Napier Harbour Question

Hawke's Bay Tribune, Volume XVI, Issue 8, 21 December 1925, Page 2

Napier Harbour Question

Cullen and Keele’s Second Report THE BREAKWATER RECOMMENDED Smaller Initial Outlay and Maintenance Provision For Four Additional! Berthages IMPOSSIBLE OF FUTURE EXTENSION Concluding their report, Messrs. Cullen & Keele say:— We are of opinion that the adoption of the Outer Harbour Scheme with one pier which, with the Glasgow Wharf will afford accommodation for four ocean liners, is to be preferred, and recommend accordingly. Briefly, our recommendation is based on the smaller intial capital outlay required for the Outer Harbour, whilst the difference in the estimated' annual maintenance for the two scheme would represent, if capitalised, a further large difference. The maintenance of the Outer Harbour would require no dredging, save a little minor work at lengthy intervals to clean up the berthage, whilst the Inner Harbour would require the keeping m continuous commission a large dredger with all that so doing involves. ‘ From the point of view of the public convenience there does not appear to be any very material difference between the two harbours; this factor, however, should not be considered a dominating one were it otherwise. The Outer Harbour possesses an advantage from a ship’s point of view in as much as it would be easier to enter during bad weather.

To the Chairman, Harbour Board, Napier.

Sir, —In response to the inquiry conveyed in your secretary’s letter of Nov ember 14th, 1924 t and the subsequent invitation to visit Napier and advise the Board on the matters enumerated we arrived there on April 22nd, and de voted the following thirteen days to investigating the questions submitted, which were:—

(a) The probable cost of completing the Inner Harbour to give safe accommodation for four ocean liners and other vessels that require berthage. (b) The question of erecting a half tide wall controlled by sluice gates or otherwise. (c) The probable cost ot completing the Breakwater Harbour to give safe accommodation v for four ocean liners and other vessels that require berthage. (d) The extra cost of maintenance over the. present cost of each proposal.

On meeting the members of the Board formally, the desire was expressed that we should consider a suggested alteration in the direction and position of the entrance moles and channel into the Inner Harbour, and that we should make a specific recommendation as to which harbour we considered it most desirable that the Board should develop to the extent indicated in its inquiry. The latter request was also conveyed again in your secretary’s letter io us dated May 12th, 1925. At date of our visit certain borings had been taken in the Inner Harbour and others were in progress at th© Breakwater Harbour We were furnished. with the results and we re quested that additional bores at each place should be taken at the sites wo indicated. These latter having been taken and the results forwarded to us we now have the honour to submit the following report upon the questions submitted.

In our report on the Inner and Outer Harbours of 1912 we expressed the opinion that a satisfactory harbour could be obtained by developing the Inner Harbour on the lines indicated, and also that the Outer Harbour could be completed to satisfactorily meet present and future requirements. The designs for each harbour, which we submitted ,wcre capable of extension to accommodate a large future increase beyond the requirements of the existing trade of Napier and district. The present view' appears to be that th** limited increase indicated in our instrue tions will be adequate. So far as the Inner Harbour is concerned, the area is not now limited r* l !«’«>• than we pro posed in 1912, the rail and road embankment having been constructed dn the site which we agreed upon in consultation with Mr Holmes, the Engineer-! nChief for Public Works in 1912. The Outer Harbour, if now constructed to accommodate a certain number of vessels cannot be enlarged hereafter except at the cost of the removal and reconstruction of the Mole in the posi tion required. The present Engincer-in-Chief, Mr F. W. Furkert, having in his report of August 23rd, 1924, to the Hon. Minister of Marine challenged th© soundness of our conclusion, as expressed in our report of 1912, that a satisfactory harbour could be devloped at the Inner Harbour, we deem it necessary to say that after further investigation and a careful consideration of Mr Furkerf’s opinions we do not accept them, and are confirmed in out former conclusion. The opinions ex pressed by Mr Furkert in support of his conclusion are as follows, viz:— (a) Difficulty of maintaining an entrance channel. b) Danger to vessels entering. He also suggests that our estimates of cost in that report were unreliable. Taking those seriatim Mr Furkert rests his belief on the difficulty of maintaining an entrance cutting on the existence of a sand drift from tinsouthward over its site. Tn this opinion he acquiesces in that bv Messrs Alason. Alaxwell and Williams in 1909. Neither of the reports referred to offers any reason whatever for their very positive statements affirming the existence of a sand drift. Tn our report of 1912 we stated that we could see no reason to believe in the aliened sand drift. As a matter of fact the positive statement of the prior report ha<] inclined us to believe that such drift existed: it was only after personal stulv of the matter at Napier that we came to a contrary conclusion. based on the lack of any cause

for such drift and the entire absence of any of the indications ITiat would certainly show did such drift exist as set forth in our report.

Our conclusion that no such drift exists, as was supposed, is fully confirmed by the condition of the “pool” some GUO feet long by 200 feet wide excavated by a dredger in November and December, 1911. Its location was on the site of our proposed entrance channel and practically on the crest of what may be termed the bar off the entrance between the moles. This test cut is stated to have been dredged to a depth of 34 foot nt L.W.S., the original depth on the site being 18 to 20 feet at L.W.S. Examination at intervals throughout 1912 and 1913 showed that soon after its completion the side slopes had flattended down very considerably'reducing its depth thereby on an average of 8 feet, after which very little change occurred. In 1921 the Board’s Engineer, Air Finch, examined it and found that the depths of 1912 had actually improved slightly durling the 9 years’ interval. He also advised that at the centre and at the inner side he found that the bottom consisted of silt, cockles and pipis, which, in his opinion, came from the J nner Harbour.

It is impossible to reconcile the foregoing with the existence of a sand drift along the coast, and in our opinion it offers conclusive evidence confuting the opinions expressed as to the existence ■of such drift. Alessrs Mason, Maxwell an<[ Williams in 1909 stated their opinion to be that the sand bar and the sand drift was the crticial feature in connection with the Inner Harbour, and that the latter would obliterate a cutting. Mr Furkert states that “The “agitation of tho sea bottom during “rough weather, combined with the “drifting of sand up the coast which is “still in progress would cause a “continual filling up of the channel.” A sand drift would certainly obliterate a cutting. As the small deep cut made has not been obliterated or even altered appreciably in 10 years after its side slopes fell in the interesting theory must be given up. We consider the objections urged against, the proposed entrance channel as quoted above have no warranty and that as we reported in 1912 such cutting could be made without difficulty and bo easily maintained. A further objection expressed by Mr Furkert was that it would bo dangerous for large vessels to enter the Inner Harbour when heavy seas prevailed, ajid also on account of the current velocity, but he would appear to have overlooked the fact that by doubling the size of the channel (between the moles) as wo proposed, tho current would be reduced. We recognised a limitation in these respects in our 1912 report and stated then our opinion that “at high water any vessel visiting “Napier could enter or leave without “risk at all times, except perhaps dur ing storms of such exceptional severity that no harbour in Hawke’s Bay “could be approached without risk. “Such storms arc fortunately of rare “occurrence.” We do not think any other limitation would exist. It must be borne in mind that at Napier fine weather and smooth seas prevail nearly all the year round* The preference of Mastqj's of vessels for a Breakwater Harbour is natural and easily understood—they consider the latter is easier to enter. It must not bo assumed, however, that that means that the Inner Harbour could not be safely entered. Mr Furkert has at some length criticised our 1911 estimates. We stated that with the plant we proposed, certain works would be carried out for a certain cost within two to three years. To contrast this with the cost of work done by other methods, and spread out from 1914 to 1924 and then draw unfavourable conclusions seems strained, to say the least. Again, Air Furkert states:— “The cost of the Quay erected shows “that the estimates, which, in my “opinion, were far too low in 1912, “must be now entirely disregarded “This applies with particular force to “the item of £6OO which is all that “appears to be allowed in the report “for the upkeep of everything oxm “the bar dredger. The upkeep of the “works at Napier cost last year “ £12,800, and even allowing thai “some of this is of a non-recurring “nature, it seems unduly optimistic “to put it mildly, to think that a port “such as was contemplated by Alcssrs “Cullen and Keele could be kept up for ‘ ‘ £6OO a year. ’ ’ What we actually reported was as follows: — “With regard to the annual cos«t or “working the Harbour on its commie “tion to the extent indicated, we do.

“not care to hazard an opinion which “if not based on a more intimate “knowledge of the trade of the port, “kibour costs, and of the numerous “factors which enter into such a cal- “ eolation, than we possess —woitid be “largely conjectural. We feel assured “however that any information on this “question which your Boaid may desire “can be furnished by your able sccrtc“tary. Ho far as the works are con- “ corned we consider that for their an“nual maintenance £7876 will suffice “which includes £6OO for the quay and “sheds and £7276 for the dredger.”

In quoting the whole expenditure m the existing harbour accommodation of Napier in 1923, some £12,800, and contrasting this with the £6OO per annum we allowed in 1912 for the upkeep of tho new quay and sheds which wo pro posed Air Furkert Seems, to put it mildly, to have been over hasty. We did not suggest that the whole port could be kept up for £6OO ; — that sum was additional Io tho then existing expenditure, as we clearly stated. Mr Furkert further states: —“To “take Cullen and Keele’s scheme now “point by point they propose to dredge “a channel ... to the end of the “new moles where the channel would “contract to 230 feet bottom width be- “ tween moles 400 feet apart.” What we actually proposed and showed on the plans was stated as follows,

“2. The removal of tho "East Mole “and enlargement of the passage to “give a width of 500 feet reconstruct“ing the East Alolo in the manner “shown on plan accompanying.” “4. This dredging of the passage “between the moles to a bottom width “ of 300 feet. ’ ’ The -foregoing as a method of criticism speaks for itself and wo consider further eoipment unnecessary. INNER HARBOUR. We have formerly dealt fully with the various questions concerning the Inner Harbour, and refer to our 1912 report in this connection. It happens that the accommodation lor four ocean liners, and other vessels that require berthage, which we are now asked to estimate the probable cost of, nearly corresponds in extent with that we proposed and illustrated formerly, and consequently that the works then proposed arc still necessary. Of those works, the road and rail embankment has been carried out. the Tutaekuri River lias been diverted to discharge outside the embankment and the West Quay has been constructed for a length of 1343 feet westward from the Iron Pot, but to a design of the Board's officers that will allow a depth in its berthage limited to 20 feet at L.W.S. T he Harbourmaster informed us that this quay of *1343 feet in length was required for vessels nbrw using the Inner Harbour, and would suffice for all other vesels that required berthage, leaving the new accommodation required to be that for the ocean liners. This accommodation we fix at 2600 lineal feet of quay, and our estimates are for that length. For the various dredging works wo recommend the same type of dredgers as before, with the same disposition ot .material. I he Basin required would be of tho same width, but about 150 feet shorter, and its area would be S 3 acres as against 86. V in our original proposal, the approach channel and the channel between the moles, and the widening of the latter channel with the extension of the moles would be as before. The Board has suggested to us in the secretary’s letter of September 1-1 th, 1925, that as tho existing mole on the West side of the entrance is in bad order through decay of the timber crib used in its construction we should consider the widening of the entrance by setting back the West side 100 feet instead of setting back the East «ide as shown on the plan accompanying. We consider that there is no engineering objection to this and that the widening of the entrance in that manner would answer equally well with that proposed. In fact we are of opinion that the removal of the West More is preferable, but we considered that as it would involve the resumption and demolition of tho Freezing Works 'i, would he too costly. We are unable »o estimate on the cost of the latter, but the board can doubtless ascertain the approximate cost. Wo furnish estimates of the cost of removing tho East Mole as originally proposed and also the alternative to shift back the West Mole. To the latter is to be added whatever amount is ascertained to be the cost of resuming and demolishing the Freezing Works, the total amount will then he the cost <>i auepting the alternative, and if this total be less or approximately equal io the cost of widening by shifting tim East side Mo’e then we recommend that the widening be done by removing hack the West Mole 100 feet.

Assuming that interference with the Freezing Works would be too costly and that the East Mole would have to be set back 100 feet as we proposed in 1912, we repeat what we then reported, viz.:— REMOVAL OF EAST MOLE. The extra width of 100 feet is demanded for navigation, and to obtain r* suitable cross sectional area fof- the Lagoon and upland water. With a width of 500 feet and a dredged cutting 300 feet wide by 31 feet deep, the present .disturbed currents will be reduced in velocity.

It is proposed to remove the timber crib work entirely, to remove the material behind to the necessary extent, and to protect the natural slope left with largo random stones as shown on type section. This work to be done in short sections, finishing each one before commencing the next. PROTECTION OF WEST MOLE. The West Mole of timber crib work requires attention, arid it is recommended that such protection consist of large stones forming a natural slope according to section shown on plan. This protection to include the outer or West side beyond the beach line as well as tho inner or channel side. In tho event of tho alternative, which we indicate on the plan in dotted outline, proving less costly and being adopted the Channel side of the East Mole and tho end beyond the beach line on the outside would be protected with large random stone in the same manner as that shown on typo section for the West Alole. The present West Mole would be removed entirely and the ground behind it excavated to the proposed width, the slope left being protected with large random stone. The work would be commenced from inside, in short sections, finishing each one before commencing the next. From the H.W.L. outside the new Mole would be built to the type section shown for the extension. EXTENSION OF MOLES. The extension of both Aides for 400 feet we consider to be necessary and recommend accordingly. The extension will preclude any shoaling at the ends due to wave movement, it will assist in diminishing wave movement inside, and will aid the sluicing action of the ebb tide on the bar to maintain tho cutting through the latter. Both extensions should be of heavy random stone as shown on type sections. The extra width will admit a slightly larger wave movement, but the rough stone sides will tend to damp the movement, and on account of this, and of the extra length, the wave movement will not exceed that at present existing. Its effect in the new basin will be quite negligible. DREDGING BETWEEN THE MOLES. We reported in 1912 as follows: — “From personal tests and from information supplied to us we find that tlie bottom consists largely of bourders, interspersed with patches if shingle, for a length of about 1500 feet, or up to a point approximately off the Iron Pot, after which dark sand or sand with shingle occurs. The boulders are rounded and vary in size up to about 3 cubic feet, averaging about 60 lbs. in weight. The Alaster of the grab dredge states that the largest that ho has raised was under 4 cubic feet, and that he never experienced any diffiiculty in grabbing. “With a suitable plant we apprehend no difficulty in dredging this channel; a large amount of the stone raised could be advantageously utilised in the construction of the training wall.” The borings taken this year between the Moles confirm the above entirely. We consider that, the channel should be widened and the Aloles be extended before dredging be commenced. On our recent investigation we came to the conclusion that considerable quantities of sand and possibly small shingle are being deposited at times in the channel from the beach outside the West Mole being passed through the gaps in the crib work of the Mole under the high velocity of the flood tide entering thereby accelerated by wave motion. This explains the fact mentioned to us by the Harbour Master, Captain White-Parsons, R.N.R., that occasionally ho had found a sudden loss of depth in the channel in that vicinity of as much as three feet.

With the restoration of the Mole and the addition of the protecting stones this intrusion of sand would cease and some gain in depth would probably occur where the bottom was of sand from scour alone. EXCAVATION OF BASIN. This is work of considerable magnitude involving the removal of 4,134,000 cubic yards to provide the basin shown, i.e., 4050 feet in length from the Iron Pot with a width of 1000 feet and depth of 31 feet at L.W.L. From a consideration of borings taken by the Board and of all the evidence available it is considered that the material to be removed consists of silt sand, gravel and shingle in varying quantites with a small area of sofo “papa” along the frontage of the newly built West Quay. This material as we saw it, consists of a dark grey or blue clay of a tough consistency, but we consider it dredgablo with the dredging plant we recommend. To dispose of such volume wo repeat our former recommendation, i.e., to reclaim the North and South Ponds and the area behind the proposed quay. These areas will, if raised to tho height of the adjacent ground receive about 1,200,000 cubic yards. Tho remainder could Ixi disposed of by reclaiming areas about the East end of the Taradale road and to the South thereof. If necessary part could bo taken to sea by the Bar Dredger. Dredging outside the Training Wall, of which there would be some 1,100,000 cubic yards if no scour took place, could be most favourably done by piping the material across the Spit and discharging on the Outer Beach, employing the Basin Dredger for the purpose after the Basin is completed. TYPE OF QUAY. recommended will be seen froqj the type section drawing. It consists of a skin ot rubble on the slope left after dredging and on the bulk head line a rubble bank up to 1 foot above L.W.S. to form a foundation for the rat-proof retaining wall of L-shaped trestles. A reinrorced concerete wharf fronts the same. DESCRIPTION OF THE DREDGING PLANT RECOMMENDED. Bar Dredger.— To bo a seagoing trailing suction hopper dredger in accordance with the specifications furnished with our Report of 1912. Its length would be 204 feet, beam 38 feet, depth 14 feet, and hopper capacity 27,000 cubic feet. Boulder Dredging Between Moles.— We repeat our iormer recommendation that this work be done using 2 grab dredges with high purchase buckets ot about 40 to 50 cubic feet capacity. The type of machine to be that with an independent boiler delivering steam to the crane engine through the king post and also supplying steam to the mooring winch of 6 barrels. In view of the tidal currents the barges carrying these machines should be shaped to offer a minimum of resistance, the spoil barges could only be moved with the current, and we recommend that four be procured. The small tug to be used with them should be of as large power as possible. Basin Dredger.— To consist of a steel or tnnbei barge 100 feet by 28 feet, carrying a 22-inch dredging pump, motor driven; the suction pipe to reach 40 feet below water level and to be provided with a spiral rotary cutter— Robinson type A warping and operating winch with four independent barrels and a spud hoisting winch witn three independent barrels. Cutter and winches to be motor driven. The barge to operate by swinging the bow with side warps, the stern pivoting alternately on one of the two spud piles, working in trunkways aft. In recommending this type in 1912 we stated that in view* of the long distance that material would have to be piped we recommended the adoption of a shore power house and the transmission of electric current to motors in tho barge, so that a relay pump could be easily introduced in the pipe line for long distance discharge. The material is heavy ’and the quantity so large that we were of the opinion that that was the only satisfactory method of dealing with it. We find that in 1923 when building costs were ■cry high, the Board invited tenders for a Basin Dredger, entirely selfcontained and worked by steam. This

meant a large hull to carry heavy boilers, engines, coal and water, it was naturally costly and would probably have little or no value when the basin was dredged. Moreover it would need regular periodic docking and the provisision of at least one relax’ pump in the pipe line, a costly matter with the required power, would have been necessary to get the material far enough. We think it fortunate that the Board did not adopt this type by accepting any of the tenders received. The pump motor would deliver 700 brake horse power to the pump; the cutter requires 90. the operating winch 15 and the spud hoist winch 10 brake horse power delivered by the respective motors. , The relay pump would require 150 B.H.P. delivered. Details of the power house and electrical equipment are appended. W.T. boilers and T.E. engines are proposed. We again refer to the values of any reclaimed areas for consideration as offsetting part of the cost, hut cannot add anything to our reference as contained in our former Report. We now submit specifically our reply I to your request for an estimate of the I probable cost of completing the Inner Harbour to the extent mentioned. ESTIMATES OF COST—INNER HARBOUR SCHEME. DREDGING. Entrance Channel. 600 ft. wide to 35ft. £25.310 j Channel between I Moles and wideni ing same 40175 Basin. 1000 ft wide i as shown 86,125 Outside Training Wall up to Bridge 18000 £169610 PLANT. 1 I Seagoing Bar Dredg- ; er, as per specifica--1 tion 65000 2 Grab Dredgers complete 12000 1 Launch Tug 3000 4 Wood Spoil Punts 3000 1 Basin Dredger with 22in. pump &000 Floating pipe line 900 ft. 3300 Shore pipe line 4000 ft 4000 Power House, com- < plete as per detailed i estimate 44338 142638 — £312218 ! QUAY MOLE EXTENSION. ETC. Quay’ 2600 ft., complete witn sheds, and road behind .. 217000 Training Wall utilising boulder excavations 3000 Removal part of point opposite the Iron Pot and revetment 3000 East Mole extension 400 ft. and facing channel side ...... 20500 West Mole extension 400 ft. and protecting eixsting Mole . . 21500 Lighting 1 (XX) 266000 578248 Contingencies and engineering, 5 p.c. . 29912 Total estimated cost. including plant . . £608,160 If the West Molo be cut back instead of the East Al ole then the total estimate quoted above would be reduced in respect of the following items, viz.: Channel between Moles and widening'; same and the removal of part ol the point opposite the Iron Pot and revetments making a reduction in the estimates of some £6250, and bringing the total estimated cost to £601,305, plus the cost of resuming and removing the Freezing Works, which latter cost we are unable to assess, but the Board’s Officers would doubtless be able tovise thereon. On completion of the work indicated the electrical equipment estimated at £38518 would have a probable sale value of between 33 to 50 per cent, ot its cost. The reclaimed areas would also be valued, and the amounts when realised on would be credited to the cost of the works.

DETAILED ESTIMATE FOR POWER INSTALLATION.

BASIN DREDGING. Power required cn Dredge. 700 B.H.P. for 22-inch pump. 90 B.H.P. for cutter on suction pipe. 15 B.H.P. for operating winch. 10 B.H.P. for spud hoist, after jvinch. 815 B.H.P. Total lor Dredge. Power required for Relay Pump. 450 B.H.P. Transmission efficiency at 72 per cent. Power at engines equal to 1110 B.H.P. for Dredge 630 B.H.P. for Relay Pump 1740 Total B.H.P. Three triple expansion, enclosed, quick revolution, sei I -lubricating steam engines direct coupled to three 400 K.V.A. alternating current generators 50 p. 2000 volts 3 phase. Two sets required to supply Dredge, the third for use when relay pumping required, and may be considered a reserve set.

EQUIPMENT— PARTICULARS AND ESTIMATED COSTS. ENGINE ROOM. Three 580 B.H.P. quick revolution engines Three 400 K.V.A. A.C. 3 phase 50 p. 2000 volt generators running at approximately 350 r.p.m. Three sets condensing plant, 9500 lbs. per hour steam capacity, motor driven air and circulating pump One set switchboard insts. and liftings One set piping Total, engine-room £19492 BOILER BOOM. Three water tube boilers, 2900 sq. it. heating surface Three duplex teed pumps, 980 gallons per hour One set Hotwell, tanks, pipes and fittings One sft. x 100 ft. steel <4iininey 1 luce sets brickwork One set brickwork m flues and chimney base Total, boiler room £8893 GENERAL. i.oiler and engine-room, say, 601 t. x 15011. x 3011. galvanised iron and timber /. . 3600 Total Power Plant equipment '30,58u Erection at 10 per cent. 3058 £33613 1)R EDGE EQ UI PM ENT. One 780 B.H.P. motor for pump. 3 phase A.C. 50 p. at approx. 600 volts and 210 r.p.m 2012 One 100 B.H.P. motor for suction pipe cutter, 600 volts, 460 r.p.m. A.C. 3 phase .. 481 One 17 B.H.P. winch motor, 600 volts, <875 r.p.m 93 One 750 K.V.A. Step-down Transformer. 2000 to 600 volts. 50 p. A.C 2362 One 12 B.H.P. motor for spud hoist 79 One set induction ammeter, voltmeters indicating Watt meters, auto oil switch, etc. 262 Total Dredge equipment 5289 Election at 15 per cent. 791 £6OBO RELAY PUMP GEAR. One 500 B.H.P. motor. 600 volts, 50 p. 210 r.p.m. approx 1400 One 350 K.V.A. Step-down Transformer 2000 to 600 volts 1102 One set switch gear 142 Total Relay Pump equipment 264 I Erection at 15 per cent. 396 £3040 TRANSMISSION. Copper, poles, etc., etc., .... £1575 Total equipment and transmission £44338 DREDGE. Steel Barge. 100 ft. by 28ft. by 7; winches, pump, suction, pipe, etc., etc £BOOO It was mentioned to us at Napier that there was a possibility of powei being available from a largo hydroelectric power station to be established at some future time. Should this be an accomplished fact and power could be purchased cheaply then the loregoing estimates would no reduced by the cost of the power house we recommended- i.e.. by some £33,643 and the “Dredging Estimates” in respect oi the estimated cost of dredging the Basin and outside the training wall would be increased by the price to be paid for current, for the power indicated ; for a period of about 3 years. Until this price was known the increased amount of dredging could not be stated.’ Assuming for illustration that a special rate of £lO per horse power per annum was quoted, then 815 H.P. being required and used the annual cost would be £Bl5O plus any relay pump power taken. The power house when the dredging was completed, would, we think, have a considerable sale value so that its nost less its sale value is to be set against the cost of purchased current. HALF TIDE WALL.

The question of erecting a hall tide wall controlled by sluice gates or otherwise as referred to we found was a proposal for a wall to control the passage of water into the Ahuriri Lagoon through the railway bridge opening. The proposal, however, does not appear to have been formulated in detail and w© have concluded that the underlying idea was to so control the passage of tidal water that the velocity of the tide between the entrance moles could be regulated in the interests of navigation, or in those of dce]>ening operations between the Moles. Through the courtesy ot the Resident Engineer at Napier of the Public Works Department, we obtained a section of the around under the bridge as at the end of 1924 with current velocity measurements at the same place. From a. consideration ot these data and of the conditions between the Moles we conclude that the bridge opening at present does not admit as much water into the Lagoon as formerly, the reduction probably amounting to 16 per cent. In our proposals of 1912 the width of the opening shown was some feet, a width proposed in Air. Geo. Nelson's original scheme, with which we concurred. 1 he opening as built is some 1220 leet wide. Scour has occurred at each cml of the opening and after reaching a certain depth has been arrested by the Public Works Department tipping stone for the purpose and thus holding the bottom where scoured, at 1. feet below the low water plane. Me recommend that scour be permitted to that depth as far across the opening as it ma v occur and that no stone be tipped above that level, if scour progresses across the opening down to that depth and i.. then checked bv stone tipped for the purpose we consider that the opening will then allow nearly the same volume of water to enter the Lagoon as formerly. Any diminution

oi that volume will be prejudicial to the maintenance of the approach channel outside the Moles. It will be seen from the foregoing that we consider that to check or attempt to regulate the volume of tidal water by means oi a half tide wall would be disastrous to the approach channel outside the Moles and that sluice gates in such wall would not materially relieve the situ ation produced. Wo therefore condemn the proposal on the general grounds indicated. The temporary closing of the bridge opening would Im dilate deepening operations between tin l Moles, hut the cost of so doing and of the subsequent necessary removal of the barrier would outweigh the advantage. Either a stone bank or steel sheet piling would cost a very large num. NEW ENTRANCE TO INNER HARBOUR. Altep considering this question wo express the opinion that any advantage a new entrance might possess would not offset its very groat cost. Its advantages would be two. first on those occasions when a considerable swell irom E. and S.E. was running a vessel would have such swell more directly behind her, ami secondly any range entering the Inner Harbour through it would spend itself largely be lore reaching the berthage. Its drawbacks are, first, its great cost, secondly, it would admit a greater range between the Moles, and thirdly, its line oi direction would bring a vessel to pass nearer to two dangers, viz., the Auckland and Pania Rocks. The last two drawbacks we do not deem prohibitive, but they exist. Our opinion as to the cost rests on the facts that the new channel through the Spit would mean a large and costly cutting, that a large basin in the Harbour would be required for vessels'to turn in and get to the Quay and that two very substantial -Moles outside would be necessary, each of which should extend out to a depth of about 18 feet at L.W .S. Resumption of land would be a further factor. The present entrance admits less Tange between the Moles than the suggested one would, and if improved as we proposed would afford safe entrance for vessels, OUTER HARBOUR. The completion of the Outer Harbour to provide accommodation for 4 ocean liners and other vessels that require berthage involves the following works. 1. The extension of the Breakwater to an adequate length. 2. The construction of a Mole to shut out wave movement from the harbour. 3. 'The reclamation of an area within the harbour, retained by a rubble wall. 4. Dredging part of the enclosed area to a suitable depth and 5. The provision of one or two piers with sheds. The Secretary’s letter ot May 12. 1925, conveyed the Board’s desire that we should interpret our instructions referring to the desired accommodation here to mean that we should plan and estimate for one pier in addition to the existing pier and alternatively lor two piers, with an adequate dredged basin in each case. BREAKWATER EXTENSION. The length the Breakwater needs to bo extended is governed by the diameter of th 0 swinging circle a vessel needs to turn in between the entrance and the end of the piers. In discussing this matter ol the swinging circle with the Harbour Master Captain White-Parsons. 8.N.K., he expressed his entire agreement with the area proposed and shown on our plan. We have decided on a length therefore of 1550 leet from the end of the top of the present Breakwatei. We have fully discussed its direction in our 1912 Report, and propose the same direction as then recommended. e recommend that the type section lov the extension should be the same as that of the- existing Breakwater. I he latter appears to have stood the exposure w ell, without any serious injury from wave stroke, and the Board possesses the cranes, etc., used in its construction which we understand are in good order. Although from its direction the extension may not be subject to quite as severe a wave stroke as the outer portion of the existing work vet we consider the same sized section’ desirable. This is shown on the drawing accompanying showing type sections, etc. It consists of a rubble foundation brought up to a level of about 19 feet below low water on which concrete blocks am built up in a rectangular section 25 feet wide io a bniabt of 30 feet, i.e., to 6 foot above H.W.S. with a wave breaking apron of large stone and concrete blocks on its seaward side. MOLE. The Mole shown on the accompanying plan is indispensable to provide berthage free from material wave motion. In locating it we have placed its root so as to afford as much room lor future extension as possible without increasing its length unduly, it will be 3800 feet long, and will consist of a mound of rubble stone ol Irom half to one ton up to L.W. level with a top and an outer skin of stone of from 3 to 10 tons. The mole will be 15 feet wide on top with side slopes ol 1| to 1, and will be 6 feet above H.W.S. The opening between its extremity and the Breakwater is 600 feet wide, hut the portion of the Auckland Rock inside the Breakwater will reduce the effective width of opening to 500 feet. Wo propose that so much of the Auckland Rock be removed as will leave an effective opening of 600 feet. RECLAMATION. The reclamation shown on plan i> required for a working area on the pier approach. For the first new pier the reclaimed area would be about acres, and with a second new pier a further 4-6/10 acres. It would be created by placing rubble irom the cliff to form a retaining bank and filling behind with quarry spoil Irom the same source, to a height ol 10 feel ■ above L.W.S. and graded up to meet pier deck level. DREDGING. The borings have shown that the strata consists almost entirely of silt in the outermost portion and oi soft papa in the innermost portion of the area that would have to be dredged to provide a low water depth ol 31 I cot with 35 feet in the berthage. The socalled “papa” as il exists here appears to be a more or less tough > lay-like material of blue-grey colour, concerning which Mr. Pengelly. the ofßoer-in-charge of the boring operations states that it would present no difficulty in dredging or m driving piles. Contrary to the information afforded us in 1912. there appears to bo no rock in the area worth consideration, save at its extreme western edge, and at two small patches, one of which was formerly partly removed. This patch lies off the N.W. corner of the Glasgow wharf and carried a depth of 23 fpot which was lowered to 25 feet at. L.VV.Ss. The other lies to the Eastward of the Glasgow Wharf and car- | ries 23 feet over it at L.W. It is on the edge ol the area proposed to be dredged. It is possible that another pinnacle natch or two might bn encountered in dredging. biß if so their area would be small, and with the plant ve ni’opn««. tlimr removal offers no difficulty Tha OrMeing Plant recommended I nr»nsisf«s of a epneroing twin screw ‘ i bunkot lionnor drodgnr carrvirg abon 4 ' | Q OO toil's in its bnnrpr of s+n rn wn ]| ? i tvnn nrpfprnhlv. and ahln to drod"o tn 1 a depth of 45 feet below water level.

Wo have allowed in our estimates for the purchase of a new uredger of the < foregoing type. If, however, the ; Board could hire a Dredger of that i type or a period of about 3 years al a cost that wojild compare favourably with i ho net cost, of a new Dredg'.-r subsequently sold, then such course would be advisable, or if it could pur- . chase a second-hand one in good condition at a favourable price, we com- : mend that it do so. For dealing with Dm small rock patches, two Ingersoll-Rand 4.1-inch steam rock drills could be niciinted on the side of the dredger for dril'ing th • 1 rock nreliminarv to blasting if and then dredging if up. Blasting gelatin 1 fired with plectric detonators is rccn">nionded. The same means ban bp used for cutting back tbo Auckland Rock, a work, however, which could b'- left ever until fbc ofher works iverp more m - less completed. As wc have no detail su’-’-p” cf this rock wp have been compelled io a< c um(» th*' nunntities. involved in cutting it back to tbo extent shown in plan. i 0., to increase the not width of entrance from 500 io 600 loot. However, the area ol such is not large, and anv error in our assumed miantifies would m t nffo'-t tbo total estimates materially. AY > consider wo have very liberal allowances in nnr estimates foi all rock that needs removal. PIERS. 33ie piers shown on plan are similar Each would be 550 feet long by 178 lorn wid° and consist of a centre fill with a reinforce d concrete breast wharl on each side. The reinforcement to be designed for a loading of 7 cwt. per square foot. This will permit of railway rolling stock using the pier it desired; room for i wo tracks on each side is provided and in the centre between the sheds a roadway for vehicles is shown. ESTIMATES OR COST. WITH ONE PIER. Breakwater extension 1550 lin. ft. ... £209758 Mole 38110 lin. It ... 49690 Reclamation, 3i acres 3985 Pier 550 ft. bv 178 ft. 87261 Sheds, 350 ft. by 35ft. on each side 7350 Shed 200 ft. by 60ft. on reclamation . . 1200 Dredging to 31ft. at L.W.S 308.38 £393082 Engineering and contingencies 5% .. 19651 Twin Screw SOO ton hopper dredger 65000 2 steam rock drills 500 Removal 2 rocky patches in dredging I area. Allow 3000 c. yards at 20 - .. . 3000 Removal part of Auckland Rock. Allow 6000 c. yds. at 20 6000 £187236 ESTIMATES OF COST. WITH TWO PIERS—AS SHOWN ON PLAN. Breakwater Extension £209758 Mole 49690 IL lamaticu I 10 acres 9226 2 piers each 550 ft. x 178 ft 17(522 Sheds 50ft. x 35ft. on each side of each pier 11700 Sheds 2 on reclamation. each 200 ft. by 60ft. .. 8100 Dredging ... 44713 £511009 Engineering and contlngen536559 Dredger twin screw* 800 ton bucket hopper 650tH> 2 steam rock drills ; Removal 2 patches rock in dredged area. Allow 3000 c yards at 20 - 3000 Removal part of Auckland Rock. Allow 6000 c yds. at 20/- 6000 Total cost £611059

O.i cumpii tion of the dredging the dredger CGuld probably be sold tor ai least half the cost price, it being oi a type that is generally serviceable ana aired by harbour engineers. in connecticn with the whole of the estimates submitted with this report we desire to state (tint they have liad our most careful consideration. Costs have increased very largely sin e 1912, an.l by wav of illustration we mention that Dredging Costs have increased between 1912 and 1921 98 per cent, in \ iCtnria, 87 per cent, to i/6 per rent, in .Xew Eolith W ales, ami 98 pt i- cent, to 129 pe. cent, in Queensland. Wharf construction in Queensland and New South Wales has increased 75 pur cent, to 96 per cent., and shod construction a similar amount. The items comprised in the power hi use we recommended have mertased 75 per cent, to 260 per cent. Coal at Napier is taken at 48,'- per ton as against 28/- in 1912. The estimate for liar Dredger for the Inner .Harbour scheme and ol the Bucket Hopper Dredger for the Outer Harbour work an? based on actual tenders received from Great Britain and the Continent during 1921 ior similar dredgers. SOURCE OF STONE SUPPLY. I Our recommendation in 1912 that 1 sources of stone supply be explored fully docs not appear to have been acted upon, and wo therefore devoted what time we could to this ouestioi.. Through the courtesy of the Resident Enginoe*- P.V\ . Dept, and » f Mr. George Nelson we were enabled to see several localities from which stone that would probably prove good enough night be obtained; 1 he heavier, harder roi ks do not appear to occur in the district. The localities are Pel ano. about 7 miles; Waipunua, about ‘-’0 miks distant on the rnilwav towardsGisborne: and Oninhu. about 10 m'los . s'-niher’v from ?\api< r: Paki Paki. i l7 miles-from Nayier on the rnilwav io Palmerston appeared to bn I the most promising, but as we had no‘ i hoard of it prior to out- departure and ' onlv saw it in passing, we mav 1--mistaken. I The cliffs on Scindo Island have, we ' understand, afforded all tbo <to”n i hitherto used in the Broakwai r four datinns and apron, anti doubtless will afford much more. Tn our estimates Iwe have considered that the rubble I f'-undation for ilm Breakwater exlon- ; sion, the jiier fills, and the stone for ! the Mole »-an ho got from this source the spoil being utilised for reclama- • tion The large stone lor the Break i water apron and for the Inner Harj hour Mole extensions to be procure'l j from Petane. W aipnnga or from Pal i , EXTRA COST OF MAINTENANCE. OVER THE PRESENT COST CP

EACH PRUPOSAL. We estimate that th -annual (■)<' of niainlenanct. after completion <>l the new works for tin Inner Jlariionr scheme as proposed in this repo/t would be lor dredging and for upkeep of t In- quay, hods. etc.. U i <i. mid that the annual cost of maintenance after completion of the new works lor the Breakwater Harbour as pr<ipo < . in this report would be C 3710. RECOMMENDATION. We arc asked to idvi>c ti.e Board which of the two harbour i hemes we recommend for exocut i-n. Shortly after submitting onr rejiort of J 912 wo suggested, in reply to an inquiry irom the Board, that the Inner H “ hour appeared to offer a better pro - poet for successful i-xecuticn than the Outer Harbour; an opinicti based mi the information then supniie.l t<« •; respecting the ->trtita in flip bottom ;J the Outer Tlarboiir. viz... that a lai < area ol ro<J< existed (hero, which woti'd have to be removed. The Lom- a; ■ <■>. of the strata which ha- been made th - year liy boring lias sliiwn that th rock formerly supposed i" be th. e I does'not exist, and that ’he an a. v< h I the exception of a b-w -mall patch’ ■ down to 35 feet l>e!ow L.W.B. i- fr -• I from rock. The strata, in the opinion of the officer in charge of tlm Ir.rnig I operations, will present no diffi' i::tv n: i dredging it or in driving piles into it. I This survey has shown that what we I considered to ho a vorv serio.us ohio -- tion to the successful execution ol th.. - Outer Harbour proposals does not exht in fact.

We are of opinion that the adoption of the Outer Harbour scheme with one pier which with the Glasgow Wharf will afford accommodation for four ocean liners is to be preferred, and recommended accordingly. Briefly, our recommendation is based on the smaller initial capital outlay required for the Outer Harbour, whilst the difference in the estimated annual maintenance for the two schemes would represent, if capitalised. « furtner large difference. The maintenance of the Outer Har hour would require no dredging, save a little minor work at lengthy intervals to clean up the berthage, whilst the Inner Harbour would require the keeping in continuous commission a large dredger with all that so doing involves. From the point of view of the public convenience there does not appear to be any very material difference between the two harbours; this factor, however should nut be considered a dominating one were it otherwise. The Outer Harbour possesses an advantage from a ship’s point of view in as much as it would be easier to enter during bad weather. With this report we submit a plan showing the proposed works in outline at the Inner and Ouier Harbours, a drawing showing typo sections of the various works considered, and a plan showing the strata at both harbours as determined bv the borings taken. In conclusion, we desire to express our obligations to Mr. J. P. Kenny. Secretary, and to Captain WhiteParsons. R.N.8., Harbour Master, who assisted us materially in every possible way. also to Mr. O. D. Kennedy. M.lnst.C.E.. and to Mr. George Nelson, M.1.M.E.. for information and for the courtesies extended to us. We have the honour to be. Sir, Respectfully vours. E. A. CULLEN. M.lnst.C.E. T. W. KI-IJ.E. M.lnst.C.E.