SOLUTION

Before work began on-site, our team developed cultural and paleontological monitoring plans as well as the unexpected discovery plan to thoroughly guide the construction company and monitoring crews throughout the length of the project.

With detailed plans in hand, the archaeology of each site was modeled and boundaries set up around the project. Supporting surveys were conducted to add to the understanding of the land, stratigraphy and history and further prepare for what could be discovered during construction. Ultimately, a couple sites in the area turned up very little, as anticipated; however, one revealed more than expected.

Starting in February 2019, our project team went to work on the 140-acre Anticline greenfield site, a long-time wetland, in central Wyoming. While nothing was uncovered within the footprint of the substation — team members were keenly focused on the possibility of finding ancient burial sites — monitoring of the construction process continued for several more months. Additionally, they kept watch on surrounding sites where archaeological discoveries had been made.

The team also surveyed the geology of the 10-acre Jim Bridger expansion site and remained on-site during construction. As expected, nothing was found at this site, which is located in solid rock. Most of the team’s efforts centered on Aeolus, where the archaeological and paleontological potential was vast. Down the road from that particular site is an area called Como Bluffs, also known as dinosaur central.

In the middle of the Aeolus substation’s 120-acre footprint was a significant hill, which the team nicknamed “conglomerate hill” because of the of type of rock initially found on the surface. As it was carefully deconstructed in layers, the team made some interesting discoveries. The sedimentary rock revealed that this area was a shallow estuary near a river delta between 100 million years ago and 66 million years ago. More than 50 million years of tidal action had been preserved in the shale that makes up the area’s bedrock.

Within an eight-week timespan, the team identified significant fossils of marine life, including oysters, clams and echinoids. There was evidence of tiny fish, sponges, mantis shrimp and burrows as well as ammonites — ancestors of the modern-day mollusk that look like big snails with hard shells and octopus heads. The team also uncovered dinosaur coprolites (manure). In total, the team recovered evidence of 51 different types of species, making this the largest paleontological discovery by Burns & McDonnell to date.

While surveying the hill, the team also noticed orange stripes around the edge, the remains of cyclic volcanic eruptions, which seemed to take place every 1 million to 2 million years.

Roughly 145 million years ago, the region started out as a swamp, but as the Medicine Bow valley broke about 65 million years ago — because of the rising of the Rocky Mountains — it was tilted and rotated, then flooded again, which took the top off. This “hill” was tortured in its life, and the team could see all of that in its geology.

RESULTS

As with all discoveries, the team identified, cleaned, dated and recorded each fossil and finding at Aeolus, writing up an extensive paleontological report with a detailed historical timeline. This report was provided to the Bureau of Land Management, the on-site federal agency; PacifiCorp, the landowner and client; and the state geologist. The team consulted with the local tribe communities throughout the project and shared the report with them as well.

The entire team actively monitored each site during a nine-month time frame, a portion of which took place during the harsh winter Wyoming months. All work was successfully completed without delay or any safety issues. The archaeology team will return to Anticline in summer 2020 to monitor the installation of the substation’s permanent access road and will remain on call until all projects are completed.