On a cold but clear winter morning
|Type||Site of temporary terminus|
|Stations | Locations | Bridges | Tunnels | Map|
|Deviation | Dduallt|
Llyn Ystradau was the temporary terminus of the FR from 25th June 1977 (although public services did not commence until 8th July) until 24th June 1978, when the Deviation was completed and opened to Tanygrisiau, after which Llyn Ystradau was not used.
It was about 11¼ miles from Porthmadog on the shores of the Tanygrisiau Reservoir (never called Llyn Ystradau by its owners the CEGB, so it appears on the Ordnance Survey by the unromantic name of Tanygrisiau Reservoir), beyond the new Moelwyn Tunnel and not far short of the intermediate summit of the line (at a height of 669 ft) behind the Ffestiniog Power Station.
The station here was a temporary expedient in order to operate trains over as much of the Deviation as possible pending completion of the section behind the power station. It was originally intended to be named Buarth Melyn after a farmhouse that used to stand at this spot, but in early 1977 the Company decided it should be named after the lake created by the CEGB pumped storage scheme which flooded part of the line around 1960. The FR had built the Deviation to by-pass this Lake.
According to FRM 75 (Winter 1976-7) the name change was because it was thought that English visitors would have difficulty with the pronunciation of Buarth Melyn. Why it was thought that Llyn Ystradau would be any easier is not explained. Actually a more valid reason would have been that there is no trace of the old farm, but the lake is very evident.
It was originally intended that as there is no road access to the location, passengers would not be allowed to alight or board there, but in the event there was a platform and footpath-only access.
Laying of the main line was carried out by a Dee & Mersey working party in July 1976 and the loop in temorary materials was laid by Brambleton Model Railway Club at their summer camp in August 1976. During January 1977 a loading ramp and approach road was constructed so that ballast and other materials could be moved in four ex-RAF wagons to carry ballast to ballast the new line from Tunnel North Cutting to Llyn Ystradau.  Later the loading ramp and a torpedo wagon were used to take readymix concrete to the tunnel. Before the station could open a platform was built. Standard gauge concrete sleepers formed the front edge and a framework was constructed to robustly support the fence at the back of the platform which was on the edge of an embankment on the side nearest the lake.
The concrete standard gauge sleepers that form the redundant platform edge were moved in 1978 to the Cob to form a ballast retaining wall alongside the public footpath. 
Laying the loop, 1976 (with Four-Wheel Modified Slate Waggons#Wagon 140?)