repairs or improvements . So what ’ s an alternative ? How about a walkable tunnel underneath the corridor to supply the steam , chilled water , compressed air , signal , and electric services so crucial for daily life on campus ?
The University ’ s East Campus Utility Improvements project involved the installation of this walkable utility tunnel – essentially a 10- by 12-foot-wide , 1,800-foot-long underground vault . To complete the project , the Wisconsin Department of Administration ’ s Division of State Facilities ( DSF ) worked with a design team of Affiliated Engineers Incorporated ( AEI ), Ayres Associates , Bloom Companies , and JJR .
Such a proposed tunnel was bound to conflict with existing underground utilities , which meant that storm sewer and water mains , sanitary sewers , and other civil utilities would need to be relocated . Ayres Associates provided these relocation services , as well as traffic / pedestrian control , survey , and construction services . The high-profile , large-scale project was completed in phases over five years .
A major challenge of the project was installing a portion of the tunnel underneath West Johnson Street and University Avenue – two busy roadways connecting the east and west sides of Madison . So vital are these arteries that the City of Madison stipulated that the roads could never be closed during construction . Any lane closures were largely restricted to off-peak hours .
To deal with these limitations , the design team came up with several options , including boring ( i . e ., going underneath the majority of utilities ) and using temporary bridges . A cost analysis revealed that the option of temporary bridges was the most cost-effective and offered the least surface disruption .
This approach involved constructing bridges to hold and maintain the existing street levels , allowing the tunnel to be constructed underneath the streets while traffic above could continue . Before the temporary bridges could be constructed , structures called H-piles were driven into the ground where the tunnel would be installed to support the bridge decking . A frame work was installed between the H-piles to keep soil from collapsing into the excavation . Over the course of numerous weekends , the existing surface on University Avenue and West Johnson Street was removed one lane at a time and then repaved with a bridge deck sitting on the H-piles .
The construction involved a true bridge deck design using reinforced bar – also known as rebar – and highearly-strength concrete so that traffic could be back on the surface by 7 a . m . each Monday . The bridge decks were used for two years while the tunnel was being constructed . When the tunnel was completed underneath these roadways , the bridge decks were removed and replaced with colored concrete .
But don ’ t forget all that “ spaghetti .” Fred Klingbeil ,
8│TRENDS