ENGINEERS DIFFER

Pukekohe & Waiuku Times, Volume 8, Issue 467, 26 September 1919, Page 2

ENGINEERS DIFFER

Mr Lopdell Picks up t Gauntlet

Slashing Rejoinders

Under yesterday's date, Mr W. J, Lopde l ', engineer to the Manukau County Council, writes as follows to the Editor of the Times: Siii,—As the " Franklin and Pukekohe Times" has such a numerous circulation in the Manukau County, kindly allow me space to reply to an effusion appearing in the " N Z Herald" on the 22nd inst, on the above subject, from the pen of Mr F. Shannon, Engineer to the Matamata County. Mr Shannon states: " I make no apology for any comments 1 am about to make on t'ae subject of theManukau County Loan proposals, as I assume that other ratepayers in the County have received a circular letter from the County Engineer eimilar to the one before me."

It may be of interest to my ratepayers when I state that I have perused the roll of the Mangere riding (the only riding interested in the £30,000 Loan for tarring roads) and I find that Mr Shannon is not a ratepayer in that riding. It is then apparent that professional etiquette is not Mr Shannon's strong point. It is with reluctance that I am compelled to make comparisons in the relative merits of tar v. concrete, but owing to the mis-statements appearing in Mr Shannon's letter, also in his report printed and circulated in June, 1919, on concrete roads. I am, in fairness to the material I propose using, justified in making a few comparisons. Mr Shannon's letter is practically a copy of his report above referred to, and his report is a re-print of the American Engineering Conferences, hence it will be found that there is nothing original in them; besides, the figures quoted by Mr Shannon are entirely applicable to America, and will not work out in practice, as I will prove, in this country. Mr Shannon, in bis report, says the cost of a concrete road per mile is from) £2500 to £3,000. Now, Sir, I have followed this class of road making very closely, and I find the cost per square yard is from 10s fid to 14s 6d, this then works out on a 15 feet wide road at £4,620 on a 10a 6d basis. As we have 27 miles of roads to treat in the Mangere riding, and assuming this width to be only 15 feet wide, whereas they would average over 18 feet, we would require a loan of £124,740. I am very much afraid, unless I had the assistance of such an able exponent on concrete as Mr Shannon, I would have little chance of piloting such a loan to a successful issue. Mr Shannon says that the tar macadam road is costly to construct and expensive to maintain! He further states that it is only 25 per cent cheaper than concrete If he were to have said 73 per cent cheaper he would have been nearer the mark. As we have 27 miles to treat with tar on a £30,000 loan, I will leave it to the ratepayers to judge if Mr Shannon's figures can be relied upon. Tar macadam works out at 3s 7d per cubic ye'd, tar grouting at Is 9tl, tar sealing at Is 2d, providing for two coat-; annual upkeep at about £6O per mile per annum—not £IBO, as Kt'ted by Mr Shannon. Mr Shannon again shows his limitations on the subject of stating that a tarred road after being down 12 or 18 months, if picked up will be found to be quito dry and granulous, having noadheive properties, rendering it no better than the ordinary water bound macadam. Now, Sir, let me quote you what the Commissioner of Highways in America has to say on this subject at a conference held in Washington, • U.S.A 1917. ' A Tar Macedam road laid down 1 in Washington 44 years ago stands as a morument to the value of proper treatment of road tars. Recently sections of this road were cut out for the purpose of examination and report. The mineral aggregate was found to be exceedingly well bonded, and the tar binder still quite lively, giving off a strong odour of coal tar." "Vhile we have no »oads in Now Zealand which have been down 11 years, we have m»ny 12 and 15 years old, and the experience of those of us who have not a mote in our eye, coincide with the Commissioner in his report as sat'd above. I have cut through roada which haye been down several yars, and have seen the tar stick to the picks. After having hsd eight years' practical experieuce amogst tar in the Taranaki Province, where I raised a £GO,OOO loan in the Waimate West County, I have since had the satisfaction of seeing the work carried out within the estimate.

I would recommend that Mr Shannon should uke a trip to that province which may broaden the vision of my brother engineer, and enable him to see virtues in road making material than concrete.

Can Mr Shannon tell me of one concrete road in the Dominion two years old, which has not been treated with some bituminous t jp-dressing ? I can inform my fiiend of many streets and roads that have been so treated after one year. I caa go further and refer him to a street in Wanganui once laid down in concrete—to day we find it lifted and replaced with tar macadam. I do not wish to enlarge further on the merits of tar as against concrete, but will conclude by »ju iting you from the last three annual reports of the Commissioner of Highways (C. J. Bennett), wherein be says:" I strongly favour concrete as a foundation, but after fiv.) years it is suitable for paving blocks or bituminous covering." If Mr Shannon were to confine his remarks to concrete as a foundation he would have many followers, but when he speaks of it as a suitable road to outlive a loan of 36$ years, lam afraid he must claim to have the field to himself.

What stronger proof can we have of the success of tarred roads in Taranaki and their effect upon the rate, than to note that after 12 years experience we find to-day that the Taranaki County is raising a £60,000 loan, to follow in the same lines as their neighbouiing counties who have given them a lead ? W. J. Lopdeix, County Engineer, Mftnukau County Council.