Harbour Commission

Hawke's Bay Tribune, Volume XVII, Issue 204, 12 August 1927, Page 8

Harbour Commission

MR. PENGELLY CROSSEXAMINED.

engineers evidence. Mr. Gray’s cross-examination ol Mr. Richard Pengelly, who carried out the borings in the_ Inner ami Outer Harbours in 1925. was continued before the Commission yesterday afternoon. Mr. Gray: You recommended that a line of bores should be taken ashore?—Yes. That was not carried out?—No. You know that the board decided to widen the channel 1 from the other side?—No. Your reports of borings at the Breakwater showed silt and papa?— Yes. Silt is easy to more?—Yes. What about papa?—ft is very soft and easily dredged. If it were not lor the water a man could dig it out with a spade. What kind of dredge do you suggest would be required to do the pork?—An ocean-going dredge with a hull like that of a steamer. Wouldn’t a dredge like they have in Wellington do?—lt would find the work difficult You never went below 35 feet?— Yes, with one bore at the Breakwater I went down to 40 feet. Mr. Lusk: On September 10 von put down bore 81, you found between 31 feet and 35 feet friable limestone What does it mean’—Fragments of limestone. Did you ever have to make repeated attempts in getting a boro down?- Yes, when the anchor dragged down stream the gear often got bent and had to be straightened again. How were you moored in the channel?—By means of fi- » anchors and sometimes two lines asMve. The heaviest anchor would be about three cwt. ' In evidence given it was stated that you made your report in which you suspected a solid reef at the Inner Harbour, just prior to a hoard election. Comment was made that you posed not only as a rock borer hut as a rock diviner. I want to ask I did anyone ever approach you to get ; '..hat report?—No, certainly not. DISCHARGE FROM RIVERS. Mr John Dudley Holmes, M.1.C.E., A.M.1.M.E., N.Z., S.C.E., of the firm of R. W. Holmes and Sons, consulting engineers to the hoard, stated that he started with the board last August, beginning with making investigations regarding suitable store for harbour construction, 'io begin, ho wished to emphasise that his firm was not acting for any section of the board hue for the whole board. From a locality map witness explained the coastline from Cape Kidnappers to beyond Tangoio. The Tuki Tnki river, he said, was discharging shingle on to the beach, the Ngaruroro sand and silt, while the Tutaekui'i discharged silt into the Ahuriri lagoon. Generally speaking the littorel current was in a northerly direction, the shingle from the Tuki Tuki being carried in the early days beyond Napier. The shingle at the Breakwater was very fine, gradually getting coarser towards the Tuki I tiki. 'lhis was due to a grinding process that ensued as it was being carried along. The erection of the Breakwater 40 years ago had accounted for the travelling shingle going northwards having hri»n arrested. The supply northwards had consequently been cut off. Thorn was no shingle in the Breakwater Harbour, all soundings showing sand. I he Breakwater in cutting off the supplies going north, had resulted in denudation taking nl.aee along Har dings road and Westshore. The quantity of shingle depended on the floods of the Tuki Tuki, but owing to the lack of heavy floods of the last few years the beach south of the Breakwater to the baths showed indications of the beach having been lowered, which showed that accumulations of gravel had not taken place there of recent years. The remains of the gravel that hnd been ground into mud had been carried out into the bav by wave action, while the sand had been carried over the Breakwater or round it. Soundings taken for some distance out from the Breakwater to about a mile and a lisli west of the Inner Harbour entrance showed the depth of water -it every point. Witness put in records of soundings taken in 1927 with a comparative record taken in 1906. ‘lnside the Breakwater there were no indications of passing gravel. One chart showed the accumulations that had taken place at the Breakwater. Mr. Lusk: The whole of the Breakwater has shoaled has it?—Y’es. AVERAGE ACCUMULATION. Continuing, , witness said that between 1906 and 1927 the average accumulation was 17.700 cubic yards per annum. On March 14 last a progress report was made to the Ixiard on the matter which stated that an area at the Outer Harbour had silted in. the greatest siltation having taken place from close behind the Breakwater, the maximum silting m being 19 feet. The total accumulation since the commencement of the Breakwater was 494.200 cubic yards It was calculated that to make ar Inner Harbour in 1906 30 feet deep and 600 feet wide a total of 763.000 cubic yards would have had to be removed. The recent soundings showed that with the results of the erosion that had taken place the quantity of spoil to be removed to make such a channel had been reduced to 426.000 cubic yards. The soundings were completed later and a report was made on April 11. 1927, to that effect. Referring to the accumulation of silt, witness stated that the Waitaki river emptied large quantities of shingle on to the beach near the Timaru harbour, trouble being caused there through silting. It bad been reported that from 1916 tn 1921 there had been a yearly accumulation there of 163.000 cubic yards. The watershed of that river was approximately 3000 square miles, while that of the Tuki Tuki was 900 sauafe miles. 210 square miles of which were shingleproducing. The amount that was being deposited in the lee of the Breakwater was approximately in proportion tn that taking place it Timaru. Referring to the formation of the sand spit under the lee of. the Breakwater, witness stated that the sand was coming round the end or the apron, forming a .sand spit. A similar area was being formed at N’ew Plymouth, where constant, dredging had to be maintained. From the Auckland rock across to the Inner Harbour channel the material was not being spread over

the bottom or otherwise it would be shown to be shoaling and not eroding. It would also be seen that no accretions had taken place on the four, five and six fathom contour lilies—that was as far as soundings were taken, NOT A BAR. Witness explained that what appeared to be a bar in the neighbourhood of the dredged patch and the open sea was not a bar but the remains of the sea bottom that had not been eroded. Witness produced a photograpii taken in 1887 showing the 'Westshore and from which could be seen the denudation that had taken place ip till to-day. He further produced a tracing showing the shore-lines at various periods. He considered that if a small channel was cut through the apparent bar referred to above that the current issuing from ths Inner Harbour would scour sufficiently to keep it clear. The dredged patch in his opinion had undoubtedly assisted erosion in utiat locality. With a view to making a critical comparison of the Breakwater and Inner Harbour proposals be had dealt with the recommendations of Cullen and Keele and others on the ones tion. The chief thing about the present Breakwater was its height. The top of the cap was six feet above high water spring tide level and on the outside blocks had been pile 1 above the cap to an average height of 14 feet Just how many of the blocks would stay thete after a sea such a p occurred in 1910 it would be difficult to say. In his opinion the Breakwater was not of sufficient height to give adequate protection. Witness produced a photo of the sens in the 1910 storm going over the Breakwater. It was difficult to say how high the seas were but die photograph indicated that thev were of considerable magnitude. In his opinion no boat could have been held in the harbour at that time. Mr Lusk: It stands out by itself. I wish we could have another like it while you are here. HEIGHT OF BREAKWATERS. Continuing, witness quoted the height of the following Breakwaters. I Havre 12ft 6in„ Bizert;a 22ft.. Jlar- ; seilles 29ft.. Sunderland 19ft . I Alexandria 20ft., Algiers- 18ft.. ' Boulogne lift., Holyhead 28ft.. Los . Angeles lift 6ins., Colon 10ft. (i> i very sheltered place). Delaware 13lt. bins., Tyne 22ft.. and Portland. England. 28ft. In his opinion the height of the Napier Breakwater was in sufficient. Witness stated that he had accepted Cullen and Keele’s Breakwater scheme of 1925 and offered no criticism regarding it. In view of the board having adopted the Inner Harbour scheme witness had cone into it very carefully. The Breakwater afforded great shelter and could he, looked upon as part ol the lunsr Harbour scheme, INNER HARBOUR PROPOSALS QUITE GOOD. Witness considered the proposals to construct an Inner Harbour in its present position quite good. The wind tor a greater portion came from the west, but the Inner Harbour, being so close behind Scinde Island, was greatly sheltered. The harbour, hy means of the island, was sheltered from all winds from the south-east to the north-east. Once inside a vessel could he moored by . its own lines, i which could not be done in a less | sheltered harbour. The Breakwater j Harbour, when completed, would be less sheltered than the Inner Harbour. Springs would always have to be used in that harbour. DID NOT CONSIDER REEF EXISTED.

Concerning the borings witness said that he could not follow the evidence of Air. Pengelly when lie said that he never drilled through a larger boulder than 14 inches. In bore 42 Mr. Pengelly showed that from 22 feet to 27 feet he wet t through large boulders. Personally witness did not consider that tl.« alleged reef existed. Continuing, witness said that Mr. Pengelly. in refusing to allow presence of a supervisor made it doubtful for an engineer to accept the borings without check borings having been taken. Witness ■ had been through the samples of the borings now in the board’s office, being of the opinion that most of them were debris if greywacke rock. Dredgings had bee: taken by Mr, Finch of the' channel with the Browning crane. Mr. Finch had stated that the maximum depth reached was 34 feet below low water. In driving the last two hays of piles it was found that the sub-strata below the 10 feet thickness of hard conglomerate was of a soft material. This hard layer which was now being picked up ball hitherto resisted the efforts of the J.D.O.

The Commission then adjourned until 10 o’clock this morning.

Correction: In opr printed report of Mr Pengelly’s evidence yesterday, an error occurred in the sentence “a man who was not a driller was capable of drilling,” It should have read: “No man who was not a driller was capable of drilling.”