Shallow land burial is the most common method for disposing of industrial, municipal, and low-level radioactive waste, but in recent decades it has become apparent that conventional landﬁ ll practices are often inadequate to prevent movement of hazardous materials into ground water or biota. Most waste repository problems result from hydrologic processes. When wastes are not adequately isolated, water received as precipitation can move through the landﬁll cover and into the wastes. Presences of water may cause plant roots to grow into the waste zone and transport toxic materials to aboveground foliage. Likewise, percolation of water through the waste zone may transport contaminants into ground water.
In semiarid regions, where potential evapotranspiration greatly exceeds precipitation, it is theoretically possible to preclude water from reaching interred wastes by:
The Protective Cap/Biobarrier Experiment (PCBE) was established in 1993 at the Experimental Field Station, INL Site, to test the efﬁcacy of four protective landﬁll cap designs. The ultimate goal of the PCBE is to design a low maintenance, cost effective cap that uses local and readily available materials and natural ecosystem processes to isolate interred wastes from water received as precipitation. Four evapotranspiration (ET) cap designs, planted in two vegetation types, under three precipitation regimes have been monitored for soil moisture dynamics, changes in vegetative cover, and plant rooting depth in this replicated ﬁeld experiment.
From the time it was constructed, the PCBE has had four primary objectives which include;
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