One of the issues with a sand filter is that the filter media, i.e. the subsurface sand layers, often needs replacing. After a few years, sediment and hydrocarbons from the drainage area build up ...

If you were to build a house, what materials would you use ... which is essentially a mixture of sand, soil, and gravel compressed into "lateral forms," as per The Architectural Review).

They toss the dirt on conveyor belts, which carry the excess soil out of ... effective way to build a shallow subway tunnel beneath the city -- but it's much messier than using a tunnel shield.