252
Permeable Reactive Barrier
FIGURE 12.1
Botany groundwater location plan. (From Orica Ltd.)
All plumes originate from multicomponent source areas denoted with the
letters S, C, and N (standing for Southern, Central, and Northern, respectively), corresponding with the grouping as follows:
• Southern Plumes—Comprising primarily CTC, PCE, TCE, and EDC
(and their daughter products including VCM and chloroform) from
former CTC, PCE, and TCE production.
• Central Plume—Comprising primarily EDC with lower concentrations of TCE, VCM, and other daughter products from the former
EDC to PVC manufacturing processes.
• Northern Plumes—Comprising mainly EDC. It is believed that
these plumes were mainly formed from the historical movement of
the Central Plume toward the former large-scale industrial groundwater abstraction well fields north/northwest of the site in the 1960s
to the 1980s. It is also likely that other CHCs were derived from corroding drums of CHC waste in the former open-air waste-storage
areas. There is also a CTC plume associated with a former tank farm
and loading bay (N4).