Three days before Thanksgiving, the Coral Springs Improvement District (CSID, with whom we have a continuing design-build services contract) informed us they had experienced a structural problem with their Plant D Package Plant. Within a hour, Globaltech had an investigative team at the plant site. It appeared that water from the plant’s outer aeration ring had rushed into the inner clarifier section in a rapid, uncontrolled fashion, lifting up the clarifier section.
Globaltech returned the next day, after all water had been pumped from the plant, to continue investigating. We noted damage to the clarifier floor and mechanism arms, displacement of the WAS pipe, and separation of the axial wall in the aeration section from the interior and exterior walls. Eager to learn why this happened, CSID issued a Work Authorization to have Globaltech develop a summary report on the probable cause of damage, with recommendations for corrective action.
Globaltech subcontracted with a structural engineering firm to assist in evaluating the cause of the failure and developing a remedy. Our investigation included collecting corings, with compressive tests, of the sloped clarifier floor in several locations.
The evaluation concluded that the high-water level in the aeration ring, in relation to an empty clarifier, caused the entire clarifier section to float due to hydrostatic forces. This led to damage of the clarifier mechanism, cracking of the clarifier floor, slight displacement of the clarifier wall, damage to aeration piping/diffusers, damage to the divider wall in the aeration basin and minor damage to piping and electrical.
Project Achievements / Benefits
Based on the damage, Package Plant D could not be used until the repairs were made. The recommended repairs, which Globaltech was hired to execute, include:
- Replacing some mechanism components, including the drive
- Replacing the clarifier floor slab with a new fully-reinforced floor slab, to be structurally tied into the flat base slab
- Installing additional, larger clarifier wall anchors.
- Replacing the aeration basin baffle wall
- Repairing aeration diffusers and piping
- Minor repairs to water piping, electrical components, and coatings
- Modifications to the walkway to provide better access to the man-lift safety hoist