The excavation plan for a foundation requires a level bottom with a tolerance of ±50 mm over a 10-metre length. Which grading technique is best suited to achieve this precision with an excavator?

Question: The excavation plan for a foundation requires a level bottom with a tolerance of ±50 mm over a 10-metre length. Which grading technique is best suited to achieve this precision with an excavator?

Answer options:

• Freehand digging with visual estimation from the cab.
• Using a graded spoil pile beside the trench as a visual reference. ✅ Employing a laser receiver mounted on the stick for continuous grade checking.
• Setting a batter board at one end and digging to that depth across the entire length.

Correct answer: Employing a laser receiver mounted on the stick for continuous grade checking.

Explanation: Achieving a precision grade of ±50 mm over a significant length typically requires more than visual estimation or a simple batter board. A laser receiver mounted on the stick provides continuous, real-time grade checking, allowing the operator to maintain the required depth with high accuracy. Batter boards are useful but less precise over long distances without constant checking.