Sewer vault for another house on our rental's land

[Vanessa Johns]

I have a newly built manufactured home on 0.6 acres in a rural area. The subdivision, however, has "city" sewer through a sanitation district. When I purchased the land I was told of an easement on the front edge of my lot for a sewer vault, which I incorrectly believed to be for the sanitation district to access it. This vault actually feeds from two lots adjacent to me and has nothing to do with the sewer lines from my house. Due to one of these two homes being listed for sale recently, I learned from the sewer inspector they hired that the vault was near full and could start leaking sewage, which would go directly into my lot and downhill towards the house. Upon contacting the sanitation district to file a complaint I was told they have no ownership of the vault and that it's the responsibility of the homes who feed into it.

While I know they are going to clean it out for the upcoming sale, I am anticipating an ongoing issue and a possible future health hazard for tenants if so. Has anyone experienced anything similar or have any good ideas for how to prevent an issue for tenants and protect myself liability-wise going forward? We did reach out to the state and were told to contact the county environmental health department, who just seemed confused and fairly worthless.

Thanks in advance!