Legislative Assembly for the ACT: 2022 Week 06 Hansard (Thursday, 9 June 2022) . . Page.. 2070 ..
(7) How many West Macgregor residents were consulted as part of the investigation referred to in part (6).
(8) Can the Chief Minister provide a summary of hydrogen sulphide levels as measured at the OCU ventilation stacks in West Macgregor from when they were gifted to Icon Water in 2010 until now.
(9) How frequently are the filters in an OCU cleaned and/or replaced.
Mr Barr: I have sought Icon Water’s advice and the answers to the Member’s questions are as follows:
1 Please refer to QON 3 to the Standing Committee on Public Accounts, which was provided on 7 April 2022. The height of the stacks (approximately 20m) was determined through a detailed investigation and design process to meet the performance requirements of the facility.
2. None of the West Macgregor Odour Control Unit Vent stacks have been raised since their installation and commissioning.
3. As per 2 above.
4. While hydrogen sulphide is often used as a proxy for odourous emissions it is not a measurement of odour itself. Icon Water is required to comply with concentration levels specified in the South Australian 2016 Environment Protection (Air Quality) Policy, as stipulated by the ACT Environmental Protection Authority (EPA). The policy states performance levels for both odour and other emissions. The design and performance of ventilation assets to meet these requirements is confirmed through computer modelling (which is site specific and influenced according to factors such as location, facility size, distance from sensitive receptors, terrain and meteorological conditions) and then managed over time through monitoring and operational controls. Because of the above factors, acceptable odour performance can be achieved with a range of hydrogen sulphide emissions from a ventilation asset dependent on climatic and meteorological conditions.
5. Hydrogen Sulphide is recorded at each of the West Macgregor OCU’s using permanent H2S monitoring on the vent outlets.
6. For the response to this question regarding investigations undertaken, please refer to the response to QON 10 which was provided to the Standing Committee on Public Accounts on 3 March 2022.
7. For the response to this question regarding consultations undertaken in an investigation, please refer to the above response and the responses to QON 10 which was provided to the Standing Committee on Public Accounts on 3 March 2022, and QON 3, which was provided to Ms Kikkert MLA on 7 April 2022.
8. The median outlet hydrogen sulphide concentrations at each facility and overall are shown below in Table 1. These values can be variable over time and as advised in QON3, performance against regulatory standards is impacted by a number of other factors. Hence a value recorded at the outlet does not represent the odour or hydrogen sulphide concentration at ground level.