Page 2072 - Week 06 - Thursday, 9 June 2022

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(4) Was the public ever informed, as part of the community consultation in relation to the Belconnen Trunk Sewer Upgrade, that OCUs may release hydrogen sulphide into the air and/or cause nuisance odours; if not, why not?

(5) What is the elevation above sea level for the top of each odour control unit (OCU) ventilation stack planned as part of the Belconnen Trunk Sewer Upgrade.

(6) Were prevailing winds considered in any way in relation to the location or height of these OCU ventilation stacks; if so, in what way; if not, why not.

Mr Barr: I have sought Icon Water’s advice and the answer to the Member’s questions are as follows:

(1) Stack heights for the four Odour Control Units (OCUs) have been determined following the completion of air quality assessments which have included dispersion modelling.

North Latham: Details are provided in the Environmental Impact Statement (EIS) document, section 11. The EIS assumed a stack height of 24 m (table 11.7). This has been refined through the detailed design process (and verified with dispersion modelling) with a revised stack height of 15 m.

Latham, Florey and Evatt: Details are provided within their respective Air Quality Impact Assessments which were submitted with the Development Applications (DA). The assessment has assumed a stack height of 14 m (table 5.1). The detailed design has resulted in the stack height at Florey being slightly increased to 15 m. The other two sites remain at 14 m.

(2) Stack height is determined by air quality assessment and odour dispersion modelling. This determination also accounts for a variety of other factors including sensitive receiver locations, topography and local climatic conditions. The stack heights for the Belconnen trunk sewer project are as per the above.

(3) Technically, the ventilation stacks could be replaced with a larger unit. However, this action is not foreseeable given the dispersion modelling verifies that system performance is well within the compliance criteria.

(4) Information on the OCU function of filtering gases was included in consultation activities. Fact sheets created for this purpose are available on the Icon Water website at ( This information was included in community newsletters (delivered to homes in the area and emailed to members of the community who requested to be informed of updates). The topic is also covered in the FAQs available on the website. Furthermore, the developments have been subject to statutory planning approval processes including public notification.

(5) The elevation above sea level for each ventilation stack is provided below:

i. North Latham: 574.98 meters

ii. Latham: 574.696 meters

iii. Florey: 584.90 meters

iv. Evatt: 589.604 meters

(6) Yes, refer response to question 2 above. Please refer to the respective air quality assessment submitted with the EIS/DA’s.

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