Use a steel rake to crush and break up large chunks of clay. Start at one end of where the sewer line trench was dug and work your way to the end. The goal is to crush the clay into the smallest bits possible with your rake.
Open a bag of top soil and walk along the path next to the sewer line where the dug up dirt is piled up next to the trench. As you walk pour the contents of the top soil over the piled up clay. Once the first bag is empty open another bag and continue. Do not completely cover the clay with soil but pour enough for it to mix thoroughly with the clay. Four to five 20-lb. bags of soil should be more than adequate.
Use the steel rake to mix the clay and soil thoroughly.
Shovel the clay and soil mixture carefully back into your trench. Use the rake or a hoe to pull lingering dirt and clay off your grass and into the trench. Smooth the mix on top of the trench with a rake.
Place 4 cups of spreadable fertilizer into your spreader. Walk up and down the length of the trench a couple times, or until you have emptied out all the fertilizer.
Water the affected area for around 45 minutes daily for a week or until you see grass begin to sprout.