In 1909 the Bedwas Colliery Company leased 1,475
acres of land, on the slopes of
Mynydd y Grug just outside the village of
Trethomas. As the best and easiest mineral rights had already been taken, Bedwas was forced to go deep, and called on the proven continental experience of
Austrian Edmund L. Hann (cousin of
meteorologist Julius von Hann), to design the colliery, having previously designed
Penallta Colliery. To sink the shaft the company used the same experience formula, engaging mining contractor Fred Piggott from Caerphilly (the former owner of a mansion that was The
Caerphilly District Miners Hospital), to be responsible for the entire sinking. Two shafts were sunk through the Mynyddislwyn seam, down to the Rhas Las (English - Black Vein) and thence, by a cross-measure, to the lowest coal seam then known in the Caerphilly area, the Hard Vein, known later as the Lower Black Vein. The two shafts (North and South) were 768 and 802 yards deep respectively (more than twice the height from ground to the roof of the
Empire State Building), both with a diameter of 21 ft. Due to its depth, Bedwas was one of the first collieries in South Wales to employ double-deck winding to improve efficiency. The purposeful insertion of the word "navigation" was undertaken to entice orders from marine shipping customers, including the
Admiralty. The
Royal Navy liked coal from Rhas Las, and hence many of the mines which extracted coal from this seam added "navigation" to their name. ==Operations==