Pressurized Private Onsite Wastewater Treatment Systems (POWTS)
All pressurized POWTS stated in this section can utilize the mechanical components mentioned in the in-ground gravity POWTS section of this website. The benefits or advantages for use in the pressurized systems are the same as those stated on that site as well. There are additional advantages that can be stated but that is not the primary purpose of this website.
All pressurized POWTS are designed to have wastewater distributed through small diameter holes that are drilled into the piping network at a specified size and distance apart from one another. Through the pressurization process the predetermined wastewater dose volume is sent throughout the pressurized piping network to be distributed throughout the entire POWTS cell.
Reasons for Pressurized POWTS
Typically, in this particular area of the state, the reason a pressurized POWTS is designed and installed is due to a limiting site or soil feature. An example of a site limitation might be a small lot size, therefore a particular area that may be available for a POWTS has to be maximized. That would mean getting the absolute most out of an available area by using a unique POWTS design for that site. There are several soil features that require a POWTS to be pressurized. They would be limitations due to soil texture, soil structure, or natural soil wetness. Any one of these specific soil features, or combination of, will cause a particular POWTS design requirement, and these requirements will change based on the soil limitations of each parcel of land soil tested.
Most Common Pressurized POWTS
Most often the pressurized POWTS you will hear about will be one of the following: a mound, an at-grade, or an in-ground pressurized system. You will find that a mound system is most often used where the most limiting soil features are found on a given site. Most often the soil limitation is due to a seasonal high groundwater table. Water does not necessarily have to be observed at the time that the soil test is being completed. The soil tester will look for soil features that are left behind when seasonal water has been present. These features are called "Redoximorphic features," often referred to as soil mottling. Based on the degree and extent of this mottling as well as its vertical orientation in the soil boring that the soil tester is evaluating, will determine what type of POWTS the site may be suitable for.
You will find that in Kenosha County about two-thirds of the County will have the lower soil strata (layers) are of a clay type texture which results in a very slow infiltration rate. This slow infiltration rate means that the water that is in the soil stays there for extended periods of time. It is during this extended time frame and several additional factors that the redoximorphic features (soil) will be created. Where mottles exist at less than 36 inches below the soil surface a mound system will be the type of POWTS installed. A long narrow design of mound POWTS and at-grade POWTS are preferred in lieu of a short wide design due to the slow percolation rate previously discussed. The reason for the long narrow design is to reduce the gallons of wastewater distributed per lineal foot of system area. See a diagram of a mound system (PDF).
You will find that the design of the at-grade POWTS differs from the mound POWTS in that the at-grade will not have any additional sand material trucked to the site for use under the pressurized pipe distribution system as mound systems do. The at-grade POWTS is used on sites where the soil redoximorphic features exists from 36 inches - 45 inches below the natural ground surface. There are very few at-grade POWTS in Kenosha County due to the extent of redoximorphic features that exist in the soils of this county. See a diagram of a at-grade system (PDF)
The last of the pressurized POWTS is the in-ground pressure. The in-ground pressure system is installed where redoximorphic features exist at more than 45 inches below the natural ground surface and where soil texture or soil structure is of concern. With exception to the redoximorphic features and the pressurized portion of the POWTS the design and construction of the system is the same as the gravity in-ground system.