The widening of the I-66 westbound lanes and the associated bike/shared use path required the construction of multiple retaining walls. Due to the required wall heights and existing right of way constraints, a double post and panel wall was designed. The wall system consists of an upper wall portion that supports a noise barrier and a lower wall portion separated by the shared-use path. Due to significant wall and soil-structure interaction due to the relatively small distance between the upper and lower walls, the FEM (PLAXIS) was used for the design and to limit wall displacements.