Jobs under threat in Nant Helen mine mothball plan
A Powys opencast mine could be mothballed, resulting in 90 redundancies.
Celtic Energy said it followed an announcement by RWE that Aberthaw power station was unlikely to require large volumes of coal beyond March 2017.
A consultation on the plan for the Nant Helen opencast site has begun with trade unions and other parties.
The company said the state of the coal industry meant "difficult decisions are inevitable".
In October, Celtic Energy announced its decision to mothball its opencast coal site Selar, near Glynneath, for three years, resulting in 70 people losing their jobs.
When that decision was taken, the company said it could not keep the site running along with Nant Helen and the expanded East Pit.