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i Table of Contents List of Tables.................................................................................................................................. ii List of Figures................................................................................................................................ iii 1.0 Introduction.......................................................................................................................... 1 1.1 Study Area........................................................................................................................ 1 2.0 Methods................................................................................................................................ 5 2.1 Habitat and Water Quality................................................................................................ 5 2.2 Fishes................................................................................................................................ 5 2.3 Benthic Macroinvertebrates............................................................................................. 7 3.0 Results.................................................................................................................................. 9 3.1 Sampling Conditions........................................................................................................ 9 3.2 Habitat.............................................................................................................................. 9 3.2.1 Hams Fork 1 (HF 1).................................................................................................. 9 3.2.2 Hams Fork 2 (HF 2)................................................................................................ 10 3.2.3 Hams Fork 3 (HF 3)................................................................................................ 10 3.2.4 North Fork Little Muddy Creek 1 (NFLM 1)......................................................... 10 3.2.5 North Fork Little Muddy Creek 2 (NFLM 2)......................................................... 10 3.2.6 North Fork Little Muddy Creek 3 (NFLM 3)......................................................... 11 3.3 Water Quality................................................................................................................. 11 3.4 Fishes.............................................................................................................................. 13 3.4.1 Hams Fork............................................................................................................... 13 3.4.2 North Fork Little Muddy Creek.............................................................................. 13 3.5 Benthic Macroinvertebrates........................................................................................... 19 3.5.1 Hams Fork............................................................................................................... 19 3.5.2 North Fork Little Muddy Creek.............................................................................. 25 4.0 Discussion and Conclusions.............................................................................................. 27 5.0 References.......................................................................................................................... 31 Appendix A.

Photos.................................................................................................................. 33 Appendix B.

Length-frequency Histograms............................................................................. 54 TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

ii List of Tables Table 1. Habitat, substrate, and cover codes used to describe habitat conditions at each segment.

........................................................................................................................................ 6 Table 2. Metrics used to calculate the Wyoming Stream Integrity Index...................................... 8 Table 3. Water quality measurements at three survey segments on Hams Fork (HF) and three survey segments in the North Fork Little Muddy Creek drainage (NFLM) during fall 2022, spring 2023, and summer 2023.......................................................................... 12 Table 4. Abundance (#) and percent relative abundance (%) of fishes collected from three segments on the Hams Fork (HF) via electrofishing and minnow trapping in 2022-2023.............................................................................................................................. 14 Table 5. Abundance (#) and catch-per-unit-effort (CPUE; fish/min) of fishes collected by electrofishing from three segments on the Hams Fork (HF) in 2022-2023................. 15 Table 6. Abundance (#) and catch-per-unit-effort (CPUE; fish/trap-night) of fishes collected in minnow traps from three segments on the Hams Fork (HF) in 2022-2023................. 15 Table 7. Number (#) and percent relative abundance (%) of fishes captured from three survey segments on Hams Fork during fall (October 2022), spring (June 2023), and summer (August 2023)............................................................................................................... 16 Table 8. Species richness, total fish abundance, electrofishing CPUE (fish/min), and minnow trap CPUE (fish/trap-night) by season at Hams Fork................................................... 17 Table 9. Abundance (#) and percent relative abundance (%) of fishes collected from three segments on the North Fork Little Muddy Creek drainage (NFLM) via electrofishing and minnow trapping in 2022-2023............................................................................. 17 Table 10. Abundance (#) and catch-per-unit-effort (CPUE; fish/minute) of fishes captured by electrofishing at three segments on the North Fork Little Muddy Creek drainage (NFLM) in 2022-2023.................................................................................................. 20 Table 11. Abundance (#) and catch-per-unit-effort (CPUE; fish/trap-night) of fishes captured in minnow traps at three segments on the North Fork Little Muddy Creek drainage (NFLM) in 2022-2023.................................................................................................. 20 Table 12. Number (#) and percent relative abundance (%) of fishes captured from North Fork Little Muddy Creek during fall (October 2022), spring (June 2023), and summer (August 2023)............................................................................................................... 21 Table 13. Species richness, total fish abundance, electrofishing CPUE (fish/min), and minnow trap CPUE (fish/trap-night) by season at North Fork Little Muddy Creek.................. 21 Table 14. Number of benthic macroinvertebrates by lowest taxonomic unit (LTU) collected from each survey segment in Hams Fork during fall 2022, spring 2023, and summer 2023 sampling events........................................................................................................... 22 Table 15. Metric values and scores for calculating the Wyoming Stream Integrity Index (Wyoming Basin) at three segments in the Hams Fork during fall 2022, spring 2023, and summer 2023 sampling events. Composite WSII scores for each segment/season are in bold text.............................................................................................................. 24 Table 16. Number of benthic macroinvertebrates by lowest taxonomic unit (LTU) collected from each survey segment in the North Fork Little Muddy Creek drainage during fall 2022, spring 2023, and summer 2023 sampling events......................................................... 26 TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

iii Table 17. Metric values and scores for calculating the Wyoming Stream Integrity Index (Wyoming Basin) at three segments in the North Fork Little Muddy Creek drainage during fall 2022, spring 2023, and summer 2023 sampling events. Composite WSII scores for each segment/season are in bold text........................................................... 28 List of Figures Figure 1. Map of aquatic survey segments in relation to the Kemmerer Unit 1 site and associated infrastructure in Lincoln County, Wyoming.................................................................. 2 Figure 2. Map of aquatic survey segments on Hams Fork in relation to the existing dam and intake structure............................................................................................................... 3 Figure 3. Map of aquatic survey segments in the North Fork Little Muddy Creek drainage in relation to the Kemmerer Unit 1 site and associated infrastructure............................... 4 Figure 4. Length-frequency histograms for Brown Trout (top), Mountain Whitefish (middle),

and White Sucker (bottom) captured from Hams Fork during all sampling events..... 18 Figure 5. Composite Wyoming Stream Integrity Index scores (Wyoming basin; mean +/- 95%

confidence intervals) and associated aquatic life use status thresholds at three segments on Hams Fork during fall 2022, spring 2023, and summer 2023 sampling events...... 25 Figure 6. Composite Wyoming Stream Integrity Index scores (Wyoming basin; mean +/- 95%

confidence intervals) and associated aquatic life use status thresholds at three segments in the North Fork Little Muddy Creek drainage during fall 2022, spring 2023, and summer 2023 sampling events..................................................................................... 29 TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

1 1.0 Introduction TerraPower plans to build a 345-megawatt sodium-cooled Natrium' reactor and energy storage system (the Project) at a site located in southwest Wyoming. Tetra Tech is preparing an Environmental Report as part of the Construction Permit Application to the Nuclear Regulatory Commission (NRC). A description of the principal aquatic ecological features of the site and vicinity is needed in the Environmental Report to evaluate potential impacts to the aquatic environment that may result from Project construction or operation. In July of 2022, Tetra Tech contracted BIO-WEST, Inc. (BIO-WEST) to conduct surveys of fish and benthic macroinvertebrates in a total of six segments within two stream systems (North Fork Little Muddy Creek and Hams Fork) that could be impacted. Due to seasonal variation in aquatic communities and imperfect capture efficiencies, multiple sampling events are typically necessary to detect rare species and appropriately characterize aquatic communities. Therefore, surveys were replicated across fall (October 2022), spring (June 2023), and summer (August 2023) seasons. Winter sampling was not conducted due to ice coverage on both streams and potentially hazardous conditions for biologists. This comprehensive final report delineates the segments selected, describes the habitat conditions encountered, details the sampling methods employed, and summarizes results of all surveys in context with existing information.

1.1 Study Area The proposed Kemmerer Unit 1 generating facility would be located between U.S. Highway 189 and North Fork Little Muddy Creek approximately 3 miles south of the city limit of Kemmerer, Lincoln County, Wyoming, and a short distance southeast of the existing coal-fired Naughton Power Plant (Figure 1). The Project would include two approximately 6-mile-long transmission lines and a water supply pipeline that would connect the new Kemmerer Unit 1 facility to the existing Naughton Plant infrastructure. Since Project construction and operation activities could affect North Fork Little Muddy Creek, baseline information on the aquatic communities of the creek was collected for inclusion in the Environmental Report. Additionally, to take advantage of existing infrastructure, the Project will use the Naughton Power Plants existing Cooling Water Intake Structure (CWIS) on Hams Fork approximately seven miles north of the power plant (Figure 1). Therefore, baseline information on the aquatic communities of Hams Fork in the vicinity of the CWIS was also collected. Both Hams Fork and North Fork Little Muddy Creek are tributaries of Blacks Fork within the Green River subbasin of the Colorado River drainage.

Six survey segments within the two stream systems were chosen for seasonal sampling based on discussions with Tetra Tech, locations of project infrastructure, aquatic habitat conditions, and available access points. Each segment was a minimum of 100 meters in length, with exact segment locations selected during an August 2022 reconnaissance trip conducted by BIO-WEST biologists. They included three survey segments on the Hams Fork - one segment at the existing dam/intake structure and two segments upstream (Figure 2). Three survey segments were also selected within the North Fork Little Muddy Creek drainage - one upstream of the Kemmerer Unit 1 site near the planned water pipeline and transmission lines on an unnamed tributary that carries effluent from the Naughton Power Plant, one on North Fork Little Muddy Creek near the mid-point of the Kemmerer Unit 1 site, and one downstream of the site (Figure 3). Brief TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

2 Figure 1. Map of aquatic survey segments in relation to the Kemmerer Unit 1 site and associated infrastructure in Lincoln County, Wyoming.

3 Figure 2. Map of aquatic survey segments on Hams Fork in relation to the existing dam and intake structure.

4 Figure 3. Map of aquatic survey segments in the North Fork Little Muddy Creek drainage in relation to the Kemmerer Unit 1 site and associated infrastructure.

5 descriptions of the habitat conditions observed at each segment are provided in Section 3.2, with representative photos of each segment taken during the August reconnaissance trip provided in Appendix A.

2.0 Methods 2.1 Habitat and Water Quality Habitat conditions were described by visually estimating the percent cover of mesohabitat types (e.g., riffle, run, pool, backwater) within each segment using predefined categories similar to those proposed by Hawkins et al. (1993) (Table 1). Additionally, areal coverage of individual fish habitat parameters such as undercut bank, submerged aquatic vegetation, woody debris, and overhanging/inundated vegetation was visually estimated as percent coverage of the total wetted area/bank area using similar categories. Water depth (feet) and mean current velocity (feet/second) were quantified at a minimum of six representative points within each segment using a flowmeter and incremental wading rod. At each of these points, dominant and subdominant substrates were also visually classified based on definitions in Table 1. Lastly, standard water quality parameters (water temperature [°C], dissolved oxygen [mg/L and percent saturation], pH, and specific conductance [µS/cm]) were measured at each segment using a handheld water quality sonde. Habitat data collected at each segment are summarized in Section 3.2, and water quality data are summarized in Section 3.3.

2.2 Fishes Depending on stream size and access conditions at time of sampling, electrofishing was conducted with one of two electrofishing units. Where feasible, electrofishing was conducted with a Smith-Root 5.0 GPP boat/barge-electrofisher mounted on a 15 ft aluminum jon boat. This unit allowed for boat-electrofishing in deeper areas, and barge-electrofishing in wadeable areas.

In situations where boat access was infeasible and flow conditions were unsafe for boating (Hams Fork segments in spring 2023), or stream size was too small for the boat (North Fork Little Muddy Creek), a backpack electrofisher (Smith Root LR-24) was used. Electrofishing was not conducted at Hams Fork Segment 3 (HF 3) in spring 2023 as flow conditions were unsafe for boat operation and this segment was too deep for backpack electrofishing. In all other cases, a minimum of 900 seconds/15 minutes of pulsed DC electrofishing pedal time (when electric current is actually applied) was conducted at each segment. Survey crews consisting of two netters started at the downstream end of the segment and moved upstream to minimize the influence of surveyor-generated turbidity on sampling efficiency. Lastly, to help ensure capture of all species present, three Gee-style minnow traps were baited with dry dog food, deployed overnight at each segment, and retrieved the following day. All fishes collected were identified to species and enumerated by gear type, except some young-of-year suckers (Catostomus sp. <

25 mm total length) were identified only to genus because their small size limited the ability to identify them to species in the field without harming them. No fish were killed during the study.

Up to 50 individuals of each species were measured (total length, inches) and weighed (grams),

with voucher photographs taken of each species. Following data collection, all fishes were released near the point of capture. Data were analyzed to provide raw abundance, percent relative abundance, and catch-per-unit-effort (CPUE) by species and survey segment for electrofishing TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

6 (fish/minute) and minnow trap sampling (fish/trap-night). Species richness was also recorded for each segment overall and by sampling method. Length frequency histograms were generated for species with sufficient sample size. Results of all sampling events are provided in Section 3.4.

Table 1. Habitat, substrate, and cover codes used to describe habitat conditions at each segment.

Code Habitat / Substrate /

Cover Type Definition Habitat BW Backwater An off channel but connected body of water in an abandoned secondary mouth, behind a bar, or in a bank indention, with no perceptible flow, and typically a sand or silt substrate.

PO Pool Area within a channel where flow is not visually perceptible or barely so, deeper depths, and typically a surface substrate of silt or sand.

ED Eddy Similar to pool except water flow is evident (but slow) and typically circular or opposite that of the channel.

SH Shoal Generally shallow areas with laminar flow and slow to moderate velocity over any substrate.

RN Run Moderate or rapid velocity water with little or no surface disturbance, moderate depths.

RF Riffle Area within a channel where gradient is moderate to high, depth is shallow, velocity is moderate to rapid, and water surface is disturbed by turbulence.

SW Slackwater Low-velocity habitats usually along inside margin of river bends or shoreline indentations, or immediately downstream of debris piles, bars, or other instream features.

IP Isolated Pool Small body of water in a depression, old backwater, or side channel that is not connected to the channel due to receding flows.

Substrate SI Silt Fine sediments with no visual grain size, tactilely smooth.

SA Sand Visually coarse fine sediments, tactilely gritty.

FG Fine Gravel

<2.5 cm CG Coarse Gravel 2.5 - 7.6 cm SC Small Cobble 7.6 - 15.2 cm LC Large Cobble 15.2 - 25.0 cm BLD Boulder

>25.0 cm BR Bedrock Rock with no definable grain size.

Cover IV Inundated Vegetation Inundated emergent or terrestrial vegetation near stream edges, islands, or point bars.

RT Roots Inundated roots of riparian trees along stream edges, islands, or point bars.

SWD Small Woody Debris Small diameter (twig-like) woody debris.

LWD Large Woody Debris Larger diameter woody debris such as limbs, trunks, and large root wads.

OV Overhanging Vegetation Emergent or terrestrial vegetation hanging over the stream surface along stream edges, islands, or point bars.

BRS Bedrock Shelves Sharp transitions or undercuts in bedrock.

7 2.3 Benthic Macroinvertebrates Benthic macroinvertebrates were collected with a D-frame kick net (500-micron mesh) in wadeable areas and supplemented with additional sampling using a Ponar grab sampler in non-wadeable habitats (>3.8 ft deep). Kick net sampling was conducted in swift-flowing riffle habitats (where present) and was also supplemented with jab-style sampling in undercut banks, backwaters, and littoral areas, generally following methods described in Barbour et al. (1999).

Due to non-wadeable depths at HF 3, a petite Ponar grab sampler was used to collect benthic organisms from mid-channel areas at this survey segment. Three grabs were conducted, and all associated sediment and detritus were combined into a sieve bucket to rinse out fine sediments.

Ponar collections at HF 3 were supplemented with jab-style sampling using the D-frame kick net along the stream margins and littoral zones. All macroinvertebrates and associated detritus were preserved in 95% ethanol in clearly labeled containers for later laboratory analysis.

In the laboratory, an experienced taxonomist sorted and identified all organisms within the sample, or until a minimum of approximately 500 organisms was reached, identifying benthic invertebrates to the lowest practical taxonomic level.

Assessments of ecological condition based on macroinvertebrate communities were conducted at each segment and season using the Wyoming Stream Integrity Index (WSII) developed by the Wyoming Department of Environmental Quality (Hargett and ZumBerge 2006). This index incorporates multiple metrics that were developed for specific bioregions in the state, integrating compositional, structural, and functional components of macroinvertebrate assemblages to quantify the status of aquatic life use. For each survey segment per season, WSII was calculated using ten metrics and scoring criteria provided for the Wyoming Basin (Table 2). Scoring was based on taxa richness (Ephemeroptera, Trichoptera, and Plecoptera taxa richness), assemblage composition (percent non-insect, Plecoptera, and Trichoptera), functional feeding groups (percent collector-gatherer and scraper), tolerance (Hilsenhoff Biotic Index [HBI]; Hilsenhoff 1987), and life history (semivoltine taxa richness) metrics (Hargett and ZumBerge 2006).

Functional feeding groups and tolerance values (Northwest designations) used to calculate HBI were assigned based on Barbour et al. (1999). Taxa were classified as semivoltine (i.e., > 1 year to complete life cycle) based on unpublished data provided by R.W. Wisseman (2001).

Each metric quantified was standardized through integration as described in Hargett and ZumBerge (2006), resulting in unitless scores that ranged from 0 to 100. Segment-level WSII scores were quantified by calculating means of the ten metrics assessed, which were then assigned a criterion for the status of aquatic life use based on numeric thresholds assigned for the Wyoming Basin. Status of aquatic life use criteria included full support (> 51.9%), indeterminate (34.6-51.9%), and partial/non-support (< 34.6%) (Hargett and ZumBerge 2006). Lastly, 95%

confidence intervals were also calculated based on scores from all metrics for each segment/season to account for uncertainty in WSII scores and status of aquatic life use assignments. Values and standardized scores for each metric along with overall WSII aquatic life use assignments are summarized in Section 3.5.

8 Table 2. Metrics used to calculate the Wyoming Stream Integrity Index.

Metric Definition Predicted Response to Increased Perturbation No. Ephemeroptera Taxa Number of taxa in the insect order Ephemeroptera (mayflies)

Decrease No. Trichoptera Taxa Number of taxa in the insect order Trichoptera (caddisflies)

Decrease No. Plecoptera Taxa Number of taxa in the insect order Plecoptera (stoneflies)

Decrease

% Non-Insects Percent of individuals which are not insects (e.g., amphipods, oligochaetes, snails)

Increase

% Plecoptera Percent of individuals that are Plecoptera (stoneflies)

Decrease

% within Trichoptera (less Hydropsychidae)

Percent of trichopterans that are not Hydropsychidae Decrease

% Collector-gatherer Percent of all individuals that are in the Collector-Gatherer Functional Feeding Group and feed on fine particulate organic matter Increase

% Scraper Percent of all individuals that are in the Scraper Functional Feeding Group and feed by scraping biofilms Decrease Hilsenhoff Biotic Index (HBI)

The HBI is calculated by multiplying the number of individuals of each taxa by its assigned tolerance value, summing these products, and dividing by the total number of individuals Increase No. Semivoltine Taxa (less semivoltine Coleoptera)

The number of semivoltine taxa (taxa requiring more than one year to complete their life cycle), excluding semivoltine Coleoptera which are often semi-aquatic Decrease TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

9 3.0 Results 3.1 Sampling Conditions The initial fall 2022 sampling event was conducted October 18-19, 2022, under mostly sunny skies and light winds. Air temperatures at a nearby weather station at Kemmerer Municipal Airport ranged from 32-68°F (0-20°C). Mean daily discharge taken from USGS gage

09223000 (Hams Fork Below Pole Creek, Near Frontier, WY) was 13.3 and 13.4 cubic feet per second (cfs), which is slightly lower than the long-term median of approximately 20 cfs during this time period (USGS 2023). No streamflow gage was present on North Fork Little Muddy Creek, but flows seemed rather typical based on visual assessment (stream within banks, emergent littoral vegetation wetted).

Although spring sampling was initially planned for May 2023, high flows on Hams Fork in May resulted in unsafe sampling conditions. Spring sampling was ultimately conducted June 13-14, 2023. Weather conditions during sampling were relatively cool for June, with air temperatures ranging between 46-65°F (8-18°C). Intermittent rain and episodic thunderstorms (at times heavy) occurred on the days of sampling. Due to above-average snowfall in the area the previous winter, as well as localized rain during sampling, both Hams Fork and North Fork Little Muddy Creek experienced relatively high flows during the spring 2023 sampling event. Mean daily discharge on the Hams Fork was 354 cfs and 348 cfs, slightly higher than the median for this date of 334 cfs (USGS 2023). Although no gage data is available for North Fork Little Muddy Creek, flows were elevated during the sampling period (out of bank at times) due to localized runoff from recent rains.

Summer sampling took place August 22-24, 2023, under seasonally typical weather conditions with air temperatures ranging between 48-78°F on the days of sampling. Intermittent rain and thunderstorms occurred on the days of sampling but did not substantially influence flow conditions. Mean daily discharge on the Hams Fork ranged from 27-32 cfs during the time of sampling, slightly higher than the median of approximately 20 cfs during this time period (USGS 2023). On the afternoon of August 22nd, the project team noted zero flow and isolated pools at North Fork Little Muddy Creek. Communication with Naughton Power Plant staff confirmed that plant discharge had been diverted into a reservoir while a pump was being replaced. The following day, on August 23rd, typical flow conditions were noted in North Fork Little Muddy Creek.

3.2 Habitat 3.2.1 Hams Fork 1 (HF 1)

HF 1 was the most upstream segment, located about 2.4 stream miles above the existing dam and intake structure (Figure 2). Stream width was approximately 45-70 feet (ft). Measured water depths ranged from 0.7-4.1 ft, and current velocities ranged from 0.2-2.5 feet per second (ft/s).

Habitat was mainly run, with lesser amounts of riffle, slackwater, backwater, and eddies.

Substrate was dominantly cobble, with interspersed gravel, sand, and silt. Water was generally clear and submerged aquatic vegetation (Myriophylum sp.) covered approximately 60% of the survey segment in all seasons. Woody debris was consistently present but not abundant, and TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

10 undercut banks provided additional cover. Surrounding terrestrial areas were used for livestock grazing and irrigated hay production. Although riparian vegetation was limited, livestock access to the stream resulted in trampling of streamside vegetation in places.

3.2.2 Hams Fork 2 (HF 2)

HF 2 was located approximately 1.2 stream miles downstream of HF 1 in a free-flowing section above the hydraulic influence of the downstream dam/intake structure at HF 3 (Figure 2).

Stream width was approximately 30-50 ft. Measured water depths ranged from 1.0-3.0 ft, and current velocities ranged from 0.6-3.1 ft/s. Habitat was mostly run and riffle, with scattered slackwaters, eddies, and pools. Substrate was predominantly cobble with lesser amounts of gravel, sand, and silt. Water was generally clear, and submerged aquatic vegetation (Myriophylum sp.) covered approximately 60% of the segment in all seasons. Woody debris was consistently present but not abundant. Undercut banks and overhanging terrestrial vegetation provided additional cover. Surrounding terrestrial areas were used for livestock grazing and irrigated hay production. Although riparian vegetation was limited, livestock access to the stream resulted in trampling of streamside vegetation in places.

3.2.3 Hams Fork 3 (HF 3)

This segment was located at the existing CWIS, which includes a small diversion dam and associated intake structure (Figure 2). Stream width was approximately 75 ft. Due to the pooling effects of the dam, this was the deepest and slowest segment, with measured water depths ranging from 2.3-8.0 ft, and current velocity ranging from 0.1-1.4 ft/s. Habitats were classified mainly as pool and run with scattered backwaters, slackwaters, and eddies. Substrates were predominantly silt with lesser amounts of cobble, gravel, and sand. The water was generally clear, but submerged aquatic vegetation was less common than in other segments due to the increased depths at this segment. Woody debris was present along banks and undercut banks and overhanging vegetation provided additional cover.

3.2.4 North Fork Little Muddy Creek 1 (NFLM 1)

NFLM 1 was located approximately 1.5 stream miles upstream of the Kemmerer Unit 1 site on an unnamed tributary carrying Naughton Power Plant effluent (Figure 3). The channel of North Fork Little Muddy Creek above the confluence of this tributary was generally dry. Wetted stream width was 3-9 ft. Habitat diversity was rather low with at least 90% of the segment being run habitat across seasons. Measured water depths ranged from 0.7-3.1 ft, and current velocities ranged from 0.1-1.4 ft/s. Substrate was 100% silt. Water was noted to be clear during base flow conditions but was extremely turbid following runoff from rainstorms. Submerged aquatic vegetation (Potamogeton foliosus) was prevalent in fall 2022, with reduced coverage in other seasons. No undercut banks or woody debris were noted. Surrounding terrestrial areas were used for livestock grazing (sheep and cattle were noted in the area).

3.2.5 North Fork Little Muddy Creek 2 (NFLM 2)

NFLM 2 was located on North Fork Little Muddy Creek near the midpoint of the Kemmerer Unit 1 site (Figure 3). Wetted stream width was 3-8 ft. Habitat diversity was rather low with 95% of the segment being run habitat across seasons. Measured water depths ranged from 0.5-2.3 ft, and current velocities ranged from 0.1-1.1 ft/s. Substrate was 100% silt and water was TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

11 typically turbid. Submerged aquatic vegetation was present, but limited, and portions of the channel were bordered in cattails (Typha sp.) resulting in overhanging and inundated vegetation covering much of the banks. No undercut banks or woody debris were noted. Surrounding terrestrial areas were used for livestock grazing (sheep and cattle were noted in the area).

3.2.6 North Fork Little Muddy Creek 3 (NFLM 3)

NFLM 3 was located approximately 0.4 stream mile downstream of the Kemmerer Unit 1 site on North Fork Little Muddy Creek (Figure 3). Stream width was 2-7 ft. Habitat diversity was rather low with at least 90% of the segment being classified as run habitat across seasons. Measured water depths ranged from 0.9-3.1 ft, and current velocities ranged from 0.3-1.4 ft/s. Substrate was 100% silt and water was generally turbid. Submerged aquatic vegetation was limited and the entire channel was bordered in cattails resulting in overhanging and inundated vegetation covering much of the banks. No undercut banks or woody debris were noted. Surrounding terrestrial areas were used for livestock grazing (sheep and cattle were noted in the area).

3.3 Water Quality Water quality showed both diel and seasonal variation (Table 3). At Hams Fork, observed water temperatures were lowest in fall 2022, ranging from 44.8 to 51.6 °F (7.1-10.9°C), intermediate in spring 2023, ranging from 54.9 to 56.8 °F (12.7-13.8°C), and highest in summer 2023, ranging from 64.2 to 67.3 °F (17.9-19.6°C). Water temperature differences between survey segments within a particular sampling event were likely influenced more by survey time of day than location, with measurements taken at segments sampled earlier in the day consistently being cooler than those taken later in the afternoon. Seasonal patterns in dissolved oxygen (DO) were also evident due to the inverse relationship between DO and water temperature, as expected.

Hams Fork DO was lowest in summer 2023 (7.35-7.90 mg/L), intermediate in spring 2023 (8.25-8.53 mg/L), and highest in fall 2022 (9.21-10.05 mg/L). Specific conductance at Hams Fork was lowest in spring 2023 (329-330 µS/cm), intermediate in summer 2023 (353-388 µS/cm), and highest in fall 2022 (441-455 µS/cm). This was likely influenced by flow conditions, as spring 2023 had the highest flows (thus more dilution) and fall 2022 had the lowest flows (potentially more concentration of soluble minerals, etc.). Lastly, pH ranged between 8.38 and 8.76 and no clear diel or seasonal patterns were evident based on the available data.

Seasonal patterns in water temperature and dissolved oxygen were less consistent at North Fork Little Muddy Creek (Table 3). Fall 2022 exhibited the warmest water temperature measured (23.3°C) during the coolest ambient air temperatures observed among seasons. However, similar to Hams Fork, DO levels were typically higher in fall 2022 (9.12-9.84 mg/L) compared to spring 2023 and summer 2023 (6.89-9.17 mg/L). No distinct diel or seasonal patterns in pH were noted, with values ranging from 8.01-9.29. Similarly, specific conductance ranged from 1498-4169 µS/cm and no clear patterns were evident based on the available data.

12 Table 3. Water quality measurements at three survey segments on Hams Fork (HF) and three survey segments in the North Fork Little Muddy Creek drainage (NFLM) during fall 2022, spring 2023, and summer 2023.

Segment Date Time Water Temperature (°C)

Dissolved Oxygen (mg/L)

Dissolved Oxygen

(% Saturation) pH Specific Conductance

(µS/cm)

HF 1 10/18/2022 10:54 7.1 9.21 76 8.47 444 HF 2 10/18/2022 12:36 8.6 10.05 86 8.60 441 HF 3 10/18/2022 14:40 10.9 9.23 82 8.73 455 NFLM 1 10/18/2022 15:26 23.3 9.84 114 8.99 1498 NFLM 2 10/18/2022 16:33 20.1 9.42 103 9.29 1525 NFLM 3 10/18/2022 15:58 17.7 9.12 95 8.40 1604 HF 1 06/13/2023 12:36 13.2 8.53 81 8.66 329 HF 2 06/13/2023 11:28 12.7 8.25 78 8.67 330 HF 3 06/13/2023 14:38 13.8 8.53 82 8.76 329 NFLM 1 06/13/2023 17:15 14.6 7.51 75 9.13 4169 NFLM 2 06/13/2023 16:35 17.4 7.42 78 8.51 2744 NFLM 3 06/13/2023 16:00 11.3 6.89 75 8.82 1580 HF 1 08/22/2023 12:15 18.6 7.35 79 8.51 354 HF 2 08/22/2023 10:56 17.9 7.44 78 8.38 353 HF 3 08/22/2023 14:20 19.6 7.90 86 8.50 388 NFLM 1 08/23/2023 9:00 16.8 7.86 82 8.01 2507 NFLM 2 08/23/2023 9:17 15.8 7.89 80 8.05 2513 NFLM 3 08/22/2023 15:25 23.2 9.17 109 8.37 2618 TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

13 3.4 Fishes 3.4.1 Hams Fork Across all segments and seasons, over 127 minutes of electrofishing time and 27 minnow trap-nights resulted in capture of 2,034 fishes representing three families, eight genera, and ten species (Table 4). Species captured most frequently were Redside Shiner Richardsonius balteatus (71% relative abundance), White Sucker Catostomus commersonii (14%), and Longnose Dace Rhinichthys cataractae (6%). Less common species included Rainbow Trout Oncorhynchus mykiss and Utah Chub Gila atraria, with only two and seven individuals collected, respectively.

Species richness was lowest at HF 3 (8 species), intermediate at HF 1 (9), and highest at HF 2 (10). In general, species composition was relatively similar between HF 1 and HF 2, with Redside Shiner, White Sucker, and Longnose Dace being the three most abundant species at each. Although Redside Shiner and White Sucker were similarly dominant at HF 3, Speckled Dace Rhinichthys osculus, Longnose Dace, and Mountain Sucker Catostomus platyrhynchus were absent or rare. In contrast, abundance of Fathead Minnows Pimephales promelas increased at HF 3, becoming the third most abundant species at this segment.

When analyzed by gear type, electrofishing accounted for approximately 90% of fishes collected (1,822 individuals) from Hams Fork whereas minnow traps accounted for 10% (212 individuals).

All species observed were captured via electrofishing, whereas minnow traps captured seven of ten species. Minnow traps did not capture any of the salmonids (Rainbow Trout, Mountain Whitefish Prosopium williamsoni, Brown Trout Salmo trutta). Overall electrofishing catch-per-unit-effort (CPUE) was 14.26 fish/minute (min) and decreased from upstream (20.88 fish/min at HF 1) to downstream (7.83 fish/min at HF 3) (Table 5). Minnow trap CPUE showed the opposite trend, increasing from upstream (5.22 fish/trap-night at HF 1) to downstream (12.44 fish/trap-night at HF 3), with the overall CPUE being 7.85 fish/trap-night (Table 6).

Among seasons, species richness, total fish abundance, electrofishing CPUE, and minnow trap CPUE all showed consistent trends, being highest in fall 2022, and lowest in spring 2023 (Table 7, Table 8).

Fish collected at Hams Fork ranged in size from a 12 mm (0.5 inch) young-of-year sucker (Catostomus sp.) to a 536 mm (21.1 inch) Brown Trout weighing 1,264 grams (2.8 lbs.). Length-frequency histograms for Brown Trout, Mountain Whitefish, and White Sucker provide evidence for multiple size/age classes within the population (Figure 4). Length-frequency histograms for other species with sufficient data can be found in Appendix B.

3.4.2 North Fork Little Muddy Creek Across all segments and seasons, over 145 minutes of electrofishing time and 27 trap-nights with minnow traps resulted in capture of 189 fishes representing two families, five genera, and seven species (Table 9). Species captured most frequently included Redside Shiner (41% relative abundance), Speckled Dace (28%), and Longnose Dace (13%). The least common species was Utah Chub, with only one individual collected at NFLM 2.

14 Table 4. Abundance (#) and percent relative abundance (%) of fishes collected from three segments on the Hams Fork (HF) via electrofishing and minnow trapping in 2022-2023.

Species Status HF 1 HF 2 HF 3 Overall Fathead Minnow (Pimephales promelas) non-native 10 1.00 4

0.59 15 4.32 29 1.43 Longnose Dace (Rhinichthys cataractae) non-native 36 3.59 93 13.62 1

0.29 130 6.39 Speckled Dace (Rhinichthys osculus) native 20 1.99 28 4.10 48 2.36 Redside Shiner (Richardsonius balteatus) non-native 733 73.01 489 71.60 224 64.55 1446 71.09 Utah Chub (Gila atraria) non-native 1

0.10 3

0.44 3

0.86 7

0.34 White Sucker (Catostomus commersonii) non-native 158 15.74 34 4.98 93 26.80 285 14.01 Mountain Sucker (Catostomus platyrhynchus) native 11 1.10 2

0.29 13 0.64 Young-of-Year Sucker (Catostomus sp.)

14 1.39 3

0.86 17 0.84 Rainbow Trout (Oncorhynchus mykiss) non-native 1

0.15 1

0.29 2

0.10 Mountain Whitefish (Prosopium williamsoni) native 11 1.10 7

1.02 1

0.29 19 0.93 Brown Trout (Salmo trutta) non-native 10 1.00 22 3.22 6

1.73 38 1.87 Species Richness 9

10 8

15 Table 5. Abundance (#) and catch-per-unit-effort (CPUE; fish/min) of fishes collected by electrofishing from three segments on the Hams Fork (HF) in 2022-2023.

Species Status HF 1 HF 2 HF 3 Overall CPUE CPUE CPUE CPUE Fathead Minnow (Pimephales promelas) non-native 10 0.22 1

0.02 10 0.33 21 0.16 Longnose Dace (Rhinichthys cataractae) non-native 20 0.44 81 1.56 1

0.03 102 0.80 Speckled Dace (Rhinichthys osculus) native 17 0.37 14 0.27 31 0.24 Redside Shiner (Richardsonius balteatus) non-native 705 15.38 477 9.18 122 4.07 1304 10.21 Utah Chub (Gila atraria) non-native 1

0.02 3

0.10 4

0.03 White Sucker (Catostomus commersonii) non-native 158 3.45 26 0.50 88 2.93 272 2.13 Mountain Sucker (Catostomus platyrhynchus) native 11 0.24 1

0.02 12 0.09 Young-of-Year Sucker (Catostomus sp.)

14 0.31 3

0.10 17 0.13 Rainbow Trout (Oncorhynchus mykiss) non-native 1

0.02 1

0.03 2

0.02 Mountain Whitefish (Prosopium williamsoni) native 11 0.24 7

0.13 1

0.03 19 0.15 Brown Trout (Salmo trutta) non-native 10 0.22 22 0.42 6

0.20 38 0.30 Overall 957 20.88 630 12.13 235 7.83 1822 14.26 Electrofishing Time (min) 45.83 51.95 30 127.78 Table 6. Abundance (#) and catch-per-unit-effort (CPUE; fish/trap-night) of fishes collected in minnow traps from three segments on the Hams Fork (HF) in 2022-2023.

Species Status HF 1 HF 2 HF 3 Overall CPUE CPUE CPUE CPUE Fathead Minnow (Pimephales promelas) non-native 3

0.33 5

0.56 8

0.30 Longnose Dace (Rhinichthys cataractae) non-native 16 1.78 12 1.33 28 1.04 Speckled Dace (Rhinichthys osculus) native 3

0.33 14 1.56 17 0.63 Redside Shiner (Richardsonius balteatus) non-native 28 3.11 12 1.33 102 11.33 142 5.26 Utah Chub (Gila atraria) non-native 3

0.33 3

0.11 White Sucker (Catostomus commersonii) non-native 8

0.89 5

0.56 13 0.48 Mountain Sucker (Catostomus platyrhynchus) native 1

0.11 1

0.04 Overall 47 5.22 53 5.89 112 12.44 212 7.85 Trap-nights 9

9 9

16 Table 7. Number (#) and percent relative abundance (%) of fishes captured from three survey segments on Hams Fork during fall (October 2022), spring (June 2023), and summer (August 2023).

Species Status Fall Spring Summer Hams Fork 1 Fathead Minnow (Pimephales promelas) non-native 10 1.5 Longnose Dace (Rhinichthys cataractae) non-native 5

0.7 1

5.3 30 9.8 Speckled Dace (Rhinichthys osculus) native 10 1.5 1

5.3 9

2.9 Redside Shiner (Richardsonius balteatus) non-native 526 77.6 15 78.9 192 62.5 Utah Chub (Gila atraria) non-native 1

5.3 White Sucker (Catostomus commersonii) non-native 119 17.6 1

5.3 38 12.4 Mountain Sucker (Catostomus platyrhynchus) native 11 3.6 Young-of-Year Sucker (Catostomus sp.)

14 4.6 Mountain Whitefish (Prosopium williamsoni) native 11 3.6 Brown Trout (Salmo trutta) non-native 8

1.2 2

0.7 Species Richness 6

5 7

Total Abundance 678 19 307 Hams Fork 2 Fathead Minnow (Pimephales promelas) non-native 1

0.3 3

4.3 Longnose Dace (Rhinichthys cataractae) non-native 27 7.9 19 27.1 47 17.2 Speckled Dace (Rhinichthys osculus) native 4

1.2 20 28.6 4

1.5 Redside Shiner (Richardsonius balteatus) non-native 278 81.8 16 22.9 195 71.4 Utah Chub (Gila atraria) non-native 2

2.9 1

0.4 White Sucker (Catostomus commersonii) non-native 10 2.9 9

12.9 15 5.5 Mountain Sucker (Catostomus platyrhynchus) native 1

1.4 1

0.4 Rainbow Trout (Oncorhynchus mykiss) non-native 1

0.4 Mountain Whitefish (Prosopium williamsoni) native 4

1.2 3

1.1 Brown Trout (Salmo trutta) non-native 16 4.7 6

2.2 Species Richness 7

7 9

Total Abundance 340 70 273 Hams Fork 3 Fathead Minnow (Pimephales promelas) non-native 15 6.6 Longnose Dace (Rhinichthys cataractae) non-native 1

0.8 Redside Shiner (Richardsonius balteatus) non-native 141 61.8 1

100.0 82 69.5 Utah Chub (Gila atraria) non-native 3

2.5 White Sucker (Catostomus commersonii) non-native 65 28.5 28 23.7 Young-of-Year Sucker (Catostomus sp.)

3 2.5 Rainbow Trout (Oncorhynchus mykiss) non-native 1

0.4 Mountain Whitefish (Prosopium williamsoni) native 1

0.4 Brown Trout (Salmo trutta) non-native 5

2.2 1

0.8 Species Richness 6

1 5

Total Abundance 228 1

17 Table 8. Species richness, total fish abundance, electrofishing CPUE (fish/min), and minnow trap CPUE (fish/trap-night) by season at Hams Fork.

Season/Date Species Richness Total Abundance Electrofishing CPUE Minnow Trap CPUE Fall (October 2022) 9 1246 24.0 13.4 Spring (June 2023) 7 90 1.6 3.6 Summer (August 2023) 8 698 14.2 6.6 Table 9. Abundance (#) and percent relative abundance (%) of fishes collected from three segments on the North Fork Little Muddy Creek drainage (NFLM) via electrofishing and minnow trapping in 2022-2023.

Species Status NFLM 1 NFLM 2 NFLM 3 Overall Fathead Minnow (Pimephales promelas) non-native 5

5.4 2

2.8 7

3.7 Longnose Dace (Rhinichthys cataractae) non-native 24 33.8 24 12.7 Speckled Dace (Rhinichthys osculus) native 21 84.0 29 31.2 3

4.2 53 28.0 Redside Shiner (Richardsonius balteatus) non-native 3

12.0 49 52.7 25 35.2 77 40.7 Utah Chub (Gila atraria) non-native 1

1.1 1

0.5 White Sucker (Catostomus commersonii) non-native 1

4.0 14 19.7 15 7.9 Mountain Sucker (Catostomus platyrhynchus) native 9

9.7 3

4.2 12 6.3 Species Richness 3

5 6

18 Figure 4. Length-frequency histograms for Brown Trout (top), Mountain Whitefish (middle), and White Sucker (bottom) captured from Hams Fork during all sampling events.

19 Species richness increased from upstream to downstream, being lowest at NFLM 1 (3 species) and highest at NFLM 3 (6 species). Similarly, abundance was lowest at NFLM 1 (25 individuals) and increased at the downstream segments (71-93 individuals) (Table 9).

When analyzed by gear type, minnow traps caught more fish (113 individuals, 60% of all fish captured) in North Fork Little Muddy Creek than backpack electrofishing (76 individuals, 40%),

but electrofishing caught more species (7 species) than minnow traps (5 species) (Table 10, Table 11). White Sucker and Utah Chub were not captured by minnow traps. Overall electrofishing CPUE was low (0.52 fish/min) and increased from upstream (0.07 fish/min at NFLM 1) to downstream (0.87 fish/min at NFLM 3). Overall minnow trap CPUE was 4.19 fish/trap-night and was lowest at NFLM 1 (2.44 fish/trap-night) and highest at NFLM 2 (7.11 fish/trap-night).

Among seasons, species richness and total fish abundance were highest in fall 2022 and lowest in spring 2023 (Table 12, Table 13). Electrofishing CPUE was highest in fall 2022 (1.2 fish/min) and similar in spring 2023 and summer 2023 (0.2 fish/min). Lastly, minnow trap CPUE was highest in summer 2023 (10.6 fish/trap-night) and lowest in spring 2023 (0.1 fish/trap-night).

Fish collected at North Fork Little Muddy Creek ranged in size from a 40 mm (1.6 inch) Fathead Minnow to a 275 mm (10.8 inch) White Sucker. Length-frequency histograms for species with sufficient data can be found in Appendix B.

3.5 Benthic Macroinvertebrates 3.5.1 Hams Fork In aggregate, a total of 4,972 individual macroinvertebrates from 70 unique taxa were identified from seasonal sampling (Table 14). Segment abundance and taxa richness overall were noticeably higher at HF 1 (1,779 individuals, 45 taxa) and HF 2 (2,474 individuals, 48 taxa) than HF 3 (719 individuals, 38 taxa). Dominant taxa across segments (relative abundance > 10%)

included mayflies of the Baetis genus (16.2%), caddisflies of the genus Hydropsyche (15.3%),

and midges of the family Chironomidae (10.9%). Abundant taxa at HF 1 included pea clams of the family Sphaeriidae (15.1%) and midges of the genus Simulium (13.9%). At HF 2, the two most abundant taxa were Baetis sp. (23.1%) and Hydropsyche sp. (21.3%). The top two taxa at HF 3 were annelids in the subclass Oligochaeta (31.0%) and chironomid midges (16.6%) (Table 14).

WSII metric values among segments showed number of Ephemeroptera, Trichoptera, and Plecoptera taxa were higher at HF 1 and HF 2 than HF 3 (Table 15). In contrast, HF 3 yielded higher percentages of non-insect and collector-gatherer taxa. Calculations of HBI showed similar results across segments and seasons. Variation in metric values between seasons was highest at HF 1 and HF 2, due to larger changes in percent Trichoptera and percent collector-gatherer taxa, respectively (Table 15).

Composite WSII scores reflect these differences in metric values, both seasonally and among segments. WSII scores were similar in the fall and summer for HF 1 (35.5-44.4) and HF 2 (35.3-44.3) (Figure 5). In spring, WSII was higher at HF 1 (41.7) than HF 2 (28.9), due mostly to large differences in percent Trichoptera score and percent Collector-gatherer score (Table 15). This TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

20 Table 10. Abundance (#) and catch-per-unit-effort (CPUE; fish/minute) of fishes captured by electrofishing at three segments on the North Fork Little Muddy Creek drainage (NFLM) in 2022-2023.

Species Status NFLM 1 NFLM 2 NFLM 3 Overall CPUE CPUE CPUE CPUE Fathead Minnow (Pimephales promelas) non-native 4

0.08 2

0.04 6

0.04 Longnose Dace (Rhinichthys cataractae) non-native 10 0.20 10 0.07 Speckled Dace (Rhinichthys osculus) native 2

0.04 14 0.28 16 0.11 Redside Shiner (Richardsonius balteatus) non-native 8

0.16 15 0.30 23 0.16 Utah Chub (Gila atraria) non-native 1

0.02 1

0.01 White Sucker (Catostomus commersonii) non-native 1

0.02 14 0.28 15 0.10 Mountain Sucker (Catostomus platyrhynchus) native 2

0.04 3

0.06 5

0.03 Overall 3

0.07 29 0.59 44 0.87 76 0.52 Electrofishing Time (min) 45.18 49.45 50.48 145.11 Table 11. Abundance (#) and catch-per-unit-effort (CPUE; fish/trap-night) of fishes captured in minnow traps at three segments on the North Fork Little Muddy Creek drainage (NFLM) in 2022-2023.

Species Status NFLM 1 NFLM 2 NFLM 3 Overall CPUE CPUE CPUE CPUE Fathead Minnow (Pimephales promelas) non-native 1

0.02 1

0.01 Longnose Dace (Rhinichthys cataractae) non-native 14 0.52 14 0.12 Speckled Dace (Rhinichthys osculus) native 19 0.86 15 0.23 3

0.11 37 0.33 Redside Shiner (Richardsonius balteatus) non-native 3

0.14 41 0.64 10 0.37 54 0.48 Mountain Sucker (Catostomus platyrhynchus) native 7

0.11 7

0.06 Overall 22 2.44 64 7.11 27 3.00 113 4.19 Trap-nights 9

9 9

21 Table 12. Number (#) and percent relative abundance (%) of fishes captured from North Fork Little Muddy Creek during fall (October 2022), spring (June 2023), and summer (August 2023).

Species Status Fall Spring Summer North Fork Little Muddy Creek 1 Speckled Dace (Rhinichthys osculus) native 18 94.7 3

60.0 Redside Shiner (Richardsonius balteatus) non-native 1

5.3 2

40.0 White Sucker (Catostomus commersonii) non-native 1

100.0 Species Richness 2

1 2

Total Abundance 19 1

5 North Fork Little Muddy Creek 2 Fathead Minnow (Pimephales promelas) non-native 1

1.2 1

100.0 3

27.3 Speckled Dace (Rhinichthys osculus) native 29 35.8 Redside Shiner (Richardsonius balteatus) non-native 42 51.9 7

63.6 Mountain Sucker (Catostomus platyrhynchus) native 9

11.1 Utah Chub (Gila atraria) non-native 1

9.1 Species Richness 4

1 3

Total Abundance 81 1

11 North Fork Little Muddy Creek 3 Fathead Minnow (Pimephales promelas) non-native 2

3.8 Longnose Dace (Rhinichthys cataractae) non-native 15 28.3 9

81.8 Speckled Dace (Rhinichthys osculus) native 2

3.8 1

14.3 Redside Shiner (Richardsonius balteatus) non-native 23 43.4 2

18.2 White Sucker (Catostomus commersonii) non-native 8

15.1 6

85.7 Mountain Sucker (Catostomus platyrhynchus) native 3

5.7 Species Richness 6

2 2

Total Abundance 53 7

11 Table 13. Species richness, total fish abundance, electrofishing CPUE (fish/min), and minnow trap CPUE (fish/trap-night) by season at North Fork Little Muddy Creek.

Season/Date Species Richness Total Abundance Electrofishing CPUE Minnow Trap CPUE Fall (October 2022) 6 153 1.2 1.9 Spring (June 2023) 3 9

22 Table 14. Number of benthic macroinvertebrates by lowest taxonomic unit (LTU) collected from each survey segment in Hams Fork during fall 2022, spring 2023, and summer 2023 sampling events.

Phylum Order Family Genus/Species/LTU HF 1 HF 2 HF 3 Overall #

Overall %

Annelida Oligochaeta 17 44 223 284 5.7 Hirudinea 0

0 1

1

<0.1 Arthropoda Coleoptera Dytiscidae Acilius abbreviatus 0

1 2

3 0.1 Agabus sp.

0 1

1 2

<0.1 Colymbetes incognitus 0

0 2

2

<0.1 Laccophilus maculosus 0

1 1

2

<0.1 Liodessus obscurellus 1

2 0

3 0.1 Rhantus binotatus 1

1 1

3 0.1 Rhantus sericans 1

0 0

1

<0.1 Elmidae Dubiraphia sp.

7 20 5

32 0.6 Optioservus sp.

197 274 0

471 9.5 Gyrinidae Gyrinus bifarius 1

1 0

2

<0.1 Gyrinus sp. 2 7

5 13 25 0.5 Gyrinus sp. 3 1

2 22 25 0.5 Haliplidae Haliplus sp.

1 0

0 1

<0.1 Hydraenidae Ochthebius lineatus 0

1 0

1

<0.1 Hydrophilidae Enochrus sp.

0 1

<0.1 Hydrobius fuscipes 1

0 0

1

<0.1 Tropisternus lateralis 1

0 0

1

<0.1 Copepoda 2

0 1

3 0.1 Diptera Athericidae Atherix sp.

35 10 0

45 0.9 Ceratopogonidae Bezzia complex 0

1 1

2

<0.1 Chironomidae Chironomidae 175 249 119 543 10.9 Limoniidae Hexatoma sp.

0 2

<0.1 Symplecta sp.

0 1

<0.1 Simuliidae Simulium sp.

247 110 0

357 7.2 Tabanidae Tabanus sp.

0 0

2 2

<0.1 Tipulidae Tipula sp.

3 0

0 3

0.1 Ephemeroptera Baetidae Baetis sp.

231 571 5

807 16.2 Callibaetis sp.

34 0

68 102 2.1 Caenidae Caenidae 0

1 0

1

<0.1 Ephemerellidae Ephemerella sp.

0 39 0

39 0.8 Ephemeridae Ephemera sp.

6 11 0

17 0.3 Heptageniidae Stenonema sp.

23 22 1

46 0.9 Leptohyphidae Tricorythodes sp.

52 60 0

112 2.3 Leptophlebiidae Leptophlebia sp.

6 7

1 14 0.3 Neoleptophlebia sp.

1 0

0 1

<0.1 Paraleptophlebia sp.

22 46 1

23 Table 14 continued.

Phylum Order Family Genus/Species/LTU HF 1 HF 2 HF 3 Overall #

Overall %

Hemiptera Corixidae Callicorixa sp.

0 1

4 5

0.1 Cenocorixa bifida 0

0 14 14 0.3 Corixini 0

0 17 17 0.3 Hesperocorixa laevigata 0

0 4

4 0.1 Sigara sp.

4 6

22 32 0.6 Notonectidae Notonecta spinosa 0

0 9

9 0.2 Lepidoptera Crambidae Petrophila sp.

1 17 0

18 0.4 Lepidoptera sp.

2 3

0 5

0.1 Noctuoidea 0

0 1

1

<0.1 Megaloptera Sialidae Sialis sp.

1 2

2 5

0.1 Odonata Aeshnidae Anax junius 0

0 13 13 0.3 Calopterygidae Calopteryx sp.

0 1

<0.1 Coenagrionidae Enallagma sp.

14 11 10 35 0.7 Gomphidae Ophiogomphus sp.

2 0

0 2

<0.1 Plecoptera Perlodidae Cultus sp.

4 11 0

15 0.3 Perlodidae 15 17 0

32 0.6 Trichoptera Brachycentridae Brachycentrus occidentalis 91 39 0

130 2.6 Helicopsychidae Helicopsyche sp.

1 0

0 1

<0.1 Hydropsychidae Cheumatopshyche sp.

0 19 0

19 0.4 Hydropsyche sp.

231 528 1

760 15.3 Leptoceridae Oecetis disjunctus 7

2 0

9 0.2 Limnephilidae Limnephilidae 1

3 0

4 0.1 Amphipoda Hyalellidae Hyallela sp.

33 104 28 165 3.3 Decapoda Cambaridae Faxonius sp.

15 90 99 204 4.1 Mollusca Sphaeriida Sphaeriidae Sphaeriidae 268 79 6

353 7.1 Basommatophora Ancylidae Ferrissia sp.

2 33 2

37 0.7 Lymnaeidae Lymnaea sp.

0 0

2 2

<0.1 Stagnicola sp.

0 0

2 2

<0.1 Physidae Physella sp.

9 19 12 40 0.8 Planorbidae Planorbidae 2

0 1

3 0.1 Nematoda Nematoda 0

1 0

1

<0.1 Platyhelminthes Tricladida Dugesiidae Dugesia sp.

3 4

0 7

24 Table 15. Metric values and scores for calculating the Wyoming Stream Integrity Index (Wyoming Basin) at three segments in the Hams Fork during fall 2022, spring 2023, and summer 2023 sampling events. Composite WSII scores for each segment/season are in bold text.

Fall Spring Summer Metric Value Score Value Score Value Score Hams Fork 1 No. Ephemeroptera Taxa 7

77.8 2

22.2 4

44.4 No. Trichoptera Taxa 3

33.3 3

33.3 No. Plecoptera Taxa 1

16.7 1

16.7 0

0.0

% Non-insect 10.2 86.5 17.1 73.7 23.6 63.5

% Plecoptera 2.2 9.8 5.7 25.6 0.0 0.0

% Trichoptera (less Hydropsychidae) (% within Trichoptera) 15.2 15.2 90.9 90.9 33.3 33.3

% Collector-gatherer 49.7 61.2 58.6 49.4 25.6 93.0

% Scraper 20.8 53.9 2.9 7.4 7.9 20.5 HBI 5.1 49.8 4.6 57.5 5.3 47.0 No. Semivoltine Taxa (less semivoltine Coleoptera) 2 40.0 2

40.0 1

20.0 Composite WSII Score 44.4 41.7 35.5 Hams Fork 2 No. Ephemeroptera Taxa 6

66.7 5

55.6 4

44.4 No. Trichoptera Taxa 5

55.6 2

22.2 3

33.3 No. Plecoptera Taxa 0

0.0 1

16.7 1

16.7

% Non-insect 6.3 91.9 8.2 87.8 19.7 69.6

% Plecoptera 0.0 0.0 2.3 10.3 0.3 1.2

% Trichoptera (less Hydropsychidae) (% within Trichoptera) 12.1 12.1 3.6 3.6 6.3 6.3

% Collector-gatherer 39.9 74.1 86.2 13.0 43.8 69.0

% Scraper 22.6 58.4 0.6 1.6 15.0 38.8 HBI 4.2 64.1 4.6 58.0 4.9 53.6 No. Semivoltine Taxa (less semivoltine Coleoptera) 1 20.0 1

20.0 1

20.0 Composite WSII Score 44.3 28.9 35.3 Hams Fork 3 No. Ephemeroptera Taxa 2

22.2 3

33.3 0

0.0 No. Trichoptera Taxa 0

0.0 1

11.1 0

0.0 No. Plecoptera Taxa 0

0.0 0

0.0

% Non-insect 26.6 64.3 65.0 0.0 64.4 0.0

% Plecoptera 0.0 0.0 0.0 0.0 0.0 0.0

% Trichoptera (less Hydropsychidae) (% within Trichoptera) 0.0 0.0 0.0 0.0 0.0 0.0

% Collector-gatherer 79.9 21.2 95.0 1.3 72.3 31.3

% Scraper 2.1 5.4 0.0 0.0 3.6 9.3 HBI 6.8 23.8 5.1 50.3 5.9 38.3 No. Semivoltine Taxa (less semivoltine Coleoptera) 0 0.0 0

0.0 1

25 resulted in a partial/non-support aquatic life use status at HF 2 in spring, whereas all other events at HF 1 and HF 2 had an Indeterminate aquatic life use. WSII scores were much lower at HF 3 (9.6-13.7) and all seasons yielded aquatic life use statuses of partial/non-support (Figure 5). In addition to having high percentages of non-insect and collector gatherer taxa, HF 3 also had more frequent metric scores of zero, particularly in spring and summer seasons (Table 15).

Figure 5. Composite Wyoming Stream Integrity Index scores (Wyoming basin; mean +/- 95%

confidence intervals) and associated aquatic life use status thresholds at three segments on Hams Fork during fall 2022, spring 2023, and summer 2023 sampling events.

3.5.2 North Fork Little Muddy Creek In aggregate, a total of 1,651 individual macroinvertebrates from 36 unique taxa were identified from seasonal sampling (Table 16). Segment abundance and taxa richness overall were higher at NFLM 1 (629 individuals, 22 taxa) and NFLM 2 (680 individuals, 25 taxa) than NFLM 3 (342 individuals, 15 taxa). Dominant taxa across segments included midges of the family Chironomidae (23.1%), mayflies of the Callibaetis genus (15.5%), amphipods of the genus Hyallela (12.4%), crayfish of the genus Faxonius (11.2%), and snails of the genus Physella (10.3%). Insects mostly dominated assemblages at NFLM 1 and NFLM 2, which included chironomids (22.3-32.1%) and Callibaetis (17.2-20.3%). In contrast, NFLM 3 assemblages had higher abundances of non-insect taxa that included Hyallela (36.5%) and Faxonius (23.7%),

though Physella (20.7%) was also relatively abundant at NFLM 1 (Table 16).

26 Table 16. Number of benthic macroinvertebrates by lowest taxonomic unit (LTU) collected from each survey segment in the North Fork Little Muddy Creek drainage during fall 2022, spring 2023, and summer 2023 sampling events.

Phylum Order Family Genus/Species/LTU NFLM 1 NFLM 2 NFLM 3 Overall #

Overall %

Annelida Oligochaeta Oligochaeta 15 28 68 111 6.7 Arthropoda Anisoptera Libellulidae Sympetrum sp.

1 0

0 1

0.1 Coleoptera Dytiscidae Dytiscus marginicollis 0

1 0

1 0.1 Hydroporinae sp.

1 0

0 1

0.1 Laccophilus maculosus 4

28 11 43 2.6 Liodessus obscurellus 2

1 1

4 0.2 Elmidae Dubiraphia sp.

0 0

1 1

0.1 Gyrinidae Gyrinus bifarius 2

0 0

2 0.1 Gyrinus sp. 2 1

0 0

1 0.1 Haliplidae Haliplus sp.

1 0

0 1

0.1 Helophoridae Helophorus sp.

2 1

0 3

0.2 Hydraenidae Ochthebius sp.

0 1

0.1 Copepoda 0

1 0

1 0.1 Diptera Ceratopogonidae Bezzia complex 0

1 4

5 0.3 Culicoides sp.

0 0

1 1

0.1 Chironomidae Chironomidae 140 218 24 382 23.1 Limoniidae Symplecta sp.

0 1

0.1 Muscidae Limnophora sp.

0 1

0.1 Simuliidae Simulium sp.

0 42 0

42 2.5 Stratiomyidae Nemotelus sp.

1 0

0 1

0.1 Tabanidae Tabanus sp.

1 0

0 1

0.1 Brachycera 0

1 0

1 0.1 Ephemeroptera Baetidae Callibaetis sp.

108 138 10 256 15.5 Caenidae Caenis sp.

19 1

0 20 1.2 Hemiptera Corixidae Corisella decolor 0

10 0

10 0.6 Hesperocorixa laevigata 0

1 0

1 0.1 Sigara sp.

2 34 3

39 2.4 Notonectidae Notonecta kirbyi 0

1 0

1 0.1 Notonecta spinosa 0

0 1

1 0.1 Odonata Aeshnidae Anax junius 6

0 0

6 0.4 Coenagrionidae Enallagma sp.

64 21 3

88 5.3 Trichoptera Hydroptilidae Hydroptila sp.

32 2

0 34 2.1 Amphipoda Hyalellidae Hyallela sp.

58 21 125 204 12.4 Decapoda Cambaridae Faxonius sp.

29 75 81 185 11.2 Ostracoda 10 16 4

30 1.8 Mollusca Basommatophora Physidae Physella sp.

130 35 5

27 WSII composite scores were mostly similar across segments, excepting NFLM 1 and NFLM 2 which had relatively high scores in fall (Table 17, Figure 6). Percent non-insect taxa were substantially higher at NFLM 3, which also yielded no Trichoptera taxa during any event.

Variation in metric values between seasons at NFLM 1 and NFLM 2 was mostly due to seasonal changes in the trichopteran community (Table 17). Most events yielded aquatic life use statuses of partial/non-support, with composite WSII scores ranging from 4.8 to 28.0. NFLM 1 in fall was the only sampling event that produced an aquatic life use status higher than partial/non-support (35.6, indeterminate), as shown in Table 17 and Figure 6.

4.0 Discussion and Conclusions Data presented in previous sections characterize fish and benthic macroinvertebrate communities in two streams potentially impacted by construction and operation of Kemmerer Unit 1 and associated infrastructure. The information in this report is based on seasonal surveys conducted in October 2022 (fall), June 2023 (spring), and August 2023 (summer). Within Hams Fork, these surveys documented 10 fish species ranging from native cold-water salmonids such as Mountain Whitefish to non-native generalist species such as Fathead Minnow. Of the 10 species collected, only the Speckled Dace, Mountain Sucker, and Mountain Whitefish are originally native to the upper Green River basin (Baxter and Stone 1995; WGFD 2017). Data provided by Wyoming Game and Fish Department (WGFD) show five fish collections within the mainstem Hams Fork in this general area (Kemmerer City Reservoir downstream to Kemmerer, Wyoming) from 2002 to 2004 (J. Lockwood, WGFD, e-mail to P.R. Moore, May 12, 2022). Collectively, these surveys documented the same 10 species (disregarding rare sucker hybrids and unknowns).

Both fish and benthic macroinvertebrate community composition were relatively similar between the two upstream segments (HF 1 and HF 2) which were comprised mainly of run and riffle habitats with cobble and gravel substrates. In these segments, Redside Shiner, White Sucker, and Longnose Dace were the numerically dominant fish species, and mayflies (Ephemeroptera),

stoneflies (Plecoptera), and caddisflies (Trichoptera), indicators of good water quality, were common in the macroinvertebrate community. In contrast, HF 3 was deeper, with slower velocities and siltier substrates due to impoundment by a small dam/intake structure. Here, certain small-bodied cyprinids adapted to shallow swift waters (i.e., Longnose Dace and Speckled Dace) were less abundant or absent whereas non-native Fathead Minnows increased in abundance. Fathead Minnow are typically found in quiet ponds, pools, and backwaters within their native range east of the Rocky Mountains (Minckley 1959; Deacon 1961). Similarly, benthic macroinvertebrate sampling documented decreased abundance or absence of mayflies, stoneflies, and caddisflies at HF 3 and increased dominance of worms (Oligochaeta) and midges (Chironomidae).

Both total fish abundance and electrofishing CPUE at Hams Fork decreased from upstream (HF

1) to downstream (HF 3). Reduced abundance and catch rates at HF 3 were likely due to habitat differences which limited the abundance of certain small-bodied cyprinids, as noted above.

Interestingly, minnow trap CPUE exhibited an opposite trend of electrofishing CPUE, being highest at HF 3 and lower at upstream segments. This suggests that baited minnow traps may be TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

28 Table 17. Metric values and scores for calculating the Wyoming Stream Integrity Index (Wyoming Basin) at three segments in the North Fork Little Muddy Creek drainage during fall 2022, spring 2023, and summer 2023 sampling events. Composite WSII scores for each segment/season are in bold text.

Fall Spring Summer Metric Value Score Value Score Value Score North Fork Little Muddy Creek 1 No. Ephemeroptera Taxa 2

22.2 1

11.1 0

0.0 No. Trichoptera Taxa 1

11.1 0

0.0 0

0.0 No. Plecoptera Taxa 0

0.0 0

0.0

% Non-insect 28.3 62.0 44.8 30.1 75.0 0.0

% Plecoptera 0.0 0.0 0.0 0.0 0.0 0.0

% Trichoptera (less Hydropsychidae) (% within Trichoptera) 100.0 100.0 0.0 0.0 0.0 0.0

% Collector-gatherer 55.8 53.1 82.8 17.5 75.0 27.7

% Scraper 29.6 76.6 0.0 0.0 0.0 0.0 HBI 7.6 11.5 6.0 35.9 6.6 27.0 No. Semivoltine Taxa (less semivoltine Coleoptera) 1 20.0 0

0.0 1

20.0 Composite WSII Score 35.6 9.5 7.5 North Fork Little Muddy Creek 2 No. Ephemeroptera Taxa 2

22.2 0

0.0 0

0.0 No. Trichoptera Taxa 1

11.1 0

0.0 0

0.0 No. Plecoptera Taxa 0

0.0 0

0.0

% Non-insect 15.0 80.0 63.2 1.3 58.5 8.7

% Plecoptera 0.0 0.0 0.0 0.0 0.0 0.0

% Trichoptera (less Hydropsychidae) (% within Trichoptera) 100.0 100.0 0.0 0.0 0.0 0.0

% Collector-gatherer 74.2 28.8 68.4 36.4 58.5 49.6

% Scraper 7.3 19.0 0.0 0.0 0.0 0.0 HBI 7.1 18.9 5.3 46.4 5.3 47.1 No. Semivoltine Taxa (less semivoltine Coleoptera) 0 0.0 0

0.0 0

0.0 Composite WSII Score 28.0 8.4 10.5 North Fork Little Muddy Creek 3 No. Ephemeroptera Taxa 1

11.1 0

0.0 1

11.1 No. Trichoptera Taxa 0

0.0 0

0.0 No. Plecoptera Taxa 0

0.0 0

0.0

% Non-insect 58.9 20.5 100.0 0.0 89.8 0.0

% Plecoptera 0.0 0.0 0.0 0.0 0.0 0.0

% Trichoptera (less Hydropsychidae) (% within Trichoptera) 0.0 0.0 0.0 0.0 0.0 0.0

% Collector-gatherer 88.4 10.1 87.5 11.2 91.7 5.7

% Scraper 2.3 6.0 12.5 32.4 0.5 1.3 HBI 5.7 40.0 8.0 4.7 6.2 33.3 No. Semivoltine Taxa (less semivoltine Coleoptera) 0 0.0 0

0.0 0

29 more effective in the slower moving waters at HF 3 compared to the generally swifter upstream segments.

Figure 6. Composite Wyoming Stream Integrity Index scores (Wyoming basin; mean +/- 95%

confidence intervals) and associated aquatic life use status thresholds at three segments in the North Fork Little Muddy Creek drainage during fall 2022, spring 2023, and summer 2023 sampling events.

Among seasons, species richness, abundance, and CPUE of both fish sampling methods at Hams Fork were lowest in spring 2023, due to high flow conditions which limited sampling efficiency.

The same metrics were all highest in fall 2022, perhaps because many young-of-year fishes grow to catchable size by October. Alternatively, differences observed between fall 2022 and summer 2023 could have been influenced by inter-annual variability in recruitment or a variety of other factors. Similarly, composite WSII scores were generally highest in fall 2022 and lower in spring 2023 and summer 2023. Differences in macroinvertebrate community composition between seasons may be influenced by intra-annual ontogenetic patterns in life cycles of resident insect taxa (Johnson et al. 2012), among other factors.

Within the North Fork Little Muddy Creek drainage, seasonal surveys at the three survey segments documented seven fish species, of which only the Speckled Dace and Mountain Sucker are originally native to the drainage (Baxter and Stone 1995; WGFD 2017). Data provided by TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

30 WGFD show five fish collections within this general reach of North Fork Little Muddy Creek (from Naughton Power Plant to confluence with Little Muddy Creek) from 2004 to 2018 (J.

Lockwood, WGFD, e-mail to P.R. Moore, May 12, 2022). Collectively, these surveys also document seven species, but two of the collections document Roundtail Chub Gila robusta, which was not observed in this study. On the other hand, none of the WGFD collections list Longnose Dace, which was observed in this study. Roundtail Chub was rare in WGFD collections (0.4% relative abundance; 2,844 fishes collected), and the species absence in this study (189 fishes collected) may just reflect inherent sampling variability associated with a lower sample size. Longnose Dace have become established in the Hams Fork drainage, presumably introduced by bait fishermen (Baxter and Stone 1995) and were documented in the mainstem Hams Fork during this study. The reason for its absence from previous North Fork Little Muddy Creek collections is unclear. It should be noted that Longnose Dace and Speckled Dace are closely related species that are known to hybridize in areas where Longnose Dace have been introduced (Sigler and Miller 1963).

Total abundance and richness of fishes was lowest at NFLM 1 and higher at downstream segments, but an opposite trend was observed in macroinvertebrate richness and abundance, being lowest at the downstream segment (NFLM 3). This may reflect the influence of fish predation on macroinvertebrate communities in a small stream environment. However, a variety of other potential mechanisms may be influencing fish and macroinvertebrate communities within this effluent-dominated system and additional data are needed under varying hydrologic conditions to better understand exact mechanisms behind the spatial and temporal patterns observed.

Overall electrofishing CPUE was low in the North Fork Little Muddy Creek drainage, and in contrast to Hams Fork, minnow traps collected more fish here than electrofishing. This demonstrates the effectiveness of baited minnow traps in such small stream environments.

Additionally, it should be noted that backpack electrofishing efficiency was often limited due to turbidity.

Among seasons in North Fork Little Muddy Creek, species richness, total fish abundance, and catch rates from both fish sampling methods were low in spring 2023. Although flow in North Fork Little Muddy Creek did not fluctuate as drastically as in Hams Fork, rainstorms during spring 2023 sampling did result in high muddy water at some survey segments, which may have influenced catch rates. As observed at Hams Fork, macroinvertebrate composite WSII scores were generally highest in fall 2022 and lower in spring 2023 and summer 2023. Seasonal differences in macroinvertebrate communities may be influenced by life cycle timing of resident insect fauna and potential interactions with abiotic disturbances (Johnson et al. 2012, Ofogh et al.

2023). For example, zero flow conditions observed on August 22, 2023 may have influenced macroinvertebrate community composition, as most invertebrates observed in summer 2023 can burrow into the substrate or have adult life stages that can fly (Coleoptera, Hemiptera). Its unknown how often zero flow conditions occur in this portion of North Fork Little Muddy Creek.

31 Results of this study in context with previously available information from WGFD provide useful baseline data on aquatic habitat, fish communities, and benthic macroinvertebrate communities that will aid in assessing potential impacts from Project construction and operation.

Continued monitoring of the established survey segments is recommended to allow evaluation of potential temporal changes in aquatic communities as Kemmerer Unit 1 construction and operation progress. Based on results from this study, and to allow comparisons to existing data, monitoring is recommended annually in August and/or October, as annual peaks in discharge associated with spring snow melt in this region result in decreased fish capture efficiencies in spring and early summer months. Additionally, when seasonal variation in macroinvertebrate communities exist, indices generated during base flow periods of summer and fall have shown the best bioassessment performance (Ofogh et al. 2023).

5.0 References Barbour, M.T., J. Gerritsen, B.D. Snyder, and J.B. Stribling. 1999. Rapid Bioassessment Protocols for use in Streams and Wadeable Rivers: Periphyton, Benthic Macroinvertebrates and Fish, Second Edition. EPA 841-B-99-002. U.S. Environmental Protection Agency, Office of Water, Washington, D.C.

Baxter, G.T., and M.D. Stone. 1995. Fishes of Wyoming. Wyoming Game and Fish Department.

U.S.A.

Deacon, J.E. 1961. Fish populations, following a drought, in the Neosho and Marais des Cygnes Rivers of Kansas. Mus. Nat. Hist. Univ. Kans. 13(9):359-427.

Hargett, E.G., and J.R. ZumBerge. 2006. Redevelopment of the Wyoming Stream Integrity Index (WSII) for assessing the biological condition of wadeable streams in Wyoming.

Wyoming Department of Environmental Quality, Water Quality Division, Cheyenne, WY.

Hawkins, C.P., J.L. Kershner, P.A. Bisson, M.D. Bryant, L.M. Decker, S.V. Gregory, D.A.McCullough, C.K. Overton, G.H. Reeves, R.J. Steedman, and M.K. Young. 1993. A hierarchical approach to classifying stream habitat features. Fisheries 18(6): 3-12.

Hilsenhoff, W.L. 1987. An improved biotic index of organic stream pollution. Great Lakes Entomologist 20:31-39.

Johnson, R.C., M.M. Carreiro, H. Jin, and J.D. Jack. 2012. Within-year temporal variation and life-cycle seasonality affect stream macroinvertebrate community structure and biotic metrics. Ecological Indicators 13(1): 206-214.

Minckley, W. L. 1959. Fishes of the Big Blue River Basin, Kansas. Mus. Nat. Hist. Univ. Kans.

11(7):401-422.

Ofogh, A.R., E.E. Dorche, S. Birk, and A. Bruder. 2023. Effect of seasonal variability on the development and application of a novel Multimetric Index based on benthic TP-LIC-LET-0362 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved

32 macroinvertebrate communities - A case study from streams in the Karun river basin (Iran). Ecological Indicators 146 (2023) 109843.

Sigler, W.F., and R.R. Miller. 1963. Fishes of Utah. Utah Department of Fish and Game, Salt Lake City, UT.

USGS (U.S. Geological Survey). 2023. USGS 09223000 Hams Fork Below Pole Creek, Near Frontier, WY. https://waterdata.usgs.gov/nwis/inventory/?site_no=09223000.

Wisseman, R.W. 2001. Salomon Web: Community Based Monitoring for Biological Integrity of Streams, Taxa Information. https://www.cbr.washington.edu/salmonweb/taxon/ [accessed on 1/6/2022].

WGFD (Wyoming Game and Fish Department). 2017. Green River Basin. In Wyoming State Wildlife Action Plan - 2017. Available on line at:

https://wgfd.wyo.gov/WGFD/media/content/PDF/Habitat/SWAP/Aquatic%20Basins/Gre en-River-Basin.pdf.

33 Appendix A. Photos Figure A1. Segment HF 1 during August 2022 reconnaissance.

34 Figure A2. Segment HF 2 during August 2022 reconnaissance.

35 Figure A3. Segment HF 3 during August 2022 reconnaissance event showing dam (lower photo) and upstream pool (upper photo).

36 Figure A4. Segment NFLM 1 during August 2022 reconnaissance.

37 Figure A5. Segment NFLM 2 during August 2022 reconnaissance.

38 Figure A6. Segment NFLM 3 during August 2022 reconnaissance.

39 Figure A7. BIO-WEST and Tetra Tech personnel barge electrofishing at segment HF 2 in fall 2022.

40 Figure A8. Backpack electrofishing at NFLM 2 during spring 2023.

41 Figure A9. Minnow trap set at HF 2 in fall 2022.

42 Figure A10. Macroinvertebrate sampling with D-net at HF 1 in fall 2022.

43 Figure A11. Longnose Dace (Rhinichthys cataractae) captured from Hams Fork.

44 Figure A12. Mountain Sucker (Catostomus platyrhynchus) captured from North Fork Little Muddy Creek.

45 Figure A13. Redside Shiner (Richardsonius balteatus) captured from North Fork Little Muddy Creek.

46 Figure A14. Speckled Dace (Rhinichthys osculus) captured from Hams Fork.

47 Figure A15. Brown Trout (Salmo trutta) captured from Hams Fork.

48 Figure A16. Mountain Whitefish (Prosopium williamsoni) captured from Hams Fork.

49 Figure A17. Rainbow Trout (Oncorhynchus mykiss) captured from Hams Fork.

50 Figure A18. White Sucker (Catostomus commersonii) captured from Hams Fork.

51 Figure A19. Fathead Minnow (Pimephales promelas) captured from North Fork Little Muddy Creek.

52 Figure A20. Mountain Sucker (Catostomus platyrhynchus) captured from Hams Fork.

53 Figure A21. Utah Chub (Gila atraria) captured from North Fork Little Muddy Creek.

54 Appendix B. Length-frequency Histograms Figure B1. Length-frequency histogram for Longnose Dace captured from Hams Fork (top) and North Fork Little Muddy Creek (bottom).

55 Figure B2. Length-frequency histograms for Speckled Dace captured from Hams Fork (top) and North Fork Little Muddy Creek (bottom).

56 Figure B3. Length-frequency histograms for Redside Shiner captured from Hams Fork (top) and North Fork Little Muddy Creek (bottom).

57 Figure B4. Length-frequency histograms for White Sucker captured from Hams Fork (top) and North Fork Little Muddy Creek (bottom).

58 Figure B5. Length-frequency histograms for Mountain Sucker captured from Hams Fork (top) and North Fork Little Muddy Creek (bottom).

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