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Hokitika Guardian, 6 February 1924, Page 2

TiiKoi'tiiiorr Stratford County, the tarM'uling system is almost entirely adopted. The general principles on w hich this work is cariied out are in the case of refacing a. road which has practically served its day, as follows;—The old road is scarified up, and a coating of crushed met ill placed on the old metal, the depth of new* metal required must, bo determined by depth c-f old existing metal, solidity ot foundation, i (lie character and weight of traffic, local I conditions lnrving great bearing on the ! amotiui, of metal necessary. Alter n]'- | plying the new metal and rolling same, trio water eart is biought, into requisition (if only a limited supply of water e ill he obtained, a very light coat ol iriai,le clay is put on and well brushed in with a bass broom to fill the interstices between the stones). Then a coating ot I crusher screenings is placed on the I road, which is again watered and tho- | roughly rolled, 'this work should he completed to tho tip-head at the end of each day. If carried otic on these lines, the portion of the road under repair can lie thrown open for traffic, and little or no inconvenieee caused to the users during the carrying out- of the work. The road is then left ill this state till the traffic has thoroughly consolidated it. and the blinding (clay and screenings) has practically disappeared. Tarring operations can then he commenced, the first, and one ol the chief operations, consists ot thoroughly sweeping the metalled surface. A\ hen satisfied that the road is practically free of dust the sprayer is then run over the road, each run of the sprayer covers a width of up to a little over seven feet; the sprayer used by tlio writer in an F.nglisli machine, with a tank of a capacity of lf>o gallons, fitted with thermometer and pressure gunge. When spraying tt rond snt face the state of the side track or unmetalled portion of the load must he taken into consideration, it being necessary itt some cases to spray half tho width and blind same before coating the balance width. Where possible, lengths ot seven to eight- chains for the whole width are sprayed, and blinded with metal chips at d sand or if clear coarse sharp sand is available, with sand only ; with the latter, after the traffic has worn in the blinding a good clear surface is the result. If metal chips are used, they must he clean and free from crusher dusts. When using chips a light. coat of chips a.ro spread by hand with shovels over the wot tar. this is followed by a similar coat of sand. This ensures the whole of the surface being sufficiently coated to prevent, the tar being picked up by vehicles or horses using the road. This can be used for traffic immediately the blinding is put on. The tar used f-*** this work is equal to parts of Restar No 1 (delivered ill wooden barrels) and Restar No 3 (in steel barrels).

On* roads that have been refaced and are in order for spraying it- is advisable that the road should receive two tar dressings during the first season. One will not- he found sufficient to withstand the traffic during the bad winter. '1 tie second coat should follow* the first i ruin a month to two months later, the time entirely depending on the amount ani effect of the traffic on the road. A road refaced and tar-sealed one season should receive a tar dressing the following season. A\ hetlier it will be necessary to dress yearly cannot- be stated, it entirely depends on general conditions, and can be easily judged by the officer-in-chaige. When laying down roads preparatory to tar-sealing the camber should not he so great as on a water-bound macadam roail, as a heavy camber renders a tarred road dangerous for horses, the camber geneially adopted being a rise from side to centre of half an inch to the foot of the road width. The question of safe grades for tar-sealing is a debatable one, in Stratford county, the steepest tarred grade is one in twelve. In this case a side metalled track five feet j.j width has been formed on one side

of the tarred portion, this enables the horse mid one wheel of rehide to run on the side track the Other wheel being on the tar. In quite a number of cases, steep graded have been reduced to one in fifteen to allow of the bills being tarred. Taranaki, of course, does not have the severe frosts to contend with that several other parts of New Zealand have, a matter which must bo taken into consideration. A great deal

is heard of the great benefits to he gained by using bitumen instead of tar, it being hold that the life of bitumen is at least three times that of tar. A considerable amount lias been used this season, and it remains lobe seen

whether the results will come up to , .. , expectation. \\ liere used locally it has , , i , • i , \. oeen Sound to lie much more slippery , . tlian tar. hut this may he account- , , i , cd lor hv tlie possibility that tlie grade • , ' . • is not ol the right- peneration notessarv for a cold climate. Tt is not the imention of this county to place bitu- „ 7 nvn on a watrr-nound macadam road

till the first and possibly the second tar dressing has been well worn in by the traffic. The rondeau thou he said to he dust free when thoroughly swept.

A kkw lines showing the inainteniinco cost of some of tlie heavy traffic main roads, may he of some value. On the main road (Wellington to New Plymouth), which runs through Stratford canity for a length of nine miles, tlie annua! maintenance cost was about £3OO per mile, and tlie road could only he said to he in rough condition. Since tlie greater part of this road has been reduced and tar-sealed, the cost of portions has dropped lo about £2 per chain. Other tar-soaleil parts this year have not received a tar-dressing, hence the cost of these parts is much loss, the only work done consisting of a few tar patches and a small amount of sidebanking to protect the edges of tho iarroil portion. There are 2“ mites of tarred roads in this county an l a further 8} miles rclnid and ready for sealing. The season has been a particularly had one for tar work, and a full programme could not ho carried oni. With the sprayers used, one gallon of tar covers five square yards, or 22 gallons per chain on a Halt, road, the amount of blinding being two yards to that width per chain. While 11 general outline has been given of the methods used in the above work, local conditions must in all cases be taken into consideration. In most parts of Taranaki. the subsoil being of a friable and porous nature, il i.x not as a general principle necessary to do much road draining. The presence of water under an.\ road is. of course, well known to have detrimental effect, the effect being much more serious under tarred roads. The roads ns constructed are carrying heavy traffic up to ten tons; the by-laws framed and adopted by seven of tln- Taranaki counties restrict the load, including the weight ol the vehicle to ten ions. Without a personal knowledge of the material generally used in the way of metal for refneing. Hi., .state of foundation ol existing roasts, anti the pnssil.ilit ies ol pi ot-urillg suitable sand for top-dressing tar work, it is difficult to say how far the above remarks may he of assistance in other pa l'ts.