What is an “Alternative” Septic System?
The majority of the septic systems installed in Jefferson County are “conventional” systems. These systems consist of a septic tank and drainfield. The drainfield typically is from 12 to 36 inches deep and uses gravity to move effluent into the drainlines.
“Alternative” systems are being required on some limiting sites. These systems differ from conventional systems in their complexity and design. For these reasons, alternative systems must be designed by a licensed engineer or licensed designer.
For all their differences, however, alternative and conventional systems have much in common. Like conventional systems, alternative systems use a tank to provide initial treatment. Most of them also use the soil for final treatment. Since state law prohibits discharge of wastewater to ground surfaces, all septic systems rely on the soils for final disposal. Some sites, therefore, may still be unsuitable for even “alternative” system installation. What sets “alternative” systems apart is their capacity to achieve a greater degree of effluent treatment than conventional systems. The amount of treatment depends on the type of system used. Operations and maintenance agreements are also required on alternative systems. This agreement is administered by the Public Utility District.
Alternative systems generally fall into four different types: pressurized drainfields, mounds, sand filters and patented devices.
PRESSURIZED DRAINFIELDS
The pressurized drainfield is the simplest of the alternative systems. Like conventional systems, household waste first enters the septic tank. The clarified water called effluent, then flows into a watertight chamber that contains a small effluent pump. When the level rises to a prescribed level, the pump turns on and pushed effluent into the drainfield either on demand or a timed cycle called a dose. Unlike conventional systems that use 4-inch pipe with large perforations, the pressurized drainfield uses 1 to 2 inch pipe. Use of the small pipe and a small number of drainholes allows the system to pressurize very quickly. In this way, all areas of the drainfield receive equal amounts of effluent. In addition to providing equal distribution to all areas of the drainfield, the pressurized system allows soil to dry out between doses. These two techniques accomplish the level of enhanced treatment required for some sites.
MOUNDS
Mounds are used in areas with soil depth as little as 18 inches and pretreatment of the effluent is required prior to disposal into the ground. The mound is a pressurized drainfield built on a specially constructed fill. The effluent is pumped to the mound where it percolates through the sand fill. This is a substantial amount of treatment within the mound and then some treatment in the native soils underlying the sand fill.
SAND FILTER
Sand filters are used when site conditions are fairly limiting. Like mounds, sand filters use a pump to send the effluent to a specially constructed fill. The fill, or filter, is usually built below ground surface. What makes the sand filter different from a mound is that it is built within a plastic barrier that collects the treated effluent, which is then pumped, to a pressurized drainfield. This type of system affords the greatest degree of treatment and can be used when site conditions prohibit the use of a mound or other system.
PATENTED DEVICES
There are patented devices that accomplish an acceptable level of affluent treatment. These devices require approval by the Washington State Department of Health. A list of approved devices can be obtained from the health department.
NEED HELP?
No-cost assistance is available in the following ways:
Information on financial assistance which may be available to property owners to repair or upgrade their on-site sewage systems.
General information on septic systems and water quality.
Workshops for understanding, operating and maintaining your on-site sewage system.
FOR MORE INFORMATION CONTACT:
Jefferson County Public Health
Environmental Health Division
615 Sheridan
Port Townsend WA 98368
360.385.9444
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