The health department should test the water that is seeping from the house and condem if the septic or sewer is leaking. If the house is a nusiance you may sue the neighbor to stop the activity but it would take some time and money to get the final orders.
You should also file a claim with your insurance for any damage that is occuring and get a contractor who has dealt with drainage issues to give you a bid.
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The RLTA has a provision whereby you notify the owner of the waste/nuisance/trespass issue and demand that they fix the situation. If they do not fix it, you sue them. You can find out who the record owner is by consulting the County's tax records; the assessor-treasurer will have an address for the owner, so you can write to them. This is public record, so you are entitled to the information so you can bring your complaint to the correct party - the owner.
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