At What Point Do I Pursue Legal Action? Or Is This Actually A Legal Issue?

Location: Oregon, USA

I have lived in a house for about 4 years now, it has a kick ass backyard... that I can't use.

When I moved in they had a section of the yard covered by a half fence that I couldn't really see behind, and as I was doing yard work I started going back there to clean where I found metal pipes knives tools tons of shattered glass (beer bottles, windows, pipes I think). The fence was removed, and the more I cleaned the more I found buried under layers and layers and layers of dirt, All throughout the yard, I think they just covered it up with mulch before we moved in..

I let the rental company and the owner know about it a couple of times in passing. Each time they verbally told me that they would send someone and something would be done about it, nothing happened. A year in I decided to finally write them about the verbal request I had made and they asked why I was only just now bringing it up to which I pointed out that I hadn't they sent someone he just picked up the top layer of stuff despite the fact that I told him it was coming up through the ground. They did nothing, I asked for more assistance, they did nothing. I can't just dig up my yard, I think that would break my lease, but also I'm pretty sure we have gas pipes and crap underground and I don't know how that works and I don't want to blow myself up.

Tonight, not for the first time I stepped on a piece of glass that came up out of the ground after a storm. I never go in my yard barefoot after the first several times I stepped on things and cut myself so I'm fine but this piece was part of a window or something and it's almost 2 ft long and basically looks like a big ass glass knife. I have contacted them again and I regularly attach photos of all the glass and metal stuff I'm finding, but I have zero faith that they will do anything.

I have not lived in the house since I was a very young child, I've lived in apartments pretty much forever, I don't know anything about any of this or what I should be doing. I can't even mow my own lawn without going out and digging through the ground first to make sure that I'm not going to hit some random rusty throwing knives (Yes I did find a set of rusty throwing knives buried out here) or something and end of accidentally Final Destinationing myself.

This is Uber specific I feel so if you happen to work at the company that I'm talking about, please fix my freaking yard, I'm sick of worrying my dog is going to stab herself every time she gets the zoomies.