What's a failure? Island County Code defines a failure as "a condition of an onsite sewage system or component that threatens the public health by inadequately treating sewage or creating a potential for direct or indirect contact between sewage and the public".
This can include sewage backing up into a home, usually at the lowest point of entrance such as a basement shower or toilet. If sewage is ponding on your drain field or is surfacing - your system is failing. There may be some quick and cheap ways to remedy the problem - the sooner you act the better. You may be able to save a lot time, money and effort by addressing issues quickly. The longer a system is in a failure state the more it could cost.
If you have a failing system, contact a licensed maintenance service provider or Island County Public Health for troubleshooting support.
Washington State Department of Health - Signs of Septic System Failure