Wetter Is Better?

Wetter is better?  For those involved in the construction of waste storage ponds and treatment lagoons, that means a well designed, fully functional soil liner that meets minimum admissible thresholds.  The influence of initial water content at which a sample is molded affects the hydraulic conductivity.  When saturated, permeability can vary by several orders of magnitude if the initial water content is changed a few percentage points.  Soils compacted above optimum moisture content (wetter) generally have lower permeabilities than when compacted dry of optimum moisture content for the same density. This has been well documented in literature, as well as in tests taken at NRCS’s geotechnical laboratories in Lincoln, Nebraska and Fort Worth, Texas based on results using state-of-the-art flexible-wall permeameters.  This is a much different recommendation than in testing of road fill or dams where compaction characteristics are perhaps of greater importance than the moisture content at which the soil is molded.  Appendix 10d in Part 651 of the Animal Waste Management Field Handbook provides excellent guidelines and design considerations when using a compacted soil liner.
Your contact is Jody Kraenzel, NRCS civil engineer, at 402-437-5337, ext. 113.