The WGM Rising Main:
19. The Council's "sewage reticulation system" as regulated by the Licence includes the WGMJ Rising Main.
20. The WGMJ Rising Main is approximately 3,232m in length, beginning at the WGMJ Pump Station at 224 Manns Road, West Gosford NSW 2250. It then crosses Narara Creek via an aqueduct, runs parallel to Narara Creek, through a golf course and terminates at the Springfield Sewer Tunnel. The total elevation of the pipeline from the lowest point to the highest point is 11.4m.
21. The WGMJ Rising main is a 750mm (nominal internal diameter) mild steel cement lined pipe from chainage 0m to 116.9m.
22. The WGMJ Rising Main then transitions to a 600mm (nominal internal diameter) ductile iron cement lined pipe from the buried section east of the aqueduct crossing over Narara Creek, and for the remainder of the pipeline from chainage 116.9m up to its termination at the Springfield Sewer Tunnel. This section of pipeline comprises of a cement internal lining, ductile iron primary pipework material, and a plastic external lining.
23. At all relevant times, the Council was responsible for the management, operation, inspection, maintenance and repairs of the WGMJ Rising Main.
24. The WGMJ Rising Main was constructed in approximately 1985-1986 by NSW Public Works Department. There have been no upgrades or modifications made to the WGMJ Rising Main since its construction.
25. The Council was not responsible for the location, route, design or construction of the WGMJ Rising Main.
26. The purpose of the WGMJ Rising Main is to transfer sewage from the WGMJ Pump Station and the Kariong Carrier Main (and including the upstream sewage pumping stations as listed in [18] above contributing to these sources) to the Springfield Sewer Tunnel.
27. The WGMJ Rising Main is considered a critical asset within the Council's sewage system.
28. A significant part of the WGMJ Rising Main is located within 100m of Narara Creek. NSW soil mapping data shows that acid sulphate soils are present in the vicinity of Narara Creek. Acid sulphate soils increase the risk of external corrosion of metal pipes by increasing the solubility of metals in soil.
29. The WGMJ Rising Main is likely subject to high external corrosion rates due to the flow of groundwater in combination with the occurrence of acid sulphate soils in these areas.
Key Components of the Council's Sewage Treatment System
30. The key components of the Council's sewage treatment system of relevance to these proceedings are summarised below:
a). WGMJ Pump Station: The WGMJ Sewer Pump Station pumps sewage under pressure into the WGMJ Rising Main. Sewage flows into the WGMJ Rising Main are also received from the Kariong Carrier bypass of the WGMJ Pump Station.
b). WGMJ Rising Main: The WGMJ Rising Main transfers sewage under pressure from the WGMJ Pump Station and sewage under gravity drainage from the Kariong Carrier Main to the Springfield Sewer Tunnel, and eventually to the Kincumber STP.
c). Kariong Carrier Main: The Kariong Carrier Main flows from the Kariong Plateau down towards the WGMJ Rising Main. During normal operation, the Kariong Carrier Main flows around the WGMJ Pump Station and connects directly into the WGMJ Rising Main. Flows in the WGMJ Rising Main from both the WGMJ Pump Station (pumped) and the Kariong Carrier Main (gravity) flow into the Springfield Sewer Tunnel and into Kincumber STP.
d). Kariong Carrier Main Bypass: The Kariong Carrier Main Bypass allows for sewage flows to discharge into the WGMJ Pump Station, rather than directly into the WGMJ Rising Main.
e). West Gosford Catchment: Sewage catchment area for the WGMJ Pump Station.
f). Springfield Sewer Tunnel: The Springfield Sewer Tunnel transfers sewage to the Kincumber STP.
g). Kincumber STP: Flows in the WGMJ Rising Main from both the WGMJ Pump Station (pumped) and the Kariong Carrier Main (gravity) flow into the head of the Springfield Sewer Tunnel and into Kincumber STP.
h). Discharge Point 1: The only permitted Discharge Point for Discharge to Waters pursuant to the Licence is "Discharge Point 1" located north of Winney Bay NSW.
Figure 1: WGMJ Rising Main and adjacent systems
The Enforceable Undertaking following a rising main failure in Wamberal in January 2019
31. Between 24 January 2019 and 29 January 2019, a hole in a sewer rising main at or near 893 The Entrance Road, Wamberal NSW 2260 caused approximately 2,200,000 litres of raw sewage to discharge into Forresters Creek and Wamberal Lagoon.
32. The EPA entered into an enforceable undertaking with the Council pursuant to s 253A of the POEO Act on 15 January 2020 in relation to the abovementioned incident (the 2019 EU).
33. The Council made a commitment in the 2019 EU to complete a Pressure Mains Criticality Analysis project (PMCA) by 31 December 2020. The Council committed to the following actions as part of the PMCA project:
a) to assess and assign a risk criticality score to each water and sewer main section in the Council's sewer network;
b) to use the risk criticality scores to prioritise proactive sewer main inspections to assess the condition of the sewer mains; and
c) to use the results of the inspection program to identify isolated sewer mains that require regular inspection regimes and additional monitoring via the Council's Supervisory and Data Acquisition (SCADA) system to reduce the likelihood of failures.
The failure of the WGMJ Rising Main in 2020
34. Between approximately 11:15pm on 26 February 2020 and 12:20pm on 25 March 2020, being a period of approximately 31 days and 1 hour, an estimated volume of 8,000,000 litres of untreated sewage discharged from a hole in the WGMJ Rising Main and into the environment, including Narara Creek (the 2020 Incident).
35. Council became aware of the 2020 Incident when a member of the public reported sewage flowing into Narara Creek behind 10 Racecourse Road, West Gosford on 23 March 2020 at 10:45am. Council subsequently identified the start date of the incident by observing a retrospective drop in pressure on 26 February 2020 on its SCADA system.
36. A photograph of the hole the subject of the 2020 Incident showed the polyethylene sleeve wrapped around that section of the pipeline to be in poor condition.
37. On or about 30 March 2020, in accordance with s 148 of the Protection of the Environment Operations Act 1997 (POEO Act), the Council notified the EPA and relevant authorities of the 2020 incident as potentially having caused or threatened material harm to the environment.
38. The cause of the 2020 Incident was identified as being corrosion of the 600mm plastic lined section of the WGMJ Rising Main.
39. WSP is an independent multi-disciplinary wastewater engineering consultancy with expertise in sewerage management infrastructure. They provide advisory services and engineering solutions for regulatory standards compliance, the protection and enhancement of the environments and the promotion of sustainable development.
40. Mr Jamie Loader, the Council's Director of Water and Sewer, agreed that WSP had been requested by Council to prepare a condition assessment of the West Gosford Major Sewer Rising Main and he accepted that WSP had come to the conclusion that the sleeve around the 'West Gosford Major' was in poor condition in March 2020. In his record of interview, Mr Loader stated the following:
Q 175 Okay. So based on the photos, WSP have come to the conclusion that the sleeve around the West Gosford Major was in a poor condition.
A Yes that's what it says, yes.
Q 176. That's right. So my understanding is council were repairing that particular break?
A Yes.
Q 177. So council staff would have been there at the time of the break?
A Yes.
Q 178. Council would have been in a proximity to view the break?
A Yes.
Q 179. So I guess I'll just again, does council consider they were aware of the condition of that sleeve at the time of the 2020 break?
A Yes.
Q 180. Okay. Does council consider that they would have been aware of the poor condition of the sleeve at the 2020 break?
A Yes.
41. In response to a request for information about the 2020 Incident, including any actions that Council had since taken to prevent or mitigate against a recurrence, the Council advised the EPA as follows:
"High level alarm added into SCADA for WGMJ. The alarm will be triggered for a drop in pressure equivalent to that indicative of a potential break.
CCC are currently undertaking a Pressure Main Criticality Analysis of sewer rising mains that assigns risk to all rising main segments. This will assist in determining which sections of pipe should be included in our proactive condition assessment program. It is envisaged that this program will significantly improve Council's ability to detect breaks in isolated main".
42. The Council did not conduct any physical preventative maintenance work on the WGMJ Rising Main following the 2020 Incident.
The Council's Pressure Main Criticality Analysis project
43. Following the 2020 Incident, WSP, an independent contractor engaged by the Council, prepared the following documents supporting the Council's PMCA project contemplated by the 2019 EU:
a) Intervention Plan - Basic Intervention Framework, dated 26 June 2020 (the WSP Intervention Plan). The purposes of the WSP Intervention Plan were to recommend a basic framework to assist with decisions regarding when and how to intervene during the asset life of sewer pressure pipelines, and to categorise different types of interventions that are used to manage the risk profile of the pressure pipeline portfolios;
b) Pipe Performance Report - Likelihood of Failure - Sewer, dated 22 July 2020 (the WSP Pipe Performance Report). The purposes of the report were to identify the likely factors that correlate to actual sewer pressure pipe failures. WSP concluded in the report that acid sulphate soil does not indicate any increase in failure rate, on the basis that the highest failure rates were observed in pipes located outside of acid sulphate soil areas. WSP's recommendation was that acid sulphate soil is not used as a cohort for assigning expected remaining life in the next project stage.
Included with the WSP Pipe Performance Report were three additional documents each dated 10 July 2020 and respectively titled Sewer Mains Pressure CoF Final, Sewer Pressure Mains LoF Final and Sewer Pressure Mains RoF Final;
c) Pressure Main Criticality Analysis - Final Report, dated 1 September 2020 (the WSP PMCA Final Report). This report set out the project methodology to assign scores for likelihood of pipe failure (LoF), consequence of pipe failure (CoF) and the resulting risk of failure (RoF), with the scores to then be assigned to each pressure main in the Council's water supply and sewer network.
Included with the WSP PMCA Final Report were three Microsoft Excel spreadsheets respectively titled sPressureSewerMain_CoF_V1.2, sPressureSewerMain_LoF_V1.2 and sPressureSewerMain_Risk_v1.2.
44. The purpose of engaging WSP to carry out the Pressure Main Criticality Analysis was to bring expertise to bear on the task which the Council did not possess.
The Initial Risk Rating for the WGMJ Rising Main under the PMCA
45. As part of the PMCA, each pipeline the subject of the analysis was assigned a LoF score and a CoF score. These scores were then multiplied to calculate an "overall failure risk" (RoF) score.
46. The initial LoF score for the WGMJ Rising Main was 1, and was calculated based on the following criteria:
1. Field condition assessment - This criterion is based on the actual condition of an asset, as verified by testing and/or inspection. Information regarding the field condition of the WGMJ Rising Main was not input into the LoF calculation for the initial risk score because no condition assessment had been undertaken as at that time;
2. Failure history - This criterion is based on previous recorded failures of the asset. The LoF score for the WGMJ Rising Main did not take into account any recorded failures despite the fact that 2020 Incident occurred prior to the PMCA being finalised;
3. Derived Condition - This criterion is based on age of the asset, pipe material, pipe diameter and maximum operating pressure.
47. The LoF spreadsheet for each sewer pipe asset the subject of the PMCA incorporated an acid sulphate soil risk. The WGMJ Rising Main was assessed as subject to a high acid sulphate soil risk for the sections of the pipeline laid in proximity to Narara Creek. However, WSP did not include acid sulphate soil risk as an input to the LoF calculation, despite the fact that acid sulphate soil significantly increases the risk of external corrosion of metal pipes.
48. The Council's experts preparing the PMCA:
a) did not consider acid sulphate soils a high risk factor and in the absence of any greater expertise within the Council the assessment was not questioned by Council's officers at the time; and
b) did not include the 2020 incident in the PMCA as it had not yet occurred at the time the PMCA supporting data for inclusion in the report was generated.
49. The initial CoF score for the WGMJ Rising Main was 5, and was calculated based on consideration of the following criteria:
1. Financial - repair cost and damage to property;
2. Social - including consideration of loss of service, public health and safety, and reputational damage;
3. Environment - based on assessment of pollution damage.
50. The outcome of the PMCA resulted in the WGMJ Rising Main being assigned an overall risk score of 5 and being placed into the "low risk" category as at 1 September 2020 based on the following scores:
a) LoF: 1
b) CoF: 5
c) Overall risk score [RoF score]: 5
51. The low risk category specified that validation of pipe specific input data within the framework should occur before the pipe is promoted for condition assessment or renewal. This category is described relevantly in the WSP Intervention Plan as follows:
"3.7 Do Nothing
Where the pipe failure risk is low there is little financial justification to pursue interventions such as condition assessment or renewal. In this case the recommendation is to do nothing…
For pipes with a medium or high consequence of failure, little intervention is expected during the first portion of their asset lives. The point of first intervention is a function of failure risk and will generally occur earlier for pipes that have a very high consequence of failure".
The Council's Updated Risk Rating for the WGMJ Rising Main in 2021
52. On 19 May 2021 the EPA wrote to the Council to request it confirm the WGMJ Rising Main's score in the PMCA.
53. The Council advised the EPA on 10 June 2021 that the WGMJ Rising Main had obtained the following scores in the PMCA:
a) CoF score: 5/5
b) LoF score: 1/5
c) Overall risk score [RoF score]: 5/25
54. As at 10 June 2021, the WGMJ Rising Main was still assigned an overall risk score of low, and assigned to the "Do Nothing/Validate Asset Data" asset category.
55. The Council provided the following explanation as to how the risk score for the WGMJ Rising Main had been calculated:
"the risk score was calculated by assessing sewer rising main sections for LoF and CoF, which combined resulted in the overall RoF of each pipe segment… the LoF methodology is derived by an estimation of the pipe remaining useful life considering age, material and acid sulphate soil risk, adjusted where there are recorded failure records. The CoF methodology combines 15 data sources to identify the financial, social and environmental consequences of pipe failure."
56. On 4 August 2021, the EPA wrote to the Council expressing concern at the low risk rating assigned to the WGMJ Rising Main in light of the 2020 Incident, and noting that functionality improvements advised to have been made to the SCADA system are post event notification improvements, not measures to prevent the recurrence of further pipe breakages and significant environmental impacts.
57. On 9 September 2021, the Council wrote to the EPA advising that the WGMJ Rising Main had been re-classified as high risk, with intervention recommendations including an initial condition assessment under its PMCA framework. The Council's response advised of the following updated risk scores for the WGMJ Rising Main:
a) CoF: 5/5
b) LoF: 3/5
c) Overall risk score [RoF score]: 15/25
58. The Council further advised the EPA that it had, as at 9 September 2021, engaged a specialised consultant to carry out a condition assessment of the WGMJ Rising Main and that funding for partial main replacement had been included within the Council's Independent Pricing and Regulatory Tribunal (IPART) submission. As at that date, the Council had not engaged any contractor to carry out a condition assessment in respect of the WGMJ Rising Main.
59. On 11 February 2022, the Council issued a purchase order to engage WSP to undertake a condition assessment of the WGMJ Rising Main.
60. While the purchase order engaging WSP to undertake a condition assessment of the WGMJ Rising Main had a required completion date of 27 October 2022, the assessment was not completed until July 2023.
61. The time taken was adversely affected by staff shortages in Council available to plan and deliver asset management programs. This included a lack of staff to oversee contracts, including the PMCA and condition assessment contracts.
The failure of the WGMJ Rising Main in 2023 the subject of these proceedings
62. On 6 March 2023, the SCADA alarm threshold for the WGMJ Rising Main triggered. By 8 March 2023 the Council's technicians had investigated the alarm but had been unable to identify the cause of the trigger.
63. The SCADA alarm threshold triggered again on 8 March 2023 and the Council arranged for further investigations to be conducted. The Council's civil crew walked the easement of the WGMJ Rising Main on 17 March 2023 but did not identify evidence of leaks, nor detect any odour.
64. At about 12:44pm on 13 April 2023, the Council received a report from a member of the public, Mr Lewis Windle, regarding an overflow of sewage in the vicinity of Narara Creek.
65. At approximately 3:22pm on 13 April 2023, the EPA's Environment Line received a call from Council staff member Ms Joanne Mack self-reporting a sewer main break into Narara Creek from 10 Racecourse Rd, West Gosford NSW, with an unknown volume and considered significant.
66. Between approximately 12:44pm on 13 April 2023 and 2:05pm on 15 April 2023, being a period of approximately 2 days, 3 hours and 20 minutes, an estimated volume of 1,834,000 litres of raw sewage discharged from a 150mm by 50mm sized hole in the WGMJ Rising Main and into the environment (including Narara Creek) (the 2023 Incident).
67. The 2023 Incident occurred in the vicinity of 10 Racecourse Road, West Gosford NSW 2250, in an area adjacent to mangroves. More specifically, the 2023 Incident occurred at about chainage 850m from the WGMJ Pump Station. The depth below ground of the WGMJ Rising Main at the location of the 2023 Incident was approximately 1-2m.
68. The location of the hole in the WGMJ Rising Main subject of the 2023 Incident was approximately 90m in distance downstream from the hole the subject of the 2020 Incident.
69. The diameter of the WGMJ Rising Main at the location of the 2023 Incident was 600mm (nominal internal diameter) and the composition of the pipeline was ductile iron cement lined.
The cause of the 2023 Incident
70. The sewage overflow from the WGMJ Rising Main that occurred in the course of the 2023 Incident was caused by external corrosion of the WGMJ Rising Main pipe wall (as was the case in respect of the 2020 Incident).
71. More specifically, corrosion of the WGMJ Rising Main leading to the 2023 Incident was likely to be a combination of the following factors:
Corrosion Presence at WGMJ Rising Main Explanation
Factor
Chloride High concentrations recorded in close proximity to Narara Creek. Narara Creek is an estuarine waterway. Salinity from the creek may create brackish groundwater which contains chlorides.
Acidity Low pH (4.9) recorded in proximity to the WGMJ Rising Main 2023 Incident location. The WGMJ Rising Main is installed within acid sulphate soils.
Moisture Content Moisture content in excess of 38% recorded at locations along the WGMJ Rising Main. Proximity to Narara Creek leads to increased soil moisture content.
Soil Conductivity Soil conductivity in proximity to Narara Creek is considered to be highly corrosive. The presence of chlorides and high moisture content support high soil conductivity.