This is an account of the building of the old bridge across the Blackwater at Youghal, between 1829 and 1832. The account was written by the site engineer (if that’s the right title) John Jones A Inst CE ** in 1837; the bridge was designed by Alexander Nimmo.
Jones’s account was published in Transactions of the Institution of Civil Engineers Volume II John Weale, London 1838; it also appeared in the American Railroad Journal, and Mechanics’ Magazine [No 8 Vol V New Series, Whole No 368, Vol XI] October 15, 1840.
Note that the modern bridge is at Rhincrew; Nimmo’s suggestion for a suspension bridge at that point was rejected.
Here is Mr Jones’s account.
Account and Description of Youghal Bridge, designed by Alexander Nimmo
Youghal, a town in the south of Ireland, county of Cork, celebrated as being the place in which the potatoe [sic] was first planted in Irish soil, by Sir Walter Raleigh, is a sea-port of considerable trade, situated on the river Blackwater, which separates if from the adjoining county of Waterford.
Until the building of the present bridge, a dangerous ferry of nearly half a mile was the only means of communication at this point between the two counties, except by going a distance of sixteen miles by the bridge of Lismore.
The erection of a bridge, which had been for many years in contemplation, was at length decided upon by the principal inhabitants of Youghal, and the late Mr Nimmo, then employed as government engineer in Ireland, was applied to. He accordingly gave two designs, one for a suspension bridge at Rencrue, where the river narrows, the other, a timber one, within a mile of the town; the latter was preferred for many reasons, viz: from its requiring an embankment to be made to low water mark, a distance of fifteen hundred feet, forming one side of a triangle, which, when completed, would enclose a tract of ground nearly four hundred acres in extent, and would also save much trouble and difficulty in forming the new line of road to join the old one leading from Waterford to Cork; but principally from its economy, there being ten thousand pounds difference in the estimates.
It was commenced in the year 1829 under my superintendence, and finished in the year 1832.
Description of bridge
Its site is upon an arm of the sea, which forms the mouth of the river Blackwater, the rise and fall are sixteen feet each tide, the rapidity of its flow being so great as to increase one half its height in the first quarter.
There are two channels, east and west, separated by a bank of sand, the tail of which passes under the centre of the bridge and is scarcely covered at low water. The quay on the Waterford or western [should be eastern] side is two hundred feet square, and its channel upwards of twenty feet deep at the lowest spring tides; from this circumstance it was considered the best place for the bascule, which was for the accommodation of the larger trading vessels, the smaller being enabled, like those on the Thames, to pass under by lowering their masts. The embankment on the eastern [should be western] side is fifteen hundred feet in length. The face walls are built in good dry rubble work, varying in height from two to twenty feet, along which line there is a belting course laid in mortar, to support the parapet, which is four feet high and two feet thick, that next the sea having a curved batter of six inches to the foot; the upper face two inches to the foot; top of the wall is two feet six in breadth, with counterforts five by four and ten feet apart; the road is thirty feet broad, and there is a footpath on either side of six feet.
The foundations for the walls are formed by placing a heap of loose stones about six feet in depth along the entire line; upon this were deposited the materials for the future wall. This weight sunk the stones a considerable way into the sand. The filling was thrown in, and the whole allowed to remain in that state for twelve months, during which time, if any part of it sank, there was more added, until it at last became one firm mass. The temporary walls were then taken down and rebuilt, according to the section given in the drawing.
The bridge unites with the embankment at low water mark, and is 1542 feet in length; it is composed of 47 bays of 30 feet span. The bascule and its piers 80 feet and 52 feet, the space occupied by the piles making the total length of timber work 1542 feet. Its breadth is 22 feet, and height above high water 10 feet, which makes a variation in the length of its piles from 36 to 70 feet; those I have drawn are the two extremes as far as the depth of the piles in the ground, but are shown in 15 feet water.
The timber is of crown brand Memel, selected by one of the contractors who went there for that purpose. The beams were 14 inches square, and in length from 44 to 90 feet; the specification only required that the piles, caps, and all the larger timber, should be 12 inches square, but the contractors did not reduce it, though they were aware that it would have paid very well for its sawing. Mr Nimmo, in his specification, allowed the piles to be scarfed, which however was not necessary, as long as the selected timber lasted, but from not having imported quite enough, they were obliged to have recourse to this method, not being able to get any of sufficient length in either Cork, Youghal, or Waterford. The quantity of timber used was nearly as follows:
The dimensions of the gauge beams, diagonal braces, caps, bolsters, joists, struts, straining beams, purlin beams, and flooring, etc etc are given in the large elevations and sections.
The caps are fastened to the heads of the piles by an oaken coke three inches in diameter and six in length, through which an inch and a quarter iron bolt is driven. At each side of the high water gauge beams, there is an iron strap three inches broad and half an inch thick thoroughly bolted. There are also three tailed straps at the joining of the struts and straining beams.
In the specification it was said the piles were to be driven ten feet at least, or until they did not move an inch after receiving twenty blows of an iron ram five cwt falling ten feet; however, upon driving the piles which formed the first pier, I found that the bottom was so soft, that their own gravity sunk them five or six feet, and that it required very little additional power to drive them the remainder of the ten feet! Upon applying to Mr Nimmo, he said his idea was, that ten feet would have been enough for the piles to go into the ground, and that it was only in cases where they would not go that depth that he specified otherwise. This circumstance, as well as my observing that the narrowing of the river by building the embankment on the eastern side had caused a washing away of the bottom, induced me to recommend the commissioners to pay an additional sum to the contractors for driving the piles as far as they would go, which proved to be in many instances 25 feet. In cases where the ground was at all hard, the piles were shod with iron, as I have shown.
The quay wall is four feet six at the top, and twenty-six feet high, battering two inches to the foot, with counterforts four by eight, and ten feet apart.
There are two toll houses and about three miles of new road, which comprises all the works connected with this bridge.
The entire length is as follows:
The expense was under £18,000, but it could not have been done for anything like that sum, had it not been near one of the finest quarries in Ireland.
** I suspect that the Dictionary of Irish Architects may be in error in saying that Jones was responsible for a bridge over the Suir.
Waterford Council has a page about the Youghal bridges here with some nice photos.