Title: Timaru’s District Wide Sewer Strategy
Author: Ashley Harper, Timaru District Council
Abstract: Timaru’s District Wide Sewer Strategy
Key Words: Wastewater Strategy, Working Party, Community, Oxidation Ponds, Wetlands, Trunk Sewers, Tunnels
Introduction The Timaru District has four main urban areas, namely Timaru, and the inland towns of Geraldine, Pleasant Point and Temuka, with each of these areas having a traditional piped sewer network. The total population served within these urban areas is 40,000.
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Since 1987 Timaru’s wastewater had been treated via a 0.5 milliscreening plant and associated ocean outfall, while each of the three inland towns utilised oxidation ponds and river discharge as the wastewater treatment and disposal process.
In 1996 the Timaru District Council initiated a review of the respective wastewater treatment and disposal strategies, primarily because of emerging environmental and regulatory issues. Council supported a community based approach to identifying a preferred strategy, noting that the strategy needed to be robust and viable and to recognise the unique nature of the Timaru District’s effluent. Compliance with proposed environmental standards was a non negotiable requirement.
Wastewater Working Party The community based approach involved the appointment of an experienced facilitator (Gay Pavelka) and the formation of a Wastewater Working Party in 1997. Membership of the working party was made up of representatives of the following organisations:
Timaru District Council Community Boards Federated Farmers Chamber of Commerce Industrial Dischargers Royal Forest and Bird Society Central South Island Fish & Game Council Tangata Whenua National Council of Women Crown Public Health
Invited observers represented:
Environment Canterbury Department of Conservation/Aoraki Conservation Board Timaru District Council Planning Unit
The Wastewater Working Party were supported by Timaru District Council engineering and asset management staff and by specialist consultants such as Beca, Pattle Delamore and Mitchel Partnerships. Meetings were held approximately every six weeks, usually at the end of the normal working day and site visits to existing treatment sites in the Timaru District and in neighbouring districts were made.
Consultation Objectives The consultation objectives were wide ranging and specifically covered the following issues:
To include Runanga in the decision making process in accordance with the roles prescribed in the RMA. To ensure that the community’s spectrum of views was included in fairly held discussion about wastewater issues and options. To ensure all the wastewater issues that affect the community were identified and understood, sound information was available and a range of options were evaluated objectively. That the desired outcome was a consensus recommendation to the TDC from the range of interests in the Community.
#:872456 Te Runanga O Arowhenua chose to join the WWP in addition to holding several consultation hui. Meetings also took place between TDC representatives, Te Runanga O Arowhenua (Resource Management Committee) and Te Runanga O Ngai Tahu, on a number of occasions.
A Summary of Understanding was reached between Timaru District Council, Te Runanga O Arowhenua Trust and Te Runanga O Ngai Tahu on 13 October 1999. The intention was to confirm how land disposal can remain a future option for disposing of treated wastewater (given that an ocean outfall is currently seen as the likely best practicable option).
Consultation Details Between 1997 and 2000 TDC also maintained an 0800 number for people to use, published a number of articles in the “Timaru Herald”, “High Country Herald” and “Temuka Leader”, and sent regular newsletters to residents near the proposed treatment plant on Aorangi Road and adjacent to the Inland Towns pipeline route.
To facilitate further feedback, thirty thousand pamphlets with a questionnaire were delivered to all households in the Timaru District and 1041 questionnaires were returned by September 1999. Results indicated around 80% support for the proposed wastewater management option.
Following preparation of the draft 2002 AEE, several meetings were held with residents living near to the Waste Water Treatment Plant on Aorangi and Meadows Roads.
Representatives from TDC and Beca again met with residents from Aorangi and Meadows Roads in December 2006. The meeting was facilitated by Gay Pavelka who was also involved in the Wastewater Working Party process.
The consultation process described above achieved the following:
Agreement on community goals and standards any wastewater system must satisfy. Confirmation of the issues to be addressed. A range of wastewater management options to consider. Agreement on the wastewater system to recommend to TDC (and subsequently TDC acceptance of this recommendation). A proposed trade waste strategy aimed at giving industry certainty and the broader community a higher standard of treated trade wastewater. Interest from WWP members in continuing discussion with TDC, when other community issues are being addressed.
Community Consultation on the Timaru Wastewater Management Strategy continues on an ‘as required’ basis. Liaison meetings are held with the major industrial discharger group to discuss implications of industrial wastewater treatment proposals and the trade waste charging framework. Discussions with individual industries are also on-going on the specific details of each industrial discharge including potential growth and on-site treatment options.
Regulatory Environment The emerging regulatory environment in 1998 included the Canterbury Regional Council proposed Opihi River Regional Plan (ORRP) and the Minister of Conservation proposed National Coastal Policy Statement (NCPS). The ORRP would prohibit the discharge, either directly or indirectly, of human waste to natural waterways. This would therefore apply to the Pleasant Point and Temuka oxidation pond discharges and would likely also apply to the Geraldine oxidations pond discharge. The NCPS would exclude the disposal of treated human effluent to the ocean unless it has passed through or via land.
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Timaru District Wastewater Characteristics – Flow and Loadings The Timaru urban wastewater stream is unique in that it has a 40:60 volume ratio between domestic and commercial/industrial wastewater and an approximate 10:90 strength ratio.
The main contributing industries connected to the Timaru urban sewer network are:
Meat Processing Fish Processing Vegetable Processing Brewing Pelts Processing Wools Scouring Rendering
Most of these industries are located in the Washdyke and Port areas. The existing wastewater milliscreening plant is located just North of Washdyke. The three inland towns have reasonably standard domestic wastewater characteristics with all urban areas experiencing the addition of significant amounts of rainwater during and after rain events.
#:872456 Location of WWTP and Outfall
Technical Studies and Reports A review by Beca was undertaken which confirmed the strategy of separating the Timaru domestic and industrial flows and identified technically feasible treatment options that would achieve the performance standards that will likely be required for continued discharge through the Timaru ocean outfall.
The review prepared initial cost estimates for each of a number of different treatment options. The cost estimates for the preferred option were updated to 2008 costs before a final binding decision was made.
A beach-user survey was carried out in 2009. The reconvened Wastewater Liaison Group considered a draft AEE and limited further public consultation was carried out.
Field investigations and consultation on the effects of the ocean outfall were carried out, prior to the submission of an ocean outfall renewal consent application. This application was submitted 10 months before the application would need to be submitted, in order to continue discharging after the consent expiry date of December 2010.
Immediately South of Temuka, located between the Opihi and the Temuka Rivers is the small rural settlement of Arowhenua. Within this settlement are historic wastewater disposal issues.
The Water Services Sanitary Assessment on the Arowhenua community identified that no Council wastewater systems serviced the Arowhenua community, and that a very strong community preference to increase the level of service existed. There were a number of on- site wastewater system failures, notably the school and the marae.
A number of preliminary options were investigated by TDC in 2005. All property owners in the area were contacted and provided with an information pack and a public meeting was
#:872456 held in April 2006. Following this meeting a Working Party was established consisting of representatives from Timaru District Council, Te Puni Kokiri, Te Runanga O Arowhenua and later Opus International Consultants.
The outcome of this sub strategy was that a local wastewater system was installed within the Arowhenua Community area. The system consists of a grinder pump at each house and pressure pipes to a centralised pump station. This main pump station then discharges to the Temuka oxidation ponds. There are currently 42 connections within the scheme.
Wastewater Treatment and Disposal Strategy The Wastewater Working Party was set up to provide community input to the development of this Strategy where the following strategies where recommended:
Upgrading of the Inland Towns Wastewater Treatment Plants (Oxidation Ponds). Conveyance of the treated Inland Towns wastewater to the Timaru marine outfall (initially direct to the ocean outfall, but ultimately via new Timaru maturation ponds/wetlands at Aorangi Road). Separation of Timaru industrial and domestic wastewater streams. Construction of new oxidation ponds, maturation ponds and wetlands for the Timaru domestic stream. Treatment of Timaru industrial wastewater in anaerobic lagoons (or equivalent) and possible UV disinfection (or equivalent). Continuing discharge of all Timaru and Inland Towns treated wastewater to the Pacific Ocean, via the existing submarine outfall.
This strategy was adopted by the Timaru District Council and has formed the basis for the work programme since 2000.
Consenting Resource consent applications and a notice of requirement for a designation were made in December 2006 for the construction, operation and maintenance of a wastewater treatment plant in Aorangi Road.
Public notification of the applications was made which drew nine submissions. A hearing of submissions was held in October 2007 and consents and designations were granted in December 2007.
Resource Consent applications were then made in 2010 for the discharge of treated effluent to the ocean via the existing ocean outfall, which had been constructed in 1986.
One objection was submitted by the Department of Conservation. There were 9 submissions in support, primarily from industrial trade waste dischargers.
The objection related to the duration of the consent and a solution was reached by negotiation. The agreed solution is that there will be a major review of the effectiveness of the treatment and disposal strategy after 12 years of operation.
Following a hearing in December 2010, ECan issued a 35 year consent with a raft of conditions. The most relevant being the effluent trigger value exceedence concept whereby there is a reporting and remedial programme required when the allowable trigger values exceed more than an allowable number of times in a 12 month period. The trigger values relate to BOD, suspended solids and fats/oils/greases.
#:872456 There is also a comprehensive regime of receiving environment monitoring which provides surety that the ocean discharge is compliant. This in turn drives oxidation pond performance and industrial dischargers on site treatment performance and compliance.
Treatment and Disposal Process The change in the treatment process is best illustrated with a diagram, showing the existing and the new, as from May 2014.
Existing Process Stream:
New Process Stream:
Strategy Work Streams and Budgets Improving the level of treatment at each of the three oxidation ponds serving the Inland Towns communities of Temuka, Geraldine and Pleasant Point, consisting of fitting aeration devices, influent screening and pond segmentation to provide maturation ponds and incorporating rock filters, was completed in 2002.
After extensive consultation with the public and key interest groups, the Inland Towns pipeline option of conveying treated wastewater from the Inland Towns to the Timaru marine outfall was constructed. It was commissioned in 2003.
The remaining stages all relate to the Timaru urban sewer network and the main Wastewater Treatment Plant in Aorangi Road. The construction programme was pragmatic and covered the 10 year period 2004-2014.
#:872456 Implementation The Wastewater Treatment and Disposal Strategy involved the following works:
Work Year Cost
1 Concept/Investigations/Consenting 1997-2001 $0.5m
2 Inland Towns Oxidation Ponds Upgrade 2002 $0.4m
3 Inland Towns Pipeline 2002-2003 $4.5m
4 Land Acquisition 2004-2007 $1.8m
5 New Trunk Sewer Central. Timaru to Aorangi Road
Stage 1 – Central Timaru to Virtue Avenue 2003-2004 $4.3m Stage 2 – Washdyke Lagoon Perimeter 2005-2006 $4.1m Stage 3 – Tunneling 2007-2009 $15.4m Stage 4 – Connecting Stage 1 to the Tunnels 2008-2009 $2.3m and the Tunnels to Stage 2 Stage 5 – Washdyke to Aorangi Road 2012-2013 $5.7m 6 Wastewater Treatment Upgrade Including 2012-2014 $19.1m Planting of Wetlands 7 Various Interconnecting Pipelines and 2009-2014 $2.4m Laterals 8 Wastewater Component Model Build & 2010-2014 $0.2m Dischargers Negotiation TOTAL 1997-2014 $60.7m
The above costs include professional services and construction work and exclude GST.
Trade Waste Component Model A key component of the wastewater treatment and disposal strategy is for industrial dischargers to primary treat their own wastewater.
The decentralised concept does generate a need for a site specific trade waste discharge agreement with all major trade waste dischargers.
BTO Limited were engaged to assist with the preparation of these agreements. In particular, BTO Limited have prepared a very comprehensive trade waste acceptance criteria model. The model is used to simulate, at a component level, the effects of combining the largest 14 trade waste discharge streams with the treated domestic wastewater.
Through the model trade waste discharge limits were set for each of flow, BOD, suspended solids and fats/oils/grease. For some dischargers it is possible to allow some components to exceed the TDC discharge consent limit. This individualised agreement process has won favour with all affected dischargers. The trade waste model is also used to determine the level of trade waste fees.
#:872456 Annual Costs The annual costs of the Wastewater Treatment and Disposal Strategy are primarily depreciation and interest charges. The actual variable operating costs of labour and electricity made up less than 10% of the annual cost.
Funding All costs associated with the provision of the Timaru sewer system are funded by the imposition of trade waste charges and the setting of a uniform annual sewer charge. This charge is levied on all toilet pans connected to the sewer network, with each dwelling deemed to be the equivalent of 1 pan. The uniform annual sewer charge is projected to peak in 2014/15 at $377 per annum including GST. The total projected recovery from rates will be $7m. Trade waste charges will recover $2.3m in 2014/15 and their ratio of 75%:25% is a best estimate of the costs of providing the sewer service to these two sectors of the Timaru District community.
Conclusion The promulgation of a comprehensive wastewater treatment and disposal strategy in the late 1990’s has been a catalyst for the implementation of a number of discrete projects that have resulted in improved environmental standards for the Timaru community.
The total spend of $60.7m has resulted in an increase in the uniform annual sewer charge to $377 per annum. Urban residents are very accepting of this charge, knowing that a long term strategy has been implemented as proposed more than 10 years ago.
Acknowledgments
My thanks go to my Chief Executive for supporting the writing of this paper and all the people involved in developing and implementing the Timaru District Wastewater Treatment and Disposal Strategy.
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