Oaks Union Depot: Engineered Excellence for Urban Mixed-Use Housing

Project Overview

BKBM provided structural and civil engineering services for Oaks Union Depot, a 70-unit apartment complex in the heart of downtown St. Paul. The building incorporates two levels of parking and is designed for maximum efficiency and performance in a tight, high-density urban site directly adjacent to the city’s light rail line.

Project Highlights

  • Integrated Structural Design:
    • Three levels of post-tensioned concrete (below-grade parking, main floor, and podium slab) provide robust support for five stories of wood-framed apartments above.
    • Partial mezzanine level on the top floor adds flexibility, while its design offsets the upper most wood level inward to create attractive recessed balconies.
  • Tight Urban Construction Solutions:
    • Building footprint set within 1 foot of all four property lines, maximizing residential and amenity space.
    • Close proximity to the light-rail line and significant elevation change across the site created complex foundation and retaining wall challenges.
  • Innovative Foundations & Field Coordination:
    • Blindside waterproofing and a raker-and-waler system used for temporary soil retention on the north side.
    • Foundations were designed on battered piles to manage unbalanced soils; excavation revealed numerous existing piles requiring field modifications.
    • Over 90% of pile caps were adjusted on-site due to conflicts or pile misalignment, with BKBM delivering expedited redesigns—typically within 1–2 days of new survey results—to keep the project on schedule.

Engineering Solutions

BKBM’s proactive problem-solving and rapid field coordination minimized construction delays and provided cost-effective, robust foundation and superstructure systems. The team’s expertise with post-tensioned systems, urban site constraints, and real-time site adaptation ensured constructability and long-term performance.

Results & Impact

Oaks Union Depot offers efficient, modern living spaces and secure parking in a sought-after downtown location, with striking recessed balconies and resident-focused amenities. BKBM’s civil and structural engineering ensured the project overcame complex site and foundation challenges, achieving both design intent and project timelines for the client.