A method of forming a polymer concrete CNG tank by forming an inflatable liner member composed of high density polymer impermeable to CNG； providing column forms as part of the liner member, the column forms having open tops and open bottoms and extending completely through the liner member； providing an outer form； positioning the liner member within the outer form with the column forms vertically oriented, the liner member being positioned to provide a gap between the liner member and the outer form； inflating the liner member； pouring polymer concrete about the liner member and through the column forms； and allowing the polymer concrete to cure. Reinforcement members may be positioned around the liner member and within the column forms prior to the step of pouring the polymer concrete.
