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2015 Chicago Chapter Award of Excellence: 10 & 120 South Riverside Plaza

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Project Details

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10 & 120 South Riverside Plaza are twin, 22-story office buildings constructed in 1965 along the west bank of the Chicago River and over the north terminal of Chicago's Union Station. They are situated between two major commuter rail stations and also serve as a pedestrian right-of-way easement through the property. 

Each plaza is surrounded by public sidewalks and streets on three sides, the Chicago River on the East side and an active Metra and Amtrak train terminal below. Previously renovated in 1985, the 30-year old plaza pavers were buckling and coming loose. Widespread leaking through the plaza was also creating a nuisance for rail passengers and deteriorating the structure and plenum below the plaza. 

A great deal of coordination, communication and cooperation between the design team, contractors, owners, Amtrak and governing agencies was required to successfully complete the project.

Unique challenges included:
  • Extremely limited space for staging the work
  • Site access limitations both above and below the plaza
  • Limited and conflicting permissible hours of operation restricted by Amtrak, the Chicago Department of Transportation, tenant operations and City noise ordinances.
To further complicate matters, ownership of the property changed during construction.

Careful sequencing and phasing of the work was critical for maintaining access to the building and first floor retail tenants. Temporary dining decks were built over the top of two planters that were to be substantially salvaged so that outdoor seating for the restaurants could be maintained during construction. 

Extreme care during demolition was necessary to prevent punching through the plaza and dumping debris on trains and commuters. Fortunately, full-depth repairs were limited in size and number and were very carefully executed.

Conventional Cast-In-Place concrete was used for most of the repairs, but fast-curing proprietary bag mixes and polymer-modified ready-mix concrete were used in limited areas where waterproofing needed to follow rather quickly.

Access to the railroad right-of-way below the plazas was limited to between the hours of 10PM-5AM, and only when Amtrak would allow it. With required daily safety training, mobilization and demobilization, the contractor was lucky to get 4 or 5 hours of work accomplished in each shift. 

Sections of deteriorated precast plenum floor planks were replaced with cast-in-place concrete poured in formwork hung from the plaza structure so as not to interfere with train operations after the end of the night's shift. Shotcrete was primarily used to repair the plaza slab structure. The only shoring allowed was ta tower used to temporarily support a 52-inch deep steel girder; the web had buckled from corrosion causing the area of plaza above it to drop three inches.

A hot-applied waterproofing membrane was applied to the structural deck. Due to some areas of sloping deck, multiple sequencing, phasing, and schedule requirements, flood testing was abandoned for EFVM testing at 100% of the waterproofing system. 

The plaza was finished with a pedestal pavement system, casti-in-place concrete planter walls and seating, custom designed built-in wood benches, stainless steel railings, lighting and landscaping, which transformed the riverfront plaza into an oasis in the midst of the city.

2015 Award of Merit: Wheaton Center Rehabilitation

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2015 Award of Merit: St. Charles Air Line Bridge

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Project Notes:

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Tower 2 Exterior Rehabilitation
  • 91 Balconies Replaced
  • Sawtooth Wall Forms
  • One Season Delivery
  • 9,500 Anodes Installed
  • 5,800 sf Slab Repair
  • 9,500 sf Wall Repair
  • Door Replacements
  • Membrane / Paints / Coatings
Garages & Recreational Deck
  • 96,500 sf Footprint
  • 2 Levels, 1 Below Grade
  • 550 Parking Stalls
  • 2,050 sf Topside Repairs
  • 23,500 sf Underside Repairs
  • 700 sf Full Depth Repairs
  • 7,000 Anodes Installed
  • 195,000 sf Waterproofing
Building 6 Lifting and Reinforcement
  • 3-Story Wood Framed Building
  • 1-Story Reinforced Concrete Podium
  • Shoring Towers with 600 kip Total Cap.
  • 3 Hydraulic Jacks per Tower
  • Unified Jacking System
  • Permanent Steel Framing
  • Shotcrete Repairs

Project Notes:

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Counterweight Details: 
  • Height: 56'6" H X 10-40' W X 6' D
  • Surface Area: 9,000 sf
  • Weight: 1,770 Tons
Square Apertures / Through Pockets:
  • Used for Weight Adjustments
  • Max. Blocks: 414
  • 3 Blocks per Pocket
Project Scope:
  • Surface Repairs: 9,000 sf.
  • Repair Depth: 10-12 in.
  • Install Galv. Welded-Wire Fabric
  • Wet Mix Shotcrete: 5,000 PSI
  • 6,000 cubic feet Shotcrete
  • Surface Applied FRP/Acrylic Top Coat
Unique Challenges: 
  • Bridge Operational 
  • Short Notice for Train Passage
  • Counterweights Balanced
  • Active Tracks & Roadway
  • Repair Heights up to 100 ft.
  • Max. Concrete Removal: 3 yd3 
  • 10 Hr. Window:Train Traffic
  • Liq.Damages: $1,000/15 min.