Copeton Dam is a major clay core and rock fill embankment dam with nine radial gates and a gated concrete chute spillway across the Gwydir River upstream of Bingara in the New England region of New South Wales. The dam's purpose includes environmental flows, hysdro-e;ectric power generation, irrigation and water supply. The impounded reservoir is called Lake Copeton.
In 2007, it was decided the dam would need an upgrade for safety reasons. This was completed in recent years. Unexpected erosion of hard, sound, unweathered granite in the unlined spillway discharge channel was caused by rock failure under high in-situ compressive stress. This type of erosion due to high in-situ stress has apparently not been reported elsewhere in the worl
Remedial works involved building a training wall to separate the original single spillway into a service spillway and a secondary (emergency) spillway. A concrete slab, anchored to the underlying rock was constructed in the floor of the main scour channel to provide some additional protection on those rare occasions when the secondary spillway will discharge water over this area. The smaller, more frequent flood events will be discharged through the service spillway onto more scour resistant rock.
The eastern Inverell and western Grafton region is a geologically diverse part of the New England region. There is a wide range of felsic volcanic rocks.
The Inverell survey area in the New England Orogen hosts known mineralisation — including granite-related cassiterite, tungsten, molybdenum, gold, silexite (quartz–topaz greisen) and silver-rich lead, zinc and copper; sea floor manganese oxide–rhodonite and copper–lead–zinc; and alluvial deposits of tin, sapphires and diamonds. There is a relationship between the structurally controlled granite-related mineralisation and various fault and fracture sets, and between the occurrence of sapphires and Tertiary volcanic rocks.
The Inverell area also encompasses rocks of the southern New England Orogen (NEO) The region consists of complexly deformed rocks that are unconformably overlain by felsic volcanic rocks, a heritage of the regions volvanic activity. The complexly deformed rocks are Early Carboniferous and Early Permian, shallow to deepwater marine sandy and muddy sedimentary rocks, minor volcanic rocks, conglomerate, chert and jasper, and rare limestone (Korsch 1977; Wood 1982; Cozens 1984; Aitchison et al. 1988). These rocks have undergone low-grade regional metamorphism, meaning there have been significant changes over the years.
Tertiary volcanic and intrusive rocks and sediments occur extensively throughout the survey area. The volcanic rocks are predominantly basaltic lavas ranging in age from about 36 to 18 Million years.
To log this cache, go to the listed coordinates and email me the answers to these questions. You can immediately log the find and if there are any problems I will contact you.
Standing at the listed co-ordinates and facing NW (toward the rock face and the dam wall), provide the answers to the following questions:
Q1 What are the two main rock colours which are most prominent. Can you comment on the most likely cause of the colour variations?
Q2 Although the main layers of the rocks are horizontal, at what angle are the rock fissures through the rock face. Can you comment on how those fissures were likely to have been formed?