I put in a septic system for my kennels years ago. It is a regular system like those installed for homes. It worked fine in the beginning but now it seems the waste is just building up. The cover has disintegrated over time allowing rain water to enter the tank causing the surrounding yard to become muddy and water filled. I did place something over it to try and alleviate further issues. I physically pick up all the waste myself since it is not working properly. I am at my wits end... the catch basin is filling up and with all the rain here in the south along with the heat it surely is a nasty mess.

You probably need to get it pumped out and then find a proper lid for it to keep rain water from getting in.

I'd love to help, and I am an expert in the pet forum, but this question really has nothing to do with dogs, so I have no advice.

I've asked the mods to move your question to a different forum, one where there are experts about septic systems.

I hope you get it all worked out.