Work at the property had exposed the septic tank, leading to the woman falling through a small hole in the rusted metal top of the tank.
Firefighters found her with raw sewage inches from her face and needed to call reinforcements to rescue her.
A confined space rescue team arrived, equipped with air monitoring and ventilation equipment.
"It can be definitely a scary situation, especially sitting at the bottom of a septic tank and you don't know that anybody's coming to get you," Nick Wettlaufer, an engineer/paramedic, told KATU.
Firefighters lowered the handle of one of their tools, allowing the woman to grab hold and sit up enough that her rescuers were able to place a strap around her and hoist her up.
"Once we got her out, she was pretty weak so we just got her straight onto the cot and laid her down," said Anderson.
The woman, who didn't have any visible injuries, was taken to a nearby hospital due to concerns about the lack of oxygen in the tank and possible infection from the raw sewage.
Anderson told KATU that the woman did not want to be identified publicly.