Possibly it is mounted too high - it is atop a very tall pole right beside the highway, pretty hard to see anything but the pole while driving by. This siren could be a remnant of either World War II or the Cold War, as nearby were potential military targets, primarily during World War II.
Just half mile from this siren was the
Cominco Fertilizer Plant which, during the war was used to produce heavy water for the Manhattan Project. It also produced explosives and marine engines for the military during the course of the war.
A further half mile distant is the Cominco Smelter, at the time the largest zinc, lead, copper smelter in the world, which supplied a great deal of the Allies' strategic metals during both World Wars. As such both the smelter and the fertilizer plant were considered potential targets of an air attack in the second World War. The heavy water plant was shut down in 1955, but the smelter continues in operation to this day, as does the fertilizer plant.