Aug 1 (Reuters) - Teck Resources Ltd TECKb.TO :
* Teck Resources Ltd - BC Hydro has exercised right of first offer to buy co's two-thirds interest in Waneta dam, British Columbia, Canada, for $1.2 billion cash
* No material changes to commercial terms of previously announced waneta purchase agreement between fortis inc and teck
* Says Teck expects to realize a net book gain of approximately $800 million on closing