Tomagos & Anna Bay Sandbeds
Tomago Sandbeds
The Tomago Sandbeds is an underground water source that provides about 20% of the lower Hunter’s drinking water. The sandbeds are parallel to the coast between Newcastle and Port Stephens, starting at Tomago and extending north-east for 25 kilometres to Lemon Tree Passage.
An extensive system of underground bores and vacuum stations draws raw water from the sandbeds and pumps it to Grahamstown Water Treatment Plant. The maximum storage is about 100,000 megalitres of water above sea level, of which Hunter Water can access about 60,000 megalitres with existing infrastructure from a portion of Tomago Sandbeds covering about 100 square kilometres.
About the Tomago sandbeds
The sandbeds are a natural geological feature, consisting of a layer of highly permeable fine grained sands underlain by impervious clay and rock. The thickness of the sand layer reaches a maximum of 50 metres, but on average is 20 metres deep. The source of the water is the rainfall that lands directly on the sand surface. While a proportion of the rainfall is lost to plants and evaporation, sufficient water is stored in the sand to provide a viable and significant source of water for ongoing extraction.
The sandbeds are strategically important for both ongoing and backup water supply. Ongoing supply from the sandbeds reduces the load on surface water sources (Chichester Dam and Grahamstown Dam) and thereby allows greater overall yield from the total water supply system. This large storage volume can also be used as a reserve supply during drought, and is available as a backup supply in the event of water quality issues in the surface storages.
Tomago Sandbeds specifications
| Capacity |
60,000 megalitres |
| Catchment |
100 square kilometres |
| Average Depth |
20 metres |
| Average water table full |
4.8 metres ASL (above sea level) |
| Average water table empty |
1.8 metres ASL |
| Bore stations |
14 |
| Average ground elevation |
8 metres ASL |
| Average Daily Supply |
45 megalitres |
| Peak Daily Supply |
110 megalitres |
| Vacuum stations |
10 |
| No vacuum spearpoints |
360 |
| No individual bores |
157 |
The history of Tomago Sandbeds
- 1916: Water Reserve declared over 25km2 with Hunter Water assigned as trustee.
- 1939: Construct Vacuum Stations 1-2, spray basin, 500mm pipeline to Newcastle.
- 1940: Construct Tomago Vacuum Stations 3 and 4.
- 1941: Williamtown RAAF base established, Tomago Catchment Area gazetted 100km2.
- 1942: Construct Vacuum Stations 5-15, second spray basin, 900mm pipeline.
- 1946: Start water treatment by lime/alum dosing into delivery pipelines with sedimentation into Waratah Reservoir and later North Lambton Reservoir.
- 1953: Construction of Tomago Bore Stations 16 to 20.
- 1957: Abandoned due to poor water quality.
- 1959: Tomago No. 1 Water Treatment Plant opened.
- 1965: Tomago No. 2 Water Treatment Plant opened.
- 1972: Heavy mineral sand mining commenced operations leading to the relocation and eventual abandonment of Station 6.
- 1973: Tomago No. 3 WTP opened (also known as Grahamstown WTP) to treat water from both Tomago Sandbeds and Grahamstown Reservoir.
- 1992: Construction of Bore Stations 21 to 23.
- 1999: Heavy mineral sand mining operations cease.
- 2000: Construction of Bore Stations 24 to 27.
Geological history of Tomago Sandbeds
The Tomago Sandbeds were formed during the Pleistocene era with the original sand deposits occurring up to 250,000 years ago. Rising sea levels created a large bay extending from Newcastle to Port Stephens. The Hunter and Karuah Rivers both flowed into the bay and deposited large volumes of sand. A combination of wave and wind action spread the sand along the coastline and formed the series of shallow dunes that make up the Tomago Sandbeds.
The Tomago Sandbeds are no longer mobile and have evolved into a mature and well vegetated landform. Over time rainfall landing on the sandbeds has washed out any remnants of sea salt leaving the deep sand system full of fresh water.
The North Stockton Sandbeds, which form the current coastline between Newcastle and Port Stephens, were deposited much more recently than the Tomago Sands. They overlie the eastern extremity of the Tomago Sands and were deposited in the Holocene era (i.e. the last 10,000 years).
Other groundwater resources
In addition to the Tomago Sandbeds, there are three other smaller groundwater schemes operated by Hunter Water:
- Lemon Tree Passage water treatment plant (link to 7.3.4.3) draws water from the eastern edge of the Tomago Sandbeds to supply Karuah and the Tilligerry Peninsula
- Glovers Hill (link to 7.3.4.5) and Anna Bay (link to 7.3.4.4)treatment plants draw water from the Anna Bay Sandbeds to supply towns along the Tomaree Peninsula.
About the Anna Bay sandbed system
The system consists of 21 bores within the Anna Bay, Glovers Hill and Nelson Bay sandbeds. Extracted water is treated at the Anna Bay and Glovers Hill Water Treatment Plants, each with a capacity to treat and deliver up to 12 megalitres per day.
The sustainable yield of the sandbed system is estimated to be around 7.0 megalitres per day over the longer term. The aquifer can, however, be used to supply much higher flow rates to meet peak day demands, provided that average extraction is kept at or below the sustainable yield. To compensate for high pumping rates in peak periods, treatment rates at the water treatment plants are reduced in non- peak periods. A valve in the bore fields splits the supply system in two. The Anna Bay bores pump water to the Anna Bay Treatment Plant whilst the Fingal Bores and Nelson Bay Bores pump water to the Glovers Hill Water Treatment Plant.
The Anna Bay bores deliver water to the Anna Bay Water Treatment Plant. They generally operate with a delivery pressure of around 10-20 metres. The Anna Bay bores are located in a deep sand aquifer. The capacity of some bores is currently constrained by screen diameter and length, and/or by installed pump capacity.
About the Tomago to Tomaree Pipeline
The Tomago to Tomaree pipeline supplies treated water from the Tomago/Grahamstown system. This pipeline, commissioned in 2002, was built predominantly to service growth and limit groundwater extraction from the aquifers in line with regulatory requirements.
The 38 kilometres 300mm diameter pipeline delivers water from Grahamstown water treatment plant to a 300mm water main at the intersection with Salamander Way, Salamander Bay. Two intermediate water pumping stations (WPS) are located along the pipeline to provide sufficient pressure to the system to deliver water to the Salamander Reservoir. The first is near Williamtown (Williamtown WPS No. 2) and the second near Bobs Farm (Bobs Farm WPS No. 1). The pipeline supplies around 7 megalitres per day with both Williamtown WPS No. 2 and Bobs Farm No. 1 Operating.
Tilligerry Peninsula
The Tilligerry area (including the townships of Lemon Tree Passage, Karuah and Tanilba Bay) is serviced solely by the Lemon Tree Passage water treatment plant. This plant receives water from the north-eastern end of the Tomago Sandbeds system. A closed valve on the Tomago raw water pipework marks the division between bores supplying the Grahamstown treatment plant and Lemon Tree Passage. Extraction from the borefield is currently limited by the capacity of the Lemon Tree Passage plant, which can treat up to 5 megalitres per day of raw water.
The figure below shows a simplified system schematic of the Tomaree and Tilligerry water supply systems, including the reliable capacity of various units.
