Design-Build Elevator Pit Remediation After Concealed Conditions
Location: Southeastern United States
Industry: Industrial Facilities
Service: Occupied Space & Facility Renovation
The Situation
An active industrial facility required design-build elevator pit remediation as part of a planned freight-elevator modernization. The existing pit floor and surrounding support conditions needed to be investigated, strengthened, and reconstructed before future hydraulic-system work could proceed.
JBrennon’s scope combined structural and geotechnical coordination with field demolition, concrete cutting, exploratory excavation, formwork, infill placement, confined-space controls, and procurement support for future elevator components. Because the work occurred within an existing building, access, lifting, lighting, fall protection, and work-area controls had to be incorporated into the construction approach.
The Challenge
Initial demolition was intended to expose the existing hydraulic jack head and prepare the pit for a defined structural modification. Once the floor was opened, however, the field team discovered a substantial subsurface void and concealed support conditions that were not represented in the available documentation.
Continued excavation also revealed oil-impacted material near the legacy hydraulic equipment and underlying bedrock. The original construction assumptions could no longer provide a reliable basis for the work.
JBrennon paused the affected activity, stabilized the work area, and coordinated the additional exploration, soils evaluation, structural analysis, and atmospheric monitoring needed to understand the conditions. The remediation design and means and methods were then revised around the actual pit geometry, existing cylinder, underlying rock, and surrounding structural elements.
A second field challenge emerged after the initial concrete placement. When the forms were removed, localized areas around the cylinder and perimeter had not filled completely. The geometry of the existing pit prevented the first concrete mixture from reaching every concealed space. Those remaining voids required another engineered placement using pumpable, high-strength grout.
How We Worked
JBrennon established the required confined-work-area controls, including lockout/tagout coordination, portable lighting, fall protection, atmospheric monitoring, and controlled access around the elevator pit and adjacent crawlspace.
Crews performed concrete cutting, coring, and exploratory demolition to establish the extent of the subsurface void. Field findings were incorporated into structural and geotechnical evaluations, which informed the revised pit-infill design and construction sequence.
Before concrete placement, crews constructed and braced forms around the elevator base and pit perimeter. Anchor holes were drilled to stabilize the formwork, and foam isolation material was installed around piers and the existing hydraulic cylinder to protect components from direct contact with the infill. Fill and observation openings were cored through the existing slab so placement could be monitored across the concealed space.
Approximately 23 cubic yards of concrete were pumped into the pit void during the primary placement. Crews monitored multiple fill and weep openings to confirm the movement of concrete beneath the existing slab. The exposed surface was finished, and concrete break testing was used to verify that the placement had reached the required strength before the forms were removed.
Form removal exposed localized areas where concrete had not completely reached the perimeter and cylinder interface. JBrennon documented the remaining conditions, reconstructed the necessary forms, and prepared the affected areas for a supplemental placement.
High-strength, pumpable grout was then installed to fill the remaining concealed spaces. The grout placement was monitored from the surrounding accessible areas until field observations indicated that the remaining voids were filled. After strength testing, the forms were removed and minor accessible conditions were completed through dry-packing and localized patching.
JBrennon also coordinated procurement planning for future hydraulic-jack, liner, buffer, channel, and hydraulic-fluid components associated with the broader elevator modernization. Those components are not represented as installed under this case study.
The Outcome
JBrennon delivered a completed engineered pit-remediation system based on actual subsurface and structural conditions rather than the assumptions available before demolition. The finished work filled the concealed void, reconstructed the pit support area, addressed localized gaps through high-strength grout placement, and established a stable foundation for future freight-elevator modernization.
Subsurface void and concealed structural conditions identified during demolition
Structural and geotechnical investigations incorporated into a revised design-build solution
Confined-space, fall-protection, lockout/tagout, and atmospheric-monitoring controls maintained
Existing hydraulic cylinder protected during infill operations
Formwork anchored and braced around the pit and elevator base
Approximately 23 cubic yards of concrete placed in the primary pit infill
Fill and observation openings used to monitor concrete distribution
Localized remaining voids filled with pumpable high-strength grout
Concrete and grout strength verified before form removal
Pit surfaces dry-packed, patched, cleaned, and prepared for future elevator work