Containment of 25% Caustic Tank at Congleton Waste Water Treatment Plant
Congleton wastewater treatment plant approached our tank partners United Rentals for a replacement bulk tank for an old ISO tank held on site. The old tank was held in a bund that was formed from PVC liner and scaffolding to secondary contain the tank. The unit had been in place for some years and the bund had clear signs of weathering.
The tank held a 25% caustic solution required for dosing in the treatment plant, understandably this operation could not be interrupted, and we were required to coordinate the work with a pump contractor who came into setup temporary dosing via IBC’s, in this time the clock was ticking to get the bunding setup because the IBC’s would soon run dry. Initially, United Utilities had specified an area where the bund could sit however upon inspection for installation we found this area to have kerbs that would interfere with how the bund would sit. Rather than move things operationally we came away from site and the ground was promptly levelled out with hardcore, this gave us a perfect base to work on.
The previous tank was decommissioned, and the temporary dosing was hooked up without a hitch, we went to site the following day alongside United Rentals to install the bunding system.
Firstly, a protective geotextile liner was put in place across the hardcore base, this protects the bund from any sharp stones that could potentially puncture the liner. To hold this down in place the walls were then assembled around the perimeter, leaving one end open to drive the new tank into the bund.
Once assembled by slotting these together the liner was then unfolded from the pallet and pulled into place, it was important to ensure there were no internal stresses within the liner, so this has to be performed carefully to ensure the liner is flat in the bund, this is why we always oversize our liner panels to ensure tears don’t occur. Once the liner sits flat into the base of the bund, the capping clips are positioned atop the bund and hammered firmly into place to secure the liners position.
The liner was then cut on one end so the liner sat flat on the entrance to the bund, this was performed carefully to ensure no liner required to go inside the bund itself was cut which could prevent the bund sealing correctly. Once flat the tank was reversed into the bund and placed on mats to spread the load as an extra protective measure.
Once positioned correctly the bund was then closed on the final wall, the remaining wall was capped off using the clips. Once this was complete the liner was cut to fit around the edges of the wall, the corners were folded into place neatly and the bund was complete.