“INTERNAL” CORRESPONDENCE

Dominion, Volume 19, Issue 155, 27 March 1926, Page 18

“INTERNAL” CORRESPONDENCE

MAIN HIGHWAYS BOARD AND CITY ENGINEER SOME SEVERE STRICTURES WERE THERE ERRORS IN ANALYSIS? About half an hour was devoted at Thursday's meeting of the local Highways Board to the question as to whether the correspondence between the engineer of the Main (Government) Highways Board and the city engineer of Wellington should be made available for publication.

The chairman (Mr. C. J. B. Norwood), took the view that when the correspondence was of an internal character, from one engineer to the other, “it should not be brought before the board, and should not be made available to the press for publication, for if it were understood that all letters so written were to be published there would not be that openness about them; they would be written/ in a more diplomatic manner, and not simply as one engineer to another. Mr. R. A. Wright said that he could only agree with the Mayor up to a point. He could scarcely accept the letters as being from one engineer to another. To him they were letters iron! one highways board to another, letters which might have been sent to the Town Clerk or Mayor; ami very important they were, for they said, in effect, that if certain things were not done they (the Main Highways Board) were not going to pay the subsidy. “There may be letters from one engineer to another/’ said Mr. Wright, “but when the writer speaks as from the Main Highways Board it became quite another matter. If the letters were only for the engineer they should Ire marked ‘private/ but when the writer mentions the withholding of the subsidy unless something was done that was not then being done, it becomes a vital matter to every member of the board. Such correspondence should be available to the board, and ho doubted whether it could be withhold. Eyen when considered in committee, the time came when the business done in committee hud to be confirmed, and after that I doubt very much whether it could be withheld from the public. I don’t think it can,” concluded Mr. Wright.t Mr. H. D. Bennett thought that more harm was bein'" done by the discussion than by the jiublication of the correspondence. His point was that there were matters that could be settled between the engineers .without being published in the press. Personally he did not cure if the correspondence was published. Mr. A. J. McCurdy pointed out that whilst tho Mayor was opposed to publication, it was at tho City Council that the only part of the correspondence already polished had been made available. The chairman: "Is that so?” Mr. McCurdy: "Yes, after the last meeting of the board, Councilor Monteith delved into the files, and quoted from one of the letters in open council. Mr. B. G. 11. Burn said Hint Mr. Monteith had got wind of something, and it was something which had surprised most of the members of tho board. "If you do not wish thinlgs to get out,” said Mr. Burn, “cut them out in committee; don’t let them go on to tho council at all. 1 am on several committees, I know how things are ■worked!” It was decided to held the question of the correspondence over. THE CORRESPONDENCE IN DISPUTE "GRADING MOST UNSATISFACTORY.” ' ’& The correspondence referred to in the foregoing discussion is as follows:— “Public Works Department, Wellington, January 11, 192 G. "Re Wellington-Napier, via WairarapaUpper Hutt Town Board Section. •

“Dear Sir, —It is realised that with a new plant of a different typo tho officers of your staff are bound to have difficulty in comjilying with the specifications, but sufficient tin'ie has now elapsed and enough work done to enable those difficulties to be surmounted, so that from now on the specifications must be followed to the letter if any subsidy is to be pnid bv the Main Highways Board, when the necessary legislation' is put through. The work at present is unsatisfactory, and no Highways or other Government funds will be paid on any such unsatisfactory work, either already laid or to be laid. First of all. the sand being used in the wearing course is still deficient in material between 50 and 200 nicsh, although a sample taken on the 7th instant was somewhat belter)

"The grading of the aggregate of the base course was found to ho most unsatisfactory. The specification states that the base course mixture shall contain 60 per cent, to 80 per cent, of material ranging from Ijin. to 10, mesh, and 15 to 35 per cent, of material passing 10 mesh. Some batches ’ reaching the road on the 7th instant consisted almost entirely of Ilin, to 21in. metal, whilst other batches’ going into the base course wore almost entirely sand. The former batches naturally had a considerable surplus of bitumen. Upon investigating the conditions at the plant it was found that the specifications were being ignored in a flagrant manner. "It is clearly stated in the specifications that the coarse and fine aggregate for the asphaltic concrete mixture shall be measured separately and accurately,, either by weight or volume for each batch to bo mixed. It was found that the bitumen and aggregate for the base cQiirse were certainly weighed, but the coarse and fine aggregate, for the mixture were not being weighed separately. The grading of the base course was being left entirely to the men with the shovels at the elevator, and, moreover, it was very evident that these men were not carrying out their instructions. Even if the instructions were carried out to the letter, there is no guarance that the base course aggregate would bo up to specification because segregation of the different sizes of the material is very apt to occur during their passage through the drier. Some very much improved method of proportioning the aggregate for the base course will have to be devised if the spirit of the specified lion is to ho met. It was slated by the City Council officials that it was not practicable with this particular plant to obey the specification in detail as regards the accurate weighing of the different sizes of the material. If this is so, some alternative method may be proposed, provided the method of proportioning gives satisfactory and uniform results. The present methods are quite, unsatisfactory. “Three loads of base mixture were test-

cd for temperature during Mr. ’Tyndall's visit, and gave the following results:— nCJdeg. I'., 3t4dcg. I’., 28Gdeg. F. The limit provided in the specifications is 280 deg. to 325 deg. It will be seen that two of tho loads out of tho three were overheated. This fact was quite evident without tho use of thermometers from the blue fumes which came from the loads. While the lower limit of the above range of temperature suggested by the Citv Council is 280dcg. it would bo quite satisfactory, from the point of view of the Main Highways Board, if this limit was lowered to 250 deg. “Another unsatisfactory feature of tho work was the great frequency of hair cracks in the surface course prior to the application of the seal coat. These hair cracks are usually due to the creeping of tho soft surface mixture on loose material under rolling. They may be duo in this particular instance to use of rather a heavy roller for giving the material its initial compression. Wherever hail’ cracks show up, tho surface material should bo immediately loosened, reraked, and rerolled. In this way the hair cracks may be eliminated. No seal coat, however, uhould be put on any surface course from which the hair cracks have not been eliminated. In more severe cases of hair cracking the defective portions must bo cut out and replaced. Tf the hair cracking is very evidently due to a foundation defect, such" defect should bo remedied before replacing tho surface material. “It was also found that a section of road which had been condemned the previous day had been torn up after complete cooling had taken place and the. loose lumps of material had been used to form a portion of the extra base course ahead. This practice is not up- | proved. „ , , ~ , “Another feature of the work which was not quite satisfactory was that the base course was being allowed to get somewhat dirty with an accumulation of dust before the laying of the wearing course. An attempt should also be made to keep the foundation freer from loose material and dust before the laying of the base course. The failure, to do this also tends towards the production of hair cracks. “The time of mixing was found to be between 45 and 85 seconds. As previously mentioned, a elock or other timepiece should be installed without delay. "For your information I enclose a sheet showing the results of some.of tho tests which have so far been made.— Yours 'faithfully, (Sgd.) J. Hannah, District Engineer. “The Citv Engineer, “Wellington.” CITY ENGINEER IN REPLY. “February 11, 1926. “Mr. Hannah, “District Engineer, “Public Works Department, “Wellington, “Ro Paving Upper Hutt, Wellington- ■, Napier Main Hoad.

“Dear Sir,— Following the complaints made by your Department re t tlio unsatisfactory grading of materials constituting the aggregate of the top course of tho asphaltic concrete paving at Upper Mutt, a conference was held on February 10 between Messrs. McKenzie and Tyndall representing the Main Highways Board and Councillor 11. D. Bennett and myself, representing the Wellington City and Suburban Highways Board. At this conference it was decided to alter the present specification for working in connection with the top course from fine Topeka mix to coarse aggregate mix. “The following grading, I understand, is acceptable to tho Main Highways Board, and it is ’proposed to work on this grading of material immediately Metal passing H held on 10 mesh, 45 per cont. to 60 per cent.; sand passing 10 mesh held on 200, 30 per cent, to 45 per cent, (of this grading / percent to 12 per cent, to pass 80 mesh, retained on 200); filler passing 200 mesh, 5 per cent, to 7 per cent.; bitumen, 5 per cent, to 8 per cent. “It is anticipated that no difficulty will be experienced in obtaining the grading as above, with perhaps tho exception of tho 80-200 mesh. It is hoped to supply any deficiency in this grading from the dust mill now operating in the city. Further details of the metal gradings and sand gradings will be submitted v-hen further tests have been made. In my opinion as we arc now working on a coarser aggregate, it is advisable to reduce the working temperatures. Therefore, I have to submit for your approval the working temperature to bo from 225 <leg./o 2Sodeg. cn dcliverv. For the past six weeks we have been without the services of a testing officer. At the present tune we arc endeavouring to obtain the services of a tester, bint until tho appointment is made I should be grateful if arrangements could bo made for the Dominion analyst to test, on our behalf certain nuitcrifilSj more in<*s and filler dust gradings.—Yours faithfully (Signed) A. J. Paterson, city engineer.” STILL UNSATISFACTORY. "Public Works Department, •'Wellington, February 26, 1926. “Re Paving, Upptir Hutt, WellingtonNapier Main Road. ’ “Dear Sir,—Replying to yours of Febluary 11, on reading this letter again, I notice that there is a possibility of two meanings being taken out of the note ’re 7 per cent, to 12 per cent, to pass 80 mesh and to be retained on 200/ If these percentages refer to the total mix, they are satisfactory, but if they only refer to the sand content, then (hey cannot be regarded us satisfactory, as the amount should then be expressed somewhere between quarter and half of the total material passing a 10 mesh. Samples taken since the date of your letter still do not disclose a satisfactory grading of sand, and the material does not agree with the requirements agreeu upon by -Messrs. McKenzie and Tyndall nt the 'recent conference with you. Before tho specification submitted on Feb-

ruary 11 can bo approved, whichever way “the note referred to is interpreted, it ‘is necessary that the further details of the gradings promised in your third paragraph come to hand. In tho abscnco of this specification, and in the absence of any evidence that the material now being laid on the road is satisfactory, our letter of January 11 still stands; in fact, such evidence as we have indicates that the grading of the fine a"gregate is still unsatisfactory. With regard to the. temperature, though ■’2s deg. to 280 dog. may be satisfactory for tho base course. I am of the opinion that tho lower limit: for the upper course shou.’.d not fall ..below 250 dog.— Yours faithfully (Signed) J. Hannah, board’s representative. "A. J. Pato.rson, Esq.. “City Engineer. Wellington.” “WE CANNOT UNDERSTAND IT.” “March 1, 1920. “J. Hannah. Esq., “District Engineer. “Public AVorks Department, “Wellington. 'Die Paving, Upper Hutt: WellingtonNapier Main Road. “Dear Sir, —I am in receipt this day of your letter of the 26th ultimo and note that you make further complaint in connection with tho paving work on the Main Road, Upper Hutt. This complaint camo as a complete ■ surprise to me and my officers, and we confess we cannot understand it. As a result of the conference of the 10th ultimo it was clearly understood that certain specifications were to bo adopted and carried out as early as possible. These specifications were stated in writing in my letter of tho 11th ultimo and as there has been no comment from your Department to the contrary and as they wero verbally agreed to by the representatives of tho Main Highways Board, I presumed this specification was satisfactory to you. The specification referred to was put into operation at the Trentham plant three days after the conference, on the 13th ultimo.

“It is true that pending tho supply of filler dust and fine sand from the new dust mill plant then expected in tho course of a few days there was a danger, of this fine sand ingredient being short. This shortage, however, was regarded at the conference as being of less importance with the adoption of the now specification of the course aggregate type as against the late type of fine aggregate. As a matter of fact this was the principal factor in arriving nt an agreement in favour of that particular typo of specification. Tho grading of, the top course material sent out from the plant on and after the 13th ultimo was graded in accordance with the conclusions come to at the conference and was as follows: P.c. Metal passing Hin. hold on 10 mesh 52 Sand passing 10 mosh held on 200 mesh _■ 35 Filler passing 200 mesh 5 Bitumen a 8 100 “This grading you will note is in keeping with the specification referred to in my letter of the 11th ultimo. It was expected and the conference foresaw it that the fine sand would perhaps be on the low side as previously stilted, although it was allowed for in the specification ranged from 30 per cent, to 45 per cent, for sand. This is of course admitted. On tho 24th ultimo the •roduct of the new dust mill became available, and has been used in all top course material since that date. It is contended that the grading has been satisfactory and containing the neecs-* sary fino sand grading of 89 mesh H 209 mesh material. “X sample taken on the 26th ultimo gave tho following grading:— P.O. Motal passing ljin. hold on 10 mesh 50 Sand passing 10 mesh held on 80 mesh ..., 29.11 Sand passing 80 mesh held on 200 mesh 7.78—36.89 Filler passing 200 mesh 5.31 Bitumen R.GO 100.70 “The detail grading of sand and i Iler dust was as follows:—

“I might add further that we have had tests made of the gradings on the 24th, 25th and 26th ultimo, and these tests wero entirely satisfactory and in conformity with your requirements. Referring to the first paragraph of your letter of the 26th ultimo, the percentage referred to is based on the total mix and not on the quantity of the sand only. It has to be pointed out that in future your representative will require to include in samples of materials taken from tho plant trie fine sand and filler which is now bein" weighed out in the weighing bin and added as a cold charge to the heated sand and metal. “I am lather at a loss to understand why in view of your letter of tho 26th ultimo you did not say anything relative to this matter between Hie time of the receipt of my letter of the 11th ultimo and the date of your last letter of the 26th ultimo, which is in The form of a complaint. I understand that we wore to exchange views when any development occurred that required ad, justing. May I say also that no copies of tests of material made by your Department since tho date of tho conference have been sent to this office. AVith regard to the temperature of tho material delivered to tho road, 1 regret that von do not see tbe advisability of reducing tho range of temperature to 225 degrees F. In my opinion the anxiety to maintain a h'igher temperature tends to the overheating of material which is dangerous, containing as this material does a high percentage of metal. Rolling materia! at too high a temperature than is necessary also creates hair cracks previously complained of bv your Department, and it is difficult'to'control the -oiling of overheated material unless tbe temperatures are regulated at the plant. “Following the publicity given to your first letter,. members of the local board will probably insist upon similar publicity being given to future communications.—Yours faithfully, “(Signed) A. J. Paterson, “City Engineer.”

Passing 10 mosh 3.84 Passing 20 mosh 6.12 Passing 30 mosh 4.11 Passing -10 'n?sh 7.0!) Passing 50 mesh 7 92—29.11 Passing 80 Passing 100 mesh 1 01 cans h 6.77— 7.78 Passing 200 mesh 5.31- 5.31 ‘ 42.20 42.20