What is the minimum soil depth between the high groundwater table and the bottom of an earth pit privy?

• A. 600 mm
• B. 750 mm
• C. 900 mm
• D. 1200 mm

Answer: (C)

The key idea is protecting groundwater by keeping a sufficient layer of soil between the pit and the water table, so waste effluent is filtered and does not reach groundwater during fluctuations.

Having at least 900 mm of soil between the bottom of an earth pit privy and the high groundwater table provides a reliable buffer. That thickness lets the soil act as a natural filter, slowing and attenuating contaminants, while also giving space for seasonal rises in groundwater without the pit bottom contacting saturated soil. This separation helps prevent groundwater contamination and supports the structural stability of the pit as water tables move.

If the soil layer were thinner, groundwater could come into contact with the pit contents more easily, increasing the risk of contamination and compromising the pit’s integrity. A deeper separation could be more protective, but the standard minimum specified is 900 mm.