I. Temporary Holding Tank: Provide a temporary holding tank placed on the existing pavement to receive water from the existing Fort McHenry Tunnel Low Point Pumping Stations (LPPS). Excavate near the existing holding tank to expose the LPPS force mains and extend the force mains to the temporary tank. The temporary tank will drain by gravity to existing sewer manhole EXMHS4. II. Rehabilitate Existing Holding Tank: Demolish all existing equipment and pumps. Remove existing holding tank structure above existing grade. Install temporary bracing to support existing tank walls. Demolish existing steel wall stiffeners and floor stiffeners. Install new holding tank concrete walls and top slab with required access hatches and pipe connections. Install control panel, float controls, and guide rails for duplex submersible pumps. III. Roof Drain and Floor Drain Piping Separation: The existing West Ventilation Building roof drains piping system and floor drain piping system combine to discharge to the storm drain system. The intent is to separate the two systems so that the roof drains discharge to the storm drain and the floor drains discharge to the existing sewer system. a. Roof Drain Piping: Cut and remove portions of interior vertical roof drains at various locations. Install new roof drain piping to exit the building. Install new below grade roof drain piping and manholes to connect to the existing storm drain system. b. North Side Floor Drain Piping: Install new below grade drain piping and manholes to connect the existing floor drains to the existing sewer system. New floor drain system includes the installation of a below grade oil/water separator. Abandon in place existing drain piping between new floor drain manholes and new roof drain manholes. c. South Side Floor Drain Piping: Install new below grade drain piping and manholes to connect the existing drains to the holding tank. Abandon existing drain piping between new floor drain manholes and new roof drain manholes.
