A composite liner has been developed for use in impoundments of hazardous wastes. It consists of high-density polyethylene membrane placed between two 6-inch compacted layers of soil-cement. The high-density polyethylene has the unusually high laboratory test elongation of 700 percent. Furthermore, it is highly resistant to puncture. The other material of the system, soil-cement, is virtually impermeable: water passes through it at the rate of about 0.1 foot per year. The in-place construction cost of this composite liner is competitive with comparable lining systems. The liner offers a high degree of reliability against seepage, it is durable, and it provides a firm working surface. It produces more impoundment storage volume than conventional thicker lining systems being used today and is expected to have long life.