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A Soil Test is the first step for installing a new or replacement Septic System or formally known as a Private Onsite Wastewater Treatment System (POWTS). The results of the soil test determine what type of system will be required for each specific site.  The days of boring a hole and utilizing water to rate a soil's hydraulic conductivity are behind us. 

Now soil tests are performed by digging a hole with a backhoe and analyzing each soil layer by its physical characteristics. Examples of these characteristics are the soil type, structure, consistency, moisture content, and particle size. Once these have been determined, a hydraulic rating is assigned to each layer.

The location within the property is evaluated for limiting factors. A limiting factor is a layer of soil that consists of either periodic high ground water or bedrock. For a septic system, three feet of separation is required between the elevation in which effluent water is discharged in the absorption cell and the limiting factor below. If either high ground water or bedrock is found close to the surface, the required three feet of separation may not be feasible and proper treatment of the effluent water will not be obtained before it enters back into the water table.

Once a soil test has been completed, the septic system plans can be designed. Upon completion of the plans they are submitted to the State and/or County for review before a sanitary permit can be issued. A sanitary permit must be obtained prior to the start of installing a new system. For a conventional system, each County's Planning and Development Department approves the plans. For a mound or holding tank, the plans must also be approved by the Wisconsin State Department of Commerce. For new construction and remodeling, a sanitary permit must be obtained before a building permit can be issued.

The function of a holding tank is to serve as a temporary reservoir for effluent to a waste water treatment plant. Unlike other types of systems, an absorption field is not utilized. Collected effluent is pumped from the tank by a Licensed Waste Hauler into their truck and hauled off. A three-bedroom home, usually requires a tank five feet in diameter by eighteen feet long. This tank has a volume of 3000 gallons and is constructed of carbon steel. The size and volume of the tank depends on the number of bedrooms in the house. An alarm float is installed in the tank and is connected to a visual and audible alarm inside the house. The alarm is to let the homeowner know that the tankneeds to be pumped as soon as possible.

A holding tank is one of the most restricted types of systems that can be installed in Wisconsin. The following criteria must be met:

• The soil and site cannot be suitable for any other Wisconsin Department of Commerce approved Private Onsite Wastewater Treatment System (POWTS). (ie. A mound or similar system must be ruled unsuitable)
• The property must have holding tank "rights". This can be checked by contacting your local County Planning and Development Department.
• A holding tank pumping agreement form needs to be signed indicating that as the homeowner, responsibility will be taken to have the tank pumped as required (generally every three to four weeks).

Holding tanks are generally installed in sites that are too small for a different type of system, or the water table in the area is too high to allow for proper treatment of the effluent (wastewater). Due to the high level of maintenance and frequency of pumping for a holding tank system, this type of system, in the long run, is more work and costs the homeowner more money than standard POWTS systems.

In July of 2000, the Wisconsin Department of Commerce issued a Code requiring that if a holding tank is installed, a water meter must be installed inside the house, on the incoming water line along with an outside reader. This meter must be installed by a contractor with a Master Plumber License, such as Billingsley Engineering.

This type of septic system became known as a mound because the entire absorption field is above the ground and forms a mound of dirt in a yard. As you can see from the graphic to the right, the mound consists of nothing more than sand, washed stone, and top soil. Characteristics of a mound, such as length, width, and height, are determined by the soil test performed on the site. The length and width of the mound are determined by the hydraulic rating of the soil. The height of a mound varies based on the depth of the sites limiting factor for the soil. A limiting factor is the elevation in which either a high ground water table exists or bedrock is found.  Tolearn more about limiting factors please see the Soil Test page of this web site. The approximate size of a mound for a three bedroom house is 25' wide, 90' long, and 4' tall.

Now that you know what determines the physical characteristics of a mound; lets go over the functionality of the system. As the effluent (wastewater) leaves the house, it first passes through two tanks. The first of these tanks is the septic tank. The septic tank (shown above) is know as a double compartment tank and is pre-cast, watertight concrete. For a three-bedroom home, it is typically six feet wide, eight feet long, and five feet tall, with 1000 gallons in capacity. The size and volume will change depending on the number of bedrooms in the house.

The primary purpose of the septic tank is to act as a temporary reservoir that allows time for the solids to settle to the bottom creating a sludge layer and fats to float to the top creating a soft layer of crust. As the effluent is retained in the tank, natural bacteria biodegrade the majority of the solids leaving a partially clarified liquid. Inside the septic tank is a baffle (wall) that retains the majority of the solids and fats in the first compartment. In the second compartment there is a filter. With the combination of a double compartment tank and a filter, the probability of keeping solids from flowing down to the pump tank is greatly increased. The filter must be cleaned periodically to keep it from becoming plugged.

After the effluent has been partially treated and filtered in the septic tank, it flows down to the second tank, the pump tank. The pump tank, like the septic tank, is constructed of pre-cast concrete and is watertight. However, it does not have two compartments. It typically is six feet wide, seven feet long, five feet tall, with a volume of at least 770 gallons. It may be larger depending on individual site restrictions.

Inside the pump tank is an effluent pump operated by two separate floats. The first float controls the pump on and off settings. The second float is an alarm float, which is connected to the alarm box that is mounted inside the house. This alarm will sound, audible and visual, if there is any malfunction with the effluent pump

A water resistant junction box is mounted on the pump tank riser. THis is where the electrical connections for the pump and alarm are made inside a junction box. All risers that are above the ground surface have warning labels and are locked with a cable and padlock. It is important to ensure that the risers are locked at all times to avoid accidental entry that could result in injury or death.

The absorption cell, commonly known as the "mound", is where the effluent treatment is finalized before it reenters the underground water table. The mound consists of a layer of sand on the bottom, a cell of washed stone placed in the middle, and then covered with a layer of topsoil that will support vegetation. Typically, two laterals (PVC pipe) 1 ½" in diameter are placed in the gravel cell with 3/16" holes drilled in the bottom. When the effluent pump in the pump tank turns on, the water is pumped into the laterals and is dispersed evenly through the holes in the laterals and into the gravel. As the water percolates through the stone and sand, it is naturally filtered leaving all of the bacterial and harmful substances behind before entering the water table.