Council has carried out extensive rehabilitation works at the Barretta Waste Management Facility under an agreed closure plan with the Environmental Protection Authority (EPA). Since the landfill cap was completed in 2015, Council has continued to improve the site, including new fencing, roofing, landscaping/rehabilitation, solar generation and environmental monitoring at the site. We are working closely with the EPA to improve environmental conditions both on and offsite, and ensure that visitors to the site and nearby residents are not impacted by on-going operational or historic contamination from the site.
Current Environmental Conditions
Based on the results of the monitoring program, the following conclusions have been made.
- Per-& Poly- Fluoro Alkylated Substances (PFAS) were detected in leachate at the site, including in leachate dams and in landfill gas extraction bores installed in the waste mass. Compared to data in the literature, PFAS concentrations in the leachate were less than the mean reported for other Australian closed landfills. PFAS concentrations in leachate were also less than the primary contact recreation guideline indicating that the risk from incidental contact by workers at the site is very low.
- Leachate should be retained onsite wherever possible and managed to avoid high water levels in the leachate dams to minimise risk of spill over to the stormwater perimeter drain. Ongoing irrigation of the cap to manage leachate onsite is currently preferable to a higher risk of dam overflow during heavy rain events. Irrigation practices should avoid over-irrigation or excess runoff. An option for excess leachate is being progressed with TasWater for offsite disposal via trade waste, although the rising main is not operational and discharge limits for PFAS have not been established. Council will continue to pursue this option as the preferred method for removing PFAS contaminated leachate from the site.
- PFAS was detected in groundwater in two areas with concentrations that exceeded ecological, drinking water and primary contact recreation guidelines. This included the southeast corner of the site and adjacent offsite area; and in the eastern part of the site and adjacent offsite area along the alignment of the creek line. Domestic groundwater bores have not been identified in the residential area east of the site, a registered groundwater bore was identified on the Tassal site and downgradient of inferred groundwater flow. Tassal has advised Council that this bore is not in use. Groundwater discharge is also anticipated to occur along the shoreline of North West Bay, east and southeast of the site. These results trigger the need for further investigation of the risk of potential PFAS exposure to these receptors. Groundwater modelling of contaminants is currently being investigated and will be reported once completed.
Surface Water and Sediments
- PFAS was detected in stormwater at the site and offsite at the creek discharge point, at concentrations that exceeded the ecological guideline. PFAS was not detected in marine waters or sediments adjacent to the shoreline and creek discharge point, and not detected in the broader areas of the Bay north, east and south of the site.
- PFAS concentrations were below the primary contact recreation guideline indicating that the risk from incidental contact by public visitors to the creek and shoreline is low. The results indicate a risk to aquatic biota in the creek and shoreline discharge area, including the potential for bioaccumulation. Council recently sampled biota (flathead and oysters) from the Barretta bay / shoreline and the results will be provided once complete.
- PFAS levels detected in surface water leaving the site improved during the three sampling rounds, likely reflecting improved management and containment of leachate over this period. PFAS has been identified as a contaminant of concern in surface water at the site and will be included in future monitoring of surface water both on- and offsite.
Council are acting on the following recommendations.
- Discussions have commenced with TasWater on trade waste limits for PFAS and have submitted a request for disposal of PFAS impacted leachate to sewer.
- The extent of PFAS impacts in offsite groundwater are currently being investigated, with installation and sampling of additional groundwater monitoring wells to attempt to delineate PFAS in groundwater to the east and southeast of the site. Five bores have been approved for this purpose.
- The groundwater modelling conducted in 2015 will be updated to include PFAS as a contaminant of concern. Updated modelling will account for results of the additional monitoring bores, and include modelling the migration of PFAS to the east and southeast of the site. This work is currently underway.
- The risk assessment conducted in 2016 will be updated to include PFAS as a contaminant of concern. It is anticipated the updated risk assessment would assess risks from PFAS in surface water and groundwater, and incorporate sampling of aquatic biota in and around the shoreline discharge area. This work is approved for the 2018/19 fiscal year.
- Public signage has been installed at the creek shoreline area with advice to avoid contact with stormwater, similar to existing signage elsewhere in the municipality such as at stormwater drain discharge points at Blackmans Bay beach. More broadly, this would also take into account other contaminants that have been previously detected in stormwater discharging from the site, including Coli, metals and hydrocarbons. These signs have been installed.