You'll remember to close it after your first EPA fine. They like to start around 10k, less than that isn't worth getting involved. I had a friend who drove for FedEx, and drove over a broken pallet someone had dropped on the highway. A piece of it hit his fuel tank just right to rip a hole in it. Luckily, some other trucker passing by saw his predicament and stopped with a spill kit. Putty on the tank, absorbent pads, diatomaceous earth, the works. This happened in California next to a protected wetland area. He was later told if the fuel has gotten off the road surface, or he hadn't taken protective steps that he would have been personally fined 100k and the company would have been fined 1M. His company had spill kits in every truck a week later. A lot of the laws will protect you from fines if you take measures to stop the fuel from leaking. If you drive a sleeper, and don't have a spill kit, sacrifice your bedding. That $100 mattress and whatever your blankets and pillows cost could save you tens of thousands of dollars in fines. Drive safe out there and protect yourselves.