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Water Restrictions

Background

The security of supply for the Rylstone reticulated water system is significantly different from that of Mudgee and Gulgong due to the fact that the Rylstone system draws water from the Rylstone Dam, which has a capacity of 3,320ML while Mudgee and Gulgong source their water from the Cudgegong River downstream of Windermere Dam and have the added protection of significant ground water sources.

As a result, the towns and villages serviced by the Rylstone system have faced severe restrictions from time to time in the past.

The Rylstone Dam was constructed by the Public Works Department in 1954 together with a reticulated supply to service the townships of Rylstone and Kandos, which was completed in 1955. In later years this supply was extended to Charbon and Clandulla.

Triggers for Restrictions - Rylstone Water Supply System

In March 2004, Council resolved to adopt the attached table indicating restrictions and their relationship with the dam level supplying water to the treatment works in Rylstone.

The report tabled at that meeting highlighted the effect of the drought in 2002/03 on the levels in the Rylstone Dam, which dropped to around 40% capacity at that time. It should be noted that once the dam reaches 25% capacity the remaining water is unusable due to quality and pump lift concerns. Predictions made in February 2003 indicated that without restrictions, the supply would be exhausted by April of that year.

Whilst the value of water restrictions has been questioned by some as an ineffective means of reducing consumption, especially without a corresponding enforcement of compliance, the mechanisms put in place to protect the Rylstone water supply system have proven effective since their introduction in March 2004. In addition, the voluntary restrictions imposed during the summer of 2002/03 resulted in a dramatic decrease in water consumption.

Unfortunately it is not as simple as stating that the level of restrictions in one part of the region should be reflected in all parts of the region. The reality is that each town supply has different security of supply regimes. In Mudgee and Gulgong, a secure supply is available from the Cudgegong River, with licensing arrangements protecting that supply. In the unlikely event that access to the river water was denied, these towns continue to have the ability to tap into the ground water aquifers using the benefit of infrastructure utilised up until completion of new water treatment plants for those townships.

The issue in Rylstone is that the only supply of water to the system there is via the Rylstone Dam. If the level of that dam were to drop to the 25% level, the only option to provide water to the towns served by the Rylstone system would be to cart water in – a very expensive and restrictive practice.

Water Restrictions Levels

Security of Supply Analysis

In March 2008 Council engaged engineering consultants GHD P/L to investigate the following alternative water supply options:

• Groundwater – extract groundwater and pump to the treatment plant at Rylstone.
• Windamere Dam – pump water from the Windamere Dam to the treatment plant at Rylstone.
• Dunn’s Swamp – gravity feed water from the Kandos Weir at Dunn’s Swamp to the treatment plant at Rylstone.
• Effluent Recycling – Effluent from Rylstone, Kandos, Charbon and Clandulla would be treated to a high level and pumped to the Rylstone Dam.

Options were assessed against key levels of service and the study objectives as follows:

Levels of Service

• Desirable supply level – Normal summertime demand of three megalitres per day.
• Minimum Supply Level – Severe water restrictions with no residential outdoor use (one megalitre per day)
• Emergency Supply Level – Rationed water supply following failure of the primary supply. (eg; water carting requirements, assessed at 0.54 megalitres per day).

Objectives

• To improve the security of the water supply, achieved by reducing the likelihood of supply failure, and therefore being able to deliver the Minimum Supply Level at all times.
• To reduce the frequency and duration of water restriction for customers, achieved by improving the reliability of the system in delivering the Desirable Supply Level.

A Draft report has been prepared for Council’s review and comment. It is recommended that the Draft report be placed on public exhibition for comment for a period of 28 days.

Groundwater Supply Option

The feasibility of accessing groundwater for an alternative or supplementary supply was assessed by reviewing the geology and existing groundwater bores within an economically feasible distance of the water treatment plant. The desktop study found that there would be limited groundwater supply potential.

Test drilling was carried out within alluvial deposits adjacent to the Cudgegong River at a property downstream of Rylstone to determine the depth of alluvium and to collect groundwater for quality analysis. Test drilling samples indicated that the alluvium aquifer is not very permeable and therefore the achievable flow rate would be poor. Water tests indicated that the quality is not ideal for town water supply due to moderate salinity.

The investigation concluded that sufficient groundwater would not be available to meet the emergency supply level, and the installation of bores would only serve to supplement water carting in the case of a primary water supply failure.

Windamere Dam Supply Option

This option involves pumping water from the Windamere dam located on the Cudgegong River downstream from Rylstone. As the capacity of Windamere Dam is large compared to the Rylstone water supply scheme and as the capital cost will be large, regardless of the size of the pipeline installed, the option was assessed for delivering the peak day demand.

Three options were considered as follows:

• Option A - Pumping from immediately downstream of the dam, which will allow pumping until the minimum draw off level of the dam. The option includes 25km of pipeline and multiple pump stations. The estimated cost of construction is $9.5million and the estimated annual operating cost is $120,000.
• Option B – Pumping from near the middle of the dam, which will allow pumping to approximately 5% of the dam capacity. The option includes 21km of pipeline and multiple pump stations. The estimated cost of construction is $8.5million and the estimated annual operating cost is $110,000.
• Option C – Pumping from near the tail end of the dam, which will allow pumping to approximately 10% of the dam capacity. The option includes 15.5km of pipeline and multiple pump stations. The estimated cost of construction is $6.7million and the estimated annual operating cost is $95,000.

As pumping from Windamere will be significantly more expensive than pumping from the Rylstone Dam, the system would not normally be operated unless the Rylstone dam was low. The system might be used only for a few months during summer and might not be used every year. It is therefore difficult to justify the large infrastructure cost of this option.

Dunn’s Swamp Option

This option involves supplementing the supply with water from the Kandos Weir at Dunn’s Swamp. The Kandos weir was built in 1930 to supply water to Cement Australia’s Kandos manufacturing plant. A section of the Cudgegong River in the Wollemi National Park was dammed and a pipeline constructed from the dam to the cement manufacturing plant approximately 20 kilometres away.

Two options were considered as follows:

• Constructing a pipeline a distance of approximately 25 kilometres from the Kandos Weir to the Rylstone Water Treatment Plant. The estimated cost of construction is $4.9million and the estimated annual operating cost is $38,000. However, Dunn’s Swamp lies in the Wollemi National Park which is included on the UNESCO world heritage list due to the biodiversity of plant and animal communities including the recently discovered Wollemi Pine, and it would be difficult obtaining approval form Commonwealth and State agencies for the construction of a pipeline through the Park.
• Use of the existing Cement Australia Pipeline. The Cement Australia pipeline would be intercepted near the intersection of Dabee and Glen Alice Roads and a new pipeline constructed for a distance of approximately 7 kilometres to the Rylstone Water Treatment Plant. The estimated cost of construction is $1.3million and the estimated annual operating cost is $25,000. The use of the Cement Australia pipeline is contingent on the permission and operating restrictions of Cement Australia.

Due to the heritage and environmental sensitivity of Dunn’s Swamp, it would be difficult to obtain a licence for other than securing supply, and the Dunn’s Swamp options have therefore been assessed only for delivering the Minimum Supply Level, that is, during drought conditions when the Rylstone Dam is low. The system would therefore be used infrequently, if at all, considering that the Rylstone Water supply has never actually run out of water. It is therefore difficult to justify the large infrastructure cost of constructing a separate pipeline. However, utilising the Cement Australia pipeline to provide security warrants further investigation.

Reuse Option

As the Rylstone, Kandos and Villages Sewerage Augmentation is presently in the planning stage, there is scope to redesign the system so that potable water reuse can be achieved. Three options of reuse have been discussed as follows:

• Urban non-potable reuse. This option involves the construction of a separate distribution and reticulation system for delivering recycled water for non-potable use. In residential areas, recycled water is used for flushing toilets and outdoor irrigation. As the cost of constructing a new distribution and reticulation system in an urban setting is high, this type of system is usually only considered in growth areas.
• Direct potable reuse. This option involves the delivery of very high quality reclaimed water directly into the water supply system. However, direct potable reuse of reclaimed water has not yet gained acceptance within Australia due to the potential risks to public health.
• Indirect potable reuse. This option involves supplementing the raw water source with treated wastewater. Indirect potable reuse can be unplanned, such as drawing water from a source that has received an upstream wastewater discharge (eg; at Mudgee or Gulgong), or planned, where the water source is intentionally fed by the discharge of treated wastewater.

Of the above reuse options planned indirect potable reuse is the most attractive. This is for a number of reasons including it being an extensively studied and practiced technology. The scheme involves the construction an advanced wastewater treatment plant at Rylstone and a pipeline from the wastewater treatment plant to the Rylstone Dam. The estimated cost of construction is $3.9million (over and above the cost of a conventional wastewater treatment plant and discharge facility) and the estimated (additional) annual operating cost is $260,000.

Summary

In summary, the investigation did not find an economically and environmentally feasible alternative water supply that has the potential of achieving the dual objectives of securing the Rylstone Water Supply and reducing the frequency and duration of water restrictions for customers. However, the alternative of securing a minimum supply by constructing a pipeline from the Cement Australia supply from Dunn’s Swamp warrants further investigation.

Additional Studies

A subsequent investigation has commenced to determine if the frequency of water restrictions can be improved by better managing the Rylstone Dam Supply. Additional investigations being carried out include modelling the dam to obtain an accurate stage/storage relationship, and a catchment yield analysis and dam water balance considering all inputs (rainfall and runoff) and outputs (evaporation, infiltration, environmental flows, town water use and private water use). It should be noted that the Rylstone town water demand of approximately 400ML per year is only a small proportion of the total demand (the total of private water licences accessing the dam is about 800ML per year, but which is not presently monitored).

Options available to Council include:

• Purchasing properties adjacent to the dam and/or their water licences. It is estimated that the cost of purchasing relevant adjacent properties would be $1million to $1.5million (land) plus buildings. Part of this cost could be recovered by consolidating/subdividing the land and retaining only a larger foreshore and the water licences (ie later selling land with road frontage).
• Restricting access to the dam foreshores owned by Council. As Council owns all of the land on which the dam is situated, adjacent properties exercising their water licence rights are doing so by accessing Council land. Council can therefore exercise control over access by private licence holders to the water in the dam. Council could require that private licence holders fit tamper-proof water data logging meters to their pumps so that Council could monitor their consumptions. Council could also deny access at any time, but particularly during periods of low rainfall. This option would require fencing approximately 15kilometres of property boundary, installing data logging meters on private water supplies, installing flow meters both upstream and downstream of the dam, developing a detailed dam operating procedure and the formation of a Rylstone Dam water users group.

Council is awaiting detailed licence information from the Department of Water and Energy which has been requested under the Freedom of Information Act. Comments from Council and customers would be addressed in the final report.