| # | Company name | Role | # of projects |
|---|---|---|---|
| 41 | CDM Consult GmbH | Geotechnical engineering | 0 |
| 42 | CDM Grundbauinstitut Sommer GmbH | Geotechnical engineering | 0 |
| 43 | CDM Jungbauer GmbH | Geotechnical engineering | 0 |
| 44 | CGC, Inc. | Geotechnical engineering | 3 |
| 45 | CNA Consulting Engineers | Geotechnical engineering | 2 |
| 46 | Coastal Planning and Engineering, Inc. | Geotechnical engineering | 18 |
| 47 | Coastal Planning and Engineering, Inc. | Geotechnical engineering | 0 |
| 48 | Compétence Géotechnique | Geotechnical engineering | 1 |
| 49 | Consolidated Engineering Labs | Geotechnical engineering | 1 |
| 50 | Construction Engineering Consultants, Inc. | Geotechnical engineering | 1 |
| 51 | Consultancy Group Company | Geotechnical engineering | 1 |
| 52 | CY Geotech Inc. | Geotechnical engineering | 1 |
| 53 | Darviche Haddad Teknofor Piling & Shoring Company | Geotechnical engineering | 3 |
| 54 | Davies Geotechnical Inc. | Geotechnical engineering | 2 |
| 55 | Diaz•Yourman & Associates | Geotechnical engineering | 1 |
| 56 | Douglas Partners Pty Ltd | Geotechnical engineering | 1 |
| 57 | Dr. Vollenweider AG | Geotechnical engineering | 2 |
| 58 | Driggers Engineering Services, Inc. | Geotechnical engineering | 17 |
| 59 | Dyregrov Consultants | Geotechnical engineering | 10 |
| 60 | Enders & Dührkop | Geotechnical engineering | 3 |