trough deformation during grouting process the culvert being repaired should be cleaned prior to installing the rib and trough system of the invention any obstruction s such as any that protrude more than u215b u2033 from the inner surface of the culvert any loose pipe pieces and any solid objects should be removed if the host pipe 1 has become oval or weakened because of structural deformation it should be repaired before the rib and trough installation is begun as shown in fig1 temporary supports 2 can be used to secure the culvert under repair troughs should be laid out before the ribs are installed also if the bottom of the host pipe is damaged sufficiently it might be necessary to add cementitious grout or other filling material to the hot pipe as indicated schematically by reference numeral 8 in fig8 the troughs can have lengths of four or eight feet and can be cut for shortening as needed and can be abutted end to end to accommodate the length of the culvert that is host pipe in need of repair in the case of a culvert in the form of corrugated metal pipe cmp supports from closed celled polyethylene foam foam sealer should be placed in the pipe under the curved edges of the troughs as would be done as shown in fig2 such foam sealer can be adhered to the crest of the cmp as a close loop the rib can then be transported into the pipe in some cases the ribs are disassembled for easy access the repair.