Landscaping and Other Activities on Your Property

If you live outside the service area of a sewer district you most likely have a septic tank and a drainfield to treat your household wastewater. If designed and installed properly, these systems can usually function for many years-- as long as they aren't damaged. The major causes of septic-system damage are failure to pump the tank regularly (not covered in this document) and physical destruction of the drainfield. This document will discuss special considerations for landscaping and other land uses to avoid damage to your septic system.

The first step is to identify the location of your septic tank and drainfield. If you don't know the location, check with y our County Development or Environmental Health office. If you are in the process of installing a new system, give careful consideration to the location of your septic tank and drainfield based on your plans for landscaping or other land uses.

Septic Tank

Newer tanks have service ports that extend above ground, so you can't "loose" them. Older tanks are usually buried 6? to 2? or more, and they are often difficult to locate when it comes time to pump. The worst case is that a sidewalk, driveway, or building is constructed above the septic tanks by a landowner unaware of its location. Once this has happened the tank cannot be pumped regularly, and failure in inevitable. Less serious is the inconvenience that results when digging up exploratory holes around your yard to locate the tank and the damage to the landscaping above the tank. And finally there is the possibility of damage to the tank from roots of trees unknowingly planted too close to the tank.

Some suggestions for landscaping above and around a septic tank include:

• Set a birdbath, potted plant or lawn ornament directly above the access port to mark the tank.

• Plant grass or low-value herbaceous vegetation over the tank so you won't hesitate to damage the plants in order to service the tank.

• Do not plant trees so close to the tank that someday their roots may reach the tank. Roots usually extend further than branches! Think long-term-trees and septic tanks both have long lives.

• Be creative when trying to hide an aboveground access port. Consider tiered planter boxes, a row of shrubs to block the line of sight (but not too close to the tank-roots), a bird-feeding station, or whatever fits your landscape and personal taste.

Drainfield

The drainfield area is much larger than the septic tank, and much more susceptible to damage. The soil above the leach lines must remain able to breathe, so any activity that compacts the soil puts the system at risk. Additionally, there is the risk of crushing the drain lines. Some guidelines for protecting the drainfield include:

• Do not drive anything larger than a riding mower over this area-if you must occasionally cross this area with a larger vehicle, make sure the soil is dry, or put down track boards to distribute the weight.

• Keep large animals off of the drainfield. If you choose to have the area grazed, remove the animals before any bare soil is evident and NEVER during the wet season, and be aware that you are taking a risk.

• Do not add or remove or rearrange any soil from this area. The depth to the leach lines has been designed specifically for your soil and site conditions.

• Optimally, the drainfield should be planted in grass. Grass roots actually aid in the functioning of the system as a whole. Other herbaceous plants are also O.K.

• Do not plant a garden over the drain field. The risk of compaction from tilling, heavy watering, and paths is too great. Also, building beds may make the soil too deep for air to reach the treatment zone.

• Keep trees away at least 25? or so from the drainfield. Be aware that roots of some types of trees are particularly bad at clogging drain lines. The worst are willows, alder, poplars, and cedars. Less risky are maple and fruit trees. Conifers other than cedars do not seem to cause as much of a problem, but may if given a chance. Junipers are often left standing between drain lines in dry regions, but the homeowner should be advised of the risk they are taking.

• If you do have trees near your drainfield or septic tank, consult with both a septic system professional and an arborist to determine if the trees should be removed. You need to weigh the value of the tree to your landscape against the likely risk to the septic system.

• Do not cover the drain field with any structure that may prevent air from moving through the soil. This is not a good place for an aboveground pool, gazebo, R.V. pad, storage shed, basketball court, riding arena, or patio.

Sand-filters

Sand-filters are a special type of treatment between the septic tank and drainfield. They are quite expensive and you will most likely be aware that you have one. Sand-filters are typically a box about 16? x 20? (sizes vary) that often sits a foot or two above ground. Manufactures recommend that the top of the sand-filter by planted in grass, and that creative landscaping be avoided. If you are tempted to do any planting in the sand-filter besides grass, check with the installer or manufacturer first. If you wish to disguise the fact that you have a sand-filter consider planting a shrub-wall around it or build a trellis for vines.

Failing Septic Systems

It is normal for there to be stripes over the septic system, especially during the summer-the grass above the drain lines may be either greener or browner, depending on your situation-this is a good way to locate the lines, and is not a sign of failure. However, if the ground is spongy or the grass is so lush that you can't mow it, you most likely have a problem. Do not try to fix this with landscaping solutions such as fertilizer, added soil, reseeding, or the like. Call a septic system repair professional.