Final soil preparation, decompaction and fine grading After having set the drainage system in place, the final preparation stage is set in motion. Wheel marks and other surface imperfections are erased using different accessories. Great care must be taken when finishing the slit drained surface so that the drainage slits are not contaminated. All the drainage lines are checked and any problems are corrected at this stage. Surface sanding and final leveling Once all corrections to the slit drainage system have been completed and the surface is perfect, a fine layer of coarse sand is laid over the entire surface. This will isolate the slit drains from any contaminants and allow better access for the water having permeated the grass surface. This protective layer also protects the drainage system during sod roll delivery and installation. This sand layer can also serve as a seed bed when seeding is preferred over sodding.