Arvinolga,
You did not mention the system size, but the choice of tank style will be very dependant on how much fuel you need. If this is an office building as you state, then I imagine the system is quite small. If the genset size you need only needs to feed egress lighting and egress pathway lighting for 90 minutes, then you can probably get away with a packaged system utilizing a skid mounted tank below the genset, or at worst case a concrete, dual walled, fire rated tank such as made my "ConVault". Althought that does introduce pumping and piping, monitoring and spill control. Which will involve Mechanical and Civil/Architecural design.
If the syatem is large, such as one we are currently involved with. Which is the second phase of the construction of a generator plant feeding a large hospital complex in Los Angeles, California. The initial phase included three-2MW gensets, with diesel fired engines generating at 12 kV. We are in the process of adding two more. These are on a closed transition switching scheme with the utility which will be adding a 66 kV-12kV substation.
The site is extremely crowded, there would be no room for above ground storage and having 100,000 gallons of diesel fuel in tanks above ground is not only a physical and safety concern, it is an eyesore the County and the Architect would hang us for. The initial two tanks are underground and have presented no problems whatsoever. We have dozens of installations using Underground tanks. The leakage monitoring of the interstitial spaces, fuel piping, man-wells, etc..., is a well regulated and common installation.
Our Mechanical/Plumbing engineers are well versed in fueling systems, the piping, pumping, monitoring and fuel management systems are part of their daily routine. I suggest Arvinolga, that you contact a local Mechanical consultant and hire him to assist with the design. It is very possible to get a depandable, safe, environmentally friendly design with underground tanks.
