Design concept long term

The simplicity and robustness of the MARS design under long-term operation is ensured by an appropriate selection of the structural materials and by the incorporation of certain inherent and passive safety features in the original design concept. 

The bathtub effect occurs, in part, because most wastes have much higher hydraulic conductivities than the natural material into which they are placed they may also have very different unsaturated soil—moisture characteristics. The hydraulic conductivity of some wastes can be reduced by compaction. The bathtub effect also occurs because more infiltration enters the disposal excavation than would under normal undisturbed conditions. Trench covers may be constructed to achieve the desired hydraulic conductivity and to limit infiltration for the required period of containment or until compaction of the wastes occurs however, it is difficult to maintain the trench covers. The covers must withstand attack by plants, weather (freeze—thaw, wet—dry), erosion, and strains caused by consolidation within the trench. Most trench covers are not capable of meeting these demanding requirements without costly long-term maintenance programs. The cover should be designed to allow for expected consolidation and to utilize hydro-geological concepts of saturated and unsaturated flow systems present at the site. 

The relevance of the research agenda of IMPROVE has not fully been acknowledged by industry when IMPROVE got started. One reason for this lack of attention has been the business climate of the time. There has not been sufficiently strong economical pressure to reevaluate the design practice and to question the way design support tools have been used. Another reason for the limited attention of industrial practitioners is the focus of IMPROVE on fundamental and long-term research objectives which should result in novel concepts and methodologies rather than in prototypical tools to be demonstrated and evaluated by industry. 

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