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We recently completed a unique and challenging project for a new client. The project required dismantling a 55’ diameter x 36’ height (600,000 gallon) steel tank. That part of the project is very familiar to us, as we maintain a steady diet of dismantling tanks of all sizes, materials and purposes.
This tank, however, was part of a sewerage treatment plant and had been used to collect “grit and screenings”. Rather than having been routinely cleaned, the grit & screenings had collected in the tank to the point where they became an inaccessible solid mass which was 16 feet deep in the tank.
After consultation with the tank manufacturer and doing our own structural engineering survey by Tom Berenz on our staff, it was decided that we would surgically remove the roof and top 16’ of the tank shell to make the grit and screenings accessible for removal.
We selected our Volvo 700 High Reach Excavator as the ideal machine for this job because of the reach available (95 feet) and capacity for a shear to cut and dismantle the top half of the tank and an interchangeable rotating basket grapple, which we felt could efficiently remove the accumulated grit solids which were supposed to be coffee ground consistency and to remove and load the material to waiting trucks.
We adapted our grapple with steel plate to make a clam bucket. Our fabrication/welder, Bob Hughes, did a fabulous job of rolling, fitting and welding plate to make the new “clam bucket” look like it just came off the showroom floor!
To the surprise of all involved, the solid “coffee ground” material was actually a soupy, sludgy mess that had far too much moisture content for handling and removal, trucking and disposal parameters at an ultimate disposal facility. To say that the material was stinky is a vast understatement.
Working with our client, we used a combination of creating sumps for dewatering by pumps and installation of fifty tons of perlite, an inorganic absorbent material for solidification, and lime for odor control to bind up the grit to make it able to be loaded, transported and disposed at the out of state landfill. We took the additional step of providing and installing truck liners for each load to further contain any liquids.
Initially we had installed a gravel work pad adjacent to the tank to allow our operator, Kevin Grant, a better angle and visibility. Kevin’s 700 is also equipped with cameras that let him view the grit removal and not hit or damage the remaining tank wall containment during the removal process. As we got to the tank bottom, we placed a skid steer loader into the tank to collect all remaining grit and “clean the corners” of the tank. Shawn Clouten was instrumental in support of lining and loading each truck and then had the unenviable task of running the skid steer inside the tank for the final clean up.
The remainder of the tank was dismantled for scrap. We replaced the clamshell/grapple with the shear once again to complete the final tank demolition and scrap processing. Final site clean-up and removal of the gravel work platforms completed our task of site restoration.
Greg Geyer was the project manager, overseeing all activity and tracking all transportation and disposal activities. Sean Rae, our operations manager, made sure that the entire team had every piece of equipment, tool or supply in anticipation of every need to allow the project to proceed safely and efficiently.
Great job by the whole team!
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