CW1050900:RD 2 17 January 2022
K:\Projects\CW1050900_Bunbury-Harvey_Regional_Council_Groundwater_Monitoring_CRWMF\5_Technical\Water and Environment\Reports\Report Annual 2021\CW1050900_Licence_Addendum_Groundwater_Support_Memo_rev3 docx
at GQ1S (bicarbonate) and GQ2S (ammonia and Total Nitrogen). A decreasing trend was observed at GQ11D for TN.
GQ1S and GQ2S are adjacent to the neighbouring (offsite) landfill and are likely to be impacted from leachate generated from the unlined cells present. This is supported by other source bores at the Stanley Road Facility reporting no increasing trends and down-gradient bore GQ11 reporting greater concentrations than onsite boundary bores.
1.2 Plume Stability and Risk Discussion
Consideration has been given to the previous four years of data 2018-2021 for all groundwater analytes and the Mann-Kendall (95%) trend analysis undertaken. Predominantly, groundwater quality has remained stable at the site and at down-gradient bores with further discussion provided in Table 1-2.
There are no clear trends for any major metal impacts with background bores generally reporting the same or higher concentrations than down-gradient bores; suggesting metals are regionally elevated. Due to this, metals are not further discussed in Table 1-2.
Based on the results of the landfill leachate indicator assessment and the plume stability, a risk discussion is also provided in Table 1-2.
CW1050900:RD 4 17 January 2022
1.3 Contaminated Sites and Remediation
As part of on-going contaminated site investigations, Cardno completed the first stage of Detailed Site Investigations (DSI) (Cardno, 2020) which concluded the following:
The CSM for the Site was refined following the investigation with the following potentially complete S-P-R linkages identified:
> Concentrations of nutrients adjacent to the Site boundary and down-gradient of the
Site have been recorded above adopted human health (aesthetic) and ecological assessment criteria;
> Concentrations of metals adjacent to the Site boundary and down-gradient of the
Site have been recorded above adopted human health (aesthetic) and ecological assessment criteria;
> Concentrations of PFOS adjacent to the Site boundary and down-gradient of the
Site have been recorded above adopted ecological assessment criteria; and
> Concentrations for the sum of PFHxS and PFOS adjacent to the Site boundary and
down-gradient of the Site have been recorded above adopted human health (drinking water) assessment criteria.
The pathways for nutrient and metal exposure and risks to human health and
ecological receptors presented in the Preliminary Site Investigation (PSI) in relation to groundwater are considered to be relevant and data presented in this report does not suggest any significant changes to these mechanisms or risks, with the risk posed by these CoPCs considered as low. However, the results of the investigation have identified potentially complete S-P-R linkages, in relation to human health and
ecological receptors located off-site associated with PFAS, with particular reference to the exposure pathway of household/domestic utilisation and garden irrigation. These conclusions were supported by the appointed contaminated sites auditor
Subsequent to this, Cardno has commenced Stage two of the DSI which included an off-site water survey and sampling which indicated a low and acceptable risk for non- potable and potable water use for off-site residential water use. The results of the survey have been reported and supported by DWER Contaminated Sites team. The results will be reported as part of the stage two DSI reporting along with further groundwater bore installation and sampling.
Further, as part of contaminated sites, it will be likely recommended that remediation shall be undertaken which will include, capping of the existing unlined landfill cells and moving to a lined facility to continue operations.
Yours sincerely,
Riccardo Divita
Principal Contaminate Hydrogeologist for Cardno
