Salty Sand EarthCache
Hidden : 10/17/2012
Difficulty:
1 out of 5
Terrain:
1 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:

The geology of the the Townsville area has had a major impact in the development of the city from its settlement in the mid 1800's. 

It was this sandy sedimentry layer that has played a major part to the history of a city. As with much of Australia drinking water has had a direct correlation to the settlement of new frontiers so in 1908 early settlers began to pond water in the Ross River and artificial daming had been started. This daming was more permantly constructed and was to become known as Gleeson's Weir. However one of the factors affecting salinity and salt water intrusion through the sand layer was its altitude above sea level. 

Wells were sunk into the sandy river bed both above and below Gleeson's Weir for water supply to the residents of Townsville. Due to the sandy pourous nature of the ground around the Ross River salt water often contaminated these wells. This unreliable water source did not support the further settlement of the area. 

The decision was made to constuct another weir (a "stop" weir) below Gleeson's Weir. Iron sheets later reinforced with concrete were driven into the sandy base of the river and a concrete capping was placed on raising the wall 1.2m above the sand level. This retained more water and kept salt water out of the sandy river beds providing useble water. This stop weir is known as Aplin's Weir. As a result in 1926 more wells were sunk along the riverbed above the Weirs to make use of fresh water trapped in the sedimentry sand banks.

With an expanding population and water still not very potable another weir was constructed. This time it was to be above the original Gleeson's Weir. In the early 1930's Black's Weir was completed.Substantial renovation after flooding was completed in 1934 but did not fill to capacity until 1936. This solved the water crisis of early Townsville up until the World War Two.



So from this history it can be seen that the sedimentry sand in the Townsville region had a significant and almost dooming influence on the city as it stands today. Quite a constast given the prominent granite and limestone topography that can surrounds Townsville.

To claim this cache you have to answer the following questions that can be observed at the cache coordinates.

Q.1. What specific type of rock is does the weir use to enhance its design and foundation?

Q.2. Can you estimate the distance from one side of the river to the other where the weir is?

Q.3  So an appreciation of the height of the porous sand layer can be made use your GPSr at the co-ordinates to give an altitude above sea level?

Whilst optional it would be appreciated if you can post a photo of you and you GPSr at the posted coordinates.

Additional Hints (No hints available.)



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