Oil tanks were very common between the 1920s and 1960s to store the relatively cheap heating oil for the oil furnace. If the home has exchanged hands a few times the underground tank may not be known about. The presence of oil tanks is an issue that can rear its ugly head on an inspection every now and then. Thankfully the Oregon DEQ is doing something to help.
The Department of Environmental Quality (DEQ) here in Oregon, has a program to help keep track of those oil tanks that may have been forgotten.
However this site is tricky and you should go to my later post for a better explanation on how to preform a search:
If excavation or redevelopment is planned you can find information on known and suspected Heating Oil Tanks (HOT). Information on: if the site has received a closure letter for the decommissioning, assessment and certification of a HOT is available.
If a HOT is present there may be contamination of the surrounding area and a cleanup may be required. Decommissioning, assessment, and cleanup must be performed by a DEQ licensed HOT Service Provider.
For you agents out there check out this publication: What agents should know about underground oil tanks.