Layer S of preserved glariat road surface 4027 and N of basalt paved stretch of road 4010. southernmost part of SU extends under basalt pavers and is clearly a preparation level for the road--comprised of compact soil with numerous yellow tufo inclusions. Same preparation layer is visible in bottom of basalt paver robbing trench 4043. Rest of SU most likely consists of several episodes of destruction of the road surface and/or road preparation--orange tufo (preparation?) basalt slabs (preparation or paving?) and a compact layer with basalt and tufo cobbles (preparation of earlier glariat?). Stratigraphic relationship to be clarified in 2012. *Layer not excavated in 2011 or shot in in 2011