Lessons Learned from Compacted Clay Liner

A highly plastic clay liner was compacted in the field with full‐sized equipment to an average of more than 100% of standard Proctor maximum dry density. The average field permeabilities of two sections of the liner, as measured with four sealed double‐ring infiltrometers and a $16\times 16\mathrm{ft}(4.88\times 4.88m)$ pan lysimeter, were $3\times {10}^{-5}$ and $10\times {10}^{-5}\mathrm{cm}/s\text{.}$ Laboratory permeability tests were conducted on samples compacted in the laboratory by three procedures, only one of which gave a reasonable prediction of the permeability of the liner. The high permeability of the liner was caused by the failure to achieve the two “basic” compaction objectives that govern the permeability of compacted clays. The basic objectives (destruction of soil clods and bonding between lifts) and 17 other key factors that influence the permeability of compacted clays explain the performance of the liner and provide a basis for understanding how to construct liners to avoid such high permeabilities.