Apparently recent, despite the bone-dry conditions. Bizarre.
How's that for a terrible photo...
Single adult, approximately 27 cm long. Body slim, not too chunky. Upper body color dark brown with copper-colored, irregular network of splotches. Fully eyed and actively moving from lights.
Located approximately 240 m inside entrance of disused tunnel under an abandoned marble quarry in access-controlled private conservation tract near Davenport, CA. Elevation approximately 128 m.
Floor of tunnel has perennial stream with discharge varying from approximately 3 l/sec. autumn low flow to El Nino flood flows of approximately 2700 l/sec.
Salamander was in shallow pool with rotting redwood mine timbers and large volume of iron bacteria mats as well as root mats of douglas fir(?) growing down through soil-clogged solution passages approximately 20-30 m below quarry floor. Temperature approximately 13.3°C.
ID based on poring over field guides, pulling my hair out, until I finally just gave up and winged it.