sentences:  Under DOSCO ownership, the CR&C operated its Springhill mines as efficiently as possible, however by the 1950s, demand for coal was softening as railways dieselized and alternative heating fuels were implemented.DOSCO made few capital investments in the Springhill mines as production was winding down, which is believed to have contributed to two mining tragedies in that decade.The 1956 Explosion was caused by a runaway mine tram on November 1, 1956 and killed 39 miners.