Geomechanics cc28 Central Road, Sunrella, Gauteng, South Africa PO Box 68063, Bryanston, South Africa, 2021

Tel: +27 11 451 7760 Fax: 086 663 3896

THE PROJECT

Metolong Dam and Water Supply Programconducts the geotechnical investigation for the

Metolong Dam wall in the South Phutiatsama RiverGeomechanics

MEETING THE CHALLENGES

OVERVIEWGeomechanics was contracted by Arcus Gibb to conduct the geotechnical investigation for the Metolong Dam wall in the South Phutiatsama River between October and December 2009.

The Metolong Dam and Water Supply Program in the Maseru District of Lesotho, forms part of the Lowlands bulk

water supply Scheme (LBWSS) to improve sustainable access to safe water in the lowlands areas of Lesotho and

to support economic growth.

The Metolong Dam is expected to provide an additional 75,000m³ of clean water for 385,000 people in Maseru and

the neighbouring towns of Mazenod, Roma, Morija and Teyateyaneng by 2013.

The dam is on the South Phutiatsama River adjacent to the villages of Ha Seeiso and Ha Makotoko about 35kms

from Maseru. It is 73 meters high, made of roller compacted concrete (RCC), has a crest length of 210 m and

contains 53 million cubic meters of water in its reservoir.

The geotechnical investigation conducted by Geomechanics required rotary core drilling for two alternative dam

wall sites, a diversion tunnel and three alternative quarry sites – 35 holes in all. Over 820 meters were drilled at

incline and over 300 meters of that required core orientation and Packer testing. The bulk of the holes for the

quarry and the river bed (25) had to be drilled through boulders.

Vehicle access to these platforms was impossible necessitating the use of helicopters with slings and long lines to move the drill rigs to their positions.

Of the 35 holes drilled, 26 were in difficult set-up locations with 8 being on the valley walls and 7 in the river bed. The steep valley sides required the building of horizontal drilling platforms in the valley walls.

S U C C E S S S TO RY

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Geomechanics cc28 Central Road, Sunrella, Gauteng, South Africa PO Box 68063, Bryanston, South Africa, 2021

Tel: +27 11 451 7760 Fax: 086 663 3896

THE OUTCOME

MEETING THE CHALLENGES

According to Barry Kruger, Site Manager, “The rain just poured down and within 24 hours our machines were submerged at the bottom of the river with no chance of rescue until the flood water subsided.

As soon as nature allowed, we refurbished the machine in the river valley and picked up the drilling where we left off.”

Even with the difficult access to drill sites and the delays caused by the weather, the project was completed within the allocated time and to the satisfaction of Arcus GIBB.

About GeomechanicsGeomechanics and Geomech Africa provide a drilling and testing service to the minerals exploration market as well as the Geotechnical and Civils industries and have over 20 years experience in Southern Africa.

Today, through a continued policy of upgrading of staff and equipment through training, replacement and maintenance, Geomechanics is one of the leaders in its field.Geomechanics cc is the founding company of the GeoGroup. The GeoGroup is a group of companies comprising Geomechanics, GeoCrush, GeoStone, GeoPlant, Geomech Africa, GeoPower Africa, Terra Power Solutions, GeoSolar Energy, GeoSolar and Green-a-Planet.These companies provide a range of services from geotechnical and exploration drilling, renewable energy and emergency power supply systems.

The essence of the GeoGroup is entrepreneurial initiative, integrity and honesty.

Helicopters were also needed to lower the rigs down to the valley floor where drilling was conducted from an elevated steel platform. This platform was built to operate in less than 300mm of water.

October 2009 was extremely wet with above normal rainfall experienced countrywide in Lesotho. Some places experienced rain fall 347% of normal for the month.

S U C C E S S S TO RY Metolong Dam and Water Supply Program

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Drill rigs submerged in the river after torrential rain caused the river to flood