Should be the station of the centroid of the embankment area on the diagram. AutoCad has a command which can find the centroid point in a given area. Or without computerized assistance - cut out the area on paper. Take a pin with a string hanging from it. Stick it through the paper into a wall. Trace the hanging string. Stick it through again in one or two more places and trace it. The intersection should be the centroid.
