This is a geometry design and surveying problem. The reference point of the abutment/wingwall must be tied to a station, or a bench mark, same as the roadway alignment itself. The abutment can't be refer to a floating point without bearing and elevation. For structural design, we need two reference points to determine the bridge length, and slop. And for construction, the reference point is required to layout the foundation/structure correctly, and for grading.