Notice of Meeting

 

 

 

 

 

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Water, Waste and Sewer Advisory Committee Meeting

 

 

A Water, Waste and Sewer Advisory Committee Meeting of Byron Shire Council will be held as follows:

 

Venue

Conference Room, Station Street, Mullumbimby

Date

Thursday, 2 June 2016

Time

9.00am

 

 

 

 

 

 

 

Phillip Holloway

Director Infrastructure Services                                                                                           I2016/598

                                                                                                                                    Distributed 26/05/16

 

 


CONFLICT OF INTERESTS

What is a “Conflict of Interests” - A conflict of interests can be of two types:

Pecuniary - an interest that a person has in a matter because of a reasonable likelihood or expectation of appreciable financial gain or loss to the person or another person with whom the person is associated.

Non-pecuniary – a private or personal interest that a Council official has that does not amount to a pecuniary interest as defined in the Local Government Act (eg. A friendship, membership of an association, society or trade union or involvement or interest in an activity and may include an interest of a financial nature).

Remoteness – a person does not have a pecuniary interest in a matter if the interest is so remote or insignificant that it could not reasonably be regarded as likely to influence any decision the person might make in relation to a matter or if the interest is of a kind specified in Section 448 of the Local Government Act.

Who has a Pecuniary Interest? - a person has a pecuniary interest in a matter if the pecuniary interest is the interest of the person, or another person with whom the person is associated (see below).

Relatives, Partners - a person is taken to have a pecuniary interest in a matter if:

§  The person’s spouse or de facto partner or a relative of the person has a pecuniary interest in the matter, or

§  The person, or a nominee, partners or employer of the person, is a member of a company or other body that has a pecuniary interest in the matter.

N.B. “Relative”, in relation to a person means any of the following:

(a)   the parent, grandparent, brother, sister, uncle, aunt, nephew, niece, lineal descends or adopted child of the person or of the person’s spouse;

(b)   the spouse or de facto partners of the person or of a person referred to in paragraph (a)

No Interest in the Matter - however, a person is not taken to have a pecuniary interest in a matter:

§  If the person is unaware of the relevant pecuniary interest of the spouse, de facto partner, relative or company or other body, or

§  Just because the person is a member of, or is employed by, the Council.

§  Just because the person is a member of, or a delegate of the Council to, a company or other body that has a pecuniary interest in the matter provided that the person has no beneficial interest in any shares of the company or body.

Disclosure and participation in meetings

§  A Councillor or a member of a Council Committee who has a pecuniary interest in any matter with which the Council is concerned and who is present at a meeting of the Council or Committee at which the matter is being considered must disclose the nature of the interest to the meeting as soon as practicable.

§  The Councillor or member must not be present at, or in sight of, the meeting of the Council or Committee:

(a)   at any time during which the matter is being considered or discussed by the Council or Committee, or

(b)   at any time during which the Council or Committee is voting on any question in relation to  the matter.

No Knowledge - a person does not breach this Clause if the person did not know and could not reasonably be expected to have known that the matter under consideration at the meeting was a matter in which he or she had a pecuniary interest.

Participation in Meetings Despite Pecuniary Interest (S 452 Act)

A Councillor is not prevented from taking part in the consideration or discussion of, or from voting on, any of the matters/questions detailed in Section 452 of the Local Government Act.

Non-pecuniary Interests - Must be disclosed in meetings.

There are a broad range of options available for managing conflicts & the option chosen will depend on an assessment of the circumstances of the matter, the nature of the interest and the significance of the issue being dealt with.  Non-pecuniary conflicts of interests must be dealt with in at least one of the following ways:

§  It may be appropriate that no action be taken where the potential for conflict is minimal.  However, Councillors should consider providing an explanation of why they consider a conflict does not exist.

§  Limit involvement if practical (eg. Participate in discussion but not in decision making or vice-versa).  Care needs to be taken when exercising this option.

§  Remove the source of the conflict (eg. Relinquishing or divesting the personal interest that creates the conflict)

§  Have no involvement by absenting yourself from and not taking part in any debate or voting on the issue as if the provisions in S451 of the Local Government Act apply (particularly if you have a significant non-pecuniary interest)

RECORDING OF VOTING ON PLANNING MATTERS

Clause 375A of the Local Government Act 1993 – Recording of voting on planning matters

(1)   In this section, planning decision means a decision made in the exercise of a function of a council under the Environmental Planning and Assessment Act 1979:

(a)   including a decision relating to a development application, an environmental planning instrument, a development control plan or a development contribution plan under that Act, but

(b)   not including the making of an order under Division 2A of Part 6 of that Act.

(2)   The general manager is required to keep a register containing, for each planning decision made at a meeting of the council or a council committee, the names of the councillors who supported the decision and the names of any councillors who opposed (or are taken to have opposed) the decision.

(3)   For the purpose of maintaining the register, a division is required to be called whenever a motion for a planning decision is put at a meeting of the council or a council committee.

(4)   Each decision recorded in the register is to be described in the register or identified in a manner that enables the description to be obtained from another publicly available document, and is to include the information required by the regulations.

(5)   This section extends to a meeting that is closed to the public.

 


BYRON SHIRE COUNCIL

Water, Waste and Sewer Advisory Committee Meeting

 

 

BUSINESS OF MEETING

 

1.    Apologies

2.    Declarations of Interest – Pecuniary and Non-Pecuniary

3.    Adoption of Minutes from Previous Meetings

3.1       Water, Waste and Sewer Advisory Committee Meeting held on 3 March 2016

4.    Business Arising From Previous Minutes

5.    Staff Reports

Infrastructure Services

5.1       STP Flow Data Report...................................................................................................... 4

5.2       History and Future of Inflow and Infiltration in Byron Shire Council's Sewer Systems.... 8

5.3       Main Arm Reuse Options................................................................................................ 80

5.4       Container Deposit Scheme (CDS) Information Session................................................ 86

5.5       Scope of the Water, Waste and Sewer and Related Committees................................. 88   

 

 


BYRON SHIRE COUNCIL

Staff Reports - Infrastructure Services                                                                   5.1

 

 

Staff Reports - Infrastructure Services

 

Report No. 5.1             STP Flow Data Report

Directorate:                 Infrastructure Services

Report Author:           Peter Rees, Manager Utilities

File No:                        I2016/542

Theme:                         Community Infrastructure

                                      Sewerage Services

 

 

Summary:

 

The data presented in Tables 1-3 is for the period May 2014 to April 2016.

 

It is the monthly inflows to each STP; the highest daily flow for each month and a calculated ratio of the highest monthly daily flow to as assumed average dry weather flow.

 

  

 

RECOMMENDATION:

That the Committee note the report.

 

 

 

 


 

Report

 

The data presented in Table 1 below contains all inflows to each Sewage Treatment Plant (STP) collated by month as requested by the Committee.  The flows are for the period from May 2014 to April 2016.  Included in the Table is the highest daily flow received at the plant for each month.  The flows are not warranted as audited.

 

Table 2 contains a calculated ratio of the highest flow received for each month to an assumed average dry weather flow (ADWF).  The ADWF is not a current calculated value and is based on historical assessments of each system.

 

Table 3 contains all recycled water monthly flows from each STP. The flows are not warranted as audited.

 

Table 1 – STP Flows and Highest Daily Flow for the Month

 

 Total Monthly Flows (kL)

 

Highest Daily Flow for Month (kL)

 

 BASTP

 BBSTP

 BVSTP

OSSTP

TOTAL STP FLOW

BASTP

BBSTP

BVSTP

OSSTP

 

 

 

 

 

 

 

 

 

 

May-14

       9,824

      161,920

     38,922

41421

252087

366

5865

1617

1787

Jun-14

       9,297

      130,578

     35,074

36864

211813

340

5573

1461

1804

Jul-14

       9,645

      141,782

     33,465

40497

225388

410

4890

1170

2097

Aug-14

     15,353

      178,730

     76,823

54527

325433

1899

11791

8459

3786

Sep-14

       9,411

      148,768

     52,400

43527

254106

417

6139

2775

1847

Oct-14

       9,393

      144,868

     34,137

40689

229087

618

5334

1309

2484

Nov-14

       8,619

      132,092

     35,320

38089

214120

601

4791

1611

2213

Dec-14

     11,118

      154,976

     52,810

46256

265160

648

7600

5576

3417

Jan-15

     11,397

      177,643

   110,628

57935

357603

626

7380

9339

3479

Feb-15

     16,054

      174,031

   121,452

69952

381489

3862

13278

19599

12636

Mar-15

     10,614

      163,309

     67,063

48778

289763

461

6780

8686

2896

Apr-15

     10,930

      171,481

     84,414

48060

314885

575

7154

10676

2902

May-15

     16,025

      171,186

     78,472

55750

321432

2732

12371

15812

4199

Jun-15

     10,936

      146,013

     61,815

54928

273692

855

11101

7900

8092

Jul-15

     10,266

      151,286

     55,841

49723

267116

371

6127

2816

2532

Aug-15

       9,721

      127,397

     42,120

42918

222156

349

4430

1644

1912

Sep-15

       9,571

      125,259

     35,123

41516

211469

508

4778

1624

1956

Oct-15

       9,533

      138,474

     40,480

41014

229501

329

4908

2497

2047

Nov-15

       9,985

      155,571

     60,487

45040

271083

476

8329

4536

3562

Dec-15

       9,951

      169,819

     54,273

47875

281918

382

9201

3358

3078

Jan-16

     10,762

      171,169

     56,902

46960

285792

746

6933

3516

3344

Feb-16

       8,322

      160,291

     43,265

39143

251022

367

15951

3030

1897

Mar-16

     12,633

      190,703

   100,204

56002

359542

1063

13822

12357

6112

Apr-16

       9,781

      193,405

     46,091

41000

290277

352

30283

2761

1787

 

 

Table 2 – Peak Wet Weather Flow: ADWF Ratio

 

 

ADWF RATIO

 

 

 

BASTP

BBSTP

BVSTP

OSSTP

Byron Rainfall

 

ADWF

350.0

5000.0

1500.0

1200.0

 

May-14

 

1.0

1.2

1.1

1.5

32

Jun-14

 

1.0

1.1

1.0

1.5

62

Jul-14

 

1.2

1.0

0.8

1.7

18

Aug-14

 

5.4

2.4

5.6

3.2

313

Sep-14

 

1.2

1.2

1.8

1.5

29

Oct-14

 

1.8

1.1

0.9

2.1

16

Nov-14

 

1.7

1.0

1.1

1.8

85

Dec-14

 

1.9

1.5

3.7

2.8

120

Jan-15

 

1.8

1.5

6.2

2.9

234

Feb-15

 

11.0

2.7

13.1

10.5

307

Mar-15

 

1.3

1.4

5.8

2.4

171

Apr-15

 

1.6

1.4

7.1

2.4

131

May-15

 

7.8

2.5

10.5

3.5

223

Jun-15

 

2.4

2.2

5.3

6.7

137

Jul-15

 

1.1

1.2

1.9

2.1

49

Aug-15

 

1.0

0.9

1.1

1.6

46

Sep-15

 

1.5

1.0

1.1

1.6

104

Oct-15

 

0.9

1.0

1.7

1.7

43

Nov-15

 

1.4

1.7

3.0

3.0

151

Dec-15

 

1.1

1.8

2.2

2.6

145

Jan-16

 

2.1

1.4

2.3

2.8

82

Feb-16

 

1.0

3.2

2.0

1.6

48

Mar-16

 

3.0

2.8

8.2

5.1

386

Apr-16

 

1.0

6.1

1.8

1.5

50

 

Table 3 – Recycled Water Flows

 

 

RECYCLED WATER

 

Byron Rainfall

BASTP REUSE

BBSTP Reuse

BVSTP Reuse

Total Reuse

 

 Mm

kL

kL

kL

kL

May-14

32

944

27099

5219

33262

Jun-14

62

786

26839

910

28535

Jul-14

18

1247

29184

16379

46810

Aug-14

313

792

31095

2578

34465

Sep-14

29

1318

29237

2

30557

Oct-14

16

1359

30301

13344

45004

Nov-14

85

502

33455

11757

45714

Dec-14

120

341

39177

4480

43998

Jan-15

234

0

51018

0

51018

Feb-15

307

0

34053

0

34053

Mar-15

171

498

40427

0

40925

Apr-15

131

483

57263

0

57745

May-15

223

243

30178

0

30421

Jun-15

137

264

23369

3363

26995

Jul-15

49

384

25886

2603

28873

Aug-15

46

405

26182

4414

31000

Sep-15

104

375

50654

1237

52266

Oct-15

43

1778

47741

2810

52329

Nov-15

151

1821

47105

2242

51168

Dec-15

145

0

12604

0

12604

Jan-16

82

162

17072

4096

21331

Feb-16

48

3

16384

0

16387

Mar-16

386

0

36822

0

36822

Apr-16

50

0

29015

754

29769

 

Financial Implications

 

Nil

 

Statutory and Policy Compliance Implications

 

Nil

 


BYRON SHIRE COUNCIL

Staff Reports - Infrastructure Services                                                                   5.2

 

 

Report No. 5.2             History and Future of Inflow and Infiltration in Byron Shire Council's Sewer Systems

Directorate:                 Infrastructure Services

Report Author:           Peter Rees, Manager Utilities

File No:                        I2016/543

Theme:                         Community Infrastructure

                                      Sewerage Services

 

 

Summary:

 

The final report on the Mullumbimby Inflow and Infiltration programme has been attached for discussion.

 

  

 

RECOMMENDATION:

That the Committee note the report.

 

Attachments:

 

1        Mullumbimby Inflow & Infiltration Integrated Strategy Final Annual Report June 2010, DM990881 , page 10  

 

 


 

Report

 

There have been comments regarding the level of stormwater ingress into the Mullumbimby sewerage system despite there being no sewer overflows into the river as a result of this ingress. It has been suggested  Council needs to revisit its Mullumbimby stormwater inflow mitigation measures and more broadly review stormwater ingress into all the Shire’s catchments.

 

As a starting point, the final Council considered report on the Mullumbimby Inflow and Infiltration programme has been attached for consideration.

 

Financial Implications

 

Nil

 

Statutory and Policy Compliance Implications

 

Nil

 


BYRON SHIRE COUNCIL

Staff Reports - Infrastructure Services                               5.2 - Attachment 1

BSC_CMYK
Byron Shire Council 
MULLUMBIMBY SEWERAGE SYSTEM INFLOW AND INFILTRATION PROGRAMME PRP 1 INTEGRATED STRATEGY
Final Project Review June 2010
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MULLUMBIMBY SEWERAGE SYSTEM INFLOW AND INFILTRATION PROGRAM INTEGRATED STRATEGY FINAL PROJECT REVIEW

 

TABLE OF CONTENTS

 

1.0       SUMMARY AND RECOMMENDATIONS. 3

2.0       INTRODUCTION.. 6

3.0       SECTION 1: Project Element Review.. 8

3.1 Overall Project Coordination. 8

3.2 Data Collection and Analysis. 8

3.3 Public Sewerage Infrastructure Repairs. 9

3.4       Private Sewerage Infrastructure Repairs. 14

3.5 Stormwater 16

3.6 Community Education. 17

3.7 Pump Station Review and Upgrade. 17

4.0       SECTION 2: Project Evaluation. 19

4.1 Key Performance Indicators Overview.. 19

4.2 Maximum Ratio Wet Weather Flow (Daily) / Dry Weather flow (Daily) 20

4.3 Overflow Events to the Brunswick River 20

5.0       SECTION 3: Project Alternatives and Recommendations. 22

5.1 Low Pressure Pump System.. 22

5.2 Gravity Sewerage System Maintenance. 23

5.3 Recommendations. 24

APPENDIX 1. 26

 


 

1.0    SUMMARY AND RECOMMENDATIONS

 

The Mullumbimby sewerage system has historically suffered significant stormwater inflow and infiltration problems with flows well in excess of 14 x average dry weather flow being received in large rainfall events. This has resulted in sewage overflows to the Brunswick River. In 2007 Council developed and adopted the Mullumbimby Sewerage System Inflow and Integration program PRP 1 Integrated Strategy. 

 

The Integrated Strategy focused effort on the following areas:

 

·    Data Collection and Analysis

·    Public Sewerage Infrastructure Rehabilitation

·    Private Sewerage Infrastructure Repairs

·    Stormwater Maintenance

·    Public Education

·    Pump Station Analysis and Upgrade

 

The strategy outlined a program of work for three years costing $0.5 million per annum and required a report to be prepared annually to analyse the effectiveness of the program.

 

The strategy was also endorsed by the Department of Environment, Climate Change and Water (DECCW) and incorporated in PRP 2 on Licence #830.

 

Annual reports on progress have been reported to Council in 2008 and 2009.  This report is the final annual report considering the outcomes of the implementation of the three year Strategy. The Final Report includes:

 

·  a review of each project element defined in the original Strategy

 

·  an evaluation of the project against both the original KPIs identified in the Strategy and all the relevant data collected.

 

·  analysis of alternatives and makes recommendations on the direction the project should take to ensure there are no overflows into the Brunswick River due to stormwater ingress.

 

The Final Report documents the extensive work completed in rectifying defects in the stormwater system and public and private sewers but concludes that the project has not achieved the KPI targets for reducing overflow occasions to zero and reducing the ratio of Peak Weather Flow to Average Dry Weather flow to only 7 times.  The project has however had the following positive impacts

 

§ A reduction in overflow occasions by 15%.

§ A reduction in overflow volume by 39%.

 

The project has also demonstrated the mains of the sewerage system are not the cause of the stormwater ingress – there has been only four defects identified in the past three years in the sewer mains.  The significant defects in the system are in the sideline connections to the properties and the property’s drainage infrastructure.  To date 543 of 703 property connections have been inspected with 61% found to have a defect.  Of the properties, 704 of 766 have been inspected with 46% found to have defects.

 

The augmented sewerage system is now at a level which has adequate capacity to transfer all flows received to the new treatment facility.  Considering the largest storm event of 2009/10 as an example, Mullumbimby generated 12.373 ML of effluent and Brunswick Heads 2.172 ML – with total effluent delivered to the STP’s of 14.545 ML.  This is significantly below the 22.04 ML per day of flow that can be fully treated at the new Brunswick Valley STP and only eight times the combined average dry weather flow of Brunswick Heads and Mullumbimby.

 

High levels of stormwater ingress will always be undesirable because it leads to higher energy costs associated with pumping and treatment, but the ratio of peak wet weather flow to average dry weather flow cannot be used as the measure of system capacity provided:

 

1.   The system has sufficient pumping capacity to transfer flows to the treatment facility;

2.   The system has sufficient treatment (and storage) capacity to adequately treat the transferred flows; and

3.   The system is adequately monitored and maintained to prevent peak wet weather flows from increasing.

 

Completion of the Brunswick Area Sewage Augmentation Scheme (BASAS) and ongoing maintenance work will ensure the Brunswick valley (Mullumbimby and Brunswick Heads) sewerage system satisfies these three criteria.  This is supported by the computer model developed using both the data collected in this project and Council’s asset management system.

 

The existing gravity sewerage systems complete with the newly constructed transfer pump stations (SPS 4000 Mullumbimby and SPS 2000 Brunswick Heads) and the new Brunswick Valley sewage treatment plant, will be capable of collecting, transferring and treating sewage flows for all rainfall events up to the 1 in 20 year Average Recurrence Interval (ARI) event and possibly above.

 

In accordance with the resolution of Council, this report considers the option of addressing the problem of stormwater ingress through the retrofitting of a Low Pressure Pumping System (LPPS) to the Mullumbimby sewerage reticulation system. This option would have a high capital cost (estimated at $19,000 per property) and will not eliminate stormwater inflow and infiltration because defects in the upstream private sewers will continue to be a problem and source of stormwater ingress. This conclusion has been demonstrated in the recent installation of a LPPS unit at one property in the catchment and subsequent flow monitoring indicates wet weather flows are up to 20 times the dry weather flow due to stormwater ingress through defects in the upstream private sewers on the property. The reasons a LPPS is not recommended as a preferred project alternative are further discussed in Section 3 of this report.

 

The condition of the public and private sewerage system is dynamic and defects that result in stormwater ingress can emerge due to deterioration and private works. For this reason it will be necessary to complete residual corrective works in the worst effected sub catchments and also ongoing maintenance work so that the level of stormwater ingress is progressively decreased.

 

The BASAS incorporates wet weather storage capacity that assists with pumping capacity and eliminating sewage overflows that occur when the sewerage system is overwhelmed. The level of wet weather storage capacity could be further increased by the implementation of a bulk effluent storage dam and constructed wetlands at the Brunswick Valley STP (Vallances Road) site. These facilities were part of the concept for the BASAS and have been assessed in the EIS process but were deferred due to financial constraints. Implementation of a bulk effluent storage dam and constructed wetlands would also improve integrated effluent management outcomes that will provide sustainable benefits to the community and the environment.

 

The recommended future works to be undertaken on the Mullumbimby sewerage system are:

 

1.   complete the work on the gravity system in catchments 4001 and 4003b;

2.   continue with inspection of private assets;

3.   implement routine investigation and repairs for both public and private infrastructure in our operational and maintenance activities; and

4.   investigate further the use of the original BASAS project effluent storage dam and the constructed wetlands for supplementary storm flow storages and/or treatment.

 

 


2.0    INTRODUCTION

 

The purpose of this report is to provide a review of the Mullumbimby Inflow and Infiltration project in accordance with the Integrated Strategy developed in 2007 and endorsed by Council (Resolution 07-208) and the Department of Environment Climate Change and Water (DECCW PRP1and PRP2).

 

This report follows on from

 

§ the annual Mullumbimby Inflow and Infiltration Integrated Strategy review report prepared in June 2008 and received and noted by Council (Resolution 08-490); and submitted to the DECCW who issued PRP3 in response;

§ a review of the project by a “consultant conversant with sewerage design and repair” in response to Council resolution 08-748; and

§ Council resolution 09-854 in response to the Consultant’s report.

 

The review assesses actual data against the nominated Key Performance Indicators and makes an assessment of the success or otherwise of the strategy.  The report also makes recommendations for future work required to mitigate the stormwater inflow and infiltration into the Mullumbimby sewerage system.  The report will be presented to Council in accordance with the resolution of Council.

 

In addition to reviewing the project, this report also addresses specific issues raised in Council Resolution 09-854.

 

09-854        Resolved:

 

1.      That Council notes the Consultant's report titled 'Final Report Mullumbimby Inflow Infiltration Review Byron Shire Council'.

2.      That shortfalls in the company Aurecon's report entitled 'Final Report Mullumbimby Inflow Infiltration Review Byron Shire Council' (#889165) be noted, including:

a.      the report does not answer the question posed by Council in its Resolution 08-748 namely to establish whether replacement or continued repair (or a combination of the two) would be the best option to resolve the Mullumbimby Inflow and Infiltration problem.  It advises putting the issue off for some years, thus setting the scene for a panic at that time.

b.      it estimates a cost of $2.9million for the low pressure pump (LPPS) option.  It states that costing the other (repair) option is extremely difficult, and that such an approach is difficult to maintain (see Annexure 12, Page 3 of 49).  Council has past expenditures and could forecast future ones.  A comparison is however not made in the report.  A brief comparison would however indicate that replacement at $2.9million is a far more cost effective option than repair.  The report dismisses the option however, simply saying it 'is very expensive'.

c.      the report makes no assessment of the success rate of the extensive repair programme carried out by Council to date.  Aurecon may have been influenced in this by the Project Brief (Contract No: BSC/2009/00003; Pp 5-6) stating 'In response to Item 7, in April 2005 a report was prepared and presented to the Brunswick Wastewater Steering Committee quantitatively evaluating the work done.  The data at the time indicated there had been measurable improvements and that overflows to the Brunswick River had been reduced by 60% and total flows in the system by 15%.  That data was re-examined by the Committee and extreme doubts raised.  In addition, there are now several years of data since 2005.  These do not back up the claimed reduction.

d.      the report ignores years of overflow data collected by Council, as presented in its I/I Programme for PRP1, Annual Project Review of June 2008.  Those data indicate system flows of about 14 times ADWF in 2005, 2006 and 2008.  Measurement failed in May 2009, an event sure to have exceeded all others.  April 2009 had already reached 12.4 times ADWF.  Overflow occurs regularly from the Mullumbimby system.  Sewer total flows exceed 10 Ml/day (11 times ADWF) on about 3 days a year (many more in 2009).

e.      the report argues on the flimsiest of grounds that Mullumbimby should accept as normal its current rate of overflows (assessed as a 1-in-3-month event).

f.       the report argues that extreme conditions in Mullumbimby drag its performance down from NSW's 1-in-20-year norm.  It fails to examine what happens on the top half of Australia's east coast.

g.      the report claims that the Sewerage Augmentation Scheme currently being built will eliminate sewer overflows.  It fails to mention however that flows greater than 7 times ADWF will go untreated at the new STP, presumably overflowing there instead of in town (this ratio needs checking but the issue is presented in the Augmentation design).

3.      That key performance indicators of the Mullumbimby Inflow and Infiltration situation be reviewed six months before the opening of the new Brunswick Valley STP.

4.      That a decision on the level of leakage of the system, acceptable on a cost/benefit basis against a new sewerage system, be redetermined at that time. (Tabart/Staples)

 

Section 1 of the report provides a review of each project element defined in the original Strategy.

 

Section 2 provides an evaluation of the project against both the original KPIs identified in the Strategy and all the relevant data collected.

 

Section 3 analyses alternatives and makes a recommendation on the direction the project should take to ensure there are no overflows into the Brunswick River due to stormwater ingress.

 


3.0    SECTION 1: Project Element Review

 

       3.1 Overall Project Coordination

 

The majority of works incorporated in the Integrated Startegy have been completed but some work remains outstanding.  For the public infrastructure, all mains and 77 % of the sidelines have been CCTV’d with only areas in catchment 4001 yet to be completed. An iterative process has been necessary because it is not possible to identify all defects with CCTV technology through one inspection.

 

Defect generation is a dynamic occurrence with development; tree root ingress and age deterioration all contributing to the generation of new defects.  One area of concern is the sewer relining applied to some mains and manholes in 2000/01 is now failing.  A programme has therefore been developed to re inspect areas previously done.  This should be considered normal sewerage operations and maintenance for Mullumbimby.

 

The remaining CCTV work and repairs are being completed in the 2010/11 year as part of the budget allocation in the current Management Plan.  The private asset inspections will also need to be continued for the foreseeable future.  This can be completed with the budget allocation and in association with routine maintenance and operational work. The age, state and ground conditions of the private sewers mean this is a recommended function for the Mullumbimby sewerage system.

 

The total funds approved for the Mullumbimby Inflow and Infiltration Integrated Strategy were $500,000 per year for three years.  In total $1,408,870 was spent over the three years.  Part of this expenditure has included the procurement of CCTV technology; data collection technology; switchboard technology and the training of operational staff in its use.

 

       3.2 Data Collection and Analysis

 

In March 2008 the new telemetry SCX Data monitors were installed into Sewer Pumps Stations 4001, 4002, 4003, 4004 and 4005.  These monitors provide inflow; outflow; well heights and rainfall data.  They are incorporated within Council’s overall telemetry system.  In addition, flow monitors were installed at the Palm Park and Mill Street overflow points.

 

Unfortunately, the Palm Park monitor was vandalised and the radio unit and antenna were stolen.  Prior to this the respective pump station collection wells were calibrated so that the level at which the pump stations overflow was verified on the telemetry.

 

In 2009, using data gained from the SCADA system and the asset management data, a H2O Map Computerised Sewer Model for the Mullumbimby sewerage system was established.  This model can be used to provide a measure of the system response to various rainfall events with the current sewerage system and again with the upgraded sewerage system.  The results of this modelling are shown in Table 1 below.

 

The following points need to be stressed when using this data

 

§ The model is an estimation based on an assumed unit Hydrograph.  The results cannot be considered definitive but can be used to compare scenarios and provide a qualitative indication of system response.

§ The figures in Table 1 are flows over a three day period (to derive average daily flow, divide the figures in Table 1 by three)

 

Table 1

 

H2O Map Model of Mullumbimby Sewerage System Before and After Upgrade for Several Rainfall Events

 

Scenario / Parameter

DWF (No Storm)

1 in 2 year storm of 1 hour duration

1 in 2 year storm of 24 hours duration

1 in 5 year storm of 1 hour duration

1 in 5 year storm of 24 hours duration

1 in 20 year storm of 1 hour duration

1 in 20 year storm of 24 hours duration

Rain Fall (mm)

0

50

178

64

246

83

344

YEAR

2010

2015*

2010

2015*

2010

2015*

2010

2015*

2010

2015*

2010

2015*

2010

2015*

3 Day System Inflow (ML)

3

3

9

8

19

19

9

9

25

26

11

11

34

34

3 Day STP Inflow (ML)

3

3

8

8

18

19

9

9

21

24

10

11

25

29

3 Day Reticulation Overflow (ML)

0

0

0

0

1

0

0

0

4

1

0

0

9

5

 

Notes:

§  2015* is the Mullumbimby Sewerage System with an allowance for development in accordance with current plans

§  The rainfall events modelled are:

No rainfall

1 in 2 year rainfall event of 1 hour duration (50mm)

1 in 2 year rainfall event of 24 hours duration (178mm)

1 in 5 year rainfall event of 1 hour duration (64mm)

1 in 5 year rainfall event of 24 hours duration (246mm)

1 in 20 year rainfall event of 1 hour duration (83mm)

1 in 20 year rainfall event of 24 hours duration (344mm)

 

Observations from the modelling

 

§ The existing sewerage system overflows for all rainfall events over the 1 in 2 year event (50mm in 1 hour).

§ The upgraded system will overflow in the 1 in 20 year event of 24 hours duration with only a nominal overflow in the 1 in 5 year event of 24 hours duration.

§ The model indicates that there will be no overflows at the Mill Street and Palm Park overflow points but rather will occur through manholes due to the hydraulic grade line at these locations.  There will therefore be no direct wet weather overflow into the Brunswick River.

§ The quantum of flow to the new STP is significantly below the design wet weather maximum for all events (the maximum 3 day flow predicted is 29 ML which gives a daily flow average of 9.7 ML.  The design wet weather maximum flow the STP can fully treat in one day is 22.04 ML)

§ The transfer pump station 4000 is not required to operate at its capacity during these peak flow days.

 

Based on the modelling it could therefore be concluded that once the upgraded sewerage system is commissioned, there will be no wet weather overflows into the Brunswick River and the new STP will have the capacity to fully treat all wet weather flows received at the plant.

 

       3.3 Public Sewerage Infrastructure Repairs

 

Work on the public sewerage system has been an iterative approach with work being undertaken on the entire reticulation system in catchments 4001; 4002 and 4003a and b.  The camera and repair of sidelines (sewer lines from the sewer mains to the property boundary shafts) was targeted.

 

CCTV footage prepared under a contract undertaken in 2001 was initially used to identify repairs to the sewer mains.  An in house capability to undertake pipeline inspections with Council’s own personnel and CCTV equipment has been developed during the course of this project.  These reinspections have been necessary as new defects were identified mainly due to tree root ingress.

 

There has been no evidence found that the sewer mains and pipe joints are a systemic cause of stormwater inflow.  Only four instances have been identified over the 3 years of this strategy that required a sewer mains repair. Refer Photographs 1 - 4 below of some of the deep mains CCTV’d that highlight the generally good state of Council’s sewer mains.

 

Photograph 1

AP7 to AP6-tree root bung inside a 300mm gravity main

 

Photograph 2

AP7 to AP6- Good General condition of the 300mm gravity main


 

Photograph 3

AP14 to AP13-Good General condition of the 300mm gravity main in 3A catchment

 

Photograph 4

AT1 to AP13 - 150mm Gravity Main General Condition

 

 

Apart from the four isolated single source defects located in the mains, the defects in the public infrastructure have been located in the sideline connections to the properties.  An area of particular weakness has been found to be the connections of these sidelines to the mains.

 

There are 703 property connections.  Inspections have been done on 543 and of these, there have been defects in 332 connections – 61% of the assets have had some form of defect to permit stormwater ingress.  The repairs have varied from full sideline replacements to replacement of the boundary shaft.  Refer to Photographs 5 to 10 below for some typical defects encountered.

 


 

Photograph 5

Stuart Street cracked pipe

Photograph 6

AP14 to AP13-Dislodged joint + Infiltration & tree roots in a 150mm house connection

 

 

Photograph 7

New City Road crack where BS Connects to Main

 

Photograph 8

150mm house connection with tree root infiltration

 

 

Photograph 9

Jubilee Avenue leak at joint on riser

 

Photograph 10

Cedar Road broken bend at bottom of shaft

 

Repair work in catchments 4003a and b is ongoing and both CCTV and repair work in catchment 4001.

 

       3.4    Private Sewerage Infrastructure Repairs

 

Overflow Relief Gully “Pop Tops” were installed throughout catchment 4002 during November and December 2007.

 

Inspections of the private sewerage infrastructure commenced in February 2008.  The process has been as follows:

 

§ enter the property;

§ undertake a physical above ground inspection of the plumbing system;

§ undertake a CCTV inspection of the underground pipes and fittings;

§ identify defects (note it cannot be guaranteed that all defects will be identified as in some cases a defect is not noticeable unless it is raining at the time);

§ send the property owner a letter advising of defects found and requesting repairs to be undertaken;

§ if repairs not done, a follow up letter advising repairs must be done within 28 days;

§ if repairs not done a follow up letter with a quote for Council to effect the repairs;

§ once repairs done, a follow up inspection undertaken by Council.

 

In total, there are 766 properties in catchments 4001, 4002 and 4003a and b.  Since February 2008, 704 properties have been inspected.  The results are:

 

Week Ending 30/07/10

Total Inspections

704

 

Defective

321

46%

Repaired

239

74%

Repairs in progress

34

11%

No response

48

15%

 

A critical point from this data is that 46% of the properties have defects that permit the ingress of stormwater.  This statistic gives credibility to the statement that private sewerage infrastructure can potentially contribute up to 60% of stormwater inflow and infiltration in a sewerage system (refer Aurecon report Mullumbimby Inflow Infiltration Review dated 11 September 2009 Section 4.3).

 

Another key point to arise from this part of the project is that it has not been possible to fully identify all defects in a plumbing system with one inspection.  This has necessarily become an iterative process whereby ongoing inspections are required, preferably under wet conditions although not too wet to prevent CCTV work.


Photograph 11

Stormwater Collection System Feeding directly to Sewer System Stuart St

 

 

 

 

 

Photograph 12

Stormwater pipe Discharging to Sewer System Dalley St (1)

 


 

Photograph 13

Stormwater pipe Discharging to Sewer System Dalley St (2)

 

 

Photograph 14

Broken Fitting Private Infrastructure

 

 

      

       3.5 Stormwater

 

The Stormwater crew commenced work in November 2007.  The crew consists of two men, a contract excavator and a 3 tonne tipper truck.  In total the following work has been done on the stormwater system.

 

§ Removal of in excess of 50 tonnes of rubbish from the open drains.

§ Rehabilitation of 19,800 metres of stormwater drains across catchments 4001; 4002 and 4003a and b.

§ Re established 2.2 kilometres of open drains to the Brunswick River and Kings Creek.

§ Refurbishment of culvert crossings.

§ Flushing of 500 metres of stormwater pipes.

 

This work has been very successful in getting the Mullumbimby stormwater system operational again.  The extent of localised flooding during large rainfall events has been all but removed.  This prevents the stormwater finding an alternative path into the sewerage system.

 

There have been several letters of commendation received from the residents of Mullumbimby for this work in particular noting how the stormwater no longer ponds around their homes.

 

       3.6 Community Education

 

The focus of the communication strategy has been on direct contact with individual householders.  This was possible because the large majority of houses (and associated private sewers) were individually inspected allowing direct communication on the project objectives and issues with the residents of Mullumbimby.  In addition, there was follow up with many of the owners of properties with defects allowing further information to be provided on the problem of stormwater ingress into the Mullumbimby sewers.  Through the process of letters, inspections and direct dialogue there has been a high awareness in the community of the project and also a high level of cooperation.

 

In addition to the inspections on the sewer system, considerable work has been completed in maintaining and upgrading the stormwater system.  This work has brought the crews into direct contact with many residents and allowed further communication and promotion of the integrated strategy aims.  For many residents it was an opportunity to understand first hand the relationship between ineffective stormwater drains that increase the level of the water table and ultimately increase the amount of stormwater ingress into the sewerage system.

 

To complement the process of direct communication, an information brochure was produced and circulated to residents.

 

During the implementation of the strategy several articles and advertorials were produced on the Brunswick Area Sewerage Augmentation Scheme and this information also included discussion on the associated Mullumbimby Integrated Inflow and Infiltration reduction strategy.  This information has also been made available on the web.

 

Formal reporting on the progress and outcomes of the implementation of the strategy has occurred via annual reports to Council and this information has also been available to the community.

 

       3.7 Pump Station Review and Upgrade

 

The review was completed in October 2007.  The recommendations in part were:

 

§ Connect 4001 rising main into the delivery main to bypass PS4003.

§ Upgrade the switchboard at PS4003 to allow parallel pumping during high flows.

 

Both of these recommendations are consistent with the Brunswick Area Sewage Augmentation Scheme and were completed in 2008.  In addition, a bypass pipeline was installed at the Mullumbimby STP from the sedimentation tanks to the tertiary pond.  This allows controlled overflow of the increased flow delivered to the STP during high flows.  This ensures that the diluted sewage storm flows receive primary treatment during storm events.

 

Constraints in the 4003 rising main prevented pumping station 4001 pumping directly to the STP concurrently with 4003 due to excessive head loss in the pipeline.  The final pump station configuration will therefore be implemented with completion of construction of the Brunswick Area Sewerage Augmentation Scheme.  This is currently expected to occur in of October 2010.  This is when the flows will be diverted from the existing Mullumbimby and Brunswick Heads STPs to the new Brunswick Valley STP at Vallances Road and pump station 4000 will become operational.

 

The new pumping configuration will then become:

 

§ PS4001 will pump direct to PS4000 (and not through PS4003)

§ PS4002 will pump direct to PS4000 (and not through catchment 4003a)

§ The emergency overflow storage of 350 kilolitres will be operational

 

The advantages of this configuration are:

 

§ PS4000 will have a single pump capacity of 167 litres/second, and the ability to have two pumps pumping in parallel.  This provides a pumping capacity well in excess of four times the existing 4003 pump station capacity.

§ Magnetic flow meters have been installed to measure the flow from PS4000 and the total flow being received at the STP.  This will provide more accurate flow data than the current monitoring system which uses ultrasonic technology.

§ Once the changeover occurs, work will commence to convert PS4003 from a dry well to a wet well configuration.  This will provide an estimated additional 150 kilolitres of wet weather storage.

 

As a practical example of what will happen in the future, it is useful to consider the largest flow event of the past 12 months in both Brunswick Heads and Mullumbimby.  It is necessary to look at both areas as it is the combined flows that will be received at the new treatment facility.

 

The largest flow event occurred on the 7/2/2010.  The Mullumbimby system, including overflows, recorded 12.373 ML and Brunswick Heads recorded 2.172 ML – giving a combined total flow of 14.545 ML.  This is comfortably below the design treatment capacity of 22 ML/day.  The actual combined flow also equates to eight times the current combined average dry weather flow.

 

Therefore on the largest storm event during the past 12 months which was close to a 1 in 20 year event, there would have been no overflows and all flows would have been fully treated in the upgraded sewerage system.

 


4.0    SECTION 2: Project Evaluation

 

       4.1 Key Performance Indicators Overview

 

The adopted Performance Indicators for the project are detailed in Table 1 :

 

Table 1

PRP 1 Project Key Performance Indicators

 

Key Performance Indicator

2007

2008

2009

Maximum Ratio  Wet Weather Flow (Daily) / Dry Weather flow (Daily)

12

9

7

Number of Collection System Overflow Events to the Brunswick per year (for a 60 mm rainfall event)

0

0

0

Number of Collection System Overflow Events to the Brunswick per year (for a 85 mm event)

 

0

0

 

The Average Dry Weather Flow is taken as 953 kL/day; and the years referred to in Table 1 are DECC licence years commencing 27 April and finishing 26 April.  Therefore:

 

2007     refers to 27 April 2007 to 26 April 2008

2008 refers to 27 April 2008 to 26 April 2009

2009 refers to 27 April 2009 to 26 April 2010

 

The raw flow data is contained in Appendix 1.  For 2005 to 2007 the data listed is for days with rainfall above 3 mm commencing April 2005.  Days with no rain are included when there was an overflow occurring due to ongoing stormwater infiltration following the rainfall event.  Years 2008 to 2010 has all days.  The data recorded is:

 

§ Date

§ Flow received at STP

§ Rainfall

§ Overflow Mill St

§ Overflow Palm Park (Estimated)

§ Ratio Peak Wet Weather Flow / Average Dry Weather Flow

 

The actual Key Performance Indicators calculated for each of the three years are:

 

Table 2

Actual Key Performance Indicators

(Derived from Data in Appendix 1)

 

Max PWWF/ADWF

No of Overflows for <60mm Rainfall

No of Overflows for <85mm Rainfall

2007/08

14.0

7

8

2008/09

12.4

4

9

2009/10

12.4

3

4

 

Other significant data that can be taken from Appendix 1 is shown in Table 3

 

Table 3

Other Significant Data

Indicator

2007/08

2008/09

2009/10

Total Rainfall Recorded (mm)

2,198

2,035

1,795

No of Days of Rainfall

168

159

141

Total Yearly System Flow

637,984

635,064

545,076

Total No of Overflow Events

8

11

7

Total Overflow Volume (kL)

39,476

22,128

28,056

Maximum Ratio Peak Wet Weather Flow / Average Dry Weather Flow

14.0

12.4

12.4

 

The project has not achieved any of the stated KPI targets.  A discussion of each KPI is provided below.

 

       4.2 Maximum Ratio Wet Weather Flow (Daily) / Dry Weather flow (Daily)

 

This ratio has decreased over the life of the project from 14.0 to 12.4.  This is a modest decrease and it is doubtful that the ratio can ever be reduced to the currently discussed 5 and 7 times.  The report undertaken by Aurecon last year demonstrates that for the Mullumbimby system characteristics, higher peak wet weather ratios are to be expected (refer Aurecon report Mullumbimby Inflow Infiltration Review dated 11 September 2009 Section 3.3).

 

High levels of stormwater ingress will always be undesirable because it leads to higher energy costs associated with pumping and treatment, but the ratio of peak wet weather flow to average dry weather flow cannot be used as the measure of system capacity provided:

 

§ The system has sufficient pumping capacity to transfer flows to the treatment facility;

§ The system has sufficient treatment (and storage) capacity to adequately treat the transferred flows; and

§ The system is adequately monitored and maintained to prevent peak wet weather flows from increasing.

 

Completion of the Brunswick Area Sewage Augmentation Scheme (BASAS) and ongoing maintenance work will ensure the Brunswick valley (Mullumbimby and Brunswick Heads) sewerage system satisfies these three criteria. 

 

Completion of the work in catchment 4001 and continuing with the private asset defect identification and repair program is recommended to continue the process of decreasing the volume of stormwater ingress.

 

       4.3 Overflow Events to the Brunswick River

 

This KPI was split into two – one for 60 mm rainfall events and one for 85 mm rainfall events.  The project failed to reach the nominated targets.  It should be noted however that overflows into the Brunswick River have decreased over the life of the project.  This is a positive result.

 

If this fact is also viewed with the other data of reduced total flows in the system by 15% (albeit on reduced rainfall); and total overflow volume reduction of 39%, then it can be argued the work done to date is having a measurable and positive effect.

 

It should also be noted that of the seven overflow events in the past year,

 

§ Event 22/5/2009 – there was a power failure in Mullumbimby that increased the overflow volume.

§ Event 9/11/2009 – there was only one pump operating at pump station 4003 due to a pump failure. This increased the overflow volume.

§ Event 7/2/2010 – there was 305mm of rain recorded at the PS4003 rain gauge in a 12 hour period. This would put the event close to the 1 in 20 year ARI category. .The model projects a three day system flow of approximately 30 ML – which is what was received.

 

If the power blackouts and pump failures did not occur, the overflow volume reduction would have been greater.  This also highlights the importance of completing the project element of pump station reconfiguration.  This will be finalised under the Brunswick Sewage Augmentation Scheme in October 2010 when PS4000 becomes operational and the system flows are transferred to the new treatment facility.

 

When the BASAS is completed and the new pumping arrangements are in place, the overflows into the Brunswick River will cease under normal operating conditions and for all rainfall events up to the 1 in 20 ARI event and possibly even above.

 

It is expected that dry weather flows will increase with growth and additional development in the catchment. This growth in combination with wet weather flows could cause the treatment capacity to be compromised sooner than the 20 year design life. This risk can be mitigated and is discussed further in Section 3 below.

 


5.0    SECTION 3: Project Alternatives and Recommendations

 

Following on from the June 2008 Annual Review and the September 2009 Aurecon reports, there are only two practical project configurations to reduce the Mullumbimby inflow and infiltration with the objective of having no overflows into the Brunswick River. These are:

 

§ Low Pressure Pump System – retrofitting low pressure pump units and associated pipework in place of the current gravity sewer system.

§ Gravity Sewerage System Maintenance – continue with the identification and repair of defects in the existing gravity system and provide adequate storage for peak wet weather flows.

 

These configurations are discussed separately below.

 

       5.1 Low Pressure Pump System

 

The concept that a Low Pressure Pump System (LPPS) will remove inflow and infiltration of stormwater into the sewerage system needs to be discussed further as there is now additional data on the performance of this system.  The Mullumbimby Public School installed a private pump station earlier this year which essentially acts as a LPPS.  The effluent from the site collects in the pump well and is pumped off site.

 

In June of this year a magnetic flow meter was installed on the discharge line to monitor the flows being discharged from the site.  The data from this monitoring is shown in Table 4 below.

 

Table 4

Flow Data Mullumbimby Public School

 

This data provides a clear example of the risks associated with implementing a LPPS.  The Mullumbimby Public School, during the rainfall event on 28/7/2010, discharged in excess of 20 times its average dry weather flow.  The school has significant amounts of rainfall entering its drainage system both as inflow and as infiltration.

 

The pump system is more efficient than the gravity sewer system at removing the stormwater inflow off the site and into the public sewerage system.  Therefore, unless all the house drainage systems up stream of the pump unit are free of defects, installation of LPPS units on a large scale in Mullumbimby could increase the amount of stormwater entering the system in the short to medium term.  With any LPPS project it would be necessary to continue with the identification and repair of private property drainage defects and this would need to continue for years to keep the system under control. It is important that the implementation of a LPPS be considered in the context of the need to also ensure the integrity of the upstream private sewers.

 

Another aspect of the LPPS that requires discussion is the cost.  In the June 2008 report the costs to fit LPPS to catchments 4002 and 4003a only, and alternatively, retrofit to catchments 4002, 4003a, 4003b and 4001 were broadly estimated to be:

 

Project Element

Cost 4002 & 4003a

Cost 4002; 4003a; 4003b; 4001

Supply and Install Low Pressure System

$2,900,000

$12,750,000

Project Initiation and Planning Costs

$200,000

$200,000

Project Management

$250,000

$400,000

NPV Saving on Pump Station Operation

$300,000

$300,000

Contingency

$500,000

$500,000

Current Work on 4001 and 4003b gravity system

$200,000

 

 

 

 

Total Project Costs Low Pressure Pump System

$4,350,000

$14,150,000

 

Implementation of an expanded LPPS will also involve unquantified costs such as installing LPPS units in the confined central business district; redesigning pump station 4006 to allow discharge into pump station 4001/4000 and not into the extremity of 4001 gravity system as it currently does.

 

The retrofitting of a Low Pressure Pumping System (LPPS) to the Mullumbimby sewerage reticulation system would have a high capital cost and will not eliminate stormwater inflow and infiltration because defects in the upstream private sewers will continue to be a problem and source of stormwater ingress. For these reasons and given the capacity of the BASAS, implementation of a LPPS is not recommended.

 

       5.2 Gravity Sewerage System Maintenance

 

The current project has decreased inflows into the system to a level that, once pump station 4000 is operational, there will be no direct overflows into the Brunswick River for any storm event less than a 1 in 20 year ARI and probably even greater.  The current gravity system repair work is continuing and is expected to be largely completed by 2010.  It is expected this work will reduce storm water inflow into the sewerage system even further.  Thereafter it will be necessary to continue with maintenance of the system in conjunction with normal operational activities.  This will keep stormwater ingress into the sewerage system to a manageable level.

 

Once pump station 4000 is operational the system will have sufficient capacity to pump all flows to the treatment plant for the design life of the plant.  Once the treatment facility is commissioned, the facility will have capacity to treat up to 22.04 ML per day.

 

As stated in Section 2 above, the Mullumbimby sewer system will therefore be in a manageable state with no overflows occurring.

 

There is some conjecture that the treatment capacity will be compromised at some future date.  The June 2008 annual review projected this date would be 2017 if flows could not be reduced below 14 times ADWF in Mullumbimby.  The flows currently are at 12.4 times and falling, therefore this projection could be extended to 2020 or beyond.

 

There is significant capacity in the BASAS but it is also possible to provide further  contingency and ensure all flows to the STP are treated to licence quality by constructing additional emergency storage at the new Vallances road treatment facility.  This could be achieved by constructing the already scoped BASAS project elements of constructed wetlands and the effluent storage dam.  These elements have a combined storage capacity of 135 ML and would provide enormous flexibility to the system including enhancement of reuse capacity; and capture and treatment of storm flows.

 

The effluent storage dam could be used to store treated effluent in the dry months for use in reuse schemes; and lowered/ emptied in the wet months for the contingency use of capturing excess storm flows which could then be recycled through the plant for treatment.  The effluent storage dam capacity is 55 ML.

 

The wetlands were designed as three cells covering 10 hectares with an operating depth up to 800mm.  This gives a maximum storage capacity of 80 ML.  The major storm events and the associated flows that would need to be bypassed would be highly diluted with stormwater.  It is possible the wetlands could further treat these flows without using the STP biological processes.

 

The effluent storage dam and the wetlands were part of the original approved project scope and are already partially designed.  They were excluded from the project scope due to financial constraints.  The total cost is estimated to be $4.5 million – similar to the limited Low Pressure Pump System (catchments 4002 and 4003b) and less than half the cost of the full Low Pressure Pump System (catchments 4001; 4002; 4003a and b).

 

This configuration would have very little risk in performing to operating licence requirements and providing sufficient contingency to capture any future unforeseen excess flows for subsequent treatment. Further investigation of this option is recommended.

 

       5.3 Recommendations

 

The most practical approach to the project is to complete the work in 4001 and 4003b; continue with inspection of private assets; implement routine investigation and repairs for both public and private infrastructure in normal operational and maintenance activities; and investigate further the implementation of the effluent storage dam and the constructed wetlands at the Vallances road site as storm flow storages and/or treatment.  This configuration will:

 

§ Cost less than a full LPPS system

§ Have no untreated overflows to the Brunswick River for the design life of the BASAS for any event less than a 1 in 20 year ARI and possibly more under normal operating conditions

 

This configuration with additional storage capacity has the following advantages:

 

§ It is already part of the approved BASAS scheme

§ Provides increased reuse capacity

§ Provides increased environmental outcomes in wetland operation

§ Provides increased effluent polishing with the wetlands

§ Design documents already exist and the project could be considered “shovel ready”.

 

Ongoing maintenance of the existing gravity sewerage system with the potential implementation of the effluent storage dam and constructed wetlands at the Vallances road site would further increase system storage capacity and improve integrated effluent management outcomes. It would also provide sustainable benefits to the community and the environment and will further enhance the award winning Brunswick Area Sewage Augmentation Scheme.

 

 


BYRON SHIRE COUNCIL

Staff Reports - Infrastructure Services                                                                               5.2 - Attachment 1

APPENDIX 1

Flow Data

DATE

STP INFLOW (KL)

RAINFALL (mm)

MILL ST OVERFLOW  (KL)

PALM PARK OVERFLOW (KL)

Total Flow (KL)

RATIO PWWF / ADWF

Ratio>12

Ratio>9

Ratio>7

KPI 60mm

KPI 85mm

27/04/2005

1005

17

 

 

1005

1.1

0

0

0

0

0

28/04/2005

1960

18.5

 

 

1960

2.1

0

0

0

0

0

5/05/2005

1751

26

 

 

1751

1.8

0

0

0

0

0

6/05/2005

2854

10

 

 

2854

3.0

0

0

0

0

0

7/05/2005

1586

6.5

 

 

1586

1.7

0

0

0

0

0

8/05/2005

2016

18

 

 

2016

2.1

0

0

0

0

0

9/05/2005

5393

30.5

 

 

5393

5.7

0

0

0

0

0

13/05/2005

2830

7.5

 

 

2830

3.0

0

0

0

0

0

21/05/2005

1423

16

 

 

1423

1.5

0

0

0

0

0

7/06/2005

980

5

 

 

980

1.0

0

0

0

0

0

8/06/2005

962

6.5

 

 

962

1.0

0

0

0

0

0

9/06/2005

1233

3

 

 

1233

1.3

0

0

0

0

0

15/06/2005

635

8

 

 

635

0.7

0

0

0

0

0

27/06/2005

1303

15.5

 

 

1303

1.4

0

0

0

0

0

28/06/2005

4121

52

 

 

4121

4.3

0

0

0

0

0

29/06/2005

7898

137.5

3000

 

10898

11.4

0

1

1

0

0

30/06/2005

9843

268.5

3000

 

12843

13.5

1

1

1

1/07/2005

8119

133.5

3000

 

11119

11.7

0

1

1

2/07/2005

6566

2

3000

 

9566

10.0

0

1

1

20/07/2005

1440

18.5

 

 

1440

1.5

0

0

0

0

0

21/07/2005

1923

9.5

 

 

1923

2.0

0

0

0

0

0

22/07/2005

1950

3

 

 

1950

2.0

0

0

0

0

0

13/08/2005

858

3

 

 

858

0.9

0

0

0

0

0

14/08/2005

1101

10

 

 

1101

1.2

0

0

0

0

0

28/08/2005

844

4

 

 

844

0.9

0

0

0

0

0

29/08/2005

747

7

 

 

747

0.8

0

0

0

0

0

30/08/2005

930

8.5

 

 

930

1.0

0

0

0

0

0

5/09/2005

880

5

 

 

880

0.9

0

0

0

0

0

17/09/2005

989

9.5

 

 

989

1.0

0

0

0

0

0

28/09/2005

791

5

 

 

791

0.8

0

0

0

0

0

16/10/2005

727

7.5

 

 

727

0.8

0

0

0

0

0

20/10/2005

602

3

 

 

602

0.6

0

0

0

0

0

21/10/2005

633

8

 

 

633

0.7

0

0

0

0

0

22/10/2005

1123

20

 

 

1123

1.2

0

0

0

0

0

25/10/2005

1334

27

 

 

1334

1.4

0

0

0

0

0

28/10/2005

1641

27

 

 

1641

1.7

0

0

0

0

0

2/11/2005

814

3

 

 

814

0.9

0

0

0

0

0

6/11/2005

823

5

 

 

823

0.9

0

0

0

0

0

7/11/2005

870

5

 

 

870

0.9

0

0

0

0

0

18/11/2005

768

7

 

 

768

0.8

0

0

0

0

0

24/11/2005

1520

23

 

 

1520

1.6

0

0

0

0

0

25/11/2005

2471

52

 

 

2471

2.6

0

0

0

0

0

26/11/2005

5193

11

 

 

5193

5.4

0

0

0

0

0

28/11/2005

3926

22

 

 

3926

4.1

0

0

0

0

0

29/11/2005

3926

22

 

 

3926

4.1

0

0

0

0

0

2/12/2005

1709

10

 

 

1709

1.8

0

0

0

0

0

3/12/2005

1763

5

 

 

1763

1.8

0

0

0

0

0

4/12/2005

4114

31

 

 

4114

4.3

0

0

0

0

0

9/12/2005

2446

20

 

 

2446

2.6

0

0

0

0

0

14/12/2005

1044

4

 

 

1044

1.1

0

0

0

0

0

17/12/2005

1909

31

 

 

1909

2.0

0

0

0

0

0

4/01/2006

877

14

 

 

877

0.9

0

0

0

0

0

6/01/2006

2040

45

 

 

2040

2.1

0

0

0

0

0

7/01/2006

2287

9

 

 

2287

2.4

0

0

0

0

0

8/01/2006

2024

14

 

 

2024

2.1

0

0

0

0

0

9/01/2006

4448

39.5

 

 

4448

4.7

0

0

0

0

0

10/01/2006

5938

33

 

 

5938

6.2

0

0

0

0

0

11/01/2006

6059

10

 

 

6059

6.4

0

0

0

0

0

19/01/2006

3778

220

393

 

4171

4.4

0

0

0

0

1

20/01/2006

9253

115

3557

1196

14006

14.7

1

1

1

21/01/2006

8777

78

3024

442

12243

12.8

1

1

1

22/01/2006

7024

0

2390

 

9414

9.9

0

1

1

5/02/2006

1386

23.5

 

 

1386

1.5

0

0

0

0

0

13/02/2006

2818

33

 

 

2818

3.0

0

0

0

0

0

16/02/2006

4222

36

20

 

4242

4.5

0

0

0

1

1

23/02/2006

1226

12

 

 

1226

1.3

0

0

0

0

0

25/02/2006

1481

12

 

 

1481

1.6

0

0

0

0

0

26/02/2006

1260

4

 

 

1260

1.3

0

0

0

0

0

28/02/2006

3416

38

 

 

3416

3.6

0

0

0

0

0

1/03/2006

2951

3

 

 

2951

3.1

0

0

0

0

0

3/03/2006

2985

18

 

 

2985

3.1

0

0

0

0

0

4/03/2006

6928

107

 

 

6928

7.3

0

0

1

0

0

5/03/2006

7986

38

 

 

7986

8.4

0

0

1

0

0

6/03/2006

10059

75

 

 

10059

10.6

0

1

1

0

0

23/03/2006

1283

15

 

 

1283

1.3

0

0

0

0

0

24/03/2006

3569

39

 

 

3569

3.7

0

0

0

0

0

25/03/2006

4439

22

 

 

4439

4.7

0

0

0

0

0

26/03/2006

3120

5

 

 

3120

3.3

0

0

0

0

0

1/04/2006

1788

13

 

 

1788

1.9

0

0

0

0

0

5/04/2006

1696

25

 

 

1696

1.8

0

0

0

0

0

6/04/2006

4049

20

 

 

4049

4.2

0

0

0

0

0

16/04/2006

2361

78

832

 

3193

3.4

0

0

0

0

1

17/04/2006

7964

31

 

 

7964

8.4

0

0

1

0

0

 

 

 

 

 

 

 

 

 

 

 

 

23/03/1900

 

2433

22216

1638

Total 2006

 

3

8

11

1

4

 

 

 

 

 

 

 

 

 

 

 

 

1/05/2006

1355

10

 

 

1355

1.4

0

0

0

0

0

16/05/2006

2930

33

 

 

2930

3.1

0

0

0

0

0

17/05/2006

1277

3.5

 

 

1277

1.3

0

0

0

0

0

11/06/2006

1090

13.5

 

 

1090

1.1

0

0

0

0

0

14/06/2006

934

4

 

 

934

1.0

0

0

0

0

0

18/06/2006

1092

16

 

 

1092

1.1

0

0

0

0

0

19/06/2006

1074

4

 

 

1074

1.1

0

0

0

0

0

20/06/2006

1093

5

 

 

1093

1.1

0

0

0

0

0

21/06/2006

4796

46

 

 

4796

5.0

0

0

0

0

0

22/06/2006

5585

15

 

 

5585

5.9

0

0

0

0

0

23/06/2006

4595

24

 

 

4595

4.8

0

0

0

0

0

24/06/2006

6496

15

 

 

6496

6.8

0

0

0

0

0

25/06/2006

6369

17

 

 

6369

6.7

0

0

0

0

0

30/06/2006

1504

4

 

 

1504

1.6

0

0

0

0

0

5/07/2006

1399

7

 

 

1399

1.5

0

0

0

0

0

15/07/2006

999

4

 

 

999

1.0

0

0

0

0

0

16/07/2006

1105

8

 

 

1105

1.2

0

0

0

0

0

22/07/2006

942

13

 

 

942

1.0

0

0

0

0

0

25/07/2006

1188

8

 

 

1188

1.2

0

0

0

0

0

26/07/2006

2750

16

 

 

2750

2.9

0

0

0

0

0

28/07/2006

1755

9

 

 

1755

1.8

0

0

0

0

0

29/07/2006

4894

25

 

 

4894

5.1

0

0

0

0

0

6/08/2006

1233

5.5

 

 

1233

1.3

0

0

0

0

0

28/08/2006

925

7

 

 

925

1.0

0

0

0

0

0

29/08/2006

1395

19

 

 

1395

1.5

0

0

0

0

0

30/08/2006

5219

67

 

 

5219

5.5

0

0

0

0

0

31/08/2006

6729

38

 

 

6729

7.1

0

0

1

0

0

1/09/2006

6276

14

 

 

6276

6.6

0

0

0

0

0

2/09/2006

4389

7.5

 

 

4389

4.6

0

0

0

0

0

5/09/2006

1951

10.5

 

 

1951

2.0

0

0

0

0

0

11/09/2006

2543

25

 

 

2543

2.7

0

0

0

0

0

12/09/2006

2666

11

 

 

2666

2.8

0

0

0

0

0

13/09/2006

3304

10

 

 

3304

3.5

0

0

0

0

0

28/09/2006

2256

24

 

 

2256

2.4

0

0

0

0

0

17/10/2006

766

11

 

 

766

0.8

0

0

0

0

0

22/10/2006

724

4.5

 

 

724

0.8

0

0

0

0

0

30/10/2006

932

4

 

 

932

1.0

0

0

0

0

0

5/11/2006

1381

23.5

 

 

1381

1.4

0

0

0

0

0

9/11/2006

1455

27.5

 

 

1455

1.5

0

0

0

0

0

10/11/2006

3394

25.5

 

 

3394

3.6

0

0

0

0

0

28/11/2006

610

3.5

 

 

610

0.6

0

0

0

0

0

30/11/2006

935

10

 

 

935

1.0

0

0

0

0

0

4/12/2006

1125

17.5

 

 

1125

1.2

0

0

0

0

0

16/12/2006

849

6

 

 

849

0.9

0

0

0

0

0

17/12/2006

1145

21.5

 

 

1145

1.2

0

0

0

0

0

22/12/2006

1061

10

 

 

1061

1.1

0

0

0

0

0

27/12/2006

814

4

 

 

814

0.9

0

0

0

0

0

3/01/2007

1029

15

 

 

1029

1.1

0

0

0

0

0

4/01/2007

1105

9.5

 

 

1105

1.2

0

0

0

0

0

5/01/2007

1594

19

 

 

1594

1.7

0

0

0

0

0

6/01/2007

1879

17

 

 

1879

2.0

0

0

0

0

0

9/01/2007

1416

17.5

 

 

1416

1.5

0

0

0

0

0

26/01/2007

875

16

 

 

875

0.9

0

0

0

0

0

27/01/2007

828

4

 

 

828

0.9

0

0

0

0

0

12/02/2007

871

9.5

 

 

871

0.9

0

0

0

0

0

13/02/2007

2758

58

 

 

2758

2.9

0

0

0

0

0

14/02/2007

2663

10

 

 

2663

2.8

0

0

0

0

0

15/02/2007

1339

5

 

 

1339

1.4

0

0

0

0

0

18/02/2007

892

4

 

 

892

0.9

0

0

0

0

0

19/02/2007

887

3

 

 

887

0.9

0

0

0

0

0

21/02/2007

824

6

 

 

824

0.9

0

0

0

0

0

22/02/2007

903

3

 

 

903

0.9

0

0

0

0

0

23/02/2007

860

10

 

 

860

0.9

0

0

0

0

0

24/02/2007

957

3

 

 

957

1.0

0

0

0

0

0

1/03/2007

829

3.5

 

 

829

0.9

0

0

0

0

0

2/03/2007

779

4

 

 

779

0.8

0

0

0

0

0

6/03/2007

744

4

 

 

744

0.8

0

0

0

0

0

7/03/2007

1335

18.5

 

 

1335

1.4

0

0

0

0

0

8/03/2007

1005

7

 

 

1005

1.1

0

0

0

0

0

9/03/2007

2205

25

 

 

2205

2.3

0

0

0

0

0

10/03/2007

1238

4

 

 

1238

1.3

0

0

0

0

0

14/03/2007

926

8

 

 

926

1.0

0

0

0

0

0

26/03/2007

944

8

 

 

944

1.0

0

0

0

0

0

5/04/2007

860

4

 

 

860

0.9

0

0

0

0

0

6/04/2007

887

8

 

 

887

0.9

0

0

0

0

0

7/04/2007

814

11

 

 

814

0.9

0

0

0

0

0

8/04/2007

1013

5.5

 

 

1013

1.1

0

0

0

0

0

9/04/2007

1391

20

 

 

1391

1.5

0

0

0

0

0

10/04/2007

1639

18

 

 

1639

1.7

0