If rough or rocky ground is a concern, use a ground mat underneath your berm to help prevent puncturing the membrane. Our ground mat is made from a 30 mil reinforced PVC fabric that has over 600 PSI of puncture resistance. This mat will help cushion the berm from any sharp edges on the ground that might otherwise puncture the containment unit. Enviro-Guard Ground Mats are 2 feet wider and longer than the Enviro-Guard spill containment berm.