The ornamental design for a paired side portal structure for a water distributing chamber, as shown and described.
FIG. 1 is a top and side perspective view of a paired side portal structure for a water distributing chamber showing my new design, and further showing in phantom outline a water distributing chamber for illustrative purposes only and form no part of the claimed design;
FIG. 2 is an end view thereof;
FIG. 3 is a top view thereof; and,
FIG. 4 is a side view thereof, the unshown opposite side being of identical appearance.