Nambucca Water Supply Investigation of On-stream …NSW Public Works – Dams and Civil Section...

George Samios | Senior Dams Engineer Dams and Civil Section | NSW Public Works NSW Department of Services, Technology & Administration T 02 9372 7804 F 02 9372 7822 E [email protected]

Nambucca Water Supply

Investigation of On-stream Water

Storages

Nambucca Shire Council

Report Number: DC10092 September 2010

NSW Public Works – Dams and Civil Section September 2010 Report Number: DC10092

Nambucca Shire Council Nambucca Water Supply Investigation of On-stream Water Storages

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Executive Summary The Dams and Civil Section (D&C) of NSW Public Works was engaged by Nambucca Shire Council (NSC) to investigate the construction costs and risks associated with the two potential on-stream dam sites identified by D&C in June 2007. The total construction costs of the proposed League Creek and Gravelly Creek dam sites were revised to be $ 102.2 Million and $ 88.4 Million respectively. The costs include the construction of a pipeline water delivery system from the proposed dam sites to the existing Bowraville Water Headworks, which was found to be the preferred delivery method over the delivery via Nambucca River. The costs exclude the construction of a fishway structure, which may cost up to $ 20 Million as its necessity and configuration are highly sensitive and dependent on environmental, social and economical requirements. The final site selection would include the analysis and opinions of stakeholders, regulating authorities and potential funders associated with this major project.



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TABLE OF CONTENTS

1 INTRODUCTION .............................................................................................................. 1

2 PROPOSED DAM LOCATIONS ...................................................................................... 2

2.1 League Creek .............................................................................................................. 2

2.2 Gravelly Creek............................................................................................................. 2

3 WATER DELIVERY.......................................................................................................... 3

3.1 League Creek .............................................................................................................. 3 3.1.1 Pipeline Delivery....................................................................................................... 3 3.1.2 Alternative Nambucca River Delivery....................................................................... 4

3.2 Gravelly Creek............................................................................................................. 4 3.2.1 Pipeline Delivery....................................................................................................... 4 3.2.2 Alternative Nambucca River Delivery....................................................................... 5

3.3 Discussion of Delivery Method ................................................................................. 5

4 DAM STORAGE INUNDATION AREAS.......................................................................... 6

4.1 League Creek .............................................................................................................. 6

4.2 Gravelly Creek............................................................................................................. 6

5 ON-STREAM WATER STORAGE RISKS ....................................................................... 7

5.1 Overview...................................................................................................................... 7

5.2 Sedimentation ............................................................................................................. 7

5.3 Algal, Water Quality and Other Contaminants ........................................................ 8

5.4 Flooding....................................................................................................................... 8

5.5 Environmental Issues in the Inundation Area ....................................................... 10

5.6 Fish Passage............................................................................................................. 10

5.7 Maintenance of Environmental Flows .................................................................... 11

5.8 Legislative ................................................................................................................. 12

5.9 Grant Funding........................................................................................................... 14

5.10 Catchment Area Management ................................................................................. 14 5.10.1 Adequacy of Required Runoff............................................................................ 14 5.10.2 Water Pollution Issues ....................................................................................... 15

6 COST ESTIMATES ........................................................................................................ 16



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7 CONCLUSION................................................................................................................ 17

REFERENCES ........................................................................................................................ 18

TABLES Table 1 Proposed League Creek Dam Data ........................................................................ 2 Table 2 Proposed Gravelly Creek Dam Data....................................................................... 2 Table 3 Proposed League Creek Pipeline Statistics ............................................................ 4 Table 4 Proposed Gravelly Creek Pipeline Statistics........................................................... 5 Table 5 League Creek Dam Inundation Area Information ................................................... 6 Table 6 Gravelly Creek Dam Inundation Area Information .................................................. 6 Table 7 Approval Authorities .............................................................................................. 12 Table 8 Total Construction Cost Estimates........................................................................ 16 Table 9 Total Operation and Maintenance Cost Estimates ............................................... 16 Table 10 Potential Fishway Cost Estimates ..................................................................... 16

FIGURES Figure 1 – League Creek Dam Site Plan Figure 2 – League Creek Dam Inundation Area Figure 3 – Gravelly Creek Dam Site Plan Figure 4 – Gravelly Creek Dam Inundation Area Figure 5 – Plan of River Crossing and Existing Headworks

APPENDIX Appendix 1 – Construction Cost Estimate of League Creek Dam Appendix 2 – Construction Cost Estimate of Gravelly Creek Dam Appendix 3 – Construction Cost Estimate of League Creek Dam Pipeline Appendix 4 – Construction Cost Estimate of Gravelly Creek Dam Pipeline



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1 INTRODUCTION Nambucca Shire Council (NSC) is situated on the Mid North Coast of NSW, midway between Sydney and Brisbane. The Nambucca Local Government Areas consists of an area of approximately 1,400 km2 and contains 10 towns and villages – Nambucca Heads, Macksville, Bowraville, Valla Beach, Scotts Head, Eungai Rail, Taylors Arm, Warrell Creek and Donnellyville. It has a population of approximately 19,000. The southern and western boundaries of the Shire are generally defined by the Nambucca River Catchment. The eastern boundary is defined by the South Pacific Ocean while the northern boundary is approximately 4 km north of Valla Beach and runs almost directly west. NSC has been advised that its water supply has inadequate drought security and has been working with the Dams and Civil Section (D&C) of NSW Public Works to develop strategies to ensure it has an urban water system with adequate drought security as well as optimum water conservation practices. To date an Integrated Water Cycle Management Strategy has been prepared. In addition NSC has undertaken considerable planning, including the preparation of an Environmental Impact Statement (EIS), for the provision of an off-stream water storage of 5,500 ML near Bowraville. D&C has also carried out an inspection of potential on-stream dam sites and preliminary construction cost estimates were prepared in June 2007. The work which has been undertaken in relation to the proposed off river water storage has highlighted a number of risks and operating costs. NSC now wishes to undertake further preliminary investigation of options for an on-stream water storage so that it may have better information on costs and risks against which the proposed off-stream water storage may be evaluated. The purpose of this report is to:

1. Update the construction cost estimates for the two preferred 5,500 ML on-stream dam options which were identified in a report prepared by D&C (then known as D&C from NSW Department of Commerce) in June 2007;

2. Estimate the cost of transferring stored water from the two proposed dam sites to

NSC’s water headworks at Bowraville;

3. Estimate the area of private land and State Government owned land which would be inundated by the two proposed dams’ storages; and

4. Appraise NSC of any generic and observed risks for on-stream storage dams at both

proposed locations.



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2 PROPOSED DAM LOCATIONS

2.1 League Creek A Roller Compacted Concrete (RCC) dam has been proposed at the confluence of Nambucca River and League Creek. Refer to Figures 1 and 2. This location is approximately 40 km west of Bowraville via North Arm Road. Refer to proposed dam sections in D&C’s June 2007 Inspection Report for more dam details.

Table 1 Proposed League Creek Dam Data

Dam Type RCC Operable Storage Height 17 m

Maximum Dam Height 26 m Dam Crest Length 180 m

Full Supply Level (FSL) RL 155.0 mAHD Dam Crest Level RL 161.6 mAHD

FSL Storage Volume Approx. 5,500 ML FSL Inundation Area Approx. 21.4 ha

2.2 Gravelly Creek A zoned earthfill dam has been proposed at the confluence of Nambucca River and Gravelly Creek. Refer to Figures 3 and 4. This location is approximately 20 km west of Bowraville via North Arm Road. Refer to proposed dam sections in D&C’s June 2007 Inspection Report for more dam details.

Table 2 Proposed Gravelly Creek Dam Data

Dam Type Zoned Earthfill Operable Storage Height 7 m

Maximum Dam Height 22 m Dam Crest Length 200 m

Full Supply Level (FSL) RL 75.0 mAHD Dam Crest Level RL 83.4 mAHD

FSL Storage Volume Approx. 5,500 ML FSL Inundation Area Approx. 105.3 ha



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3 WATER DELIVERY

3.1 League Creek

3.1.1 Pipeline Delivery A pipeline could be constructed connecting the proposed dam’s outlet pipework directly into Bowraville’s Water Headworks. The pipeline route has been proposed to run along Gaddess Ridge Road connecting to North Arm Road for the majority of its length from where it would cut east, deviating from Lower North Arm Road, before connecting to the headworks location between Nambucca River and Bellingen Road. With the current available geographical information, efforts have been made to ensure that the majority length of the proposed pipeline route runs along NSC’s road reservations where practical while the rest would be constructed along pipe easements to be purchased by NSC. This would limit on NSC’s acquisition for private land. NSC has advised that, in general, along North Arm Road, the road reservation width available is approximately 6.5 m away from either side of the road. This should generally satisfy the required width for construction easements. For general easements, engineering practice is to allow for a minimum clearance width, the same distance as the pipe depth from ground surface to its invert, from the outer edge of the pipe to the nearest civil structure, depending on the pipe trench excavation method. This would be further examined in depth along with the locations of existing overhead and underground services during the detail design phase. For the pipeline route, following the route of a major road would be the most logical and suitable because:

� It would provide convenient access for construction machinery; � It could eliminate the need to excavate through thickly vegetated hills, which may be

impractical;

� It would provide convenient access for maintenance procedures. However, there are portions of the route where deviation from the major roads are inevitable to suit the existing topography. Refer to Figures 1 and 5 for this pipeline plan.



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Table 3 Proposed League Creek Pipeline Statistics

Pipeline Distance Approx. 36 km from dam to headworks Approx. Length of Forested Land

to be cleared 15 km (all in private land)

Approx. Length of Pipeline Easement required 12 km (all in private land)

Number of Major Road Crossings 13

Mostly across Gaddess and North Arm Roads

Number of Minor Road Crossings

12

Mostly across unnamed roads connecting into major roads

Number of River Crossings

1

Across Nambucca River to headworks at north of Borefield Road

3.1.2 Alternative Nambucca River Delivery Water could also be delivered to the Bowraville Water Headworks from the proposed dam via Nambucca River. A weir pool would be created to allow water extraction into the existing headworks from the proposed dam’s calculated releases down Nambucca River. A weir structure would be constructed at a convenient location in the proximity of the existing headworks to build up the water level in Nambucca River. This would assist the water extraction process from an adjacent pump station into the existing headworks. This option would keep land disturbances to a minimum as the main construction works (besides the main dam) would only occur in the proximity of Nambucca River and the Bowraville Water Headworks. Construction works for this option would include:

� A weir structure on Nambucca River in the proximity of the existing headworks; � A pump station adjacent to the weir structure to extract the water from the created

weir pool;

� A short pipeline to transfer the extracted water from the pump station to the existing headworks.

3.2 Gravelly Creek

3.2.1 Pipeline Delivery A pipeline could be constructed connecting the proposed dam’s outlet pipework directly into Bowraville’s Water Headworks. The pipeline route has been proposed to run along North Arm Road for the majority of its length where it would cut east, deviating from Lower North Arm Road, before connecting to the headworks location between Nambucca River and Bellingen Road. As explained in Section 3.1.1, efforts have been made to minimise NSC’s acquisition for private land to construct the pipeline. Refer to Figures 3 and 5 for this pipeline plan.



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Table 4 Proposed Gravelly Creek Pipeline Statistics

Pipeline Distance Approx. 20 km from dam to headworks Approx. Length of Forested Land

to be cleared 5 km (all in private land)

Approx. Length of Pipeline Easement required 10 km (all in private land)

Number of Major Road Crossings 5

Mostly across Gaddess and North Arm Roads

Number of Minor Road Crossings

5

Mostly across unnamed roads connecting into major roads

Number of River Crossings

1

Across Nambucca River to headworks at north of Borefield Road

3.2.2 Alternative Nambucca River Delivery Refer to Section 3.1.2.

3.3 Discussion of Delivery Method Compared to pipeline delivery method, the alternative Nambucca River delivery method is associated with more potential risks:

1. The construction of another on-stream structure (i.e. the weir structure) would attract more negative attention form parties of interest, in addition to the proposed dam. The presence of this weir structure, required to aid the water pumping processes, would require another separate EIS to be carried out due to its anticipated size;

2. The upstream weir pool created by the weir structure may reach inundation extents

unacceptable to the parties of interest;

3. The weir structure would be another obstruction to the upstream / downstream migration of aquatic lives, in addition to the proposed dam;

4. Security of the deliverable water volumes would become an issue as the water would

be exposed along Nambucca River to potential evaporation and illegal pumping activities;

5. The total cost of construction for the weir structure and pumping station is anticipated

to be similar, if not more than the civil works associated with the pipeline delivery method.

Having examined the above issues associated with the alternative Nambucca River delivery method, the preferred delivery method was determined to be via a pipeline system as it would involve less environmental and security issues.



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4 DAM STORAGE INUNDATION AREAS

Potential inundation areas created by the proposed dams were analysed on a 10 m contour map and cadastre boundaries supplied by NSC for both sites. The inundation areas were calculated by the software ArcGIS.

4.1 League Creek

Table 5 League Creek Dam Inundation Area Information

Potential Inundation Area Approx. 21.4 ha

Areas Inundated 1,300 m2 of State owned land (0.6%) 21.3 ha of private land (99.4%)

Roads Inundated • 1.3 km of Nambucca River Road, upstream NW of the dam; • 300 m of Gaddess Ridge Road, upstream NW of the dam; • 275 m of League Creek Road, upstream SW of the dam.

Properties Affected 5 considering roads also as boundaries

Total Length of Road Diversions

• 2.1 km of Gaddess Ridge Road (also accommodates for League Creek Road Diversion);

• 1.3 km of Nambucca River Road. Diversions of Nambucca River, Gaddess and League Creek Roads are inevitable as the inundation of League Creek cuts off traffic connection from upstream of the proposed dam to its location via all three roads. Efforts were made to keep the proposed diversion route grades as flat as possible to avoid tunnelling through hills and excessive up / down slopes. The orientation of the diversions may change after detail survey has been carried out. Refer to Figure 2 for the League Creek Dam inundation map.

4.2 Gravelly Creek

Table 6 Gravelly Creek Dam Inundation Area Information

Potential Inundation Area Approx. 105.3 ha Areas Inundated 100% private land Roads Inundated 900 m of North Arm Road, upstream N of the dam

Properties Affected 20 considering roads and Nambucca River also as boundaries Total Length of North Arm Road Diversion 3.8 km

Diversion of North Arm Road is inevitable as the inundation of Gravelly Creek cuts off traffic connection from upstream of the proposed dam to its location. Efforts were made to keep the proposed diversion route grade as flat as possible to avoid tunnelling through hills and excessive up / down slopes. The orientation of the diversion may change after detail survey has been carried out. Refer to Figure 4 for the Gravelly Creek Dam inundation map.



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5 ON-STREAM WATER STORAGE RISKS

5.1 Overview This section identifies generic or observed risks for the two on-stream water storages. These risks pertain to:

1. Sedimentation;

2. Algal, Water Quality and other Contaminants;

3. Flooding;

4. Environmental Issues in the Inundation Area;

5. Fish Passage;

6. Environmental Flows;

7. Legislative;

8. Grant Funding; and

9. Catchment Area Management.

5.2 Sedimentation Risks On-stream water storages carry risk in regards to sedimentation due to the action of flowing water within the storage and also sediments that are eroded from within the catchment. Runoff generated within the catchment would carry surface soils into the storage. Flows within the storage would mobilise sediments from upstream to downstream. Sediments would build up behind the dam wall. Sedimentation build up within the storage depends on a number of factors including:

� The level of vegetation clearance within the catchment; � The level of riparian vegetation;

� The erosion hazard of soils within the catchment;

� Size of the catchment.

Mitigation Measures Strategies are available to desilt a dam, e.g. scouring by the dam’s outlet pipework. In addition, catchment management such as revegetation strategies, especially in riparian areas, can contribute to reducing the potential for erosion and sedimentation.



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Periodic hydrographic surveys and desiltation are required to be carried out to ensure the dam’s storage volume, stability and outlet pipework are not compromised by anticipated sedimentation. Further Studies

� Catchment Landuse Investigation; � Soils assessment.

5.3 Algal, Water Quality and Other Contaminants Risks Dam storages have the risk of algal growth, especially blue-green algae. The growth of algae is dependent on the temperature and nutrient levels of stagnant surface waters in a dam’s storage. Algal growth is associated with warmer temperatures, which lead to stratification of the storage waters. Deoxygenation of waters is associated with stratification of the storage and this leads to increased nutrient releases from sediments. Nutrient concentration becomes the main variable which leads to algal growth. Nutrient levels in the storage depend on the materials carried in by the catchment’s runoff and the sediments within the storage. Hence, landuse of areas adjacent to the storage contributes to the nutrient types and amounts conveyed by runoff. For example, water nutrient levels would be expected to be high if a population of cattle were present on the banks of a flowing stream. Adverse water quality impacts are predicted during the operation of the dam, such as through the leaching of nutrients from the newly drowned soils, sedimentation (turbidity) and the decay of inundated upstream vegetation. Other potential contaminates within the storage would need to be investigated such as whether there have been previous dip sites or areas of fuel storage. Mitigation Measures

Strategies to mitigate algal growth in dam storages are available and well developed e.g. destratification processes. Artificial destratification within the storage would allow mixing of water and reduce the potential for deterioration of water quality due to chemical, thermal and physical changes.

NSC may be required to regulate landuse activities in order to minimise the risk of the dam storage’s water quality. Further Studies

� Catchment Landuse Investigation; � Destratification Processes.

5.4 Flooding Risks An on-stream storage alters flood flows upstream and downstream of the dam.



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The upstream maximum water level (or the dam’s inundation water level) would be at the proposed dam’s Full Supply Level (FSL) and upstream properties with elevations lower than the FSL would be flood–affected. The local Flood Study would be required to be updated as rainfall in the catchment would raise the dam’s inundation water level further (if the dam were to be at the FSL at the commencement of storm events) and consequently more areas could be flood-affected. This study would also redefine flood easement reservations which would impact on the availability of future development zones. Extreme flood events in the dam’s catchment may destabilise the dam’s embankment which may in term result in dambreak events. Extreme flood events alone should not pose any stability threats to a sound dam as modern dams are designed and constructed to safely cater (i.e. minimising the probability of all possible dambreak mechanisms) for a specific extreme flood event (known as the Acceptable Flood Capacity (AFC)) according to guidelines established by the NSW Dams Safety Committee (DSC). Dambreak events, whether the dam is located on or off-stream, are catastrophic especially if the dam stores a large water volume with a large population present directly downstream. Water pressures, especially during extreme flood events, acting on the dam’s upstream face may initiate dambreak events by piping, i.e. instability due to internal material erosion through a zoned earthfill dam embankment, leading to a breach. For concrete dams, water pressures may breach the concrete structure by forcing cracks from the crest downwards resulting in a dambreak. Earthquake events may also initiate breaches as described above. In addition to the extreme flood flow releases from the dam, a dambreak event would also release its storage volume downstream resulting in higher flood levels and greater flood flow velocities than just the occurrence of the extreme flood event alone, hence affecting more people and structures downstream. The forces of these extreme water flows are highly detrimental and would have the potential to destabilise buildings located directly in its path. Modern dams must incorporate reasonable factors of safety in its design and construction to ensure its stability during rare extreme events. But it is impossible to design a fail-proof dam and no matter how little, there is always a probability that a dam could break. For proposed dams, locations must be carefully selected to ensure that the Population At Risk (PAR) could be kept to a minimum, i.e. a small population situated downstream of the dam. If this is achieved, it would also minimise the Probable Loss of Life (PLL) values and subsequently the dam’s Consequence Categories (CCs). Hence Dambreak and PLL Studies are required to confirm on the dam’s CCs and to finalise the dimensions of the proposed dam and associated hydraulic structures. Further Studies

� Hydrology Study; � Flood Study; � Dambreak Study;

� Probable Loss of Life (PLL) Study;

� Dam Embankment and Abutment Stability Analysis;

� Risk Assessment.



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5.5 Environmental Issues in the Inundation Area Risks The inundation of land with the on-stream storage waters can result in adverse environmental effects. Vegetation within the inundation area would be required to be cleared or left in-situ. The conservation value of the vegetation communities to be inundated would need to be assessed, especially as to whether nationally and state listed endangered ecological communities, populations and threatened species occur in the inundation area. Potential habitat is likely to exist within the inundation area for threatened species, including amphibians, reptiles, birds and mammals (including bats). The land inundated may contain cultural heritage sites, both Aboriginal and non-indigenous. It is noted that Aboriginal sites are often located adjacent to waterways. The on-stream storage would alter the aquatic habitat from a flowing stream to a lake environment. The loss of the riparian buffer is likely to have indirect impacts upon aquatic fauna, primarily through a decline in the water quality and loss of shading. There is risk that the storage would alter the ecological composition within the river. Mitigation Measures Native vegetation and fauna habitat loss would be required to be off-set as part of the planning process. Further Studies

� Terrestrial Flora and Fauna Study; � Cultural Heritage Study;

� Geomorphology Study;

� Aquatic Ecology Study.

5.6 Fish Passage Risks On-stream water storages block fish passage and prevent upstream and downstream migration of fish. Mitigation Measures A fishway with a fish lift may be required to be incorporated into the dam design to maintain fish passage for both dam locations. Further Studies

� Aquatic Ecology Study.



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5.7 Maintenance of Environmental Flows Risks The NSW Weirs Policy discourages the construction of new on stream storages. Any new dam would be required to demonstrate that environmental outcomes are maintained or improved. New on-stream storages alter the modification of the natural flow regime, impacting on the downstream ecological habitat values, morphology of the river channel and water quality. The construction of a new dam would require the release of environmental flows to protect habitat values downstream and to maintain geomorphology processes downstream. Environmental flow releases from storages can be accommodated in the dam’s outlet pipework. Both natural and human communities depend on flows within the river e.g. wildlife, irrigation industries, recreational aquatic activities etc. Investigations would be required to be undertaken to determine the quality, amount of water and timing of releases required to maintain habitat values downstream and any current human reliance on the existing flows. While maintaining water conveyance through Nambucca River, the release water volumes must not compromise the water demand from Bowraville Water Headworks. A Water Balance Analysis would be required to confirm the potential yield of the dam’s storage. This would be used to balance the demand between storage and release and establish the secure yield of the storage. NSC should be prepared to develop and enforce drought policies during dry seasons where storage for the headworks may need to become a priority over downstream releases, subject to agreed environmental flow releases to maintain current habitat values of the river system. The temperature of water to be released from the dam has the potential to impact aquatic species. Waters at a lower depth in the storage would be cooler than near the water surface, due to stratification within the storage. When cooler waters are released, this impacts on the health and habitat of existing aquatic species downstream of the dam. Mitigation Measures The thermal pollution which could result due to the dam would need to be mitigated. For example this could be addressed by the installation and incorporation of a multi-level offtake (MLO) mechanism into the dam’s outlet pipework design. This would control the temperature of waters to be released to match the existing downstream optimal conditions. Further Studies

� Flora and Fauna Study; � Water Demand Investigation;

� Hydrology Study;

� Water Balance Analysis;

� Aquatic Ecology Study;

� Drought Contingency Policies;

� Environmental Flow Assessment.



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5.8 Legislative Environmental Planning Pathway Planning and development in NSW is carried out under the Environmental Planning and Assessment Act 1979 (EP&A Act) and the Environmental Planning and Assessment Regulation 2000 (EP&A Regulation). The need for development consent is likely to be removed due to the provisions of the State Environmental Planning Policy (Infrastructure) 2007 where the proposed water storage is within a prescribed land zone. Therefore the likely planning pathway would either be a Part 5 assessment where NSC is the determining authority or a Part 3A Major Project assessment where the Minister for Planning is the approval authority. To be a Part 3A project, the Minister for Planning must consider the project to be of State or regional significance. The environmental assessment required to be completed for on-stream storages is required to assess the environmental risks of the project. The environmental assessment process for an on-stream storage normally takes several years to adequately assess the risks and to identify mitigation measures such as establishment of environmental flow regimes and identifying environmental off sets to achieve maintained or improved environmental outcomes. Approvals for Dam Construction There are a number of regulatory authorities that would be required to be consulted and provide approval for a new on-stream dam structure. The approval process will vary depending on whether the planning pathway is under Part 5 or Part 3A. Obtaining planning approvals provides risks in regards to program. The table below provides an indication of the approvals which may be required prior to an on stream storage proceeding.

Table 7 Approval Authorities

Administering Authority Nature of Approval / License if Part 5 Nature of Approval /

License if Part 3A

Nambucca Shire Council

Determination under Part 5 of the EP&A Act.

Minister for NSW Planning

Approval if Part 3A.

NSW Office of Water (part of DECCW)

Approval to construct a dam under Section 60 of the Local Government Act 1993.

Approval to construct a dam under Section 60 of the Local Government Act 1993.

NSW Office of Water (part of DECCW)

Issue of a works approval and water licence under the Water Management Act 2000/Water Act 1912 depending on status of water sharing plans.



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Administering Authority Nature of Approval / License if Part 5 Nature of Approval /

License if Part 3A

Department of Industry and Investment (Fisheries)

Dredging and reclamation under Section 200 of the Fisheries Management Act 1994.


Provisions of a fishway under Section 218 of the Fisheries Management Act 1994.

Provisions of a fishway under Section 218 of the Fisheries Management Act 1994.


Permit to block fish passage under Section 219 of the Fisheries Management Act 1994.


A species impact statement would be required to be prepared if there is a significant impact on threatened species listed under the Fisheries Management Act 1994.

Threatened species are considered as part of the Part 3A assessment.

Department of Environment, Climate Change and Water (DECCW)

Excavation works in excess of 30,000 m3 would require an Environmental Protection Licence under the Protection of the Environment Operation Act 1997.

Excavation works in excess of 30,000 m3 would require an Environmental Protection Licence under the Protection of the Environment Operation Act 1997.

National Parks and Wildlife Service (part of DECCW)

Aboriginal Heritage Impact Permit (AHIP) under Section 90 of the National Parks and Wildlife Act 1974 if any sites would be impacted.

Department of Environment, Climate Change and Water (DECCW)

A species impact statement would be required to be prepared if there is a significant impact on threatened species listed under the Threatened Species Conservation Act 1995 or alternatively participation in the biobanking scheme.

Threatened species, endangered ecological communities and populations are considered during the Part 3A environmental assessment.

Department of the Environment, Water, Heritage and the Arts (DEWHA):

Approval under the Environment Protection and Biodiversity Conservation Act 1999 if matters of National Environmental Significance are significantly impacted and therefore become a controlled action.

Approval under the Environment Protection and Biodiversity Conservation Act 1999 if matters of National Environmental Significance are significantly impacted and therefore become a controlled action.

Crown Lands Act 1989

Approvals if Crown reserves are impacted.

Approvals if Crown reserves are impacted.



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It is also noted that any land impacted would need to be assessed as to whether there are native title issues.

5.9 Grant Funding Acquisition of funding for this project may depend but not limited to the following factors:

� Reasons for application, e.g. explanation of the necessity of a brand new water storage, the advantages of an on-stream water storage system compared to an off-stream water storage system, etc;

� Initiative and cooperation of the dam owner to satisfy relevant Acts and guidelines as

set by the relevant authorities, e.g. engagement of stakeholders, development of environmental protection strategies, potential social and economical benefits, etc;

� Timing and timeframe of proposed construction works;

� Capital and annual operation / maintenance costs;

� Opinions of potential funders;

� Political and Financial positions of potential funders.

NSC should be prepared for lengthy approval processes (in the order of 5 years) as on-stream water storage systems are associated with more risks compared to off-stream storage systems such as environmental flow releases, drought issues, etc.

5.10 Catchment Area Management NSC must develop and execute Catchment Area Management Plans for the chosen dam site prior and post construction works. The plans are required to identify, rectify and manage any activities that may impact on the security of waters to be stored in the dam. Further Studies

� Water Balance Analysis;

� Drought Contingency Policies;

� Catchment Management Plan.

5.10.1 Adequacy of Required Runoff To date, D&C has identified the potential locations and configurations of the proposed dam according to NSC’s current requirements and constraints. The subsequent activity required from NSC would be their analysis into future water usage demands for the population and areas to be served by the proposed dam, e.g. ML per day required from the proposed dam to be delivered to the Bowraville Water Headworks for the next 30 years. Subsequent to this, a Water Balance Analysis would follow to analyse if the proposed dam has the capacity to meet these future demands. The Water Balance Analysis would be simulated on historic rainfall data for the proposed dam’s total catchment to examine the potential water yield available for average, wet and dry years. NSC may then develop drought contingency strategies to be implemented for the dry



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seasons should water storage volumes in the proposed dam become a problem for the demand.

5.10.2 Water Pollution Issues After the purchase of private land in the potential dam inundation zone, NSC must ensure all potential sources of pollution are eliminated. For example, all sewerage systems (mains and or septic systems) must be decommissioned, cleared / cleaned and removed / capped to avoid contamination of the waters to be stored by the proposed dam. Also, any former dip sites or fuel storage should be identified. Once the catchment boundaries have been defined, NSC must implement regulations and enforcements to manage illegal activities such as illegal waste dumping etc to prevent deliberate contamination of runoff and stored waters. Natural contaminations such as algae, sedimentation, wildlife wastes, etc may be accommodated but only after thorough environmental and water quality assessments have been carried out for the whole potential catchment.



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6 COST ESTIMATES All revised and associated costs for the dam construction and operation / maintenance works for both sites are summarised in tables below.

Table 8 Total Construction Cost Estimates

League Creek Site Gravelly Creek Site Dam Construction Cost^ $ 23,192,800 $ 39,400,800 Water Delivery Pipeline

Construction Cost# $ 79,045,500 $ 49,019,200

Total Construction Cost $ 102,238,300 $ 88,420,000 Notes*** All costs estimated according to 2010 pricing;

All construction costs exclude NSC’s purchase of private land and establishment of pipe easements. ^ Refer to Appendices 1 and 2 for the cost breakdowns; # Refer to Appendices 3 and 4 for the cost breakdowns. Based on delivery rate of approx. 17 ML/day.

Table 9 Total Operation and Maintenance Cost Estimates

League Creek Site Gravelly Creek Site Annual Operating / Maintenance Cost:

1. Pipeline; 2. Destratification; 3. Dam Monitoring.

1. $ 20,000; 2. $ 20,000; 3. $ 10,000.

1. $ 15,000; 2. $ 20,000; 3. $ 10,000.

Total Annual O&M Cost $ 50,000 $ 45,000 Notes*** All costs estimated according to 2010 pricing.

Table 10 Potential Fishway Cost Estimates

League Creek Site Gravelly Creek Site Potential Fishway Cost#:

� Earthworks for white

water channel, downstream dissipater pool, etc;

� Civil works on dam for gate installation or equivalent;

� Installation of fish trap chamber, fish lift, etc;

� EIS, Aquatic Studies; � Detail Design and

Specifications.

Up to $ 26 Million Up to $ 22 Million

Potential Annual O&M Cost $ 30,000 $ 25,000 Notes*** All costs estimated according to 2010 pricing;

All construction costs exclude NSC’s purchase of private land and establishment of pipe easements. # Cost estimate based on D&C’s past experience on projects of similar magnitudes e.g. fishway at Tallowa Dam. Detail costs are highly sensitive and dependent on environmental, social and economical requirements. Potential configuration and cost would be examined during the concept design phase.



17

7 CONCLUSION The preferred water delivery method from the two potential dam sites to Bowraville’s existing Water Headworks was determined to be via a pipeline system. Alternatively, water delivery via Nambucca River was assessed to involve more environmental and security issues and is also anticipated to be of higher costs. Risks associated with on-stream water storages and water delivery systems were examined and the major issues of concern identified for NSC include:

� Amount of land acquisition and feasibility of purchase; � Presence of protected species in potentially affected areas by construction and post-

construction activities;

� Presence of land of heritage significance;

� Release of environmental flows down Nambucca River;

� Potential necessity of fishways. The following table summarises the major results of the analysis carried out.

League Creek Dam Gravelly Creek Dam Dam Inundation Area 21.4 ha 105.3 ha

% of Private Ownership of Dam Inundation Area 99.4 % 100 %

Number of Properties to be Inundated by Dam 5 20

Length of Delivery Pipeline 34 km 20 km % of Pipeline to be Installed

on Pipe Easements 33 % 50 %

Total Dam and Pipeline Construction Cost $ 102.2 Million $ 88.4 Million

Total Annual O&M Cost $ 50,000 $ 45,000 Potential Fishway Cost Up to $ 26 Million Up to $ 22 Million

Potential Fishway Annual O&M Cost $ 30,000 $ 25,000

Results of further studies and opinions of regulating authorities / potential funders will ultimately dictate the decision on the most suitable dam site. The necessity, configuration and cost of the potential dam’s fishway would also be subsequently addressed in detail.



18

REFERENCES

� NSW Department of Commerce – Dams and Civil Section, Construction of On Stream

Storage – Inspection of Dam Sites and Preparation of Cost Estimates for Staged

Construction – Report No. DC07087, June 2007.



FFIIGGUURREESS

Oakes State Forest

Buckra Bendinni State Forest

Proposed League Creek Dam

Proposed Gravelly Creek Dam

Nambucca River

Irishman State Forest

Argents Hill

Potential Pipeline Route

214,225

Legend

LC pipeline

RL 155 mAHD Inundation A (m2)Note*** Inundation area based on 10 m contours

FIGURE 1a - League Creek Dam Site Plan 0 1,600 3,200 4,800 6,400800Meters

�)

Bowraville Water Headworks

Bowraville



Nambucca River

Irishman State ForestMissabotti Creek

Missabotti

Argents Hill


Legend

LC pipeline


FIGURE 1b - League Creek Dam Site Plan 0 1,600 3,200 4,800 6,400800Meters

Oakes State Forest

Gaddess Ridge Rd

League Creek

League Creek Rd

Proposed Gaddess Ridge Rd Diversion

Proposed League Creek Dam

Nambucca River Rd

Proposed Nambucca River Rd Diversion

Road (Unnamed)

214,225

Legend

LC pipeline

RL 155 mAHD Inundation A (m2)

State Owned Land

Private LandNote*** Inundation area based on 10 m contours

FIGURE 2 - League Creek Dam Inundation Area 0 150 300 450 60075Meters

�)


Bowraville



Nambucca River

Irishman State ForestMissabotti Creek

Missabotti

Argents Hill


1,053,301

Legend

GC pipeline


FIGURE 3 - Gravelly Creek Dam Site Plan 0 1,600 3,200 4,800 6,400800Meters

Gravelly Creek


Bottle Gully

Bottle Creek Rd


Road (Unnamed)

Proposed North Arm Rd Diversion

Nambucca River

North Arm Rd

1,053,301

Legend

GC pipeline

RL 75 mAHD Inundation A (m2)

State Owned Land

Private LandNote*** Inundation area based on 10 m contours

FIGURE 4 - Gravelly Creek Dam Inundation Area 0 330 660 990 1,320165Meters

�)

Lower North Arm Rd

Borefield Rd


Bellingen Rd

Nambucca River

Proposed Pipeline

FIGURE 5 - Plan of River Crossing and Existing Headworks 0 220 440 660 880110Meters

Legend

State Owned Land

Private Land



AAPPPPEENNDDIICCEESS

APPENDIX 1NAMBUCCA SHIRE COUNCIL - LEAGUE CREEK ON-STREAM WATER STORAGE - COST ESTIMATE, July 2010Staged Construction for RCC Type Dam

Quantity CostPreliminaries

Access Roads:New km $200,000 3.4 $680,000

Upgrading km $50,000 10 $500,000

Establishment/Disestablishment Item 1 $200,000Clear Storage Area Ha $2,500 22 $55,000

Sub Total $1,435,000

DIVERSION WORKS

Dewatering and Cofferdamming Item 1 $200,000Excavation for Diversion m3 $25 1,800 $45,000Steel Conduit Concrete Encasement m $4,000 240 $960,000


DAM WALLStripping m3 $6 18,000 $108,000

Excavation m3 $15 3,500 $52,500

Foundation Preparation/Clean Up m2 $20 4,000 $80,000

Drill, Supply and Grout Anchor Bars m $50 500 $25,000Grouting m $220 4,600 $1,012,000RCC in Dam Wall m3 $120 30,000 $3,600,000

RCC In Flip Bucket/Apron Slab m3 $120 1,800 $216,000

Reinforced Concrete in Wall Face and Apron Slab m3 $1,500 2,500 $3,750,000

Downstream Protection Item 1 $80,000Guardrails and Crest Pavement Item 1 $100,000


INTAKE TOWERExcavation for Tower Base and Bridge Piers and Abutment m3 $10 1000 $10,000

Tower Base Reinforced Concrete m3 $1,000 100 $100,000

Tower Stem Reinforced Concrete m3 $1,200 120 $144,000

Tower Deck Reinforced Concrete m3 $1,500 35 $52,500

Tower Bridge Item 1 $250,000

Trashracks/Bulkhead Item 1 $80,000Metalwork Item 1 $80,000

Portal Frame and Crane Item 1 $150,000Sub Total $866,500

OUTLET WORKSExcavation m3 $10 800 $8,000Valve Block Reinforced Concrete m3 $1,200 150 $180,000

Valves and Pipework Item 1 $1,200,000Metalwork Item 1 $300,000


MISCELLANEOUS

Landscaping Item 1 $80,000

Fencing Item 1 $60,000

Sub Total $140,000

TOTAL PRIME COST $14,358,000Additional Site Investigation 1 Item $80,000 $80,000

EIS 1 Item $120,000 $120,000Seismic/Hazard Evaluation 1 Item $20,000 $20,000Detailed Design and Specifications (10% of total Prime Cost) $1,435,800

Construction Management (10% of total Prime Cost) $1,435,800Contingencies (40% of total Prime Cost) $5,743,200

TOTAL COST $23,192,800

Description Unit RateConstruction of dam to FSL at RL 155.0 mAHD (5,500 ML)

G:\IS\Watertec\Dams_civ\PROJ\Nambucca\Nambucca_Est.xls

APPENDIX 2NAMBUCCA SHIRE COUNCIL - GRAVELLY CREEK ON-STREAM WATER STORAGE - COST ESTIMATE, July 2010Staged Construction for Zoned Earthfill Type Dam

Quantity CostPreliminaries

Access Roads:New km $200,000 3.8 $760,000

Upgrading km $50,000 10 $500,000

Establishment/Disestablishment Item 1 $200,000Clear Storage Area Ha $2,500 106 $265,000


DIVERSION WORKS

Dewatering and Cofferdamming Item 1 $200,000Excavation for Diversion m3 $25 2,200 $55,000Steel Conduit Concrete Encasement m $4,000 180 $720,000

Sub Total $975,000

EMBANKMENTStripping m3 $6 65,000 $390,000

Excavate Core Trench m3 $15 6,500 $97,500

Foundation Preparation (core trench only) m2 $20 2,300 $46,000

Grout Cap m3 $550 600 $330,000

Grouting m $220 4,200 $924,000Borrow Area Excavation m3 $6 36,000 $216,000

Core Material, win, haul, place and compact m3 $15 36,000 $540,000

Filter Material , win, haul, place, compact and test m3 $80 12,000 $960,000

Shell, Place and Compact m3 $10 130,000 $1,300,000

Rip Rap, deliver and place m3 $60 8,500 $510,000

Instrumentation Item 1 $100,000Guardrails and Crest Pavement Item 1 $100,000


SPILLWAYExcavation m3 $10 200,000 $2,000,000Drill, Supply and Grout Anchor Bars m $50 12,000 $600,000Floor, Walls, Sill, Basin Reinforced Concrete m3 $1,500 7,200 $10,800,000Bridge Over Spillway Item

Stilling Basin Protection Item 1 $100,000

Sub Total $13,500,000

INTAKE TOWERExcavation for Tower Base and Bridge Piers and Abutment m3 $10 1000 $10,000

Tower Base Reinforced Concrete m3 $1,000 100 $100,000

Tower Stem Reinforced Concrete m3 $1,200 120 $144,000

Tower Deck Reinforced Concrete m3 $1,500 35 $52,500

Tower Bridge Item 1 $250,000

Trashracks/Bulkhead Item 1 $80,000Metalwork Item 1 $80,000

Portal Frame and Crane Item 1 $150,000Sub Total $866,500

OUTLET WORKSExcavation m3 $10 800 $8,000Valve Block Reinforced Concrete m3 $1,200 150 $180,000

Valves and Pipework Item 1 $1,200,000Metalwork Item 1 $300,000


MISCELLANEOUS

Landscaping Item 1 $100,000

Fencing Item 1 $120,000

Sub Total $220,000

TOTAL PRIME COST $24,488,000Additional Site Investigation Item $80,000

EIS Item $120,000Seismic/Hazard Evaluation Item $20,000Detailed Design and Specifications (10% of total Prime Cost) $2,448,800



Description Unit RateConstruction of dam to FSL at

RL75.0 mAHD (5,500ML)


APPENDIX 3NAMBUCCA SHIRE COUNCIL - LEAGUE CREEK ON-STREAM WATER STORAGE - COST ESTIMATE, July 2010Pipeline from Dam to Bowraville Headworks

Quantity CostPRELINMINARIES

Establishment/Disestablishment Item 1 $200,000Land Clearance for Route Ha $2,500 11 $27,500

Sub Total $227,500

PIPEWORKS1,067 OD SCL RRJ Pipe with 450 mm cover (supply) m $1,150 36,000 $41,400,0001,067 OD SCL RRJ Pipe with 450 mm cover (installation in rock) m $650 10,000 $6,500,0001,067 OD SCL RRJ Pipe with 450 mm cover (installation in OTR) m $510 16,000 $8,160,000Opencut Excavation & Restoration Pipe Road Crossing with 1 m cover Item $16,450 25 $411,250SCL / HDPE Pipe for HDD River crossing with installation m $4,400 65 $286,000Supply of Stop Valves No. $60,000 5 $300,000Installation of Stop Valves No. $6,500 5 $32,500Construction of SCL Pipe fittings, air / scour valves and thrust blocks including connection into Bowraville Headworks

Item $3,425,385

Sub Total $60,515,135


Detailed Design and Specifications (5% of total Prime Cost) $3,037,132



Description Unit RatePipeline Installation from

League Creek to Bowraville


APPENDIX 4NAMBUCCA SHIRE COUNCIL - GRAVELLY CREEK ON-STREAM WATER STORAGE - COST ESTIMATE, July 2010Pipeline from Dam to Bowraville Headworks

Quantity CostPRELINMINARIES

Establishment/Disestablishment Item 1 $200,000Land Clearance for Route Ha $2,500 4 $10,000

Sub Total $210,000

PIPEWORKS1,067 OD SCL RRJ Pipe (supply) m $1,150 20,000 $23,000,0001,067 OD SCL RRJ Pipe with 450 mm cover (installation in rock) m $650 10,000 $6,500,0001,067 OD SCL RRJ Pipe with 450 mm cover (installation in OTR) m $510 10,000 $5,100,000Opencut Excavation & Restoration Pipe Road Crossing with 1 m cover Item $16,450 10 $164,500SCL / HDPE Pipe for HDD River crossing with installation m $4,400 65 $286,000Supply of Stop Valves No. $60,000 4 $240,000Installation of Stop Valves No. $6,500 4 $26,000Construction of SCL Pipe fittings, air / scour valves and thrust blocks including connection into Bowraville Headworks

Item $2,118,990

Sub Total $37,435,490


Detailed Design and Specifications (5% of total Prime Cost) $1,882,275



Description Unit RatePipeline Installation from

Gravelly Creek to Bowraville


NSW Department of Services, Technology & Administration Dams and Civil Section Level 13 West, MCKell Building 2 – 24 Rawson Place Sydney NSW 2000 T 02 9372 7808 F 02 9372 7822 TTY 1300 301 181 www.services.nsw.gov.au

Nambucca Water Supply Investigation of On-stream …NSW Public Works – Dams and Civil Section...

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