Tweed Shire Demand Management Strategy & Water Supply Augmentation Options Study A Brief Technical Review quality solutions sustainable future Tweed Shire Demand Management Strategy & Water Supply Augmentation Options Study A Brief Technical Review © GeoLINK, 2011 PO Box 9 Lennox Head NSW 2478 T 02 6687 7666 PO Box 1446 Coffs Harbour NSW 2450 T 02 6651 7666 [email protected] Version History UPR Description Date Issued Issued By Reviewed By 9030371 1st issue 08/02/2011 Duncan Thomson Craig Zerk Table of Contents 1 Background 1 2 General Comments 3 1.1 Separation of the Studies ....................................................................................................................... 3 1.2 Baseline Forecasts ................................................................................................................................. 3 3 Tweed Shire’s Future Water Supply 5 2.1 The Challenge ........................................................................................................................................ 5 2.1.1 Note on Scenario 1 Assumptions ....................................................................................................... 5 2.2 Council's Current Favoured Options ....................................................................................................... 5 2.3 Potential Alternative Options .................................................................................................................. 6 2.3.1 Larger Rainwater Tanks ..................................................................................................................... 6 2.3.2 Recycled Water combined with Rainwater Tanks .............................................................................. 7 4 Closing Remarks 9 Tweed Shire Demand Management Strategy & Water Supply Augmentation Options i Study: A Brief Technical Review 9030371 1 Background 1 1 1 The purpose of this document is to present the key issues identified as part of a brief technical review of various reports associated with the planning of the future water supply for Tweed Shire. These reports include: Tweed Shire Council: Demand Management Strategy – Stage 1 (MWH, Rev. No. 3, 16/11/09) Tweed Shire Council: Demand Management Strategy – Stage 2 (MWH, Rev. No. 2.1, 21/12/09) Tweed Shire Council: Demand Management Strategy (MWH, Rev. No. 1.1, 21/12/09) Tweed District Water Supply Augmentation Options Study: Stage 3 – Fine Screen Assessment of Shortlisted Options (MWH, Rev. No. 3.0, 28/09/10) The review was carried out by engineers from GeoLINK, an environmental management and design consultancy that has been in operation on the north coast of NSW for twenty years. GeoLINK undertook the review at its own initiative and did not receive any payment for the work. The purpose of this review is to consider the water supply planning process with a 'fresh set of eyes'. The intention is to provide constructive suggestions that will assist Council in its quest to pursue the most appropriate and sustainable water supply strategy for Tweed Shire. This document constitutes a 'brief technical review'. It is not a comprehensive review of the aforementioned reports. It is understood that the water supply planning process has been ongoing for at least the past four years, involving the detailed analysis of options and collaboration with stakeholders. GeoLINK has not been involved in any aspect of this process and it has been a challenge to come 'up to speed' with the key issues in a short timeframe. Therefore, despite the fact that this document has been prepared in good faith, it is possible that some of the comments and assertions are inaccurate due to a lack of detailed understanding of the work. Tweed Shire Demand Management Strategy & Water Supply Augmentation Options 1 Study: A Brief Technical Review 9030371 2 General Comments 2 2 2 1.1 Separation of the Studies Undertaking the Demand Management Strategy and the Water Supply Augmentation Options Study as separate processes (as has been done in Tweed Shire) is unlikely to produce the best outcome. Both processes are a means to the same end – i.e. ensuring there is sufficient water for the projected future population scenario. The required outcome can be achieved by numerous combinations of initiatives. Whether those initiatives are classified as 'loss reduction', 'demand management', 'water recycling' or 'supply augmentation' is inconsequential. The most appropriate and sustainable water supply strategy should be developed by considering all options in an integrated manner. The Water Supply Augmentation Options Study assessed nine options: Option 1 – Raising Clarrie Hall Dam Option 2 – New dam on Byrrill Creek Option 3 – New dam on Oxley River Option 4 – Pipeline to connect to Rous Water network Option 5 – Pipeline to connect to SEQ network Option 6 – Desalination Option 7 – Groundwater supply Option 8 – Indirect potable reuse Option 9 – Direct potable reuse It would have been beneficial to include the options considered in the Demand Management Strategy (i.e. rainwater tanks and localised application of recycled water) in the same multi criteria assessment process to ensure the most appropriate integrated strategy was identified. It is acknowledged that these options on their own are unlikely to satisfy the required annual yield. However, this highlights a shortcoming of the Water Supply Augmentation Options Study, which is that combinations of options were not considered. Options 4 and 7 were automatically discarded because they didn't meet the minimum annual yield requirement. This ignores the possibility that they could have formed part of an integrated (and perhaps more flexible and resilient) solution that might have scored well in the multi criteria assessment. For example, what would have been the score for an option incorporating groundwater supply and recycled water for the greenfield major development areas? 1.2 Baseline Forecasts The NSW BASIX legislation and the federal WELS scheme are 'givens' – they are not options that Council can decide to either pursue or abandon. All new residential buildings, as well as significant additions or alterations to existing residential buildings, must comply with the water saving requirements of BASIX. The WELS scheme has been in place for more than five years and it is reasonable to assume that it will not be abandoned. Therefore, the impact of BASIX and WELS should be included in any baseline forecasts of future water demand, because this essentially represents the 'do nothing' option from a Council perspective. It is considered unrealistic to present baseline forecasts that do not include the impact of these measures, as has been done in various reports, including Section 4.3.6 of the Demand Management Strategy – Stage 1 and Section 2.2.2 of the Water Supply Augmentation Options Study. It is acknowledged that these unrealistic baseline forecasts have not been used to determine the required annual yield. However, the presentation of these forecasts in various tables and Tweed Shire Demand Management Strategy & Water Supply Augmentation Options 3 Study: A Brief Technical Review 9030371 charts is considered to be unhelpful to the process, because it provides a misleading impression of the Shire’s future water demands. There is also concern that the baseline forecasts may have been unwittingly over-estimated because the numbers presented in Table 4-3 of the Demand Management Strategy – Stage 1 are inconsistent with the numbers presented in the preceding Tables 4-1 and 4-2. If the numbers presented in Tables 4-1 and 4-2 are correct, then the average daily consumptions per account for 2004/05 and 2005/06 presented in Table 4-3 have been over-estimated by approximately 14%. If indeed there has been an unintentional over-estimation in Table 4-3, it appears as though this error has been carried through to Tables 4-4 and 4-5 and the subsequent baseline forecasts. Tweed Shire Demand Management Strategy & Water Supply Augmentation Options 4 Study: A Brief Technical Review 9030371 3 Tweed Shire’s Future Water Supply 3 3 3 2.1 The Challenge According to Section 2.2.2 of the Water Supply Augmentation Options Study, the current secure yield of 13,750 ML/yr will be exceeded in 2023 if Scenario 1 eventuates or 2031 if Scenario 4, which is Council's adopted 'demand management' scenario, eventuates. Given that Scenario 4 has been adopted by Council and presumably will be adequately funded and resourced, this scenario would seem to be a likely outcome. However, the study has adopted Scenario 1 for forecasting future water demands stating that it is a more conservative target and more readily achievable. Based on Scenario 1, future water demand is predicted to rise to 16,750 ML/yr by 2036, the end of the planning period. Therefore, the objective is to find an additional 3,000 ML/yr of secure yield compared to Scenario 1. 2.1.1 Note on Future Water Demand Forecasts The future water demand forecasts quoted above are taken from the Tweed District Water Supply Augmentation Options Study: Stage 3 – Fine Screen Assessment of Shortlisted Options (MWH, Rev. No. 3.0, 28/09/10). However, a presentation to a Council workshop in late 2010 appears to indicate that the forecasts have been refined since the publication of this report and that under Scenario 1 the current secure yield of 13,750 ML/yr will not be exceeded until 2026 or possibly even 2030. Accordingly, the forecast water demand in 2036 has been revised down to 15,750 ML/yr or possibly