Many tanks were filled in place when they could have easily been removed
The tank to the left was located in a side yard, as you can see, a small excavator can access the area and did when this tank (that was previously filled in place) was required to be removed for a real estate transaction.
This tank had to be removed because when the tank was previously filled in place, no testing was performed. Buyers want testing to ensure the tank does not leak and
You see, when they filled the tank with sand, no one did any soil testing. The buyer, their mortgage company, and their attorney wanted to ensure the tank did not leak. The property owner had nothing that would satisfy this concern, requiring the tank to be removed with soil sampling. Funny thing is, the oil tank could have been removed when it was filled with sand, but the owner decided not to remove the tank.
This tank was filled with sand and was required to be removed when the property was sold, and again, the tank could have been removed originally, but wasn't.
Can you legally close a tank in place by filling it with an inert material?
Petroleum storage tanks, once cleaned, can be filled with an inert material, such as sand, concrete slurry, or foam. Once a tank is cut open and cleaned, it is technically no longer a tank as it can no longer securely store liquid contents.
By cleaning the tank, as per API standards (American Petroleum Institute), you are removing the possibility of the tank ever leaking in the future because you are removing all oil from the tank.
But how do you know if the closed-in-place tank leaked?
You collect soil samples and have them analyzed by an independent laboratory.
Just because you cleaned a tank and got a permit to fill it in place and the local government signed off on the permit, it Does Not Mean the Tank Did Not Leak. EVERY abandoned tank needs soil testing and a report explaining the test results and why remediation is not necessary, every tank.
The reason is that removing a tank is a few thousand dollars, whereas remediating an oil tank leak can be tens of thousands of dollars.
The photo on the left was a tank that was filled in place 15 years ago.
When it was removed, it was found to be leaking.
Remedial costs were $42,000.00, not including the cost of a new driveway.
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What does everyone want to know about an oil tank? People want to know if the tank leaked. Leaking tanks cost money to clean up. The way you know a tank did not leak is by obtaining soil samples. When a tank is being abandoned in place, how do you obtain soil samples from below a steel tank? 
You can cut holes, or the industry term, cut coupons in the bottom of the tank so you can access soils below the tank and obtain your samples. This practice has been followed for over 30 years, but the problem is that many tanks never had the testing performed when the tank was filled in place. These cases dictate that you reverse engineer the prior tank removal by removing all the prior fill installed, you reclean the tank, cut coupons, and obtain soil samples. The smart bulletproof approach is to obtain samples at the time of tank closure in place.
Why do you have to remove your filled-in place underground oil tank when you sell the property?
You have to remove the tank because you do not have a report with lab data documenting that the tank did not leak. You may have some papers, a permit, an invoice, a letter stating the tank was cleaned and filled with sand or foam, but you lack any cohesive document that would 100% state the tank did not leak.
In addition to cleaning and filling the tank in place, the outside fill and vent to the tank need to be sealed so that oil can no longer be delivered to the out-of-service tank. You must also backfill the area excavated to access the tank. Typically, a 4' by 4' area is excavated to safely access the tank top.
You are not alone; 40% of the thousands of tanks we remove every year are tanks previously filled in place. Now there are many people who had their tanks filled in place and who did not obtain soil samples, either because they got bad advice from the removal company, or they did not want to find a problem, or both. These tanks are a whole separate issue, which you can learn more about by clicking the following link: Tanks Previously Abandoned in Place
In summary, most tanks can be removed for the same cost as abandoning a tank in place. These are sites that have a tank in an accessible location, which is the vast majority of tanks. Now there are situations where there are obstructions that hinder the physical removal of a tank. Maybe you could remove these tanks, but oftentimes the math doesn't work, meaning it is just much more expensive to remove than abandoning the tank in place.
