Must originally have been the western continuation of foundation 5538.

Irregular blocks of basalt seem to be filling a foundation trench either for wall 5158 or for another unknown later wall. At least 7 of the blocks are re-used road paving stones (which are flat on one surface and worked to a rough point on the other side). This foundation abuts the bedrock. The cut of the foundation trench was not identified it may have been compromised by the backhoe used to open the area or the cut line maybe obscured by the edges of the basalt blocks themselves.