Landscaping with an on-site sewage system
Landscaping when you have an on-site sewage system (OSS) requires special care. Since your yard is where wastewater is treated, a landscape design should not interfere with the natural functioning of your OSS. A balanced combination of oxygen and organisms will maintain healthy soils necessary for your system.
3 easy steps to develop a landscape design:
An as-built is a drawing of your septic system in relation to your house and property boundaries. Your septic system designer completes the as-built after the septic system is installed. Public Health keeps as-built drawings on file as public information. You can request Public Health to search their records for your septic system. NOTE: Not all records are complete and older septic systems may not have as-builts.
Avoid landscaping on or near the septic tank. Consider installing "risers" or septic tank lids to make septic tank pumping and monitoring visits easier and less time-consuming.
The septic tank, drainfield and reserve area should be clear of:
- underground sprinkler lines
- decks, patios, sports courts, or utility storage sheds
- sand boxes
- paved or dirt driveways
- parked vehicles
After locating the septic tank, drainfield and reserve area, you may now begin the design phase. Keep the tips in Step 2 in mind.
Do's and Don'ts when preparing your garden:
- Don't plant a vegetable garden on or near the drainfield or reserve area
- Plants over the septic system may be disturbed or destroyed with repair work
- Don't put plastic sheets, bark, gravel or other fill over the drainfield or reserve area
- Don't reshape or fill the ground surface over the drainfield and reserve area (just adding topsoil is generally OK as long as it doesn't exceed a couple of inches over the drainfield area)
- Grass or the existing native vegetation are the best covers for your drainfield and reserve area
- Direct all surface drainage areas away from the septic system
- Use shallow-rooted plants (see plant list below)
- Avoid water-loving plants and trees
- Do not make ponds on or near the septic system and the reserve area
Suggested plant list (provided by Washington Sea Grant Program):
Groundcovers for sun:
- Bugleweed (Ajuga)
- Carpet heathers (Calluna)
- Cotoneaster (Cotoneaster)
- Ground Ivy (Glechonma)
- Kinnickinick (Arctostapylos)
- Periwinkle (Vinca)
- Soapwort (Saponaria)
Groundcovers for shade: