The sight of some 5.5 million tons of rubble left behind at construction sites in Greece each year could become a thing of the past in 10 years as a new law will be passed this fall to encourage the recycling of materials, government sources said yesterday. Under the new legislation, constructors will have to recycle at least 50 percent of the building materials that remain after they have completed their projects. The law will force builders to use materials, such as bricks and steel girders, that meet certain specifications which allow them to be reused. Before beginning construction, they will also have to submit a plan to town-planning offices to show how they will ensure that the material is recycled. Sources said that the legislation will allow the formation of companies whose business it will be to recycle rubble. These firms will also have to submit paperwork to town-planning offices so staff can check whether the amount of building waste recycled corresponds with the figure given by the construction company.