TAIHAPE BOROUGH COUNCIL

Taihape Daily Times, Volume XII, Issue 3655, 17 December 1920, Page 4

TAIHAPE BOROUGH COUNCIL

MAIN STREET IMPROVEMENTS., CONSULTING ENGINEER'S REPORT. The consulting engineer, Mr A G. Walker, reported to the JBorougn Council as follows:! — I have the honour in compliance with your instructions of the 13th ultimo to submit herewith the result of my investigations duiring my recent visit to Taihape in connection with the proposed improvement of Main Street.

EXISTING CARRIAGEWAY. As you aTe aware, I made a pergonal examination over the whole of the proposed work and investigated the depth and character of the existing carriageway foundations. As the result of my investigations and a perusal of the permaanent level plans, I ariT reluctantly """compelled to advise you that, the existing carriageway for an aveirage width of 50ft. from near Kuku Street to Huia Street will require to be reformed on new foundations.

I am hopeful that advantag could have been taken for the most part of the existing consolidted roadway, but find that on account of the excessive camber, it will not be practicable to Ho this.

I have carefully looked into the question of the proposed levels and find that they cannot be improved on, as they represent the minimum amount of regrading which in my opinion should be done. The laying of the storm water, drain and connections has also disturbed a good deal of the carriageway and special care must be taken to ensure that the filling' material becomes thoroughly "consolidated. After ascertaining the nature of the subsoil, I formed the opinion that it will be necessary to deal with the new foundation area in a very thorough manner. NEW FOUNDATION WORK. The exact routine to be adopted in carrying out the work will depend on local traffic conditions and other considerations which have to be taken into account when the work is in hand. Such matters as the point of commencement and the width to bo dealt with at one time can only be decided on the spot. ' The total thickness of foundation and paving course should not be less than -2in. After the existing material has been taken off, the subgrade should be formed to the tru'a contour and grade of the finished carriageway.

A layer of furnace ashes consolidated to Sin. thick, should be laid dir'ect onto -the subgrade after same has been well'rolled. The chief object of this layeir is to prevent the clay rising into the foundation material, and ft also provides a medium whereby any ground water may be disposed of . The fact must hot be overlooked that it saves an equivalent amount of broken material, and if it is readily obtainable at reasonable price. I have no hesitation in strongly' recommending its use, ' as" experience shows that it is highly effective in clay areas. After this layer has "been roiled and all irregularities dealt with, a broken foundation 6in. thick should be laid in layers and thoroughly blinded, watered and rolled. The top of this should finish about 2-Un. below the finished surface of carriage way, and before any paving is laid 1 , maximum consolidation must have taken place. In order to assist consolidation, ordinary vehicular traffic should be turned onto the new foundation. This will assist in discovering any inherent defects which can be dealt with before the paving is laid. •The material from the existing carriageway can be re-used provided it is free from excess clay and also has all stones ovdr 2|in cube removed. Any plums, etc., if of suitable quality can be passed through the crusher If this procedure is adopted, very little * new material will be required. Should ther'e be any shortage, however, this can be made up by crushing some of the good quality from the Council's pit The points which I wish to stress aire that the foundation material must be thoroughly consolidated, the interstices of all stones well filled, 1 and the surface finished true to the contour and graiTc of the finished carriageway When this condition is reached then will b'-? the time to take in I hand the layintr of the paving. PAVING According to the specifications it is proposed to lay a 3in consolidated layer of Tar Macadam, distilled tar being the binding medium. The surface is to be finished off with a bituminous binder

Apart from the fact that the tar will in time dry "out on""the stone, I also know from expedience" how advisable it is to keep tar and bitumen well apart. I have no hesitation in

stating that I cannot recommend the Council to lay down the paying as specified I agree that a 3in consolidated layer is necessary, but a much more satisfactory and durable job will be obtained by using a bitumen of 40 to 50 penetration for mixing with the stone, and a bitumen of 60 to 70 penetration for finishing off on the surface.

BITUMENS There are several good grades of bitumen or asphalt obtainable through local agents, .and the following information "Is submitted for your Council's guidance: (1) Mexphalte" Bitumen can be imported through fMessrs Kidd, Garrett Ltd., Little Queen St, Auckland The manufacture and sale of this article is controlled by the AngloMexican Products Co, Ltd, London, j There are two American Bitumens j which are also in general use. (2) '"Union Asphalt" from Messrs Ellis and Co., High Street, Auckland (3) "Sogony" Asphalt from Mes- j srs John Chambers and Son, | Ltd, Auckland and Wellington. i All the above are practically of "the ! same quality and it is only necessary when obtaining quotes to mention the penetration required.The material is ordered by quoting the penetration number, and in order* to avoid confusion when the, work is in hand it is necessary that this number be clearly marked on all barrels. About 15 gallons of bitumen will he required per cubic yard .of mixed material or about 1* gallons per square yard of finished roadway. The material is -mixed in the same manner as for tar macadam but it must be laid hot and well rolled to finished surface while in that" condition. | The metal to be used for the paving work should be clean and 'tough. The quality of the Belmont metal you have in stock is quite satisfactory, but it should be broken to pass, a 3Jin ring and have all dust screened out. SHINGLE The material for finishing off on the surface:, must be of the best quality and as, the result of inspection of the Rangitikei River shingle at Utiku, I have- no hesitation, in recommending its use It, will be necessary to pass the shingle through a 5-Bin. mesh screen; which work can best be done at the river banks., MATERIAL EX COUNCIL'S PIT. The material in this pit appears to vary somewhat in quality. The majority of it is covered with a thin layer of -dust and it would therefore not be advisable to use any of this class for the paving work The large boulders, however, which are of a tough nature and clean on the surface arc best for this purpose. For side streets and general foundation work the better quality boulders of all sizes should be passed through the crusher, as I do not agree with the practice of using this class of material for road work unless crushed. I therefore recommend the Council to continue the use of the crusher for this purpose, and as soon " as* power is available to move it to thfe pit. PLANT With regard to the mixing plant, it is possible to" mix the material without a machine although ft would be more economical and a more satisfactory job made if this was pro-, vided. In view of the fact that the area to be dealt with is not of very large extent, and also that no further work is proposed after Main Street and Tui Street are completed, the expense of purchasing a macnine hardly seems warranted I would suggesT'that the Council enclf r ours to hire one. I understand that the Hastings Borough Council have a suitable machine, but if this cannot be hired other methods can. be adopted. This is *a matter, however, which can be &t aplater date? COMMENCEMENT OP WORK The work of permanently improving' the Western footpath and the Reforming of carriageway should be put in hand without delay There are several facts, however, which soem to point to the advisability qf deferring the paving work until early in next season. Firstly the bitumen will have to be imported as no stocks are carried in New Zealand; secondly, facilities I have to be provided for drying the Btone and mixing the "Bitumen with eamcj and thirdly, time must be given for the foundation to become consolidated Taking all these into consideration, it hardly seems possible for your Council to be in si position to put in hand any large amount of paving work until after the winter Decision on this point should be deferred until matters progress further- :" ; "HJ

I have made no special reference to Tui Street as tirco did not permit of my making a close inspection of this work. I have, howefM, set a sum down in the estimates' which will in ny opinion cover the cost of same. ESTIMATES. • I estimate the approximate cost of the proposed work to be as follows: MAIN STREET.—Reformation df carriage way (Wcka Street to "Gretna"); Bituminous macadam paving (Kuku Street to "Gretna"), £4700. 10 per cent supervision and contingencies, £470. Total £5170. TUI STREET. —> Reforniaticm ; of Carriageway and laying of Bituminous macadam (Main Street to Railway Station), £773; 10 per cent supervision and contingencies, £77. Total £BSO. CONCLUSION. In conclusion I have to extend my hearty thanks to-His Worship the Mayor, Or. Reid, the Town Clerk, and the Foreman of Works, for the courtesy shown and information supplied during my investigation of the pro* posals. (Signed) A. GREVILLE WALKER, Assoc. M. Inst. C.E, (Lontfon), Consulting Engineer. Cr. Davies considered the report a most comprehensive one, and thought that Councillors should have*.an opportunity of considering it in detail. He moved that consideration of the* report be held ovex. Cr. Fookes in seconding the motion concurred in this view, and the motion was carried.