Valley National Bank, in the heart of downtown Tampa, planned a major building expansion. The design called for a new elevator shaft, a structural element connecting multiple floors and relied upon daily by employees and clients.

Before construction could move forward, it was essential to confirm the foundation soil beneath the shaft could handle the load and vibration over the long term. In Tampa Bay's urban and coastal zones, unpredictable sandy soils pose serious risks for structures without proper stabilization. Valley National Bank turned to Helicon, Florida's trusted name in foundation repair, soil stabilization, and polyurethane grouting.

Initial Assessment

Helicon's site evaluation identified two hurdles.

Tight access. The shaft sat inside an existing, older building downtown. Narrow entryways, low overhead clearance, and the confined urban setting meant traditional foundation repair equipment would not fit. Helicon's polyurethane injection equipment is engineered for low-footprint, tight-access work where heavy machinery is not an option.

Sandy, unstable soils. The subsurface was primarily loose, granular sand, prone to shifting under heavy loads. Left unaddressed, it could cause uneven settling of the shaft, leading to operational problems and possible structural damage. The solution had to strengthen the sand without adding excessive weight, distribute load uniformly beneath the shaft footprint, and install without major disruption.

Proposed Solution 

Helicon selected AP Soil 600, a one-part, low-viscosity polyurethane permeation grout engineered for sandy soil stabilization. Low viscosity allows deep penetration into loose soils. The material is light relative to its strength, binds soil particles to reduce settlement risk, and resists water infiltration in Florida's wet climate. AP Soil 600 is widely used where high load-bearing capacity is required, including elevator shafts, bridge abutments, and commercial foundations.

Procedures

1. Evaluated the site to confirm subsurface conditions beneath the planned shaft footprint
2. Designed a grid of 14 injection points beneath the footprint
3. Drilled each point to 5 to 6 feet, targeting the soil layers most at risk of movement
4. Injected AP Soil 600 through the grid, ensuring coverage without gaps
5. Permeated the sand, locking it into a dense, load-bearing mass
6. Confirmed uniform support across the foundation before vertical construction began

Results 

• Delivered a stable base for both the static weight of the shaft and the dynamic forces of daily elevator operation
• Eliminated voids and weak points, increasing soil density and shear strength
• Installed quickly and cleanly with minimal disruption
• Kept construction on schedule
• Treated the soil before vertical construction, heading off future settlement and repairs

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