Usually, only heating oil USTs associated with commercial properties are regulated. thus, most home heating oil tanks may and often are taken out of service without any oversight from state regulators.Second- the rules that are in effect for heating oil tanks are usually less stringent than for diesel or gasoline tanks since heating oil tends to thicker and may not migrate as far. as a result, many states just require tanks to be cleaned out. they may also require the tanks to be filled with sand or concrete to prevent collapse. but sampling may not be required.Third- the key to determining if a tank has leaked is to collect soil samples from around and beneath the tank (groundwater also if groundwater is shallow). another quick way to see if a tank is leaking is to "dip" it with a stick that has a paste that turns color in the presence of water. generally, if water has gotten into a tank, it can mean oil has leaked out of the tank (although a certain amount of condensation may be present even where there is no leak so this is not a infallible test).Fourth- if there is currently a tank in the basement, ask the owner if there used to be a buried tank (a/k/a underground storage tank).Fifth, If the tank has impacted the soil, the cleanup generally varies from $25K to $50K though the costs will depend ont he depth of the contamination. i once had a home with a heated pool that had pressurized piping and used diesel. the contamination went down 40 feet and the consultant went crazy excavating the soil to the tune of $400K!!!

The realtor is saying we can get a price adjustment but a soil delineation/ground water testing has to be carried out for me to come up with even a conservative number to protect me.

Example: We recently had a plot of land under contract and while walking the land discovered that a corner portion of the lot was wet from the ground water runoff of a new development above it.

If its real bad you may need a hydrogeologist, a person who studies the ways that groundwater (hydro) moves through the soil and rock of the earth (geology) or a hydrologist, someone who studies surface water.You will most likely want a HAZMAT spill team to asses the situation and provide clean up.

If it is running all the time there is simply too much ground water - this is the problem I am having.If your pumps not running, but your wall is wet, perhaps the water is not reaching way down to your drain tile.

Usually it's because there is lake water or drinking water or groundwater degraded that can be contaminated by septic or your project. 

Prepares offers to purchase or purchase agreements, listing contracts, agency disclosures, real property residential and agricultural rental agreements, real property commercial rental agreements of one year or less, and groundwater hazard statements, including any modifications, amendments, or addendums to these specific documents.Iowa Code Section 543B.3.  

The furnace is hooked up in a dangerous way to an exterior above ground water tank being used as an oil tank.

Mold was caused by shallow groundwater/excessive rain last winter.

Once you know the reason(s), for the flooding, then you'll be able to figure out a solution.I'd also strongly suggest that you don't re-finish the basement until you've determined the cause of the flooding and fixed the problem (last thing you want is to re-finish the basement, and have it all ruined again by another flood).I'd suggest first watching some videos on youtube on flooding, drainage, groundwater, french drains, sump systems, water catchment systems, etc, just to give you a better understanding on what can cause flooding, and what types of fixes might work.