Given more time to actually look at the picture, I would def. say this would be the work of a species in the family Agelenidae (Funnel-Web Spiders) or Family Lycosidae with the genus being Sosippus (Funnel Web Wolf Spiders).. especially with the fact that your father claimed more webbing was present the previous visit!
-There are 10 species of Funnel Web Wolfiies, 6 species can be found in North America north of Mexico. These species include; californicus, floridanus, janus, mimus, placidus, and texanus.
-The most characteristic sign of a Funnel-web's burrow is the irregular 'silk trip-lines' that radiate out from the burrow entrance of most species; (FYI, these 'trip-lines' alert the spider to possible prey, mates or danger).
Here are some examples of some Funnel Web Wolf Spider burrow along with other information and pictures;
I hope that information will help in some way or another, LOL! If nothing else, gently stick a long piece of grass in the burrow and see what pops out! Good Luck and please, let us know if you need any other info! :]
Thanks for the info! I probably won't be able to visit the site. It's near a water tower and cell phone tower and not for public access. I could tag along with my father perhaps, but I'm not sure it's worth the trip considering that the temperatures are starting to get lower here in the Northeast.
I'm gonna send him those funnel wolf burrow pictures and ask him how they compare to the previous visit.