Missouri Soil Evaluation and Septic FAQ
If you are planning to build a home, add a bedroom, replace a failing septic system, or buy rural property in Missouri, a soil evaluation is often one of the first steps. In Missouri, the type of onsite wastewater system allowed on a property depends heavily on the soil, slope, available area, and local permitting authority. State standards are set by the Missouri Department of Health and Senior Services, but local authorities may apply stricter rules.
What is a soil evaluation for a septic system?
A soil evaluation is an on site assessment of the soil and landscape to determine what kind of wastewater dispersal system may work on a property. It looks at factors such as soil texture, structure, color patterns related to seasonal wetness, depth to limiting layers, slope, and available area. In Missouri, soil and site limitations are one of the main factors used to determine what type of onsite wastewater treatment system is appropriate.
Why would I need a soil evaluation?
You may need a soil evaluation before building a house, adding wastewater generating space, replacing a failing septic system, or buying rural land that is not served by public sewer. Missouri DHSS states that soil reports provide information about the soil characteristics and site, and that installing the correct type of onsite system helps protect public health and maximize system longevity.
Is a soil evaluation the same thing as a perc test?
Not always. A perc test and a soil morphology evaluation are different approaches. Missouri currently recognizes both, but a soil morphology evaluation is preferred and uses direct observation of the soil profile and site conditions rather than relying only on water movement in test holes. Under Missouri rules, anyone conducting a percolation test or soil morphology evaluation for OWTS design must be properly registered with the department.
Who can perform a septic soil evaluation in Missouri?
Missouri requires registration for individuals who conduct percolation tests or soil morphology evaluations intended for onsite wastewater system design. State law also prohibits allowing an unregistered person to perform that work for design purposes.
What factors can make a site unsuitable for a conventional septic system?
Common limitations include shallow depth to bedrock, seasonal water table indicators, very restrictive clayey subsoil, steep slope, limited usable area, drainageways, and setback conflicts. Missouri DHSS notes that the most limiting factors are often the soil resource, site limitations, and space limitations.
Can a property still work if it will not support a conventional septic system?
Sometimes, yes. A site that is not suitable for a conventional gravity trench system may still allow a more advanced onsite system, depending on the specific limitations and the amount of suitable area available. Missouri distinguishes between basic systems and advanced systems. Advanced systems can include options such as sand filters, sand mounds, low pressure pipe distribution, drip dispersal, pressure distribution to conventional sized fields, modified shallow systems, and other systems using fill soil. Final approval depends on the site and the permitting authority.
Do I need a permit for a septic system in Missouri?
In most cases, yes. DHSS states that a construction permit is required before installing or repairing most onsite wastewater treatment systems. For residential property under three acres, a construction permit is required, though some county specific exceptions may apply. Non residential structures served by onsite systems generally require a permit regardless of acreage. Always check the county or other local permitting authority where the property is located.
Who issues septic permits in Missouri?
In many counties, the local health department handles permits. In others, the authority may be DHSS, a local authority under contract, or a local authority operating under ordinance. Some areas may also use another agency such as a sewer district, building department, or planning and zoning department. The permitting process depends on where the property is located.
Does Missouri have a minimum lot size for a septic system?
Where the state onsite laws apply, Missouri does not set one universal minimum lot size. However, counties with local wastewater ordinances may have restrictions, and subdivisions may have approved minimum lot sizes tied to wastewater treatment. Lagoons also usually require more land because of larger setback requirements.
Can I install my own septic system as a homeowner?
Sometimes, but it depends on the local permitting authority and the type of project. Missouri DHSS says that in some instances homeowners may install their own system, but they should first check with the local authority and determine whether a permit is required. DHSS also strongly encourages property owners to work with a registered installer.
Is it legal to pipe wastewater into a ditch or let it discharge on the ground?
No. Missouri DHSS states that a system cannot pose a threat to public health or the environment, and its FAQ specifically answers this question with a no.
What kinds of systems are regulated by Missouri DHSS, and when does DNR get involved?
DHSS generally regulates single family residential onsite systems, including single family residence lagoons, and onsite or cluster domestic wastewater systems with flows of 3,000 gallons per day or less that disperse through soil treatment or absorption systems. Missouri DNR regulates other wastewater treatment systems, including lagoons serving anything other than a single family residence, systems discharging to surface waters, systems over 3,000 gallons per day, and systems handling industrial wastewater.
What happens during a soil evaluation visit?
A soil evaluator typically reviews the site, observes slope and landscape position, digs or examines test pits, evaluates the soil profile, identifies limiting layers or seasonal wetness indicators, and determines whether there is enough suitable area for wastewater dispersal. The findings can help guide system selection and permit planning. In Missouri, the state site evaluation form and permit instructions both rely on site and soil information such as slope and soil data for system design.
What should I have ready before scheduling a soil evaluation?
It helps to have the property address, parcel information, a rough site plan if available, and a general idea of where the proposed house or structure will sit. If utilities, property lines, easements, ponds, drainageways, or wells are known, that information is useful too. The more clearly the usable area is understood, the more efficient the evaluation can be.
Can a soil evaluation help before I buy land?
Yes. A pre-purchase soil evaluation can help identify whether the property is likely to support an onsite wastewater system, whether a conventional system is possible, or whether significant limitations may lead to added cost or restricted building options. For rural properties, this can be one of the most important due diligence steps before closing.
What areas do you serve?
Richner Soil Services serves clients in several counties in Southwest and West-Central Missouri who need soil evaluations for onsite wastewater planning, septic design support, and related site review. Contact us to confirm service in your county and discuss your project.
How do I schedule a soil evaluation?
Use the contact page or call directly to discuss your property, location, and project goals. We can help you determine whether you likely need a soil evaluation, what information to gather before the visit, and what the next steps may be with your local permitting authority.