filter underdrain
1underdrain — I. ˈ ̷ ̷ ̷ ̷ˌ ̷ ̷ noun Etymology: under (III) + drain : a concealed drain with openings through which the water enters when the water table reaches the level of the drain an underdrain below a filter bed II. | ̷ ̷ ̷ ̷| ̷ ̷ transitive verb : to… …
2environmental works — ▪ civil engineering Introduction infrastructure that provides cities and towns with water supply, waste disposal, and pollution control services. They include extensive networks of reservoirs, pipelines, treatment systems, pumping stations …
