Filling in an old cesspool

We discovered a pretty large void under our grass and a "sinkhole" has started to form in the grass... It looks to be about 4 ft deep and 5-8 ft wide. My neighbor who owns a landscaping business looked at it and said he thinks it's probably an old cesspool from the 70's (we have sewers). Has anyone dealt with something like this, and how did you address it? Can anyone recommend someone who they had excavate and fill it in? You wouldn't go through homeowners insurance for something like this, right? This is the first big house issue we've had and newish homeowners, so any advice is appreciated!!

Filling in an old cesspool

We just had a new cesspool and dh filled in the old one and overflow himself. It does settle a lot so he needed a lot of extra fill to account for that. I would probably call a cesspool company if you want a professional to deal with it.

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