OLIFANTS RIVER WATER RESOURCES

DEVELOPMENT PROJECT (PHASE 2A)

DE HOOP DAM

SEPTEMBER 2012

ORWRDP PHASES• Phase 1 – Raising of Flag

Boshielo Dam (Completed in 2006)

• Phase 2A – Construction of the new De Hoop Dam

• Phases 2B to 2H

– Bulk Water Supply Pipelines to Mines & Municipalities

– Pump Stations

– Reservoirs

– Balancing Dams and Weirs

– TCTA implementing agency

• Municipalities distribute to communities

MAIN FEATURES OF THE DAM

1. Gross Storage Capacity [million m3] 347,4

2. Catchment Area [km2] 2 865

3. Approximate Length [m] 1 017

4. Approximate Height [m] 88

5. Total Excavation – Dam Footprint [m3] 415 000

6. Total Excavation – Quarry [m3] 1 300 000

7. Total Estimated Concrete Volume of the Dam [m3] 1 100 017

DE HOOP DAMMain Components:

• River Diversion

(Three (3) Stages)

• Outlet Works

• RCC NOC sections

• RCC Spillway (Stepped)110 m

• Total Length of Dam Wall: 1 017 m

• Access Roads

• River Gauging Structures

OUTLET WORKSThe Outlet Works will essentially comprise the following:

• Wet Well Intake Works on the upstream side comprising two bays each;

• Staggered Bell-Mouth Intakes;

• A Service Shaft will be provided in the concrete body of the dam immediately downstream of the Wet Well bays between the two vertical pipe stacks;

• This shaft will be used to remove the selector valves situated in pockets on either side of the shaft from the body of the dam;

• A Staircase Shaft as well as a Lift Shaft will also be provided;

OUTLET WORKS

RIVER GAUGING STRUCTURES• For operational purposes of the dam,

River Gauging Structures are required;

• Three (3) River Gauging Structures were constructed as part of the project:

– De Hoop Dam Gauging Weir

(Situated immediately downstream of the Spillway);

– Taung Gauging Weir

(Situated approximately 80 km downstream of the dam, near the influence with the OlifantsRiver); and

– De Hoop Upper Gauging Weir

(Situated approximately 30 km upstream of the dam).

DEVELOPMENT OF RCC AT DE HOOP DAM

Original RCC Mix: OPC 68

PFA 172

Total cementitious 240

53mm aggregate 316

38mm aggregate 505

19mm aggregate 631

sand 816

Additive (plasticizer)

Additive (retarder)

Water 120

W/C Ratio 0.52

DEVELOPMENT OF RCC AT DE HOOP DAM

Properties of the Original Mix:

• Low paste mix;

• Harsh mix;

• Difficult to apply and to achieve density;

• Segregation occured;

• Permeable mix; and

• Requires “Skin Concrete” or “Grout Enrichment”.

IV-RCC MIX DEVELOPMENT• International Expertise was utilized to

assist with Mix Development in order to stay in touch with International trends;

• IV-RCC (Immersion Vibrated Roller Compacted Concrete) was developed;

• IV-RCC is a high paste concrete mix;

• Eliminates the need for “Skin Concrete” as normally used in RCC dams;

• Placement in 300 mm thick layers;

• Recently altered methodology to placement in 400 mm layers and testing density by means of Strata Gauge;

• Development of IV-RCC is truly a ground breaking achievement.

RCC ACRONYMS

• Current known acronyms used in the International RCC industry:

– GERCC (Grout Enriched RCC)

– GEVRCC (Grout Enriched Vibrated RCC)

• New Acronym created at De Hoop Dam:

– IV-RCC (Immersion Vibrated RCC)

IV-RCC MIX DEVELOPMENT

Mix Description RCC (15/38) Original

RCC (15/38)Spillway

Conventional Concrete (15/38)

OPC 68 62 87

PFA 172 145 203

Total Cementitious 240 207 290

53mm Aggregate 316

38mm Aggregate 505 883 789

19mm Aggregate 631 483 511

Sand 816 877 821

Water 120 122 145

Additive (retarder) 2500cc

Additive (plastisizer) 2400cc

W/C ratio 0.52 0.59 0.50

Technical Design Information of the Mix:

RCC PLACEMENT IN PROGRESS

CONSTRUCTION PROGRESS• June 2007 Commencement of Construction

CONSTRUCTION PROGRESS• December 2007 First (1st) Stage River Diversion

CONSTRUCTION PROGRESS• June 2008 First (1st) Concrete Placed

CONSTRUCTION PROGRESS• August 2008 R555 Traffic Diverted and First (1st) RCC Placed

CONSTRUCTION PROGRESS• March 2009 First (1st) Outlet Pipes Installed

CONSTRUCTION PROGRESS• May 2009 International expertise utilized (F Ortega)

New IV-RCC Mix Development Commenced

CONSTRUCTION PROGRESS• January 2010 New RCC (IV-RCC) Placed in Spillway Section

RCC PLACEMENT RECORD ATTEMPT (NOVEMBER 2010)

• The Contractor attempted to break the South African record for RCC placement in a month;

• Previous record was 40 600 m3, placed at Wolwedans Dam;

• The Contractor was successful and a total of 103 000 m3 was placed in 21 Days;

4 November 2010

RCC PLACEMENT RECORD ATTEMPT (NOVEMBER 2010)

RCC PLACEMENT RECORD ATTEMPT (NOVEMBER 2010)

9 November 2010 (After 5 Days)

RCC PLACEMENT RECORD ATTEMPT (NOVEMBER 2010)

27 November 2010 (After 23 Days)

RCC PLACEMENT RECORD ATTEMPT

(NOVEMBER 2011)• A further attempt to break this record was conducted in November 2011

and the Contractor was successful in placing 131 000 m3 was placed in 28 Days;

OVERALL PROGRESS

• Overall Progress– 89% Complete (Measured against time);

• Commencement of Impoundment– Closure of Second (2nd ) Stage River

Diversion (Diversion Culvert) and diverting river flow towards Compensation Water Pipe until water level rise sufficiently for operation of the Outlet Works to commence;

– Impoundment is expected to commence towards October 2012;

• Estimated Completion– Overall Completion is expected towards

March 2013.

THANK YOU