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| Company | Location | County | Certifications | License # |
|---|---|---|---|---|
| Wallace S Lewis | Pawcatuck, CT | — | Installer | L1487 |
| Waste Away Septic Service | Exeter, RI | — | Septage Hauler | 788 |
| Wayne J Hawkins | Sterling, CT | — | Designer (Class I) | D1144 |
| Wayne J Hawkins | Sterling, CT | — | Installer | L1299 |
| Westerly Sanitation | Westerly, RI | — | Septage Hauler | 573 |
| Western Oil, Inc. | Lincoln, RI | — | Septage Hauler | 326 |
| William A Clarke | Charlestown, RI | — | Installer | L1357 |
| William A Coulter | Wood River Jct, RI | — | Installer | L1126 |
| William B McMahon | N.Harwich, MA | — | Installer | L1863 |
| William B Rose | Block Island, RI | — | Installer | L1406 |
| William Baldwin | Johnston, RI | — | Installer | L0598 |
| William Clarke A | Charlestown, RI | — | Designer (Class I) | D1110 |
| William D Dowdell | Charlestown, RI | — | Designer (Class III) | D3010 |
| William E Frederickson | North Scituate, RI | — | Installer | L1562 |
| William E Ronci | North Kingstown, RI | — | Installer | L1583 |
| William F Smith | Little Compton, RI | — | Designer (Class III) | D3025 |
| William F Smith | Little Compton, RI | — | Designer (Class IV Soil Evaluator) | D4034 |
| William G Silvia | Portsmouth, RI | — | Installer | L1409 |
| William H Howard | West Kingston, RI | — | Installer | L1971 |
| William J Rodenhiser | Holliston, MA | — | Installer | L1741 |
| William J Ross | East Greenwich, RI | — | Designer (Class I) | D1231 |
| William J Ross | East Greenwich, RI | — | Installer | L1632 |
| William J Vorra III | North Stonington, CT | — | Installer | L1957 |
| William J Wilbur | Warwick, RI | — | Installer | L0839 |
| William M Anderson | East Greenwich, RI | — | Designer (Class III) | D3001 |
| William P Napier | Portsmouth, RI | — | Designer (Class I) | D1230 |
| William P Napier | Portsmouth, RI | — | Installer | L1693 |
| William R Buckley, Jr. | Foxborough, MA | — | Designer (Class III) | D3109 |
| William S Gavitt | Westerly, RI | — | Installer | L1137 |
| William S Rice | Coventry, RI | — | Installer | L1631 |
| William Wright Jr. | West Greenwich, RI | — | Installer | L1051 |
| Wind River Environmental | Marlborough, MA | — | Septage Hauler | 827 |
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