| Business | Phone |
| Bell Engineering Inc 138 Oak Shadow Dr, Santa Rosa 95409 | (925) 443-6446 |
| Cancio Engineering 438 1st St, Santa Rosa 95401 | (707) 569-8511 |
| Engineering Technical Svc 146 Wikiup Dr # A, Santa Rosa 95403 | (707) 546-4300 |
| Horn Engineers 521 Mendocino Ave, Santa Rosa 95401 | (707) 546-1332 |