Far below the hustle and bustle of game day sits one of Wrigley Field's most unsung heroes, more than 200 of the city's strongest micropiles. One of the efforts most critical to The 1060 Project was to strengthen the foundations to accommodate the planned additions and expansions to the superstructure.
Like most of Chicago, Wrigley Field is built on a sandy lake bed that was raised with repeated infilling. Bedrock begins almost 75 feet below the surface, making soil stabilization of utmost importance.
Decades of wear and tear had left many of the columns supporting the ballpark in need of restoration.
The columns were restored, increasing the ballpark's foundational load capacity. Along with geotechnical experts Hayward Baker and engineering firms Thornton Tomasetti and GEI, the team installed four 500 kip capacity micropiles 100 feet under each column before welding on a new zero-tolerance column base.
213 micropiles have been installed throughout the ballpark. An additional 24 columns were lifted, structurally reinforced, and foundations replaced.
Construction continued alongside a detailed sequence of shoring the structure, removing walls, and restoring the columns and deep foundations at strategic intervals.
A kip is a unit of force. It equals 1000 pounds-force, used primarily to measure engineering loads Each micropile installed at Wrigley Field can withstand 500,000 pounds of force or 500 kips. In context, that's enough to support the weight of the Statue of Liberty.
Listen to Pepper Senior Project Manager Andy Johnson explain the process using a 3D printed model.
The clubhouse is located outside the ballpark, under the plaza building. Utilizing this subterranean approach provides a more controlled, secure environment which increases security for players and allows the Cubs to utilize more space inside the ballpark for enhanced fan amenities. The underground location and distance to the field required an innovative solution to get the players from the clubhouse to the field. The Cubs carefully constructed an underground tunnel, which called for a meticulously-devised excavation and construction process that provided the Cubs a way to expand their venue while preserving the integrity of historic Wrigley Field.
A major component of The 1060 Project was providing the players with the best-in-class facilities needed to train, rehabilitate injuries and prepare for games. Since assuming control of the franchise, the Ricketts family has made it a clear priority to renovate or rebuild all of the team's facilities to the big leagues' modern standards and beyond. To provide the team with the best clubhouse in the game, more than 30,000 square feet of space was dedicated to new player facilities. Completed by Opening Night 2016, the new clubhouse area includes a locker room for players and coaches, a strength and conditioning center, training and hydrotherapy areas, a media center, offices and a player lounge. Batting tunnels also have been added so hitters can warm-up against live pitching before, during and after games. The visitor's clubhouse will be expanded and improved in a future phase of the 1060 Project.
The restoration brings back several historic touches to the façade including the original natural terra cotta roofing, ornamental grillwork and sunburst screens amidst the ballpark's steel frame.
The iconic art deco marquee was completely restored and reinstalled in time to welcome fans to Opening Day 2016.
Like the ballpark, soil stabilization played a key role in the clubhouse and plaza building. Sheet pile was driven 36 feet down into the silty clay where it meets the hardpan to separate the excavated area from the ballpark. (2703198.jpg if an image is helpful) Then the team used a process called top-down construction to stabilize the sandy soil and expedite the schedule.
Hear Pepper Project Executive Brian Peter discuss how top-down construction helped create the plaza and clubhouse.
We're installing the last micropile this year. Sign up to follow progress on this and other updates at Wrigley Field.
Location: Chicago, Illinois
Owner: Chicago Cubs Baseball Club, LLC
Owner's Rep: ICON Venue Group
Architect: Stantec Architecture
Photography: Steve Green, Bob Elmore and Pepper Construction