Page 1909 - Week 06 - Thursday, 5 June 2014
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Where fractures and interconnections are ‘tight’, access to this groundwater can be difficult. When hydrocarbons permeate from the surface into these fractures it adsorbs (sticks) onto rock and soil particles making it very difficult to remove. As groundwater levels vary seasonally or, as has been the case recently in the ACT, where periods of drought have been followed by periods of heavy rain, these hydrocarbons “smear” onto the rock and soil surfaces making it even more difficult to completely remove them.
(3) What action has been taken to ensure that the remediation process will be completed as quickly as possible.
Whilst timeframes are determined by the development process, the Environment Protection Authority (EPA) constantly monitors the progress of all sites in the Territory undergoing remediation.
Where phase separated (free) hydrocarbon (PSH) product is identified at a site the EPA requires, consistent with nationally adopted criterion, that it all be removed as a matter of urgency due to the potential explosive nature of vapours associated with this material. Developers and Oil Companies understand the risks associated with this material and undertake the necessary remediation in a timely manner.
As explained earlier, due to the complex nature of our geology PSH can reoccur as hydrocarbons “smear” from the surrounding rock and soils move back into groundwater, with fluctuations in groundwater levels making the task complex and potentially time consuming.
Following the removal of PSH, hydrocarbons dissolved in the groundwater (dissolved phase impacts) must then be removed so as to remove any vapour risk associated with this material. The remediation (removal) of PSH and dissolved phase impacts is typically performed in the ACT by means of multi-phase vapour extraction (MPVE) technologies. This involves the extraction of hydrocarbon (petrol) impacted water and hydrocarbon vapours from the groundwater aquifer beneath a site. This is contemporary practice for this type of contaminant.
(4) When will the remediation process be complete on each site
As I have pointed out, remediation of sites with hydrocarbon impacts to groundwater is complex and will be completed as quickly as possible.
Below are anticipated completion dates provided to the EPA by the Developer/Oil Companies of each site:
Blocks 16 & 17 Section 29 Braddon – Late 2014 to early 2015
Blocks 1 & 2 Section 25 Griffith – 2015
Block 10 Section 12 Higgins – Late 2014
Block 3 Section 41 Lyneham – 2015
Block 13 Section 28 Narrabundah – 2015
Block 1 Section 17 Watson – Late 2014
Block 1405 Tuggeranong – 2015
These are subject to change depending upon the complexities encountered as outlined above.
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