That seems like way too much to me. I have a buried oil tank. I think it's 500-gallons (bought the house at the end of July). It was full as of August 1. It still had 185 gallons in it as of a couple of weeks ago. And I live in Alaska as well. It seems to me that I'm burning maybe 100 gallons a month, maximum.
If you have a leak, you'll want to be quiet about it and clean it up yourself. I worked for an environmental engineering company for years, and that is mostly what I did. Clean up and monitor fuel spills. If you reported this to your state environmental agency, the cost of their cleanup could exceed the value of the property.
Find out if you're leaking. Rent some equipment and excavate the tank if you are. Overexcavate the contaminated soil and install a new tank with secondary containment and leak detection. If you have property, you can place the contaminated soil on a liner and churn it over every couple of months to let the fuel evaporate out of it (which will take several years, potentially).
Anyway, good luck. I'm paranoid about leaking fuel tanks....