THE PROJECT

During the Miocene, over 150 volcanic pipes erupted in the West Kimberley Province; about fifty of which intruded Permian and older sediments, collectively forming the Ellendale Diamond Field. 

The volcanic pipes are generally carrot-shaped at depth, but near the surface they frequently erupt outwards forming a wine-glass shaped structure. The pipes consist of magmatic lamproite cores with tuffaceous margins.  During the eruptive events, the country-rock sediments were super-heated and then, as they cooled, the sandstone adjoining the pipes recrystallised to form a hard quartzite rim, which commonly forms an aquiclude.

The tuffacous lamproite, containing the diamonds, is generally moderately to highly permeable and forms a significant aquifer. 

The Ellendale 4 and 9 pits were mined about 60 m depth, intersecting vuggy and highly permeable calcretised lamproite around the margins of the deposit.  Dewatering of the pits was achieved by 15 in-pit and ex-pit bores, depressurisation holes, and in-pit sumps.  The bores were designed and drilled under the supervision of Rockwater. 

Rockwater also designed and supervised the installation of a fresh water supply of 10 GL/annum from 23 bores of up to 300 m depth for processing of the ore by Dense Media Separation.  The project included extensive numerical modelling, and the preparation of hydrogeological assessments for mining proposals, licensing and submission to the EPA.

• Geological and geophysical interpretation
• Groundwater modelling for dewatering and water supply
• Field investigation and modelling reports
• H3 level of Hydrogeological Assessment
• Annual compliance monitoring reports

• RC exploratory drilling
• Mud-rotary production bores 
• Depressurisation bores
• Down-hole gamma and resistivity logging 
• Test-pumping
• Water quality sampling
• Stygofauna surveys
• Vegetation and groundwater spring monitoring and condition surveys