Willows, red osier dogwood and elderberry do well in the wet areas around here. Not sure how they would like the hardpan however.

Nothing beats Cottonwood - Populus Fremontii is your native variety - for sucking up water. This doesn't work during winter when the plant doesn't have leaves, but it will work great the rest of the year. Other choices include willows, or really any shrub for a riparian (water influenced) area. Cottonwoods grow really fast, so you'll have large trees in a few years.