Soil permeability assessment for feedlots

Summary

The feedlot industry has been pro-active in developing and adopting appropriate guidelines and codes of practice for environmental management. Clay liners are relatively impervious barriers used to protect groundwater from potential contaminants present on the feedlot pad and in feedlot effluent stored in holding ponds. Current feedlot guidelines state that clay liner materials should have a maximum hydraulic conductivity (Ksat ) of 1 x 10-9 m/s.  
This project collected a representative sample of soil types from the major lot feeding regions of Australia and assessed them for a range of engineering properties, including Ksat at various compaction levels (98%, 95% and 90% of maximum dry density). A range of different percolation fluids were also employed, including distilled water, which is the standard used in commercial laboratory tests, and feedlot pond effluent.
The majority of soils achieved the soil classification and plasticity criteria stated in the National Guidelines for Beef Cattle Feedlots as being suitable for use as a clay lining. Only five soils achieved a hydraulic conductivity at or just below the accepted maximum of 1.0 x 10-9 m/s. When feedlot effluent was utilised as the percolating fluid, improved results were achieved (i.e. soils were less permeable) . However, the characteristics of feedlot effluent restrict its use as a percolation fluid for most soil testing laboratories.