Summerhill Environmental Monitoring Results
A range of environmental monitoring is conducted at the Summerhill Waste Management Centre in an effort to measure any impacts that the operations at the Centre may have on the environment. The type and frequency of monitoring conducted is specified by the Centre’s Environment Protection Licence, which is administered by the NSW Environment Protection Authority (EPA). A copy of this licence (No. 5897) can be viewed on the EPA’s website.
A summary of the monitoring program specified by the Environment Protection Licence is detailed below. Results of recent monitoring are available by accessing the attached links.
A figure detailing the locations of various monitoring points is available below. That document labels sites using labels developed prior to implementation of the current Environment Protection Licence nomenclature. A table cross-referencing labels in the diagram and the Environment Protection Licence is also available below.
Groundwater Monitoring Program
The City of Newcastle established a groundwater monitoring program at Summerhill Waste Management Centre (SWMC) in 1993 to characterise background water quality prior to landfilling and to allow identification of potential impacts on groundwater quality and groundwater levels once landfilling commenced. Groundwater impacts from landfilling would most likely arise from the migration of leachate from within the landfill.
A system of groundwater monitoring bores has been installed in stages as the site has developed. The monitoring program involves collecting groundwater samples from these groundwater wells (when the water is present) four times per annum. Samples are tested for a restricted list of analytes on three occasions and for a more comprehensive list of analytes annually, in accordance with Environment Protection Licence requirements.
The groundwater bore network comprises:
- ten monitoring wells around the General Solid Waste (Putrescible) (GSWP) landfill (identified as GW27 to GW36);
- six wells installed around the General Solid Waste (Non-Putrescible) (GSWNP) landfill (identified as GW46 to GW51), and
- two wells installed at the Former Building and Demolition Waste (FBDW) site (GW42 and GW43).
A number of geotechnical and hydro-geological studies were conducted prior to the Centre being approved. These studies identified the previously mined coal measures underlying the site as the most hydraulically permeable strata in the formations present – although un-fractured coal’s hydraulic conductivity is relatively low. Coal seams beneath the site dip generally to the southeast or southwest.
Thus, in locations downgradient from the landfill, it was attempted to install the groundwater monitoring bore screens in coal seams. Upgradient bores (north of the landfill) are located in areas where the coal outcrop has been mined by open cut methods, so seams are not present. Those bores are screened at depths between 5 and 35 mAHD.
Those initial hydro-geological studies and early groundwater sampling also suggested that groundwater levels beneath the site had been artificially lowered by past mining and mine de-watering activities at the adjacent Gretley Colliery. This meant many potentially downgradient bores were dry.
Those same reports anticipated that groundwater levels may rise when de-watering activities stopped at Gretley, although it was noted that groundwater levels could only rise to the elevation of any discharge points from old workings. Since de-watering ceased at Gretley in 2008, groundwater levels beneath Summerhill have not trended upwards, supporting the previous assertion.
A schematic cross-section detailing the geology beneath Summerhill and what was considered as the potential rise in groundwater levels - see below. That cross-section was extracted from one of the abovementioned independent reports (CMPS&F, 1997).
Since commencing groundwater sampling, Council has engaged independent consultants to review the monitoring data and monitoring program on a number of occasions, and has provided those reviews to the NSW EPA. Those reviews have supported the hydro-geological model described above, and have suggested that in many cases, water extracted from bores during sampling represents surface water or condensation pooled within the bores. This is supported by records of static water levels and the variable chemistry of water between bores.
The results of the data reviews are not surprising in view of the previous underground bord and pillar coal mining that took place beneath the site. In bord and pillar mining a regular grid of intersecting tunnels are driven into the coal seams. These tunnels are the bords, and the remnant blocks of coal left between the bords are the pillars. These pillars support the overlying strata during the extraction of the bords, a process known as the first workings. The pillars may be subsequently partially extracted during the second workings, depending on the site. By the end of mining, at least some of the pillars will remain between the voids left from the extraction process. (An idealised schematic diagram of bord and pillar extraction from the Encyclopaedia of New Zealand is shown below)
Source: Encyclopaedia of New Zealand
Because of these previous coal extraction techniques, when groundwater monitoring bores are installed at the Summerhill site, it is a matter of chance whether the bores intersect remnant pillars of coal or voids left after mining. Bores intersecting pillars are unlikely to encounter groundwater, as that groundwater would follow preferential flow paths in the voids between pillars (intact coal is relatively impermeable). As mine discharge points exist at lower (down-dip) elevations than that of the coal seams beneath the Summerhill site, the voids cannot become flooded, and so monitoring bores which intersect voids are also unlikely to encounter groundwater.
Despite the low probability of obtaining meaningful data, Summerhill’s Environment Protection Licence still requires groundwater monitoring. Recent results of that monitoring are available on this web site. An analysis of data trends etc is provided in Summerhill’s Annual Environmental Report.
A section of the Young Wallsend seam exposed during landfill cell excavations at Summerhill. The old workings exposed would have been excavated in the 1880’s.
Surface Water Management
The Summerhill Waste Management Centre (SWMC) occupies two adjacent creek valleys comprising the Wentworth Creek and Flaggy Creek catchments. Both creeks flow northwards from the site and discharge into Hexham Swamp. A number of stormwater quality ponds have been established on the natural site drainage lines and all surface water from disturbed areas passes through at least one pond prior to leaving the site.
Factors that have the potential to influence the quality of surface water discharged from the site include rainfall, the amount of disturbed vegetation or ground cover, discharge of groundwater and the escape of leachate from the landfill or leachate management system. Measures employed to prevent impacts on surface water quality due to the operations of the landfill include:
- screening the types of waste entering the landfill
- installation of a leachate collection and disposal system
- diversion of uncontaminated stormwater runoff around the landfill areas to sedimentation ponds
- daily covering of deposited waste to prevent contact with storm water and minimise leachate generation
- maintenance of erosion and sedimentation control measures.
Surface Water Monitoring Program
A surface water monitoring program for the SWMC was established on-site in 1991 (prior to the SWMC opening) to characterise background water quality prior to landfilling and to assess the potential impacts once landfilling commenced.
The current monitoring program as per condition M2 of the licence includes four sampling locations. Three of these locations are located on the SWMC site and one location is located offsite. These sites are listed below and are presented in the Plan of environmental monitoring locations (340 kb).
- SW55 – Onsite water quality pond downstream of the Former Building and Demolition Waste (FBDW) site;
- SW56 – Onsite water quality pond downstream of the General Solid Waste (Putrescible) (GSWP) landfill cells;
- SW57 – Onsite water quality pond downstream of the General Solid Waste (Non-Putrescible) (GSWNP) landfill; and
- SW58 – Offsite point located in Wentworth Creek, upstream of Minmi Road but downstream of SW56.
Surface water flows from the site at SW56 (GSWP landfill catchment), SW55 (FBDW landfill catchment) and SW57 (GSWNP) landfill catchment).
Due to WHS issues associated with access to the off-site sampling location, and residential development between the SWMC and the sampling location, it was determined in consultation with the EPA to defer off-site sampling pending identification of a suitable replacement location.
The current monitoring program involves collecting a sample from each location four times per year when the surface water ponds are discharging water from site. Historically, surface water samples were collected every four months, regardless of whether the ponds were discharging. In June 2009, the decision was made (in consultation with the EPA) to only sample when the ponds were discharging, so that the samples were representative of the water leaving site.
Field observations and field parameters are taken at the time of sample collection. Samples are collected used decontaminated containers and transferred into laboratory supplied sterile bottles. The samples are submitted to a NATA accredited laboratory and tested for the list of analytes required by the site Environment Protection Licence (EPL).
Analysis of sampling data is conducted by independent environmental consultants. Due to a lack of relevant thresholds to compare results against, sampling data is compared against pre-landfilling data where relevant. Known leachate indicating parameters are also compared against levels contained in site leachate to allow identification of any potential leachate impacts. A full discussion of those results is contained in the Annual Environmental Report also prepared by those consultants.
Dust Deposition Monitoring
Dust deposition monitoring is conducted at the SWMC in an effort to assess the contribution of site operations to dust fallout in the surrounding area. Dust fallout is measured using dust deposition gauges in accordance with the requirements of the Australian Standard 3580.10.1 – 1991. The dust deposition rate is measured as the amount of dust deposited on a horizontal surface and the units for this parameter are grams per square metre per month (g/m2/month).
Three dust deposition gauges were installed off-site in 1991, identified as DM9, DM8 and DM7. Two additional gauges were installed on-site in December 1997 and a third on-site gauge was installed at the GSWNP site in September 1999. The on-site gauges are identified as DM2, DM3 and DM4. View Plan of environmental monitoring locations (340 kb).
DM2 was removed during the construction of an Ausgrid electricity substation adjacent to Summerhill’s access road. Due to the consistent vandalism of the gauge, that gauge has not been successfully reinstalled. Off-site dust gauge DM9 was also decommissioned in August 2010 as the trees surrounding the subject resident’s yard had grown too high and it was no longer providing a location which met the requirements of the Australian Standard. A suitable replacement residential location has not yet been found.
Clean bottles were placed in the dust gauges at the beginning of each month and retrieved within 30 days ± 2 days in accordance with AS3580.10.1 – 1991. The samples were analysed by Council’s Laboratory for total insoluble solids. View results of monitoring in tabular and graphical form (61.38 kb).
The Environment Protection Licence for Summerhill does not specify a dust deposition threshold or limit. However, Council has adopted a target of not exceeding an annual average result of 3.9 g/m2/month at each individual location.
This target is based on the NSW EPA annual average target of 4 g/m2/month (Approved Methods for the Modelling and Assessment of Air Pollutants in New South Wales, NSW EPA, 2005).
View monthly dust deposition results at each location for 2012 (61.4 kb) - shown in tabular and graphical form.