This is a one trailhead great outdoors trail, so you're looking at an in and out backcountry walk. Puako-Waimea Trail has a total elevation difference of 164 feet which is lower than average. Being 3.6 miles long it's a shorter type hike. You spend the whole hike in roughly the same elevation zone which means the conditions are about the same from start to finish. The time needed for this backcountry hike is roughly 3 hours, but of course some people walk a bit slower and some a bit faster. This is not a very long hiking trail but you should still bring some emergency supplies just in case something happens. Sometimes this hiking trail gets really dry, so do check for current fire restrictions before you go if you plan to bring a stove or make a camp fire.