Contaminated groundwater
had previously migrated off-site into this area prior to construction
of the boundary containment systems.
The First Creek Pathway System consists of five extraction
wells and six recharge trenches. The extraction wells
are spaced 60–152 m apart and are aligned along the main
axis of the plume. The recharge trenches are located along
the edge of the pathways and downgradient of the extraction
well system (Fig. 3). This configuration is intended to
enhance the flushing of clean water towards the extraction
wells.
The Northern Pathway System consists of 12 extraction
wells and 24 recharge wells. The extraction wells are located
60 m apart and aligned perpendicular to the direction
of groundwater flow. The recharge wells are positioned
30 m apart and located 91 m downgradient of the extraction
well line (Fig. 3).
The Offpost systems are designed with the groundwater
being pumped out of the unconfined aquifer, purified by
removing contaminants, and recharged back into the aquifer
using recharge wells and trenches. These systems are a
complex array of trenches, pumping and injection wells.
Their operation is further complicated by periodic flow in
nearby irrigation canals, pumping in nearby wells for irrigation
and municipal use, and complex local hydrogeology.