STN 1 (NOT 0) is PSS
STN 15 is climb up into crawl to avoid pitch at STN 13
STN 20 crawl rejoins main passage
STN 23 is PSS in small chamber by wet crawl
STN 31 is PSS at bottom of pitch
STN 38 is window above bath/canticle pitch
STN 53 is Octarine Core STN 13