Original contract was to rough-grade the site to the proposed elevations to drive 97 wood piles. Excavate for and install concrete footers, foundations and slabs. Install sanitary sewer, storm sewer, domestic water, city sidewalks and curbs. However the pre-construction procedures missed a pre-existing factory that was demolished and covered up. Therefore, in addition to our original scope, we devised and executed a plan to remove the buried building debris, excavate to virgin soil (and remove debris) in proposed pile locations. Then screen excavated material to use as controlled backfill in pile locations, prior to executing our original scope.