| Business | Phone |
| Phoenix Land Design Inc 14412 Old Mill Rd # 201, Upper Marlboro 20772 | (301) 627-5581 |
| Rda Engineering Co 14603 Main St, Upper Marlboro 20772 | (301) 952-8200 |
| Stehle Engineering Corp 14400 Old Mill Rd # 101, Upper Marlboro 20772 | (301) 627-6700 |
| Civ Tech Designs Inc 6413 Crain Hwy, Upper Marlboro 20772 | (301) 780-7373 |