Dreaded Oil is BACK - In my Water Well

Please see attached pic of my oil issue. This is my water tank buried in ground that stores water straight from my water well, before it goes inside into a number of filters. I have this buried tank because of having oil in my water - this way it vents off some of the fumes before going into every filter known to man. Anyway over the weekend I noticed that oil had seeped out the top of the holding tank. Apparently I had an influx/flow of oil and I guess because it was so foamy on top layer it didn’t shut off, or blocked the float from shutting off…causing it to spill out. I have a cap on the tank as you can see, of which about once every 4 months, or when needed, I drain the tank and get in and clean it. Usually it is greenish water with a small rainbow film on top, but occasionally it looks like this. The tank is 6’x10’. What I’d like I do is be able to get the oil off the top accessing thru the cap without having to get down in it. Does anyone have a suggestion for a product I could use that I could literally put down in the hold to scoop it off. This is in Bentonville/Cave Springs, AR.