Bedford Dam, situated on the mountains above Ladysmith, Kwa-Zulu Natal, South Africa is a 49m high Concrete Face Rock-Fill Dam (CFRD) with an 810m crest length. This dam structure forms the upper reservoir of the Ingula Pumped Storage Scheme. During construction the river diversion works consisted of channels, a cofferdam and a training wall where the Main Contractor Bedford/Bramhoek Dams Joint Venture (BDJV) trained their personnel and honed their dam building skills.

The Main Embankment (480m) has a 170m Long clay core extension and 42m dry well single-level intake tower.

The Dam capacity is 22.4 million m³ with an active water storage volume of 19.2-million m³.

Bedford Dam Instrumentation consists of the following:

• Convergence points in the Outlet-Tunnel measuring expansion/contraction.
• Vibrating Wire Strain Gauges in and around the Outlet-Tunnel, measuring concrete and re-enforcing strain.
• Vibrating Wire Load Cells and Vibrating Wire Pressure cells around and on top of the Outlet-Tunnel, measuring total load and pressure.
• Vibrating Wire Piezometers in the Clay Core of the coffer wall/embankment, measuring pore pressure.
• Five sets of Vibrating Wire Perimetric Joint Meters are installed on crucial structural points on the plinth and the concrete face slab, measuring three-dimensional movement between the plinth and the starter slab.
• Eighteen Vibrating Wire Embedment Jointmeters are installed in the top parts of the various vertical joints of the concrete face slab measuring movement between the joints.
• Two Horizontal Inclinometer casings on the face slab measuring deflection of the face slab as such.
• Vibrating Wire Settlement Cells in the rock-fill for measuring settlement.
• Standpipe Piezometers for measuring water table.
• Vibrating Wire Transducer measuring seepage.

Instruments installed in and around the Dam Embankment are intended to monitor:

• Settlement of the Embankment;
• Opening of the concrete face slab joints;
• Stresses and deflection in the face slab concrete;
• Stresses, strains and convergence of the Conduit;
• Pore pressure build-up around the Conduit and Main Embankment.

Installed Instruments Specification:

Seepage (Dam, Conduit and Spillway)

• Geokon Vibrating Wire Transducers Vented Model 4580

Piezometers (Clay Core against Retaining Wall)

• Geokon Vibrating Wire Model 4500S

Joint Meter (Concrete face and plinth)

• Geokon Vibrating Wire Model 4400

Strain Gages (Face and Conduit)

• Geokon Vibrating Wire Model 4210/4200/4202

Pressure Cells (Conduit and Main Embankment)

• Geokon Vibrating Wire Model 4800

Settlement Cells (Fill)

• Geokon Vibrating Wire Model 4650

Convergence Meters (Conduit)

• Geokon Model 1610 Tape Extensometer

Data Acquisition System CR800/1000 (Valve House)

• Geokon Micro-1000 Data logger Model 8021

• Geokon Multiplexer (MUX) Model 8032

Designers: Steward Scott Incorporated (SSI), Arcus Gibb and Knight Piésold

Consulting Engineers: Braamhoek Consultants Joint Venture (BCJV) comprises three of the country's mayor consulting firms namely Steward Scott Incorporated (SSI), Arcus Gibb and Knight Piésold

Contractors: Concor Roads & Earthworks, Wilson Bayly Holmes-Ovcon (WBHO), Edwin Construction and Silver Rock (BDJV)