Phase 3: Waunfawr to Rhyd Ddu, 2000-3

The Betws Garmon River Bridges


Phase 3 pages:
 
Betws Garmon river bridges

Route map ( J.C. Sreeves) - will open in a separate window.

UB51

Immediately beyond the site of Betws Garmon Station, the railway makes the second of its four crossings of the Afon Gwyrfai (the first being Bontnewydd Viaduct). In addition to the main river bridge (UB51) there is also an adjacent spillway (UB52) of entirely different construction.

Contract 3A was initially awarded to Triact Civil Engineering Ltd of Colwyn Bay, who moved onto the site of Betws Garmon Station in late October 2000 to pursue clearance work. An early goal of this contract was the removal of the old river bridge on November 2nd 2000, prior to the driving of piles to protect the sites of the new abutments. The piling work is visible (left riverbank) in the left-hand picture below. On the bank opposite the station, a temporary contractors' access track was established, reaching the trackbed at the site of an occupation crossing.

The bridge girders were moved to Dinas. Analysis of the bridge prior to lifting proved that it was indeed made from wrought iron and not steel, as had been suggested in some sources. The resistant properties of wrought iron (the proper kind, from a puddling furnace) would help explain the relatively modest corrosion of the Gwyrfai bridges in their long years without maintenance or even paint - though the humourous WW2 "Mr Chad"-style "Wot no Railway?" applied to this one by some railway supporter long ago remained just visible to the end (does anyone know for sure just how old the graffiti was? Feedback from website visitors now has it dated back to at least 1962 - though another account suggests paint was applied in the mid-1970s, and yet another details at least a repaint in 1983! The picture below shows it in October 1986).

In mid-January 2001 Triact were back on site at Betws Garmon, building the new abutments for the river bridge, as seen in the mid-March picture below left. The middle picture shows the cast concrete abutments at the start of April. The spirit of "Wot no railway?" seemed to have rubbed off on the contractors, with a "road ahead closed/ffordd ymlaen ar gau" sign fixed to the river side of the northern abutment. The right-hand picture shows the abutments largely complete in mid-May, with stone cladding on the faces which would remain visible when the bridge was complete. The span between the new abutments was greater than the old, as the Environment Agency wished to improve the flow of the river at this point; re-use of the beams from original bridge span was thus not possible at this site, unlike the two similar bridges further south.

In early 2003 a change of plan occurred regarding the new span of UB51. The Railway obtained components from a virtually unused modern single track span ideal for the site at a cost well below the estimates for the all-new steel structure which had previously been planned for the site. The span required some modification, notably to do with turning it into a straight span - it was on a skew angle at its original location. The design work was done by volunteer structural engineer John Sreeves, to whom WHLR Ltd expressed its gratitude for the tremendous amount of design work involved.

The span is made up from two of four identical 18.2m beams from a double track standard gauge bridge, 18.2m long and made from 38.1mm steel plate. To give the full length needed to give a firm location on the abutments, each beam was extended at one end by a 1.143m extension cut from one of the remaining beams; the actual gap across the river, measured across the inner faces of the new abutments, is 16.8m. These extensions are at opposite ends of the two beams, compensating for the skew angle the components were built for while allowing the crossmembers to provide the structure's full design strength, as they had to coincide with existing stiffening pieces in the webs of the beams at 1.524m intervals.

The components were found in a location where access to remove them was extremely difficult, but this process was expedited with all possible speed, as Phase 3 obviously could not open without this structure complete.

The purchase of the redundant bridge from Network Rail (successors to Railtrack plc) was completed in March. The components were recovered from their location at a site near Sheffield on April 8th and delivered to the heavy engineering works of Whiteley Engineering Ltd in Rotherham the same day.

John Sreeves' picture below shows work in progress on the beams on April 16th, and the paragraph below the picture is his explanation of what was being done.

"The right hand beam is standing upside down. At the time of taking the picture, welding of the extension piece at the far end was in progress. The large blocks projecting from the top flange at either end will be where the beam will be supported on bearings. The vertical fins are web stiffeners which will be on the outside face as viewed when the bridge is assembled. The other beam is on its side with the top facing to the left. Shear plates are visible on the web, which will form the bolted connection with the cross girders. The end nearest the camera has been prepared for welding. In the right foreground is the extension piece, which after trimming square will be welded onto the end of the girder lying down. The beam extensions are joined on by full-penetration full-strength butt welds, being done by experienced and certified welders in preference to bolting. This change was necessary because surface irregularities and fabrication distortion discovered in the beams would have made it difficult to achieve a tight fit with splice plates."

The extension of the main beams and the modification of the cross beams were complete by April 25th, and this work was followed by the fabrication of four new rail bearer beams (similar to those on UB56 and UB64) to complete Whiteley Engineering's work on the bridge. The components then went to a contractor in Sheffield for shotblasting and priming before delivery to Wales.

The beams and waybeams were delivered to Waunfawr on the morning of May 13th; they were too long to be moved by lorry directly into the Betws Garmon site. The components were craned from road to rail wagons at the yard where the Waunfawr rail stack was, and were then propelled to Betws Garmon. This was done before the start of the day's passenger service; the construction stock stabled south of the station had to be moved into the platform to allow the beams through. Jan Woods' pictures below show the process.



The Funkey was used to move the beams to the southern end of the station, its power being needed here because of the steep gradient up from where the beams were loaded. It then worked back to Dinas to haul the passenger service. Conway Castle then shunted more wagons (carrying the cross beams) behind the main beams, following which Upnor Castle propelled the bridge components, plus the ballast hoppers (and towing the ballast plough), along the relatively level run to Betws Garmon. Jon Marsh captured the convoy approaching its destination (below).

The crane then moved to Betws Garmon to unload and help assemble the components, which was done by late afternoon. John Sreeves' and Jon Marsh's pictures below show, in sequence: (i) offloading of the first beam; (ii) the first of six cross members being lowered on to the sleepers and bolted on to the main beam at the left hand end; (iii) all six cross members in place, the chains being prepared for lifting the second main beam; (iv) the crane preparing to lift the second beam; (v) the lift in progress; (vi) the second main beam being gently lowered into place and offered up to the ends of the cross beams; and (vii) the job done, with the waybeams in temporary positions, prior to drilling work to enable them to be bolted in place permanently (96 bolts in total). In their final positions, the waybeams would lie directly over the web stiffeners of the cross members. Initial assembly of the structure was done with ordinary 22mm bolts - all of which fitted first time - which were subsequently replaced by high strength friction grip bolts of the same diameter, precision torqued to make the permanent connections.


Once the waybeams were in place mesh walkway were added (some angle sections for supporting the edges of this are visible in the last picture above), and the bridge was painted on dry land before the complete 35-tonne span was craned into place on the abutments. Work on the abutments included setting the bearing plates, and making short concrete plinths at either end to support the ends of the waybeams.

The painting was already in hand by May 18th, as seen below in a view from OB53 (left) and on site (right, picture by Dave Waldren).

Clive Briscoe's pictures below show painting in progress on the evening of May 29th, with volunteers from Wylfa Power Station on the second of two visits that week. The structure had been jacked up on sleepers to allow painting of the lower surfaces, including those which mate with the bearer pads and thus are unlikely to be seen again for many decades. The waybeams were partly secured, and the walkway angles were bolted in place and primed. Completion and painting of these items were the only main tasks still to be done before the span was carned into place.

The site is seen below on May 31st, with work in progress on the modifications to the abutments to suit the new span, specifically the concrete plinth to support the four protruding rail bearer waybeams.

Jon Marsh's pictures below show more of this work. In the right-hand view the shuttering had been removed on the northern side of the river to allow accurate measurement for the outside locating strips which were being fitted to the bearer pads; these locating strips also serve to retain the rubber strips which go between the bridge beams and the bearer pads; similarly, rubber strips were fitted between the waybeams and their plinths, which were cast after installation of the span.

The span was lifted into place on June 5th. Although the span weighs about 35 tonnes, the crane reach needed to place it across the river meant that a giant thousand-tonne capacity Demag telescopic crane was needed, itself weighing a total of about 200 tonnes when set up for the lift with all its additional balance weights. Roger Dick's pictures below show the span being lowered into place, and the result.



This operation marked the closure of the final gap in the trackbed from Waunfawr to Rhyd Ddu.

While the new bridge is a more substantial piece of engineering than its predecessor, it fits very comfortably into its surroundings.


UB52

Triact carried out a major reconstruction of the adjacent river flood relief spillway (UB52), and the associated formation. This work involved excavation down to ground level of the embankments either side of the spillway (left-hand picture), and a new internal deck for the spillway (middle picture). This structure now has a new load-bearing concrete structure (abutments and deck), concealed when complete (see work in progress on this in the right-hand picture); the original slate pillars remain in place.

The following pictures show rapid progress. On the left, the new deck can be shown standing without support from (or contact with!) the pillars; in the second picture, re-cladding work has started to restore the appearance of the original structure; in the third, the job is largely complete; the fourth shows the finished product.

The floods of early November 2002 gave the rare opportunity to see UB52 fulfilling its purpose as a spillway, for times when the main channel of the river cannot cope with the flow on its own.

The picture below shows the view back to the Betws Garmon station site, with the spillway in the middle distance and the river bridge abutments behind.

Following the structural completion of OB53 to the south of the river bridges, the contractors were back on this short stretch in mid-October 2002, preparing the trackbed from the gap at UB51 onwards to the Head of Steel just beyond OB53. In the left-hand picture below, the roller is standing on UB52; the right-hand picture is from a week later, with the sub-base in place and rolled.

Ballasting of this section finally got under way in mid-June 2003, following installation of UB51, where a working party can be seen below.

A week on from the above picture, the ballast bed had been laid from the Head of Steel south of OB53 across UB52 and to within a few metres of UB51.

The contractors are seen below finishing this last gap in the ballast bed on June 27th, just in time to hand over this short section for tracklaying; rails were already being moved up from the south ready for tracklaying to proceed under OB53 and across UB52 and UB51; by this point the sleeper deck of UB51 had been bolted in place.

Tracklaying reached UB51 from the south on June 29th, leaving just a short gap to join up with the track from Waunfawr - visible in the middle picture below, together with the disconnected track just beyond. This had been disconnected and raised into a ramp to allow loading of the construction stock moved to Rhyd Ddu by road in May.

The two lengths of isolated track at the old station site had been lifted by July 2nd, allowing a fresh ballast bed to be laid north of UB51 to give a smooth run of track through the site.

The track had been relaid by July 5th, at which point the ballast train returned from Rhyd Ddu by road; the tamper arrived between the two pictures below. The ramped track was reconnected to the main line on July 7th, to allow completion of ballasting, tamping and lining south from here towards Castell Cidwm. Harold was the first loco across UB51, as he had been across the other two Gwyrfai bridges.

The scene below, just four days later, shows the track fully connected, top ballasted and tamped. The ballast finishing works were already well south of this area by this time, although they only started on the 7th.

The bridges are seen below on July 26th, with UB51's guard rails in place, and work by the fencing contractors well advanced on the occupation crossing between the bridges, and another further back in the old Betws Garmon Station site.


Phase 3 pages:
 
Betws Garmon river bridges

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Authored by Ben Fisher; last updated January 7th, 2005