Given: finely perforated pipes are driven vertically into the ground around the perimeter of an area to be excavated. These pipes are connected to one or more above-ground pumps. In order to lower the water table. This de-watering system is:

Given: finely perforated pipes are driven vertically into the ground around the perimeter of an area to be excavated. These pipes are connected to one or more above-ground pumps. In order to lower the water table. This de-watering system is: