Includes construction, repair or maintenance of all buildings, structures or equipment, and the installation of machinery.  No canal, sewer or cellar excavation or underground mining.

Code 4000 applies to employers engaged in digging sand, clay, gravel and shale.  In some cases, the clay is loaded onto small cars and hauled to manufacturing plants or shipped.  Sand and gravel involve digging or dredging operations.  Sand or gravel is excavated with hand shovels or with mechanical apparatus such as power shovels, drag lines, clam shell diggers or cranes or obtained from navigable or non-navigable waters by means of hydraulic dredges, clam shell dredges, etc.  Water is pumped into the soil to loosen the sand or gravel which is then pumped through pipes to hoppers.  The sand or gravel is conveyed from the bank, pit or dredge to hoppers by means of trucks, belt conveyers, narrow gauge railroads or pipelines.  At the hoppers, sand or gravel is washed to remove any foreign element, graded and sorted by means of revolving screens, stored in bins, hoppers or piles, or dumped or chuted to delivery conveyances.  Sand and gravel in its natural state usually requires only screening with the larger stones being rejected.  However, when the rejected material is run through a crusher and then rescreened, the crushing operation is incidental provided that the principal business of the employer is sand or gravel digging. 

This interpretation is intended to distinguish crushing operations by sand and gravel dealers from rock crushing operations that take place in connection with quarrying operations.  Also included under the scope of this classification is the preliminary stripping operations which consist of the clearing of brush (not trees), some pulling of stumps, removal of top soil or occasional blasting.  Note that this classification applies only when the excavation is performed to obtain sand or gravel for reprocessing (such as washing and screening) and used elsewhere other than at the point of deposit from dredging operations.