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| Company | Location | County | Certifications | License # |
|---|---|---|---|---|
| O'connell & Lawrence Inc | Olney, MD | — | Inspector (BAT O&M)Inspector (Property Transfer)Installer (At-Grade)Installer (BAT)Installer (Sand Mound) | 00855 |
| Oak Hill Construction, LLC | Silver Spring, MD | — | Inspector (BAT O&M)Inspector (Property Transfer)Installer (At-Grade)Installer (BAT) | 00512 |
| Oakley Martin | Knoxville, MD | — | Inspector (BAT O&M)Inspector (Property Transfer)Installer (At-Grade) | 01126 |
| OC Home Care DBA Blue Crab Inspec | Joppa, MD | — | Inspector (BAT O&M)Installer (At-Grade)Installer (BAT)Installer (Sand Mound) | 01494 |
| OC HomeService Group LLC | Delmar, MD | — | Inspector (BAT O&M)Inspector (Property Transfer)Installer (BAT) | 02413 |
| Old Line Septic | Frederick, MD | — | 02070 | |
| Olden Excavating Inc | Keedysville, MD | — | Inspector (BAT O&M)Inspector (Property Transfer) | 00972 |
| Olingers Paving, LLC. | Littlestown, PA | — | Inspector (BAT O&M)Inspector (Property Transfer)Installer (At-Grade)Installer (BAT)Installer (Sand Mound) | 00223 |
| OnSite Construction, Inc. | Seaford, DE | — | Inspector (BAT O&M)Inspector (Property Transfer) | 01908 |
| Onsite Septic Inspection & Service LLC | Denton, MD | — | Inspector (Property Transfer)Installer (At-Grade)Installer (BAT)Installer (Sand Mound) | 00717 |
| Onsite, LLC | Union Bridge, MD | — | 00664 | |
| Osis, Llc | Denton, MD | — | Inspector (BAT O&M)Inspector (Property Transfer)Installer (At-Grade)Installer (BAT)Installer (Sand Mound) | 02516 |
| Outback Porta Jon Inc | Prince Frederick, MD | — | Inspector (Property Transfer)Installer (At-Grade)Installer (BAT)Installer (Sand Mound) | 02106 |
| Owen Excavation, LLC | Chestertown, MD | — | Inspector (BAT O&M)Inspector (Property Transfer)Installer (At-Grade)Installer (BAT)Installer (Sand Mound) | 00116 |
| Ox Construction | New Windsor, MD | — | Inspector (Property Transfer)Installer (At-Grade) | 01866 |
| Ozman Turf Management, LLC | Trappe, MD | — | Inspector (BAT O&M)Inspector (Property Transfer)Installer (At-Grade)Installer (Sand Mound) | 00954 |
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