Tomago Sandbeds

Overview

Catchment area

109km2

Annual rainfall

1125mm

Accessible aquifer volume

60,000ML

Areas supplied

Lower Hunter, up to approximately 20% of volume

Land use breakdown of catchment

44% State Conservation Area, 21% Hunter Water freehold, 21% industrial, 8% Defence (RAAF Base), 3% Bombing Range, 3% rural residential

Public Access  To protect the quality of the Tomago Sandbeds drinking water source, public access to land within the catchment is restricted. This includes:
  • No public access into Tilligerry State Conservation Area (SCA) which is a reserve that is fully contained within the catchment
  • No public access to any Hunter Water owned land
For further information on access restrictions click here

The Tomago Sandbeds is an underground water source that operates as a back up to Grahamstown Dam and can provide about 20 per cent 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.

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.

History

  • 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

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).

The Catchment

The Tomago Sandbeds lie parallel to the coast between Newcastle and Port Stephens, beginning at Tomago and extending north-east for 25 kilometres to Lemon Tree Passage. Below the Sandbeds is an aquifer (or underground water source) consisting of clay and rock layer underneath fine sand. The sand is on average 20 metres deep, but reaches a depth of 50 metres in places.

Rain water lands directly on the sand surface to replenish the aquifer, with some of the water being lost to plants and evaporation. The water table is approximately 4.8 metres above sea level when full and 1.8 metres above sea level when empty.

Extraction of water from the aquifer

There is a network of more than 500 individual bores covering 100kmfrom Lemon Tree Passage west to Tomago. After treatment at Grahamstown Water Treatment Plant, water from the western Tomago Sandbeds is piped to consumers in Newcastle and the lower Hunter regions.

To the east of Lemon Tree Passage, a smaller volume of water is extracted and treated by the Lemon Tree Passage Water Treatment Plant and piped to Karuah, Lemon Tree Passage and Tanilba Bay.

The importance of the Sandbeds to the supply system

The Sandbeds are strategically important for both ongoing and backup water supply. The ongoing supply from the sandbeds reduces the load on surface water sources and thereby allows greater overall yield from the total water supply system. The large storage volume can be used as a reserve supply during drought and is available as a backup supply in the event of water quality issues in the dams.

Water quality and catchment health

Water from the Tomago aquifer good quality. Sand itself is a good filter of contaminants and therefore pollutants do not travel quickly and are normally inactivated. In addition, most of land in the catchment areas is a protected  area which preserves drinking water quality.

Hunter Water works with land use planners and industry in this area to protect the Sandbeds as a natural resource.

Public Access

To protect the quality of the Tomago Sandbeds drinking water source, public access to the land within the catchment is restricted. This includes:

  • No public access into Tilligerry State Conservation Area (SCA) which is a reserve that is fully contained within the catchment
  • No public access to any other Hunter Water owned land

See Tomago Sandbeds Access Restriction Map showing restricted area.

For further information on access restrictions click here