20 DAYS TO EXCAVATE. ' . The excavation will, take about 20 days, it is said. The ditch is to be about 15 feet deep. The steam shovel will have to be abandoned as the ' ditch gets deeper, because it cannot be operated in such small space. As soon as the excavation is finished the walls will be constructed " with concrete. After that, carpenters will begin to board up the extra space and this will be filled In with concrete. Then work on the roof will commence. This consists of three separate Jobs, and because of the j . great weight of traffic must be done with the utmost care. Supports will j be constructed and then the excavation will be closed up, the dirt that is now being hauled away will be placed back and the asphalt company will reconstruct the street.