Simulations of infiltration of meteoric water and contaminant plume movement in the vadose zone at single-shell tank 241-T-106 at the Hanford Site.

摘要

Contaminant plume migration in the vadose zone from a leak at Tank 241-T-106 on the Hanford Site was modeled to determine the effect of coarse backfill covers on the infiltration of meteoric water and the subsequent transport of contaminants. Infiltration through the upper 2 m of soil cover was simulated for the period of 1947 to 2020 using hydraulic properties estimated for the backfill sediments. The Tank 241-T-106 leak was simulated for the period 1960 to 1990 using an infiltration average of 77 percent of precipitation. The results of the simulations indicate that increased meteoric water infiltration because of the presence of coarse surface sediments increases the rate of movement of (sup 106)Ru. The simulations show the (sup 106)Ru plume approaching the water table in the early 1980's, but subsequent radioactive decay appears to preclude the plume from moving into the saturated zone. The simulated (sup 137)Cs plume migrates considerably less distance than the (sup 106)Ru plume because of greater sorption. The increased plume mobility compared to previous simulations at lower infiltration rates implies that remedial action, in the form of an infiltration barrier, could be an effective means to inhibit the movement of the plume. 22 refs., 19 figs., 7 tabs.