|Battery #131 is in the Salt Creek Recreation Area west of Port Angeles. Take highway 112 about 8 miles west from Port Angeles and follow signs to Salt Creek rec area. The battery is on the road inside the campground that has a sign for the trailer dump, just follow it and you'll drive right into the #1 casemate.
Most of the battery is closed to the public, but you can drive through the casemates and look at the air compressor rooms. (I had to arrange a special tour to photograph the interior rooms.)
The plotting room is off to the right of the road if you stay on the road rather than entering the camp ground. It's sealed up tight, the escape shaft is buried and the vent shaft in mostly buried.