The ornamental design for a transportable trapezoidal storage tank, as shown and described.
FIG. 1 is a left side perspective view of a transportable trapezoidal storage tank, the truck shown in broken lines are for illustrative purposes only and form no part of the claimed design;
FIG. 2 is a top view of the transportable fluid storage tank of the present invention;
FIG. 3 is a rear view of the transportable fluid storage tank of the present invention, showing the trapezoidal shape of the present invention and the addition of a rectangular sump on the bottom of the tank;
FIG. 4 is a left side view of the transportable fluid storage tank of the present invention; and showing the sump positioned on the bottom of the trapezoidal tank; and,
FIG. 5 is a view looking up at the bottom of the transportable fluid storage tank, showing the location of the rectangular sump, of the present invention.