Oregon DEQ records are the most solid evidence that an oil tank has been removed and decommissioned. Buyers of any Oregon real estate become the responsible party for soil contamination at closing which makes finding out if there is/was an oil tank an important part of buyer due diligence during the inspection period.
I attended an oil tank locate that came up inconclusive today done by Alpha Environmental. There are supply lines in the basement which “proves” that once upon a time there was a tank but it could have been above ground in the basement our outside or buried. Portlandmaps shows a permit for an underground tank in this case (under historic permits tab). There is a concrete driveway up the side of the house that the furnace is on and the back yard is also impervious near the house.
The first step is a metal detector sweep around the property:
The next step was to hook this machine up to the actual supply line in the basement. There may be rebar touching the line as the machine pings all around the basement! Normally the trace of the pipe’s directionality would be clear.
Though inconclusive, the buyer is now possesses all the available information regarding the tank.