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EVANDALE WASTEWATER TREATMENT PLANT 2008 PROPOSED PLANT UPGRADE WORKS 13 th March 2008

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Page 1: EVANDALE WASTEWATER TREATMENT PLANT - EPA …epa.tas.gov.au/documents/northern_midlands_council_evandale_wwtp... · Evandale Wastewater Treatment Plant ... It is noted that the prime

EVANDALE WASTEWATER TREATMENT PLANT

2008 PROPOSED PLANT UPGRADE WORKS

13th March 2008

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Evandale WWTP – Proposed 2008 Plant Upgrade – March 2008

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Evandale Wastewater Treatment Plant

2008 Proposed Plant Upgrade Content 1.0 Background 3 2.0 Proposed Development 3 3.0 Key Issues

3.1 Physical Description of Site 5 3.2 Access to Site 8 3.3 WWTP Design. 8 3.4 Environmental 9

4.0 Reports and Correspondence 11 5.0 Timeline 12

6.0 Appendices 12

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1.0 Background The Evandale WWTP has for some time not totally performed within limitations imposed by EPN 481/1 (refer Appendix ‘Influent test results October 2007’). Northern Midlands Council (NMC) has determined to address the situation and to undertake necessary actions to improve plant performance and ensure sustainable operation and maintenance regimes are in place. Several reports have been prepared over a period of time and are listed in the reference documents. The latest annual report on the Evandale WWTP by Consultants CEE Pty Ltd (July 2007) is attached as appendix ‘2007 Evandale Annual Report (CEE Consulting)’. This report shows that:

the plant is operating at about two-thirds of its design capacity, that the sewerage is essentially of a domestic nature, that there has been little growth in services for several years and little

likelihood of growth in the near future. It is noted that the prime method of disposal of effluent is to land. In 2007 all WWTP effluent was applied to land and no discharge to Boyes Creek occurred. Whilst this has meant that further treatment of effluent has occurred at the site storage dam, and that no apparent environmental effects have been observed in the short term because of the dry year, it is essential that the long term compliance problems at the WWTP be addressed. Previous reports have determined that earlier failure to promptly and/or adequately desludge the single primary lagoon, together with some specific operational issues, are the major immediate problems facing the WWTP. In response, NMC has allocated funds for the upgrade of the Evandale WWTP by the immediate provision of an additional primary lagoon and changes to pipe works allowing maximum flexibility of operations and “paralleling” of treatment streams which will in turn enable routine desludging, maintenance and refurbishment of each lagoon as required. In the longer term, the desirability of providing increased on site storage of effluent has been identified and the provision for such storage (land acquisition, design, etc.) through a tertiary lagoon will be made at this time. 2.0 Proposed Development NMC owns and operates the Evandale WWTP. The WWTP treats wastewater from the township of Evandale and discharges to an Effluent Reuse Dam on the property “Andora” or when flow cannot be stored there, directly to Boyes Creek. The Proposed Development is broken down into the following components and for ease of identification these are listed in process order:

1) Reconstruction of inlet pipelines and structures to address existing problems

with the location of the inlet works (including potential for blockages), to

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provide for a second primary lagoon and to enable necessary operational flexibility.

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2) Provision of a second primary lagoon to enable flow to be “split” between two

parallel lagoon trains of one primary and one secondary lagoon, with a total of four lagoons.

3) Alterations to the existing primary and secondary lagoons, including the replacement of the failed baffle, to reflect provision of the second (new) primary lagoon

4) Provision of internal pipework between lagoons allowing maximum flexibility of operations.

5) Provision of new outlet pipelines (to existing reuse pumping station and existing outfall) and peripheral works as required.

6) Provision for alterations to the effluent reuse transfer pump to meet any identified future requirements.

7) Provision for future “on site” tertiary storage to enhance effluent reuse opportunities, and cater for future growth.

8) Ancillary works required such as drainage, fencing, access, etc. 9) Completion of a revised Operations Manual and Management Plan reflecting

the upgraded WWTP and the actions that Council must undertake to meet the conditions of Environment Protection Notice [EPN] 481/1 issued in January 2003 by DPIWE.

Sketch Plan 6 (page 4) shows possible locations of the proposed new lagoons at the WWTP. Details of the location of the WWTP, the area served and key items of proposed works are attached as an appendix. General Planning Approval from Council will be required. 3.0 Key Issues Identified 3.1 Physical Environment of Site The Evandale WWTP is built on the Boyes Creek floodplain which flows into the South Esk River. The area is undulating, within the Launceston Tertiary Basin, has an overall annual rainfall of some 600-750 mm with the underlying geology being a mix of alluvial gravels, sands and till with outcrops of igneous and volcanic rock. The area adjacent and surrounding the WWTP is under agricultural use, with the nearest residential area in excess of 700m away. The 2007 WWTP Annual Report indicated no complaints regarding the WWTP. Access to the site is off Logan Road via a 3.0m wide gravelled access road. The site is secured with a locked gate at the single access point.

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View of Access Road Looking towards Logan Road The area identified for the new Primary Lagoon is highly disturbed from earlier construction activity and the stockpiling of excess material. This area is also transversed by natural and urban stormwater drainage from the Logan Road area, which naturally falls to outfall at Boyes Creek.

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View showing stockpiled excess excavation and drainage channel where proposed new primary lagoon to be located View showing stockpiled material on site of proposed primary lagoon The area identified for the long term new tertiary lagoon storage is currently primarily used for agricultural purposes. The loss of this small area of agricultural activity is not considered to be significant in agricultural terms (see Sketch Plan 1).

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3.2 WWTP Design The existing load on the WWTP is approximately two thirds of its design capacity. In previous reviews of the plant performance, issues regarding questions of maintenance and suitability of inlet controls have arisen. It has been concluded that the operational performance of the plant is compromised by the single primary lagoon further compromised by a failed internal lagoon wall; the resultant failure to desludge and maintain the single primary lagoon over several years has lead to plant performance failures. Recorded sludge levels show from 300mm to 600mm of sludge in the primary and secondary lagoons. For an operational depth of 1100mm to 1200mm this represents an effective decrease in available depth of 25% to 55%. Not only will the effective decrease in depth adversely affect lagoon performance, the anaerobic sludge layer will cause its own specific adverse affects. View showing failed baffle between existing primary and secondary lagoon

The solution to such operational problems in lagoon systems is to provide primary lagoon capacity by use of multiple lagoons rather than a single lagoon, and having “spare” lagoon capacity thereby allowing the provision of adequate treatment capacity whilst providing for necessary refurbishment and maintenance of the plant. At Evandale, the existing site can accommodate the ready provision of additional primary lagoon capacity to enable resolution of the operational problems currently

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giving rise to compliance problems. NMC will be engaging a qualified and competent engineering consultant to undertake all aspects of the detailed design. 3.3 Access to Project Site The site of the project partially lies within land owned by NMC and land owned by the adjacent landowner. NMC has undertaken discussions with the adjacent landowner regarding this project. An “in principle” agreement has been reached regarding the project; acquisition of the required land will be undertaken once the final footprint of the new lagoons and any other ancillary works required is finalised. 3.4 Environmental Flora & Fauna Flora and fauna of the site are largely modified. View showing construction material and drainage line through site of proposed primary lagoon The immediate construction area of the proposed new Primary lagoon has already been subjected to construction activity. Material storage, drains and excavation have been undertaken across most of the site with the balance of the area being subjected to agricultural use.

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Views showing extent of existing site disturbance and farmland at proposed primary lagoon site

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The area of construction for the longer term proposed new Tertiary lagoon has been subjected to long term farming activity. Other areas of construction activity will be undertaken within areas already disturbed by previous construction activity. Water Quality The proposed construction will have no additional adverse effects on water quality in the Boyes Creek and South Esk River. Effluent from the WWTP will continued to be discharged to land reuse on the “Andora” property, and the additional storage as planned will further reduce any potential for effluent disposal to the existing outfall during wet years. Overall, the proposals will address short term operational problems with the WWTP and improved long term storage capacity which will have the effect of an overall reduction in the nutrient and contaminant load from the WWTP to surface waterways and therefore will lead to an overall improvement in water quality in the catchment. Air & Noise Pollution An increase in air & noise pollution is likely to occur during the construction phase of the project. Sources for this increase will be the associated construction activity and equipment emissions. As the adjacent area is rural, the likely impact is considered to be low. The nearest residents will be individually advised of the commencement of construction together with communication lines for complaints. Works will be restricted to normal hours for building construction applicable within the NMC area, Culture No site specific survey for aboriginal sites has been undertaken at this point in time. In general terms the area has been significantly changed by earlier construction activity and farming activities. It is proposed that once preliminary design works have been commenced and a final footprint has been determined for the new lagoons, a detailed site survey will be undertaken by qualified persons before finalization of designs. 4.0 Reports & Correspondence The following reports have been accessed in forming this Notice of Intent.

• Evandale Wastewater System....2007 Annual Report....CEE Consultants (July 2007)

• Evandale WWTP Operations Manual.....NMC (September 2007)

• Evandale WWTP Review and Annual Report.....GHD (July 2006)

• NMC Wastewater Treatment Plants (NMC02)... AusEngineers (August 2006)

• Evandale Sewage Treatment Plant......LPH (Tas) P/L (1994) Additionally, there is a body of correspondence and test results between the NMC and DTAE which indicate the need for the issues regarding the Evandale WWTP performance to be addressed. This correspondence has been part of the consideration for this NOI. 5.0 Project Timeframe

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Having identified the overall problems and solutions, NMC has allocated funding for the immediate construction of the new primary lagoon, lagoon modifications and ancillary works. NMC intends to proceed with the project as soon as approvals are in place and designs completed and tendered. 6.0 Appendices:

a) Sketch Plans #1.....Evandale WWTP Plan Showing WWTP & Reuse Dam and Surrounding Farm. #2.....Evandale WWTP Plan of WWTP and Sewerage Scheme #3.....Evandale WWTP Plan of Existing Layout. #4.....Evandale WWTP Proposed Additional Lagoon(s) and Surrounding Farmland. #5.....Evandale WWTP Plan of 1994 Upgrade #6.....Evandale WWTP Plan of Proposed Additional Lagoons #7.....Evandale WWTP Plan Showing Required External & Internal Wall Heights. #8.....Evandale WWTP Plan Showing need for Multiple Cross Connections #9.....Evandale WWTP Plan Showing Stormwater Disposal #10...Evandale WWTP Plan Showing Proposed Inlet and Outlet Works Redesign. #11...Evandale WWTP Plan Highlighting Reuse Pump Station Review. #12...Evandale WWTP Plan Showing Proposed Redesign of Baffle Wall

b) Reports

2007 Evandale Annual Report (CEE Consulting). Influent Tests, Evandale WWTP (October 2007)

c) Photos • To be Provided as Required