140311 NSOOS Scrubber Decision Report Final...Scrubber\140307_NSOOS Scrubber Repl acement Decision report.docx Publication number SW199 3/14 Sydney Water - Commercial in Confidence

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Decision report

North Head Wastewater Treatment Plant NSOOS Scrubber Replacement Project

March 2014


© Sydney Water Corporation (2014) Commercial-in-Confidence. All rights reserved. No part of this document may be reproduced without the express permission of Sydney Water.

File Reference: S:\\Sustainability\EP&M\WASTEWATER\North Head\Replacing the NSOOS Scrubber\140307_NSOOS Scrubber Replacement Decision report.docx

Publication number SW199 3/14


Contents

1 Introduction 5

1.1 Purpose of the Decision report 5

1.2 Planning approval framework 6

1.3 Summary of the proposal from the REF 7

2 Consultation 8

2.1 Proposal development and REF preparation 8

2.2 Public exhibition of the REF 8

2.3 Submissions 9

2.4 Further consultation 9

3 Changes to the proposal 10

3.1 Amendment to REF contours 10

4 Summary of issues raised 11

5 Consideration of issues 13

5.1 Air quality (odour) 13

5.1.1 Objectives of proposal and odour performance 13

5.1.2 Efficiency of new scrubber 15

5.1.3 Scope of odour work 17

5.1.4 EPA guidelines and licensing 20

5.1.5 Managing odour at North Head WWTP 23

5.1.6 Effect of odours from North Head WWTP 25

5.2 Alternatives considered 26

5.2.1 Selection process 26

5.2.2 Design considerations 28

5.3 Community and stakeholder engagement 29

5.3.1 Consultation process for the proposal 29

5.3.2 Sydney Water complaints process 31

5.3.3 Decision report queries 32

5.4 Environmental management 32

5.4.1 Environmental performance and management of North Head WWTP 32

5.4.2 Construction environmental management 34

5.4.3 Flora and fauna 35

5.4.4 Waste management 35

5.4.5 Heritage 36

5.4.6 Traffic and chemical use 37

5.5 Scope of assessment, technical clarifications and corrections 38

5.5.1 Scope of assessment in the REF 38


5.5.2 Technical clarifications 40

5.5.3 Corrections 41

5.6 Support for the proposal 41

6 Justification of the proposal 42

7 Conclusion 43

8 Recommendation 44

9 References 45

Figures

Figure 1 Location of North Head WWTP (ESRI, 2013) 6

Figure 2 Artist’s impression of the NSOOS Scrubber Replacement Project 7

Figure 3 Predicted 2 odour unit contours with estimated (REF) and measured air flows 10

Figure 4 Predicted 2 odour unit contours for 1,000 and 500 odour units at outlet 17

Tables

Table 1 Issues raised in submissions 11

Table 2 Comparison of different odour concentration data and air flows for the NSOOS scrubber 15

Table 3 Upcoming projects which may influence odour from North Head WWTP 18

Table 4 Odour assessment criteria (EPA, 2006) 21

Table 5 Summary of potential impacts during operation of the proposal 38

Appendices

1 Community and stakeholder engagement

2 Submissions

3 Additional environmental measures


1 Introduction

The North Head Wastewater Treatment Plant (WWTP) is located on Blue Fish Drive, North Head, in the Manly local government area.

The WWTP is situated on the eastern side of North Head peninsula, which also includes the North Head Sanctuary (former School of Artillery), the Australian Institute of Police, Manly Hospital and St Pauls College. Sydney Harbour National Park borders the WWTP to the south and north, with the Tasman Sea to the east and north east (Figure 1).

North Head WWTP is the second largest wastewater treatment plant in Sydney, providing high rate primary wastewater treatment and operating 24 hours a day, seven days a week.

Chemical scrubbers are used at North Head WWTP to control odours associated with the transfer and treatment of wastewater. The scrubbers treat ‘foul air’, before discharging the air to atmosphere. The Northern Suburbs Ocean Outfall Sewer (NSOOS) scrubber is approaching the end of its useful life and needs to be replaced.

Sydney Water and the Odour Management Program Alliance (the Alliance) propose this North Head NSOOS Scrubber Replacement Project to improve the reliability of the WWTP and help reduce corrosion in the NSOOS.

The proposed works include:

replacing the existing chemical scrubber with a bio-trickling filter (BTF) scrubber, made up of nine units and associated infrastructure including duct work, a ventilation stack and water tank

modifying the underground ventilation system at the plant

decommissioning and removing the existing NSOOS chemical scrubber, once the bio-trickling filters are operational

completing associated infrastructure works, including work on internal roads.

We do not expect the proposal to cause any significant environmental or community impacts, once it is operational. The proposal should slightly improve odour impacts on the surrounding community.

Sydney Water and the Alliance completed a Review of Environmental Factors (REF) for the proposal in October 2013. We placed the REF on public display from 28 October to 11 November 2013 and invited community members and other interested stakeholders to comment on the proposal in the REF.

Sydney Water received 20 submissions, following the public exhibition of the REF. These raised issues related mainly to air quality and odour, the scope of the proposal, alternatives considered and environmental management during construction.

We have not significantly changed the proposal since public exhibition of the REF. However, we have included several new mitigation measures to address some of the issues raised in submissions.

This Decision report addresses issues raised in the submissions.

1.1 Purpose of the Decision report This Decision report:

considers the issues raised in submissions

identifies and assesses whether the submissions require any changes to the proposal

identifies whether the submissions require any new mitigation measures, or changes to existing mitigation measures

recommends whether Sydney Water should proceed with the proposal.


Figure 1 Location of North Head WWTP (ESRI, 2013)

1.2 Planning approval framework The Environmental Planning and Assessment Act 1979 (EP&A Act) provides the statutory context for the proposal’s environmental assessment. We are assessing and determining the proposed work under Part 5 of the EP&A Act, with Sydney Water the determining authority. The State Environmental Planning Policy (Infrastructure) 2007 allows Sydney Water to complete the work without development consent from Manly Council.

The REF assessed the potential environmental impacts associated with replacing the NSOOS scrubber and associated infrastructure. We considered potential impacts against the matters listed in clause 228 of the Environmental Planning and Assessment Regulation 2000 (EP&A Regulation).

Our assessment concluded that it is unlikely that the proposal will have a significant impact on the environment. We have not changed this conclusion after considering the submissions, so an environmental impact statement is not required.


1.3 Summary of the proposal from the REF The North Head NSOOS Scrubber Replacement Project (the ‘proposal’) involves:

replacing the existing NSOOS chemical scrubber with a new bio-trickling filter (BTF) scrubber which will be more reliable. The scrubber includes nine BTF units and associated water tank, pipe and duct work and a ventilation stack

modifying the underground ventilation system

decommissioning and removing the existing NSOOS chemical scrubber

installing associated infrastructure and services, and work on internal roads.

We will be completing work both above and below ground. Figure 2 shows the layout of the proposal.

Figure 2 Artist’s impression of the NSOOS Scrubber Replacement Project

Vent stack

BTF towers Pipe and ducting work

Water tank


2 Consultation

Sydney Water developed a communication strategy to ensure the local community and key stakeholders are given clear, accurate and timely information during the proposal’s various stages. We identified key stakeholders according to their interests of the proposal’s potential impacts.

As part of the communication strategy, we consulted with the local community and key stakeholders while preparing and exhibiting the REF. This includes preparing and displaying the REF, considering submissions and preparing this Decision report. Appendix 1 includes examples of the consultation completed for this proposal. The following sections describe the consultation to date. We will continue to inform the community and key stakeholders about the proposal.

2.1 Proposal development and REF preparation While preparing the REF and developing the proposal, we:

wrote to key stakeholders, in July 2013, seeking input for the REF

presented information about the proposal with key stakeholders before the REF public display, including:

- North Head WWTP Community Consultative Committee (CCC), on 14 August 2013

- Manly Council Community Environment Committee, on 11 September 2013

- North Head Sanctuary Foundation, on 12 September 2013.

set up a community information line, website, and email address.

2.2 Public exhibition of the REF The REF was on public exhibition from 28 October to 11 November 2013 at:

Manly Council, Customer Service Centre, 1 Belgrave Street, Manly

Manly Library, Market Place, Manly

Manly Environment Centre, 41 Belgrave Street, Manly

Sydney Water invited the community and stakeholders to provide comments or submissions on the proposal. The deadline for REF submissions was initially 15 November 2013, however we extended this to Friday 22 November 2013 to meet requests from a number of submitters. During exhibition of the REF, we consulted with the community and stakeholders and invited comments and submissions by:

advertising the REF in the Manly Daily on 26 October 2013 (a copy of the newspaper advertisement is attached in Appendix 1)

holding a drop-in information session at Manly Community Centre on 4 November 2013 from 4 pm to 6 pm. At the session, we provided information including printed and CD copies of the REF, photographs and images of the plant and the proposal, and a fact sheet summarising the project. Staff from both Sydney Water and the Alliance were available to answer questions from the community. Ten community members attended the session.

placing the REF and other proposal information on the Sydney Water Talk website (sydneywatertalk.com.au)

delivering a newsletter about the proposal to local residents through a letter box drop

mailing copies of the REF to key stakeholders. We sent 14 hard copies, 10 CDs and one electronic copy to the following stakeholders:

- local Member of Parliament for Manly

- Manly Council


- Manly Council Community Environment Committee

- Fairy Bower and Little Manly Precinct Committees

- Manly Environment Centre

- Sydney Harbour Federation Trust

- Manly Hospital

- NSW Environment Protection Authority

- NSW National Parks and Wildlife Service

- representatives of the North Head WWTP Community Consultative Committee

- School of Artillery and National Artillery Museum

- St Paul's Catholic College

- Saint Patrick’s College and the Cardinal’s Palace

- Gatehouse Visitors’ Centre

- North Head Stakeholder Group

- Friends of Quarantine Station

- Australian Institute of Police Management

- International College of Management

- North Head Sanctuary Foundation

- Headland Montessori

responding to community and stakeholder enquiries during proposal development, the REF public exhibition period, and to date.

In total, we sent about 1,725 letters to stakeholders and local residents. After exhibiting the REF, Sydney Water and the Alliance prepared this Decision report to address the issues raised in submissions. We will distribute it to stakeholders who made a submission.

2.3 Submissions We received the following enquiries and submissions in response to the REF:

3 calls to the community information line

2 emails to the project email address

10 attendees at the information session

20 submissions on the proposal (both hard copy and to the email address).

Sections 4 and 5 address issues raised in these enquiries and submissions. Appendix 2 includes copies of submissions received.

2.4 Further consultation Sydney Water is committed to informing and consulting the community and stakeholders throughout the proposal’s design, construction and operation. This will ensure the community and stakeholders are kept informed and that we understand their issues and concerns. During the construction phase of the project, the Alliance will work with Sydney Water to develop and implement a Community Liaison Plan in line with Sydney Water’s Communications Strategy and Stakeholder Engagement Policy for the project.

The Alliance must keep the community informed throughout construction and manage issues and complaints. After commissioning, Sydney Water’s standard policies and procedures for customer and community relations will apply.


3 Changes to the proposal

Sydney Water has not significantly changed the proposal since public exhibition of the REF. However, we have included several new mitigation measures to address some of the issues raised. These are identified in section 5 and Appendix 3.

3.1 Amendment to REF contours After issuing the North Head NSOOS Scrubber Replacement REF for public exhibition, Sydney Water received revised air flows for the cogeneration plant and waste gas flare from our consultants. The revised flows were based on actual measurements (rather than estimates) and changed the predicted 2 odour unit contours slightly. Figure 3.1 shows the estimated air flows identified in the REF (dotted line) and the measured air flows (solid line). In terms of impact assessment, there is no substantial difference between the contours, and the conclusions in the REF remain the same.

Figure 3 Predicted 2 odour unit contours with estimated (REF) and measured air flows


4 Summary of issues raised

This chapter summarises the 20 submissions we received, from 28 October to 22 November 2013, in response to public exhibition of the REF. These included submissions from 12 community members, four from the local community precincts (North Harbour, The Corso, Little Manly and Fairy Bower), and one from each of Manly Council and Manly Council Community Environment Committee, NSW National Parks and Wildlife Service, Sydney Harbour Federation Trust, and North Head Sanctuary Foundation.

We identified 23 different issues from the submissions and categorised them into six summary issue groups (outlined in Table 1). Table 1 gives each submission number, details the number of times an issue was raised and where we have addressed it in the Decision report.

We have listed all submission authors in Appendix 2 and included the submissions, as requested. We have omitted names and addresses of private individuals and community members, as required by the Privacy and Personal Information Protection Act 1998.

Section 5 includes our responses to the issues raised in the submissions.

Table 1 Issues raised in submissions

Submission number

Summary issue Number of submissions raising this issue

Location where issue is addressed in REF

Location where issue is addressed in Decision report

Air quality (odour)

3, 5, 7, 8, 9, 12, 17, 19, 20

Objectives of proposal and odour performance

9 4.1 5.1.1

3, 4, 7, 8, 9, 11, 12, 13, 14, 15, 16, 18, 19, 20

Efficiency of new scrubber 14 5.4 5.1.2

3, 5, 6, 7, 8, 9, 11, 16, 17

Scope of odour work 9 5.4 5.1.3

3, 7, 8, 9, 15, 17, 18, 19, 20

EPA guidelines and licensing 9 5.4 5.1.4

1, 2, 3, 5, 6, 9, 14, 15, 16, 17, 18, 20

Managing odour at North Head WWTP

12 5.4 5.1.5

2, 3, 6, 7, 8, 14, 15, 17, 19

Effect of odours from North Head WWTP

9 5.4 5.1.6

Alternatives considered

3, 4, 7, 8, 15, 19 Selection process 6 3.3 5.2.1

3, 11, 15, 16, 17, 20

Design considerations 6 3.3 5.2.2

Community and stakeholder engagement

1, 3, 4, 7, 8, 11 Consultation process for the proposal

6 1.3 5.3.1

3, 5, 9, 18 Sydney Water complaints process

4 - 5.3.2


Submission number

Summary issue Number of submissions raising this issue

Location where issue is addressed in REF

Location where issue is addressed in Decision report

3 Decision report queries 1 - 5.3.3

Environmental management

7, 8, 9, 11, 12, 13, 14, 16, 18, 19, 20

Environmental performance and management of North Head WWTP

11 - 5.4.1

1, 2, 6 Construction environmental management

3 6.1 5.4.2

1, 6 Flora and fauna 2 5.3 5.4.3

3, 4, 9, 15, 16, 19 Waste management 6 5.6 5.4.4

2, 15, 16 Heritage 3 5.7 5.4.5

16 Traffic and chemical use 1 5.8, 5.10 5.4.6

Scope of assessment, technical clarification and corrections

3, 15, 16 Scope of assessment in the REF

3 - 5.5.1

3 Technical clarifications 1 - 5.5.2

3 Corrections 1 - 5.5.3

Support for the proposal

10 Support for the proposal 1 - 5.5.1


5 Consideration of issues

This chapter outlines the issues raised in the submissions that we received in response to the REF public exhibition period. We have reviewed each submission and identified and categorised concerns, based on the chapters and issues in the REF. Appendix 2 includes the list of submissions and their reference number.

As many submissions raised concerns on related issues, we have grouped submissions for clarity of response. Where possible, we have extracted phrases from the submissions to ensure the meaning is accurately portrayed.

If a submission raised several issues, the submission number will appear in many sections. We have aimed to address every issue raised, and to correctly interpret the meaning in the submissions. We focussed on the content of each submission that raised concerns or questions about the proposal. This means we have usually not addressed points that noted or supported a finding from the REF.

5.1 Air quality (odour) Most of the submissions identified odour from the WWTP as the main issue of concern. We broadly categorised these issues as relating to:

objectives of the proposal and odour performance

concerns around the efficiency of the new scrubber

disappointment expressed at the scope of odour work proposed

how the EPA guidelines and licensing are relevant to the proposal

management of odour from North Head WWTP

concerns about the effect of odour from North Head WWTP

5.1.1 Objectives of proposal and odour performance

Objective of proposal should be odour reduction not just renewal/replacement

Many submissions (3, 6, 5, 7, 8, 9, 15, 16) noted that the objectives of the proposal relate to replacing the existing scrubber and improving underground ventilation only. It was suggested that the objectives should have included ‘significant odour reduction’ as the Malabar and Cronulla Odour Management Projects did. Submission 3 suggested the primary reason for the scrubber should be to reduce odours from the NSOOS and underground to a level acceptable for release into the atmosphere. Submissions 7 and 8 indicated the objectives should be to reduce long-term odour effects on the surrounding population of Manly, and guaranteed reduction in odour from the entire facility.

Response

The objectives for this proposal are different to the Malabar and Cronulla odour management projects.

The objectives for this proposal were identified in the NSOOS Scrubber Replacement REF to:

replace the existing NSOOS scrubber before the existing scrubber reaches the end of its useful life

reduce corrosion and increase the air flow within the NSOOS.

These objectives are about replacing an aged asset to improve performance and reliability.

Significant odour reduction was not an objective for this proposal as:

replacing the NSOOS scrubber is the latest in a long program of reliability upgrade works at North Head WWTP, which have already significantly improved odour from the plant


Malabar and Cronulla WWTPs had not had the previous odour management works that North Head had, and their processes are different. North Head WWTP already has three scrubbers treating odour

we are taking a staged approach to odour management at North Head WWTP. This is discussed in more detail in section 4.1.3.

Previous odour management work at North Head

From 2005 to 2009, the Performance and Reliability/Renewal (PARR) project involved whole-scale changes to North Head WWTP. Work specifically relating to reducing odour included:

amending the biosolids storage building and developing the Central Scrubber to capture and treat odours

closing the M1 building and above ground screenings handling (dewatering and placing into skip bins). Screenings handling is a source of odour. The screenings handling was moved below ground so the NSOOS scrubber could treat odorous air from the relocated screenings handling facilities

installing the cogeneration engine which takes biogas from the waste gas flare. The cogeneration engine has proven to be effective at reducing odour emissions, compared to the waste gas flare

installing three digesters to replace the lime dosing/stabilisation process. The digesters increase solids retention times, which reduces volatile solids content, odour and volume of the sludge/biosolids

managing general odour activities, such as amending maintenance procedures.

A review after the PARR work was completed confirmed that the work had successfully reduced total odour emissions from the WWTP, and the extent of the 2 odour unit contour, noting that some receivers were still within the 2 odour unit contour. The review identified that the next project which could further reduce odour would be to do work on, or replace, the NSOOS scrubber, as we now propose. A benefit of this proposal is that the work will slightly reduce odour impacts on the surrounding community.

While we acknowledge that there can be some odours, we are actively planning and working to reduce odours where possible. This is consistent with our staged approach for North Head WWTP.

Proposal is seen as inferior to odour management work at Malabar and Cronulla WWTPs

Some submissions (5, 12, 15,19, 20) suggested that the North Head proposal being scrubber replacement only, was not in line with work at other facilities (such as Malabar and Cronulla odour management projects) and that the North Head proposal is inferior. Submission 17 (North Head Sanctuary Foundation) requests that the residents of North Head and Manly have the same standard as residents of Malabar. Submission 19 states that the Malabar proposal provides the community with an odour free environment, but North Head doesn’t.

Response

As identified above, the Malabar and Cronulla odour management projects included an objective to ‘significantly reduce the risk of odours impacting the surrounding community’. However, given the previous odour management work at North Head WWTP, this proposal focussed on asset renewal. Each WWTP within the Sydney Water operating network is unique and we program work in response to their different needs.

Both the Malabar and North Head projects are essentially renewal projects where existing scrubbers are being replaced with new ones. At Cronulla, minimal odour control had been installed at the WWTP and new urban development was being planned near the boundary. As a result, the Cronulla project included additional scrubbing and odour containment.

Each of the three scrubbers has the same performance requirement of 1,000 odour units. BTF technology has been installed at Cronulla, and is proposed for North Head, while Malabar uses chemical scrubbing. The alternatives and options selection process was similar across each of the three sites, but refined to meet the individual requirements of each WWTP.


The new NSOOS scrubber will reduce the impact of odour on the community, by providing a more reliable facility that will provide consistent odour levels, unlike the current scrubber that is subject to process upsets, due to its age and configuration. In addition, the new BTF scrubber will also reduce the 2 odour unit contour of the WWTP. Sydney Water will continue to monitor odour during and after the work is complete. This includes monitoring performance of the WWTP and odour treatment facilities, and operating the WWTP to meet the NSW Environment Protection Authority (EPA) licence.

At all our WWTP sites, we aim to minimise community and environmental impacts.

5.1.2 Efficiency of new scrubber

Replacement scrubber design should be as efficient as existing scrubber

Submissions 3, 4, 7, 8, 11, and 15 consider it unacceptable for the performance of an ‘end-of-life’ scrubber to be used as a baseline for the new scrubber. Many submissions (9, 11, 12, 13, 14 15, 16,18, 20) expressed concern that the new scrubber is seen as less environmentally efficient than the existing equipment in 2003–04. Some submissions (3, 4, 15) referred to a 2004 report commissioned by Sydney Water to inform the concept design for the PARR Project; North Head STP PARR Project Concept Design Odour Review (MWH, 2004). This report referred to the NSOOS chemical scrubber having an odour concentration of 630 odour units, and a corresponding emission rate of 18,270 ou.m3/s. Submissions suggested that these numbers should be the minimum performance levels for the new BTF scrubber. Submission 3 asked how we obtained the figures of 1,900 ou/m3 and 55,290 ou/s and the range of values from which we derived these figures. Some submitters (3, 4, 7, 8, 15, 16) suggest that odour emissions will increase from the current proposal, compared to the 2004 report.

Response

In 2012, CH2M HILL reviewed historical odour data for the existing NSOOS chemical scrubber to use in dispersion modelling. Fourteen datasets were available, from the years 1998, 2000 and 2010, with outlet measurements ranging up to 8,995 odour units. Most results were above 1,000 odour units. They analysed the data and discarded inconsistent data (two results) before calculating minimum, maximum, average and 50 and 90th percentiles for both the inlet and outlet. CH2M HILL recommended an odour concentration of 1,900 odour units be used for modelling. We agreed that this figure would reflect typical emissions from the existing NSOOS scrubber. We have not recently measured odour emissions from the NSOOS scrubber.

The MWH (2004) report was prepared to inform concept design decisions for the PARR Project, and was not an odour impact assessment. This report used an odour concentration of 630 odour units for the NSOOS chemical scrubber. However, modelling indicated that there is little difference in off-site odour emissions between the 500 and 1,000 odour unit scrubber scenarios (more detail included below).

The new BTF scrubber will be able to treat more air than the existing chemical scrubber, increasing from 29m3/s to 35m3/s. This represents an increase in flow, meaning the scrubber can treat more ‘foul’ air, but this is not an increase in odour impact. Similarly, while the performance guarantee for the proposed BTF scrubber is 1,000 odour units, we expect better performance, in the range of the originally designed scrubber. We took a conservative approach during the REF assessment, showing the ‘worst case’ scenario. More detail is provided in Table 2.

Table 2 Comparison of different odour concentration data and air flows for the NSOOS scrubber

Data source Odour units

Air flow

Odour emission rate

Explanation of data

MWH (2004) report

630 29 18,270 Data not available for confirmation. 500 and 1,000 odour unit contours very similar.

Existing scrubber (estimated)

1,900 29 56,500 1,900 recommended for dispersion modelling after reviewing and analysing historical measurements.


Data source Odour units

Air flow

Odour emission rate

Explanation of data

Proposed BTF scrubber

1,000 35 35,000 1,000 odour units is manufacturer’s guarantee, and was modelled as conservative ‘worst case’ scenario (as per EPA Guidelines). We generally expect better performance. Increased airflow, to treat more foul air.

Expected (but not guaranteed) general performance of BTF scrubber

500–1,000 35 17,500–35,000 The proposed BTF scrubber is expected to achieve less than 1,000 odour units at the outlet. We are introducing a number of improvements to standard BTF designs that should result in better performance. We are unable to quantify the amount and as a result, modelled the performance guarantee of 1,000 odour units.

After commissioning, we will monitor odours and test performance to confirm that the proposal meets the manufacturer’s performance guarantee of less than 1,000 odour units.

A scrubber that can achieve 500 odour units should be installed

Some submissions (3, 4, 12, 15, 19) suggested that the proposal should have a 500 residual odour concentration and asked how the 1,000 odour concentration was selected. A reference to the Malabar Odour Management Decision Report was quoted ‘in order to reduce the impact of odours on the community, the odour concentration at the exhaust from the scrubber would be reduced from 1,000 to 500 ou/m3’ and the submission asked why there has been a reduction in standards compared to the 2004 report and at Malabar.

Response

During option selection, scrubbers with both 500 and 1,000 odour units were considered to replace the NSOOS chemical scrubber. A biological scrubber with a performance guarantee to 500 odour units residual would require a second stage carbon ‘polishing’. Preliminary modelling (refer Figure 4) indicated a negligible difference between the two odour contours, however with significant extra cost and site constraints. As mentioned above, actual general performance of the proposed scrubber is expected to be better than 1,000 odour units, however the modelling used 1,000 odour units to ensure a conservative approach.

Both the recently refurbished Malabar (chemical) and the proposed North Head (BTF) scrubbers are guaranteed to 1,000 odour units, however can perform below this level. The outlet odour performance of a scrubber can be influenced by different conditions such as temperature and upstream dissolved sulphide concentrations. Our dosing units project will help reduce dissolved sulphide concentrations in the NSOOS which will also reduce the odour levels emitted from the outlet of the new BTF scrubber at North Head.

New scrubber is seen to increase atmospheric pollution

Submissions 3, 4, 7, 8, 9, 15, 16 and 18 state that the proposal will increase atmospheric pollution (emissions) compared to the present scrubber or to 2004 levels. This was described as 90% higher or double in some submissions (4, 15, 16). Submission 3 states that since the odours from the WWTP were not acceptable in 2004, why should a doubling in odour emission levels from the proposed replacement device be acceptable now?

Response

The proposal will not increase atmospheric pollution. Modelling indicates that the existing NSOOS scrubber is the main contributor to odour from North Head WWTP. The proposal will reduce emissions from about 56,500 ou/s to 35,000 ou/s or better. The REF predictions of only a slight improvement in odour emissions from the WWTP were based on a worst-case scenario to ensure a conservative assessment. This means it potentially over estimates potential odour emissions.


Figure 4 Predicted 2 odour unit contours for 1,000 and 500 odour units at outlet

The proposal also involves improving scrubber performance and improving reliability. The BTF will result in fewer incidents where hydrogen sulphide exceeds expected performance, and lower peaks in odour.

5.1.3 Scope of odour work

Scope of work is too limited and further odour upgrade work requested

Submissions 6 expressed disappointment in the level of odour reduction and asked for further odour reduction. Submissions 3, 7, 8 and 11 suggest the scope of the proposal is too limited and ‘piece-meal’, and that Sydney Water should do a holistic review to reduce long-term odour effects on the surrounding population of Manly. Submission 9 is pleased the work is being funded, but thinks it is not enough of an upgrade to provide comfort. Submissions 7 and 8 note that the community may be asked to review a number of REFs if work is done in stages. Sydney Water was urged to do further upgrade work to mitigate odour and minimise disturbance to residents (Submissions 5, 6, 7, 8). Submission 3 states that the fact that gases from the scrubber contribute to the foul odours emanating from the WWTP is not considered in the REF. Submissions 7, 8, 16 stated the NSOOS scrubber is responsible for under 50% of odour emissions and that other odour generating facilities/operations also require upgrading, such as the primary sedimentation tanks, cogeneration facility, flare and biosolids handling.


Response

We did not complete a whole of plant/holistic review of operations for this proposal because:

the recently completed PARR work was a major refurbishment of the plant and significantly reduced odour emissions

the review that followed the PARR work identified work on the NSOOS scrubber as the next major work to further reduce odour emissions

this proposal is only one part of a staged approach to manage and improve odour from North Head WWTP

we are planning a number of other projects to help reduce ‘whole of plant’ odours. These are identified in Table 3.

Table 3 Upcoming projects which may influence odour from North Head WWTP

Upcoming / planned projects

Timing Implications for odour reduction

NSOOS Scrubber Replacement Project and improvements to underfloor ventilation

We are continuing planning and design work for this project. We anticipate that construction will commence in March or April 2014, with commissioning scheduled for late 2015 to early 2016 with final completion by mid-2016.

The proposal should slightly improve odour impacts on the surrounding community. Post-commissioning monitoring will confirm performance of the BTF scrubber. The proposal also includes modifying the underground ventilation system. We anticipate this will also help reduce odour emissions from the decline tunnel.

Installing dosing units within the network

Planning for this work is underway. Commissioning of these projects is likely to be early to mid-2015.

The dosing units are at a preliminary stage in proposal development, however they are quicker to plan and construct than the NSOOS scrubber. While the dosing units are primarily to protect critical infrastructure, they can potentially also reduce odours. We believe that reducing the hydrogen sulphide load within the pipe network may also reduce odour at the WWTP. We are currently assessing three dosing units, but as we cannot quantify the odour improvements that these will achieve, we would not normally include them in odour modelling. To include these proposals would delay the NSOOS scrubber replacement REF which is relatively urgent.

Developing trade waste controls at large point sources

Finalise first trade waste control mid- 2014

Trade waste controls will reduce hydrogen sulphide load within the network. The work is focussed on reducing corrosion locally, however, we think the work may have an impact on odour from North Head WWTP by reducing total odour arriving at the plant for treatment. We are unable to quantify the effect of this and so, it has not been included in the modelling.

Installing a second cogeneration plant

Commissioning scheduled for mid-2014

This will take most of the biogas currently going to the flare. The flare has a higher odour output than the existing cogeneration plant. This means it should slightly reduce odours from the WWTP, once complete.


Upcoming / planned projects

Timing Implications for odour reduction

Additional waste gas flare

Project currently in planning stages. Indicative commissioning mid- 2015

We will install an additional waste gas flare as ‘duty assist’. This means it will be used when the existing flare is undergoing maintenance, or when there is a very high volume of biogas, which exceeds the capacity of the existing flare. This could occur a few times each year. The additional flare will be similar to the existing waste gas flare. The revised air flow measurements (discussed in Section 3) show that the waste gas flare is the second largest contributor to odour emissions, after the NSOOS scrubber. As stated above, it is intended that the second cogeneration plant will take all available biogas, however, if the cogeneration engine is shut down the flares are used. The flares must be able to take 100% of biogas load. The new flare should be more reliable and efficient than the existing flare.

Once all these works are complete, we will do a benefits realisation study to determine the levels of odours and performance of the new facilities. While the REF took a conservative assessment approach, these projects should noticeably improve odour emissions beyond the WWTP boundary.

As required under the Environmental Planning and Assessment Act 1979 (EP&A Act), we assess all our activities with potential environmental impacts. We are not required to place these assessments (usually REFs) on public exhibition, but we have for this proposal, due to the high levels of community interest. We will continue with this approach, balancing community involvement and interest with the need to finalise projects. We always aim to minimise impacts on the environment and community.

Additional projects described in REF should be part of the proposal

Submissions 7, 8 and 9 expressed concern that the proposal didn’t include the additional projects identified in the REF (for example dosing units) and queried why they weren’t part of the proposal, or included in the modelling. The submissions asked when these projects will occur and would they improve odour control. Submissions 7 and 8 said the community expects these projects to be done.

Response

The proposal focuses on replacing the existing chemical scrubber, as this is fairly urgent work. The modelling for the REF followed the EPA guidelines, and included the worst case scenario from the BTF scrubber. We expect better performance than predicted (refer section 5.1.2).

Table 3 identifies other projects that are currently being planned. We had to assume no odour reduction from these projects for the REF, to ensure we robustly assessed the potential impacts of the NSOOS scrubber.

These projects weren’t included in the scope of the proposal or REF as they are not directly related to the NSOOS project and they are at different stages of planning and assessment. We will review the success of the projects once complete.

Consideration of the odour emissions of the whole plant should be included

Submission 3 stated that Sydney Water should consider odour levels from the whole plant to inform appropriate design parameters for the proposed NSOOS scrubber, the purpose of which is to treat odours. Submission 11 suggests that the REF does not, but should, address all sources of odour from the plant. Submission 17 says the REF should have involved auditing sources, identifying and potential treatment solutions and resolving which matters resulted in the most effective odour reduction. The submitter states that the site sources are not regularly and effectively monitored, and accordingly this data needs to be gathered before embarking on significant expenditure which may or may not deal with the source of the most noxious odours.

Response

These submissions relate to two issues:


The assessment in the REF should have taken into account all odour sources.

The proposed scrubber should be designed to treat all odour sources from the WWTP.

The air quality assessment in the REF considered the different sources of odour from North Head WWTP, including the NSOOS, central and NST scrubbers, decline tunnel, waste gas flare, primary sedimentation tanks and cogeneration engine. This is why only a relatively small improvement can be seen in the odour emission contours. Dispersion modelling of the proposed BTF scrubber only shows a very small odour contour and a large improvement in emissions. This gives us confidence that the proposal will help reduce odours from the WWTP. We modelled all sources in the air quality assessment, as required by the EPA guidelines. The modelling used previous monitoring data for the scrubbers, decline tunnel and primary sedimentation tanks, and recent measurements taken for the cogeneration and waste gas flare.

The proposed scrubber is not designed to treat all odour sources from the WWTP. The NSOOS scrubber treats air from the NSOOS and the underground area only. At North Head, three scrubbers are used to treat foul air. Both the central and Northside Storage Tunnel scrubbers are performing appropriately. It would be difficult to build a scrubber that could capture and treat all the different sources of odour from North Head, which is why we use a range of measures and technologies to manage odour.

We will continue to use existing odour controls, including operational procedures like securing doors and hatches, to maintain ventilation. We will also install the second cogeneration plant and waste gas flare and other projects to help improve odour. Once all these projects are complete, we will review odour from the WWTP and consider whether additional work is necessary.

5.1.4 EPA guidelines and licensing

Sydney Water should be planning to contain odours at the WWTP boundary

Many submissions (3, 5, 6, 9, 15, 17,19) noted the nearby sensitive receivers and stated that Sydney Water should be planning to contain odours at the WWTP boundary, and building a plant that could meet this requirement. Submission 17 states that the North Head WWTP post-dates most uses at North Head and should operate in a manner that does not impact pre-existing users, noting there are residents close to the boundary (about 400 m away). Submissions 7 and 8 suggest a guarantee to keep odour emissions to a minimum on North Head, where the public has access.

Response

We are not required to contain odour at the boundary. However, we operate our plant to avoid off-site odour emissions. Previous monitoring suggests the NSOOS scrubber is a cause of intermittent off-site odour, and a benefit of this project is that odour emissions from the NSOOS scrubber will reduce, and so will emissions from the WWTP. Table 3 above identifies the different projects that will help us further improve odour emissions from the WWTP.

As to North Head WWTP impacting pre-existing users, the NSOOS was constructed between 1916 and 1933, and the WWTP completed in the 1970s. North Head WWTP treats wastewater from over one million customers in Sydney, generally with minimal impacts on the community or the environment. We continually work towards minimising our impacts on the community. While some sensitive receivers (such as the school and childcare centre) have moved in recently, the proposed work will reduce odour emissions from the WWTP and we hope to continue to work effectively with our old and new neighbours.

The proposal will help us reduce odour emissions from the WWTP.

Odour contour does not meet EPA criteria for sensitive receivers

Many submissions (3, 7, 8, 15, 17, 20) note the REF predicts odour emissions outside the boundary of the WWTP. The submissions state this is inconsistent with the DECCW (EPA) ‘Odour Assessment Criteria’. Some submissions (15, 17, 19, 20) identify particular sensitive receivers, that they say will be affected by odour, including Manly Hospital, and the new primary school. The submissions state that sensitive receivers should be in contours of less than 2 odour units, to meet


the EPA guidelines, but are in contours of 3 to 4 odour units. A map was included to identify sensitive receivers.

Submission 17 maintains the objective should be to reduce odour to no more than 1 odour unit at the boundary, and zero where people are occupying premises for 24 hours a day, such as homes and hospitals. The submission states that the DECCW odour criterion line includes areas of 24 hour occupation and is not acceptable on a health or risk level, or amenity.

Response

Section 5.1.6 addresses potential health risks from odour.

The two relevant guideline documents relating to odour are the:

Technical framework: assessment and management of odour from stationary sources in NSW (DEC/EPA, 2006) ‘the framework’

Approved Methods for the Modelling and Assessment of Air Pollutants in NSW (DEC/EPA, 2005) ‘the approved methods’.

Both documents reference ‘Odour assessment criteria’ which are to be used during project planning for a new or modified project, to predict and assess odour impacts. The criteria were presented in the REF (page 43) and are included here in Table 4.

Table 4 Odour assessment criteria (EPA, 2006)

Population of affected community Odour assessment criteria (OU)

Rural single residence (<2) 7.0

<10 6.0

<30 5.0

<125 4.0

<500 3.0

Urban area (>2000) and/or schools and hospitals 2.0

It is important to note that the figures included in the REF showing the 2 odour unit contours are for the 99th percentile. This means it is what we predict will happen 1% of the time, or one hour in one hundred. It is designed to be precautionary, so we can minimise impacts on sensitive receivers. The contours show that, from time to time, there may be some odour emissions (equivalent to 2 odour units) at some sensitive receivers.

The framework was developed to provide guidance for assessing and managing activities that emit odour. Its key principles are planning to prevent and minimise odour, using a range of strategies to manage odour, and ongoing environmental improvement.

The framework says the criteria are best regarded as project planning tools and are used to assess the likely performance of a project and acceptability of impacts to ‘sensitive receptors’ (or receivers). As such, they are based on ‘worst case’ or extreme events.

The framework explains that the level at which an odour is perceived to be of nuisance ranges from 2 to 10 odour units, and that everyone experiences odour differently. A person standing on the 2 odour unit contour will not necessarily notice an odour. The range can depend on a number of factors, such as odour quality, intensity, frequency, population sensitivity and public expectations.

The odour assessment criteria of 2 odour units are used as a precautionary calculation to minimise or avoid impacts to sensitive receivers. ‘Acceptable odour’ is defined as 2 odour units for receivers that have large populations, in which there will be a greater range of sensitivities to odour (and a higher number of more sensitive individuals).

Odour dispersion modelling is not an exact science and odour emissions are difficult to monitor (DEC, 2006). As a result, the framework says the criteria are to be used as a design tool, to predict odour impacts, rather than as a regulatory tool.


The submissions incorrectly state that the proposal is inconsistent with the framework and odour assessment criteria, because there is a school and hospital in the 2 odour unit contour. The framework doesn’t prohibit sensitive receivers in this contour, but indicates there is a higher likelihood that people who are sensitive to odour may be within that area.

The framework is not a regulatory tool.

Our proposal is consistent with the framework and its key principles:

Planning to prevent and minimise odour by

- following the assessment approach identified in the framework

- modelling using the approved methods and relevant odour assessment criteria

- adopting a precautionary approach by modelling ‘worst case’ scenario, so we are expecting performance to be better than predicted.

Using a range of strategies to manage odour, including:

- using the 2 odour unit contour to guide decisions for the whole plant

- using best practice technology to reduce odour emissions

- continuing to consult with our neighbours and other regulatory bodies about land use planning and odour management.

Ongoing environmental improvement by:

- identifying mitigation measures, including other projects (refer Table 3 above), which will also help reduce odour emissions from the plant

- committing to reviewing the success of this proposal and the other projects once work is complete.

Sydney Water aims to minimise odour impacts on sensitive receivers, and this proposal supports that aim.

New scrubber won’t meet ‘ongoing improvement’ requirement in Environmental Protection Licence

Submissions 3, 9, 15,16 and 20 question how the proposal will meet the EPA licence requirement to ‘manage, operate and maintain the reticulation system and WWTP so that operational and maintenance activities result in ongoing improvement’. Submissions 9, 16 and 20 ask where is the improvement when emissions have substantially increased since 2005?

Response

The matters relating to perceived emission increases are discussed in section 5.1.2.

The existing NSOOS scrubber was built in 1992 and reconfigured in 1997. Over time, it has become less reliable at capturing and treating the hydrogen sulphide levels from the NSOOS. Hydrogen sulphide levels have exceeded licence limits on occasion.

We have been operating and maintaining the scrubber, however some key design parameters are now inadequate. This is why we propose replacing the scrubber with a more efficient and robust system.

We will continue to comply with our Environmental Protection Licence, and the proposal has been designed to meet the requirements of ongoing improvement.

No recourse available if odour emissions higher than predicted

Submissions 7, 8 and 18 expressed concern that the community has no recourse if odour emissions are higher than predicted. Submissions 7 and 8 noted that there was no undertaking or guarantee from Sydney Water that the new scrubber would reduce odour emissions. If it didn’t, the community cannot force Sydney Water to make investments to reduce odour emissions to an acceptable level. The community needs recourse the replacement scrubber odour concentration exceeds an agreed baseline. The emissions must be monitored by an independent authority and, if it does not meet agreed standards, Sydney Water must fix the problem.


Response

We will be testing the effectiveness of the scrubber during the commissioning of this project to ensure it meets the agreed 1,000 odour units. The Alliance will be required to make any changes required to ensure the performance limit is met.

We currently monitor hydrogen sulphide (and other emissions) from the NSOOS scrubber as required by our Environmental Protection Licence. We will continue to monitor emissions and report these to the EPA, and will publish the results of our monitoring on our website.

5.1.5 Managing odour at North Head WWTP

Existing odour from the plant

Submissions 1, 2, 3, 5, 6, 14, 17 and 20 stated there are ‘numerous occasions’ when odour from North Head WWTP is offensive/unpleasant and that this can significantly affect enjoyment of the area. Some submissions note they are located within the odour contour or affected by odour (5, 6 9). Submission 20 said odour emissions have been increasing between 2004 and 2013 and submission 15 referred to a long history of odour from the plant. Submission 2 trusts that the proposed NSOOS scrubber replacement will reduce this impact.

Response

Sydney Water takes odour complaints and feedback from the community seriously. We have a number of projects underway to manage impacts from various sources of odour at the plant. However, the decreasing reliability of the NSOOS scrubber is the main contributor of odour emissions from the WWTP. The scrubber cannot reliably treat the hydrogen sulphide levels in the NSOOS, due to its age. As a result we have occasionally exceeded licence levels, usually when the equipment in question has failed.

In addition to the proposed work, Sydney Water:

replaced the central odour scrubber in 2009

installed the NST scrubber in 2001

completed all action requests from an audit of odour management procedures at North Head WWTP

installed odour loggers around North Head to monitor odour.

We have also committed to:

adding an extra cogeneration unit to take biogas from the waste gas flare, reducing odour emissions

installing dosing units in the network to reduce hydrogen sulphide levels in the NSOOS

connecting an additional waste gas flare to minimise chances of leaks and odour emissions

reviewing the impact of work when complete.

Between 2004 and 2013 odour complaints about North Head WWTP varied from 2 to 19 a year. We received the most number of complaints in 2009–10. We expect odour impacts to reduce when the projects above are complete.

Odour monitoring

Submissions 2 and 18 noted that odour monitoring devices will be installed. Submission 2 (Sydney Harbour Federation Trust) asked that the data be made available on a regular basis.

Response

Sydney Water has installed a number of long-term hydrogen sulphide monitors around North Head and in some locations in Manly. We are currently working with Sydney Harbour Federation Trust to identify suitable sites for two monitors within their land. We will discuss the data with the Trust when it is available.


Uncovered primary sedimentation tanks are a source of odour

Submission 9 asks why the screening pits (primary sedimentation tanks) are left open. Submission 17 (North Head Sanctuary Foundation) notes that the sedimentation tanks are a significant source of odour on the site, and associated issues such as rafting, or piles of sludge/sediment from cleaning are also sources of odour which were not audited (in the voluntary audit of North Head WWTP).

Response

Sydney Water does not believe the primary sedimentation tanks are likely to significantly contribute to the intermittent odour issues at North Head.

Table 5-2 of the REF (page 41) shows the odour emission rates for different odour sources at North Head WWTP. This data does not show the primary sedimentation tanks as a significant source of odour.

We have not covered the primary sedimentation tanks because:

the tanks are considered a ‘diffuse’ source of odour and because they are not turbulent, odour is not usually released in large amounts. Our independent expert technical advice and our observations also support this view

we have covered and separately ventilated the grit tanks and the effluent channel, which generate the most odour

uncovered tanks make operation and maintenance significantly easier.

This means that the primary sedimentation tanks are not covered because it would create additional operational constraints and costs, with little benefit to the odour contour of North Head WWTP.

The audit referred to in the submissions focussed mostly on procedures that we thought could contribute to the reported intermittent odour impacts beyond the boundary of the WWTP.

The auditor discussed the operations of the primary sedimentation tanks with staff at the WWTP. They confirmed that because the tanks operate continuously, there is little we can do to change the way they are managed every day. The intermittent nature of the complaints does not indicate that the primary sedimentation tanks are the source of the odour and other areas of the WWTP are more likely.

The way the other areas of the WWTP are managed, such as the biosolids plant, odour scrubbers and digesters is more likely to contribute to intermittent odour impacts beyond the boundary of the WWTP than the primary sedimentation tanks. We have placed odour loggers in various locations around North Head, which should provide more information on the source of odours.

Source of funding for projects

Submissions 3 stated that some of the works associated with the proposal (for example blocking air pathways and replacing equipment covers) should be funded as part of an ongoing maintenance program and not this proposal.

Response

The work to block air pathways and replace equipment covers is part of the proposal because:

it relates to replacing the scrubber, as it is needed to collect foul air from the screenings chamber and provide a negative pressure in the underfloor area

we can more easily access and time underground work while constructing the NSOOS scrubber

the work can potentially improve the odour contour beyond what was predicted in the REF and we can deliver efficiencies by completing it at the same time as the scrubber

the work was part of the original business case and is the delivery mechanism proposed.


5.1.6 Effect of odours from North Head WWTP

Activities and visitors at North Head being affected by odours

Submissions 6 and 15 note new businesses are opening up at North Head, including offices, galleries and workshops, childcare and schools. Some of these are likely to experience reduced odour impacts, but not all. Submissions 7 and 8 ask if Sydney Water has recognised the value of existing and future tourism at North Head. Submissions 2, 14 and 15 note the area is full of natural beauty and the WWTP must be at an efficiency level where it does not impact the local area, or the high profile tourism program. Submission 3 said the plant is located in a tourist area with thousands of visitors daily wanting to visit one of the ‘sights of the world’. The submitter suggested if the tourist ‘flow’ is reduced by significant odour emissions from the plant, there will be an effect on the state and local economy and, in that sense, what is proposed is indeed ‘state significant infrastructure’.

Response

Sydney Water is aware of the land use changes on North Head and has discussed these with the Sydney Harbour Federation Trust. We provided a submission to their management plan and respond to requests for comments regarding new activities within the Sydney Harbour Federation Trust area (former School of Artillery). While we considered new land use activities when planning our proposal, our work meets the odour guidelines from the EPA (the framework). This is further discussed in Section 5.1.4.

At this stage, Sydney Water is not aware of any impacts to the number of tourists in the area.

In regards to assessing the proposal as ‘state significant infrastructure’, there are specific requirements identified in Schedules 3 and 4 of the State Environmental Planning Policy (State and Regional Development) 2011. This project does not meet these requirements and cannot be classed as ‘state significant infrastructure’. The REF also concluded that significant impacts from the proposal were unlikely, including those on sensitive receivers. The proposal will improve odour emissions from the WWTP.

Potential health impacts of odour emissions

Submission 17 (North Head Sanctuary Foundation) noted at times odours are noxious causing eyes to water and respiratory problems. This submitter also expressed concern about odours impacting residents and other sensitive receivers (respite carers, hospital patients and staff) being exposed to substantial odour, from which they are unable to escape. Concern was also expressed for the WWTP staff and asked if an OH&S audit has been done to ensure workers are safe. Submission 19 stated that wastewater gases are a known health hazard that is not being addressed, and noted the extent of predicted odour emissions which would affect Manly Hospital and several schools close to the WWTP.

Response

Hydrogen sulphide is a component of odour associated with wastewater treatment. It has a characteristic ‘rotten egg’ smell, which can be detected by our sense of smell at very low levels – well below those known to cause health effects. Smelling hydrogen sulphide does not mean that it will harm your health. The risk of harm from hydrogen sulphide mainly comes from being exposed to high levels in a confined space.

Emissions of hydrogen sulphide from North Head WWTP are regulated by:

Work Health and Safety Act and Regulations 2011

Protection of the Environment Operations (Clean Air) Regulation 2010

The Workplace Exposure Standards for Airborne Contaminants (Safe Work Australia, 2011) identifies short and long-term exposure limits for workers in contact with hydrogen sulphide. The emissions from the WWTP are significantly lower than these limits.

The Protection of the Environment Operations (Clean Air) Regulations also limits the amount of hydrogen sulphide that can be emitted from the WWTP. For a point source, such as a scrubber,


the limit is 5 mg/m3 of air (~3.6 ppm). Our Environment Protection Licence requires us to monitor hydrogen sulphide emissions. If we exceed our limits, we report this to the EPA.

While we acknowledge that odour may be noticeable at times, community health is not at risk. Sydney Water complies with both the Safe Work and Clean Air requirements, and we are committed to safety. The proposal to replace the NSOOS scrubber and improve underground ventilation will help protect the environment, the health and safety of our staff and the community.

5.2 Alternatives considered

5.2.1 Selection process

Criteria used to evaluate alternative options

Submission 3 asked for more detail on alternative options and the criteria for assessing those options, including what the criteria were, and whether the decision drivers were relevant to cost, community, worker safety and/or the environment. Submission 15 from Manly Council and Manly Council Community Environment Committee also requested information on the options considered and how we evaluated the social and environmental costs of the proposal. Submission 4 referred to a document entitled ‘Project North Head Upgrade Preferred Option Statement on Air Treatment and Biofilters’, which suggested biofilters would be inadequate for odour treatment, due to required air flows and large land requirements.

Response

The background to this project included the review conducted after PARR, which identified the NSOOS scrubber for future work. About this time, we completed condition assessments of the NSOOS pipe network, which identified high levels of corrosion. We also reviewed odours and modelled all odour sources within the WWTP. This confirmed the NSOOS scrubber as a key source of odour. With this information, we began investigating and planning to replace the NSOOS scrubber and improve underfloor ventilation. Air flow and ventilation considerations are discussed in the next response.

A variety of technology options were considered to replace the NSOOS scrubber, including:

biotrickling filtration (BTF)

wet chemical scrubbing

biotrickling filtration with activated carbon polishing

wet chemical scrubbing with activated carbon polishing

biotrickling filtration with polishing by wet chemical scrubbing.

A BTF is different from a biofilter, which is filtration through a large compost or wood-chip bed. We did not consider installing a biofilter, mainly due to the extremely large footprint that would be required to treat the high air flows. Similarly, using enhanced dispersion alone (a very tall stack) was not considered feasible because of potential visual impacts the structure height might have on North Head amenity values.

We identified design criteria to narrow down the options, including that the technology:

should be proven

be able to treat a maximum odorous air flow identified

be able to treat both average and peak hydrogen sulphide concentrations

be able to reliably and effectively reduce odours to a concentration of 1,000 odour units or less

be capable of managing fluctuations in inlet odour concentration

provide a minimum of 20 years’ service life (except for consumable components).

The two suitable options for the NSOOS scrubber assessed were BTF and wet chemical scrubber technology:


Wet chemical scrubbers have been one of the most common technologies for removing odours from WWTPs. There are three currently operating at North Head WWTP. They represent a proven technology for treatment of hydrogen sulphide based odours.

BTFs were initially developed to overcome some design and operational limitations associated with other more conventional odour control technologies. They have been shown to increase operational stability and reduce costs. The technology transforms a mixture of pollutants from the air into water, carbon dioxide and salts. Micro-organisms, primarily bacteria, are the catalyst for this process. Multi-stage BTFs are relatively new in Australia, but are well proven overseas. They are able to treat foul air containing a large spectrum of compounds, including volatile organic compounds, as well as hydrogen sulphide.

We did not further consider the ‘second stage’ process with additional activated carbon polishing because the modelling indicated that this would have little benefit on the odour contour, but have significant extra costs and operational constraints.

Sydney Water uses many criteria to assess projects. During the first stage of assessment, we considered:

long-term technical considerations, such as operational features, maintenance requirements, operational flexibility and upgradability

short-term technical considerations, focused on construction requirements, such as timeframes, access, practicability, demolition and excavation requirements

environmental considerations, including the use of chemicals, emissions and impacts on flora and fauna

social considerations, such as noise, visual amenity and community acceptance. Community acceptance related mainly to stack heights and traffic. We believed that the proposal, if odours could be reduced, would be welcomed. Section 4.3 has more information on community involvement.

We then considered cost, including lowest total cost and predictable operation costs.

Sydney Water chose a BTF scrubber in preference to chemical treatment for this proposal, as it is equally effective in terms of odour removal, but has inherent advantages that confirm its preferred status. These advantages include:

high levels of odour reduction

chemical free operation

no additional truck movements

no additional storage of hazardous chemicals.

We also found that the BTF scrubber requires less operator intervention to maintain reliable performance. While the BTF has higher capital costs, it has a lower operating cost compared to a chemical scrubber, offering long-term value for money.

How will increasing air flow affect odour and corrosion?

Some submissions (7, 8, and 15) noted air flow to the scrubber would increase. Submission 15 questioned if an increase of 7 m3/s (from 8 m3/s) would be sufficient to reduce corrosion and asked how we determined this. Submission 15 also asked why the large flow rate of 20 m3/s is required from the underfloor area of the grit chamber. Submission 3 queried whether the proposed flow rate is sufficient to reduce corrosion.

Response

Condition assessments show that concrete pipes in the North Head wastewater network are deteriorating at a greater rate than designed. When moisture is present, bacteria convert hydrogen sulphide into sulphuric acid. This can accelerate pipe corrosion, and network odour problems. Increasing air flow through the NSOOS reduces the amount of hydrogen sulphide. This minimises the amount of sulphuric acid produced, reducing corrosion of the concrete pipes.


Sydney Water studies indicate that the current flow rate from the NSOOS is about 8 m3/s. The increase in the scrubber air flow to 35 m3/s (from about 29 m3/s) is made up of:

20 m3/s from the underfloor area to improve the odour containment

15 m3/s from the NSOOS to reduce risk of escaping odours and corrosion.

We based these volumes on the ventilation and hydrogen sulphide modelling we did to inform project planning.

The aim is to reduce hydrogen sulphide generation within the pipe network to less than five parts per million (ppm). This will be achieved by increasing the air flow in the NSOOS (to 15 m3/s) and by installing dosing units in the networks. The dosing units treat wastewater with a compound commercially known as OdourLock. OdourLock reduces the generation of hydrogen sulphide gas in the wastewater system and may also reduce odour concentrations at the plant.

Selection of scrubber and 1000 vs 500 odour unit concentration

Submissions 3, 12, 15, and 19 queried why a residual odour concentration of 1,000 odour units was selected, drawing comparison to the 500 odour unit concentration at Malabar WWTP. Submission 3 submission asked if the choice of scrubber impacts odour concentration and states that there was no justification in the choice selected.

Response

Section 4.1.2 addresses performance at 1,000 odour units rather than 500 odour units.

In regards to the choice of scrubber, both chemical and BTF technology were identified as suitable to meet the 1,000 odour unit performance guarantee required. During the options selection, a BTF scrubber was chosen for North Head WWTP as it is easy to operate and maintain, avoids the use of chemicals and has lower whole of life operating costs.

5.2.2 Design considerations

New scrubber should be best practice

Submission 11 states that the proposal should target best practice and the scope should be revised accordingly, and include a long-term strategy for the WWTP. Submissions 15 and 20 suggest the proposal does not meet requirements for current odour treatment technology. Submission 17 states that the scrubber replacement is a maintenance issue and that new technology could improve operations of the plant and odour issues.

Response

The project will aim to meet best practice and the performance objectives of 1000 odour units. Both chemical and BTF scrubbers could achieve these performance requirements. The BTF scrubber proposed for North Head incorporates cutting edge refinement with a number of improvements over conventional systems. In this respect, it is among world’s best practice. The BTF scrubber is also being designed and commissioned by one of the leading international exponents of the technology.

The BTF technology will deliver efficiencies through a lower operating cost over the life of the project compared to chemical scrubbers. Also, this technology does not require chemicals for treatment, reducing the number of chemical deliveries to the WWTP, making it more sustainable. The technology is proven to achieve the target odour limits.

Use of chemicals and lime

Submission 16 stated that chemical treatment is expensive and that the proposal assumed it would be cost effective for reducing odours in the future. The submission also asked why this system would be considered more effective than the historical practice of addition of lime to the sludge.

Response

The submission may have misinterpreted some information in the REF. The BTF scrubber uses a nutrient mixture (containing nitrogen, phosphorus, potassium and thiosulphate) and small amounts of sodium hydroxide to control the pH of the water. It does not require chemicals for operation, and


so will reduce the amount of chemicals currently used at North Head WWTP. It should be noted that chemical scrubbers are currently, and will continue to be, used to control odour at North Head WWTP (Central Scrubber and NST scrubber). Both technologies are proven for odour control.

‘Liming’ is the process of adding liquid lime or calcium hydroxide to wastewater sludge to control pathogen growth and convert sludge into a useable product for agriculture or recycling. It has been widely used in the industry for many years, but is no longer used at North Head WWTP as more suitable processes have been developed. It is not relevant to this proposal which relates to the replacement of a scrubber for odour control.

Why is NSOOS scrubber at end of useful life and will BTF scrubber deteriorate as quickly

Submission 15 from Manly Council and Manly Council Community Environment Committee asked how we determined that the NSOOS scrubber is approaching the end of its useful life and whether odour concentration from the BTF scrubber will increase as quickly and significantly as the NSOOS chemical scrubber did. Submission 3 notes the scrubber is well past its ‘use-by’ date.

Response

The existing NSOOS chemical scrubber was installed in 1992 and significantly reconfigured in 1997. This reconfiguration fundamentally altered the system’s operation. A condition assessment of the NSOOS ventilation system noted that modifications on the scrubbers over the years had affected condition and performance (PB/MWH, 2007). The assessment also found that a lack of sufficient ventilation in the NSOOS was causing excessive corrosion and sub-optimal odour containment. As a result, the NSOOS was corroding at a faster rate than expected, and the scrubber was not extracting sufficient air flows to avoid high levels of hydrogen sulphide generation.

The proposal, which includes replacing the scrubber and improvements to the underground ventilation system, has been sized to extract and treat required air flows. The BTF is also a relatively uncomplicated system requiring no chemicals. The proposed BTF scrubber has a 20-year design life and is expected to perform reliably for that duration.

5.3 Community and stakeholder engagement

5.3.1 Consultation process for the proposal

Lack of consultation during proposal development

Many (3, 4, 7, 8) submissions suggested that community consultation and involvement in the proposal development process was insufficient. It was suggested that by developing the Community and Stakeholder Engagement Plan ahead of the REF, the community were unable to provide input into the values and assumptions of the REF, current and projected odour levels from the WWTP (including boundary considerations) and the choice of technology for the new scrubber, including operational capacity and resultant output. Submission 3 questions how ‘community acceptance’ was tested.

Response

Sydney Water is aware that odour is an issue for members of the community. Understanding community values is important, particularly when planning major upgrades. The aim of this work, however, is to ensure the reliability of an existing asset. The scrubber is near the end of its useful life and must be replaced to ensure the WWTP’s reliability.

Replacing the NSOOS scrubber is the latest in an ongoing program of upgrade work at North Head WWTP. Previous work included replacing the central odour scrubber. This helped reduce the impact of odour on the local community, and reduce the 2 odour unit contour.

We considered a number of options from a cost, safety, environmental and community perspective. Section 5.2.1 describes this and includes the projected odour levels and the choice of technology.

In developing the Community and Stakeholder Engagement Plan we considered both the scope of the project and its urgency. As a result, we provided an opportunity for key stakeholders and the


community to comment on the environmental assessment rather than the scope of the project. We also consulted with stakeholders and the community in the following ways before displaying the REF:

wrote to key stakeholders, inviting them to provide comments or concerns, statutory or otherwise, for consideration in the REF

discussed this work with the North Head WWTP Community Consultative Group

briefed the Manly Community Environment Committee and North Head Sanctuary Foundation.

We received three responses to our letters. They raised concerns about the impact of odour on nearby sensitive receivers, options considered as part of the proposal, budget and the objectives of the Alliance, as well as requesting briefings before the REF exhibition.

Replacing the NSOOS scrubber is not the only work to manage odour at North Head WWTP. Section 5.1.3 describes the other work to address odour.

Sydney Water will continue to monitor odour and odour complaints after the work is done.

REF had unexpected attitude of ‘community should accept proposal’

Submission 3 stated that the REF is written with an attitude of ‘This is what we will do, the impact on the community is whatever it will be and we believe that the community should accept it, as there will be a slight reduction in the odour impact. The submissions suggest that we expect community acceptance.

Response

We prepared the REF according to the Environmental Planning and Assessment Act (EP&A Act). To assess potential environmental impacts, a clear scope is required. We also took a conservative approach to the assessment, to be confident when predicting improvements.

Benefits of this project will be a slight improvement in the odour contour and elimination of intermittent odour issues from the scrubber (due to its poor reliability) on the surrounding community. We are taking a staged approach to improving odour. This includes a review at the end of this project to assess how odour has improved, its impact on the neighbouring community and next steps.

Communicating with local community and addressing concerns

Submission 11 notes the level of community concern and suggests more work is needed for this project, including educating and working with the local community

Response

Sydney Water notes the level of community concern about odour from North Head WWTP. While we have a range of communication activities, we seriously consider all community comments and review our activities where required.

Current consultation activities include North Head WWTP’s Community Consultative Group, which meets regularly to discuss the operations and plans for the plant. The group represents many of the community groups near the plant, Manly Council and the local MP’s office. We also meet with the North Head Stakeholders group which includes NPWS, Sydney Harbour Federation Trust and Manly Council. We send out newsletters, update the website and Sydney Water Talk. We also meet with stakeholder groups on request, for example North Head Sanctuary Foundation. We will continue to provide updates for the proposal.

Request for regular project updates to stakeholders

Submission 1 requests Sydney Water provide regular updates on the progress of the project to NPWS and other North Head landowners through the North Head Stakeholders Group meetings.

Response

Sydney Water will provide regular project updates to the local community and North Head Stakeholders’ Group. Sydney Water is a member of the North Head Stakeholders Group and plans to attend meetings to update the group.


Sydney Water will inform and engage the community throughout the project to ensure construction impacts are minimised.

NPWS to be notified if bushfire risk profile changes

Submission 1, NPWS: Please advise us in writing if the proposed replacement of the NSOOS scrubber and associated works will change the bushfire risk profile for the site and/or North Head generally. If the proposed operation of the new scrubber system does increase bushfire risk or consequences, the Review of Environmental Factors should cover this and future operational plans for the site.

Response

We are not expecting this project to change the bushfire risk profile at the North Head WWTP or within North Head more broadly. We will consult NP&WS if we think the bushfire risk will increase.

5.3.2 Sydney Water complaints process

Complaint numbers lower than actual impacts

A number of submissions (3, 5, 9) suggested that some residents, tourists and other users of North Head do not know how to make a complaint, meaning complaint numbers are low and understated compared to actual impacts. It was suggested that signs be posted around North Head with complaint contact details. Submission 18 notes that they will advise members of contact details to call for odour or noise from the plant, to provide a broader form of information.

Response

Sydney Water has a number of ways it lets the community know about the plant and how to contact us if there is a complaint or enquiry. We are placing signs around the plant which will include contact details for complaints or enquiries. We often write to the community with updates about the plant and this includes how they can contact us, including a phone number for North Head WWTP, so that we can investigate issues quickly. In addition, Sydney Water’s general contact details are on all Sydney Water mail outs including bills, advertising, local signs and on our website.

All complaints should be properly addressed

Submission 18 notes that Sydney Water should treat all calls advising of odours/noise concerns appropriately, regardless of the frequency of calls. Submission 3 says complaints from Manly residents have been ignored.

Response

Sydney Water’s Customer complaints policy specifies how we manage complaints. It’s on our website (sydneywater.com.au). We record, track and report the outcome of all complaints to the complainant, as required by this policy.

Sydney Water will continue to monitor odour and odour complaints after the work is done.

Community notification of odour levels

Submission 9 notes that monitoring has identified a number of times when hydrogen sulphide emissions (odour generating substance) have exceeded licence conditions and that complaints over the last few years have increased. The submission notes the EPA are notified of this and asks if the public should also be notified.

Response

Sydney Water monitors hydrogen sulphide emissions for North Head as required by our Environmental Protection Licence with the NSW EPA. We publish these results monthly on the Sydney Water website at www.sydneywater.com.au/SW/water-the-environment/how-we-manage-sydney-s-water/waterquality/epa-reports/air-quality/index.html. The data indicates compliance within the limits identified in the Protection of the Environment Operations Act 1997. Sydney Water reports non-compliances to the EPA. Times where we exceed limits are usually short-term and infrequent. Section 5.1.6 refers to potential health impacts.


Sydney Water also reports annually to the EPA on all non-compliances. All annual returns and incidents can be viewed publicly online at www.epa.nsw.gov.au.

5.3.3 Decision report queries

Submissions should be provided in full in the Decision report

Submission 3 stated that each submission should appear in full and that if the submitter wishes to remain anonymous, then names should be blanked out. Submission 9 requests consideration of the issues raised in the submissions.

Response

This Decision report aims to address all concerns and questions in the various submissions. We will send this report to all stakeholders who made a submission and post it on sydneywatertalk.com.au.

As discussed in Section 5, we have grouped issues from each submission and summarised them to provide responses. Each submission is provided in full in Appendix 2, but we have omitted names and addresses of individuals for privacy reasons.

Dissatisfaction at information session and lack of time/ email details in REF

Submission 3 expressed dissatisfaction that the time of the information session was not in the REF and details for lodging submissions did not include an email address.

Response

We promoted the details of the information session, including the time, through an advertisement in the Manly Daily on 26 October 2013, through direct mail to key stakeholders, on Sydney Water Talk and in the newsletter that was sent to 1,725 properties. The omission of the time for the information session in the REF was an oversight. We included an email address ([email protected]) in section 1.4 ‘Making a Submission’, on page 12 of the REF, in the advertisement, letters and on sydneywatertalk.com.au

Approval authority and value of the Decision report

Submission 3 queries the approval authority (Alliance or Sydney Water) and the ability to decide if a Decision report is needed. The submission also suggests that the Decision report will only focus on issues of consequence, not all issues. The submission asserts that Sydney Water does not view the community as a ‘worthwhile contributor’ to its activities, and should be used to improve the proposal, as well as assess it.

Response

The Alliance has prepared the REF and Decision report in consultation with Sydney Water. Sydney Water is the determining authority for the proposed project under Part 5 of the EP&A Act. We prepared this Decision report to address matters raised in submissions and assess changes to the proposal, since preparing the REF. If we had received no submissions or not made changes, we would not have required a Decision report, and so this was explained in the REF. We aim to address all issues raised in the submissions.

Sydney Water values the submissions provided during the REF process. We have used information from the submissions, where appropriate, to refine the proposal. For example, section 5.4.2 describes further mitigation and management measures that we have added for construction.

5.4 Environmental management

5.4.1 Environmental performance and management of North Head WWTP

General environmental performance and future plans for North Head WWTP

A number of submissions were made regarding the general environmental performance of the North Head WWTP. Some stated that Sydney Water should:

take a ‘holistic’ approach to upgrading the WWTP to best practice (Submissions 7, 8, 12, 13)


close the plant (Submission 16)

treat wastewater at its source, and to a tertiary standard (Submission 20)

commit to a plan and budget in the next five years to upgrade the plant to meet best practice international standards (Submissions 12,13).

Other submissions are concerned that:

Sydney’s growth will mean the WWTP will continue to receive increased quantities of wastewater (Submissions 7, 8, 16)

the proposal does not address the many environmental concerns Manly residents have about performance, suggesting the WWTP is having a detrimental effect on the health and wellbeing of people, the marine and terrestrial environment (Submission 19)

there have been a number of promises made to improve the plant that did not eventuate, including upgrading North Head WWTP from primary to secondary treatment (Project North Head), planning for eventual reduction and closure of the plant, and replacing sludge trucks with a pipeline to a rail head. This submission is also concerned that reliance on North Head WWTP should be reduced to avoid environmental impacts associated with the WWTP (Submission 9)

the trucks and other vehicles travel through the town centre and residential streets, leaving an ‘ugly impression’ on tourists (Submission 9)

the gravity feed system is at capacity, but this issue is not being addressed (Submission 16).

Submissions 9, 11, 12, 13, 14 asked about Sydney Water’s and the NSW State Government’s long-term strategy and plans for both the North Head WWTP and waste treatment in general. Submission 18 expressed concern that there is no commitment to reviewing current and future operational performances of the North Head WWTP with community consultation as part of the process.

Response

The scope of work in the REF is to replace an odour scrubber and improve the underground ventilation. Replacing the scrubber is essential, because it is near the end of its useful life. Many of the community’s concerns are not within the scope of this project. However, Sydney Water does consider these concerns when making plans for North Head WWTP.

Currently, the North Head WWTP meets the EPA’s requirements in our Environmental Protection Licence. Monitoring required by this licence shows we are meeting our licence conditions and performance criteria. Consequently, we have no plans to upgrade the WWTP to secondary treatment or close the WWTP.

Sydney Water had previously planned a project known as Project North Head. This proposed to upgrade the plant to full primary treatment. Feedback from the EPA and the Independent Pricing and Regulatory Tribunal (IPART) indicated there were not sufficient drivers for this project. That is, there was no environmental or regulatory need and so the project was not funded.

The focus of recent projects has been to ensure the reliability of the plant. This included projects costing $150 million, known as PARR (Process and Reliability/Renewals project).

PARR was completed in 2009 and ensures a reliable wastewater treatment service for northern Sydney within the context of urban growth, meeting Environmental Protection Licence requirements and maintaining reliable assets. Improvements included:

protecting water quality at local beaches

reducing odour emissions at the WWTP by upgrading the central odour scrubber

significantly reducing biosolid truck movements through Manly

using 1.5 million litres of recycled water at the plant each day

reducing carbon emissions by generating and using renewable energy

improving worker safety


improving WWTP reliability and performance.

During the planning and assessment for the PARR, Sydney Water used population growth predictions from the Department of Planning’s Metropolitan Strategy. We allowed for the increased population and associated flows in the scope of work. This work helped reduce the number of trucks travelling to and from North Head WWTP.

Sydney Water is actively managing North Head WWTP to protect public health and the environment. This proposal helps Sydney Water meet these objectives, by improving odour emissions while having no additional impacts on the environment. Future projects at North Head WWTP will be subject to relevant environmental assessments and community consultation.

Community health concerns related to operation of North Head WWTP

Submission 15 (Manly Council and Community Environment Committee) state they have been unimpressed by Sydney Water’s lack of concern for community and environmental health as a result of emissions from the WWTP. Submission 18 (Fairy Bower Precinct) said that there is great community concern (and has been for over 20 years) regarding odours, noise, gas, dust, sludge as well as chemicals used to mask odours from the plant, and the potential these have to compromise the health of those exposed. The submission noted that many people felt that health had already been compromised.

Response

Sydney Water takes odour complaints and feedback from the community seriously. We are committed to the health and safety of our staff, contractors and neighbouring communities.

We ask that customers report all odour and other environmental complaints to Sydney Water on 132 090, which is available 24 hours a day, 7 days a week or directly to the WWTP’s operations desk on 9934 4423, also available 24/7. We will investigate all complaints.

The environmental protection licence, issued by the EPA, requires us to manage and monitor emissions from North Head WWTP. We actively manage on-site odours, noise and dust to meet the licence and other regulatory requirements. The limits in the licence are designed to protect public health and the environment.

5.4.2 Construction environmental management

Opportunity to provide input into Construction Environmental Management Plan

Submission 1 noted the preparation of a Construction Environmental Management Plan and requested an opportunity to provide input.

Response

The Alliance will prepare a Construction Environmental Management Plan (CEMP) for the project, following the Guideline for the Preparation of Environmental Management Plans (DIPNR, 2004). The CEMP will cover the construction and commissioning phases of the proposed work, as well as decommissioning activities. The CEMP will include the mitigation measures outlined in the REF and the additional mitigation measures identified in this Decision report.

As requested, the Alliance will consult with the National Parks and Wildlife Service, during development of the CEMP and before construction commences.

Potential for unpleasant odours during construction

Submission 6 expressed concern over the potential for unpleasant odours during construction.

Response

During commissioning, the existing chemical scrubber will operate in combination with the new BTF scrubber. Airflow to the BTF scrubber gradually increase over six weeks or more to ensure all emissions are properly treated by the new BTF. Once this is confirmed, we will decommission the NSOOS chemical scrubber.


We will manage changeover and commissioning activities to minimise odours and impacts on the local community. We will notify the community in advance of any potential impacts and unavoidable disruptions.

Maintenance and use of Blue Fish Drive

Submissions 1 and 2 identify suggestions relating to the use of Blue Fish Drive, including to vehicles, access, damage and maintenance, and to avoid potential impacts to the local bandicoot population.

Response

We have developed additional mitigation measures, based on the matters raised in the submissions by NPWS and Sydney Harbour Foreshore Trust. These will be incorporated into the CEMP and are outlined in Appendix 3.

All construction workers will be required to complete a site induction, including information on construction environmental management. Staff will be informed of the measures in the CEMP, such as the 40 km speed limit when travelling along Blue Fish Road, and awareness of bandicoot presence and foraging times. We will also use toolbox talks and training sessions during construction and commissioning to reinforce the importance of these matters.

5.4.3 Flora and fauna

Minimise clearing of native vegetation

Submission 1 requested mitigation measures to minimise damage to native vegetation, specifically, protecting hollow-bearing trees. The submission also requested that we plant soft native grasses or lawn during rehabilitation to help enhance bandicoot habitat. Submission 6 voiced concerns for risks to threatened flora (Eucalyptus camfieldii), and requested that we identify Brown Stringybarks before removal. Submission 6 also recommended that we revegetate the area using North Head seed or cuttings.

Response

We have developed additional mitigation measures relating to hollow bearing trees and rehabilitation, as outlined in Appendix 3. These will be included in the CEMP.

An ecological assessment of the proposed site did not find any Eucalyptus camfieldii in the project area.

We will minimise the clearing of vegetation, where possible. However, we must remove up to 0.39 ha of coastal open-scrub and regrowth scrub for the project. The vegetation to be removed is dominated by common species, including Coastal Banksia, Coastal Tea-tree, and Wattles.

All the species that we propose to remove are common in the region, and none are listed as rare or threatened. Similarly, areas designated for clearing are unlikely to provide habitat for any threatened fauna or flora species, and the areas to be cleared represent an insignificant portion of the broader landscape of North Head. Vegetation for the rehabilitation phase of the project will consist of locally-occurring native flora species, typical of the original habitat. We will attempt to source these from North Head seeds and cuttings.

5.4.4 Waste management

Additional leachate to ocean as a result of the proposal

Six submissions (3, 4, 9, 15, 16, 19) referred to the leachate from the proposed BTF scrubber. The submissions queried how this leachate will be treated before discharge and whether we had assessed the impact of leachate from an environmental perspective. Some submissions identified that 129 kL/day represents an additional load of about 47 Olympic-sized swimming pools a year and asked if the EPA had been made aware of this amount.

Response

The bacteria in a BTF use clean water for the biological processes. This means that the leachate from a BTF is essentially clean water with very dilute sulphuric acid (pH of 2), which is similar to


what would normally be present in wastewater as sulphate. The REF estimated that the proposal would produce 129 kL a day of leachate. This is about an extra 80 kL/day, compared to the existing (smaller) scrubber.

Wastewater flow through the North Head WWTP is 330 ML/day on average during dry weather. The 129 kL of leachate represents about 0.04% of the daily dry weather flow, or a dilution factor of about 1:2500. The BTF leachate will be returned to the inlet of the North Head WWTP.

We do not anticipate that the addition of the leachate will change the composition of the treated effluent discharged to the deep water ocean outfall. We will continue to monitor and report on water quality and ocean discharge as required by our Environmental Protection Licence. We do not expect any changes to compliance. The EPA was sent a copy of the REF and did not comment on this matter.

Environmental impacts of deep ocean outfalls

Submission 16 asked for more detail on the increase of sulphuric acid from the new scrubbers, including the process and environmental assessments. The submission states that no studies have been completed to assess environmental impacts flowing into the ocean since the original installation of the deep water ocean outfalls.

Response

The additional leachate is addressed above.

In regards to environmental monitoring, Sydney Water began regular monitoring of the deep water ocean outfall at North Head, before it was commissioned in the early 1990s.

We have an ongoing monitoring program to assess how the deep water ocean outfalls perform over the long-term. We collect data at 20 ocean monitoring sites between Terrigal on the NSW Central Coast and Shoalhaven Bight, south of Sydney. These sites detect any potential impacts on the marine ecology and sediments. The monitoring program studies four main areas:

Marine ecology.

Effluent toxicity.

Marine sediment characteristics.

Oceanography.

The monitoring program forms part of the North Head system Environmental Protection Licence. The program is conducted on a three-year cycle. The first year is an assessment year, while the second and third years are for surveillance. Results from the most recent assessment year, 2011, indicated that the deep water ocean outfalls had no measureable impact on ecosystem health (Sydney Water, 2012). Monitoring program results are available on our website.

We also calibrate and validate numerical models of the deep water ocean outfalls. These models are run on an hourly basis to estimate the movement and dilution of the plumes from each of the deep water ocean outfalls. This allows us to estimate likely impacts of discharges. We provide model output and associated input data to EPA and the Office of Environment and Heritage on a yearly basis.

5.4.5 Heritage

Heritage values of North Head

Submission 15 (Manly Council and Manly Community Environment Committee) noted that the WWTP is situated within Sydney Harbour National Park and adjoining the North Head Sanctuary. An extract of the Australian Heritage Database Statement of Significance was provided:

‘North Head is an area of great cultural richness, diversity and natural interest.’ It has been described together with Dobroyd Head as ‘the most precious parts of Sydney Harbour National Park’, which ‘contains the most extensive heath scrub vegetation around Sydney Harbour, much of it in almost undisturbed condition.’


Submissions 2 and 16 refer to the heritage values of North Head and submission 16 also notes that on 12 May 2006 the entire North Head was added to the National Heritage List to provide another layer of protection for the area.

The submissions state this should be a reason for Sydney Water to guarantee to keep odour levels to a minimum, and have the 2 odour unit contour apply over the entire area of North Head outside the boundary of the WWTP.

Response

North Head WWTP (Lot 1, DP 604428) is excluded from the area that is of National Heritage significance. However, the heritage assessment for the REF included potential impacts on North Head heritage values. The assessment found that, as all works will be within the WWTP, no significant impact is likely on the North Head heritage listing, or any of the other heritage items near the WWTP.

Section 5.1.4 addresses odour beyond the boundary. Sydney Water aims to minimise our odour impacts and recognises the values of North Head, including heritage values.

Reference to North Head vs Sydney Harbour National Park

Submission 3 stated that ‘North Head’ in the legend on Figure 5-7 should be ‘Sydney Harbour National Park’.

Response

Figure 5-7 from the REF shows listed heritage items. ‘North Head’ is included in the Australian Heritage Database as an item of National Heritage significance. This description was included in Table 5-7 of the REF. The submitter is correct that the area also corresponds to Sydney Harbour National Park.

5.4.6 Traffic and chemical use

Traffic movements relating to chemical use and management

Submission 16 asked for further information on local truck movements, chemical deliveries to and from the site and about chemical storage and management.

Response

Traffic

Section 5.8.1 of the REF identified existing traffic volumes generated by the WWTP as being about:

16 heavy vehicles movements a day for activities such as chemical delivery and transporting biosolids, grit and screenings off-site

60 light vehicle movements a day, mainly staff entering and leaving the site for work.

During construction of the proposal, Section 5.8.2 of the REF estimates additional construction traffic volumes as:

up to about 20 heavy vehicle movements a day

about 20 to 36 light vehicle movements a day

up to 72 BTF delivery truck movements (36 for BTFs, 36 for ducts and elbows).

The assessment found that while there may be some minor traffic impacts, the local community is not expected to experience a significant change in traffic conditions or safety, and we propose safeguards to minimise potential impacts.

After construction, the number of truck movements should not differ from the existing traffic volumes. We expect there will be one less chemical delivery truck a month, but a BTF servicing vehicle may be required. This servicing vehicle is likely to be smaller than the chemical delivery trucks.


Chemicals

During construction, some chemicals will be stored and used on-site. Section 5.10.2 of the REF identifies mitigation measures. We will develop a Construction Health and Safety Plan for the project, which will include safe work measures for the construction period, such as bunding and spill management.

During operation, a small quantity of nutrient mixture (mainly consisting of nitrogen, phosphorous, potassium and thiosulphate), and a limited volume of fuel, concrete protection paint, and grout will be stored and used. We will use standard WWTP management measures for these.

Overall, the proposal will reduce chemical use at the WWTP.

5.5 Scope of assessment, technical clarifications and corrections

5.5.1 Scope of assessment in the REF

REF only considered construction impacts

Submission 3 stated that the REF only considered environmental and community impacts of the construction period.

Response

The REF assessment included the potential environmental and community impacts for both construction and operation of the proposal.

The assessment identified a number of potential environmental impacts during construction and included safeguards to mitigate or manage these.

For operation, the assessment concluded that impacts were unlikely or easily managed through design. Table 5 provides a summary of the REF impact assessment for operation.

Table 5 Summary of potential impacts during operation of the proposal

Aspect Potential impact during operation

Safeguards

Topography, geology and soils No impacts likely No specific safeguards required

Water and drainage No impacts likely No specific safeguards required

Flora and fauna No impacts likely No specific safeguards required

Air quality Air quality (odour) would improve during operation

No specific safeguards required

Noise and vibration Aspects of the proposal would be noisy but provisions, such as encasing fans in a building, would be sufficient to manage this

Apart from design measures, we included a safeguard to monitor noise after commissioning to confirm the proposal meets the Industrial Noise Policy

Waste management Increased amount of leachate. This can be managed through existing WWTP system

No additional safeguards needed beyond normal WWTP processes and management measures, such as bunding

Heritage – Aboriginal and non-Aboriginal

No impacts likely No specific safeguards required


Aspect Potential impact during operation

Safeguards

Traffic and access No net change – one less chemical delivery truck a month, but a BTF servicing vehicle may be required

No specific safeguards required

Visual No impacts likely beyond WWTP boundary

Safeguards identified on page 62 of REF including retaining existing vegetation and painting BTF towers and tank in a low-reflective matt grey-green coating

Energy and chemical use Energy and greenhouse gas emissions would increase, chemical use would decrease

Additional energy requirements to be offset by second cogeneration engine

Cumulative impacts No impacts likely No specific safeguards required

The assessment meets the requirements of Part 5 of the EP&A Act.

REF assessment not as rigorous as Malabar and Cronulla REFs

Submission 3 and 15 queried the rigour and scope of the assessment in the REF, compared to the Malabar and Cronulla projects, and referred to the number of pages in each REF.

Response

The method for assessing the North Head NSOOS Scrubber Replacement REF was as rigorous as those done for Malabar and Cronulla odour projects. We designed the scope of the assessments to meet the regulatory requirements for each aspect, such as assessing the significance for the Long-nosed Bandicoot in the flora and fauna assessment.

For the North Head REF, we completed four specialist studies – visual amenity, ecological, noise and odour. We did not include these in the appendixes to the REF, as we did for the Malabar and Cronulla REFs. Without appendixes, the actual REF assessments are comparable – North Head 73 pages, Cronulla 75 pages and Malabar 79 pages. We did not append the specialist studies for North Head, based on feedback from communities that the information was too detailed and not often read. The idea for North Head was to provide a succinct document for public exhibition, and relevant information from the specialist studies was extracted and included in the main REF document. Had we included these studies, the North Head REF would have been significantly longer than both the Cronulla and Malabar REFs.

REF should consider downstream impacts of proposal

Submission 16 references the Nathan Dam case and says this shows precedence that downstream adverse impact on the environment must be considered.

Response

The reference to the Nathan Dam case is reference to a proposal assessed under the Commonwealth Environment Protection and Biodiversity Conservation Act, 1999 (EPBC Act)) and subsequent legal action relating to its approval. The reference is not applicable to this proposal as this proposal is being assessed under the EP&A Act, and the EPBC Act does not apply.

However, the assessment in the REF found that the proposal would not affect the ability of the WWTP to meet the conditions of the existing Environmental Protection Licence. As such, downstream impacts as a result of the proposal are unlikely.


5.5.2 Technical clarifications

Accuracy of odour modelling and contours

Submission 3 noted the REF calculations depend on input data. The submission questioned the validity of the results and asked a series of technical queries and comments about odour modelling and the contours presented, including:

the data used in the assessment has not been justified, affecting the contours

information about the weather data used was queried – which site, what period, was it typical or worst case, grid size and convergence study, and whether emissions were taken as constants in time

a sensitivity study should have been performed to show variability and reliability of the information, as well as what probable errors should have been included to provide indication of spread of values of the samples used

by not rounding figures an accuracy has been implied that is not achievable in practice

errors should have been included on the contour diagrams

Response

Odour calculations and modelling were completed following the EPA’s approved assessment methodology, Approved Methods for the Modelling and Assessment of Air Pollutants (August 2005). This document identifies which methods must be used to model and assess emissions from stationary sources in NSW. It includes meteorological requirements.

We used meteorological data from the 2012 calendar year as this was demonstrated to be a representative meteorological year.

There is precision in the model results, but the intention was not to imply that model results are accurate. The dispersion model results were used as a guide on the likely changes to off-site odour levels as a result of the proposal, compared to the current situation. Modelling in general contains a degree of variability.

The assessments use the best available data at the time of the assessment.

Incorrect flow rate and units used in REF

Submission 3 states the volumetric flow rates on page 27 of the REF are out by a factor of 3,600. The submitter also noted the unit used in the REF to express odour concentration is ‘ou’ while the odour emission rate in Table 5-2 of the REF is ou.m3/s.

Response

The REF incorrectly stated volumetric flow rate as m3/hr. The correct unit is m3/s (cubic metres per second) as noted by the respondent.

Odour concentration is correctly identified as odour units (ou). In measurement terms, one odour unit (ou) is defined by the concentration of odorous air that can be detected by 50% of members of an odour panel. An emission rate is the odour concentration (in ou) multiplied by, in the case of a stack source, the flow rate (in m3/s), and is generally represented as ou.m3/s. The terms ‘odour concentration’ and ‘odour levels’ are used interchangeably. As the submission noted, this is industry practice and accords with the EPA guidelines.

Air flow figure shows inconsistency

Submission 3 identified an inconsistency between the arrangement of the existing scrubbers shown in the REF, Figure 3-1 and the written description on page 20 under ‘Odour control and ventilation’.

Response

The diagram that appears in Figure 3-1 in the REF is incorrect. The submitter is correct in that air is extracted from the NSOOS, inlet works and the underfloor area of the screenings chamber for treatment.


5.5.3 Corrections

Reference to North Head vs Sydney Harbour National Park for heritage

Submission 3 stated that ‘North Head’ in the legend on Figure 5-7 should be ‘Sydney Harbour National Park’.

Response

Figure 5-7 from the REF shows listed heritage items. ‘North Head’ is included in the Australian Heritage Database as an item of National Heritage significance. This description was included in Table 5-7 of the REF. The submitter is correct that the area also corresponds to Sydney Harbour National Park.

Section 5.4.5 includes further information on heritage values.

Correction for reference to superseded regulation

We identified that the REF mistakenly references the Coastal Protection Regulation 2004 which has been superseded by the Coastal Protection Regulations 2011. This regulation has been reviewed and there is no change to the assessment in the REF.

5.6 Support for the proposal Submission 10 expressed support for the proposal and design of the new scrubbers. Other submissions supported replacing the scrubber and reducing odour emissions.

Response

Sydney Water notes the support for the proposal. Replacing the NSOOS scrubber is important work that will improve reliability and reduce odour emissions from the WWTP.


6 Justification of the proposal

The NSOOS chemical scrubber was built in 1992. Since then it has been substantially reconfigured and, as result of this and the scrubber’s age, is no longer performing reliably. In addition, the scrubber is unable to draw sufficient air flows from the NSOOS, which is causing corrosion in the network. These issues can contribute to high levels of odour emissions, which can impact sensitive receivers at North Head.

The proposal objectives are to:

replace the existing NSOOS chemical scrubber, before the existing scrubber reaches the end of its useful life

reduce corrosion and increase the air flow within the NSOOS.

A benefit of the proposal will be reducing odour emissions associated with the variable performance of the existing NSOOS chemical scrubber. The proposal will also reduce long-term operating costs and improve operational efficiency.

This proposal has been developed to address reliability concerns and reduce corrosion. It involves replacing and improving the NSOOS scrubber, as well as air flow within the NSOOS and the underfloor area of the screenings chamber.

The justification for the proposal remains unchanged as a result of this Decision report.


7 Conclusion

Sydney Water has assessed the potential impacts of the proposal, as required by Part 5 the EP&A Act. Section 2 outlines the public consultation process completed for the proposal. Twenty submissions were received following public exhibition of the North Head Scrubber Replacement REF, in October and November 2013.

The main issues raised in the submissions related to the need to improve odour emissions from the scrubber and the WWTP, and the scope of work proposed. Other matters raised included the alternatives considered, communication and stakeholder consultation, and environmental management.

Sydney Water has thoroughly considered the issues raised in the submissions in section 5. In considering the issues raised, we will:

continue with the proposal, because it is essential work

adopt the additional mitigation measures described in Appendix 3, which respond to matters raised in the submissions

monitor the BTF scrubber to confirm performance post commissioning

continue with other planned projects, which will indirectly contribute to odour reduction, including dosing units, a second cogeneration engine and additional waste gas flare

continue to review the effectiveness of the work to manage odour following the staged approach we are taking at North Head WWTP

aim to minimise impacts on the community.

Sydney Water considers that the proposed mitigation measures are appropriate to manage the proposal’s potential impacts and no further changes to the proposal are required. The proposal is not likely to result in a significant impact to the environment.



9 References

Australian Government 2006, Australian Heritage Database listing for North Head - Sydney, North Head Scenic Dr, Manly, NSW, Australia. Department of Environment.

CH2M HILL 2013, NSOOS and North Head Odour Control Options Report, prepared for Sydney Water

DIPNR 2004, Guideline for the Preparation of Environmental Management Plans, Department of Infrastructure, Planning and Natural Resources.

ELA 2007 North Head Sewage Treatment Plant Flora and Fauna Assessment Report prepared for Sydney Water.

ENSure 2013, (A GHD and SKM Joint Venture) North Head Wastewater Treatment Plant – NSOOS Scrubber Replacement Project, Odour Modelling and Assessment prepared for Sydney Water.

MWH 2004, North Head STP PARR Project Concept Design Odour Review prepared for Sydney Water

MWH+PB Joint Venture 2007, Condition Assessment of NSOOS Ventilation System prepared for Sydney Water.

Sydney Water 2013, Review of Environmental Factors, North Head Wastewater Treatment Plant NSOOS Scrubber Replacement Project

Documents

140311 NSOOS Scrubber Decision Report Final...Scrubber\140307_NSOOS Scrubber Repl acement Decision report.docx Publication number SW199 3/14 Sydney Water - Commercial in Confidence