The only hospital in western Nevada County will put management to work in its emergency and intensive-care departments if mediation fails to avert a threatened strike. A union representing nurses, pharmacists, laboratory technicians and housekeepers at Sierra Nevada Memorial Hospital has given formal notice that it intends to strike Tuesday unless the hospital makes an “acceptable offer” for pay raises, work conditions and benefits. A federal mediator has been contacted, but no talks have been scheduled. A spokeswoman for the hospital in Grass Valley said the 124-bed hospital would postpone elective surgery and non-emergency tests but keep its emergency room and intensive-care unit open in a strike. The closest hospitals are in Marysville and Auburn, about 35 miles and 24 miles away, respectively.