Like a torch through the generations, Daniel Burnham's vision for Chicago helped guide the $162 million reconstruction of South Lake Shore Drive.

The thoroughfare and adjacent parks were part of architect Burnham's Chicago Plan of 1909, which sought to preserve the approximately 25 mi. of shoreline along Lake Michigan in a pristine state and also access for Chicagoans for generations to come.

Several initiatives were implemented during the current project to ensure the impact on motorists and pedestrians was minimized during the reconstruction of the 6-mi.-long segment between 22nd and 67th streets, said Chris Wuellner, project manager for the Chicago Department of Transportation, the project's implementing agency.

Keeping Traffic Moving

Traffic flow was maintained during the height of construction. Approximately 24,000 vehicles a day go through the road segment's southern reach, and the number increases to more than 110,000 vehicles on the segment's north end.

A moveable barrier - sometimes referred to as a zipper wall - that simultaneously closes a lane in one direction while it opens a lane in the other was used between the Stevenson Expressway and 47th Street to create a temporary reversible lane. Because only five lanes of traffic on the mostly eight-lane segment were open for use at any time, the system allowed three lanes of traffic in the direction of rush hour.

In the morning, when traffic headed downtown is heavy, three northbound lanes were open, said J.R. Kibbon, assistant project manager for Chicago-based Walsh Construction Co., a joint-venture member of the Walsh/II in One/Riteway general-contracting team. In the evening, when traffic away from the Loop is strong, three southbound lanes were available.

The zipper wall, which took five days to link together with pins, is 3 mi. in length. To move the wall, a machine picks up the precast segments on one side, and they emerge from the other side. The changeover takes approximately an hour.

"It's one unit, almost like a big Slinky," Kibbon added.

Construction in a Park

The parkland and park users were kept in mind.

The project right-of-way extended only between the drive's curbs, and the land outside the curb was Chicago Park District property. Fencing was put up to establish the demarcation contractors were not supposed to cross.

Fencing was also put around trees at their drip lines to ensure their safety.

"If equipment was stored under the drip line of a tree or if materials were stored around a tree trunk, we could assess monetary deductions against the contractors as part of the enforcement measure," Wuellner said.

The bike path was maintained so pedestrians could continue to use it. Signs and flaggers warned residents of activity ahead. Detours routed park users around obstructions if a path was closed for an extended period. Lighting was installed.

In some cases, bicycle paths were reconstructed or repaved.

"We sort of kept three balls in the air," Wuellner said. "One was the need to maintain vehicular traffic, another was to maintain the lakefront bike traffic and the other was the need to get construction done.

Often, each was competing with the other two."

Restoring Famed Drive

The segment was crumbling due to heavy traffic from everyday use, recreation and tourism. Though the segment was resurfaced in 1999, portions of the underlying roadway date to the original construction between 1910 and 1931, Wuellner said.

The project started in June 2002 and was substantially completed in June. Full completion is expected Aug. 30.

A number of additional project goals were identified during the planning, and the make-no-little-plans approach to the project resulted in eight contracts, Kibbon said. Enhancements were made to the drive's engineering, pedestrian access and overall appearance.

"The challenge was made by the mayor to do it right, to look at all the other issues associated with South Lake Shore Drive and to address as many of these as possible through the project," Wuellner added.

The Roads Ahead

No new lanes were added, but the drive is expected to handle increased traffic due to improved roadway geometry once the project is complete.

An exit lane, for example, was built at northbound 47th Street to improve traffic flow.

A new lane was also created to improve traffic safety between the inbound lane from the Stevenson Expressway and 31st Street, the only stretch that allows trucks. Previously, traffic on the stretch, much of it headed to the McCormick Place Convention Center, merged into mainline traffic.

"The horizontal and vertical alignments at some locations were substandard, and they had to bring those up to current standards," Wuellner said.

Roadway composition varies by location.

The road between 22nd and 57th streets has been removed and replaced with 9 in. of concrete. Portions were originally overlaid with asphalt, a material that was deemed unnecessary for the reconstructed mainline.

About 4,000 cu. yds. of concrete was poured every day, and the material was brought in trucks, Kibbon said. Space for a batch plant was not available adjacent to the project.

South of 57th Street, where Jackson Park starts, the roadway composition changes. The 9-in.-thick concrete base is topped with a 1.5-in.-thick binder and 1.5-in.-thick asphalt surface.

Noise from traffic on the asphalt surface will be less in the park where solitude is valued, Wuellner said. The dark surface will also be less jarring than concrete's bright surface.

"That was felt to be important in Jackson Park because of the historic nature of the site," he added.

Pedestrian Enhancements

Improvements to traffic flow pertain to pedestrians, too.

Five underpasses were built and an existing tunnel at 55th Street was reconstructed to improve access to the park.

Sheet piles with a waterproofed membrane were driven around the sites to prevent water infiltration, and excavating equipment was used to dig the holes, said Bob Hildebranski, vice president for Plainfield, Ill.-based Harbour Engineers, a project engineer.

About 2,000 to 3,000 cu. yds. of sand was removed for each hole, and the backfill was used for embankments along the drive.

"We call it onsite gold for the most part because we haven't had to wrestle with clay, silts or rough groundwater conditions," Hildebranski added. Reinforced concrete was laid for the underpass foundations, and either precast concrete or steel forms the walls. Improvements appear above ground, too. The 31st Street bridge received the largest amount of work, including two foundations - caissons for the abutments and steel H-piles for the wing walls - structural steel and decks.

Rain, Rain Go Away

Plans called for improved drainage of stormwater and water management.

"Prior to the project, most of Lake Shore Drive drained directly into the lake," Wuellner said. "Everything that washed off the pavement during a rainstorm got flushed into the lake."

About 10 mi. of pipe, a great deal of it 8- to10-in. in diameter, were put down in the median parallel to the roadway, and perpendicular crossings direct the water to a catch basin connected to a main, Kibbon said. Night was selected for crossings to minimize impact on traffic because only one lane was open in each direction.

A system of orifices and weirs ensures that the first flush - the dirtiest - is diverted to a treatment plant. Initial low flows pass through small-diameter orifices, and as the volume increases, flows spill over a weir to be diverted into the lake.

Design studies estimate that about 85 to 95 percent of pollutants will be captured, Wuellner said.

Another unique component, backflow preventers, makes certain sewage doesn't end up in the lake if the city's sewer system backs up.

Beautifying the Drive

Several enhancements will ensure an improved appearance.

Architectural precast and pilasters, for example, were added to the 31st Street bridge, the frequent gateway to McCormick Place.

A cast-in-place concrete structure dubbed Chicago Wall will be in the median as a barrier for safety. The design is suggestive of the Prairie Style of architecture.

"Its design was developed specifically for Lake Shore Drive, and it was first used for North Lake Shore Drive 10 years ago," Wuellner said.

A version of the wall will also be used in Jackson Park. Pedestrian concourses in the park will be landscaped with trees, shrubs, ornamental grass and perennials.

Along the roadway, about 14 acres of green space were returned to the park. An existing shoulder was removed north of 47th Street and replaced with periodic pull-out bays, and lanes were narrowed to 11 ft. wide.