- O'Hare 90-inch Water Transmission Main Relocation
Burns & McDonnell provided engineering services for the relocation of a 90-inch water transmission main for the City of Chicago. The existing 90-inch water transmission main runs directly beneath Runway 18L/36R of O'Hare International Airport and conflicts with proposed airport improvements. The relocation of the 90-inch water main avoids new north Runway 9L/27R being constructed as part of a multi-billion-dollar expansion of O'Hare International Airport.
The existing 90-inch water main, serving seven communities with a population of 315,000 people, must be kept in service for the duration of the project. Use of Stopple technology allows the 90-inch water main to be relocated without interruption of customer service. Conceptual design of the project by others included the construction of approximately 11,000 linear feet of 90-inch water main. Burns & McDonnell's detailed review of the conceptual design identified several major challenges including insufficient space to construct a portion of the 90-inch water main along Higgins Road; construction of a portion of the 90-inch line along a stream bed; and future mass grading leaving portions of the new 90-inch water main with up to 25 feet of cover, making access for maintenance extremely difficult.
Burns & McDonnell overcame the challenges by designing 48-inch temporary bypass lines 3,500 feet and 1,600 feet in length to reduce the amount of new 90-inch water main installation by approximately 50 percent, and initiating revisions to the master schedule for airport expansion. Burns & McDonnell's preconstruction management activities reduced the construction cost of the 90-inch water main relocation project from $29.2 million to $16.3 million for a savings of $12.9 million.
In recognition of the technical challenges and extremely tight design schedule, Burns & McDonnell staff completed more than two dozen technical design memorandums in parallel covering all aspect of the project to establish design criteria and outline specifications on an expedited basis. Pipe material evaluation included the potential use of prestressed concrete cylinder pipe, steel pipe and ductile iron pipe. Detailed specifications for all three materials were prepared for use on the project.
- Routing study
- Value engineering
- Risk analysis
- Pipe material evaluation
- Fast-track scheduling
- Stopple technology