Depending on the type of septic system that you have there are different requirements. The first item below is a full length guide to filling out the forms and performing the inspection. The other documents are various forms. You will need to fill out at least the first form and, depending on system type, perhaps one of the others as well.
Sand Filter Add this form if the septic system includes a sand filter
Sand Media Add this form if the septic system involves sand media (e.g. Sand Mounds, Sand Lined Trenches, etc.) NOTE: Do not use this form for sand filters
Aerobic Treatment Unit (ATU) Add this form if the septic system involves an Aerobic Treatment Unit NOTE: ATUs are considered proprietary, as defined in WAC 246-272A-0010, and must be inspected by a Cowlitz County licensed O&M professional specifically approved for that product by the manufacturer