The Union ministry of environment and forests (MoEF) has served a notice on Vedanta Aluminium Ltd (VAL) to explain why the environmental clearance given to it in 2004 for a 1-million tonne per annum (mtpa) alumina refinery and 75 Mw captive power plant (CPP) at Lanjigarh, Kalahandi, should not be revoked. VAL has to also explain, in 15 days, why it began expanding the refinery from 1-mtpa to 6-mtpa, and the CPP from 75 Mw to 300 Mw without prior clearance.