The standard mandates two concentric rings, typically constructed of steel or hard plastic.
: Two concentric rings—usually a 12-inch (300 mm) inner ring and a 24-inch (600 mm) outer ring —driven into the soil to a specific depth. astm d338518 pdf
One famous anecdote from the 1990s: a landfill liner design in Florida relied on lab permeability tests showing clay was nearly impermeable. But field tests using D3385 found infiltration rates 100 times higher—because natural cracks and wormholes existed. The design was changed, preventing a major groundwater contamination risk. ASTM publishes D3385-18 (DOI 10
The 2018 revision (D3385-18) clarified procedures for different soil types, added guidance on test duration, and emphasized the importance of maintaining constant head (water depth) during the test. It also addressed common errors: ring-driving disturbance, evaporation, and temperature effects. One famous anecdote from the 1990s: a landfill