Q.: We need long-term storage for large quantities of materials that can't be processed immediately before making them safe for discharge into the natural drainage of the area. Where did I see a description of a method of building reservoirs to hold hazardous wastes using soil-cement and some kind of membrane?

A.: A 1-page article, "A New System to Contain Hazardous Wastes," with one photograph and one diagram, appeared on page 662 of our July 1984 issue. The system involves using two 6-inch layers of soil-cement with a 30- or 40-mil layer of high density polyethylene between them. It is reported that water solutions pass through the soil-cement at a rate of only 0.1 foot per year, so only a small amount of hazardous waste can even reach the polyethylene membrane in a year's time. Construction costs by this method are reported to be competitive with comparable lining systems.