3 As at 17 November 2008, the Department of Environment and Climate Change was established pursuant to the Public Sector Employment and Management Act 2002 as a department of the Government of New South Wales. The Department is currently named the Department of Environment, Climate Change and Water (DECCW). As at 17 November 2008 (and continuing today), the Parks and Wildlife Group of the Department (PWG) operated as the National Parks and Wildlife Service of NSW. The Government is part of the Crown in right of the State of New South Wales. The Crown in right of the State of New South Wales is a corporation sole. It is capable of being prosecuted, convicted and sentenced in these proceedings; see WorkCover Authority of NSW (Inspector Keelty) v Crown in the right of the State of NSW (Police Service of NSW) (No 3) (2002) 112 IR 141 at [2], Environment Protection Authority v The Crown in right of New South Wales [2002] NSWLEC 52 at [3]-[4].
4 The Defendant has pleaded guilty and has therefore admitted the essential elements of this offence. The offence is one of strict liability so that mens rea is not an element of the offence.
5 The maximum penalty applicable to offences under s 64(1) of the POEO Act is $1 million for a corporation. The penalty for this offence was increased to $1 million from $250,000 in May 2006.
Agreed Statement of Facts
6 The parties have tendered an Agreed Statement of Facts (ASOF) as follows.
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The Sewage Treatment Plant
3. Since about 1980 a Sewage Treatment Plant has operated in the Perisher Valley. The Plant is located at Perisher Creek Road, Perisher Valley (the "Premises") within Kosciuszko National Park.
4. The Plant services the villages of Perisher Valley, Smiggin Holes, Guthega and Blue Cow, located in the National Park.
5. As at 17 November 2008, the State of New South Wales (Parks and Wildlife Group of the Department of Environment and Climate Change) owned and operated (and continues to own and operate) the Perisher Sewage Treatment Plant.
6. The Plant operated with three operators on a roster. The operators were supervised by the Water and Wastewater Supervisor, Mr Chris Foley, who reported to Senior Engineer, Mr Mark Rigoni. On 17 November 2008, Mr Rigoni and Mr Foley were located off the premises at the Parks and Wildlife Group's Municipal Services Unit in Perisher Valley. The Manager of the Unit was Mr Andrew Logan.
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Operation of the Plant
10. Raw sewage from the resort areas is conveyed to the Plant via a network of pipes and pump stations.
11. When operating normally, high quality treated effluent from the Plant discharges into Perisher Creek.
12. Perisher Creek waters then enter the Perisher Range Aqueduct approximately 2km downstream of the Perisher STP. Water from the aqueduct discharges into Snowy Hydro's Guthega Dam. In the winter months some water is extracted from the aqueduct for snowmaking activities at Mt Blue Cow, after which it also ends up in the Guthega Dam. Water from Perisher Creek would remain in the Dam for some months before discharging. Water from Guthega Dam is then used to generate power at the Guthega Power Station, after which it goes into the Island Bend Dam, via the Snowy River.
13. The Plant is an 8000 Equivalent Persons (EP) treatment plant. After primary treatment (screening), the secondary treatment process utilised by the Plant is an Intermittently Decanted Extended Aeration (IDEA) system (explained below). Secondary treated effluent is then tertiary treated by ultraviolet light disinfection prior to its discharge into Perisher Creek.
14. There are three separate IDEA tanks at the STP. During peak loads in winter, after passing through the inlet works, raw sewage is distributed to between the three IDEA tanks via a flow divider (the "splitter box") - essentially a large gate valve. In summer when loads are small, raw sewage is typically treated in a single IDEA tank. The sludge from this tank is then used to "seed" the other tanks prior to winter loads.
15. The process cycle of the IDEA comprises aeration, settlement and decant. Within a single tank, sewage undergoes clarification, aeration and solid liquid separation. This treatment process relies on the sewage being exposed to a blanket of biologically active sludge (bacteria) in both an aerobic and anoxic state. This treatment (along with the limited chemical dosing of alum) results in a reduction of Biochemical Oxygen Demand, Solids, Nitrogen and Phosphorus in the sewage and an increase in clarity.
16. Secondary treated effluent is decanted from the IDEA tanks into a catch-balance pond prior to its discharge to Perisher Creek through the tertiary treatment process, the ultraviolet light disinfection chamber (UV chamber).
17. The purposes of the catch-balance pond are to catch by settling out any carry over of solids that may have been discharged from the IDEA tanks in the event of a process perturbation or failure and to balance the flow to the UV chamber and the Creek. Effluent and material in the pond can be returned to the plant for treatment.
18. The efficient operation of the IDEA tanks relies on the sludge blanket being maintained below a prescribed depth within the tanks. This ensures that sludge is not carried over into the catch-balance pond and UV system following decanting of secondary treated effluent.
19. In the normal course of the Plant's operation, the volume of the biologically active sludge will increase as the biological population increases and additional organic material is added to the system from the sewage. Accordingly, active sludge is "wasted" or transferred into sludge holding tanks.
20. There were two (waste) sludge storage tanks - one of 600 KL capacity and the other being 1200 KL. The contents of the sludge tanks are aerated to keep the sludge fresh during storage, particularly in the winter months. On a regular manual basis throughout Winter, aeration is turned off, the tanks' contents are allowed to settle and then, to create more space in the tanks, supernatant which accumulates on the top during settling is decanted. The decanting is done by lowering a pump into the supernatant contained in the tank. The cycle of aeration, settling and decanting continues until sludge dewatering operations. As part of the annual sludge dewatering operations, once the supernatant has been decanted, the sludge can be dewatered and then removed and transported to sludge drying beds at a site some distance from Perisher.
21. The pipework at the Plant allowed the decanted supernatant to be pumped either to the decant pit and thence to Perisher Creek via the catch-balance pond and the UV chamber, or to be sent back into the treatment process via the splitter box or the lift pump station in the Plant's inlet works.
22. Since the supernatant might contain elevated levels of nutrients which could adversely affect the Creek, it was both practice and in accordance with written procedure, when supernatant was decanted from the sludge storage tanks to return the supernatant to the beginning of the treatment process, that is the splitter box or the lift pump station. By being returned to the treatment works in the Plant, the decanted supernatant would undergo full biological and chemical treatment prior to being sent to the catch-balance pond, then to the UV disinfection chamber and then discharged to Perisher Creek. If any sludge carry-over occurs under normal treatment protocols, the sludge is typically captured in the catch-balance pond where it can be recovered for treatment within the Plant.
23. The Plant is located in an environmentally sensitive area and operates under a range of challenging constraints such as being snow-bound during winter and subjected to shock loads during peak holiday periods.
24. A consequence of the plant being snowbound during winter is that waste sewage sludge generated during the winter months must be stored at the premises until it can be removed in spring/summer (the period when this incident occurred).
25. With the onset of the warmer months and reduction in load at the plant, the sludge is pumped from the tanks, dewatered and transported from the site. It is as part of this process that the supernatant is removed and returned to the secondary treatment cycle.
The Incident
26. On 17 November 2008, one of the operators at the Plant was Mr Pat Freeman. He had been employed there for three years and had worked in the waste water industry for twelve years. Mr Freeman had the following qualifications in relation to sewage treatment:
a Certificate in sewage treatment activated sludge (November 2000, Department of Land and Water Conservation);
Certificate in Operation of Chemical Dosing Systems For Water Treatment Works (NSW Department of Land and Water Conservation, July 2001);
Certificate in Operation of Water Treatment Works (NSW Department of Land and Water Conservation, October 2002); and
Certificate 3 in Water and Wastewater industry (December 2003, NSW TAFE).