Mothballs are benzene based- a carcinogen. However- they do work. Never use them where a child or pet can get them or near a garden, food or water. Maybe use the flakes instead so they will evaporate more than soak into the soil. A loud radio on a wireless remote helps. You can set it off at varied times. See if you can find a hunting store with coyote or bobcat oil scent. It Really stinks so use it sparingly- maybe put it on a rag tied to a rope. Push it under the porch a bit Very slowly with a pole. Leave it for a few days after the last time you notice the skunks. Then put a drop or two along the entrance to keep them away til you can pull out the rag and close the hole. Hot pepper flakes will get into their eyes and mouths causing them as much distress as it causes us. However- they may spray. Good Luck!