Thus, a remedy evaluation needs to include the unique conditions of this perched-water zone. As a result, residual contaminants remaining after pumping is no longer effective needs to be addressed with post-extraction mitigation approaches, appropriate monitoring, and selection of suitable remediation endpoints. However, water extraction will become more challenging as the perched unit dewaters. Currently, a pumping system is used to remove contaminant mass from more » the perched-water zone. This perched-water zone contains several million liters of water contaminated with high concentrations of uranium, technetium-99 (Tc-99), and nitrate that serves as a continuing source of contamination to the underlying aquifer. At the 200-DV-1 operable unit (OU) at the Hanford Site, a key feature is a perched-water zone. These practices distributed contaminants in the subsurface, some of which are currently in the vadose zone above the groundwater. Department of Energy's Hanford Site, liquid-phase waste was discharged using surface disposal features such as ponds, trenches, and cribs. Thus, contamination that will remain after pumping needs to be addressed with post-extraction mitigation approaches along with appropriate monitoring and selection of a suitable remediation = ,Īt the U.S. Water extraction cannot remove all of the contaminant mass from this zone, nor can it stop the recharge-driven flux of remaining contaminants toward the groundwater because the flux will continue under unsaturated conditions. As the perched water zone is desaturated through pumping, removal of the contaminated perched water will become more difficult over time. Currently, a pumping system is used for removal of contaminant mass from the perched water zone to decrease the total contaminant mass transported into the groundwater. The perched water contains elevated concentrations of uranium (U), technetium-99 ( 99Tc), and nitrate (NO 3), and serves as a future flux of contaminated water into the groundwater.

In the 200-DV-1 Operable Unit at Hanford, a perched water zone is located in a fine-grained unit a few meters above the water table within the B, BX, and BY Tank Farms area.

Astm treatment well drawdown