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Table 3.11-2. Previously Recorded Fossil Localities in the Vicinity of the Project in the Records of the DMNS
Geologic Unit
Name
Tensleep Sandstone
Map Unit Abbreviation
Pt
Common Fossils
Fusilinid foraminiferans
Amsden Formation IPMa Foraminifera, brachiopods, corals, bryozoans, mollusks, echinoderms, trilobites, and fragmentary fish skeletons, scales, and teeth
Madison Limestone Mm Abundant and diverse marine invertebrates including brachiopods, cephalopods, bivalves, gastropods, and echinoids
Sources: Stantec 2022, Jones and Gregory 2011. 3.11.1.3 Results of the Paleontological Survey
Age PFYC
Middle to late Pennsylvan ian to early Permian
Upper Mississippi an to lower Pennsylvan ia
Mississippi an 3
3
3
Records searches were conducted as part of the Paleontological Resources Survey to determine the presence of previously recorded fossil localities within and near the Project area. These searches accessed data from three institutional sources: UW (2021), UCM (2021), and DMNS (2021). In addition, records were searched using the public online PBDB (2021). According to the UCM, UW, and DMNS museum records searches, there are no previously recorded fossil localities directly within the Project area. The DMNS records eight fossil localities within the same Townships and geologic units as the Project area which produced plant remains, summarized in Table 3.11-2 (DMNS 2021). The online PBDB records over 1,000 fossil occurrences within the same geologic units as the Project area elsewhere in Carbon County, Wyoming preserving plants, invertebrates, mammals, dinosaurs, squamate reptiles, and fish and provides full taxonomic lists of each locality (Stantec 2022).
Table 3.11-2. Previously Recorded Fossil Localities in the Vicinity of the Project in the Records of the DMNS
Locality Number Fossils Age Formation
2602 Plantae undet. Cretaceous Ferris
2648 Plantae undet. Paleocene
2649 Plantae undet. Paleocene Ferris
Ferris
2650 Plantae undet. Paleocene
2651 Plantae undet. Paleocene
2656 Plantae undet. Paleocene
2657 Plantae undet. Paleocene Ferris
Ferris
Ferris
Ferris
17584 Plantae undet. Paleocene Hanna
Source: Stantec 2022.
The paleontological field survey included a pedestrian and visual examination of the Project area located on BLM and private lands underlain by PFYC 3 to PFYC 5 geologic units. Topography of the survey area consists of low-to-moderate relief hills with minor drainages, steep ridges, and rocky slopes. Flat areas are characterized by grassy vegetation, prairie, and agricultural land. Sagebrush and desert grasses cover a large portion of the survey area. There are some pre-disturbances from transmission lines, gravel and dirt roads, fences, cattle tracks, and animal burrows. Bedrock from all mapped geologic units except the Chugwater Group and Wind River Formation was observed within the survey areas, and 15 new non-significant fossil occurrences were documented. No significant fossil localities were found or collected. The survey results are provided in detail in the privileged Paleontological Survey Report (Stantec 2022).
Geology
Bedrock exposures of almost all the mapped formations were observed in isolated areas within the survey areas, some of which are heavily weathered at the surface or only observed because they were exhumed by animal burrows. The Chugwater Group and Wind River Formation were not observed in any of the survey areas. Additionally, mapped geologic contacts were found to be inaccurate during the field survey, and as a result, one formation that was not mapped within the Project area was observed, the Tensleep Formation (Stantec 2022).
Paleontology
Fifteen non-significant fossil occurrences were documented in the Project area. These consist of belemnites from the Morrison and Sundance formations (undivided), bivalves from the Niobrara, Medicine Bow, and Morrison and Sundance (undivided) formations, oysters from the Niobrara Formation and found as float, crinoids from the Steele Shale, gastropods from the Medicine Bow and Morrison and Sundance (undivided) formations, plants from the Hanna and Morrison and Sundance (undivided) formations, brachiopods from the Amsden and Morrison and Sundance (undivided) formations, and vertebrates as float and from the Morrison and Sundance formations (undivided) (Stantec 2022).
Because all these fossil occurrences are non-significant, the areas do not require further treatment prior to construction (Stantec 2022).
3.11.2 Environmental Effects on Paleontological Resources
This section presents information available regarding potential effects of the proposed Project, including a discussion of fluctuations in Seminoe Reservoir water levels associated with Project pumping and generating operations.
The areas surveyed for paleontological resources contain geologic units with moderate (PFYC 3) to very high (PFYC 5) paleontological potential, as listed in Table 3.11-1. While these units are not exposed at the surface in all areas where they are mapped, in most cases they lie at very shallow depths below surficial sediments. There are no previously recorded fossil localities within the Project area. However, numerous previously recorded fossil localities occur in the same Townships within the same formations as those in the
Project area, and newly documented fossil localities within the Project area show that there is a potential for paleontological resources to be encountered during construction activities.
The paleontological resource potential for each geologic formation classified as PFYC 3, 4, and 5 is based on a review of published literature and geologic maps:
• Madison Limestone. The Madison Limestone generally consists of thick and extensive sequences of limestone and dolomite, with evaporites, some shale, and chert in some areas. The Madison Limestone is underlain by several formations of limestone, dolomite, and sandstone aging from Cambrian to Early Mississippian. The
Madison Limestone has abundant and diverse marine invertebrates including brachiopods, cephalopods, bivalves, gastropods, and echinoids, mainly from the
Lodgepole Formation (French 1984). The Madison Limestone in Wyoming produces locally abundant and diverse marine invertebrates and the BLM considers the unit to have moderate paleontological potential (PFYC 3) (Stantec 2022). • Amsden Formation. Fossils documented within the Amsden Formation are sparse but include a diverse invertebrate fauna of sponges, coral, bivalves, gastropods, bryozoans, echinoderms, trilobites, and brachiopods as well as much less abundant marine and terrestrial plants (Burk 1954, Perry and Gutschick 1959, Gordon 1975,
Gordon and Pojeta 1975, Gordon and Yochelson 1975). Most fossils are found in limestone and dolostone beds. Due to the diversity and abundance of invertebrates, and sparse vertebrate remains, the BLM classifies the Amsden Formation as having moderate paleontological potential (PFYC 3) (Stantec 2022). • Tensleep Sandstone. The Tensleep Sandstone was originally thought to be unfossiliferous. However, the discovery of fusilinid foraminiferans changed that perception (Branson, 1939). Additionally, the fusulinids Schwagerina and Triticites were found on the eastern wing of the southern Big Horn Mountains of Johnson
County, Wyoming (Verville, 1957). About 300 to 400 feet below the top of Tensleep,
Desmoinesian-age fusulinids have been discovered (Verville, 1957). The Tensleep
Sandstone is classified by the BLM as having moderate paleontological potential (PFYC 3) (Stantec2022). • Goose Egg Formation. Within the Goose Egg Formation, there are only scarce invertebrate and vertebrate fossils reported. Invertebrate taxa are limited to Trigonia clams (Newell and Boyd 1975). Vertebrate occurrences include conodonts and remnants of fish (Pearson 1971). These fossils have all been found within Natrona
County, Wyoming, with no other localities in other counties having been reported to date. The BLM has designated the Goose Egg Formation as having moderate paleontological potential (PFYC 3) (Stantec 2022). • Morrison and Sundance formations (undivided). The Morrison Formation is famous for being one of the world’s richest sources of dinosaur fossils. Fossils of the Sundance
Formation are diverse and locally quite abundant. The BLM classifies the Morrison and
Sundance formations (undivided) as having very high paleontological potential (PFYC 5) in the region (Stantec 2022). • Steele Shale. The Steele Shale consists of the Sussex sandstone beds, Shannon sandstone beds, and Fishtooth sandstone. Fossils known from the Steele Shale include trace fossils, foraminifera, brachiopods, bryozoa, bivalves, gastropods, ammonites, fish, shark, and reptiles (Gill and Burkholder 1979). The BLM classifies the
Steele Shale Formation as having moderate paleontological potential (PFYC 3) (Stantec 2022). • Mesaverde Group. The Mesaverde Group of Wyoming is known to contain fossils from multiple families of marine and non-marine Late Cretaceous faunas, including
Mammalia and Dinosauria, as well as some vertebrate microfossil assemblages (Lucas and Sullivan 2006). Some of the more notable fossil localities include sites in the Wind River and Bighorn basins in Wyoming, where multiple specimens were recorded. The BLM classifies the Mesaverde Group as having moderate paleontological potential in Wyoming (PFYC 3) (Stantec2022). • Medicine Bow Formation. This formation consists of alternating bands of yellow gray to gray carbonaceous shale and gray to brown sandstones showing cross-bedding, ripple marks, and other features of irregular deposition. Fossils known from the
Medicine Bow Formation include trace fossils, foraminifera, brachiopods, bivalves, gastropods, ammonites, fish scales and other fish remains, reptiles, and poorly preserved dinosaur remains (Gill et al. 1970). The Medicine Bow Formation is classified by the BLM as having moderate paleontological potential (PFYC 3) (Stantec 2022). • Ferris Formation. Fossils found in the Ferris Formation include plant microfossils (Gill et al. 1970) and macrofossils. There is a wide variety of non-mammalian vertebrates, including: fish, rays and guitarfish, amphibians, turtles, lizards, choristoderes, crocodilians, birds, and theropod, hadrosaurid, ceratopsian, ankylosaurian, and pachycephalosaurid dinosaurs (Lillegraven and Eberle 1999). The BLM classifies the
Ferris Formation as having very high fossil potential (PFYC 5) (Stantec2022). • Hanna Formation. The Hanna consists of alternating beds of carbonaceous shale, sandstones that are massive, thin-bedded, and commonly cross-bedded, conglomerates and conglomeratic sandstones, and numerous coal beds that were extensively mined (Bowen 1918). Shales are dark-gray and yellowish, while sandstones are white, gray, and brown. Fossils found in the Hanna include plants, invertebrates, and vertebrates. The BLM classifies the Hanna Formation as having very high fossil potential (PFYC 5) (Stantec 2022). • Wind River Formation. The exposures of the Wind River Formation have produced an abundance of highly productive fossil localities that have resulted in one of the most scientifically significant early Eocene-age vertebrate fossil assemblages known. The
BLM has designated this formation as having very high paleontological potential (PFYC 5) due to the large number of scientifically significant vertebrate fossils collected from the Wind River Formation over 125 years, along with the fact that these finds have resulted in numerous publications and museum collections (Stantec 2022). • Niobrara Formation. The Niobrara Formation was deposited mostly in near-shore, marine settings during the second late Cretaceous transgressive-regressive cycle. It is a thick and widely distributed unit that includes two members: Fort Hays Limestone and Smoky Hill Chalk Member. Although fossil invertebrates are locally abundant, the
Niobrara Formation contains less abundant fossil vertebrates throughout most of its distribution, and therefore the BLM classifies the unit as having high paleontological potential (PFYC 4) (Stantec 2022). • Cloverly Formation. The lower Cretaceous Cloverly Formation overlies the Morrison
Formation and underlies the Sykes Mountain Formation. Fossils have been collected
from the Cloverly Formation within the Bighorn Basin for over 100 years. The BLM classifies the Cloverly Formation as having very high paleontological potential (PFYC 5) (Stantec 2022). • Thermopolis Shale. The late Early Cretaceous (Albian) Thermopolis Formation, also referred to as the Thermopolis Shale, is named after the town of Thermopolis, in Hot
Springs County, Wyoming, and has a reference section in Gallatin County, Montana (Lupton 1916, Roberts 1972). It is up to 500 feet thick within the Bighorn Basin and is exposed only in Wyoming and Montana. The Thermopolis Shale contains marine invertebrates and microfossils, and less common vertebrate fossils. The BLM classifies the Thermopolis Shale as having high paleontological potential (PFYC 4) (Stantec 2022). • Mowry Shale. The Early to Late Cretaceous (Albian to Cenomanian) Mowry
Formation, also referred to as the Mowry Shale, was named for exposures along
Mowrie Creek northwest of Buffalo, Wyoming (Darton 1904). The Mowry Shale contains abundant marine invertebrate and trace fossils throughout and less abundant marine vertebrate fossils, as well as rare and poorly preserved plants. Invertebrates include ammonites such as Metengonoceras sp. and inoceramid bivalves (Cobban and Kennedy 1989). The BLM classifies the Mowry Shale as having moderate paleontological potential (PFYC 3) (Stantec 2022). • Frontier Formation. The Frontier Formation is divided into several units, in ascending order: basal marine, fluvial-deltaic, progradational series, and upper marine sandstone (Tonnsen 1980). Near its type locality, the formation is 2,000 feet thick (Cobban and
Reeside 1952). Its dominant lithology consists of light gray or medium gray, fine- to coarse-grained and conglomeratic sandstone; clayey or sandy light gray to dark gray siltstone; silty and soft, dark gray to brownish gray shale; and yellowish gray or greenish gray bentonite. A few scattered coal beds are also present (Merewether et al. 1975). Although marine mollusks are locally common in the Frontier Formation, scientifically significant vertebrate fossils are rare, therefore the BLM classifies the
Frontier Formation as having moderate paleontological potential (PFYC 3) (Stantec 2022). • Chugwater Group. The Triassic Chugwater Group was originally named as the
Chugwater Formation from Chugwater Creek near Iron Mountain in Platte County, WY (Darton 1904). Fossils of the Chugwater Group (which is equivalent to the Dinwoody,
Thanes, Spearfish, Jelm, Ankareh, Woodside, Chinle, and Dolores formations, in part, and the Glen Canyon and Dockum groups, in part) are known primarily from the vicinity of the Wind River Basin in Wyoming. Because sparse but scientifically important vertebrate fossils have been found in the group and new discoveries in the unit would be scientifically important, the BLM classifies the Chugwater Group as having moderate paleontological potential (PFYC 3) (Stantec 2022).
Because the finds of the analysis of existing data and the 2021 and 2022 field survey indicated that there is a potential for paleontological resources to be encountered during construction activities, Black Canyon will coordinate with BLM to develop a plan to mitigate adverse impacts to significant paleontological resources (as defined in BLM IM-2009-11), during construction.
The Project is designed to pump up to 10,800 ac-ft over an average of 17.05-hour period from Seminoe Reservoir to the Project’s upper reservoir and then generate electricity when returning the water to Seminoe Reservoir over a 9.7-hour period. The full pump-generating cycle may occur as frequently as daily. The effect on Seminoe Reservoir water level elevations and surface area of removing and returning 10,800 ac-ft will vary depending upon Seminoe Reservoir water level elevation at the start of pumping. Seminoe Reservoir has a normal operating range of 6,290 feet to 6,357 feet, a 67-foot range in surface elevations. Typically, Seminoe Reservoir does not fluctuate daily, but rather seasonally. However, wind wave action occurs, creating dynamic intra-day shoreline conditions across Seminoe Reservoir’s entire operating range.
3.11.3 Cumulative Environmental Effects Related to Paleontological Resources
As noted in Table 3.2-1, the geographic scope for paleontological resources is within 200 feet of the Footprint of Potential Disturbance since the impact area for direct effects (physical) includes areas subject to ground disturbance and outside of the disturbance area. As detailed in Table 3.2-2, there are two projects that occur within the geographic scope for geologic and soil resources: 1) Gateway West Transmission Line Project, and 2) Gateway South Transmission Line Project. These projects tie into the existing Aeolus Substation, which represents less than 7 percent (approximately 462 acres) of the Project’s Footprint of Potential Disturbance and the only physical proximity between the Project and others within the geographic scope for potential effects on paleontological resources.
Issues Identified for Analysis
Paleontological resources can be affected by disturbance or destruction of buried, in-situ fossils as a result of ground-disturbing activities including access road creation, leveling of transmission tower sites, trenching, and earth moving work. Impacts to paleontological resources could also include increased potential for vandalism or unauthorized collection of fossils due to increased public access into previously difficult to access areas. Potential cumulative impacts on paleontological resources include damage or loss of scientifically important fossil resources though physical impact, erosion of fossil from exposed bedrock, and unauthorized collection or destruction of fossils by those accessing the analysis area or adjacent lands.
Black Canyon will minimize disturbance to paleontological resources and will work with the BLM to develop a plan to protect significant paleontological resources within the Project area. Based on the findings of the analysis of existing data and field survey reported herein, the project proponent is committed to consultations with the BLM in order to develop a plan to mitigate adverse impacts to significant paleontological resources (as defined in BLM IM-2009-11), during construction.
Results
The impacts from construction of the Project would contribute cumulatively to the impacts of other past projects (development of Seminoe Dam and Seminoe State Park) and future
projects. The Gateway West Transmission Line Project has completed construction (within the geographic scope) and Gateway South Transmission Line Project is undergoing construction and is expected to be completed prior to Project construction. However, the application of design features of the proposed Project, including preconstruction surveys for paleontological resources, would be anticipated to minimize the incremental effects. The implementation of future projects could contribute to cumulative effects on paleontological resources if appropriate mitigation is not applied.
3.11.4.1 Agency Consultation
The NOI and PAD for the proposed Project were filed with the FERC on April 20, 2020. Comments were received from several agencies including BLM and WGFD, and individual stakeholders. Black Canyon held a virtual joint public-agency meeting on July 21, 2020, and has continued consultation with stakeholders since that time. Black Canyon distributed its proposed resource study plans for the Project on August 3, 2020, and March 23, 2021. Black Canyon distributed the DLA on June 6, 2022. Responses to stakeholder comments and Black Canyon’s Record of Consultation are provided in Appendix A. BLM provided comments on paleontological resources in their comments on the DLA. Responses to comments on the DLA are provided in Appendix L.
3.11.4.2 Applicant Recommendations
As described in Table 2.1-5, the following PM&Es are applicable to paleontological resources:
• Paleontological Monitoring: Black Canyon proposes to develop and implement a plan to monitor construction and if necessary, mitigate adverse impacts to significant paleontological resources (as defined in BLM IM-2009-11) during construction.
3.12 Aesthetic Resources
The BLM is responsible for managing public lands for multiple use and ensuring scenic values of public lands are considered before authorizing uses that may have negative visual impacts. The BLM uses the Visual Resource Management (VRM) system to inventory scenic values through different categories to establish management objectives. The VRM system is a tool for the BLM to objectively measure the scenic value of the visual resources in an area (BLM undated-c).
The BLM designates VRM classes for all areas of BLM-administered lands to manage public lands in a manner which will protect the quality of the scenic and visual value of the land. The VRM classes are based on an inventory of three key elements: 1) scenic quality, 2) sensitivity level, and 3) distance zones (BLM 1984). There are four objectives for VRM classes (Classes I through IV), with Class I being the most conservative of the visual resources (BLM 1986) as shown in Table 3.12-1.
