North Metro Treatment Plant Slurry Wall

Project Location: Denver, Colorado

Project Description:

This was a negotiated/limited project with only qualified bidders who proposed to own it. This project was unique because the purpose of the soil-bentonite cutoff walls (slurry walls) was not for the typical water storage use but instead it was to protect underground structures and equipment from groundwater. We completed this project as a subcontractor.  Hall-Irwin had to overcome three main challenges. The first challenge on this project was working around multiple contractors on a very active project site.  Hall-Irwin was hired to line two cells in two separate phases of work.  The second challenge was working next to a deep large sewer pipe that had to be installed prior to the cutoff wall.  The cutoff wall also had to be constructed underneath this pipe in order to create a sealed cell.  Plus, it was absolutely essential that the cells were constructed such that once the site was dewatered, the mass structures that were underground would no longer be exposed to groundwater.  The third major challenge was working around other utilities as well as tying into a clay plug, constructed by others on the site, to achieve the complete cut off of ground water.  Both of these cells had a minimum of a 5 FT key; the north cell was 2,893 LF with average depth of 25 FT while the south cell was 5,850 LF with an average depth of 38 FT.