Abstract: A mobile fluid storage tank having a base, a substantially vertical front wall, a substantially vertical rear wall, a pair of substantially parallel vertical sides walls, and a roof. The roof has a rear roof portion and a front roof portion. The rear roof portion extends across the rearward portion of the side walls, while the front roof portion is comprised of two different portions, a sloped portion and at least a two-stepped portion. The sloped and step portions are substantially parallel to each other. The stepped portion is comprised of at least two steps. The storage tank also has an inclined stairway attached to the front wall and extending from the stepped portion adjacent one side wall downwardly to the base portion adjacent the opposite side wall.