| Company | Location | Certifications | License # |
|---|---|---|---|
| Alan B Flasowski | — | Installer (Class II)Designer (Site Evaluator) | OS0000020 |
| Barry Cole Smith | — | Installer (Class II)Designer (Site Evaluator) | OS0037415 |
| Brady T Russell | — | Installer (Class I) | OS0036168 |
| Chance William Winkelmann | — | Installer (Class I) | OS0038774 |
| Charles Edward Sr Green | — | Installer (Class I) | OS0022014 |
| Cody Kyle Harman | — | Installer (Class II)Designer (Site Evaluator)Inspector (Maintenance Provider) | OS0038023 |
| Cody Stelter | — | Installer (Class II)Designer (Site Evaluator) | OS0039235 |
| Colby William Hodde | — | Installer (Class I) | OS0038775 |
| Creig J Corlis | — | Installer (Class II)Designer (Site Evaluator)Inspector (Maintenance Provider) | OS0029837 |
| Cynthia Renee Hamilton | — | Designer (Site Evaluator) | OS0039045 |
| Darren J Derkowski | — | Installer (Class II)Designer (Site Evaluator)Inspector (Maintenance Provider) | OS0031161 |
| Gabriel Mcwilliams | — | Installer (Class I) | OS0041012 |
| Gregory A Armstrong | — | Installer (Class II)Designer (Site Evaluator)Inspector (Maintenance Provider) | OS0035465 |
| Jack Atkinson | — | Installer (Class II)Inspector (Maintenance Provider) | OS0029048 |
| James Boone Sanford | — | Installer (Class I) | OS0040112 |
| John Ross Kettler | — | Installer (Class I) | OS0041072 |
| Jose Luis Gamboa | — | Designer (Site Evaluator) | OS0039046 |
| Justin R Flasowski | — | Installer (Class II) | OS0009246 |
| Justin V Flasowski | — | Installer (Class II)Designer (Site Evaluator) | OS0000072 |
| Lindsey Carden | — | Installer (Class I) | OS0038263 |
| Luis Javier Sanchez | — | Installer (Class I) | OS0038647 |
| Marcoantonio Bustos | — | Installer (Class I) | OS0039379 |
| Marisa K Rs Harman | — | Designer (Site Evaluator) | OS0032451 |
| Mark Kettler | — | Installer (Class II)Designer (Site Evaluator) | OS0000801 |
| Mark Luke Marzahn | — | Designer (Site Evaluator) | OS0039044 |
| Matthew Monfreda | — | Installer (Class I)Inspector (Maintenance Provider) | OS0039533 |
| Miguel Angel Perez | — | Installer (Class I) | OS0039175 |
| Paul A Brown | — | Installer (Class II) | OS0038669 |
| Riley Logan Saunders | — | Installer (Class I) | OS0038711 |
| Robert A Kettler | — | Installer (Class II)Designer (Site Evaluator)Inspector (Maintenance Provider) | OS0031701 |
| Roland W Wittner | — | Installer (Class I) | OS0002290 |
| Susie M Flasowski | — | Installer (Class I) | OS0000073 |
| Treyton Tillman | — | Installer (Class II) | OS0039910 |
| William A Kmiec | — | Installer (Class II)Designer (Site Evaluator) | OS0036166 |
| William C Hegar | — | Installer (Class II)Designer (Site Evaluator) | OS0005314 |
35 companies in the TCEQ OSSF (On-Site Sewage Facility) occupational licenses are based in Washington County as of 2026-07-23. Companies based elsewhere in Texas also commonly serve the county.
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