Holding the anchor by one earthened wall is simply a matter of analyzing the passive pressure available is enough to hold the factored tension or the capacity of the cable under worst conditions, that may include the anchoring wall being submerged and some load surcharge exist creating active push in the other side of the anchoring wall.
Ideally you would place out the anchoring wall beyond the passive pressure wedge, but if not, at least upwards of the perpendicular to the limit of the active push wedge by the point where such limit of the active push wedge meets the surface (I assume horizontal surface).
In the ARBED manual for sheet piling (I have one old spanish edition) you have examples.
