GRI GM13 for HDPE geomembranes

Most buyers meet GRI-GM13 the same way. A specification arrives, or an engineer asks for a report, and the document is named without anyone saying what it is for. It is worth knowing before the enquiry goes out.

What the document is

GRI-GM13 is published by the Geosynthetic Institute and applies to high-density polyethylene sheet in both smooth and textured form.

Its reach is narrower than the title suggests. The document belongs to the factory rather than to the site, and a buyer who treats it as a site specification will be asking it a question it was never written to answer.

What you get from it, and what you do not

The value of the document is that it makes two sheets comparable. It names the test method used for each property and sets how often each test is run during production. Without that, one supplier can quote a density figure from one method and another from a different method, and the two numbers do not mean the same thing.

What the document cannot do is tell you anything about your own ground. The subgrade, the protection layer, and the seams fall outside it, and those are where lining work is usually lost. Independent guidance is explicit that a geomembrane is more susceptible to damage during installation than in service, and that is precisely the stage this specification does not reach.

So a sheet made to it is comparable with another sheet made to it. It is not thereby suitable for your site.

Why the boundary matters

The two thickness ranges should not be read as one. GRI-GM13 does not cover sheet thinner than 0.75 mm. A thinner sheet falls outside the standard’s scope; it has not been measured against it.

We also make sheet below that thickness, and we list it separately for that reason. If your design calls for a thickness inside the range the standard covers, the standard is the right document to specify against. If it calls for something thinner, say so plainly in the specification and expect the supplier to quote against that requirement instead.

Being clear about this costs a supplier very little and saves a buyer a great deal. A quotation that quietly implies a thin sheet meets a standard it sits outside is the kind of thing that only surfaces when the lining is already in the ground.

How a regulator uses it

The other half of the picture sits elsewhere. The Environment Agency’s landfill guidance reproduces manufacturing quality control tables from this standard in its appendix, which shows how a regulator uses it. The standard supplies the factory-side numbers; the guidance supplies the site-side rules around them.

Buyers who read both have the whole picture. Buyers who read only the standard have the half that is easiest to satisfy and least likely to be the reason a cell leaks.