December 2017 Tamar Estuary
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Tamar Estuary River Health Action Plan 45 New combined rising main 26.8 Ti Tree Bend plant nutrient removal upgrade 10.0
The catchment actions will need to be implemented in partnership with a number of key organisations. It is expected that grazing and dairy action programs would be implemented by NRM North in partnership with Dairy Tasmania and the Tasmanian Farmers and Graziers Association. Past experience in on-ground investments indicates that a planned investment of $1 million per year is appropriate. It could be expected that finding farmers willing to undertake and co-fund investments may become progressively harder over time as the most able and willing are generally early adopters in any program. However this may be off-set to some extent by the momentum created by the relatively large scale of investment, with local landholders seeing the benefit of actions on neighbouring farms and the creation of new behavioural norms amongst local farming communities. The program will need to be flexible in terms of the approaches used to ensure ongoing adoption over time (for example the use of market based mechanisms or higher incentive rates for more difficult works may need to be considered). Works to address sewage intrusion into Launceston’s stormwater system would be led by Launceston City Council in partnership with TasWater as required. It is expected that these works would be undertaken over a 2 to 5 year period, depending on the scale of investment. With respect to the combined system investments, the upgrade to Ti Tree Bend and the West Launceston Diversion would be the most sensible projects to commence first. It is expected that these upgrades could be completed in a two year time frame, but clearly require TasWater’s involvement and agreement. The South Launceston Diversion is probably a more long term project given the upheaval it would likely require given its proposed route. This project may need three years to be undertaken. The offline storages and the new combined rising main from Margaret Street pump station could be completed in the period between Ti Tree Bend upgrade /West Launceston Diversion and the South Launceston Diversion.
Tamar Estuary River Health Action Plan 46 7.
Targets and monitoring 7.1
Reductions in concentrations in context A full analysis of the impact of daily (or even more frequent) estuary pathogen concentrations is not currently possible given the lack of past event monitoring for pathogens in the Estuary and limitations with the existing modelling available. It is, however, possible to model a time series of combined system overflow loads discharged to the Estuary using the data provided from the hydraulic model developed by the Combined System Working Group and which underpins the estimates of average annual load changes. Figure 16 shows the daily estimated enterococci loads from combined system overflows based on rainfall data from Distillery Creek over an eight year period. This figure shows a comparison of estimated loads based on actual rainfall versus estimated discharge loads in those rainfall events after implementing all recommended combined system projects.
This figure shows the very large expected decrease in enterococci loads overflowed for all events, ranging between 62 per cent and 93 per cent depending on the size of the rainfall event. The greatest relative decreases occur for low to medium rainfall events which are the most frequent events. Given that combined system overflows are known to be a major driver of enterococci concentrations in Tamar Estuary Zone 1, these results indicate that very large decreases in concentration could be expected on days with small to medium rainfall. Very large events will still produce large spikes in enterococci discharged to the estuary, but these events are significantly less frequent. Tamar Estuary River Health Action Plan 47 7.2
Targets
In the coming months it is the Taskforce’s intention to develop a set of targets in addition to the projected median concentration reductions for Zone 1, which convert these targets into expected reductions in the frequency of days where pathogen concentrations are above the primary contact threshold of 140cfu/100ml of enterococci. The Taskforce sees this as a tangible demonstration of the benefits of the concentration reduction in pathogens which will be more meaningful for communicating expected benefits of the investments to the community. In order to develop these targets, more event monitoring of pollutant concentrations in the days following rainfall as well as additional modelling is required. It is the intent of the Taskforce to produce a set of target before the end of June 2018. 7.3
Monitoring An evaluation framework should be developed against which activities undertaken by the body(ies) implementing the Taskforce’s recommendations can be assessed. This evaluation framework should follow the MERI principles (Monitoring, Evaluation, Reporting, Improvement), which have an adaptive management focus, allowing lessons learned through doing to be incorporated into future actions. This framework will require: More monitoring of water quality in the estuary and the freshwater system o
program. This monthly monitoring should be continued for all years. It should also be supplemented by event monitoring of some events in the estuary to allow better understanding of the estuary response to catchment and point source pollutant inputs to be developed. o
Very limited monitoring of water quality in freshwater parts of the catchment is currently undertaken. It is recommended that additional monitoring be undertaken at a minimum in the North Esk and Meander river catchments where catchment actions are expected to have the most significant benefits. o
(AUSRIVAS) methodology, or rank abundance sampling, to provide snapshots over time of the health of the TEER catchment’s freshwater system. Again, these could be focused on the Meander and North Esk river systems where catchment actions are being targeted.
Analysis of monitoring data and empirical modelling. Provision needs to be made for the analysis of monitoring data. There is no point in implementing greater monitoring regimes if there is not the dedicated resources to assess whether any of the benefits of actions can be observed and to allow the development of better understanding to refine management actions. This may include development or refinement of models that allow scenario testing or estimation of the benefits of management actions to date.
It is recommended that Tamar estuary report cards produced by the TEER continue to be released on a biennial or annual basis and incorporate the findings of the increased monitoring and analysis. Potentially occasional freshwater system report cards could also be produced using monitoring data discussed above.
Tamar Estuary River Health Action Plan 48 A State of the TEER report or similar should also be considered to provide a snapshot of progress in improving health of the estuary and freshwater systems. Annual ongoing funding to support this regime will be necessary. While TEER members already provide significant support to existing activities an ongoing budget is required to ensure consistent monitoring data is able to be collected and reporting and communications undertaken. It has been estimated that a budget of $250,000 per year would be required to facilitate the increased total program, with a proportion of this (around $100,000) currently met by in-kind contributions from TEER members and the State Government.
Tamar Estuary River Health Action Plan 49 8.
Funding and Financing of priorities 8.1
TasWater LSIP While the priority projects outlined for improving impacts of the combined system include projects potentially part of TasWater’s LSIP, it should be noted that the timing and funding of these projects are at the discretion of TasWater and its regulators. Under the current regulatory framework for the water and sewerage industry, TasWater is required to prepare a Price and Service Plan for three year “regulatory” periods, which need to gain the approval of the sectors technical regulators before funding is approved by the Economic Regulator. As LSIP is still at more a strategic level, it is not clear where the sewerage catchment diversion projects sit in the timing of LSIP works (noting they are only a minor part of LSIP), let alone the wider TasWater program. Indications from TasWater are that funding for the first stage of LSIP (specific projects still to be determined) will be sought in the 2021-24 regulatory period. The second stage of LSIP, which would nominally include the nutrient treatment upgrade at Ti Tree Bend, currently has a ten year time horizon. Should the projects need to be brought forward, agreement would likely need to be reached with TasWater (and potentially its regulators and customers) to make this happen and would also likely need some negotiation with TasWater for costs they would not otherwise incur. While TasWater are supportive of the projects identified, TasWater also note a number of factors that would influence its ability to deliver the proposed projects. These include the level of risk associated with the cost estimates for the LSIP components and any gap between funding allocated and delivery cost, the capacity of the market to deliver the projects in addition to TasWater’s program over the third price and service plan period and TasWater’s own internal resourcing and the level of involvement needed of it in delivering the projects. While the Taskforce has not sought to recommend measures to improve the ecological health of the Estuary outside of the upgrade of the Ti Tree Bend, it should be noted that TasWater’s LSIP Stage 1 has the potential to significantly reduce the effects of the seven wastewater treatment plants that discharge higher than desirable nutrient levels. In this respect, LSIP also represents a very important component to improving the ecological health of the Estuary. 8.2
Launceston City Council has indicated a willingness to provide funding towards the projects proposed for the combined system. At this stage, a dedicated amount has not yet been approved by Council, but any funds provided would be unconditional. 8.3
Department of Environment and Energy As part of the initial announcement of the City Deal, the Federal Government through the Department of Environment and Energy committed $500,000 per annum for three years towards the work of the Taskforce. The Taskforce’s discussions with the Department’s officers suggests that its funding would most sensibly be allocated
Tamar Estuary River Health Action Plan 50 to the proposed catchment actions. This funding would cover the proposed dairy related catchment initiatives and some of the grazing related program and it would therefore seem sensible to earmark them to these purposes. NRM North have had considerable success in implementing catchment based programs and would seem the likely organisation to deliver the funding if allocated to this purpose. 8.4
Clean Energy Finance Corporation The Launceston City Deal required the Taskforce to explore the possible financing of desired projects with the Clean Energy Finance Corporation. On this basis, the Taskforce has held ongoing discussions with the CEFC as it has progressed its work. The CEFC’s scope is to provide financing for projects that increase the use of renewable energy, projects that deliver increased energy efficiency or which utilise low emission technologies and does so at lending rates less than that available from private sector banks. The Combined System Working Group was consulted regarding whether the investment projects proposed would meet any of the CEFC’s criteria for financing. Notwithstanding both TasWater and Launceston City Council have limitations on borrowings such that they can only borrow through the Tasmanian Government’s financing arm, TasCorp (which would need alteration), it does not appear that any of the projects would yield material energy efficiency savings and indeed most projects require additional energy usage. The possible exception is the upgrade of Ti Tree Bend treatment plant which would need further examination.
Tamar Estuary River Health Action Plan 51 9.
Communication and education It is important that the Taskforce, or any ongoing governance body formed to implement its recommendations, place a significant focus on communicating the recommendations in this Plan and educating the community as to what underlies the findings. The reasons for this are varied, but primarily there appears to be both a misunderstanding of the natural processes which influence the Estuary and the previous interventions made to it and, possibly related to this, considerable divide between members of the community on what is required to improve Estuary health. Assuming the recommendations within this Plan are funded and acted upon, there is a need to clearly articulate the work to be undertaken to improve water quality and the health of the estuary and river systems. It is recommended that the Taskforce and any body formed to implement its recommendations, should:
communicated, audiences and methods of engagement with these audiences. At a minimum the key stories to be communicated to the community should include: o
these; o
The advantages and disadvantages of combined sewerage and stormwater systems o
Sedimentation processes and the history of sediment management through dredging and other means. Ecological values of mudflats should also be included; o
o
An overview of some of the works done to date and their impact including programs run by NRM North, Dairy Tasmania and City of Launceston; o
The TEMT, its role and recommendations and where to from here; and
Consider further the approach to communicating recreational water quality in the estuary. This might include development of an alert system through social media or a website, for example the release of advice or alerts when there’s been a combined system overflow. Alternatively a system based on monitoring or predicted rainfall could also be used. The messages around safe recreation in the estuary should be reviewed in light of improved monitoring data (e.g. periods of exclusion after rainfall, practices to minimise risk). This may be linked to the additional work the Taskforce has flagged in setting targets related to primary contact.
Tamar Estuary River Health Action Plan 52 10.
Sedimentation Following the strong feedback received through consultation, the Taskforce has resolved to engage a suitably qualified hydrologist/geomorphologist to assess the merits of the various proposals regarding the mitigation of sedimentation build up. There have been a number of studies, going back many years, commissioned by parties including the Launceston City Council, the Launceston Flood Authority and Hydro Tasmania, in addition to a number of academic research papers, many of which have explored and, in some cases, debunked theories put forward around how to manage sedimentation. These studies will be reviewed by the consultant engaged by the Taskforce when assessing the merits of the proposals received. While the Taskforce is committed to examining the proposals, based on the information gathered through its work, its current view is there are natural mechanisms of weathering, erosion and deposition that result in the ongoing modification of the Estuary and there is a limit to what can be achieved in reducing the impacts of sedimentation. The Combined System Overflow Working Group’s Investment Plan goes into some detail around these processes, but, in lay terms, the Estuary is what is known as a drowned river valley that formed between 6,500 and 13,000 years ago when sea level rose around 60m to near its current level. The natural process for drowned river valleys is to infill and eventually become alluvial (muddy) plains and deltas. The Tamar Estuary is characterised by a three to four metre tidal range and large freshwater inputs from the North Esk and South Esk rivers. The combination of a large sediment load from the catchment and strong tidal currents results in rapid sedimentation in the upper reaches of the estuary. While the main channel is quite deep in the lower estuary, reaching 45 metres in depth near Bryants Bay, upstream of Swan Point at Paper Beach the Estuary is subject to rapid infilling through sedimentation and becomes very shallow near Launceston. Tidal mudflats border the main channel of the estuary throughout its length. Though there are potential issues with silt raking which mean consideration needs to be given to the balance between environmental outcomes and flood protection, it is proven in its ability to displace the sediment build up and maintain a level of visual and recreational amenity in the upper reaches. The Taskforce aims to report on this issue, including any viable alternatives, in the first quarter of 2018.
Tamar Estuary River Health Action Plan 53 11.
Ongoing governance The Launceston City Deal flagged that the Taskforce would give consideration to the future governance of the Estuary and the Taskforce has resolved to engage further advice on this issue. While there are a number of models that are used elsewhere in the country, particularly models that install catchment management authorities to ensure water health, the roles of TasWater and Launceston City Council in delivering on this aim are not a usual part of that model. While the existing structures of the TEER have been extremely successful in bringing all relevant stakeholders together and much has been advanced by TEER in understanding the Estuary, monitoring its health and setting targets for it, perhaps one deficiency has been its inability to attract large scale funding to address some of the issues outlined in this Plan. A continuum of option will be explored from collaborative models like TEER and the similar Derwent Estuary Program in the South of the State, through to legislatively backed governance models. However, the key questions that will be asked through this work will be what the objectives and functions of the body should be and how best these would be performed, with the structural form following from that. As with the work underway on sedimentation, it is intended that the Taskforce will deliver a report with recommendations in the first quarter of 2018.
Tamar Estuary River Health Action Plan 54 Appendices 1.
Tamar Facts 2.
Catchment Action Working Group Technical Report and Investment Plan 3.
Combined System Overflow Working Group Investment Plan 4.
An Investment Plan for improving water quality in the Tamar Estuary: Combined System Overflows Technical Report
Tamar Estuary River Health Action Plan 55
Tamar Estuary Management Taskforce C/- Infrastructure Tasmania 4 Salamanca Place Hobart TAS 7000 Australia Phone:
03 6166 3463 Email:
temt@stategrowth.tas.gov.au
Web: https://www.stategrowth.tas.gov.au/infrastructure_ tasmania/tamar_estuary_management_taskforce/ Yüklə 1,91 Mb. Dostları ilə paylaş:
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