The existing liner is dug out, cleaned and inspected, then welded to the new sheet, usually by extrusion because exposed sheet is oxidized and often dirty or textured. Tie-ins are often the hardest seams on a job and get extra testing and destructive samples. Old sheet that has aged badly or stress cracked can make a sound tie-in impossible without replacing a strip of it.
Tie-in to the old cell is all extrusion, so grind back to fresh black before you lay a bead.
Also heard as
- tie in
- liner tie-in
- cell tie-in
Related terms
Extrusion weld
Geomembrane seam made by laying a bead of molten polymer along the edge of an overlap, used for patches and details.
Grinding
Lightly abrading geomembrane before an extrusion weld to remove the oxidized surface and dirt.
Stress cracking
Brittle cracking of polyethylene geomembranes under long-term tension well below their yield strength.
Destruct
Installer shorthand for a destructive seam sample, and for the job of cutting one out.