We are implementing several things in a project to comply with this prerrequisite, regarding the cleaning of the vehicle's tires leaving the site we are washing them and then the vehicles go on a bed of rock before they leave the site. However some dirt is still stick to the tires leaving the streets a little bit dirty. We have some workers wipping the dirt but still there are traces of it on the road.

How "clean" does the street need to be in order to comply with this part of the plan?