An apparatus for protecting against environmental contamination at a drilling site is disclosed. The apparatus is used to form a perimeter around the drilling site, the interior of which is covered by a geomembrane. The portion of the geomembrane found along the perimeter is placed in the groove of the apparatus's base. A key block is then fit into the groove, thereby holding the geomembrane in place by the tension created between the base and the key block. At those perimeter locations that will be traversed by vehicles and equipment, two ramp pieces replace the key block in holding the geomembrane tight against the base.