I'm curious about this because we recently looked into buying a commercial property that had been flagged as potentially having contaminated soil.
Did your partner/investor recently purchase the property or have they owned for some time? We weren't able to get a loan on our property unless there was an extensive environmental study (Phase 2 IIRC) performed. The bank didn't want to loan on a property that would potentially have a cleanup cost higher than the property was worth.
I would encourage you NOT to be financially tied to the property unless the NC DENR says it's all bueno. Renting space essentially separates you from cleanup costs as long as you don't make it worse. Ownership however, changes that liability.
Food for thought.