What would you do with this space?

Hi everyone!

I am a single middle aged person in a large Southern California city.
Plants, permaculture and etc is a very strong interest of mine, although due to my full time career I can't dedicate endless amounts of time to it.
My housemate volunteers himself to help with manual labor some of the time...but he's more of a tech guy....so designing the space and growing things is essentially all up to me.

Last spring/summer (2019) I decided I wanted a little pond in my small (30'x50') urban backyard.
I didn't want an outdoor aquarium, run with filtration and electricity and chemicals; I wanted a naturally balanced pond.
I wanted it to be attractive, available for the birds and insects (and possums); and I wanted it to be an extra water source in case the urban supply ever cut out.

Suffice it to say it was a heck of a lot of work to create. Digging, getting the rocks and pebbles and etc...
Then, it was utterly gorgeous for six weeks until the local raccoons discovered it, had their way with it and turned it into a muddy disaster hole.
It was around that time that I learned about the wicked parasites and diseases they carry. I had to go out of town last August, and I didn't want to leave my housemate with a diseased mudhole, so I drained it.

It's been like this ever since.
I was about to resurrect it, but I never did get a good raccoon barrier up.
A cover or an electrified fence just seemed so ungainly and unsightly.
I had the idea to line the first shelf with stiff little pokey wires (like the ones on those landscaping flags) sticking up out of concrete "rocks", so that they would have nowhere to step down and put their little paws in the pond. The wires would be stuck into heavy cement rocks so that they couldn't drag them out of the way.  I haven't done this project because it seems costly and time consuming, without any real guarantees of working.

Additionally, I was never really satisfied with the EPDM pond liner design. I didn't like the possibility of puncture, its tendency to reveal itself as the rocks slipped, and the fact that you have to surround the pond with all kinds of rocks to weigh down the lip of the liner. And again, the rocks would slip and you'd have this ugly black rubber sticking out. Not a very durable solution, really.

So now I have this big old hole that we dug by hand.
I'n not sure what to do with it.
In the winter, it gets essentially no sun (it's on the north side of my house, and I'm in northern hemisphere).
In the summer it gets a bunch of sun. It has a sailshade over it (for algae control) but it still gets some sun that angles in under and around part of the sailshade.

So of course I'd love a pond; but I'm wary of the labor and very wary of the potential for disease vectoring.
We did manage to avoid mosquito larvae by means of mosquito dunks and a few dragonfly larvae.

Here are my thoughts for the space--please add to these, or suggest a totally new idea!

1. I could fill in the hole and use the space for my baby plants.
That would require leveling all the nearby soil, which has some little slopes... by pushing the excess dirt into the hole.
Again, lots of physical labor, oh and the soil has some lead contamination, thank you older urban neighborhood.
All the labor we've done developing it, would be lost--but then, I don't want to fall victim to the "sunk costs" fallacy (hahaha! sunk!)

2. I could use quickcrete and seal up the bottom of the existing space, and make a pond that way.
That way, no raccoon puncture vulnerability. And no hassle with the lip of the liner or the sliding rocks revealing ugly black liner.
However, I'd probably have to devise some kind of a filter. I'm still a bit afraid of the labor and the potential disease vectoring.

3.  I don't know! Argh! What have I gotten myself into? My enthusiasm and desire often outstrip my time, energy, knowledge and ability to do research.

Thank you so much for your thoughts!

Raccoons, yes, can carry disease, as can any animal, including our pets, the risk is minimal, to nonexistent to those with a normal, healthy immune system.

Specifically looking at raccoon roundworm (that is present in almost two dozen mammal species), Baylis ascaris, when I looked into this year's ago the numbers were less than 20 humans EVER infected, in ALL of North America...and most, if not all of those cases were from humans who resided with "pet" raccoons, in their homes, that were not dewormed.

To successfully exclude, unwanted wildlife, in general, from accessing a water source, especially in an area where water can become scarce, will require a barrier.  Likely the reason you escaped as long as you did was the LACK of a fountain (the sound of moving water travels far in the quiet of darkness.

Either critter proofing the perimeter, or the pond itself will be needed IF you choose to continue it as a pond, assuming you do...

I agree with pond liners, great until a puncture, then, well, you are screwed. You may NEVER get one, or you may within weeks.

Some have success with lining the bottom with clay, usually works best where clay is naturally occurring - smear and layer and repeat until you are a few inches thick all around (sticks embedded to a certain height, all over to gauge depth, then pulled and filled/smoothed over).

Cement works for some, but runs the same issues as a liner, a failure may never happen, or a flaw will be present from the get go...

Rigid plastic "formed" ponds can work well, and are relatively easy to replace if there is a failure.

A buried old bathtub or other such container also can work, assuming the drain hole is suitably plugged; a kiddie pool sunk into the ground; all sorts of imaginative options. We inherited two "ponds" on our property, buried boat hulls, one plastic the other wood - don't know how old they are, but I've been here over 15 years!

My favorite though, a stock tank. Often cheaper than a rigid "pond form", sturdier than just about anything, designed for outdoor use, waterproof and easy to obtain. I would opt for plastic (I know, ugh) over metal, personally, but no reason either wouldn't work.

Protecting a pond is ideally done with a dog(s); but electric mesh, fence strands around the perimeter of the pond or "bird netting" (made of monofilament - fishing line) with 1cm squares, pegged taut several inches above the surface of the water. If applied in winter, spring growth will slide up through the openings and plants are generally not impeded. This provides a puzzling barrier as it is essentially invisible - so strength is not of particular issue, they feel the tautness, and with no "give" the predators are baffled. Unfortunately, this will also preclude birds and other wildlife you may WANT to encourage...

Conversely, ensuring the fence is climb proof (metal or electrified) will allow winged wildlife access, while excluding terrestrial animals.

Nice, I also would put a pond there if it were me.