What is groundwater?
How does water become groundwater?
What is an aquifer?
Does groundwater move?
What is contamination?
What is a plume?

• What is groundwater?

Groundwater is any water contained below the earth's surface. It includes moisture contained inside soil and rock, and water accumulating in gaps between soil particles and in cracks in the rock.

If groundwater comes into contact with rocks containing a lot of salt, the salt can dissolve into the groundwater making it salty.

The groundwater under the Altona Plant is in contact with basalt rock, which contains a lot of natural salts. As a result the groundwater is too salty for domestic, irrigation and most industrial uses. The EPA has, however, identified that it may be suitable for stock watering.

• How does water become groundwater?

Groundwater begins with surface water seeping into the ground. Some of this water is stored by the soil and used by plants, and some evaporates from the soil surface. Water which cannot be stored in the soil moves deeper into the ground.

At the Altona site, groundwater fills the cracks and voids in the basalt rock that lies under the site. Some of this groundwater came from rain falling in the local area. The rest is from groundwater moving through the basalt from other areas.

• What is an aquifer?

An aquifer is a zone of rock or soil which is saturated with water and through which water can easily move. An aquifer is created when all the cracks and voids in soil and rock are filled with water.

The basalt rock under the Altona site contains upper and lower aquifers. These are separated by a thin layer of clay. The upper aquifer is 10 to 20 metres below ground level. The lower aquifer is 20 to 40 metres below ground level.

• Does groundwater move?

Like surface water, groundwater flows towards the lowest place. The regional groundwater movement in the basalt under the Altona Plant is towards the south and south-east. Monitoring indicates the groundwater movement is very slow and the direction of movement remains the same.

• What is contamination?

The Victorian EPA defines contamination as "a change in water quality that produces a noticeable or measurable change in its characteristics" [State Environment Protection Policy (Groundwaters of Victoria) 1997].

Contamination of soil or groundwater can occur through any industrial, residential, agricultural or transport activity where inadequate safeguards have been used to contain spills and leaks.

• What is a plume?

A groundwater plume is an area of groundwater in which contaminants are moving with the general flow of groundwater.

The flow of groundwater under the Altona Plant has resulted in a plume of contaminated groundwater extending beyond the boundaries of the site.

Altona Properties Pty Ltd.
Copyright © 2011 Altona Properties, except where indicated.
URL: www.altonagroundwater.info
last modified:07-05-2007 | next update due May 2011
Send comments or suggestions to Mark Wloch, mwloch@pb.com.au