The DOE Grand Junction Office is evaluating long-term performance of landfill covers. The goals of the study are to improve continuity in inspections of cover performance, to project long-term changes in disposal cell environments, and to provide performance data for future cover designs. Other objectives are developing a consistent approach for cover inspections and performance evaluations and linking performance evaluations to contaminant release processes, risk, and stewardship. Saturated hydraulic conductivity of Uranium Mill Tailings Remedial Action Project covers is being investigated, as it was a primary criterion for intrusion control in the original designs. Plant root intrusion and its effects on the conductivity are uncertain.
Plants play a role in the long-term water balance.
Rapid measurement of foliage amounts is needed to evaluate evapotranspiration. Radiometric methods for estimating foliage have been evaluated at Lakeview. Plant ecologies are also being studied to determine the effects of gravel layers in the cover design, where gravel and plants were used for erosion control. Regulatory performance requirements may specify hydraulic conductivity values, but the conductivity may change with time. Leaf area indices may be more important than the percent of plant cover in predicting cover conditions.