Hello JB.
The chimney is on the trail above and to the right of the rail road tracks in the gorge. There are several access points to the ridge just west of the resort. If walking south on the ridge before you get to the rail road cars below the trail intersects with a trail going above the gorge. The trail descends to a small group of trees after these trees you will encounter another group trees in a few minutes walk. Then the trail goes up a bit. You will see old rusty cans strewn along the hillside down slope to your left. Look for a cairn on your right and a narrow foot path leading up hill. This will take you to a clearing where the chimney is. I think it was from the bunkhouse for the rail road workers running the water tank there.
I took my md up there one day hoping to find some old coins and only got a big hit for silver in a rock I found laying around. I left it on the hearth.
In probing around with a piece of re-bar I'm pretty sure I found the spot for the out house yet I didn't feel the need to disturb what has got to be a huge stash of old bottles and such. I was just trying to figure out the layout of the place and how they lived.
Here is the latest news from De Anza with an article on the history of the trails. There is a link at the bottom to more info on trails and if you look under activities on the website a list of trails.
Cheers.
Jim
http://www.deanzasprings.com/wp-content/uploads/2019/11/Newsletter-11-19-2019.pdf