Roundup Record Tribune & Winnett Times -

HELENA, Montana — The Montana Public Service Commission on Tuesday trimmed $9.4 million from an annual rate adjustment requested by NorthWestern Energy, after concluding the utility’s imprudent supervision of the coal-fired power plant in Colstrip, Montana, led to its temporary shutdown in 2018. With interest, NorthWestern will be required to refund more than $9.9 million to ratepayers.

For about two and a half months in the summer of 2018, the power plant had to be shut down after testing showed the plant’s emissions exceeded federal pollution standards. Tests leading up to the outag...