History of the aqueduct

Aqueducts

The Dalsland Canal was completed between 1864 and 1868. The work was led by the famous canal builder Nils Ericson. Due to the ground conditions in Håverud, it was not possible to build a normal lock system there. The rocks were loose, the current strong and the slopes too steep. Nils Ericson then came up with the ingenious idea of building an aqueduct instead. His son, Werner Ericson, became site manager.

The aqueduct was manufactured by the famous company Bergsunds Mekaniska Verkstad in Stockholm. The plates were assembled on land and the heavy channel was then hauled into place over the rapids. The aqueduct is a free-hanging bridge, where the water is led in a 33.5 meter long sheet metal channel above the rapids. The plates are joined together with 33,000 rivets.

When the Dalsland Canal was being built, Håverud was the point on the route that was the biggest obstacle to an unbroken waterway. Here there was a ravine surrounded by high rocky shores. Through this narrow valley with steep sides, a gate was formed through which the Håverud stream plunges down a nearly nine-meter drop that flows into Upperudshöljen.

The construction of a canal in the stream, which was trapped between the high rock walls, was naturally associated with considerable costs and technical difficulties. That is why Major Liliehöök had recommended a railroad across Håverudsedet instead of a canal.

There was really only one satisfactory solution to the problem: to create a sailing route past Håverudsfallet, and that was to get the canal over the falls themselves in one way or another. Colonel Nils Ericson then proposed an aqueduct of iron sheet.

The constructions

The structure of the aqueduct has the form of a box open at both ends. The side pieces, in which the carrying capacity is extended, are arched at the top so that the height at the center is 10 feet, about 3 meters, and at the ends 6.5 feet, about 2 meters. Both sides and bottom are of ¼ inch, 6 mm English plate Foot and top flanges are of ½-5/8 inch, 12.5-15.5 mm plate - single at the ends and at the middle increased to triple. The top flanges also serve as a walkway or towpath with a railing at the outer edges.

To reinforce and stiffen the structure, a 'skeleton' of iron reinforcements is placed externally along the sides and bottom, consisting of two differently constructed systems which alternate with each other. One consists of an angle iron under the bottom, to which a flat iron reinforcement, in the form of an inverted hanger, is attached, and another angle iron riveted to the outside of each side piece, centered over the first, bent into the top and bottom flanges, and reinforced at an angle to the latter with a triangular filling plate. This kind of reinforcement is placed along the entire length of the aqueduct at intervals of three feet, about 0.9 meters. Every fifth of these is replaced by reinforcements of the second construction, which have angle irons under the whole bottom and on the sides like the former, but the inverted suspension under the bottom is replaced by a plate riveted to the angle iron, and on the sides there are also plates riveted to the angle irons. These filling plates are reinforced with an angle iron running around the sides and bottom, riveted to the outer edge, and another running under the bottom and past the angles and applied to the other side of the plate opposite the former.

Reinforcements of this kind are used at 15-foot, about 4.5-meter, intervals. Under all the bottom reinforcements, parallel to the longitudinal direction, two flat bars run to stabilize the vertical scaffolding. At both ends of the Aqueduct, the sides are further reinforced by more tightly spaced vertical fixed angle irons. Inside the aqueduct, at the same level as the water surface, there is a wooden strip fixed with bolts to act as a support.

At both ends the aqueduct is connected to the masonry built there. The dilatation (expansion/contraction), the harmful influence of which in ordinary bridges is easily prevented by movable rest planes, here also entails the inconvenience that the seal between the iron and the masonry must also be made movable. This is achieved as follows: At the eastern end, where the Aqueduct meets the wall column in front of the recess in lock no. 6, two vertical oak beams are bolted to the wall, and a horizontal oak beam is recessed and bolted to the landing wall. Between the beams and the walls is an interlayer of thick wattle. The beams are hollowed out so that the side plates are pushed into the vertical beams and an angle iron fixed under the bottom plate in the horizontal beam. The opening in the vertical beams is closed with a leather strap, one edge of which is pinned along the beam and the other can clamp tightly against the side plate through the wooden strip screwed to it.

The opening along the horizontal beam only needs to be filled with sawdust, behind which a small pinion is tucked. A cover of sheet iron prevents the sawdust from being washed away. The rollers under the bottom flanges of the sides are those commonly found in iron bridges. The bottom plate is supported by three upside-down pieces of rail, riveted to the plate and running on small rollers, two under each piece of rail, fixed in bearing seats.

The western end of the aqueduct rests firmly on the abutment, so there was no need for a movable seal. The transition from the iron to the masonry is also mediated here by oak beams, at which the sheet metal is simply nailed.

The aqueduct can be filled to a depth of 5.5 feet, 1.8 meters, and is then loaded with about 5,580 cents, 237,150 kg. If its own weight of 1,500 cents, 63,750 kg, is added, the structure has to carry an evenly distributed load of 7,080 cents, 300,900 kg.

The aqueduct has been manufactured by Bergsunds Mekaniska Verkstad, Stockholm, both in terms of detailed design and construction.

Placement on site

The foundations for the abutments are simple, as the walls could be placed directly on the rock. At the eastern end, pallet walls were cut and embedded directly into the rock. At the western end, a small rock under the water surface of the stream was used as the foundation for the abutment. It was easily accessible when the opportunity arose to lower the water level as much as necessary by keeping the mill's sluice gates open while the foundations for the abutment and other nearby masonry work were being laid.

The overhaul of the aqueduct required less elaborate arrangements than might have been expected. As both the depth and the strong current of the river prevented any support being placed between the abutments, the aqueduct had to be assembled on land and then hauled into place. A rocky outcrop on the east side of the stream, opposite the western abutment, came in handy. A makeshift abutment was erected on it using piles, which extended out into the stream so far that the distance from it to the aqueduct's western abutment was only 50 feet, about 15 meters.

The aqueduct was now cut together, resting on eight-inch round planed timber, the rolls of which extended over its entire width. The rolls went on five rows of long logs, which were laid on braced poles. The reinforcing skeleton under the bottom, which was to be in the way, was not put on until the aqueduct had been overtaken, and the vertical position of the sides was maintained in the meantime by braces applied inside the aqueduct. The space inside the western abutment did not allow more than half the length to be assembled at once. The eastern half of the aqueduct was therefore cut first and then hauled out and spliced in several stages until the end reached the opposite bank. Two Betancourt games were sufficient for this strong hauling. The heaviest work remained to get it in place. Blasting provided space for a rolling plane, which was formed from beams laid out crosswise, like an ordinary pile. In order to achieve both a turning and a forward movement of the aqueduct, the rollers of this rolling plane were placed obliquely under the ends of the aqueduct, or roughly perpendicular to the path it should follow. Two six-pulley hoists together with the winches were needed for this hauling. After the end had reached approximately the middle, the Aqueduct was first hauled to its full length and pulled into place.

Some comments on the aqueduct

"Between two huge, forested mountains, where the light shades of the deciduous trees mingle with the dark greenery of the conifers, a foaming rapids from the lake Åklången, which lies at a considerable height above, plunges through a narrow pass into the Upperud's enclosure. The bright morning sun casts its gold over the dull silver of the rushing waters, the roar of the waves penetrates the thunder of the bar-iron forges, to the left of the fall and high above the lock gates at Håfverud we see a gigantic, reddish-brown thing, which has stretched itself leisurely over the roaring current from one bank to the other. This huge, water-filled iron box is the infamous aqueduct, the only one in Scandinavia, one of the many memorials of Nils Ericson's giant genius."

From: Svea Folk-kalender, 1870, pp. 103-104