Complex sentence: After the exhumation, work continued in the trenches over the following week, before the site was covered with soil to protect it from damage and re-surfaced to restore the car park and the playground to their former condition.
Split into simpler sentences: After the exhumation, further work was done in the trenches during the next week, before the site was covered again with soil to protect it from damage. It was re-surfaced to restore the car park and the playground to their former condition.