The primary purpose of this Design-Build project is to decommission four existing 1960’s era substations and update the existing electrical distribution in strategic, needed areas within Building 810 at the Denver Federal Center. Major pre-construction aspects of the project include pre-design metering of existing loads as well as existing supply capacity, survey of existing panelboards for replacement with modern equipment, engineering and design of construction documents. Preparatory work prior to decommissioning the four substations included conduit installation, wire pulling, testing and termination in order to supply power to existing 480V branch distribution loads, rerouting power from the obsolete substations to nearby modern substations. Once the power feed from new substations is in place, coordinated power shutdowns allow the decommissioning of each substations medium voltage feeders, load break switches, oil-filled transformers and 480V switchgear. In addition, 25 existing obsolete panelboards and one 30KVA oil filled transformer are removed and replaced with modern equivalents.