To apply a plastic concrete cut-off wall has been one of the most suitable solutions in order to control and minimize the seepages leaking under the dams bodies. Plasticconcrete cut-off walls are used in height soil dams which have an improper and heterogeneous construction site and their cut-off operation of the dam foundation usestypical approaches such as comment grout in ejection and so on (and the result doesn’t seem to be satisfactory). GOTVAND OLIA is one of those dams that the cut-offwall has been used there. There is an unstable and crashed zone in the right bank andit seems possible to create a crack in the cut-off wall due to a possible land slide Inorder to amend and boost the cracked cut-off wall, there have been considered aseries of Galleries in the lower hand of the dam body along with the dam core to let us inject the efficient grout through them in the cracked location. As the injectionoperation won’t be possible so fast during an earth quake and it’s also possible that the clay core is washed away due to the penetration water flow, and this canjeopardize the general stability of the dam, so the GEOMEMBRANE sheet wasexecuted as it gives stability to the wall. Traditionally, the sheets were installed to 40 meters deep and deeper than this has been too difficult. The execution of theGEOMEMBRANE in the depth of 99 to 125 meters in the cut-off wall of GOTVAND dam has been a unique approach in dam construction. GEOMEMBRANE is set on a rolling steel pipe (steel cylinder) which is mounted on a stand and it would beinstalled by using a mesh steel plate and steel cables (on the upper hand of the cut-off wall).In this article, the reasons for the selection of the GEOMEMBRANE and theproper executive solutions in order to be installed in the cut-off wall would be presented.