As summer draws to a close we're already preparing for autumn here at digital.forest. Part of that is topping off our fuel tank for the backup power system. Our generator runs on Diesel fuel from a 5000 gallon tank. This is enough fuel to keep us running for over four days at full load. While we don't see storms such as the hurricanes that have caused such problems in the southeastern US, we have had the occasional stormy day and the traditional season for this kind of weather here in the Seattle area is October through early December. Our policy is to always start the autumn with a full tank. Our monitoring systems told us we were mostly full already, having only used a few hundred gallons over the summer during our monthly generator maintenance & exercise runs. The first step is picking a supplier for delivery. Diesel fuel is a commodity and we maintain delivery contracts with several suppliers. When you buy a commodity fuel in a non-emergency you buy on price. Sort of like when you are buying fuel for your car, you pick the station based on the posted price rather than what is first available. Our Facilities Manager, Kevin Teker places calls to check prices and schedules a truck based on the best buy of the day.

Our generator uses non-road taxed Diesel fuel, which is used in power generation, marine, and agricultural applications. This fuel has a bright red dye added to it to distinguish it from road-taxed Diesel. Ultra-Low Sulphur Diesel (ULSD) for road use is also dyed, with a bright green tint, while also being more expensive as it is taxed at the retail level. BioDiesel remains its natural color and appears, as you would expect as a honey-colored liquid. This short lesson in fuel types is here because it is important to us that the right fuel goes into our tank:

Above: Kevin Teker performs the "Bucket Test" before taking delivery.

The next step happens when the truck arrives. We take a fuel sample from the bottom of the truck's tank and put it into a light-colored bucket. This allows us to check its type as well as quality in several ways, looking for contaminations in the form of water, dirt, etc. Diesel fuel is less refined than gasoline, being barely beyond crude oil, so it is subject to contamination a bit more than gasoline. While we have excellent and flexible filtration systems it is always best to start with the best quality fuel available.

Once accepted the truck will hook up to the tank and fill it up. A sensor tells us when to stop pumping.

Above: Kevin supervises the fill up.

Today we took on only about 450 gallons. It is just good insurance however and we feel ready for the change of seasons.