Eildon Dam Wall EarthCache

Cache Information:

Cache #: 3

Location: Eildon Dam Wall

Access: All Vehicles, 24/7

Facilities: Parking, Toilets, Boat Ramp, Lookout Tower

Details:

This EarthCache is located at the site of the 'Eildon Dam Wall', a dam constructed on the Goulburn River at Eildon in the 1950s to harness water for irrigation and power generation. You will need to visit this location to source information to complete this EarthCache.

Additional Information:

This EarthCache illustrates how earth and rock can be used to benefit the agriculture industry, supply arid inland areas of our state with water, produce green energy, act as a backup to the City of Melbourne's water supply and support the communities that surround the lake with huge tourism potential. Its construction also enables us to investigate the sedimentary layers of the earth which were left exposed by the massive earthworks.

History:

Eildon Dam Wall at Eildon is Victoria's most spectacular and accessible dam wall of its size. The main dam wall is constructed of thick layers of natural materials. These include: (1) Clay Core, (2) Sandy loam, (3) Rocks & Gravel, (4) Rocks. The larger heavy rocks are known as bluestone (basalt or olivine basalt) and were used in mass to build the wall. It was sourced locally from the northern and southern ends of the wall.

The River:

The Goulburn River is Victoria's largest and longest river at 654 kilometres. It has its source from the Woods Point and Jamieson catchment area in the Great Dividing Range. From here it winds through Central Victoria before meeting the mighty Murray River near Echuca.

The Water:

The Goulburn water catchment area above the Eildon Weir is around 2,000 square kilometres and provides water to the dam for irrigation, electricity generation and Toursim. It holds 3,334,000 Megalitres at full capacity - more than Sydney Harbour.

The Dam Wall:

The dam wall is constructed primarily of of four layers of natural materials. These are:

1. Clay Core

   Clay is a fine-grained type of soil made up of tiny particles of organic matter, metal oxides and earth. When wet it provides an almost impermeable barrier to water.

2. Sandy Loam

   Loam is a concentration of sand, silt and clay. Sandy loam has a higher concentration of sand and is ideal for construction due to its stability and resistence to expansion and contraction.

3. Rock & Gravel

   River rock in the form of gravel was sourced from other areas of the Goulburn River rich in gravel and used in the construction of the Eildon Dam Wall. One such location was the gravel works formerly located at Acheron. These gravel rocks were worn smooth by the constant friction of the water running over it. Small rock was also used in the construction of the wall and was generally sourced from the construction site and crushed. Most of this rock was bluestone.

4. Rock

   The larger heavy rocks are known as bluestone (basalt or olivine basalt) and were used en mass to build the wall. It was sourced locally from the northern and southern ends of the wall. Bluestone was used at the site due to its durability and weight. A well known example of the durability of bluestone is at the prehistoric monument known as Stonehenge in England where the rock pillars remain sturdy after more than three thousands years. In Victoria, many of the buildings constructed in the early 1800 were also of made from bluestone blocks.

Irrigation:

Thanks to the construction of the dam, water flowing from Eildon Weir is diverted into a system of gravity fed channels that themselves feed smaller irrigation channels. These allow an agricultural industry to flourish in arid areas of the State.

Electricity:

Thanks to the construction of the dam, electricity is generated at Eildon Weir. The electricity is fed into the Victorian power grid and is referred to as 'Green Energy' as it is generated from the flow of water which produces no greenhouse gasses.

Emergency City Water:

Thanks to the construction of the dam, water can be diverted from the Goulburn River below the dam in times of drought and transferred to the city of Melbourne.

Tourism:

Thanks to the construction of the dam, tourism is now a major industry for townships around the lake.

Logging the EarthCache:

To gain permission to log a find on this EarthCache, please answer the questions below and email your answers to us at the address at the bottom of the page:

1. What is the length of the earth embankment?

2. On the centre top memorial plaque labeled 'Eildon Dam', what height is the bank?

3. What is the name of the predominant rock visible along both sides of the wall?

4. By looking at the exposed layers of the earth's crust on Mount Sugarloaf (at the northern end of the wall) or at the spillway walls (at the southern end of the wall) how would you describe this areas geology?

Email your answers to:
cacher2011ah@gmail.com

I will respond as soon as possible. While you wait, why not take a picture of yourself at the wall to add to your log.