Went by today and the field is actually different than the turf at Russo Park. Helmut can explain the differences much better than me but here goes.
For baseball, loads of underground drainage pipes with rock were installed below the field surface before the final top coat and turf were installed.
From what I could see the softball field going down is more like an indoor arena except with some drainage component. The outfield areas outside the standard dirt/clay infield was dug down, leveled, and a concrete covering was installed over the field except right along the outfield wall where a "french" drain system will be installed. On top of the concrete it appears they will install some type of padding/foam type underlayment that water can permeate and allow the water to run off to the drains. On top of that surface they will have the rubber pellets typical of turf fields and then the turf. I'm hoping that Helmut has some familiarity with this process to correct any guesswork I've done. After leaving I was sorry I didn't take any photos.