BINGEN, Washington — A plywood mill in the southern Washington city of Bingen will close next month and lay off all 81 workers, the plant’s operator said Thursday. The SDS facility has been operating — with occasional stoppages — since 1949. It uses older equipment, according to Wilkins, Kaiser & Olsen, which was part of a consortium of firms that acquired the mill in 2021. “Regrettably, the long-term challenges and the magnitude of the required investment render continued operation unsustainable,” the mill’s operators said. An adjacent stud mill, planer mill and marine facility will continue operating. Bingen is a small city just across the Columbia River from Hood River. WKO and an affiliated business, Mt. Hood Forest Products, are adding 60 full-time positions to increase their output by 35%. The firms said they will consider hiring some of the laid-off workers.