Containment walls are built using 16-gauge or 22-gauge primer steel. Post are 2x3 14-gauge steel set 18” minimum in pre-mix concrete. Liner is a 16-ounce woven reinforced underlayment stabilized to resist degradation due to ultraviolet exposure. It is resistant to commonly encountered soil chemicals, mildew, and insects and is nonbiodegradable. We spray inside and out of walls with 40 mils of poly. 60 mils (average) of textured poly over the 16 oz reinforced liner on the interior for slip resistance.