Here are two images of the western tunnel portal to Maynard Mountain, on the east side of Bear Valley. These photos were taken on a sunny Sunday afternoon in February 1986. Back then the only way into Bear Valley was to walk across Portage Lake when it was frozen. It's interesting to note how far from the side of the hill the tunnel portal is. I'm guessing it was extended to avoid snow sliding down the hillside and accumulating in front of the opening. I do recall looking in the windows. It looked like there were living quarters with old metal beds and a kitchen area of sorts. It was not being used at that time.
Photographs courtesy Jonathan Fischer