The oil is pollution and seeps into the soil, possibly the groundwater. 

Or, is someone just tired of the signs, which are illegal in some communities, may be illegal without first paying for a permit, or simply considered a nuisance by someone living or working in the area and you are polluting their neighborhood in their mind?

Whereas with a regular purchase, you'd have this done up front and know in advance of purchase whether there are serious environmental problems.

The unit has also been tested for environmental issues and moisture was below "dry levels" and indoor air quality levels were okay though CO2 levels were just above guidelines in some rooms.The tenant is known to use a lot of candles, we're wondering if this could cause this.Does anyone have any ideas?

@Sonia Spangenberg If the city is giving you issues, you could ask them if you gave them an environmental report showing that the land is safe and added septics is doable and won't harm the water table that might get them to calm down. 

Ranch land, farm land, land with preservation easements or environmental easements, land for wildlife, water, air, mineral rights of land, land for development and subdivision, and general land use of all kinds.

(*Note: we waver on the slightly neurotic side when it comes to environmental health - I'm sure most people would be totally fine living in this county, plus our soil tests showed totally normal levels of heavy metal exposure.  

Pollution dropped, outside litter reduces, plastic bag reduction etc.

If YOU do it you should clean up the mess you made.On the access issue I agree with a prior post to try your local gov'ts shade tree/environmental dept. for input.

Some state environmental divisions are trying to shut down Wells for communities because of thee a safety factor and communities cant afford the chlorine and treatment that a community well needs..I'd forget this deal If I were you.