A hydro-electricity power situation built at the end of the last century to serve Welsh slate quarries is to be reopened after almost 50 years to feed a growing British appetite for "green" electricity. National Power, the generator that last week announced plans to demerge its international and domestic electricity business, has spent 1 million pounds ($1.61m) rebuilding the Croesor hydro plant at Blaencwm in Snowdonia national parm, north Wales.