| Company | Location | Certifications | License # |
|---|---|---|---|
| Austin Creek Services Inc | Santa Rosa, CA | Installer (C-42) | 1054040 |
| Bdk Septic Service | Santa Rosa, CA | Installer (C-42) | 802125 |
| Berry Kevin Lee | Cotati, CA | Installer (C-42) | 458868 |
| Bohan & Canelis General Engineering Inc | Cazadero, CA | Installer (C-42) | 829905 |
| C & C Contracting | Cotati, CA | Installer (C-42) | 823983 |
| Drew Underground Construction | Santa Rosa, CA | Installer (C-42) | 484067 |
| Ghilotti Construction Company Inc | Santa Rosa, CA | Installer (C-42) | 644515 |
| Horobin Construction Inc | Forestville, CA | Installer (C-42) | 746917 |
| Jfm Septic System Installation Llc | Forestville, CA | Installer (C-42) | 1068533 |
| Keller Charles Construction Inc | Petaluma, CA | Installer (C-42) | 885844 |
| La Bare Nicole | Penngrove, CA | Installer (C-42) | 1070414 |
| Masterson Bryan Enterprises | Petaluma, CA | Installer (C-42) | 271933 |
| Maverick Excavating Inc | Santa Rosa, CA | Installer (C-42) | 1041206 |
| Miller M M Construction | Geyserville, CA | Installer (C-42) | 865112 |
| Moore Home Services | Santa Rosa, CA | Installer (C-42) | 1051850 |
| Neighbor Homes | Santa Rosa, CA | Installer (C-42) | 357397 |
| Nicholas Johnson Innovative Systems Inc | Forestville, CA | Installer (C-42) | 462989 |
| Ongaro & Sons | Petaluma, CA | Installer (C-42) | 215233 |
| Paul Michael Company Inc | Petaluma, CA | Installer (C-42) | 386001 |
| Peterson Mechanical Inc | Sonoma, CA | Installer (C-42) | 171486 |
| Rebich Construction Inc | Windsor, CA | Installer (C-42) | 675200 |
| Redwood Septic Services | Petaluma, CA | Installer (C-42) | 1158226 |
| Roy'S Sewer Service Inc | Cotati, CA | Installer (C-42) | 491815 |
| Sanitary Solutions Corp | Santa Rosa, CA | Installer (C-42) | 1153958 |
| Trinity Oak'S Septic Service | Glen Ellen, CA | Installer (C-42) | 882951 |
25 companies in the CSLB Licensed C-42 Sanitation System Contractors are based in Sonoma County as of 2026-07-23. Companies based elsewhere in California also commonly serve the county.
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