Septic Systems

Around one third of Minnesotans rely on septic systems to treat their wastewater. Also referred to as subsurface sewage treatments systems (SSTS), septic systems utilize the power of the soil beneath our feet to remove pathogens and other contaminants from sewage so it can be safely returned to the water cycle.

In the typical system, raw sewage is collected by the plumbing in the home and delivered to the septic tank. There the light solids float to the top, forming a scum layer, and the heavy solids sink to the bottom, forming sludge.

In the tank, organic solids such as food particles and human waste are decomposed by millions of naturally occurring bacteria.

The septic tank delivers the partially treated liquids, or effluent, to the soil treatment area. Effluent contains pathogens (disease-causing organisms), nutrients, and some fine solids. A thin layer of fine solids, dead bacteria, and soil bacteria, called a biomat, forms naturally where the effluent enters the soil. The biomat restricts the flow sufficiently to keep the soil beneath unsaturated.

The unsaturated soil contains oxygen which allows aerobic bacteria to live and destroy pathogens. These air spaces also force nutrients such as phosphorus and sodium to come in direct contact with soil particles to which they become attached. A portion of the nitrogen passes through into the groundwater. After passing through the unsaturated soil, the now harmless water evaporates into the air or returns to the soil and groundwater system. In regular septic tanks, the bacteria are anaerobic, that is, they live without air in the liquid. In aerobic tanks, the bacteria are aerobic and require air to live.

This article is for informational purposes only. Inspired by the University of Minnesota.

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Septic Design and Installation Services in MN and WI

When it comes to reliable septic system solutions, Wieser Septic & Excavating specializes in providing top-tier design and installation services across Minnesota and Wisconsin. Whether you’re building a new home or upgrading an outdated system, our team has the expertise to ensure your septic system is safe, efficient, and built to last.

Customized Septic System Design

Every property is unique, and so is its septic system. Our certified designers evaluate your land, soil composition, and water usage to create a system tailored to your specific needs. From single-family homes to commercial properties, we ensure compliance with all local and state regulations.

Our Design Process Includes:

Site Evaluation: Assessing soil quality, groundwater levels, and property layout.
System Type Selection: Recommending conventional, mound, or advanced treatment systems based on your property’s needs.
Permit Assistance: Handling required permits to ensure a smooth approval process.

Professional Installation You Can Trust

Installing a septic system is a complex process that requires precision and attention to detail. Our skilled team at Wieser uses advanced equipment and techniques to complete the job efficiently while minimizing disruption to your property.

Installation Services Include:

Excavation and preparation
Tank and drain field installation
System connection and testing
Final site restoration

Why Choose Us for your Sewer Design, Replacement, and Installation?

Local Expertise: With years of experience serving MN and WI, we understand regional challenges like harsh winters and varying soil conditions.
Regulatory Knowledge: We ensure every system meets local codes and environmental standards.
Customer-Centered Approach: We work closely with homeowners, builders, and contractors to deliver exceptional results.

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To start off, let’s give you some general information on the basic types of septic systems and some fundamental basics of each:

"Trench Septic System"

A Trench is defined as a soil treatment and dispersal system, the absorption width of which is 36" or less. Trenches are narrower than they are wide, no wider than three feet, and are laid out along the contours of the soil. The method of distributing the effluent in the septic tank can be either pressure or gravity. The trench soil treatment system consists of distribution media, the bottom of which must not be deeper than 48 inches, covered with a minimum of 12 inches of soil and a close-growing and vigorous vegetation. Many Trench systems utilize a pipe and a gravel distribution system where effluent passes through the pipe and is stored within the media until it can be absorbed into the soil.

"AT-Grade Septic System"

An At-Grade, as its name implies, is a system installed with the distribution media placed at the original soil surface. It is designed to solve similar issues as the mound, but where the soil conditions are somewhat more favorable. The operation of the at-grade component is a two-stage process involving both effluent treatment and dispersal into the underlying soil. Treatment is accomplished predominately by physical and biochemical processes within the soil. These processes are affected by the physical characteristics of the effluent wastewater, influent application rate, temperature, and the nature of the receiving soil. The At-Grade component contains a septic tank(s), pump tank, and distribution system that consists of distribution media and a pressure distribution system, which is installed directly on top of the plowed natural soil and covered by loamy or sandy cover material and topsoil. Effluent flows into the soil, where it undergoes biological, chemical, and physical treatment and dispersal into the environment. The natural soil serves as the treatment medium and disperses the effluent into the environment.

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"Mound Septic System"

Mound systems were developed in the early 1970s to overcome soil and site conditions, which limited the use of trenches and beds. Limited conditions include high water tables, shallow soil depth to bedrock, slowly permeable soil, or soil too coarse for treatment. A sewage treatment mound is nothing more than a seepage bed elevated by clean sand fill to provide adequate separation between where sewage effluent is applied and a limiting soil layer. The mound system consists of a septic tank(s) followed by a pump tank. Effluent is dispersed evenly via the pump into the absorption bed, where it flows through the clean sand material and undergoes biological, chemical, and physical treatment. It then passes into the underlying soil for further treatment and dispersal to the environment. A minimum of 12 inches of cover material, which is crowned to shed water, is placed over the top of the mound, with the upper 6 inches being topsoil.

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"Seepage Bed Septic System"

A seepage bed system is a wide area (wider than three feet) prepared to accept septic tank effluent. It is created below the surface of the soil and built the same way as a trench system. Seepage beds treat the effluent effectively as long as they are located in appropriate soils. A seepage bed is defined as a soil treatment and dispersal system, the absorption width of which is greater than three feet but no greater than 25 feet. They can use either gravity or pressure distribution. The construction of a seepage bed is essentially the same as that for a trench, except the bed is wider. In Minnesota, the bottom area of seepage beds with gravity distribution must be 50% greater than that of trenches to allow for the fact that there is little sidewall with a seepage bed and low oxygen transfer. The bottom of the bed must be within 48 inches of the final grade and be covered with at least 12 inches of soil and close-growing and vigorous vegetation.

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"Alternative Septic Systems"

Traditional septic systems are typically thought of as an on-site sewage treatment system serving one household with a drain field or mound. These are probably still the best way to treat sewage when space and good soil conditions exist. When properly designed, installed, operated and maintained, they treat sewage as well as or better than municipal treatment systems.

When space is limited or soil conditions are poor (wet or close to the water table), homeowners may need to consider a modified treatment system. Because a typical septic system does not remove all of the nitrates from sewage, additional treatment steps may be used to reduce or eliminate them. These options may be considered for individual homes or multiple household units.

Typically, alternative treatments provide "pre-treatment" of septic tank effluent before it enters the soil of a drain field or mound. These pre-treatment systems include containers using sand, peat, or gravel as a medium where filtration and biological degradation of fine solids, pathogens, and nutrients occur. The containers may be manufactured or assembled on the site.

The effluent in a pre-treatment system usually passes through the system one time, but some systems collect and re-circulate the effluent several times. These systems often require more space than a traditional drainfield or mound. Research has still to determine if the size or the separation distance of the drain field receiving the pre-treated water will be able to be reduced. These same considerations are being made when aerobic septic tanks are used to pre-treat wastewater.

Alternative methods of dispersing septic tank effluent into the soil are also being tested. These include drip irrigation over a large soil area, particularly appropriate in shallow bedrock and high water table situations. Spray irrigation onto the soil surface is another option, but presents special health risks with potential human contact. Uses of the water for watering lawns and golf courses also offer opportunities to recycle the water.

Separation technology is another concept in alternative treatment for individual homes. The idea of separating the solid wastes from the toilet and delivering them to a composting unit reduces household water use by up to 40 percent and removes many of the pathogens and nutrients from the system. Some systems use worms, while others use bacteria and aeration to accomplish the composting process. Homeowners are sometimes reluctant to have a bin of composting wastes and even worms in their basements. The composted materials must be removed periodically.

Alternative treatment systems will always require increased attention to operation and maintenance. As the treatment becomes more sophisticated and technical, the need for monitoring of its performance increases. Multi-household installations must have a functional management plan.

Most alternative treatment systems require special permits for their design, installation, and operation. Any system discharging to the surface must have a State Disposal System permit, and any system discharging 10,000 gallons per day must have a National Pollutant Discharge Elimination System permit. Both require ongoing monitoring. Information about permits is available from local planning and zoning or environmental service offices.

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