Aberfan - Tip 7
21st October, 1966
The sister villages of Aberfan and Merthyr Vale are in the valley of the Taff about four miles to the south of Merthyr Tydfyl. The Merthyr Vale Colliery and part of the village were on the east bank and the village of Aberfan is on the west bank. The River Taff, where it flows through the village is about 42 feet above sea level. At about 515 feet above sea level, there is an embankment of a disused railway line and below it and further to the west there is a ditch from 5 to 15 feet away, which was formerly a disused railway line. The spoil heaps on the mountain side lay between the 650 and 1,200-foot contours and the heights above the mountain side vary between 61 and 110 feet. The slope of the mountain side above the village averaged about 1 in 4 up to the 900 foot contour and steepens to 1 in 3 up to the 1,000 foot contour when it flatted out to the ridge summit. There was a colliery tramway which took the spoil to the tip.
Under the tip the strata inclined towards the valley and was of cracked sandstone which let water through fairly easily. When the water went through, it came to an impermeable layer and springs formed on the mountain side which flowed down varying in quantity depending on the seasonal rainfall. The rock on the upper slopes was covered to a depth of 5 to 10 feet by a layer known as the 'Heads' which overlaid a deposit of boulder clay. A tongue of boulder clay extended up the mountain to about the 1900-foot contour and lay under the southern and eastern sides of the spoil heaps. Both the boulder clay and the Head had similar characteristics.
The two shafts at the Merthyr Vale Colliery were sunk between 1869 and 1875 and the fist tips were started to the west of the river.
Tip 7 was the tip that caused the disaster and was started at Easter 1958 and continued to be used up to the time of the disaster. It was estimated to be 111 feet high and to contain 297,000 cubic yards of waste including 30,000 cubic yards of material which was known as 'tailings' which the other tips did not contain.
The method of tipping at the No.7 Tip was old fashioned. The rubbish came either directly from the shaft, from the coal preparation plant or from the boiler house and was loaded into trams at the surface. When a journey was complete it was hauled by rope up a railway which climbed the side of the Merthyr Mountain. When the journey reached the engine house at the top of the incline it was stopped and the trams allowed to run by gravity, braked by a rope, to a parting and then to a point on the working tip where a crane stood. The crane was used to lift the tram and turn it upside down and the contents fell down the front or the sides of the tip according to the position of the jib of the crane. When this was done the tram was placed on the rails leading back to the operations. These operations were carried out by the crane driver and a gang of slingers who attached and detached the tubs. They were under the control of a charge hand. At the end of the working day it was the custom for the gang to bring the crane back from it's working position at the front edge of the tip to a point as far back as the short length of track permitted.