Despite resupply, the remediation team has been hard at work managing groundwater as it flows through our contaminated sites here at Casey.
Our water treatment container (WTC) underwent a retrofit in November (with the help of many Casey tradies). We celebrated the grand opening and promptly began treating surface water, groundwater and bio pile leachate.
The redesign includes larger columns packed with granulated activated carbon, better flocculation, warmer temperatures for the natural hydrocarbon degrading bacteria and a heated hose that reduced daily manual labour in this freeze/thaw environment, thank you Canada for your northern hemisphere tricks! The WTC can treat just over 11,000 litres of water a day when we run it for 12 hours, which we have been able to do now that everything is melting!
In addition to water management, our team completed the build of a brand new bio pile barrier system (named bio pile 8) and we are slowly filling it with soil. Luckily it is warm out and the soil has exposure to heat and oxygen, increasing the microbial degradation of the fuel in the soil.
After designing, constructing and spending significant effort investigating the performance of the barrier system, our team has pretty much got the build phase down pat. This time, we went for the largest bio pile we have ever built, while just almost working within the capacity of our five ton excavator to reach and aerate the soil a few times each season.
The barrier system requires the best sub-grade that Antarctica can offer, and for Casey the gap graded (fines and larger cobbles) and low moisture content soil is always a challenge. To assist the barrier system, we placed a sacrificial retention layer of fine soil that will hopefully be held within the bio pile foundation and not mobilised with the annual pulse of the summer melt.
The next layers included four panels of geosynthetic clay liners and two panels of high density polyethylene plastic welded together by our tradie Colin Ford. Then the protection layers for the main liners were placed and this included screened soil and textiles.
A bio pile barrier system is designed just like a landfill barrier system to hold in leachate (contaminated water) and soil. The challenges of designing in Antarctica come from cold temperatures, freeze/thaw cycles, the arid climate and exposure to high winds and solar radiation. However, despite the challenges the bio piles have been working and last year, after five years of treatment, soil in some of the bio piles was returned to the station as a building foundation material.
It was the first time Australia re-mediated contaminated soil and reused it on site. It was worthy of a celebration after years of working towards proving bio-remediation is possible in Antarctica.