SIR JOHN COODE’S REPORT ON PATEA HARBOR.

Patea Mail, Volume V, Issue 469, 22 October 1879, Page 2

SIR JOHN COODE’S REPORT ON PATEA HARBOR.

(Continued from last issue.) GUIDE PIER. The guide pier would be 500 feet in length, commencing at the point F, and terminating at G, so as to give a low water channel 200 feet in width. It would be curved to run parallel to the proposed eastern margin of the river, and, in conjunction with the embankment and the face of the eastern end of the head, would form an admirable wave-basin, wherein waves entering between the' pier heads during gales would, to a considerable extent, bs dissipated and absorbed, tints materially reducing the disturbance or undulation in the river. It will be observed that the top of the' close sheeting of the guide pier is at high water level) and corresponds with the upper face of the west pier. This level for the top of the solid or training structures would admit of the free run, both into and out from the riVer, of high tides or of extraordinary floods, rising above the' level of ordinary springs. To prevent the sand from being carried over into the space enclosed within the two piers, it might possibly be desirable to slope down the landward end of the west pier from the level of the surface of the depot to the top of the work, as shown on drawing No. 2. TRAINING SHEETING, AND PLANTING.

Mr Thomson has alluded to a constant stream of sand being carried into the river from the sand hills during westerly winds, which might bo prevented, by planting. I would recommend that this should bo done at the proper season with seeds of the arundo arenaria, or some other species of bent grass adapted to the climate and suitable for the purpose. I have considered it desirable' to'provide in the' design for the construction ot two K'chlf iiJo olicoimg*j OUO Oil either side of the river, commencing on the right bank at the point H and terminating at I, being a length of 1,480 feet. An opening, of 100 feet in width, would be found between the ends of the sheeting and guide pier,- through which the tidal water at the rear of the former, when below its level, may readily pass. On the left bank the training sheeting would commence at the point K, and be carried downwards to L (being a length of 870 feet), parallel to the training work on the right bank, so as to form a low water channel of 200 feet, which is the proper width. From L seawards, the eastern foreshore would form a natural training bank, rendering an artificial face unnecessary. NEW CHANNEL TO BE DREDGED. The foregoing works are those which may bo described as strictly appertaining to the improvement of the entrance. Closely following, however, upon the increased navigable depth in the outfall, the necessity would arise for an equivalent increase of depth in the river, hence I have stated in estimate, item No. 8, the cost of dredging a channel from the sea to the town, so as to give a depth of 8 feet at low water, equal to at least 14 feet at high water of spring tides, which would suffice for the full utilization for navigation purposes, of the high water depth of about 1G feet in the entrance, when the worke are carried to the extent contemplated by the red tint on drawing. NEW WHARF. At the river end of Essex-street, as marked on the plan, near the existing short jetty, on the right bank of the river, I propose to form a wharf of 300 feet in length, of open timber piling, adapted for the berthage of vessels along either face, with their heads pointing up stream. I have also dotted an extension of this wharf, which might be undertaken hereafter. Along this concave site the maintenance of deep water might be depended upon, and the space between the wharf and the shore could be filled so as to form warehouse plots and standage spaces ; although this could only be done at a sacrifice of the berthage along the inner face. SWINGING BASIN. Abreast of the extension of this wharf, I have indicated a site for a swinging basul, which should be dredged to the full depth in the channel, so that vessels might here be enabled to turn preparatory to going to sea. ALTERNATIVE POSITION FOR WHARF. Along the left bank of the river, and below the bridge, I have dotted an alternative position for the wharf, _ together with an approach from the main road to Wellington, and a bridge crossing the small kloof. Along this line, also, the deep water would be self-maintaining. It will he for the authorities to determine on Which of the two sites the Wharf should be constructed in the first instance ; the cost will be practically the same in either case. ESTIMATES’. I estimate the cost of the works hereinbefore recommended, as follows, viz ; For the construction of the piers, and training sheeting necessarry for the formation of a depth in the entrampe of 8 feet at low water, and at least 14 feet at high water of spring tides —

No. I.—East Pier, from A, to B on drawing No. 1, with foot and depot, £47,370. No. 2.—West Pier; including root and depot; front the shore to point D; £80,790. No. 3.—Guide Pier* from F to G; with embankment to form wave - basin, £6,030. No. 4.—Ha'f-tide training sbeetirig from H to I, on the right bank of the river; and from K to L oil the left bank; £10,600. Total cost for the above described works completed to the points marked D and B, £144,790. For the prolongation of the east and west piers to the extent requisite to afford a depth of 10 feet at low water, and at least lo feet at high Water of spring tides— No. 5 —Prolongation of East Pier from B to C on drawing No. 1, £17,120. No. 6.—Prolongation of West Pier from D to E on drawing No. 1, £35,380. “ Total, £52,500. Total coat of works recommended in connection with the improvement of the entrance —£197,290. No. 7. —Forming a wharf with approach to same at Carlyle, as shown on drawing No. 1, £8,450. No. B.—-Dredging a navigable channel of not less than 8 feet at low water, and 14 feet at high water, between the proposed wharf and the sea, including the purchase of the requisite dredging plant, £30,200. The above estimates include a sufficient margin to cover contingencies and all charges connected with the execution of the works. They have been arrived at hy adopting the rates received from the colony (as far as they were applicable), and applying them to the quantities of work of different classes, calculated from detail drawings, the essential portions of which are shown on the accompanying drawing No. 2. The amounts named will _ doubtless appear high, but when it is considered that the local rates, so far as regards labor, are more than double those which prevail _in England ;■ and also that cement, which forms an important item of expenditure, when delivered at works would cost about three' times as much ; and further, that other materials range at high rates—it will be evident that any works which may be undertaken' at Patea must of necessity involte an unusually large outlay compared with their extent. _, Tho sections, whilst they provide for substantial works* are*l believe* of the least exp'ensive'descnplion which can be adopted to fulfil the requirements of the case as regards sea-stroke and scour* and at the same thrie to ensure permanence. Nor would works of a less comprehensive character than those' recommended suffice to accomplish the object in view, more particulary with regard to the attainment of the requisite depth in the entrance. With reference to this latter point, I may observe that, although when' the works reach a depth of 8 feet at low water, viz., at the points B and D on drawing No. 1, considerable benefits will accrue from the entrance having been fixed* thus ensuring the passage of the whole of tho tidal and fresh waters over a duly proportioned and defined channel ; nevertheless they should bo continued to the full extent shown by the rod tint, viz., to 0 arid E respectively, these being regarded as the terminal points of the first stage of the cast and west piers, thereby a ! permanent depth 1 in the entrance of 10 feet at low water, or not less than 16' feet at high water of spring tides, might be relied on;

The execution of fhe piers' arid training sheeting contemplated in the expenditure of £197,290, would occupy about eight years ; hence the outlay would be distributed over that period, tho annual sums required during the first two or three years' being relatively more than afterwards.

If the funds necessary for the execution of the two piers, at least to the points B and D, say, £130,000, bo not forthcoming —defening for a time the guide pier and training sheeting—l see no alternative but to postpone the improvement of the entrance until the necessary means can be provided for accomplishing the woik in a proper and alfectual manner. An exception may be taken to the use of wood to such a large extent in the proposed structures. In the case of the guide piers and training sheeting, if it should be found that rubble can be obtained of a suitable character, and in sufficient quantities for the works, at a cost which would result in a saving as compared with the outlay required for the piling, then I would recommend that these works (i.e., the guide pier from F to G, and the training banks from' H to I and K to L, respectively) should consist of rubble stone in the form of mounds, their faces being left rough and without pitching. Mr' Thomson, in his reply to one of my queries, has stated that rubble of a medium size could be delivered on the south-east side of the river entrance at 5s per cubic yard. Upon this price I have based my estimate of the cost of filling the east pier between the piled faces with a hearting of rubble stone. For the piers, the use of sheet piling to the extent shown on drawing No. 2 is absolutely necessary, in order to provide for abnormal scour after completion ; and if care be exercised in the selection of the totara, more particularly with respect to its being free from sapwood, there is every reason to anticipate that it will bo found a satisfactory material. The use of concrete for the west [east] pier would increase the cost of that structure to the extent of £29,000 beyond the sura named in item No. 1 of the estimates. REMOVAL OF OBSTRUCTIONS, There can be no question as to the desirability of removing the obstructions which now exist to the free flow and ebb of the river currents, more particularly at the eel-weirs, to which r<j%rence has previously been made. The removal-of these weirs will undoubtedly increase the capacity of the tidal compartment, by lowering the low water, and raising the high water in the upper reaches of the river. Numerous snags exist in the course of the river above the bridge, as pointed out by Mr Thomson the' removal of these obstructions is also very desirable, and will tend to improve the regimen of the river. FUTURE DIVERSION OF RIVER ABOVE THE BRIDGE. On drawing No. 1, I have indicated, by crossed red lines, a suggested diversion of the river course, immediately above the

bridge; in order tri obviate the two objectionable bcihls, and the cdusequent waste of current energy, to which t have previously referred; This diversion; although not absolutely essential, is nevertheless a \Vork to be kept in view, and when funds permit, should bo carried o'iit upon the lines laid down. BRIDGE ABUTMENT. ‘ I ilmierstand that one of the abutments df the bridge is b.-iilg und>-rmined, this shotild be examined, and, if need be, prontpt measures taken for securing the structure. In conclusion; I have to express my obligations to Mr Sherwood (the Chairman of the Harbor Board), to Mr Thomson (the Engineer), and Mr Wood (the Harbor Master); they, each and all, facilitated my inspection itl every possible way. To Mr Blackett my thanks are also due for his assistance at Patea, as at other New Zoalatuls ports visited by me.—l have. &c., (Sighed) John Goode.