At a parking structure in Burlingame, California, the shotcrete structure and mat slab were exhibiting signs of unwanted ingress from the water table outside of the building.

While evidence of cracking was not necessarily present, efflorescence on the interior surface of the walls told the tale that the migration of unwanted groundwater was presenting a problem.

The structure is referred to as an Automated Parking Structure where building tenants can retrieve their automobiles by entering a code at the entry point to the structure and have their vehicles essentially “delivered” to them once the internal workings of the structure retrieve the vehicle. It becomes obvious from this description of the project that water has no place in the intricate electronic systems that comprise this facility but more so on or near the vehicles that live in this structure. Something needed to be done and a certified specialized contractor was called in to get the water mitigation handled.

The construction of the concrete is something to note, particularly with respect to the steel in place at a double mat (2 layers within the walls) of #9 and #11 bars at a spacing of 24” on center each way. This reinforcing steel is a sturdy configuration –and a lot of steel — all of which is susceptible to corrosion if water is present after the shotcrete’s cure out.

That amount of steel, if subject to corrosion, could, over time lead to spalling and eventually an overall degradation of the structure if left unaddressed.