COMPARISON OF 4 METHODS TO ASSESS HYDRAULIC CONDUCTIVITY

A hydraulic conductivity assessment that was conducted on four test pa ds constructed to the same specifications with soil from the same sour ce by four different contractors is described. The test pads had disti nctly different field hydraulic conductivities, even though they were constructed with similar soil, to similar compaction conditions, and w ith similar machinery. Adequate hydration time was key in achieving lo w field hydraulic conductivity. More extensive processing was another factor responsible for low held hydraulic conductivity. Four different test methods were used to assess the hydraulic conductivity of each t est pad: (1) sealed double-ring infiltrometers (SDRIs); (2) two-stage borehole. permeameters; (3) laboratory hydraulic conductivity tests on large block specimens; and (4) laboratory hydraulic conductivity test s on small specimens collected in thin-wall sampling tubes. The tests were conducted independently by each of the writers. After the tests w ere completed, the results were submitted and compared. Analysis of th e test results shows that the three large-scale test methods generally yield similar hydraulic conductivities. For two of the test pads, how ever, the hydraulic conductivities of the specimens collected in sampl ing tubes were significantly lower than the field hydraulic conductivi ties. Both of these test pads had high held hydraulic conductivity. Th us, there is little value in using small specimens to assess field hyd raulic conductivity.