ABSTRACT
It is relatively easy to modify soils during cover construction; some modifications are unintended, and some of them may degrade the quality of the soil. It is also easy to add major plant nutrients-nitrogen, phosphorus, and potassium-to the soil placed in the ET cover, and to adjust low soil pH. Soil density may be controlled within an optimum range during construction. However, modification of properties such as high pH, excess sodium, or very high total soil salt may be impractical. Soil modification to improve its quality costs relatively little when compared to the total construction cost, but it has the potential to improve performance, lengthen life of the cover, and to reduce long-term maintenance costs.
