PATEA HARBOR BOARD.

Hawera & Normanby Star, Volume LXXVII, Issue LXXVII, 3 June 1919, Page 5

PATEA HARBOR BOARD.

MONTHLY MEETING.

The monthly meeting of the Patea Harbor Board was held yesterday afternoon. Present: Messrs A. T. Chn&tensen (chairman), A. Pearce H. l>:ekie, E. A. Pacey and J. Verry. ■ ZLE IiOANTILE STATS-OWNED FLEET. A L-tter was received from the Act-tii-ig-iVime Minlsier, m rep;y to the j hoard's resolution urging that the j Government should take steps to secure a State-owned mercantile fleet. Tins matter, Sir James Allen said, must of necessity stand over until the return of vhe Prime Minister and Sir Joseph. Ward, whin it would be rej luTed to -them for consideration I Mr G. V. Pearcd, M.P., wrote with j iv-ierence to the foregoing, and said i the ma:tar would receive his most I careful jjo.osßgration. Some time since i a rricetmg in connection with establishing a line of shipping between New Z<M.la;:d and the Mother Country was held in Wellington. The suggestion adopted by the meeting -was that » shipping company should be formed partly owned by the producers and par!:!-- by the State. A committee of s^ven v.-as set up to go further into the master. He (Mr Pearce) was on the committee. On account of the war and the price of steamers the matter had been held in abeyance, but no doubt when peace wais .signed meetings would be held and the matter further considered.

PILOT'S REPORT.

The pilot (Captain Tinney) reported as follow*: The channel over the bar is straight •bearing S.W. by S.fS., with about 13ft at high water at spring tides and Bft 6in at high water neap tides, and about 170 ft -wide. The bar was sounded on Jun-e 1, when there wa 13ft on the bar and 12ft just inside -the _ walls, and then deeper water up to the tide guage. . There have been 21 arrivals and 22 departures during the month; 13 went out on the lights. On the 30th at 10.15 p.m., when the Kapuni was going out she. kept too much over towards the guide pier and dragged through the sand and then took at sheer over towards the eastern wall; which struck stem on. The steamer then went astern. and then went out. All along the breast of the guide pier there is between 14ft and loft of water in the channel at high water tides. Everything fit the station ;« in good work- • ing order. The chairman said the mkJhap to the E>puni was very unfortunate for the shipping company. The steamer put in at Wanganui and her cargo was trsn^-hipned. He did not know what damage the vessel had sustained. The report was adopted. ENGINEER'S REPORT. The engineer (Mr R. S. Thompson) reported, inter alia, as follows: ■During last niontji good progress was imade witih the breakwater extension contract. On the eastern breakwater three caissons were deposited and consolidated, and two caissons manufactured in the yard., On the western breakwater ,one caisson was deposited and consolidated. The total length of the western breakwater extension to date is 149 ft 6in and the eastern breakwater 294 ft, which now overlap® the western breakwater a length of 112 ft 6in. For work done in connection with the eastern breakwater a progress payment amounting to £1435 4s has been certified to., aid for work done in connection with the western breakwater the payment is £527 11s Bd. River Channel—Beacons have been placed to mark the sailing course at the railway viaduct bend, and it is s~ proposed to also erect beacons on the line of the sailing; course round the bend below the wharves. Estimates will also be prepared as to the cost of placing lights on these beacons. Wool Store—A quantity of wool, hides, tallow, etc., was received at this store for shipment. Regarding the material in stock, after due allowance has been made for material brought inio stock and material used out of stock there is a balance of £78 6s 6d in favor of the contractor. The position of fhe contract, including to-day's payments, is as follows : £ 6. d. Eastern breakwater ... 21,450 011 Western breakwater ... 18,066 5 3 Cap eastern breakwater 3,431 3 6 Total payments 42,947 9 8 Total advance made to contractor in cash for material 9,421 16 9 Amount refunded in cash 5,226 2 8- ■ Advance balance 4,195 14 1 Total amount of contract 67,500 0 O Cap eastern breakwater '5,164 14 0 1 72,664 14 0 ; Less total payments ... 42,947 9 8 29,717 4 4 Less advance balance ... 4,195 14 1 i .. ~~—*——~^ — : Balance due to conl tractor , ... 25,521 10 3 | Dredge Wallace—Tids dredge haa i been employed dredging alongside the ' wharves and the river channel. Ow-

ing to a defective steam pipe work was stopped on the 19th ult., and on. the 28th ult. a start was made to drive sheet piling at the town wharf. The chairman moved the adoption of the report, which, he said, was satisfactory. Mr Paoey seconded the motion, which was earned. ? It was decided to obtain the opinion of the shipping masters trading to the port in regard to erecting lights near the railway viaduct A DEPARTMENTAL REPORT. Mr R. W. Holmes, of the Public "Works Department, who recently inspected the harbor works, forwarded an interesting report, which, stated, inter alia: The principal item which requires attention is the question of the most suitable form of foundation for the moles, and with regard to this the following appears to be the position: A doubt appears to have arisen as to the suitability of the caisson form of construction through settlement of some of the caissons in the left or southern mole. (1) The settling of the caissons can only be due to one cause, viz.. orosioa of the material on which they stand, owing to its being either too soft, as in the case of deltaic silts, or it is too unstable, as in the case'of sand. In. ihe former case the waves striking the blocks may force water beneath them with sufficient velocity to scour away i io easily eroded silt; this action may be assisted by motion of the block3 > wliieh will tend to increase if the founHtion is scoured in an uneven manner. In the latter case the sand would be> washed out irrespective of any motion '■"' the blocks, owing td itg want of cohesion and incompressible nature. It is most probable that the motion of the onissons which has been observed, is due to the effect of scour of the foundation, rather than that the motion has caused

■he scour. However, when either action •id begun they would be interdependi't. (2) In the present case, however, :': is probably useless to discuss th»

cause but To accept the fact that settle-; ment has taken place, and at once to proceed to consider a. remedy. (3) Instances of settlement are common in connection with breakwater construe-1 tion, and. it is usual to overcome it either by allowing the settlement to continue until it stops, or to prepare the foundation by depositing a sufficient area of stone (in pieces of suitable size; to carry the weights of the block, with a minimum of settlement. It being borne in mind that it is impossible, toj .Wholly prevent settlement, particularly in such structures thafcrare now under review. In the present case, it being not convenient to wait the tim tt necessary for settlement to cease, the alternative must therefore be considered. At the commencement of the extension oi the left wall, the caissons were placed on the random blocks forming the foundation of the former work; this foundation has proved effective, no noticeable settlement having occurred. This appears to be a sufficient proof that a foundation formed of random placed blocks will prove satisfactory. Although no further settlement may take place of those caissons which have been affected, it is desirable t<> provide some protection, which may be most easily done by placing some random blocks along each side. These Will tend to prevent water being forced beneath the caissons, and at the same time to provide some lateral support. (4) The height to.which the foundation blocks, and the side supporting blocks should be brought, is dependent upon the depth of water on the bar, as there must be sufficient water over them to allow of safe navigation in the channel beneath the moles. Assuming, for the sake of argument, that the depth on the bar will be 6ft. below low water spring tides, and allowing 2ft. for pitching or vessels, and one foot clearance, then it will be quite safe to carry the random work up to within 3ft. of low water spring tides. On the outside or the moles the supporting blocks may, of course, be placed to reach a higher level, which i» lecommendetl. The foregoing figures are assumed, and they may require correction. They ar 6 quoted to exemplify what is considered to be the correct method of determining the required height. The junction of the caissons with the foundation is always the most vulnerable point for attack by tlhe waves, or other destructive force. Therefore, it is desirable to found the caissons lower than indicated so that the blocks may cover the junction. (5) Along the outsdde of the right, or northern wall, or breakwater, it is desirable to place some heavy blocks at random, in order to strengthen it to resist the stroke of the heavier seas now that deep water is being reached. It i,s expected that this will be found more economical than increasing the width of the caissons. The sloping broken surface presented by the random blocks is particularly effective in arresting the force of the eeas, and thus assisting materially in preventing the washing of sand over the wall into the channel, which is a most important desideratum. These blocks should be carried as high as funds will allow.

(6) It is recommended that the following additional points should receive consideration: (a) The position of each of the blocks at the outer end of the breakwater should be careful:y noted, in order that any movement" towards the channel may be detected. The positions should be studied from time to time, in order that any movement may be arrested before they reach a dangerous position, (b) The inside'training wails must fee maintained* (cj Wherever the sand drift has collected along the outside of the breakwater, should be planted, in order to fix it and stop as much as possible sand being wind drifted into the channel. As the wall is extended the accretions of sand will increase, (d). As the maintenance of the port of Patea in a navigable condition depends entirely upon the volume of the tidal compartment, any tendency to encroach on it should be prevented. One cannot help noticing the silting and encroaching in the area cut off from the river by the railway line. When the line was constructed a very useful volume of water used to flow in and out of this lagoon. It would materially assist scour on the bar if this area were dredged down to a little below water mark. (c) It is usual to vest in harbor boards all reclamations from the sea due to accretions, whether they be caused by natural or artificial influences. The Board is recommended, when the time is opportune, to take the necessary steps to have any accretions which may occur vested in itself. This will give the ] Board legal control, aiid thus enable it to plant and protect it, which is absolutely necessary in the interests of the port. With reference to the width of the breakwater, I am of opinion that the present width of the caissons is sufficient if founded on random blocks at the depth mentioned, and protected along the seaward side by random blocks as described, and weighing not less than 5 tons in the shallow water, but increased to at least 15 tons at the outer end. Should the walls ever be continued, then these heavy blocks could be lifted and used again further out, because accretions along the weather side of the breakwater will follow the advance; the consequent shoaling of the water will allow- of lighter blocks being used with safety." The chairman moved that a hearty votn of thanks be accorded to Mr Holmes for his valuable report, which bore out that the Board, in constructing the harbor improvements, was working on right lines. It was always gratifying to have a visit from a Government officer. The Board intended to reclaim the lagoon referred to in the report, but Mr Holmes' advice that it be deepened so as to form a washout basin was *a good one. The trouble would be to get a dredge in there.

Mr Dickie, in seconding the motion, said the report was certainly a valuable one. He noticed that Mr Holmes suggested the strengthening of the western wall, and no doubt the Board would take this into consideration when dealing with ways and means.

The motion was carried