Maintaining your septic system is important to keep it working properly over a long period of time. Good septic maintenance also protects our health and environment. Why is Maintenance Necessary? Septic systems need proper care and maintenance. We have all heard stories about septic systems that have worked well for many years without any maintenance or care. These are the exceptions to the norm. Eventually, the bacteria in the septic tank become unable to digest all of the solids in the tank. The scum and sludge layers begin to build up. This may cause the solids to block the sewer line from the house or pass out into the drainfield and clog the pipes. Clogged drainfields may result in surfacing sewage, offensive odors, plumbing backups, or contamination of surface or ground water. Repairs to a system can also be costly. It costs less to maintain a system than to replace it. Maintaining a Septic System The septic system must be inspected at least every three years for conventional gravity systems and annually for alternative systems, and pumped when necessary. To inspect the tank, uncover both the inlet and outlet access covers. Use a stick to measure the thickness of the scum and sludge layers. It is time to pump the tank if the sludge is more than 12 inches thick or within 8 inches of the baffle, or if the scum is more than 6 inches deep or within 3 inches of the bottom of the outlet. Inspect the inlet and outlet baffles and replace them if they are broken or missing. The baffles help keep the liquids from being stirred up. They also keep scum and sludge from leaving the tank and clogging the drain lines. If the septic system uses a pump, test the alarm and all controls and hose down the protective screen. The drainfield requires little maintenance. It should be checked from time to time to make sure there is no surfacing sewage. Vegetation should be kept to a minimum. Roof drains should be directed away from the drainfield. A thick growth of grass or spongy ground may indicate a potential failure. Don't drive over or park on the primary drainfield or the reserve drainfield. Drainfield Landscaping Carefully choosing the plants you have growing over your drainfield is an important part of taking care of your septic system. Avoid trees, shrubs, and water-loving plants with deep roots. These can clog or damage the pipes in your system. Grasses, mixed wildflowers, and ground covers with shallow roots are good alternatives. Department of Health Brochures:
Skamania County is updating its Critical Areas Ordinance.
Office Location:
Courthouse Annex
170 NW Vancouver Ave.
PO Box 1009 
Stevenson, WA 98648


Office Hours: Monday - Thursday 7:30am - 5:30pm Closed Fridays & Holidays

Phone Number: (509) 427-3900




UCD Handbook

Underwood Conservation District's Handbook

UCD News

2019 Annual Plant Sale

The Underwood Conservation District is accepting orders for low-cost tree seedlings and flowering shrubs through its annual native plant sale which runs thru February 28th. Visit or call (509)-493-1936 for more information.