Sacramento sits at the confluence of the Sacramento and American Rivers, creating a shallow water table that rises during winter months. This underground water pressure pushes moisture through foundation slabs and basement walls in older commercial buildings, particularly those constructed before modern waterproofing standards were adopted in the 1980s. Office buildings in Downtown, Midtown, and Old Sacramento face elevated groundwater intrusion risk from November through April when regional rainfall peaks. The American River often reaches flood stage, raising subsurface water levels across the basin. This creates hydrostatic pressure against below-grade walls, forcing water through cold joints and utility penetrations. Commercial buildings with basement parking or ground-floor retail spaces face the highest exposure.