Rain on Mesh - pooling around structures

Hoping that someone might be able to chime in on this. I have a rain on mesh model with pipe networks. Terrain modifications were made for the building footprints and refinement regions added with the footprints too. The model runs and seems to make sense as to what I'd expect, however there is pretty consistent pooling next to the buildings with excessive depths that don't make sense. The depths tend to produce mounding of water (in some cases in excess of 3 feet where they should otherwise drain out). Does this indicate that my mesh is too large and I should refine it in these areas? It's a large study area with +400k cells so I'm a little hesitant to drop cell resolution from the 20' it's at to something half that wherein my run time will be pushing 24 hours. Thanks for any advice/input!