Unless instructed otherwise the Contractor shall use any topsoil stockpiled as part of the site clearance works. Should there be a shortage of stockpiled topsoil then the Contractor shall obtain the approval of the Engineer for the importation of topsoil from sources external to the Site.
For the placement of topsoil the Contractor shall use "low-ground-pressure" equipment such as tracked vehicles rather than wheeled vehicles. Before spreading topsoil the Contractor shall disc-cultivate the prepared subgrade to a minimum depth of 100mm which shall then be harrowed and/or screeded to form surfaces to line and level. These surfaces shall be left in a loose condition until ready to accept the respread topsoil.
All topsoil shall be spread to a uniform layer thickness, as shown on the approved drawings or as instructed by the Engineer, over all exposed earthworks surfaces to be grassed. The topsoil shall be clean friable soil, free from excessive amounts of gravel, have less than 20% sand and have no other debris or fragments which, in the opinion of the Engineer, could affect later plant growth or maintenance. The topsoil shall not be spread when the ground or the topsoil is excessively wet or plastic or otherwise in a condition detrimental to successful construction of the work. If the Engineer approves placement of the topsoil when it is wet or plastic then it shall be loosely spread and traffic kept off and the topsoil allowed to dry before being worked. The topsoil shall be smoothed with a chain-harrow or similar towed by a light tractor to produce a smooth, evenly graded, open textured surface, free draining and which will not pond water. All minor depressions, wheel marks and other irregularities shall be eliminated.
The requirements of CS-23.2 Topsoil Spreading/Respreading shall also apply.
Definitions in this section