You need to cut a trench all the way around the perimeter of the basement, to the depth of the foundation footings. Do not carve the earth below the bottom surface of the footings, although if you dig the trench 12 inches in from the footing side (probably 16 inches in from the foundation wall) then you can dig four inches further down which may assist in sloping the perforated drain pipes better.
(One morning on WRKO Radio) The tub's not clean! Let's remodel the bathroom.
(One afternoon on WRKO Radio) It's time for an oil change. I'm going to trade in the car for next year's model.