A portable tank assembly that is movable between an operating position and a transport position that includes a tank assembly with a holding tank having an upper section that includes an upper wall and a lower section that includes a lower wall that tapers inwardly from the upper wall to form an orifice, a transport assembly that includes a base portion and an axle assembly. The base portion is affixed to the upper section of the holding tank, and the axle assembly includes wheels for transporting the holding tank along a surface, and a skid assembly that includes a skid plate configured to rest on a horizontal surface when the portable tank assembly is in the operating position and a plurality of legs connecting the skid plate to the holding tank.