405 / | HD | HYDRAULIC AND EARTH ENGINEERING |
52 | DF | FLUID CONTROL, TREATMENT, OR CONTAINMENT {7} |
53 | DF | .~ Fluid storage in earthen cavity {3} |
55 | .~.~ Cavity construction {2} | |
56 | DF | .~.~.~> Including cooling or heating of material surrounding cavity |
57 | DF | .~.~.~> Earth treatment {1} |