| Business | Phone |
| Consolidated Engineering 1300 Pennsylvania Ave Nw, Washington 20004 | (202) 789-4286 |
| Bay International Envrnmntl 5505 Connecticut Ave Nw # 179, Washington 20015 | (202) 584-1311 |
| Geo-Centers Inc 1201 M St Se, Washington 20003 | (202) 544-7277 |
| Grace Terpstra & Assoc 1800 M St Nw # 300n, Washington 20036 | (202) 828-9487 |
| Green Shape 616 4th St Ne, Washington 20002 | (202) 544-1400 |
| Lti-Limno-Tech Inc 1705 Desales St Nw # 600, Washington 20036 | (202) 833-9140 |
| Potomac Research Group 1030 15th St Nw # 1028, Washington 20005 | (202) 216-0363 |