| | Acc. No. | Year | Location | County | Observers |
| 1906-001 | 1906 |
Barr Lake State Park
| Adams | L. Hersey |
| 43-93-1 | 1993 |
Chatfield State Park
| Douglas | Urling & Hugh Kingery, J B Hayes, Joe TenBrink, Larry Norris, Mark Janos |
| 2006-006 | 2006 |
Chico Basin Ranch
| El Paso | Brandon Percival, Bill Maynard, Doug Faulkner, Andrew Spencer, Peter Gent, Cole Wild |
| 2006-018 | 2006 |
Denver
| Denver | Andrew Spencer, Cole Wild, Larry Semo |