A South Florida Solution to a Central Florida Problem - A 44 Feet Deep Bottom Seal Excavation-Video

Video Transcription

Video Summary

Keller engineers presented a deep-excavation solution for Tampa’s DL Tippin Water Treatment Facility. The High Service Pump Station required a 44-foot excavation—about 35 feet below groundwater—in loose sands beside the Hillsborough River, with karstic limestone and a nearby operating 5-million-gallon tank. Groundwater control by dewatering was impractical, so the team installed a deep soil-mix bottom seal, tied down with piles, and reinforced soil-mix perimeter walls. Anchors and internal bracing provided lateral support. Jet grouting underpinned the tank and treated areas obstructed by utilities; monitoring and inspections helped protect the tank. Three-dimensional modeling helped route anchors around existing structures and pipes. Karst voids caused grout losses during anchor installation; grout socks reduced anchor redrilling by roughly half, though they did not eliminate the issue. The bottom seal was 8–11 feet thick, and its weight was included in reducing uplift demand on the anchors. The presenters emphasized careful quality control, utility coordination, and site-specific construction sequencing.

Keywords

deep excavation

soil-mix bottom seal

groundwater control

jet grouting

karst limestone

anchored retaining walls