Starting Friday, local Avista Utilities customers will see their usage rates decline. The Oregon Public Utility Commission announced Tuesday it approved rate decreases for all three of the state’s natural gas providers — Avista, NW Natural and Cascade Natural Gas Co. The PUC approved changes for Spokane-based Avista, to reflect declining wholesale prices that will lower customer costs by more than $7. 8 million, or 8. 3 percent, from November 2017 rates.