of this department) have been' erected, with the necessary engine and ] boiler power, The whole plant is now j working very satisfactorily. I Dredging at Port Chalmers.—Dredging I was done adjoining the Port Chalmers ] wharves and in their approaches in the j months of July, August, September, and , October by the hopper dredge, which lifted 33,833 cubic yards from that locality and discharged it at sea. The depth aimed at was 22ft of low water, but parts were dug j somewhat deeper. Dredging on Bar.—The hopper dredge was at work on the bar on twenty-eight occasions in 1887, whereof the locality of the eleven earlier ones was to the westward of the old line of leading lights; fifteen were to the eastward, close in urjon Taiaroa Head, for the purpose of removing a narrow spit which projected from the headland, but this was not accomplished ; and two were merely for the purpose of removing the moorings after it waß resolved to discontinue operations. The total Band removed amounted to 14,426 cubic yards, making the whole quantity since Ma/, 1882,108,994 cubic yards on 186 occasions, exclusive of the times the dredge wis recovering her moorings as already referred to. North Head Works.—At the end of 1886

the staging for the training wall was out a distauce of 3,022 ft, and during 1887 work was continued until, by the 2nd November, it had been extended to 4,088 ft, and there it was stopped. The first pile of this was driven on 22nd September, 18S4, so that the progress has been at the average rato of 1104 lineal feet per month. Its total cost up to that point was L 30.982 19s 3d, but a slight further expenditure has been incurred this year for a permanent light at the outer extremity, and for a handrail the full length from the beach. The cost is quite L 22.000, or L 23,000 less than estimate, as I have already pointed out in reports of Bth November and 7th December of last year. Stonework of Training Wall.—The stonework of the training wall has been carried out as expeditiously as possible, so as to follow closely upon the piling. Notwithstanding every effort, there was always a considerable Bcour about the extreme piles, lowering the bottom to 32ft and 33ft below low water. This necossitatcd the scarfing of a number of piles up to a length of 70ft until others specially ordered from Australia had arrived. The total quantity of stone quarried and deposited during the year was 102,740 cubic yards, bringing the whole quantity placed in the wall Bince January, 1885, up to 220,398 cubic yards. The spoil dealt with last year was 24,457 cubic yards, so that in all 127,197 yards of material were handled, at a cost of L 10.396 17s 4d. If calculated upon the stone placed in the wall, the rate is 2s o|d per cubic yard, but if upon both stone and spoil, then Is 7|d per yard. After May the southern quarry , had to be abandoned on account of the quality of the stone being inferior, and thereafter the north quarry alone was worked. The stone in it is still good and abundant. Alterations in the the Neighborhood «f Harbor Entrance.—During the year every opportunity of smooth water has been taken advantage of to secure correct soundings of the neighborhood of the harbor entrance, and these have been mapped and alterations noted. Special attention was given to the condition of the bar immediately after heavy gales, with the satisfactory result that the appearances of improvements due to the influence of the training wall were unquestionable. There were severe gales from the north-east between the 7th and 14th May, and when soundings were taken immediately after they showed a considerable improvement upon the bar as compared with its condition in January, between the line of the wall and Taiaroa Head, and aho to the westward of the line of leading lights as it was at that time. The improvement in depth amounted to 9in. A shoaling of sin at one spot in the line of beacons was apparent, but this was of little consequence in the face of the widespread improvements at other parts. Again, heavy gales between the north-east to southeast on the 6th to the 10th, and loth to 17th June, gave a deposit of sand upon the line of leading beacons, reducing the depth by lft, but in a few days of fine weather the tidal scour removed the deposit. At the same time the channel towards Taiaroa Head had deepened by 3in, notwithstanding the unfavorable circumstances. All these changes for the better were distant in locality from where the dredge was working, and entirely independent of its work. The depth on the bar on the best line across it is now not less than 22ft lin, as referred to the low water level of Mr Simpson's survey of 1879. That survey showed 15ft as the limiting depth, so that the present condition is better by 7ft, or rather more than the range of a spring tide. Between May, 1882, and, say the middle of 1885, before these works were begun, and sufficiently advanced to have an appreciable effect upon the bar, a few weeks of weather bad enough to prevent the dredge working, even though there had not been any gales of pronounced severity, were sufficient to allow the bar to shoal up to 18ft 3in. A continued suspension of dredging would have resulted in a still great r shoaling. The gain in depth has been gradual, and, therefore, less noticed than had it been in one sudden increase. In 1887 the deepening has been from 19ft Gin to 22ft lin, or a total of 2ft 7iu, distributed over the various months. This is just the half of the mean difference between the high and low water, if we average both neap and spring tides. Let it be remarked also that this improvement has been effected by the works in their incomplete state, and therefore before they are in a condition of maximum efficiency. These changes are shown upon drawings forwarded herewith, on which you will also be able to observe other changes in the neighborhood. The most noticeable of these is the advance of the shoal water Beawards upon both sides of the training wall; and though it does not show upon the plan there has been considerable deposit in the north channel. Also the area of scour outside of the extremity of the training wall is considerable. Observe, also, that while the bank in the line of the wall has been pushed seawards, that part of Taiaroa Head has come slightly inwards, so that the whole appears as if it had wheeled round to oppose itself to the easterly seas. Coming inwards towards the harbor no change calls for special mention until we reach Harrington Point and the extremity of the North Spit. The latter has travelled in the direction of the flood tide, and its change of position has caused a deepening up on the side of the channel opposite. The unfortunate accident to the hopper dredge by the Omapere collision caused her to be off work, while being raised and repaired, from the 3rd January to the 12th February. Work with her was entirely stopped at the end of October, so that | her active time in 1887 was rather less than nine months. In concluding this report it is pleasing to j be able to put on record chat the officers of I this department Messrs Stephens and Mason as inspectors, and Mr Gillow as I draughtsman—have continued to discharge | their respective duties in a highly creditable manner in every respect.