Soil Centrifugal Permeameter™ System

Description & application

Municipal solid and hazardous waste landfill sites are commonly constructed utilizing engineered hydraulic barriers (often compacted clay liners) that minimize the transport of hazardous contaminants from the waste mass into the natural environment. Typically, legislative guidelines require that compacted soil liners have a hydraulic conductivity that does not exceed 1 x 10 -7 cm/sec. Current state-of-the-art laboratory testing techniques for materials with such a low hydraulic conductivity involves off-site, time consuming (anywhere from 5-14 days per sample), and costly test procedures (e.g. ASTM 5084-D). Consequently, hydraulic conductivity testing often represents a bottleneck in the construction of landfill sites which often unfortunately results in a minimum of direct hydraulic conductivity measurements to ensure that hydraulic compliance of the compacted soil liner is achieved.

The newly developed and prototyped flexible-wall centrifugal permeameter utilizes a unique sample chamber configuration that allows for leak-free representative (i.e. sample is not further compacted by the operation of the device) hydraulic conductivity assessment of compacted soil samples. The device can also be configured to include sensors that allow a user to monitor a number of real-time operating characteristics, such as pressure changes on the sample and permeant volume changes. This new flexible-wall centrifugal permeameter facilitates rapid sample testing (typically 8 to 12 hours at low gradients) and allows for expanded and more thorough compacted soil liner hydraulic compliance monitoring during landfill construction. The apparatus could be offered either as a low cost large volume testing service, or as a premium cost service due to the speed at which results can be obtained. The design of this new permeameter is also robust enough to be adapted for portable or mobile use for on-site real time testing situations.

Stage of development

A first generation prototype of the permeameter has been completed, tested, and validated against a triaxial permeameter. A second generation prototype, including advanced instrumentation is under development and will be field tested.