Abstract: A single step, bi-level portable storage tank which includes contiguous forward and rear generally rectangular liquid storage sections each having side walls and having a common bottom wall, the forward storage section having a lower roof than the roof of the rear storage section. A forwardly facing break wall joins the forward end of the roof of the rear storage section to the rear of the roof of the forward storage section at a location which is about one-third of the distance from the forward end of the tank to the rear end thereof. A ladder and stairway at the forward end of the storage tank accesses a rearwardly extending walkway which crosses the roof of the forward storage section to the break wall.