Admiral Combs Memorial Design Retreat - Summer 98

For 1998, the 18 students participating in the Admiral Combs Memorial Design Retreat will be working on a design project associated with Boston's Central Artery/Tunnel Project. Frederick R. Harris, Inc. in Boston is the host; with offices located right on Boston Harbor. Students will also be taken on tours of the construction sites.

The Boston Central Artery / Tunnel (CA/T) Project is intended to replace the current elevated I-93 with tunnel sections, and extend I-90 through South Boston to Logan International Airport via a new immersed steel tube tunnel (Ted Williams Tunnel). Planing for the project began in the early 1980's, and construction activity has peaked within the last two years. Completion is scheduled for 2004 with a construction value estimated to be more than $10 billion.

The area selected for the students is the interchange between I-90 (Massachusetts Turnpike) and I-93. This interchange is a key component of the project. A 27-acre site, it extends from Kneeland Street on the edge of Chinatown south to West Fourth Street. To the west is I-93, also known as the Southeast Expressway, which is being replaced, and to the east is the Fort Point Channel. Constraints on the site include South Station and attendant trackage. At peak construction, more than 350 train movements per day will cross the site on nine tracks.

The design of this urban interchange is expected to include concrete viaduct structures, cut-and-cover tunnels, bridges, immersed tube tunnels, tunneling under active railroad lines, depressed boat structures, and at-grade roadways that provide connections to the local street network. Several key design issues will be addressed by the students:

  • Geometry - They will develop a conceptual design of the overall layout including all major routes of travel, particularly the HOV lanes. This includes consideration of alignment, traffic, site/roadway, drainage/hydraulics, environmental, and utility issues.
  • Tunneling - They will conduct an alternatives analysis for the design of the interface between the cut-and-cover tunnels and the immersed tube tunnels. This includes consideration of structural, geotechnical, and environmental issues as well as fire, life and safety, and tunnel drainage.
  • Ramp Design - They will push toward final design of an HOV ramp that connects I-93 to I-90, including viaduct, at-grade, and tunnel sections.

Each team is to address critical areas of concern regarding environmental impacts, highway geometry and traffic analysis, traffic management, structural/geotechnical design, bridge design, major utilities design, and site drainage.

The retreat is an outstanding experience. It gives the students a chance to apply what they have learned to a real life situation. It also gives them an up-close-and-personal opportunity to see what civil engineering is all about. Students in the past have found it sharpens their skills and whets their appetite for learning more. For certain, that will happen this year also.