Tunnel Rehabilitation

Rehabilitation

Primary Guidance Assume only nighttime tunnel closure windows will be available to complete the proposed work. Coordinate with appropriate tunnel operations staff.

Discussion General The following MDOT TBUs own and maintain transportation tunnels: Maryland Transportation Authority (MDTA) Fort McHenry Tunnel (FMT) – Interstate 95 under the Patapsco River Baltimore Harbor Tunnel (BHT) – Interstate 895 under the Patapsco River Maryland Transit Administration (MTA) Baltimore Metro – Baltimore Metro Subway under Baltimore City Fort McHenry and Baltimore Harbor Tunnels Rehabilitation project designs must be closely coordinated with the appropriate tunnel operations staff. In almost all cases, shutting down a tunnel bore for an extended period is not possible due to the resulting severe traffic impacts from the reduced traffic capacity. Operations staff for both tunnels develop and maintain weekly nighttime closure schedules for the tunnel bores. BHT: weekly nighttime closures Monday through Thursday only, from 9:00 pm to 4:30 am FMT: southbound closures 7:00 pm to 4:30 am; northbound closures 8:00 pm to 4:30 am. Routine maintenance work is scheduled to coincide with nighttime closure schedules and needs to be accounted for during project design. While closure schedules and maintenance operations are subject to change, they must be used as a basis for developing how proposed rehabilitation work can be performed and sequenced. Baltimore Metro Subway Tunnel Rehabilitation project design must be closely coordinated with Metro Operations. Any work inside the tunnel tubes is considered “fouling” the track and typically requires track outage to perform the work. The typical available track outage hour is from 1:00 am to 3:30 am weekdays and 1:00 am to 4:30 am weekends. When longer shutdowns are necessary, bus bridges should be provided. The design should consider: Scheduling the work that can be completed in the track outage hour or can be stabilized for the train service to resume until the next track outage hour. The storage area and transporting path for the materials and equipment. The distance between the access point and the work zone. Work inside the underground stations, vent shafts, cross passages, emergency stairs that does not foul the track may not be subject to the track outage restriction. Peak-hour work restrictions, however, will apply to the work in the public area. If access to these ancillary areas requires passing through the tunnel tubes, the track outage restriction will still generally apply. Single Tracking Operations or Service Shutdowns Single tracking operations or service shutdowns may be available to provide longer track outage hour, but is subject to MTA’s approval. Single tracking operations: Provide a longer track outage hour in one tunnel tube without shutting down the Metro service. Typically, creative single tracking operations during the off-peak hour will result in minimum service impacts while providing long enough track outage to perform the work. For this reason, it is the preferred option. Service shutdowns: If service shutdowns are necessary, first considerations should be to weekends or other periods during low ridership. A feasibility study for construction sequencing, operations impact, service impact, and budget impact should be performed when a service shutdown is proposed. Additional operational cost such as a bus bridge, transit ambassadors, additional field supervision, service schedule change, and revenue loss should all be considered as part of the project budget impact. An hour-to-hour construction activity schedule (including the testing and certification activities) should be developed to estimate the required shutdown time.