The department said in a Facebook post that the woman, in her 40s, had dropped her phone into the toilet and fell in while trying to retrieve it. She found she was unable to get out on her own and called 911 after locating her phone.
The firefighters were able to pass the woman pieces of wood to build a platform to stand on, allowing the rescuers to reach her and pull her to safety.
The woman was "washed down" at the scene and given replacement clothes. Firefighters said she was not injured but they recommended she seek medical attention due to coming into contact with human waste.
The woman "only wanted to leave" and, after thanking firefighters, continued on her journey to California, the department said.