| # | Company name | Role | # of projects |
|---|---|---|---|
| 1 | Machta Daniel Engineer | Geotechnical engineering | 14 |
| 2 | MACTEC Engineering and Consulting, Inc. | Geotechnical engineering | 9 |
| 3 | Mason-Johnston & Associates | Geotechnical engineering | 2 |
| 4 | Materials Testing and Inspection, Inc. | Geotechnical engineering | 1 |
| 5 | Matrix Laboratory | Geotechnical engineering | 4 |
| 6 | McCallum Testing Laboratories | Geotechnical engineering | 1 |
| 7 | McClelland Engineers, Inc. | Geotechnical engineering | 1 |
| 8 | McClymont & Rak Engineers, Inc. | Geotechnical engineering | 4 |
| 9 | McClymont & Rak Engineers, Inc. | Geotechnical engineering | 6 |
| 10 | McPhail Associates, Inc. | Geotechnical engineering | 10 |
| 11 | Mechta Geotechnica | Geotechnical engineering | 21 |
| 12 | Merit Engineering Inc. | Geotechnical engineering | 3 |
| 13 | MOS Grondmechanica BV | Geotechnical engineering | 6 |