Excavation along the west lot line--adjacent to the American Surety Building--required blasting through bedrock. Three of the laborers hold rock drills. The heavy steel mat at the lower left was used to cover the area being blasted to prevent debris from being shot throughout the site. Splices to the timber post at the left shows how the temporary timber frames are extended as the excavation continues downward. Sheeting in the background appears to have been undermined.