Septic installation and replacement in Jefferson County, Missouri
The trap in Jefferson County is the name. The septic permit does not come from a health department, it comes from Jefferson County Code Enforcement in Hillsboro, and a search for "Jefferson County health department" will land you on an agency in Alabama with a similar name. The county runs its own On-Site Sewage Treatment Code, and it licenses the people who work on your system itself, on top of the state registration they already need. Those county licences carry a bond and an insurance requirement, which is unusual in Missouri and worth knowing before you compare quotes.
Who issues a septic permit in Jefferson County, MO?
The Jefferson County Code Enforcement. That is the office to call before anything else, because in Missouri the permitting authority is not the same kind of agency in every county, and assuming it is the health department wastes a week in the counties where it is not.
Phone (636) 797-5310. Their page: Jefferson County Code Enforcement.
Source: Missouri Department of Health and Senior Services, onsite wastewater construction permit authority lookup for Jefferson County, read 2026-08-26. Fees, forms and requirements change, and this county is the only current source for its own.
What does Jefferson County require beyond the state standard?
- The county has adopted its own On-Site Sewage Treatment Code, Chapter 705, alongside its building code. Source: Jefferson County, Codes and Ordinances, read 2026-08-26.
- The county issues its own licences for onsite soil evaluator, onsite sewer system designer and onsite sewer system installer, on top of Missouri state registration, and requires the applicant to hold and maintain that state registration in good standing. Source: Jefferson County, On-Site Soil Evaluator License Registration packet, read 2026-08-26.
- Each of those county licences also requires a twenty-five thousand dollar bond with the county as obligee, and liability insurance carrying a one million dollar aggregate limit and a two hundred and fifty thousand dollar per-occurrence limit naming the county as certificate holder. Source: Jefferson County, license registration packets, read 2026-08-26.
- Three full sets of sealed plans and soils reports must be submitted with the permit application, and a new home requires a soil morphology report with four sample pages. Source: Jefferson County, On-Site Sewage Treatment System Permit Application, read 2026-08-26.
- A final inspection must be completed on every permit, and the application warns that failure to comply can result in disconnection of applicable utilities and stoppage of work. Source: Jefferson County, On-Site Sewage Treatment System Permit Application, read 2026-08-26.
Missouri lets a county adopt standards more restrictive than the state's, so a requirement here is not evidence of the same requirement one county over.
Source: Missouri Department of Health and Senior Services, Onsite Wastewater Treatment, read 2026-08-26.
What is the ground like in Jefferson County?
Jefferson County is Ozark karst: shallow soil over fractured limestone and dolostone, with loess-mantled ridges and alluvium along the rivers. It sits south and east of the Missouri River, so despite being a St. Louis collar county it is not till country. The consequence is that depth to bedrock, rather than percolation rate alone, is often what decides the system, and the four-foot separation requirement for cherty clay soils in areas of severe geological limitations is a live constraint rather than a footnote.
That matters because the soil decides the system. A standard system needs at least one foot between the trench bottom and the limiting layer or seasonal high water table, rising to four feet to groundwater or bedrock in highly permeable soils and in cherty clay soils in areas of severe geological limitations, and a percolation rate slower than sixty minutes per inch pulls a registered engineer onto the design.
The soil evaluation is what settles it for your particular lot.
Source: 19 CSR 20-3.060(5)(A)2., Missouri Code of State Regulations, read 2026-08-26.
Which towns does this cover?
Jefferson County has Hillsboro as its county seat. Places served include Arnold, Festus, Crystal City, De Soto, Herculaneum, Pevely, Byrnes Mill, Kimmswick, Cedar Hill, High Ridge, Imperial, Barnhart. Anywhere in the county not on a public sewer is on a system this page applies to.
Who is allowed to do the work here?
An installer registered with the Missouri Department of Health and Senior Services. That is a state requirement rather than a county one, and it applies wherever you are. Some counties add their own licensing on top of it, which is one more reason to ask the permitting authority what they require before you sign anything.
How to check an installer's registration takes one phone call.
Source: Section 701.031, Revised Statutes of Missouri, read 2026-08-26.
What we could not confirm for this county
The text of Chapter 705 itself was not read in full, so the county ordinance is confirmed to exist and to carry the requirements above rather than being summarized end to end. The Code Enforcement Division states that it regulates construction in unincorporated Jefferson County, so requirements inside incorporated cities may differ. Fee amounts are set by county ordinance and change, so no figure is repeated here.
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Tell us the county and the jobLast reviewed 2026-08-26.