Storage tanks are classified as below ground if they have 10% or greater volume (including piping) beneath the surface of the ground. The requirements for above ground tanks are different.

Below Ground Tanks

Is the tank a septic tank containing household sewage wastes? Septic tanks are exempted from EPA and DEQ underground storage tank regulations.
Does the tank hold a maximum of 110 gallons or less?

Your tank appears to be excluded from EPA underground storage tank regulations. However buried tanks and/or associated piping can corrode, rupture, or otherwise leak and result in significant ground and drinking water contamination. Leaks that result in such contamination may pose liability issues including cleanup requirements and possible property devaluation. If you suspect a leak, notify the Idaho DEQ.

If you would like to conduct a self-assessment of possible risks associated with storage, tanks you can use Idaho Home*A*Syst.

Does the tank store heating oil for use on the premises of the farm or ranch where it is stored?
Does the tank hold a maximum of 1100 gallons or less of motor fuel used for non-commercial purposes?
Does the tank hold petroleum products such as motor fuel, waste oil, kerosene, or does it otherwise contain hazardous substances?
Your tank appears to be subject to EPA regulations and is required to be registered with DEQ. If your tank is not registered, you may do so by downloading the notification form and sending it to the Idaho DEQ.

Above Ground Tanks

Is the above ground tank used to store oil? ("Oil" includes, but is not limited to petroleum, fuel oil, sludge, oil refuse, oil mixed with wastes (other than dredged soil), and waste oil.)

Your above ground storage facility isn't required to have a Spill Plan (SPCC). We recommend, however, that you safeguard your facility, property, and any adjacent surface or ground water from losses of oil products. Experience shows that damages fom spills are long lasting and very expensive to clean. Prevention is the key!

Technical assistance is available from the Idaho DEQ. The EPA also has useful information on storage tanks on their site.

In the event of tank failure or spillage, could the contents of the tank reach any canals, drains, wetlands, streams or lakes?

Your above ground storage tanks and facilities appear to be subject to Federal Oil Pollution Prevention regulations which require the owner/operator to prepare and implement a spill prevention plan.

Information on Spill Prevention, Control and Countermeasures is available from the EPA.