Berg River Dam, situated in the mountains close to Franschhoek, Western Cape, South Africa is a 60m high Concrete Face Rock-Fill Dam (CFRF) with a 900m long crest length. During construction the river diversion works consisted of channels, a cofferdam and a training wall where the Main Contractor Berg River Joint Venture (BDJV) trained their personnel and honed their dam building skills.

Outlet works comprises of a dual wet and dry well with a multi-level intake tower that is 58m high and a 5,5m diameter concrete outlet conduit. The side channel spillway is 40m long and consists of a discharge chute, deflector bucket and plunge pool (maximum discharge capacity of 740 m³/s).

Dam capacity is 4 million m³ and a gross storage capacity of 130 million m³.

Berg River 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.
• Vibrating Wire Settlement Cells in the rock-fill for measuring settlement.
• Standpipe Piezometers for measuring water table.
• Vibrating Wire Transducer measuring seepage.
• Data Acquisition System CR800/1000 (Valve House).

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

• Settlement of the Embankment;
• Pore pressure within the Embankment and foundations;
• 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 (Foundation, Plinth and Conduit)

• Geokon Vibrating Wire Model 4500S

Joint Meter (Concrete face and plinth)

• Geokon Vibrating Wire Model 4400

Crack Meter (Plinth and starter slab)

• Geokon Vibrating Wire Model 4420

Strain Gages (Face and Conduit)

• Geokon Vibrating Wire Model 4210/4200/4202

Tilt Meter (Face)

• Geokon Vibrating Wire Model 6350

Pressure Cells (Conduit and Main Embankment)

• Geokon Vibrating Wire Model 4800

• Geokon Vibrating Wire "Fat Back" Pressure Cell Model 4810

Settlement Cells (Fill)

• Geokon Vibrating Wire Model 4650

Convergence Meters (Conduit)

• Geokon Model 1610 Tape Extensometer

Data Acquisition System CR10000 (Outlet House)

• Geokon Micro-1000 Data logger Model 8021

• Geokon Multiplexer (MUX) Model 8032

Designers: A.L. Melvill

Consulting Engineers: Berg River Consultants (BRC), a joint venture between Ninham Shand, Knight Piésold and Goba Moahloli Keeve Steyn

Contractors: Grinaker LTA, Wilson Bayly Holmes-Ovcon (WBHO), and Group 5 (BDJV)