There are ways to cut through most scrambling, but they are very technically involved, and as I believe that the "Government" has longitudinal wave data transmission available to them, it would not surprise me if they merely staged an emp event to blow all the transmitters. Your best bet for com is still courier, unless you can figure out how to build a handheld longitudinal wave tranciever. I haven't. Btw, it would take an astronomical amount of power to jam everything in the lower 48 at once.
I certainly wouldn't get a building permit, or you've defeated much of the purpose of having such a hideaway. If prisoners can tunnel out of prison under the watchful eyes of their guards, you ought to be able to expedite this project without alerting the civil authorities.
Otherwise, as people have pointed out, there are different ways to build an underground or earth-bermed shelter, based upon location, materials, climate, and what's needed. However, here are several important related issues that will not change much from person to person.
WATER: can you install a well? Do you have access to a local spring? Otherwise, collected runoff from the regular house roof would be helpful. See online for free instruction.
FOOD: Store sprouting seed, do-it-yourself-packed in nitrogen to prevent weevils. You can find instructions for the nitrogen set up online, using sealed food-grade plastic buckets and a pressurized cylinder. Grains and beans. The latter can also be planted, as can radish and other seeds. Lacto-fermented vegetables, in large quantity, are a good way to go; you can make them well in advance and cycle them through your normal food consumption. Shelf life at ground temp. is at least one year (my experience). In Rumania, farmers allegedly fill a 50 gal. food-grade barrel with whatever is in season. There's much free instruction online!
WASTE DISPOSAL: Human feces plays a major problem in sanitation. Unless you are situated over an old mine-shaft, the HUMANURE system is hands down the best way to go. Especially if you must remain sheltered for some time. With a few venting adjustments for the bunker situation this would be the way to go to eliminate germs, mess and smell. There's no room here to explain it, but there's much free instruction onine. And it's basically free, so you can use the money saved for other things. Google "Humanure" for full details. Urine elimination is easily handled if you're situated on any kind of slope, via underground 4" pipe.
TOXINS: Something else to consider: Petro chemicals, including kerosene and paraffin give off poison that won't be healthy in confined situations. You might want to use vegetable oil lamps, with proper ventilation. The oil can also be consumed if you don't need it and you should store gallons of Olive Oil anyhow, in glass jugs. MiddleEastern stores usually have these at decent prices ($20 gal±). The heat emitted will help heat your bunker. Proper venting is necessary where ever fuels are burned for heat and light.
MEDICINE: Potent healing tinctures may be made at very low prices per gallon, using 100 proof vodka and locally or easily obtainable herbs Include at least Echinacea (angustifolia), Poke (Phytolacca americana), and Cayenne (use Habanero for max. benefit). Hawthorn would be a good bet if someone has heart issues. Shelf life if sealed in glass (wax over the caps) and kept cool and dark is many years. Garlic tincture should also be on your list and LOTS of fresh garlic, which you can cycle into your normal food consumption during the year. Did you know that in WWI the Brits used mashed raw garlic paste on moss dressings to treat severe wounds and prevent infection? Fresh garlic is one of the most potent antibiotics on earth, but it loses much of its potency when dried or de-skinned, so tincturing at least a gallon will be a 'must.' Info available online, free.
ENTERTAINMENT: Frivolous as it may sound, entertainment and recreation are necessary, especially when you are under STRESS. If you've always wanted to play a musical instrument, why not assure that it will be available in your bunker, where you may have plenty of time on your hands? Jig saw puzzles, cards, and a few good board games should be high on your list of "necessities!"
All of the above may also be applied to non-bunker survival situations.
I have hands-on experience with everything except the nitrogen packing of sprouting seed, which is pretty simple, as are the other processes. I hope this helps!