Poor environmetal monitoring at Westconnex St Peters Interchange

Westconnex St Peters Interchange is a massive site bounded by Campbell Road, Princes Highway, Canal Road and Burrows Road in St Peters approximately 6 kilometres from Sydney’s CBD. It links the M8 tollway with the M5. It was built on a recently closed landfill and for this reason requires careful environmental monitoring. This post reports on that monitoring.

Historical Errors

Transport for NSW holds the Protection of the Environment Operations (POEO)Licence Number 4627 for the St Peters Interchange for Road Construction. This licence was previously held for the Alexandria Landfill in St Peters which was compulsorily acquired by the NSW government for the Westconnex St Peters Interchange in 2014.

Most of the conditions in the current licence remains focussed on managing adverse environmental outcomes associated with a putrescible waste landfill.

Community Environmental Monitoring Pty Ltd (CEM) have been evaluating data reported for this landfill since the Westconnex tollway project took over the site. Transport for NSW and their contractors CPB Contractors have been responsible for a large number of both reporting errors and adverse environmental consequences. Previous problems were associated with uncontrolled release of ammonia and sulphide odours and mistakes in gas monitoring.

During construction the contractors were not able to control water infiltration into the waste which caused uncontrolled release of both ammonia and sulphide gas, ruining local amenity for 6 months in 2018. The NSW Environment Protection Authority (EPA) ultimately gave CPB contractors a penalty notice (No: 3173526144) for these failures. In 2019, the company pleaded guilty in the NSW Land and Environment Court and was fined $500,000.

CEM finds high levels of methane and measurement errors

In 2022, CEM reviewed the methane monitoring and found that there were both extremely high levels of methane and errors in methane measurements. The high levels included 68 % methane at 1 Canal Road, nearly 7 times the warning level.  

The gas analysis in gas monitoring wells reported high methane concentrations; some higher than physically possible. During the height of the Methane Fermentation stage of landfill stabilisation, it is common to have high methane levels up to 60 %. Environment contractors hired by Transport for NSW reported methane at 99 % with carbon dioxide at 11 % in gas monitoring well LDS-GM-028 May 2022 monitoring. It is neither possible for methane to be above 70 % in a landfill or for any gas mixtures to be over 100 %. These errors were not identified by either Transport of NSW nor the NSW Environmental Protection Authority who are responsible for monitoring the accuracy of POEO licence monitoring.

The EPA added Condition U2 Hazardous Ground Gases Risk Assessment (HGGRA) Implementation Program to Transport NSW’s the POEO licence. In September 2023, the EPA extended the deadlines associated with the implementation of HGGRA program.

Current Mistakes

The groundwater/leachate monitoring in POEO licences has two separate frequencies – quarterly and annual monitoring.

Quarterly monitoring is for indicator analytes (chemical substances). These are low-cost analytical testing requirements to provide evidence that there have not been significant changes in the quality of the groundwater.

Annual Monitoring requires the testing for the presence of toxic compounds such as heavy metals (arsenic, cadmium, lead, mercury, nickel and zinc), Polynuclear Aromatic Hydrocarbons, Organochlorine and Organophosphate Pesticides, and the Volatile Aromatic Hydrocarbons (benzene, ethyl benzene, toluene and xylene associated with petroleum contamination).

Transport NSW is required to publicly report all monitoring results. CEM reviewed the results back to March 2021 and found that they had not been published. In accordance with section 66(6) of the POEO Act and written requirements issued by the EPA, licensees are required to publish pollution monitoring data that has been collected as a result of a licence condition. This represents an omission reporting violation. There is no evidence that Transport NSW has ever publicly reported the annual groundwater and leachate monitoring parameters. There is also no indication that the EPA has recognised or taken action on this reporting violation.

CEM has identified errors whenever CEM has assessed the data in monitoring reports on the Transport for NSW Alexandria Landfill reporting web page and these have been reported to NSW EPA’s Pollution line via emails.

There are a couple of analytical checks that the environmental testing industry uses to assess whether there were errors made in the in situ or in the laboratory analysis of groundwater. These checks are found in analytical reference Standard Methods for the Examination of Water and Wastewater (APHA 24th ed. Washington DC) which all accredited laboratories use when testing water. The data quality checks include ionic balance (the negative ions and positive ions being equal in solution), calculated total dissolved solids (TDS) being similar to measured TDS, and agreement between the conductivity measured in the field and TDS measured in the laboratory. The reported water quality results sampled in December 2022 (the most recent available) for the following monitoring wells failed at least one of these simple quality assurance checks: LDS-BH-3089A, LDS-BH-3090, LDS-GW-MW3, and WCX-BH157A. This level of incompetence is particularly disturbing because there are only monitor 7 groundwater wells in total.

Future Concerns

Landfills go through well identified stages and looking at leachate is a good way to assess the current landfill stage. The neutral pH, high ammonia concentration and high alkalinity observed in the Alexandria landfill’s leachate indicates that it is still in the Methane Fermentation Stage and will remain so for the next 10-20 years. The presence of methane is also an indicator, of course. This means the putrescible waste is still decomposing with ongoing potential human health and environmental degradation concerns. As the waste decomposes there will be further settling of the existing ground surface. The NSW Landfill Guidelines (NSW EPA, 2016) stipulate that steep gradients greater than 20 % (roughly 10 degrees) should be avoided to reduce the risk of erosion. The settling coupled with the steep slopes found at the Alexandria Landfill poses a continued serious risk for erosion.

There continues to be visible erosion continuing on the surface of the waste pile by Canal Road (see photos). This erosion could affect the protection structures such as final cover allowing water infiltration exacerbating contamination and greater uncontrolled gas movement.

Since there is no oversight on the reporting or quality of the data by either Transport for NSW or the EPA, the Alexandria Landfill remains a serious environmental risk. It is recommended that the site monitoring data be constantly reviewed by a professional environmental chemist with a focus on complying with the POEO licence.

In 2022, Transport for NSW attempted to give the Inner West Council over six hectares of this site as “parkland” as compensation for the impact on residents and the environment of the Westconnex interchange which carved 19,294 square meters from the adjacent Sydney Park. The green space was due to be completed in 2019 but most of the site remains closed to the public today. CEM believes that the Inner West Council would be unwise to take any ownership of this site until the final decomposition of waste has finished.

Charlie Pierce
Research Co-ordinator for Community Environmental Monitoring