The 'story' is that there was one. No one is certain that it was completed though. In the mid 60's some teens tried to dig from the Redoubt entrance and it caved in on them. One got free and got help. All 4 were ok. They were neighborhood friends. A couple of us had been there with them and told them they were crazy and didn't think they'd try it. We left and went home. They were on the front page of the newspaper the next day.
With the soil being sand, a tunnel sounds unlikely but there is the one from Barrancas to the Water Battery. When I talked to a Ranger a few years ago about it, he said they believed there was one but they tell others there wasn't to prevent what happened in the 60's. He didn't tell me that til I told him I knew about the 'dig'. Seems like there aren't any drawings of it but the probable entry at Redoubt has been located and filled in with a lot of rubble to keep dummies out.

Pam