So Monday started off with us continuing the backfilling operations behind the retaining walls. On Tuesday, the concrete sub and I laid out the mechanical trenches so that his crew could start the excavation for the HVAC ducts. Because everything is going underground, precision is critical. Once the ducts are cemented into the trenches they cannot be moved, so we are checking and re-checking to make sure it all works. We've also had to re-design the footing to allow for three 16" ducts to pass through it without compromising the integrity of the wall. This is the part of the project we've all been nervously joking about (I keep making references to needing another rolaids or valium). The slab layout is the most difficult phase for us because there are structural, electrical, plumbing, and mechanical lines running through the trenches underneath the slab. On top of all that goes the radiant floor, so nothing can be amiss.