Subterranean sanctuary for slender salamanders

Several months ago, I constructed a little "sanctuary" for subterranean animals because the rest of my backyard was starting to desiccate and I wanted a way for the other animals (particularly salamanders ) to flourish in an area I could somewhat manage and observe. Basically I dug a little pit, added some leaves and other humus, covered it with a HEAVY slab of rock, and introduced worms, slugs, a couple salamanders, etc. Today I decided to lift the slab (very carefully, mind you) and the first thing I saw was one of the largest, healthiest slender salamanders scrambling for a place to hide. I kept looking under the leaves I added trying to cause as little damage as possible and found even more really healthy looking salamanders. In all I found about 3-5 and one or two juveniles. It really made my day. Here are the pics, sorry for the awkward blurs. My GoPro doesn't have a zoom button and I kinda don't know how to make it focus properly lol.

Cool! I tried something like that eons ago when I was a teenager. And as the kids say today it wan an epic fail.

I live in coastal southern california, near los angeles. Slender salamanders and alligator lizards are usually the only herps I find in my backyard so when I do find them it's great. I checked the slab again today and added more decaying plant matter to it. I also found a really small baby slender salamander and in nearby bricks I lifted I found quite a few (about 5 or so) adult or juvenile salamanders resting. The biggest was a kinda fat adult (probably gravid?) but I also found a juvenile with part of its tail missing. I moved them near the sanctuary and they crawled under it readily. I don't know which exact species the salamanders are, but they looked kinda distinct from eachother so they could possibly be different species. Here are the pictures, I need to learn how to do close-ups on a gopro because it's focusing on the background more than the actual subject lol.