Challenge

Clay County Utility Authority (CCUA) obtained Ground Penetrating Radar and found that an 18 inch deep by 20 to 30 foot anomaly had formed at the North side of the tank. Ramos Engineering & Associates (RE&A) was retained by the contractor, TB Landmark, to craft a plan to stabilize the settling clarifier tank due to high variability in the densities of the existing subsurface soils. Three separate stabilization techniques would need to be sequentially performed.

Solution

CCUA contracted with TB Landmark to oversee the tank stabilization. RE&A was retained by TB Landmark to craft a stabilization plan for clarifier tank #2. Three different repair techniques were recommended by RE&A to stabilize the tank and remediate the karst and loose soil conditions. Helical piers and both low mobility grout and polyurethane grout were recommended to stabilize the tank. LRE Foundation Repair (LRE) installed 3.5” diameter helical piers around the perimeter of the tank on 6 foot centers. Per OSHA guidelines, the pier installation required dewatering and trench boxes for bracket installation due to the foundation being 10 feet below ground surface. High pressure low mobility grout was installed to densify the deep karst conditions below the tank. Pressure grouting was performed from 75 feet and terminated at 22 feet below ground surface at 4 foot lifts. To stabilize the soils above this elevation polyurethane grout was performed at 17 feet below ground surface. The project was successfully completed withoutinterrupting operationsof clarifier tank #2.

Project Summary

Contractor: TD Landmark

Foundation Contractor: LRE Foundation Repair

Specialty Engineer: Ramos Engineering & Associates Inc.

Repair Process:  28 - 3.5” Helical Piers with 10” - 12” -14” Helix Configuration 57 points using 400 CY of high pressure grout 57 points using 3,500 lbs. of Polyurethane Grout.

Tank in Need of Repair

Helical Pier Lead Section

Helical Pier Installation

Polyurethane Injection Pipes