Irrigation Water Canal Connects Ancient Spanish Cities
Trimble 3D guidance system guides construction

Catalonia, Spain is rich in history. Residents living between two of its provinces, Lerida (founded 6th century BC) and Tarragona (founded 5th century BC), are witnesses to the construction of a history-making irrigation water canal.

The 200 km canal is being constructed by EPSA International, Algete. Spain. The massive project began October 2008 and is expected to be completed by September 2010. EPSA International must adhere to the region’s strict construction requirements.

The 20m-wide canal will be dug to a depth of 7m. The earthen canal will be lined with concrete. It features a trapezoidal shape with side slopes of 1 to 1.5 and the bottom bed-width being 4 meters.

EPSA International employs a Liebherr R984-C Litronic crawler excavator for its principal rough earthmoving work. The 118,600 – 125,000 kg machine has a seven-meter shovel capacity. Additionally, two smaller-size Liebherr R934-C Litronic crawler excavators are being used to complete the finishing work on the bottom and shape the clay banks of the canal, using cleaning buckets with hydraulic tilt function. The two smaller crawler excavators are 31,100 - 35,900 kg machines with backhoe bucket capacity of 0.95 - 1.95 cubic meters.

Traditionally, the finishing work of shaping the sides and canal bottom were completed by in-the-trench human assistance. Workers, using visual signs to the machine operator would indicate how much cutting and filling is required.

EPSA faced two major challenges that had them look for an alternative to the traditional helper-in-the-trench approach:

• The job specifications called for higher accuracy.
• A tight deadline called for faster production.

Higher material costs require that the layer of concrete applied in the canal must be as accurate as possible. If the concrete is too thick, there would be an unnecessary increase in cost, while if it is too thin, the quality of the completed work could be compromised.

With the ambitious completion date, EPSA knew its level of productivity would have to increase. The increased rate of production meant the contractor would need to be shaping the banks faster than the trucks could pour concrete. Any delays in pouring could result in wasted loads of concrete and hold-ups in work, with the additional costs that this implies.

EPSA International understood that it needed help. The company turned to SITECH Iberia, Madrid, the Trimble distributor serving Spain and Portugal, for a solution. SITECH Iberia reviewed the project needs with EPSA, and recommended equipping one of the Liebherr R934-C Litronic crawler excavators with the Trimble GCS900 Grade Control System for Excavators to perform the finish excavating.

The Trimble GCS900 Grade Control System, with dual GPS receivers and solid-state Trimble AS300 Angle Sensors, is designed to measure the precise 3D position of the tip of the excavator bucket. This system’s two GNSS [Global Navigation Satellite Systems] antennas are mounted behind the operator cabin on athe excavator’s counterweight. The receivers capture signals from GPS and Glonass satellites. A Trimble SPS851 base station sends reference coordinate to the machine. The on-board Trimble CB430 computer de