ATT Septic Systems in Molalla, OR

There is no single “ATT system.” It’s a term that refers to a broad category of advanced treatment technologies, each suited to different site conditions and regulatory requirements. Legacy Valley installs and services the most common ATT system types found throughout our region of Oregon:

Aerobic Treatment Units (ATUs)

Aerobic Treatment Units use oxygen to accelerate the breakdown of organic waste, producing a significantly higher quality of treated effluent than a conventional septic tank. The treated effluent can then be dispersed through a smaller, shallower drain field, making ATUs a practical option on lots where space or soil depth is limited. ATUs require regular maintenance, including inspection of the aerator, cleaning of components, and periodic effluent sampling.

Best for: Lots with limited drain field space, shallow soil depth, or proximity to sensitive water resources.

Mound Systems

A mound system elevates the drain field above the natural ground surface by constructing a raised bed of engineered sand and gravel. Effluent is pumped from the septic tank up into the mound, where it filters through the engineered media before reaching the native soil below. Mound systems are one of the most common ATT solutions in Oregon and are frequently required on properties with high water tables or slowly permeable soils.

Best for: Properties with high seasonal water tables, slowly draining soils, or insufficient depth to restrictive layers in the ground.

Drip Irrigation Systems

Drip irrigation systems distribute treated effluent through a network of small-diameter tubing installed just below the soil surface, delivering effluent slowly and evenly across a larger dispersal area. Because they distribute effluent so gradually, drip systems place minimal hydraulic stress on the soil and can function effectively on sites where conventional pressure-dosed systems would saturate the ground. They require regular monitoring and maintenance of the distribution tubing and filtration components.

Best for: Sites with limited available area, variable topography, or soil conditions that require slow, controlled effluent delivery.

Pressure Distribution Systems

A pressure distribution system uses a pump to distribute effluent evenly across all areas of a drain field simultaneously, rather than allowing it to gravity-flow into just one section at a time. By spreading the hydraulic load more evenly, pressure distribution systems prevent localized saturation and extend the life of the drain field significantly. They’re often used in conjunction with other ATT components as part of a larger system design.

Best for: Properties where even effluent distribution is needed to prevent premature drain field saturation, or as a component of a more complex ATT system.

Sand Filter Systems

Sand filter systems pass effluent through a bed of engineered sand before it reaches the drain field or dispersal area. The sand acts as a highly effective biological and mechanical filter, removing pathogens and reducing the biological oxygen demand of the effluent to levels that the native soil can safely handle. Sand filters can be open or recirculating, depending on the level of treatment required.

Best for: Sites requiring a high level of effluent treatment prior to dispersal, particularly near sensitive water bodies or in areas with regulatory restrictions on effluent quality.