This building was recently completed in uptown Charlotte. We were not the base building plumbing contractor but we currently have a few interior office up fit projects within.
Before construction began the NC Department of Environmental Quality’s soil tested the site. The results led the NCDEQ to require this building be built with a designed sub slab depressurization system to keep the contaminated soil toxins from permeating into the interior of the building.
This is what the base building plumbing contractor initially installed, which may have been what was drawn, I don’t know.
After the buildings final inspections, NCDEQ tested the sub slab’s negative pressure and it was unsatisfactory to mitigate the toxic vapors as required.
So, the new current contractor in charge of up fitting the building for the owners was now also used to upgrade the sub slab depressurization system. They contracted us and I was told to add a second motor of the same and use the second stack that was already in place.
(I do not know the details of why two stacks were initially installed with only one motor)
This is what I came up with. I’m not impressed with the outcome, but it was done.
After this the NCDEQ tested the negative pressure again and it was STILL unsatisfactory.
So, it was decided to have us install a much, much bigger motor. This time the contractor asked for me by name to install the new motor because it had to be done quick. The depressurization system is not supposed to ever be taken off line so absolute minimal time for assembly was required.
Flattered and obliged to be named I arrived and was I was told to build a heavy duty stand that would hold a very heavy motor. I had to quickly engineer a stand with only a spec sheet in hand depicting a generic version of what was needed because the motor hadn’t arrived on site yet.
So, I went to Ensco and bought unistrut, nuts, spring nuts, washers, square washers, 1/2” rod & 1/2” wedge anchors. At Ferguson I bought the 2” no hub cast, fittings & heavy duty no hub bands.
The motor soon arrived on site and WOOF!
This is what I came up with.
My helper left me half way through to go to a different companies job interview while I was sweating bullets building this thing I only imagined up two hours ago with neck breathers reminding me to hurry up, NCDEQ is coming. The electrician was in the same boat as me and was pulling a new circuit with a disconnect.
Man, when we got finished and turned that thing on and it pulled gravel from under the slab, the motor ground up the gravel and shot little pieces of rock up and out the 80’ tall discharge pipe. It rained pebbles and ground water down on all of us and we all cheered for it was clearly working well!
NCDEQ came and took their negative pressure sample and they were finally satisfied! As was everyone else