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Most of the external concrete walls have been poured for the southern unit of the new Oxidation Ditches and backfilling around the tanks has begun.
Since installation of the stone columns in the Oxidation Ditch and Secondary Clarifiers was completed, the installation work was moved to the new Dissolved Air Floatation Thickeners (DAFT) and Tertiary Clarifier areas.
Work was projected to be completed on these final stone columns mid-September, but the construction sub-contractor, Hayward Baker, was able to finish early just at the end of August. Hayward Baker is currently disassembling their equipment and continuing their demobilization. A total of 1600 stone columns were installed to a maximum depth of 50 feet. These structures will help stabilize the tanks and other equipment constructed above them during a seismic event and prevent excess settling due to liquefaction. As work continues on the Oxidation Ditches, work starts up on the new Secondary Clarifiers including installation of temporary sheet piles to allow for excavation required to install the Return Activated Sludge (RAS) pump structures.
These RAS pumps will move the micro-organisms through the treatment process so they can help remove the pollution from the water. On the other side of the plant site from the Ox Ditches and Secondaries, underground pipes have been installed with associated valve structures to convey the liquid biosolids from the storage lagoons to the drying bed.
Excess water is removed from the biosolids and the remaining solid material is co-composted with green waste to create a beneficial soil amendment product used by commercial landscapers.
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