Tiling With Frozen Ground

This is a picture I took today of a field that was tiled recently. Notice there was a quite a bit of frozen ground but they were still able to pull the tile plow through the field. On Tuesday my contractor finished tiling one of my fields. He said the frozen ground was about one foot thick but it was not real hard. Even the backhoe had no trouble breaking through the frost. Of course it was a big backhoe too!