The protection of groundwater quality against leachate generated by a landfill depends in part on the hydraulic conductivity of the underlying rock mass. If the bedrock is fractured, the permeability is largely secondary and the hydraulic conductivity of open fractures becomes the key factor. The Lugeon test is a good method to determine the relative hydraulic conductivity of fractured bedrock. In this article we report on an adaptation of the test for landfill sites and propose a rock mass classification based on water-take criteria. This classification complements the Spanish regulations that are currently in place. The study is based on 27 tests for inert and municipal solid waste carried out in three landfills that are situated in northern Spain: Meruelo in Cantabria, Zalla in Vizcaya, and Oyón in Álava.