Aerial view of CNC Foundations' job site in the Delmar Loop, showing active aggregate pier installation across a large urban lot. The CNC drill rig, multiple pieces of construction equipment, and surrounding city buildings are visible on a clear day.
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Close-up of a CNC Foundations drill rig on tracked treads alongside a CAT 908M wheel loader at the Delmar Loop site. The equipment is positioned on cleared soil with mid-rise buildings in the background and a deep blue sky overhead.
Two CNC Foundations team members reviewing plans on site in front of a casino building. Both are wearing CNC-branded safety vests and white hard hats, with the team member in the foreground displaying a vest commemorating CNC’s 35th year in business.

AGGREGATE PIER INSTALLATION FOR MULTIFAMILY DEVELOPMENT ON THE HISTORIC DELMAR LOOP

  • DELMAR LOOP, ST. LOUIS, MISSOURI

CNC Foundations (CNC) delivered a ground improvement solution for Local U-City, a 414,000 SF multifamily development located in the heart of St. Louis’s historic Delmar Loop. To support the new construction, CNC implemented aggregate piers (VSCs), selected to improve challenging soil conditions and ensure long-term structural performance.

Situated in a dense, culturally rich urban corridor, the project demanded a fast approach that minimized disruption to the surrounding area. CNC’s engineered solution enhanced bearing capacity, controlled settlement, and helped keep the project on schedule—supporting both the stability of the structure and the revitalization of one of St. Louis’s most iconic neighborhoods.

  • Owner: SUBTEXT, LLC
  • General Contractor: Brinkmann Constructors
  • Structural Engineer: Pierce Engineers
  • Project Timeline: 20 Production Days
  • Project Size: 414,000 sq ft
  • Design Bearing Capacity: 3,000 psf
  • Service: Vibratory Stone Columns – Aggregate Piers
  • Install Numbers: 532 piers at 7,887 linear feet
  • Market Sector: Multifamily Development

The developer needed a foundation solution capable of supporting a large-scale residential structure on a site with undocumented fill and expansive clay soils. These variable conditions, compounded by potential groundwater intrusion, posed risks for differential settlement and schedule delays.

Deep foundations were not economically viable. The project required a fast, ground improvement system that could deliver reliable performance across a wide footprint. CNC Foundations also had to coordinate installation within a busy urban corridor, minimizing disruption to nearby businesses and infrastructure.

Subsurface investigation revealed:

  • Undocumented existing fill ranging from 1 to 11.5 feet
  • Expansive fat clay encountered at varying depths within both the fill and native soils
  • Groundwater anticipated within the lower-level excavation and encountered during installation

These conditions required a solution that could improve bearing capacity and mitigate settlement risks without extensive excavation or costly deep foundation alternatives.

CNC Foundations installed over 500 vibratory stone columns totaling over 7,500 linear feet across the site. Using a vibratory flot, stone was compacted in vertical lifts from design depth to surface, forming dense aggregate piers that:

  • Increased allowable bearing capacity
  • Controlled settlement within design tolerances
  • Enabled rapid installation with minimal site disruption
  • Eliminated the need for deep foundations or over-excavation

The project was delivered on schedule, with post-installation testing confirming design compliance and validating the performance of the ground improvement system.