Complex sentence: Embankments on the Widnes side were constructed from decontaminated material excavated along the route from historical industrial brownfield sites: treating and reusing the material meant that it did not need to be removed from the construction zone.
Split into simpler sentences: Embankments on the Widnes side were constructed from decontaminated material excavated along the route from historical industrial brownfield sites. By treating and reusing the material, it did not have to be removed from the construction zone.