| Company | Location | Certifications | License # |
|---|---|---|---|
| Advantage Contractors | Columbia, MO | Installer (Level Advanced) | 37656 |
| Atephac. | Columbia, MO | Installer (Level Basic) | 38578 |
| Benchmark Excavating Llc | Foristell, MO | Installer (Level Advanced) | 32357 |
| Bill Binkley & Sons Excavating Llc | Jefferson City, MO | Installer (Level Advanced) | 34313 |
| Bw Dirt Works & More Llc | Westphalia, MO | Installer (Level Advanced) | 38783 |
| Doug Briot Bobcat Service Landscaping Co | Henley, MO | Installer (Level Advanced) | 31248 |
| Fleer Excavating | Hermann, MO | Installer (Level Basic) | 39449 |
| Gilbert & Sons Construction Inc | Montgomery Ctiy, MO | Installer (Level Basic) | 35894 |
| Green Shore Excavating | Barnett, MO | Installer (Level Advanced) | 37022 |
| Greg Wickam Excavating | Eldon, MO | Installer (Level Advanced) | 37914 |
| Groose Heating & Cooling | Eugene, MO | Installer (Level Advanced) | 31647 |
| Hackmann Trenching & Backhoe Llc | Chamois, MO | Installer (Level Basic) | 37373 |
| Jody Schmidt Well & Sewer Service | New Melle, MO | Installer (Level Advanced) | 31768 |
| Meyerott Enterprises, Llc | St. Charles, MO | Installer (Level Advanced) | 38368 |
| Post Contract Services | Ashland, MO | Installer (Level Advanced) | 35165 |
| Semke Grading And Pipe | Saint Charles, MO | Installer (Level Basic) | 37584 |
| Volz Incorporated | Saint Louis, MO | Installer (Level Advanced) | 39038 |
17 companies in the Missouri DHSS registered OWTS installer list are based in Callaway County as of 2026-07-23. Companies based elsewhere in Missouri also commonly serve the county.
Tell us what you need — we'll connect you with state-certified companies serving your area. No obligation.