(c) The results of a shear test conducted, in accordance with ASTM method D5321, which is incorporated by reference, on the soils and geosynthetic materials selected for use in construction of the liner system and the final cover system. The test shall be conducted using wetted soil and geomembrane interfaces. The shear test results shall be used to evaluate the stability of the geomembrane component over the clay component and the drainage layers and overburden placed on the geomembrane component. For designs which utilize a GCL, the shear test results shall be used to evaluate the stability of the geomembrane component over the GCL component and the soil barrier layer and the drainage layers and overburden placed on the geomembrane component. Wet unit weights of soils shall be used in analyses. If all soil and geosynthetic materials to be used are identical to those that were tested for a previous construction phase, then the test need not be conducted again. The department may waive testing of materials which are proposed exclusively for use on liners or final cover systems with slopes of less than 10 percent. Note: Copies of the ASTM D5321/D5231M-20, "Standard Test Method for Determining the Shear Strength of Soil-Geosynthetic and Geosynthetic-Geosynthetic Interfaces by Direct Shear," revised 2020, are available for inspection at the Department of Natural Resources, 101 South Webster St., Madison, Wisconsin 53703; and the Legislative Reference Bureau, 1 E. Main St., Ste. 200; Madison, Wisconsin 53703; and for purchase at http://www.astm.org.