Tamar Estuary
River Health Action Plan
5
As a number of these projects will increase the flows being received directly by Ti Tree Bend Sewerage
Treatment Plant, an analysis of that Plant’s performance in higher flow conditions was completed. This showed
that while the Plant would continue to perform well in treating enterococci and addressing suspended solids, its
performance would be expected to drop off in terms of its nutrient treatment with the additional flows being
received. It was the Taskforce’s view that while its focus was on improving public health in Zone 1, an outcome
where that goal was met, but the ecological health of the Estuary decreased due to a decline in nutrient
treatment, would be an unacceptable outcome.
For this reason, the Working Group also included a $10 million project to upgrade nutrient treatment at Ti Tree
Bend Plant which is based on preliminary project concepts and costing that TasWater has completed. While it is
acknowledged that the Ti Tree Bend project costing is based preliminary estimates and has the potential to be
understated by a higher degree than other projects identified, the chart below shows the expected reductions in
concentrations in Zone 1 from implementing the six proposed combined system overflow projects and the
upgrade of the Ti Tree Bend.
Full separation of the combined system has an estimated cost of $435 million and assumes that this would
decrease combined system overflows to the Estuary by 100 per cent. It is clear the proposed mitigation projects
provide significant value for money and would reduce enterococci concentrations by more than 35 per cent in
Zone 1, or expressed another way, approximately a 70 per cent reduction in combined system sewage load for
an estimated $84.6 million total investment. Significant nutrient reduction would also be delivered from these
initiatives.
As can be seen, full separation is extremely costly at over 4.5 times the cost of the projects proposed and would
require works to be undertaken in up to 7,000 homes to ensure separation of private plumbing infrastructure,
not to mention the complexity of works that would occur in commercial parts of the City. This upheaval would
be considerable and the total cost may be conservative depending on the level of complexity of rectification
works on private pipes, the location of driveways, garages and trees and the for commercial customers the
potential loss of trade while works were undertaken.
Tamar Estuary
River Health Action Plan
6
Recommended Projects and Implementation
The table below outlines the individual and combined value of the projects and actions that the Taskforce believes
will yield the best value for money improvements to the Tamar Estuary. The Taskforce is of the view that
significant benefits can be delivered to the health of the Tamar Estuary for an investment of under $100 million.
Projects
Estimated Cost ($
million)
Catchment Actions
Brumbys-Lake, Macquarie, Meander & Tamar - Dairy
1.10
North Esk - Grazing
1.33
Upper Tamar – Grazing
1.66
Brumbys-Lake, Meander and South Esk – Grazing
5.41
Launceston sewage stormwater intrusion
0.50
Combined system actions
Esplanade storage
6.7
Forster St storage
8.4
New Margaret St storage
10.0
South Launceston Diversion
18.1
West Launceston Diversion
4.6
New combined rising main
26.8
Ti Tree Bend plant nutrient removal upgrade
10.0
Total
94.6
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.
Evidence from similar programs in other Tasmanian catchments reveals that along with early adopters of a such
program, momentum is generally created by the relatively large scale 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 could 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 as asset owner.
While these projects are conceptually part of TasWater’s Launceston Sewerage Improvement Plan, it is not
currently clear how prioritising these works for the benefit of Estuary health would align with TasWater’s
priorities, nor what funding from TasWater may be appropriate. A negotiation with TasWater will be necessary
to understand issues of timing and capacity for delivery.